gnunet-android

ssl.h (326250B)

---

 // Copyright 1995-2016 The OpenSSL Project Authors. All Rights Reserved.
 // Copyright (c) 2002, Oracle and/or its affiliates. All rights reserved.
 // Copyright 2005 Nokia. All rights reserved.
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
 // You may obtain a copy of the License at
 //
 //     https://www.apache.org/licenses/LICENSE-2.0
 //
 // Unless required by applicable law or agreed to in writing, software
 // distributed under the License is distributed on an "AS IS" BASIS,
 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
 #ifndef OPENSSL_HEADER_SSL_H
 #define OPENSSL_HEADER_SSL_H
 
 #include <openssl/base.h>   // IWYU pragma: export
 
 #include <openssl/bio.h>
 #include <openssl/buf.h>
 #include <openssl/pem.h>
 #include <openssl/span.h>
 #include <openssl/ssl3.h>
 #include <openssl/tls1.h>
 #include <openssl/x509.h>
 
 #if !defined(OPENSSL_WINDOWS)
 #include <sys/time.h>
 #endif
 
 // Forward-declare struct timeval. On Windows, it is defined in winsock2.h and
 // Windows headers define too many macros to be included in public headers.
 // However, only a forward declaration is needed.
 struct timeval;
 
 #if defined(__cplusplus)
 extern "C" {
 #endif
 
 
 // SSL implementation.
 
 
 // SSL contexts.
 //
 // |SSL_CTX| objects manage shared state and configuration between multiple TLS
 // or DTLS connections. Whether the connections are TLS or DTLS is selected by
 // an |SSL_METHOD| on creation.
 //
 // |SSL_CTX| are reference-counted and may be shared by connections across
 // multiple threads. Once shared, functions which change the |SSL_CTX|'s
 // configuration may not be used.
 
 // TLS_method is the |SSL_METHOD| used for TLS connections.
 OPENSSL_EXPORT const SSL_METHOD *TLS_method(void);
 
 // DTLS_method is the |SSL_METHOD| used for DTLS connections.
 OPENSSL_EXPORT const SSL_METHOD *DTLS_method(void);
 
 // TLS_with_buffers_method is like |TLS_method|, but avoids all use of
 // crypto/x509. All client connections created with |TLS_with_buffers_method|
 // will fail unless a certificate verifier is installed with
 // |SSL_set_custom_verify| or |SSL_CTX_set_custom_verify|.
 OPENSSL_EXPORT const SSL_METHOD *TLS_with_buffers_method(void);
 
 // DTLS_with_buffers_method is like |DTLS_method|, but avoids all use of
 // crypto/x509.
 OPENSSL_EXPORT const SSL_METHOD *DTLS_with_buffers_method(void);
 
 // SSL_CTX_new returns a newly-allocated |SSL_CTX| with default settings or NULL
 // on error.
 OPENSSL_EXPORT SSL_CTX *SSL_CTX_new(const SSL_METHOD *method);
 
 // SSL_CTX_up_ref increments the reference count of |ctx|. It returns one.
 OPENSSL_EXPORT int SSL_CTX_up_ref(SSL_CTX *ctx);
 
 // SSL_CTX_free releases memory associated with |ctx|.
 OPENSSL_EXPORT void SSL_CTX_free(SSL_CTX *ctx);
 
 
 // SSL connections.
 //
 // An |SSL| object represents a single TLS or DTLS connection. Although the
 // shared |SSL_CTX| is thread-safe, an |SSL| is not thread-safe and may only be
 // used on one thread at a time.
 
 // SSL_new returns a newly-allocated |SSL| using |ctx| or NULL on error. The new
 // connection inherits settings from |ctx| at the time of creation. Settings may
 // also be individually configured on the connection.
 //
 // On creation, an |SSL| is not configured to be either a client or server. Call
 // |SSL_set_connect_state| or |SSL_set_accept_state| to set this.
 OPENSSL_EXPORT SSL *SSL_new(SSL_CTX *ctx);
 
 // SSL_free releases memory associated with |ssl|.
 OPENSSL_EXPORT void SSL_free(SSL *ssl);
 
 // SSL_get_SSL_CTX returns the |SSL_CTX| associated with |ssl|. If
 // |SSL_set_SSL_CTX| is called, it returns the new |SSL_CTX|, not the initial
 // one.
 OPENSSL_EXPORT SSL_CTX *SSL_get_SSL_CTX(const SSL *ssl);
 
 // SSL_set_connect_state configures |ssl| to be a client.
 OPENSSL_EXPORT void SSL_set_connect_state(SSL *ssl);
 
 // SSL_set_accept_state configures |ssl| to be a server.
 OPENSSL_EXPORT void SSL_set_accept_state(SSL *ssl);
 
 // SSL_is_server returns one if |ssl| is configured as a server and zero
 // otherwise.
 OPENSSL_EXPORT int SSL_is_server(const SSL *ssl);
 
 // SSL_is_dtls returns one if |ssl| is a DTLS connection and zero otherwise.
 OPENSSL_EXPORT int SSL_is_dtls(const SSL *ssl);
 
 // SSL_is_quic returns one if |ssl| is a QUIC connection and zero otherwise.
 OPENSSL_EXPORT int SSL_is_quic(const SSL *ssl);
 
 // SSL_set_bio configures |ssl| to read from |rbio| and write to |wbio|. |ssl|
 // takes ownership of the two |BIO|s. If |rbio| and |wbio| are the same, |ssl|
 // only takes ownership of one reference. See |SSL_set0_rbio| and
 // |SSL_set0_wbio| for requirements on |rbio| and |wbio|, respectively.
 //
 // If |rbio| is the same as the currently configured |BIO| for reading, that
 // side is left untouched and is not freed.
 //
 // If |wbio| is the same as the currently configured |BIO| for writing AND |ssl|
 // is not currently configured to read from and write to the same |BIO|, that
 // side is left untouched and is not freed. This asymmetry is present for
 // historical reasons.
 //
 // Due to the very complex historical behavior of this function, calling this
 // function if |ssl| already has |BIO|s configured is deprecated. Prefer
 // |SSL_set0_rbio| and |SSL_set0_wbio| instead.
 OPENSSL_EXPORT void SSL_set_bio(SSL *ssl, BIO *rbio, BIO *wbio);
 
 // SSL_set0_rbio configures |ssl| to read from |rbio|. It takes ownership of
 // |rbio|. |rbio| may be a custom |BIO|, in which case it must implement
 // |BIO_read| with |BIO_meth_set_read|. In DTLS, |rbio| must be non-blocking to
 // properly handle timeouts and retransmits.
 //
 // Note that, although this function and |SSL_set0_wbio| may be called on the
 // same |BIO|, each call takes a reference. Use |BIO_up_ref| to balance this.
 OPENSSL_EXPORT void SSL_set0_rbio(SSL *ssl, BIO *rbio);
 
 // SSL_set0_wbio configures |ssl| to write to |wbio|. It takes ownership of
 // |wbio|. |wbio| may be a custom |BIO|, in which case it must implement
 // |BIO_write| with |BIO_meth_set_write|. It must additionally implement
 // |BIO_flush| with |BIO_meth_set_ctrl| and |BIO_CTRL_FLUSH|. If flushing is
 // unnecessary with |wbio|, |BIO_flush| should return one and do nothing.
 //
 // Note that, although this function and |SSL_set0_rbio| may be called on the
 // same |BIO|, each call takes a reference. Use |BIO_up_ref| to balance this.
 OPENSSL_EXPORT void SSL_set0_wbio(SSL *ssl, BIO *wbio);
 
 // SSL_get_rbio returns the |BIO| that |ssl| reads from.
 OPENSSL_EXPORT BIO *SSL_get_rbio(const SSL *ssl);
 
 // SSL_get_wbio returns the |BIO| that |ssl| writes to.
 OPENSSL_EXPORT BIO *SSL_get_wbio(const SSL *ssl);
 
 // SSL_get_fd calls |SSL_get_rfd|.
 OPENSSL_EXPORT int SSL_get_fd(const SSL *ssl);
 
 // SSL_get_rfd returns the file descriptor that |ssl| is configured to read
 // from. If |ssl|'s read |BIO| is not configured or doesn't wrap a file
 // descriptor then it returns -1.
 //
 // Note: On Windows, this may return either a file descriptor or a socket (cast
 // to int), depending on whether |ssl| was configured with a file descriptor or
 // socket |BIO|.
 OPENSSL_EXPORT int SSL_get_rfd(const SSL *ssl);
 
 // SSL_get_wfd returns the file descriptor that |ssl| is configured to write
 // to. If |ssl|'s write |BIO| is not configured or doesn't wrap a file
 // descriptor then it returns -1.
 //
 // Note: On Windows, this may return either a file descriptor or a socket (cast
 // to int), depending on whether |ssl| was configured with a file descriptor or
 // socket |BIO|.
 OPENSSL_EXPORT int SSL_get_wfd(const SSL *ssl);
 
 #if !defined(OPENSSL_NO_SOCK)
 // SSL_set_fd configures |ssl| to read from and write to |fd|. It returns one
 // on success and zero on allocation error. The caller retains ownership of
 // |fd|.
 //
 // On Windows, |fd| is cast to a |SOCKET| and used with Winsock APIs.
 OPENSSL_EXPORT int SSL_set_fd(SSL *ssl, int fd);
 
 // SSL_set_rfd configures |ssl| to read from |fd|. It returns one on success and
 // zero on allocation error. The caller retains ownership of |fd|.
 //
 // On Windows, |fd| is cast to a |SOCKET| and used with Winsock APIs.
 OPENSSL_EXPORT int SSL_set_rfd(SSL *ssl, int fd);
 
 // SSL_set_wfd configures |ssl| to write to |fd|. It returns one on success and
 // zero on allocation error. The caller retains ownership of |fd|.
 //
 // On Windows, |fd| is cast to a |SOCKET| and used with Winsock APIs.
 OPENSSL_EXPORT int SSL_set_wfd(SSL *ssl, int fd);
 #endif  // !OPENSSL_NO_SOCK
 
 // SSL_do_handshake continues the current handshake. If there is none or the
 // handshake has completed or False Started, it returns one. Otherwise, it
 // returns <= 0. The caller should pass the value into |SSL_get_error| to
 // determine how to proceed.
 //
 // In DTLS, the caller must drive retransmissions and timeouts. After calling
 // this function, the caller must use |DTLSv1_get_timeout| to determine the
 // current timeout, if any. If it expires before the application next calls into
 // |ssl|, call |DTLSv1_handle_timeout|. Note that DTLS handshake retransmissions
 // use fresh sequence numbers, so it is not sufficient to replay packets at the
 // transport.
 //
 // After the DTLS handshake, some retransmissions may remain. If |ssl| wrote
 // last in the handshake, it may need to retransmit the final flight in case of
 // packet loss. Additionally, in DTLS 1.3, it may need to retransmit
 // post-handshake messages. To handle these, the caller must always be prepared
 // to receive packets and process them with |SSL_read|, even when the
 // application protocol would otherwise not read from the connection.
 //
 // TODO(davidben): Ensure 0 is only returned on transport EOF.
 // https://crbug.com/466303.
 OPENSSL_EXPORT int SSL_do_handshake(SSL *ssl);
 
 // SSL_connect configures |ssl| as a client, if unconfigured, and calls
 // |SSL_do_handshake|.
 OPENSSL_EXPORT int SSL_connect(SSL *ssl);
 
 // SSL_accept configures |ssl| as a server, if unconfigured, and calls
 // |SSL_do_handshake|.
 OPENSSL_EXPORT int SSL_accept(SSL *ssl);
 
 // SSL_read reads up to |num| bytes from |ssl| into |buf|. It implicitly runs
 // any pending handshakes, including renegotiations when enabled. On success, it
 // returns the number of bytes read. Otherwise, it returns <= 0. The caller
 // should pass the value into |SSL_get_error| to determine how to proceed.
 //
 // In DTLS 1.3, the caller must also drive timeouts from retransmitting the
 // final flight of the handshake, as well as post-handshake messages. After
 // calling this function, the caller must use |DTLSv1_get_timeout| to determine
 // the current timeout, if any. If it expires before the application next calls
 // into |ssl|, call |DTLSv1_handle_timeout|.
 //
 // TODO(davidben): Ensure 0 is only returned on transport EOF.
 // https://crbug.com/466303.
 OPENSSL_EXPORT int SSL_read(SSL *ssl, void *buf, int num);
 
 // SSL_peek behaves like |SSL_read| but does not consume any bytes returned.
 OPENSSL_EXPORT int SSL_peek(SSL *ssl, void *buf, int num);
 
 // SSL_pending returns the number of buffered, decrypted bytes available for
 // read in |ssl|. It does not read from the transport.
 //
 // In DTLS, it is possible for this function to return zero while there is
 // buffered, undecrypted data from the transport in |ssl|. For example,
 // |SSL_read| may read a datagram with two records, decrypt the first, and leave
 // the second buffered for a subsequent call to |SSL_read|. Callers that wish to
 // detect this case can use |SSL_has_pending|.
 OPENSSL_EXPORT int SSL_pending(const SSL *ssl);
 
 // SSL_has_pending returns one if |ssl| has buffered, decrypted bytes available
 // for read, or if |ssl| has buffered data from the transport that has not yet
 // been decrypted. If |ssl| has neither, this function returns zero.
 //
 // In TLS, BoringSSL does not implement read-ahead, so this function returns one
 // if and only if |SSL_pending| would return a non-zero value. In DTLS, it is
 // possible for this function to return one while |SSL_pending| returns zero.
 // For example, |SSL_read| may read a datagram with two records, decrypt the
 // first, and leave the second buffered for a subsequent call to |SSL_read|.
 //
 // As a result, if this function returns one, the next call to |SSL_read| may
 // still fail, read from the transport, or both. The buffered, undecrypted data
 // may be invalid or incomplete.
 OPENSSL_EXPORT int SSL_has_pending(const SSL *ssl);
 
 // SSL_write writes up to |num| bytes from |buf| into |ssl|. It implicitly runs
 // any pending handshakes, including renegotiations when enabled. On success, it
 // returns the number of bytes written. Otherwise, it returns <= 0. The caller
 // should pass the value into |SSL_get_error| to determine how to proceed.
 //
 // In TLS, a non-blocking |SSL_write| differs from non-blocking |write| in that
 // a failed |SSL_write| still commits to the data passed in. When retrying, the
 // caller must supply the original write buffer (or a larger one containing the
 // original as a prefix). By default, retries will fail if they also do not
 // reuse the same |buf| pointer. This may be relaxed with
 // |SSL_MODE_ACCEPT_MOVING_WRITE_BUFFER|, but the buffer contents still must be
 // unchanged.
 //
 // By default, in TLS, |SSL_write| will not return success until all |num| bytes
 // are written. This may be relaxed with |SSL_MODE_ENABLE_PARTIAL_WRITE|. It
 // allows |SSL_write| to complete with a partial result when only part of the
 // input was written in a single record.
 //
 // In DTLS, neither |SSL_MODE_ACCEPT_MOVING_WRITE_BUFFER| and
 // |SSL_MODE_ENABLE_PARTIAL_WRITE| do anything. The caller may retry with a
 // different buffer freely. A single call to |SSL_write| only ever writes a
 // single record in a single packet, so |num| must be at most
 // |SSL3_RT_MAX_PLAIN_LENGTH|.
 //
 // TODO(davidben): Ensure 0 is only returned on transport EOF.
 // https://crbug.com/466303.
 OPENSSL_EXPORT int SSL_write(SSL *ssl, const void *buf, int num);
 
 // SSL_KEY_UPDATE_REQUESTED indicates that the peer should reply to a KeyUpdate
 // message with its own, thus updating traffic secrets for both directions on
 // the connection.
 #define SSL_KEY_UPDATE_REQUESTED 1
 
 // SSL_KEY_UPDATE_NOT_REQUESTED indicates that the peer should not reply with
 // it's own KeyUpdate message.
 #define SSL_KEY_UPDATE_NOT_REQUESTED 0
 
 // SSL_key_update queues a TLS 1.3 KeyUpdate message to be sent on |ssl|
 // if one is not already queued. The |request_type| argument must one of the
 // |SSL_KEY_UPDATE_*| values. This function requires that |ssl| have completed a
 // TLS >= 1.3 handshake. It returns one on success or zero on error.
 //
 // Note that this function does not _send_ the message itself. The next call to
 // |SSL_write| will cause the message to be sent. |SSL_write| may be called with
 // a zero length to flush a KeyUpdate message when no application data is
 // pending.
 OPENSSL_EXPORT int SSL_key_update(SSL *ssl, int request_type);
 
 // SSL_shutdown shuts down |ssl|. It runs in two stages. First, it sends
 // close_notify and returns zero or one on success or -1 on failure. Zero
 // indicates that close_notify was sent, but not received, and one additionally
 // indicates that the peer's close_notify had already been received.
 //
 // To then wait for the peer's close_notify, run |SSL_shutdown| to completion a
 // second time. This returns 1 on success and -1 on failure. Application data
 // is considered a fatal error at this point. To process or discard it, read
 // until close_notify with |SSL_read| instead.
 //
 // In both cases, on failure, pass the return value into |SSL_get_error| to
 // determine how to proceed.
 //
 // Most callers should stop at the first stage. Reading for close_notify is
 // primarily used for uncommon protocols where the underlying transport is
 // reused after TLS completes. Additionally, DTLS uses an unordered transport
 // and is unordered, so the second stage is a no-op in DTLS.
 OPENSSL_EXPORT int SSL_shutdown(SSL *ssl);
 
 // SSL_CTX_set_quiet_shutdown sets quiet shutdown on |ctx| to |mode|. If
 // enabled, |SSL_shutdown| will not send a close_notify alert or wait for one
 // from the peer. It will instead synchronously return one.
 OPENSSL_EXPORT void SSL_CTX_set_quiet_shutdown(SSL_CTX *ctx, int mode);
 
 // SSL_CTX_get_quiet_shutdown returns whether quiet shutdown is enabled for
 // |ctx|.
 OPENSSL_EXPORT int SSL_CTX_get_quiet_shutdown(const SSL_CTX *ctx);
 
 // SSL_set_quiet_shutdown sets quiet shutdown on |ssl| to |mode|. If enabled,
 // |SSL_shutdown| will not send a close_notify alert or wait for one from the
 // peer. It will instead synchronously return one.
 OPENSSL_EXPORT void SSL_set_quiet_shutdown(SSL *ssl, int mode);
 
 // SSL_get_quiet_shutdown returns whether quiet shutdown is enabled for
 // |ssl|.
 OPENSSL_EXPORT int SSL_get_quiet_shutdown(const SSL *ssl);
 
 // SSL_get_error returns a |SSL_ERROR_*| value for the most recent operation on
 // |ssl|. It should be called after an operation failed to determine whether the
 // error was fatal and, if not, when to retry.
 OPENSSL_EXPORT int SSL_get_error(const SSL *ssl, int ret_code);
 
 // SSL_ERROR_NONE indicates the operation succeeded.
 #define SSL_ERROR_NONE 0
 
 // SSL_ERROR_SSL indicates the operation failed within the library. The caller
 // may inspect the error queue (see |ERR_get_error|) for more information.
 #define SSL_ERROR_SSL 1
 
 // SSL_ERROR_WANT_READ indicates the operation failed attempting to read from
 // the transport. The caller may retry the operation when the transport is ready
 // for reading.
 #define SSL_ERROR_WANT_READ 2
 
 // SSL_ERROR_WANT_WRITE indicates the operation failed attempting to write to
 // the transport. The caller may retry the operation when the transport is ready
 // for writing.
 #define SSL_ERROR_WANT_WRITE 3
 
 // SSL_ERROR_WANT_X509_LOOKUP indicates the operation failed in calling the
 // |cert_cb| or |client_cert_cb|. The caller may retry the operation when the
 // callback is ready to return a certificate or one has been configured
 // externally.
 //
 // See also |SSL_CTX_set_cert_cb| and |SSL_CTX_set_client_cert_cb|.
 #define SSL_ERROR_WANT_X509_LOOKUP 4
 
 // SSL_ERROR_SYSCALL indicates the operation failed externally to the library.
 // The caller should consult the system-specific error mechanism. This is
 // typically |errno| but may be something custom if using a custom |BIO|. It
 // may also be signaled if the transport returned EOF, in which case the
 // operation's return value will be zero.
 #define SSL_ERROR_SYSCALL 5
 
 // SSL_ERROR_ZERO_RETURN indicates the operation failed because the connection
 // was cleanly shut down with a close_notify alert.
 #define SSL_ERROR_ZERO_RETURN 6
 
 // SSL_ERROR_WANT_CONNECT indicates the operation failed attempting to connect
 // the transport (the |BIO| signaled |BIO_RR_CONNECT|). The caller may retry the
 // operation when the transport is ready.
 #define SSL_ERROR_WANT_CONNECT 7
 
 // SSL_ERROR_WANT_ACCEPT indicates the operation failed attempting to accept a
 // connection from the transport (the |BIO| signaled |BIO_RR_ACCEPT|). The
 // caller may retry the operation when the transport is ready.
 //
 // TODO(davidben): Remove this. It's used by accept BIOs which are bizarre.
 #define SSL_ERROR_WANT_ACCEPT 8
 
 // SSL_ERROR_WANT_CHANNEL_ID_LOOKUP is never used.
 //
 // TODO(davidben): Remove this. Some callers reference it when stringifying
 // errors. They should use |SSL_error_description| instead.
 #define SSL_ERROR_WANT_CHANNEL_ID_LOOKUP 9
 
 // SSL_ERROR_PENDING_SESSION indicates the operation failed because the session
 // lookup callback indicated the session was unavailable. The caller may retry
 // the operation when lookup has completed.
 //
 // See also |SSL_CTX_sess_set_get_cb| and |SSL_magic_pending_session_ptr|.
 #define SSL_ERROR_PENDING_SESSION 11
 
 // SSL_ERROR_PENDING_CERTIFICATE indicates the operation failed because the
 // early callback indicated certificate lookup was incomplete. The caller may
 // retry the operation when lookup has completed.
 //
 // See also |SSL_CTX_set_select_certificate_cb|.
 #define SSL_ERROR_PENDING_CERTIFICATE 12
 
 // SSL_ERROR_WANT_PRIVATE_KEY_OPERATION indicates the operation failed because
 // a private key operation was unfinished. The caller may retry the operation
 // when the private key operation is complete.
 //
 // See also |SSL_set_private_key_method|, |SSL_CTX_set_private_key_method|, and
 // |SSL_CREDENTIAL_set_private_key_method|.
 #define SSL_ERROR_WANT_PRIVATE_KEY_OPERATION 13
 
 // SSL_ERROR_PENDING_TICKET indicates that a ticket decryption is pending. The
 // caller may retry the operation when the decryption is ready.
 //
 // See also |SSL_CTX_set_ticket_aead_method|.
 #define SSL_ERROR_PENDING_TICKET 14
 
 // SSL_ERROR_EARLY_DATA_REJECTED indicates that early data was rejected. The
 // caller should treat this as a connection failure and retry any operations
 // associated with the rejected early data. |SSL_reset_early_data_reject| may be
 // used to reuse the underlying connection for the retry.
 #define SSL_ERROR_EARLY_DATA_REJECTED 15
 
 // SSL_ERROR_WANT_CERTIFICATE_VERIFY indicates the operation failed because
 // certificate verification was incomplete. The caller may retry the operation
 // when certificate verification is complete.
 //
 // See also |SSL_CTX_set_custom_verify|.
 #define SSL_ERROR_WANT_CERTIFICATE_VERIFY 16
 
 #define SSL_ERROR_HANDOFF 17
 #define SSL_ERROR_HANDBACK 18
 
 // SSL_ERROR_WANT_RENEGOTIATE indicates the operation is pending a response to
 // a renegotiation request from the server. The caller may call
 // |SSL_renegotiate| to schedule a renegotiation and retry the operation.
 //
 // See also |ssl_renegotiate_explicit|.
 #define SSL_ERROR_WANT_RENEGOTIATE 19
 
 // SSL_ERROR_HANDSHAKE_HINTS_READY indicates the handshake has progressed enough
 // for |SSL_serialize_handshake_hints| to be called. See also
 // |SSL_request_handshake_hints|.
 #define SSL_ERROR_HANDSHAKE_HINTS_READY 20
 
 // SSL_error_description returns a string representation of |err|, where |err|
 // is one of the |SSL_ERROR_*| constants returned by |SSL_get_error|, or NULL
 // if the value is unrecognized.
 OPENSSL_EXPORT const char *SSL_error_description(int err);
 
 // SSL_set_mtu sets the |ssl|'s MTU in DTLS to |mtu|. It returns one on success
 // and zero on failure.
 OPENSSL_EXPORT int SSL_set_mtu(SSL *ssl, unsigned mtu);
 
 // DTLSv1_set_initial_timeout_duration sets the initial duration for a DTLS
 // handshake timeout.
 //
 // This duration overrides the default of 400 milliseconds, which is
 // recommendation of RFC 9147 for real-time protocols.
 OPENSSL_EXPORT void DTLSv1_set_initial_timeout_duration(SSL *ssl,
                                                         uint32_t duration_ms);
 
 // DTLSv1_get_timeout queries the running DTLS timers. If there are any in
 // progress, it sets |*out| to the time remaining until the first timer expires
 // and returns one. Otherwise, it returns zero. Timers may be scheduled both
 // during and after the handshake.
 //
 // When the timeout expires, call |DTLSv1_handle_timeout| to handle the
 // retransmit behavior.
 //
 // NOTE: This function must be queried again whenever the state machine changes,
 // including when |DTLSv1_handle_timeout| is called.
 OPENSSL_EXPORT int DTLSv1_get_timeout(const SSL *ssl, struct timeval *out);
 
 // DTLSv1_handle_timeout is called when a DTLS timeout expires. If no timeout
 // had expired, it returns 0. Otherwise, it handles the timeout and returns 1 on
 // success or -1 on error.
 //
 // This function may write to the transport (e.g. to retransmit messages) or
 // update |ssl|'s internal state and schedule an updated timer.
 //
 // The caller's external timer should be compatible with the one |ssl| queries
 // within some fudge factor. Otherwise, the call will be a no-op, but
 // |DTLSv1_get_timeout| will return an updated timeout.
 //
 // If the function returns -1, checking if |SSL_get_error| returns
 // |SSL_ERROR_WANT_WRITE| may be used to determine if the retransmit failed due
 // to a non-fatal error at the write |BIO|. In this case, when the |BIO| is
 // writable, the operation may be retried by calling the original function,
 // |SSL_do_handshake| or |SSL_read|.
 //
 // WARNING: This function breaks the usual return value convention.
 //
 // TODO(davidben): We can make this function entirely optional by just checking
 // the timers in |SSL_do_handshake| or |SSL_read|. Then timers behave like any
 // other retry condition: rerun the operation and the library will make what
 // progress it can.
 OPENSSL_EXPORT int DTLSv1_handle_timeout(SSL *ssl);
 
 
 // Protocol versions.
 
 #define DTLS1_VERSION_MAJOR 0xfe
 #define SSL3_VERSION_MAJOR 0x03
 
 #define SSL3_VERSION 0x0300
 #define TLS1_VERSION 0x0301
 #define TLS1_1_VERSION 0x0302
 #define TLS1_2_VERSION 0x0303
 #define TLS1_3_VERSION 0x0304
 
 #define DTLS1_VERSION 0xfeff
 #define DTLS1_2_VERSION 0xfefd
 #define DTLS1_3_VERSION 0xfefc
 
 // SSL_CTX_set_min_proto_version sets the minimum protocol version for |ctx| to
 // |version|. If |version| is zero, the default minimum version is used. It
 // returns one on success and zero if |version| is invalid.
 OPENSSL_EXPORT int SSL_CTX_set_min_proto_version(SSL_CTX *ctx,
                                                  uint16_t version);
 
 // SSL_CTX_set_max_proto_version sets the maximum protocol version for |ctx| to
 // |version|. If |version| is zero, the default maximum version is used. It
 // returns one on success and zero if |version| is invalid.
 OPENSSL_EXPORT int SSL_CTX_set_max_proto_version(SSL_CTX *ctx,
                                                  uint16_t version);
 
 // SSL_CTX_get_min_proto_version returns the minimum protocol version for |ctx|
 OPENSSL_EXPORT uint16_t SSL_CTX_get_min_proto_version(const SSL_CTX *ctx);
 
 // SSL_CTX_get_max_proto_version returns the maximum protocol version for |ctx|
 OPENSSL_EXPORT uint16_t SSL_CTX_get_max_proto_version(const SSL_CTX *ctx);
 
 // SSL_set_min_proto_version sets the minimum protocol version for |ssl| to
 // |version|. If |version| is zero, the default minimum version is used. It
 // returns one on success and zero if |version| is invalid.
 OPENSSL_EXPORT int SSL_set_min_proto_version(SSL *ssl, uint16_t version);
 
 // SSL_set_max_proto_version sets the maximum protocol version for |ssl| to
 // |version|. If |version| is zero, the default maximum version is used. It
 // returns one on success and zero if |version| is invalid.
 OPENSSL_EXPORT int SSL_set_max_proto_version(SSL *ssl, uint16_t version);
 
 // SSL_get_min_proto_version returns the minimum protocol version for |ssl|. If
 // the connection's configuration has been shed, 0 is returned.
 OPENSSL_EXPORT uint16_t SSL_get_min_proto_version(const SSL *ssl);
 
 // SSL_get_max_proto_version returns the maximum protocol version for |ssl|. If
 // the connection's configuration has been shed, 0 is returned.
 OPENSSL_EXPORT uint16_t SSL_get_max_proto_version(const SSL *ssl);
 
 // SSL_version returns the TLS or DTLS protocol version used by |ssl|, which is
 // one of the |*_VERSION| values. (E.g. |TLS1_2_VERSION|.) Before the version
 // is negotiated, the result is undefined.
 OPENSSL_EXPORT int SSL_version(const SSL *ssl);
 
 
 // Options.
 //
 // Options configure protocol behavior.
 
 // SSL_OP_NO_QUERY_MTU, in DTLS, disables querying the MTU from the underlying
 // |BIO|. Instead, the MTU is configured with |SSL_set_mtu|.
 #define SSL_OP_NO_QUERY_MTU 0x00001000L
 
 // SSL_OP_NO_TICKET disables session ticket support (RFC 5077).
 #define SSL_OP_NO_TICKET 0x00004000L
 
 // SSL_OP_CIPHER_SERVER_PREFERENCE configures servers to select ciphers and
 // ECDHE curves according to the server's preferences instead of the
 // client's.
 #define SSL_OP_CIPHER_SERVER_PREFERENCE 0x00400000L
 
 // The following flags toggle individual protocol versions. This is deprecated.
 // Use |SSL_CTX_set_min_proto_version| and |SSL_CTX_set_max_proto_version|
 // instead.
 #define SSL_OP_NO_TLSv1 0x04000000L
 #define SSL_OP_NO_TLSv1_2 0x08000000L
 #define SSL_OP_NO_TLSv1_1 0x10000000L
 #define SSL_OP_NO_TLSv1_3 0x20000000L
 #define SSL_OP_NO_DTLSv1 SSL_OP_NO_TLSv1
 #define SSL_OP_NO_DTLSv1_2 SSL_OP_NO_TLSv1_2
 
 // SSL_CTX_set_options enables all options set in |options| (which should be one
 // or more of the |SSL_OP_*| values, ORed together) in |ctx|. It returns a
 // bitmask representing the resulting enabled options.
 OPENSSL_EXPORT uint32_t SSL_CTX_set_options(SSL_CTX *ctx, uint32_t options);
 
 // SSL_CTX_clear_options disables all options set in |options| (which should be
 // one or more of the |SSL_OP_*| values, ORed together) in |ctx|. It returns a
 // bitmask representing the resulting enabled options.
 OPENSSL_EXPORT uint32_t SSL_CTX_clear_options(SSL_CTX *ctx, uint32_t options);
 
 // SSL_CTX_get_options returns a bitmask of |SSL_OP_*| values that represent all
 // the options enabled for |ctx|.
 OPENSSL_EXPORT uint32_t SSL_CTX_get_options(const SSL_CTX *ctx);
 
 // SSL_set_options enables all options set in |options| (which should be one or
 // more of the |SSL_OP_*| values, ORed together) in |ssl|. It returns a bitmask
 // representing the resulting enabled options.
 OPENSSL_EXPORT uint32_t SSL_set_options(SSL *ssl, uint32_t options);
 
 // SSL_clear_options disables all options set in |options| (which should be one
 // or more of the |SSL_OP_*| values, ORed together) in |ssl|. It returns a
 // bitmask representing the resulting enabled options.
 OPENSSL_EXPORT uint32_t SSL_clear_options(SSL *ssl, uint32_t options);
 
 // SSL_get_options returns a bitmask of |SSL_OP_*| values that represent all the
 // options enabled for |ssl|.
 OPENSSL_EXPORT uint32_t SSL_get_options(const SSL *ssl);
 
 
 // Modes.
 //
 // Modes configure API behavior.
 
 // SSL_MODE_ENABLE_PARTIAL_WRITE, in TLS, allows |SSL_write| to complete with a
 // partial result when the only part of the input was written in a single
 // record. In DTLS, it does nothing.
 #define SSL_MODE_ENABLE_PARTIAL_WRITE 0x00000001L
 
 // SSL_MODE_ACCEPT_MOVING_WRITE_BUFFER, in TLS, allows retrying an incomplete
 // |SSL_write| with a different buffer. However, |SSL_write| still assumes the
 // buffer contents are unchanged. This is not the default to avoid the
 // misconception that non-blocking |SSL_write| behaves like non-blocking
 // |write|. In DTLS, it does nothing.
 #define SSL_MODE_ACCEPT_MOVING_WRITE_BUFFER 0x00000002L
 
 // SSL_MODE_NO_AUTO_CHAIN disables automatically building a certificate chain
 // before sending certificates to the peer. This flag is set (and the feature
 // disabled) by default.
 // TODO(davidben): Remove this behavior. https://crbug.com/boringssl/42.
 #define SSL_MODE_NO_AUTO_CHAIN 0x00000008L
 
 // SSL_MODE_ENABLE_FALSE_START allows clients to send application data before
 // receipt of ChangeCipherSpec and Finished. This mode enables full handshakes
 // to 'complete' in one RTT. See RFC 7918.
 //
 // When False Start is enabled, |SSL_do_handshake| may succeed before the
 // handshake has completely finished. |SSL_write| will function at this point,
 // and |SSL_read| will transparently wait for the final handshake leg before
 // returning application data. To determine if False Start occurred or when the
 // handshake is completely finished, see |SSL_in_false_start|, |SSL_in_init|,
 // and |SSL_CB_HANDSHAKE_DONE| from |SSL_CTX_set_info_callback|.
 #define SSL_MODE_ENABLE_FALSE_START 0x00000080L
 
 // SSL_MODE_CBC_RECORD_SPLITTING causes multi-byte CBC records in TLS 1.0 to be
 // split in two: the first record will contain a single byte and the second will
 // contain the remainder. This effectively randomises the IV and prevents BEAST
 // attacks.
 #define SSL_MODE_CBC_RECORD_SPLITTING 0x00000100L
 
 // SSL_MODE_NO_SESSION_CREATION will cause any attempts to create a session to
 // fail with SSL_R_SESSION_MAY_NOT_BE_CREATED. This can be used to enforce that
 // session resumption is used for a given SSL*.
 #define SSL_MODE_NO_SESSION_CREATION 0x00000200L
 
 // SSL_MODE_SEND_FALLBACK_SCSV sends TLS_FALLBACK_SCSV in the ClientHello.
 // To be set only by applications that reconnect with a downgraded protocol
 // version; see RFC 7507 for details.
 //
 // DO NOT ENABLE THIS if your application attempts a normal handshake. Only use
 // this in explicit fallback retries, following the guidance in RFC 7507.
 #define SSL_MODE_SEND_FALLBACK_SCSV 0x00000400L
 
 // SSL_CTX_set_mode enables all modes set in |mode| (which should be one or more
 // of the |SSL_MODE_*| values, ORed together) in |ctx|. It returns a bitmask
 // representing the resulting enabled modes.
 OPENSSL_EXPORT uint32_t SSL_CTX_set_mode(SSL_CTX *ctx, uint32_t mode);
 
 // SSL_CTX_clear_mode disables all modes set in |mode| (which should be one or
 // more of the |SSL_MODE_*| values, ORed together) in |ctx|. It returns a
 // bitmask representing the resulting enabled modes.
 OPENSSL_EXPORT uint32_t SSL_CTX_clear_mode(SSL_CTX *ctx, uint32_t mode);
 
 // SSL_CTX_get_mode returns a bitmask of |SSL_MODE_*| values that represent all
 // the modes enabled for |ssl|.
 OPENSSL_EXPORT uint32_t SSL_CTX_get_mode(const SSL_CTX *ctx);
 
 // SSL_set_mode enables all modes set in |mode| (which should be one or more of
 // the |SSL_MODE_*| values, ORed together) in |ssl|. It returns a bitmask
 // representing the resulting enabled modes.
 OPENSSL_EXPORT uint32_t SSL_set_mode(SSL *ssl, uint32_t mode);
 
 // SSL_clear_mode disables all modes set in |mode| (which should be one or more
 // of the |SSL_MODE_*| values, ORed together) in |ssl|. It returns a bitmask
 // representing the resulting enabled modes.
 OPENSSL_EXPORT uint32_t SSL_clear_mode(SSL *ssl, uint32_t mode);
 
 // SSL_get_mode returns a bitmask of |SSL_MODE_*| values that represent all the
 // modes enabled for |ssl|.
 OPENSSL_EXPORT uint32_t SSL_get_mode(const SSL *ssl);
 
 // SSL_CTX_set0_buffer_pool sets a |CRYPTO_BUFFER_POOL| that will be used to
 // store certificates. This can allow multiple connections to share
 // certificates and thus save memory.
 //
 // The SSL_CTX does not take ownership of |pool| and the caller must ensure
 // that |pool| outlives |ctx| and all objects linked to it, including |SSL|,
 // |X509| and |SSL_SESSION| objects. Basically, don't ever free |pool|.
 OPENSSL_EXPORT void SSL_CTX_set0_buffer_pool(SSL_CTX *ctx,
                                              CRYPTO_BUFFER_POOL *pool);
 
 
 // Credentials.
 //
 // TLS endpoints may present authentication during the handshake, usually using
 // X.509 certificates. This is typically required for servers and optional for
 // clients. BoringSSL uses the |SSL_CREDENTIAL| object to abstract between
 // different kinds of credentials, as well as configure automatic selection
 // between multiple credentials. This may be used to select between ECDSA and
 // RSA certificates.
 //
 // |SSL_CTX| and |SSL| objects maintain lists of credentials in preference
 // order. During the handshake, BoringSSL will select the first usable
 // credential from the list. Non-credential APIs, such as
 // |SSL_CTX_use_certificate|, configure a "legacy credential", which is
 // appended to this list if configured. Using the legacy credential is the same
 // as configuring an equivalent credential with the |SSL_CREDENTIAL| API.
 //
 // When selecting credentials, BoringSSL considers the credential's type, its
 // cryptographic capabilities, and capabilities advertised by the peer. This
 // varies between TLS versions but includes:
 //
 // - Whether the peer supports the leaf certificate key
 // - Whether there is a common signature algorithm that is compatible with the
 //   credential
 // - Whether there is a common cipher suite that is compatible with the
 //   credential
 //
 // WARNING: In TLS 1.2 and below, there is no mechanism for servers to advertise
 // supported ECDSA curves to the client. BoringSSL clients will assume the
 // server accepts all ECDSA curves in client certificates.
 //
 // By default, BoringSSL does not check the following, though we may add APIs
 // in the future to enable them on a per-credential basis.
 //
 // - Whether the peer supports the signature algorithms in the certificate chain
 // - Whether the a server certificate is compatible with the server_name
 //   extension (SNI)
 //
 // Credentials may be configured before the handshake or dynamically in the
 // early callback (see |SSL_CTX_set_select_certificate_cb|) and certificate
 // callback (see |SSL_CTX_set_cert_cb|). These callbacks allow applications to
 // use BoringSSL's built-in selection logic in tandem with custom logic. For
 // example, a callback could evaluate application-specific SNI rules to filter
 // down to an ECDSA and RSA credential, then configure both for BoringSSL to
 // select between the two.
 
 // SSL_CREDENTIAL_new_x509 returns a new, empty X.509 credential, or NULL on
 // error. Callers should release the result with |SSL_CREDENTIAL_free| when
 // done.
 //
 // Callers should configure a certificate chain and private key on the
 // credential, along with other properties, then add it with
 // |SSL_CTX_add1_credential|.
 OPENSSL_EXPORT SSL_CREDENTIAL *SSL_CREDENTIAL_new_x509(void);
 
 // SSL_CREDENTIAL_up_ref increments the reference count of |cred|.
 OPENSSL_EXPORT void SSL_CREDENTIAL_up_ref(SSL_CREDENTIAL *cred);
 
 // SSL_CREDENTIAL_free decrements the reference count of |cred|. If it reaches
 // zero, all data referenced by |cred| and |cred| itself are released.
 OPENSSL_EXPORT void SSL_CREDENTIAL_free(SSL_CREDENTIAL *cred);
 
 // SSL_CREDENTIAL_set1_private_key sets |cred|'s private key to |cred|. It
 // returns one on success and zero on failure.
 OPENSSL_EXPORT int SSL_CREDENTIAL_set1_private_key(SSL_CREDENTIAL *cred,
                                                    EVP_PKEY *key);
 
 // SSL_CREDENTIAL_set1_signing_algorithm_prefs configures |cred| to use |prefs|
 // as the preference list when signing with |cred|'s private key. It returns one
 // on success and zero on error. |prefs| should not include the internal-only
 // value |SSL_SIGN_RSA_PKCS1_MD5_SHA1|.
 //
 // It is an error to call this function with delegated credentials (see
 // |SSL_CREDENTIAL_new_delegated|) because delegated credentials already
 // constrain the key to a single algorithm.
 OPENSSL_EXPORT int SSL_CREDENTIAL_set1_signing_algorithm_prefs(
     SSL_CREDENTIAL *cred, const uint16_t *prefs, size_t num_prefs);
 
 // SSL_CREDENTIAL_set1_cert_chain sets |cred|'s certificate chain, starting from
 // the leaf, to |num_cert|s certificates from |certs|. It returns one on success
 // and zero on error.
 OPENSSL_EXPORT int SSL_CREDENTIAL_set1_cert_chain(SSL_CREDENTIAL *cred,
                                                   CRYPTO_BUFFER *const *certs,
                                                   size_t num_certs);
 
 // SSL_CREDENTIAL_set1_ocsp_response sets |cred|'s stapled OCSP response to
 // |ocsp|. It returns one on success and zero on error.
 OPENSSL_EXPORT int SSL_CREDENTIAL_set1_ocsp_response(SSL_CREDENTIAL *cred,
                                                      CRYPTO_BUFFER *ocsp);
 
 // SSL_CREDENTIAL_set1_certificate_properties parses
 // |certificate_property_list| as a CertificatePropertyList (see Section 6 of
 // draft-ietf-tls-trust-anchor-ids-00) and applies recognized properties to
 // |cred|. It returns one on success and zero on error. It is an error if
 // |certificate_property_list| does not parse correctly, or if any recognized
 // properties from |certificate_property_list| cannot be applied to |cred|.
 //
 // CertificatePropertyList is an extensible structure which allows serving
 // properties of a certificate chain to be passed from a CA, through an
 // application's issuance and configuration pipeline, and to the TLS serving
 // logic, without requiring application changes for each property defined.
 //
 // BoringSSL currently supports the following properties:
 // * trust_anchor_identifier (see |SSL_CREDENTIAL_set1_trust_anchor_id|)
 //
 // Note this function does not automatically enable issuer matching. Callers
 // must separately call |SSL_CREDENTIAL_set_must_match_issuer| if desired.
 OPENSSL_EXPORT int SSL_CREDENTIAL_set1_certificate_properties(
     SSL_CREDENTIAL *cred, CRYPTO_BUFFER *cert_property_list);
 
 // SSL_CREDENTIAL_set1_signed_cert_timestamp_list sets |cred|'s list of signed
 // certificate timestamps |sct_list|. |sct_list| must contain one or more SCT
 // structures serialised as a SignedCertificateTimestampList (see
 // https://tools.ietf.org/html/rfc6962#section-3.3) – i.e. each SCT is prefixed
 // by a big-endian, uint16 length and the concatenation of one or more such
 // prefixed SCTs are themselves also prefixed by a uint16 length. It returns one
 // on success and zero on error.
 OPENSSL_EXPORT int SSL_CREDENTIAL_set1_signed_cert_timestamp_list(
     SSL_CREDENTIAL *cred, CRYPTO_BUFFER *sct_list);
 
 // SSL_CREDENTIAL_set_must_match_issuer configures whether |cred| should check
 // if the peer supports the certificate chain's issuer.
 //
 // If |match| is non-zero, |cred| will only be applicable when the certificate
 // chain is issued by some CA requested by the peer in the
 // certificate_authorities extension or, if |cred| has a trust anchor ID (see
 // |SSL_CREDENTIAL_set1_trust_anchor_id|), the trust_anchors extension. |cred|'s
 // certificate chain must then be a correctly ordered certification path.
 //
 // If |match| is zero (default), |cred| will not be conditioned on the peer's
 // requested CAs. This can be used for certificate chains that are assumed to be
 // usable by most peers.
 //
 // This setting can be used for certificate chains that may not be usable by all
 // peers, e.g. chains with fewer cross-signs or issued from a newer CA. The
 // credential list is tried in order, so more specific credentials that enable
 // issuer matching should generally be ordered before less specific credentials
 // that do not.
 OPENSSL_EXPORT void SSL_CREDENTIAL_set_must_match_issuer(SSL_CREDENTIAL *cred,
                                                          int match);
 
 // SSL_CTX_add1_credential appends |cred| to |ctx|'s credential list. It returns
 // one on success and zero on error. The credential list is maintained in order
 // of decreasing preference, so earlier calls are preferred over later calls.
 //
 // After calling this function, it is an error to modify |cred|. Doing so may
 // result in inconsistent handshake behavior or race conditions.
 OPENSSL_EXPORT int SSL_CTX_add1_credential(SSL_CTX *ctx, SSL_CREDENTIAL *cred);
 
 // SSL_add1_credential appends |cred| to |ssl|'s credential list. It returns one
 // on success and zero on error. The credential list is maintained in order of
 // decreasing preference, so earlier calls are preferred over later calls.
 //
 // After calling this function, it is an error to modify |cred|. Doing so may
 // result in inconsistent handshake behavior or race conditions.
 OPENSSL_EXPORT int SSL_add1_credential(SSL *ssl, SSL_CREDENTIAL *cred);
 
 // SSL_certs_clear removes all credentials configured on |ssl|. It also removes
 // the certificate chain and private key on the legacy credential.
 OPENSSL_EXPORT void SSL_certs_clear(SSL *ssl);
 
 // SSL_get0_selected_credential returns the credential in use in the current
 // handshake on |ssl|. If there is current handshake on |ssl| or if the
 // handshake has not progressed to this point, it returns NULL.
 //
 // This function is intended for use with |SSL_CREDENTIAL_get_ex_data|. It may
 // be called from handshake callbacks, such as those in
 // |SSL_PRIVATE_KEY_METHOD|, to trigger credential-specific behavior.
 //
 // In applications that use the older APIs, such as |SSL_use_certificate|, this
 // function may return an internal |SSL_CREDENTIAL| object. This internal object
 // will have no ex_data installed. To avoid this, it is recommended that callers
 // moving to |SSL_CREDENTIAL| use the new APIs consistently.
 OPENSSL_EXPORT const SSL_CREDENTIAL *SSL_get0_selected_credential(
     const SSL *ssl);
 
 
 // Configuring certificates and private keys.
 //
 // These functions configure the connection's leaf certificate, private key, and
 // certificate chain. The certificate chain is ordered leaf to root (as sent on
 // the wire) but does not include the leaf. Both client and server certificates
 // use these functions.
 //
 // Prefer to configure the certificate before the private key. If configured in
 // the other order, inconsistent private keys will be silently dropped, rather
 // than return an error. Additionally, overwriting a previously-configured
 // certificate and key pair only works if the certificate is configured first.
 //
 // Each of these functions configures the single "legacy credential" on the
 // |SSL_CTX| or |SSL|. To select between multiple certificates, use
 // |SSL_CREDENTIAL_new_x509| and other APIs to configure a list of credentials.
 
 // SSL_CTX_use_certificate sets |ctx|'s leaf certificate to |x509|. It returns
 // one on success and zero on failure. If |ctx| has a private key which is
 // inconsistent with |x509|, the private key is silently dropped.
 OPENSSL_EXPORT int SSL_CTX_use_certificate(SSL_CTX *ctx, X509 *x509);
 
 // SSL_use_certificate sets |ssl|'s leaf certificate to |x509|. It returns one
 // on success and zero on failure. If |ssl| has a private key which is
 // inconsistent with |x509|, the private key is silently dropped.
 OPENSSL_EXPORT int SSL_use_certificate(SSL *ssl, X509 *x509);
 
 // SSL_CTX_use_PrivateKey sets |ctx|'s private key to |pkey|. It returns one on
 // success and zero on failure. If |ctx| had a private key or
 // |SSL_PRIVATE_KEY_METHOD| previously configured, it is replaced.
 OPENSSL_EXPORT int SSL_CTX_use_PrivateKey(SSL_CTX *ctx, EVP_PKEY *pkey);
 
 // SSL_use_PrivateKey sets |ssl|'s private key to |pkey|. It returns one on
 // success and zero on failure. If |ssl| had a private key or
 // |SSL_PRIVATE_KEY_METHOD| previously configured, it is replaced.
 OPENSSL_EXPORT int SSL_use_PrivateKey(SSL *ssl, EVP_PKEY *pkey);
 
 // SSL_CTX_set0_chain sets |ctx|'s certificate chain, excluding the leaf, to
 // |chain|. On success, it returns one and takes ownership of |chain|.
 // Otherwise, it returns zero.
 OPENSSL_EXPORT int SSL_CTX_set0_chain(SSL_CTX *ctx, STACK_OF(X509) *chain);
 
 // SSL_CTX_set1_chain sets |ctx|'s certificate chain, excluding the leaf, to
 // |chain|. It returns one on success and zero on failure. The caller retains
 // ownership of |chain| and may release it freely.
 OPENSSL_EXPORT int SSL_CTX_set1_chain(SSL_CTX *ctx, STACK_OF(X509) *chain);
 
 // SSL_set0_chain sets |ssl|'s certificate chain, excluding the leaf, to
 // |chain|. On success, it returns one and takes ownership of |chain|.
 // Otherwise, it returns zero.
 OPENSSL_EXPORT int SSL_set0_chain(SSL *ssl, STACK_OF(X509) *chain);
 
 // SSL_set1_chain sets |ssl|'s certificate chain, excluding the leaf, to
 // |chain|. It returns one on success and zero on failure. The caller retains
 // ownership of |chain| and may release it freely.
 OPENSSL_EXPORT int SSL_set1_chain(SSL *ssl, STACK_OF(X509) *chain);
 
 // SSL_CTX_add0_chain_cert appends |x509| to |ctx|'s certificate chain. On
 // success, it returns one and takes ownership of |x509|. Otherwise, it returns
 // zero.
 OPENSSL_EXPORT int SSL_CTX_add0_chain_cert(SSL_CTX *ctx, X509 *x509);
 
 // SSL_CTX_add1_chain_cert appends |x509| to |ctx|'s certificate chain. It
 // returns one on success and zero on failure. The caller retains ownership of
 // |x509| and may release it freely.
 OPENSSL_EXPORT int SSL_CTX_add1_chain_cert(SSL_CTX *ctx, X509 *x509);
 
 // SSL_add0_chain_cert appends |x509| to |ctx|'s certificate chain. On success,
 // it returns one and takes ownership of |x509|. Otherwise, it returns zero.
 OPENSSL_EXPORT int SSL_add0_chain_cert(SSL *ssl, X509 *x509);
 
 // SSL_CTX_add_extra_chain_cert calls |SSL_CTX_add0_chain_cert|.
 OPENSSL_EXPORT int SSL_CTX_add_extra_chain_cert(SSL_CTX *ctx, X509 *x509);
 
 // SSL_add1_chain_cert appends |x509| to |ctx|'s certificate chain. It returns
 // one on success and zero on failure. The caller retains ownership of |x509|
 // and may release it freely.
 OPENSSL_EXPORT int SSL_add1_chain_cert(SSL *ssl, X509 *x509);
 
 // SSL_CTX_clear_chain_certs clears |ctx|'s certificate chain and returns
 // one.
 OPENSSL_EXPORT int SSL_CTX_clear_chain_certs(SSL_CTX *ctx);
 
 // SSL_CTX_clear_extra_chain_certs calls |SSL_CTX_clear_chain_certs|.
 OPENSSL_EXPORT int SSL_CTX_clear_extra_chain_certs(SSL_CTX *ctx);
 
 // SSL_clear_chain_certs clears |ssl|'s certificate chain and returns one.
 OPENSSL_EXPORT int SSL_clear_chain_certs(SSL *ssl);
 
 // SSL_CTX_set_cert_cb sets a callback that is called to select a certificate.
 // The callback returns one on success, zero on internal error, and a negative
 // number on failure or to pause the handshake. If the handshake is paused,
 // |SSL_get_error| will return |SSL_ERROR_WANT_X509_LOOKUP|.
 //
 // On the client, the callback may call |SSL_get0_certificate_types| and
 // |SSL_get_client_CA_list| for information on the server's certificate
 // request.
 //
 // On the server, the callback will be called after extensions have been
 // processed, but before the resumption decision has been made. This differs
 // from OpenSSL which handles resumption before selecting the certificate.
 OPENSSL_EXPORT void SSL_CTX_set_cert_cb(SSL_CTX *ctx,
                                         int (*cb)(SSL *ssl, void *arg),
                                         void *arg);
 
 // SSL_set_cert_cb sets a callback that is called to select a certificate. The
 // callback returns one on success, zero on internal error, and a negative
 // number on failure or to pause the handshake. If the handshake is paused,
 // |SSL_get_error| will return |SSL_ERROR_WANT_X509_LOOKUP|.
 //
 // On the client, the callback may call |SSL_get0_certificate_types| and
 // |SSL_get_client_CA_list| for information on the server's certificate
 // request.
 //
 // On the server, the callback will be called after extensions have been
 // processed, but before the resumption decision has been made. This differs
 // from OpenSSL which handles resumption before selecting the certificate.
 OPENSSL_EXPORT void SSL_set_cert_cb(SSL *ssl, int (*cb)(SSL *ssl, void *arg),
                                     void *arg);
 
 // SSL_get0_certificate_types, for a client, sets |*out_types| to an array
 // containing the client certificate types requested by a server. It returns the
 // length of the array. Note this list is always empty in TLS 1.3. The server
 // will instead send signature algorithms. See
 // |SSL_get0_peer_verify_algorithms|.
 //
 // The behavior of this function is undefined except during the callbacks set by
 // by |SSL_CTX_set_cert_cb| and |SSL_CTX_set_client_cert_cb| or when the
 // handshake is paused because of them.
 OPENSSL_EXPORT size_t SSL_get0_certificate_types(const SSL *ssl,
                                                  const uint8_t **out_types);
 
 // SSL_get0_peer_verify_algorithms sets |*out_sigalgs| to an array containing
 // the signature algorithms the peer is able to verify. It returns the length of
 // the array. Note these values are only sent starting TLS 1.2 and only
 // mandatory starting TLS 1.3. If not sent, the empty array is returned. For the
 // historical client certificate types list, see |SSL_get0_certificate_types|.
 //
 // The behavior of this function is undefined except during the callbacks set by
 // by |SSL_CTX_set_cert_cb| and |SSL_CTX_set_client_cert_cb| or when the
 // handshake is paused because of them.
 OPENSSL_EXPORT size_t
 SSL_get0_peer_verify_algorithms(const SSL *ssl, const uint16_t **out_sigalgs);
 
 // SSL_get0_peer_delegation_algorithms sets |*out_sigalgs| to an array
 // containing the signature algorithms the peer is willing to use with delegated
 // credentials.  It returns the length of the array. If not sent, the empty
 // array is returned.
 //
 // The behavior of this function is undefined except during the callbacks set by
 // by |SSL_CTX_set_cert_cb| and |SSL_CTX_set_client_cert_cb| or when the
 // handshake is paused because of them.
 OPENSSL_EXPORT size_t SSL_get0_peer_delegation_algorithms(
     const SSL *ssl, const uint16_t **out_sigalgs);
 
 // SSL_CTX_get0_certificate returns |ctx|'s leaf certificate.
 OPENSSL_EXPORT X509 *SSL_CTX_get0_certificate(const SSL_CTX *ctx);
 
 // SSL_get_certificate returns |ssl|'s leaf certificate.
 OPENSSL_EXPORT X509 *SSL_get_certificate(const SSL *ssl);
 
 // SSL_CTX_get0_privatekey returns |ctx|'s private key.
 OPENSSL_EXPORT EVP_PKEY *SSL_CTX_get0_privatekey(const SSL_CTX *ctx);
 
 // SSL_get_privatekey returns |ssl|'s private key.
 OPENSSL_EXPORT EVP_PKEY *SSL_get_privatekey(const SSL *ssl);
 
 // SSL_CTX_get0_chain_certs sets |*out_chain| to |ctx|'s certificate chain and
 // returns one.
 OPENSSL_EXPORT int SSL_CTX_get0_chain_certs(const SSL_CTX *ctx,
                                             STACK_OF(X509) **out_chain);
 
 // SSL_CTX_get_extra_chain_certs calls |SSL_CTX_get0_chain_certs|.
 OPENSSL_EXPORT int SSL_CTX_get_extra_chain_certs(const SSL_CTX *ctx,
                                                  STACK_OF(X509) **out_chain);
 
 // SSL_get0_chain_certs sets |*out_chain| to |ssl|'s certificate chain and
 // returns one.
 OPENSSL_EXPORT int SSL_get0_chain_certs(const SSL *ssl,
                                         STACK_OF(X509) **out_chain);
 
 // SSL_CTX_set_signed_cert_timestamp_list sets the list of signed certificate
 // timestamps that is sent to clients that request it. The |list| argument must
 // contain one or more SCT structures serialised as a SignedCertificateTimestamp
 // List (see https://tools.ietf.org/html/rfc6962#section-3.3) – i.e. each SCT
 // is prefixed by a big-endian, uint16 length and the concatenation of one or
 // more such prefixed SCTs are themselves also prefixed by a uint16 length. It
 // returns one on success and zero on error. The caller retains ownership of
 // |list|.
 OPENSSL_EXPORT int SSL_CTX_set_signed_cert_timestamp_list(SSL_CTX *ctx,
                                                           const uint8_t *list,
                                                           size_t list_len);
 
 // SSL_set_signed_cert_timestamp_list sets the list of signed certificate
 // timestamps that is sent to clients that request is. The same format as the
 // one used for |SSL_CTX_set_signed_cert_timestamp_list| applies. The caller
 // retains ownership of |list|.
 OPENSSL_EXPORT int SSL_set_signed_cert_timestamp_list(SSL *ctx,
                                                       const uint8_t *list,
                                                       size_t list_len);
 
 // SSL_CTX_set_ocsp_response sets the OCSP response that is sent to clients
 // which request it. It returns one on success and zero on error. The caller
 // retains ownership of |response|.
 OPENSSL_EXPORT int SSL_CTX_set_ocsp_response(SSL_CTX *ctx,
                                              const uint8_t *response,
                                              size_t response_len);
 
 // SSL_set_ocsp_response sets the OCSP response that is sent to clients which
 // request it. It returns one on success and zero on error. The caller retains
 // ownership of |response|.
 OPENSSL_EXPORT int SSL_set_ocsp_response(SSL *ssl, const uint8_t *response,
                                          size_t response_len);
 
 // SSL_SIGN_* are signature algorithm values as defined in TLS 1.3.
 #define SSL_SIGN_RSA_PKCS1_SHA1 0x0201
 #define SSL_SIGN_RSA_PKCS1_SHA256 0x0401
 #define SSL_SIGN_RSA_PKCS1_SHA384 0x0501
 #define SSL_SIGN_RSA_PKCS1_SHA512 0x0601
 #define SSL_SIGN_ECDSA_SHA1 0x0203
 #define SSL_SIGN_ECDSA_SECP256R1_SHA256 0x0403
 #define SSL_SIGN_ECDSA_SECP384R1_SHA384 0x0503
 #define SSL_SIGN_ECDSA_SECP521R1_SHA512 0x0603
 #define SSL_SIGN_RSA_PSS_RSAE_SHA256 0x0804
 #define SSL_SIGN_RSA_PSS_RSAE_SHA384 0x0805
 #define SSL_SIGN_RSA_PSS_RSAE_SHA512 0x0806
 #define SSL_SIGN_ED25519 0x0807
 
 // SSL_SIGN_RSA_PKCS1_SHA256_LEGACY is a backport of RSASSA-PKCS1-v1_5 with
 // SHA-256 to TLS 1.3. It is disabled by default and only defined for client
 // certificates.
 #define SSL_SIGN_RSA_PKCS1_SHA256_LEGACY 0x0420
 
 // SSL_SIGN_RSA_PKCS1_MD5_SHA1 is an internal signature algorithm used to
 // specify raw RSASSA-PKCS1-v1_5 with an MD5/SHA-1 concatenation, as used in TLS
 // before TLS 1.2.
 #define SSL_SIGN_RSA_PKCS1_MD5_SHA1 0xff01
 
 // SSL_get_signature_algorithm_name returns a human-readable name for |sigalg|,
 // or NULL if unknown. If |include_curve| is one, the curve for ECDSA algorithms
 // is included as in TLS 1.3. Otherwise, it is excluded as in TLS 1.2.
 OPENSSL_EXPORT const char *SSL_get_signature_algorithm_name(uint16_t sigalg,
                                                             int include_curve);
 
 // SSL_get_all_signature_algorithm_names outputs a list of possible strings
 // |SSL_get_signature_algorithm_name| may return in this version of BoringSSL.
 // It writes at most |max_out| entries to |out| and returns the total number it
 // would have written, if |max_out| had been large enough. |max_out| may be
 // initially set to zero to size the output.
 //
 // This function is only intended to help initialize tables in callers that want
 // possible strings pre-declared. This list would not be suitable to set a list
 // of supported features. It is in no particular order, and may contain
 // placeholder, experimental, or deprecated values that do not apply to every
 // caller. Future versions of BoringSSL may also return strings not in this
 // list, so this does not apply if, say, sending strings across services.
 OPENSSL_EXPORT size_t SSL_get_all_signature_algorithm_names(const char **out,
                                                             size_t max_out);
 
 // SSL_get_signature_algorithm_key_type returns the key type associated with
 // |sigalg| as an |EVP_PKEY_*| constant or |EVP_PKEY_NONE| if unknown.
 OPENSSL_EXPORT int SSL_get_signature_algorithm_key_type(uint16_t sigalg);
 
 // SSL_get_signature_algorithm_digest returns the digest function associated
 // with |sigalg| or |NULL| if |sigalg| has no prehash (Ed25519) or is unknown.
 OPENSSL_EXPORT const EVP_MD *SSL_get_signature_algorithm_digest(
     uint16_t sigalg);
 
 // SSL_is_signature_algorithm_rsa_pss returns one if |sigalg| is an RSA-PSS
 // signature algorithm and zero otherwise.
 OPENSSL_EXPORT int SSL_is_signature_algorithm_rsa_pss(uint16_t sigalg);
 
 // SSL_CTX_set_signing_algorithm_prefs configures |ctx| to use |prefs| as the
 // preference list when signing with |ctx|'s private key in TLS 1.2 and up. It
 // returns one on success and zero on error. |prefs| should not include the
 // internal-only TLS 1.0 value |SSL_SIGN_RSA_PKCS1_MD5_SHA1|.
 //
 // This setting is not used in TLS 1.0 and 1.1. Those protocols always sign a
 // hardcoded algorithm (an MD5/SHA-1 concatenation for RSA, and SHA-1 for
 // ECDSA). BoringSSL will use those algorithms if and only if those versions are
 // used. To disable them, set the minimum version to TLS 1.2 (default) or
 // higher.
 OPENSSL_EXPORT int SSL_CTX_set_signing_algorithm_prefs(SSL_CTX *ctx,
                                                        const uint16_t *prefs,
                                                        size_t num_prefs);
 
 // SSL_set_signing_algorithm_prefs configures |ssl| to use |prefs| as the
 // preference list when signing with |ssl|'s private key in TLS 1.2 and up. It
 // returns one on success and zero on error. |prefs| should not include the
 // internal-only TLS 1.0 value |SSL_SIGN_RSA_PKCS1_MD5_SHA1|.
 //
 // This setting is not used in TLS 1.0 and 1.1. Those protocols always sign a
 // hardcoded algorithm (an MD5/SHA-1 concatenation for RSA, and SHA-1 for
 // ECDSA). BoringSSL will use those algorithms if and only if those versions are
 // used. To disable them, set the minimum version to TLS 1.2 (default) or
 // higher.
 OPENSSL_EXPORT int SSL_set_signing_algorithm_prefs(SSL *ssl,
                                                    const uint16_t *prefs,
                                                    size_t num_prefs);
 
 
 // Certificate and private key convenience functions.
 
 // SSL_CTX_set_chain_and_key sets the certificate chain and private key for a
 // TLS client or server. References to the given |CRYPTO_BUFFER| and |EVP_PKEY|
 // objects are added as needed. Exactly one of |privkey| or |privkey_method|
 // may be non-NULL. Returns one on success and zero on error.
 OPENSSL_EXPORT int SSL_CTX_set_chain_and_key(
     SSL_CTX *ctx, CRYPTO_BUFFER *const *certs, size_t num_certs,
     EVP_PKEY *privkey, const SSL_PRIVATE_KEY_METHOD *privkey_method);
 
 // SSL_set_chain_and_key sets the certificate chain and private key for a TLS
 // client or server. References to the given |CRYPTO_BUFFER| and |EVP_PKEY|
 // objects are added as needed. Exactly one of |privkey| or |privkey_method|
 // may be non-NULL. Returns one on success and zero on error.
 OPENSSL_EXPORT int SSL_set_chain_and_key(
     SSL *ssl, CRYPTO_BUFFER *const *certs, size_t num_certs, EVP_PKEY *privkey,
     const SSL_PRIVATE_KEY_METHOD *privkey_method);
 
 // SSL_CTX_get0_chain returns the list of |CRYPTO_BUFFER|s that were set by
 // |SSL_CTX_set_chain_and_key|. Reference counts are not incremented by this
 // call. The return value may be |NULL| if no chain has been set.
 //
 // (Note: if a chain was configured by non-|CRYPTO_BUFFER|-based functions then
 // the return value is undefined and, even if not NULL, the stack itself may
 // contain nullptrs. Thus you shouldn't mix this function with
 // non-|CRYPTO_BUFFER| functions for manipulating the chain.)
 OPENSSL_EXPORT const STACK_OF(CRYPTO_BUFFER) *SSL_CTX_get0_chain(
     const SSL_CTX *ctx);
 
 // SSL_get0_chain returns the list of |CRYPTO_BUFFER|s that were set by
 // |SSL_set_chain_and_key|, unless they have been discarded. Reference counts
 // are not incremented by this call. The return value may be |NULL| if no chain
 // has been set.
 //
 // (Note: if a chain was configured by non-|CRYPTO_BUFFER|-based functions then
 // the return value is undefined and, even if not NULL, the stack itself may
 // contain nullptrs. Thus you shouldn't mix this function with
 // non-|CRYPTO_BUFFER| functions for manipulating the chain.)
 //
 // This function may return nullptr if a handshake has completed even if
 // |SSL_set_chain_and_key| was previously called, since the configuration
 // containing the certificates is typically cleared after handshake completion.
 OPENSSL_EXPORT const STACK_OF(CRYPTO_BUFFER) *SSL_get0_chain(const SSL *ssl);
 
 // SSL_CTX_use_RSAPrivateKey sets |ctx|'s private key to |rsa|. It returns one
 // on success and zero on failure.
 OPENSSL_EXPORT int SSL_CTX_use_RSAPrivateKey(SSL_CTX *ctx, RSA *rsa);
 
 // SSL_use_RSAPrivateKey sets |ctx|'s private key to |rsa|. It returns one on
 // success and zero on failure.
 OPENSSL_EXPORT int SSL_use_RSAPrivateKey(SSL *ssl, RSA *rsa);
 
 // The following functions configure certificates or private keys but take as
 // input DER-encoded structures. They return one on success and zero on
 // failure.
 
 OPENSSL_EXPORT int SSL_CTX_use_certificate_ASN1(SSL_CTX *ctx, size_t der_len,
                                                 const uint8_t *der);
 OPENSSL_EXPORT int SSL_use_certificate_ASN1(SSL *ssl, const uint8_t *der,
                                             size_t der_len);
 
 OPENSSL_EXPORT int SSL_CTX_use_PrivateKey_ASN1(int pk, SSL_CTX *ctx,
                                                const uint8_t *der,
                                                size_t der_len);
 OPENSSL_EXPORT int SSL_use_PrivateKey_ASN1(int type, SSL *ssl,
                                            const uint8_t *der, size_t der_len);
 
 OPENSSL_EXPORT int SSL_CTX_use_RSAPrivateKey_ASN1(SSL_CTX *ctx,
                                                   const uint8_t *der,
                                                   size_t der_len);
 OPENSSL_EXPORT int SSL_use_RSAPrivateKey_ASN1(SSL *ssl, const uint8_t *der,
                                               size_t der_len);
 
 // The following functions configure certificates or private keys but take as
 // input files to read from. They return one on success and zero on failure. The
 // |type| parameter is one of the |SSL_FILETYPE_*| values and determines whether
 // the file's contents are read as PEM or DER.
 
 #define SSL_FILETYPE_PEM 1
 #define SSL_FILETYPE_ASN1 2
 
 OPENSSL_EXPORT int SSL_CTX_use_RSAPrivateKey_file(SSL_CTX *ctx,
                                                   const char *file, int type);
 OPENSSL_EXPORT int SSL_use_RSAPrivateKey_file(SSL *ssl, const char *file,
                                               int type);
 
 OPENSSL_EXPORT int SSL_CTX_use_certificate_file(SSL_CTX *ctx, const char *file,
                                                 int type);
 OPENSSL_EXPORT int SSL_use_certificate_file(SSL *ssl, const char *file,
                                             int type);
 
 OPENSSL_EXPORT int SSL_CTX_use_PrivateKey_file(SSL_CTX *ctx, const char *file,
                                                int type);
 OPENSSL_EXPORT int SSL_use_PrivateKey_file(SSL *ssl, const char *file,
                                            int type);
 
 // SSL_CTX_use_certificate_chain_file configures certificates for |ctx|. It
 // reads the contents of |file| as a PEM-encoded leaf certificate followed
 // optionally by the certificate chain to send to the peer. It returns one on
 // success and zero on failure.
 //
 // WARNING: If the input contains "TRUSTED CERTIFICATE" PEM blocks, this
 // function parses auxiliary properties as in |d2i_X509_AUX|. Passing untrusted
 // input to this function allows an attacker to influence those properties. See
 // |d2i_X509_AUX| for details.
 OPENSSL_EXPORT int SSL_CTX_use_certificate_chain_file(SSL_CTX *ctx,
                                                       const char *file);
 
 // SSL_CTX_set_default_passwd_cb sets the password callback for PEM-based
 // convenience functions called on |ctx|.
 OPENSSL_EXPORT void SSL_CTX_set_default_passwd_cb(SSL_CTX *ctx,
                                                   pem_password_cb *cb);
 
 // SSL_CTX_get_default_passwd_cb returns the callback set by
 // |SSL_CTX_set_default_passwd_cb|.
 OPENSSL_EXPORT pem_password_cb *SSL_CTX_get_default_passwd_cb(
     const SSL_CTX *ctx);
 
 // SSL_CTX_set_default_passwd_cb_userdata sets the userdata parameter for
 // |ctx|'s password callback.
 OPENSSL_EXPORT void SSL_CTX_set_default_passwd_cb_userdata(SSL_CTX *ctx,
                                                            void *data);
 
 // SSL_CTX_get_default_passwd_cb_userdata returns the userdata parameter set by
 // |SSL_CTX_set_default_passwd_cb_userdata|.
 OPENSSL_EXPORT void *SSL_CTX_get_default_passwd_cb_userdata(const SSL_CTX *ctx);
 
 
 // Custom private keys.
 
 enum ssl_private_key_result_t BORINGSSL_ENUM_INT {
   ssl_private_key_success,
   ssl_private_key_retry,
   ssl_private_key_failure,
 };
 
 // ssl_private_key_method_st (aka |SSL_PRIVATE_KEY_METHOD|) describes private
 // key hooks. This is used to off-load signing operations to a custom,
 // potentially asynchronous, backend. Metadata about the key such as the type
 // and size are parsed out of the certificate.
 struct ssl_private_key_method_st {
   // sign signs the message |in| in using the specified signature algorithm. On
   // success, it returns |ssl_private_key_success| and writes at most |max_out|
   // bytes of signature data to |out| and sets |*out_len| to the number of bytes
   // written. On failure, it returns |ssl_private_key_failure|. If the operation
   // has not completed, it returns |ssl_private_key_retry|. |sign| should
   // arrange for the high-level operation on |ssl| to be retried when the
   // operation is completed. This will result in a call to |complete|.
   //
   // |signature_algorithm| is one of the |SSL_SIGN_*| values, as defined in TLS
   // 1.3. Note that, in TLS 1.2, ECDSA algorithms do not require that curve
   // sizes match hash sizes, so the curve portion of |SSL_SIGN_ECDSA_*| values
   // must be ignored. BoringSSL will internally handle the curve matching logic
   // where appropriate.
   //
   // It is an error to call |sign| while another private key operation is in
   // progress on |ssl|.
   enum ssl_private_key_result_t (*sign)(SSL *ssl, uint8_t *out, size_t *out_len,
                                         size_t max_out,
                                         uint16_t signature_algorithm,
                                         const uint8_t *in, size_t in_len);
 
   // decrypt decrypts |in_len| bytes of encrypted data from |in|. On success it
   // returns |ssl_private_key_success|, writes at most |max_out| bytes of
   // decrypted data to |out| and sets |*out_len| to the actual number of bytes
   // written. On failure it returns |ssl_private_key_failure|. If the operation
   // has not completed, it returns |ssl_private_key_retry|. The caller should
   // arrange for the high-level operation on |ssl| to be retried when the
   // operation is completed, which will result in a call to |complete|. This
   // function only works with RSA keys and should perform a raw RSA decryption
   // operation with no padding.
   //
   // It is an error to call |decrypt| while another private key operation is in
   // progress on |ssl|.
   enum ssl_private_key_result_t (*decrypt)(SSL *ssl, uint8_t *out,
                                            size_t *out_len, size_t max_out,
                                            const uint8_t *in, size_t in_len);
 
   // complete completes a pending operation. If the operation has completed, it
   // returns |ssl_private_key_success| and writes the result to |out| as in
   // |sign|. Otherwise, it returns |ssl_private_key_failure| on failure and
   // |ssl_private_key_retry| if the operation is still in progress.
   //
   // |complete| may be called arbitrarily many times before completion, but it
   // is an error to call |complete| if there is no pending operation in progress
   // on |ssl|.
   enum ssl_private_key_result_t (*complete)(SSL *ssl, uint8_t *out,
                                             size_t *out_len, size_t max_out);
 };
 
 // SSL_set_private_key_method configures a custom private key on |ssl|.
 // |key_method| must remain valid for the lifetime of |ssl|.
 //
 // If using an RSA or ECDSA key, callers should configure signing capabilities
 // with |SSL_set_signing_algorithm_prefs|. Otherwise, BoringSSL may select a
 // signature algorithm that |key_method| does not support.
 OPENSSL_EXPORT void SSL_set_private_key_method(
     SSL *ssl, const SSL_PRIVATE_KEY_METHOD *key_method);
 
 // SSL_CTX_set_private_key_method configures a custom private key on |ctx|.
 // |key_method| must remain valid for the lifetime of |ctx|.
 //
 // If using an RSA or ECDSA key, callers should configure signing capabilities
 // with |SSL_CTX_set_signing_algorithm_prefs|. Otherwise, BoringSSL may select a
 // signature algorithm that |key_method| does not support.
 OPENSSL_EXPORT void SSL_CTX_set_private_key_method(
     SSL_CTX *ctx, const SSL_PRIVATE_KEY_METHOD *key_method);
 
 // SSL_CREDENTIAL_set_private_key_method configures a custom private key on
 // |cred|. |key_method| must remain valid for the lifetime of |cred|. It returns
 // one on success and zero if |cred| does not use private keys.
 //
 // If using an RSA or ECDSA key, callers should configure signing capabilities
 // with |SSL_CREDENTIAL_set1_signing_algorithm_prefs|. Otherwise, BoringSSL may
 // select a signature algorithm that |key_method| does not support. This is not
 // necessary for delegated credentials (see |SSL_CREDENTIAL_new_delegated|)
 // because delegated credentials only support a single signature algorithm.
 //
 // Functions in |key_method| will be passed an |SSL| object, but not |cred|
 // directly. Use |SSL_get0_selected_credential| to determine the selected
 // credential. From there, |SSL_CREDENTIAL_get_ex_data| can be used to look up
 // credential-specific state, such as a handle to the private key.
 OPENSSL_EXPORT int SSL_CREDENTIAL_set_private_key_method(
     SSL_CREDENTIAL *cred, const SSL_PRIVATE_KEY_METHOD *key_method);
 
 // SSL_can_release_private_key returns one if |ssl| will no longer call into the
 // private key and zero otherwise. If the function returns one, the caller can
 // release state associated with the private key.
 //
 // NOTE: This function assumes the caller does not use |SSL_clear| to reuse
 // |ssl| for a second connection. If |SSL_clear| is used, BoringSSL may still
 // use the private key on the second connection.
 OPENSSL_EXPORT int SSL_can_release_private_key(const SSL *ssl);
 
 
 // Cipher suites.
 //
 // |SSL_CIPHER| objects represent cipher suites.
 
 DEFINE_CONST_STACK_OF(SSL_CIPHER)
 
 // SSL_get_cipher_by_value returns the structure representing a TLS cipher
 // suite based on its assigned number, or NULL if unknown. See
 // https://www.iana.org/assignments/tls-parameters/tls-parameters.xhtml#tls-parameters-4.
 OPENSSL_EXPORT const SSL_CIPHER *SSL_get_cipher_by_value(uint16_t value);
 
 // SSL_CIPHER_get_id returns |cipher|'s non-IANA id. This is not its
 // IANA-assigned number, which is called the "value" here, although it may be
 // cast to a |uint16_t| to get it.
 OPENSSL_EXPORT uint32_t SSL_CIPHER_get_id(const SSL_CIPHER *cipher);
 
 // SSL_CIPHER_get_protocol_id returns |cipher|'s IANA-assigned number.
 OPENSSL_EXPORT uint16_t SSL_CIPHER_get_protocol_id(const SSL_CIPHER *cipher);
 
 // SSL_CIPHER_is_aead returns one if |cipher| uses an AEAD cipher.
 OPENSSL_EXPORT int SSL_CIPHER_is_aead(const SSL_CIPHER *cipher);
 
 // SSL_CIPHER_is_block_cipher returns one if |cipher| is a block cipher.
 OPENSSL_EXPORT int SSL_CIPHER_is_block_cipher(const SSL_CIPHER *cipher);
 
 // SSL_CIPHER_get_cipher_nid returns the NID for |cipher|'s bulk
 // cipher. Possible values are |NID_aes_128_gcm|, |NID_aes_256_gcm|,
 // |NID_chacha20_poly1305|, |NID_aes_128_cbc|, |NID_aes_256_cbc|, and
 // |NID_des_ede3_cbc|.
 OPENSSL_EXPORT int SSL_CIPHER_get_cipher_nid(const SSL_CIPHER *cipher);
 
 // SSL_CIPHER_get_digest_nid returns the NID for |cipher|'s HMAC if it is a
 // legacy cipher suite. For modern AEAD-based ciphers (see
 // |SSL_CIPHER_is_aead|), it returns |NID_undef|.
 //
 // Note this function only returns the legacy HMAC digest, not the PRF hash.
 OPENSSL_EXPORT int SSL_CIPHER_get_digest_nid(const SSL_CIPHER *cipher);
 
 // SSL_CIPHER_get_kx_nid returns the NID for |cipher|'s key exchange. This may
 // be |NID_kx_rsa|, |NID_kx_ecdhe|, or |NID_kx_psk| for TLS 1.2. In TLS 1.3,
 // cipher suites do not specify the key exchange, so this function returns
 // |NID_kx_any|.
 OPENSSL_EXPORT int SSL_CIPHER_get_kx_nid(const SSL_CIPHER *cipher);
 
 // SSL_CIPHER_get_auth_nid returns the NID for |cipher|'s authentication
 // type. This may be |NID_auth_rsa|, |NID_auth_ecdsa|, or |NID_auth_psk| for TLS
 // 1.2. In TLS 1.3, cipher suites do not specify authentication, so this
 // function returns |NID_auth_any|.
 OPENSSL_EXPORT int SSL_CIPHER_get_auth_nid(const SSL_CIPHER *cipher);
 
 // SSL_CIPHER_get_handshake_digest returns |cipher|'s PRF hash. If |cipher|
 // is a pre-TLS-1.2 cipher, it returns |EVP_md5_sha1| but note these ciphers use
 // SHA-256 in TLS 1.2. Other return values may be treated uniformly in all
 // applicable versions.
 OPENSSL_EXPORT const EVP_MD *SSL_CIPHER_get_handshake_digest(
     const SSL_CIPHER *cipher);
 
 // SSL_CIPHER_get_prf_nid behaves like |SSL_CIPHER_get_handshake_digest| but
 // returns the NID constant. Use |SSL_CIPHER_get_handshake_digest| instead.
 OPENSSL_EXPORT int SSL_CIPHER_get_prf_nid(const SSL_CIPHER *cipher);
 
 // SSL_CIPHER_get_min_version returns the minimum protocol version required
 // for |cipher|.
 OPENSSL_EXPORT uint16_t SSL_CIPHER_get_min_version(const SSL_CIPHER *cipher);
 
 // SSL_CIPHER_get_max_version returns the maximum protocol version that
 // supports |cipher|.
 OPENSSL_EXPORT uint16_t SSL_CIPHER_get_max_version(const SSL_CIPHER *cipher);
 
 // SSL_CIPHER_standard_name returns the standard IETF name for |cipher|. For
 // example, "TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256".
 OPENSSL_EXPORT const char *SSL_CIPHER_standard_name(const SSL_CIPHER *cipher);
 
 // SSL_CIPHER_get_name returns the OpenSSL name of |cipher|. For example,
 // "ECDHE-RSA-AES128-GCM-SHA256". Callers are recommended to use
 // |SSL_CIPHER_standard_name| instead.
 OPENSSL_EXPORT const char *SSL_CIPHER_get_name(const SSL_CIPHER *cipher);
 
 // SSL_CIPHER_get_kx_name returns a string that describes the key-exchange
 // method used by |cipher|. For example, "ECDHE_ECDSA". TLS 1.3 AEAD-only
 // ciphers return the string "GENERIC".
 OPENSSL_EXPORT const char *SSL_CIPHER_get_kx_name(const SSL_CIPHER *cipher);
 
 // SSL_CIPHER_get_bits returns the strength, in bits, of |cipher|. If
 // |out_alg_bits| is not NULL, it writes the number of bits consumed by the
 // symmetric algorithm to |*out_alg_bits|.
 OPENSSL_EXPORT int SSL_CIPHER_get_bits(const SSL_CIPHER *cipher,
                                        int *out_alg_bits);
 
 // SSL_get_all_cipher_names outputs a list of possible strings
 // |SSL_CIPHER_get_name| may return in this version of BoringSSL. It writes at
 // most |max_out| entries to |out| and returns the total number it would have
 // written, if |max_out| had been large enough. |max_out| may be initially set
 // to zero to size the output.
 //
 // This function is only intended to help initialize tables in callers that want
 // possible strings pre-declared. This list would not be suitable to set a list
 // of supported features. It is in no particular order, and may contain
 // placeholder, experimental, or deprecated values that do not apply to every
 // caller. Future versions of BoringSSL may also return strings not in this
 // list, so this does not apply if, say, sending strings across services.
 OPENSSL_EXPORT size_t SSL_get_all_cipher_names(const char **out,
                                                size_t max_out);
 
 
 // SSL_get_all_standard_cipher_names outputs a list of possible strings
 // |SSL_CIPHER_standard_name| may return in this version of BoringSSL. It writes
 // at most |max_out| entries to |out| and returns the total number it would have
 // written, if |max_out| had been large enough. |max_out| may be initially set
 // to zero to size the output.
 //
 // This function is only intended to help initialize tables in callers that want
 // possible strings pre-declared. This list would not be suitable to set a list
 // of supported features. It is in no particular order, and may contain
 // placeholder, experimental, or deprecated values that do not apply to every
 // caller. Future versions of BoringSSL may also return strings not in this
 // list, so this does not apply if, say, sending strings across services.
 OPENSSL_EXPORT size_t SSL_get_all_standard_cipher_names(const char **out,
                                                         size_t max_out);
 
 
 // Cipher suite configuration.
 //
 // OpenSSL uses a mini-language to configure cipher suites. The language
 // maintains an ordered list of enabled ciphers, along with an ordered list of
 // disabled but available ciphers. Initially, all ciphers are disabled with a
 // default ordering. The cipher string is then interpreted as a sequence of
 // directives, separated by colons, each of which modifies this state.
 //
 // Most directives consist of a one character or empty opcode followed by a
 // selector which matches a subset of available ciphers.
 //
 // Available opcodes are:
 //
 // - The empty opcode enables and appends all matching disabled ciphers to the
 //   end of the enabled list. The newly appended ciphers are ordered relative to
 //   each other matching their order in the disabled list.
 //
 // - |-| disables all matching enabled ciphers and prepends them to the disabled
 //   list, with relative order from the enabled list preserved. This means the
 //   most recently disabled ciphers get highest preference relative to other
 //   disabled ciphers if re-enabled.
 //
 // - |+| moves all matching enabled ciphers to the end of the enabled list, with
 //   relative order preserved.
 //
 // - |!| deletes all matching ciphers, enabled or not, from either list. Deleted
 //   ciphers will not matched by future operations.
 //
 // A selector may be a specific cipher (using either the standard or OpenSSL
 // name for the cipher) or one or more rules separated by |+|. The final
 // selector matches the intersection of each rule. For instance, |AESGCM+aECDSA|
 // matches ECDSA-authenticated AES-GCM ciphers.
 //
 // Available cipher rules are:
 //
 // - |ALL| matches all ciphers, except for deprecated ciphers which must be
 //   named explicitly.
 //
 // - |kRSA|, |kDHE|, |kECDHE|, and |kPSK| match ciphers using plain RSA, DHE,
 //   ECDHE, and plain PSK key exchanges, respectively. Note that ECDHE_PSK is
 //   matched by |kECDHE| and not |kPSK|.
 //
 // - |aRSA|, |aECDSA|, and |aPSK| match ciphers authenticated by RSA, ECDSA, and
 //   a pre-shared key, respectively.
 //
 // - |RSA|, |DHE|, |ECDHE|, |PSK|, |ECDSA|, and |PSK| are aliases for the
 //   corresponding |k*| or |a*| cipher rule. |RSA| is an alias for |kRSA|, not
 //   |aRSA|.
 //
 // - |3DES|, |AES128|, |AES256|, |AES|, |AESGCM|, |CHACHA20| match ciphers
 //   whose bulk cipher use the corresponding encryption scheme. Note that
 //   |AES|, |AES128|, and |AES256| match both CBC and GCM ciphers.
 //
 // - |SHA1|, and its alias |SHA|, match legacy cipher suites using HMAC-SHA1.
 //
 // Deprecated cipher rules:
 //
 // - |kEDH|, |EDH|, |kEECDH|, and |EECDH| are legacy aliases for |kDHE|, |DHE|,
 //   |kECDHE|, and |ECDHE|, respectively.
 //
 // - |HIGH| is an alias for |ALL|.
 //
 // - |FIPS| is an alias for |HIGH|.
 //
 // - |SSLv3| and |TLSv1| match ciphers available in TLS 1.1 or earlier.
 //   |TLSv1_2| matches ciphers new in TLS 1.2. This is confusing and should not
 //   be used.
 //
 // Unknown rules are silently ignored by legacy APIs, and rejected by APIs with
 // "strict" in the name, which should be preferred. Cipher lists can be long
 // and it's easy to commit typos. Strict functions will also reject the use of
 // spaces, semi-colons and commas as alternative separators.
 //
 // The special |@STRENGTH| directive will sort all enabled ciphers by strength.
 //
 // The |DEFAULT| directive, when appearing at the front of the string, expands
 // to the default ordering of available ciphers.
 //
 // If configuring a server, one may also configure equal-preference groups to
 // partially respect the client's preferences when
 // |SSL_OP_CIPHER_SERVER_PREFERENCE| is enabled. Ciphers in an equal-preference
 // group have equal priority and use the client order. This may be used to
 // enforce that AEADs are preferred but select AES-GCM vs. ChaCha20-Poly1305
 // based on client preferences. An equal-preference is specified with square
 // brackets, combining multiple selectors separated by |. For example:
 //
 //   [TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305_SHA256|TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256]
 //
 // Once an equal-preference group is used, future directives must be
 // opcode-less. Inside an equal-preference group, spaces are not allowed.
 //
 // TLS 1.3 ciphers do not participate in this mechanism and instead have a
 // built-in preference order. Functions to set cipher lists do not affect TLS
 // 1.3, and functions to query the cipher list do not include TLS 1.3 ciphers.
 
 // SSL_DEFAULT_CIPHER_LIST is the default cipher suite configuration. It is
 // substituted when a cipher string starts with 'DEFAULT'.
 #define SSL_DEFAULT_CIPHER_LIST "ALL"
 
 // SSL_CTX_set_strict_cipher_list configures the cipher list for |ctx|,
 // evaluating |str| as a cipher string and returning error if |str| contains
 // anything meaningless. It returns one on success and zero on failure.
 OPENSSL_EXPORT int SSL_CTX_set_strict_cipher_list(SSL_CTX *ctx,
                                                   const char *str);
 
 // SSL_CTX_set_cipher_list configures the cipher list for |ctx|, evaluating
 // |str| as a cipher string. It returns one on success and zero on failure.
 //
 // Prefer to use |SSL_CTX_set_strict_cipher_list|. This function tolerates
 // garbage inputs, unless an empty cipher list results.
 OPENSSL_EXPORT int SSL_CTX_set_cipher_list(SSL_CTX *ctx, const char *str);
 
 // SSL_set_strict_cipher_list configures the cipher list for |ssl|, evaluating
 // |str| as a cipher string and returning error if |str| contains anything
 // meaningless. It returns one on success and zero on failure.
 OPENSSL_EXPORT int SSL_set_strict_cipher_list(SSL *ssl, const char *str);
 
 // SSL_set_cipher_list configures the cipher list for |ssl|, evaluating |str| as
 // a cipher string. It returns one on success and zero on failure.
 //
 // Prefer to use |SSL_set_strict_cipher_list|. This function tolerates garbage
 // inputs, unless an empty cipher list results.
 OPENSSL_EXPORT int SSL_set_cipher_list(SSL *ssl, const char *str);
 
 // SSL_CTX_get_ciphers returns the cipher list for |ctx|, in order of
 // preference.
 OPENSSL_EXPORT STACK_OF(SSL_CIPHER) *SSL_CTX_get_ciphers(const SSL_CTX *ctx);
 
 // SSL_CTX_cipher_in_group returns one if the |i|th cipher (see
 // |SSL_CTX_get_ciphers|) is in the same equipreference group as the one
 // following it and zero otherwise.
 OPENSSL_EXPORT int SSL_CTX_cipher_in_group(const SSL_CTX *ctx, size_t i);
 
 // SSL_get_ciphers returns the cipher list for |ssl|, in order of preference.
 OPENSSL_EXPORT STACK_OF(SSL_CIPHER) *SSL_get_ciphers(const SSL *ssl);
 
 
 // Connection information.
 
 // SSL_is_init_finished returns one if |ssl| has completed its initial handshake
 // and has no pending handshake. It returns zero otherwise.
 OPENSSL_EXPORT int SSL_is_init_finished(const SSL *ssl);
 
 // SSL_in_init returns one if |ssl| has a pending handshake and zero
 // otherwise.
 OPENSSL_EXPORT int SSL_in_init(const SSL *ssl);
 
 // SSL_in_false_start returns one if |ssl| has a pending handshake that is in
 // False Start. |SSL_write| may be called at this point without waiting for the
 // peer, but |SSL_read| will complete the handshake before accepting application
 // data.
 //
 // See also |SSL_MODE_ENABLE_FALSE_START|.
 OPENSSL_EXPORT int SSL_in_false_start(const SSL *ssl);
 
 // SSL_get_peer_certificate returns the peer's leaf certificate or NULL if the
 // peer did not use certificates. The caller must call |X509_free| on the
 // result to release it.
 OPENSSL_EXPORT X509 *SSL_get_peer_certificate(const SSL *ssl);
 
 // SSL_get_peer_cert_chain returns the peer's certificate chain or NULL if
 // unavailable or the peer did not use certificates. This is the unverified list
 // of certificates as sent by the peer, not the final chain built during
 // verification. The caller does not take ownership of the result.
 //
 // WARNING: This function behaves differently between client and server. If
 // |ssl| is a server, the returned chain does not include the leaf certificate.
 // If a client, it does.
 OPENSSL_EXPORT STACK_OF(X509) *SSL_get_peer_cert_chain(const SSL *ssl);
 
 // SSL_get_peer_full_cert_chain returns the peer's certificate chain, or NULL if
 // unavailable or the peer did not use certificates. This is the unverified list
 // of certificates as sent by the peer, not the final chain built during
 // verification. The caller does not take ownership of the result.
 //
 // This is the same as |SSL_get_peer_cert_chain| except that this function
 // always returns the full chain, i.e. the first element of the return value
 // (if any) will be the leaf certificate. In constrast,
 // |SSL_get_peer_cert_chain| returns only the intermediate certificates if the
 // |ssl| is a server.
 OPENSSL_EXPORT STACK_OF(X509) *SSL_get_peer_full_cert_chain(const SSL *ssl);
 
 // SSL_get0_peer_certificates returns the peer's certificate chain, or NULL if
 // unavailable or the peer did not use certificates. This is the unverified list
 // of certificates as sent by the peer, not the final chain built during
 // verification. The caller does not take ownership of the result.
 //
 // This is the |CRYPTO_BUFFER| variant of |SSL_get_peer_full_cert_chain|.
 OPENSSL_EXPORT const STACK_OF(CRYPTO_BUFFER) *SSL_get0_peer_certificates(
     const SSL *ssl);
 
 // SSL_get0_signed_cert_timestamp_list sets |*out| and |*out_len| to point to
 // |*out_len| bytes of SCT information from the server. This is only valid if
 // |ssl| is a client. The SCT information is a SignedCertificateTimestampList
 // (including the two leading length bytes).
 // See https://tools.ietf.org/html/rfc6962#section-3.3
 // If no SCT was received then |*out_len| will be zero on return.
 //
 // WARNING: the returned data is not guaranteed to be well formed.
 OPENSSL_EXPORT void SSL_get0_signed_cert_timestamp_list(const SSL *ssl,
                                                         const uint8_t **out,
                                                         size_t *out_len);
 
 // SSL_get0_ocsp_response sets |*out| and |*out_len| to point to |*out_len|
 // bytes of an OCSP response from the server. This is the DER encoding of an
 // OCSPResponse type as defined in RFC 2560.
 //
 // WARNING: the returned data is not guaranteed to be well formed.
 OPENSSL_EXPORT void SSL_get0_ocsp_response(const SSL *ssl, const uint8_t **out,
                                            size_t *out_len);
 
 // SSL_get_tls_unique writes at most |max_out| bytes of the tls-unique value
 // for |ssl| to |out| and sets |*out_len| to the number of bytes written. It
 // returns one on success or zero on error. In general |max_out| should be at
 // least 12.
 //
 // This function will always fail if the initial handshake has not completed.
 // The tls-unique value will change after a renegotiation but, since
 // renegotiations can be initiated by the server at any point, the higher-level
 // protocol must either leave them disabled or define states in which the
 // tls-unique value can be read.
 //
 // The tls-unique value is defined by
 // https://tools.ietf.org/html/rfc5929#section-3.1. Due to a weakness in the
 // TLS protocol, tls-unique is broken for resumed connections unless the
 // Extended Master Secret extension is negotiated. Thus this function will
 // return zero if |ssl| performed session resumption unless EMS was used when
 // negotiating the original session.
 OPENSSL_EXPORT int SSL_get_tls_unique(const SSL *ssl, uint8_t *out,
                                       size_t *out_len, size_t max_out);
 
 // SSL_get_extms_support returns one if the Extended Master Secret extension or
 // TLS 1.3 was negotiated. Otherwise, it returns zero.
 OPENSSL_EXPORT int SSL_get_extms_support(const SSL *ssl);
 
 // SSL_get_current_cipher returns cipher suite used by |ssl|, or NULL if it has
 // not been negotiated yet.
 OPENSSL_EXPORT const SSL_CIPHER *SSL_get_current_cipher(const SSL *ssl);
 
 // SSL_session_reused returns one if |ssl| performed an abbreviated handshake
 // and zero otherwise.
 //
 // TODO(davidben): Hammer down the semantics of this API while a handshake,
 // initial or renego, is in progress.
 OPENSSL_EXPORT int SSL_session_reused(const SSL *ssl);
 
 // SSL_get_secure_renegotiation_support returns one if the peer supports secure
 // renegotiation (RFC 5746) or TLS 1.3. Otherwise, it returns zero.
 OPENSSL_EXPORT int SSL_get_secure_renegotiation_support(const SSL *ssl);
 
 // SSL_export_keying_material exports a connection-specific secret from |ssl|,
 // as specified in RFC 5705. It writes |out_len| bytes to |out| given a label
 // and optional context. If |use_context| is zero, the |context| parameter is
 // ignored.
 //
 // To derive the same value, both sides of a connection must use the same output
 // length, label, and context. In TLS 1.2 and earlier, using a zero-length
 // context and using no context would give different output. In TLS 1.3 and
 // later, the output length impacts the derivation, so a truncated longer export
 // will not match a shorter export.
 //
 // It returns one on success and zero otherwise.
 OPENSSL_EXPORT int SSL_export_keying_material(const SSL *ssl, uint8_t *out,
                                               size_t out_len, const char *label,
                                               size_t label_len,
                                               const uint8_t *context,
                                               size_t context_len,
                                               int use_context);
 
 
 // Sessions.
 //
 // An |SSL_SESSION| represents an SSL session that may be resumed in an
 // abbreviated handshake. It is reference-counted and immutable. Once
 // established, an |SSL_SESSION| may be shared by multiple |SSL| objects on
 // different threads and must not be modified.
 //
 // Note the TLS notion of "session" is not suitable for application-level
 // session state. It is an optional caching mechanism for the handshake. Not all
 // connections within an application-level session will reuse TLS sessions. TLS
 // sessions may be dropped by the client or ignored by the server at any time.
 
 DECLARE_PEM_rw(SSL_SESSION, SSL_SESSION)
 
 // SSL_SESSION_new returns a newly-allocated blank |SSL_SESSION| or NULL on
 // error. This may be useful when writing tests but should otherwise not be
 // used.
 OPENSSL_EXPORT SSL_SESSION *SSL_SESSION_new(const SSL_CTX *ctx);
 
 // SSL_SESSION_up_ref increments the reference count of |session| and returns
 // one.
 OPENSSL_EXPORT int SSL_SESSION_up_ref(SSL_SESSION *session);
 
 // SSL_SESSION_free decrements the reference count of |session|. If it reaches
 // zero, all data referenced by |session| and |session| itself are released.
 OPENSSL_EXPORT void SSL_SESSION_free(SSL_SESSION *session);
 
 // SSL_SESSION_to_bytes serializes |in| into a newly allocated buffer and sets
 // |*out_data| to that buffer and |*out_len| to its length. The caller takes
 // ownership of the buffer and must call |OPENSSL_free| when done. It returns
 // one on success and zero on error.
 OPENSSL_EXPORT int SSL_SESSION_to_bytes(const SSL_SESSION *in,
                                         uint8_t **out_data, size_t *out_len);
 
 // SSL_SESSION_to_bytes_for_ticket serializes |in|, but excludes the session
 // identification information, namely the session ID and ticket.
 OPENSSL_EXPORT int SSL_SESSION_to_bytes_for_ticket(const SSL_SESSION *in,
                                                    uint8_t **out_data,
                                                    size_t *out_len);
 
 // SSL_SESSION_from_bytes parses |in_len| bytes from |in| as an SSL_SESSION. It
 // returns a newly-allocated |SSL_SESSION| on success or NULL on error.
 OPENSSL_EXPORT SSL_SESSION *SSL_SESSION_from_bytes(const uint8_t *in,
                                                    size_t in_len,
                                                    const SSL_CTX *ctx);
 
 // SSL_SESSION_get_version returns a string describing the TLS or DTLS version
 // |session| was established at. For example, "TLSv1.2" or "DTLSv1".
 OPENSSL_EXPORT const char *SSL_SESSION_get_version(const SSL_SESSION *session);
 
 // SSL_SESSION_get_protocol_version returns the TLS or DTLS version |session|
 // was established at.
 OPENSSL_EXPORT uint16_t
 SSL_SESSION_get_protocol_version(const SSL_SESSION *session);
 
 // SSL_SESSION_set_protocol_version sets |session|'s TLS or DTLS version to
 // |version|. This may be useful when writing tests but should otherwise not be
 // used. It returns one on success and zero on error.
 OPENSSL_EXPORT int SSL_SESSION_set_protocol_version(SSL_SESSION *session,
                                                     uint16_t version);
 
 // SSL_MAX_SSL_SESSION_ID_LENGTH is the maximum length of an SSL session ID.
 #define SSL_MAX_SSL_SESSION_ID_LENGTH 32
 
 // SSL_SESSION_get_id returns a pointer to a buffer containing |session|'s
 // session ID and sets |*out_len| to its length.
 //
 // This function should only be used for implementing a TLS session cache. TLS
 // sessions are not suitable for application-level session state, and a session
 // ID is an implementation detail of the TLS resumption handshake mechanism. Not
 // all resumption flows use session IDs, and not all connections within an
 // application-level session will reuse TLS sessions.
 //
 // To determine if resumption occurred, use |SSL_session_reused| instead.
 // Comparing session IDs will not give the right result in all cases.
 //
 // As a workaround for some broken applications, BoringSSL sometimes synthesizes
 // arbitrary session IDs for non-ID-based sessions. This behavior may be
 // removed in the future.
 OPENSSL_EXPORT const uint8_t *SSL_SESSION_get_id(const SSL_SESSION *session,
                                                  unsigned *out_len);
 
 // SSL_SESSION_set1_id sets |session|'s session ID to |sid|, It returns one on
 // success and zero on error. This function may be useful in writing tests but
 // otherwise should not be used.
 OPENSSL_EXPORT int SSL_SESSION_set1_id(SSL_SESSION *session, const uint8_t *sid,
                                        size_t sid_len);
 
 // SSL_SESSION_get_time returns the time at which |session| was established in
 // seconds since the UNIX epoch.
 OPENSSL_EXPORT uint64_t SSL_SESSION_get_time(const SSL_SESSION *session);
 
 // SSL_SESSION_get_timeout returns the lifetime of |session| in seconds.
 OPENSSL_EXPORT uint32_t SSL_SESSION_get_timeout(const SSL_SESSION *session);
 
 // SSL_SESSION_get0_peer returns the peer leaf certificate stored in
 // |session|.
 //
 // TODO(davidben): This should return a const X509 *.
 OPENSSL_EXPORT X509 *SSL_SESSION_get0_peer(const SSL_SESSION *session);
 
 // SSL_SESSION_get0_peer_certificates returns the peer certificate chain stored
 // in |session|, or NULL if the peer did not use certificates. This is the
 // unverified list of certificates as sent by the peer, not the final chain
 // built during verification. The caller does not take ownership of the result.
 OPENSSL_EXPORT const STACK_OF(CRYPTO_BUFFER) *
 SSL_SESSION_get0_peer_certificates(const SSL_SESSION *session);
 
 // SSL_SESSION_get0_signed_cert_timestamp_list sets |*out| and |*out_len| to
 // point to |*out_len| bytes of SCT information stored in |session|. This is
 // only valid for client sessions. The SCT information is a
 // SignedCertificateTimestampList (including the two leading length bytes). See
 // https://tools.ietf.org/html/rfc6962#section-3.3 If no SCT was received then
 // |*out_len| will be zero on return.
 //
 // WARNING: the returned data is not guaranteed to be well formed.
 OPENSSL_EXPORT void SSL_SESSION_get0_signed_cert_timestamp_list(
     const SSL_SESSION *session, const uint8_t **out, size_t *out_len);
 
 // SSL_SESSION_get0_ocsp_response sets |*out| and |*out_len| to point to
 // |*out_len| bytes of an OCSP response from the server. This is the DER
 // encoding of an OCSPResponse type as defined in RFC 2560.
 //
 // WARNING: the returned data is not guaranteed to be well formed.
 OPENSSL_EXPORT void SSL_SESSION_get0_ocsp_response(const SSL_SESSION *session,
                                                    const uint8_t **out,
                                                    size_t *out_len);
 
 // SSL_MAX_MASTER_KEY_LENGTH is the maximum length of a master secret.
 #define SSL_MAX_MASTER_KEY_LENGTH 48
 
 // SSL_SESSION_get_master_key writes up to |max_out| bytes of |session|'s secret
 // to |out| and returns the number of bytes written. If |max_out| is zero, it
 // returns the size of the secret.
 OPENSSL_EXPORT size_t SSL_SESSION_get_master_key(const SSL_SESSION *session,
                                                  uint8_t *out, size_t max_out);
 
 // SSL_SESSION_set_time sets |session|'s creation time to |time| and returns
 // |time|. This function may be useful in writing tests but otherwise should not
 // be used.
 OPENSSL_EXPORT uint64_t SSL_SESSION_set_time(SSL_SESSION *session,
                                              uint64_t time);
 
 // SSL_SESSION_set_timeout sets |session|'s timeout to |timeout| and returns
 // one. This function may be useful in writing tests but otherwise should not
 // be used.
 OPENSSL_EXPORT uint32_t SSL_SESSION_set_timeout(SSL_SESSION *session,
                                                 uint32_t timeout);
 
 // SSL_SESSION_get0_id_context returns a pointer to a buffer containing
 // |session|'s session ID context (see |SSL_CTX_set_session_id_context|) and
 // sets |*out_len| to its length.
 OPENSSL_EXPORT const uint8_t *SSL_SESSION_get0_id_context(
     const SSL_SESSION *session, unsigned *out_len);
 
 // SSL_SESSION_set1_id_context sets |session|'s session ID context (see
 // |SSL_CTX_set_session_id_context|) to |sid_ctx|. It returns one on success and
 // zero on error. This function may be useful in writing tests but otherwise
 // should not be used.
 OPENSSL_EXPORT int SSL_SESSION_set1_id_context(SSL_SESSION *session,
                                                const uint8_t *sid_ctx,
                                                size_t sid_ctx_len);
 
 // SSL_SESSION_should_be_single_use returns one if |session| should be
 // single-use (TLS 1.3 and later) and zero otherwise.
 //
 // If this function returns one, clients retain multiple sessions and use each
 // only once. This prevents passive observers from correlating connections with
 // tickets. See RFC 8446, appendix C.4. If it returns zero, |session| cannot be
 // used without leaking a correlator.
 OPENSSL_EXPORT int SSL_SESSION_should_be_single_use(const SSL_SESSION *session);
 
 // SSL_SESSION_is_resumable returns one if |session| is complete and contains a
 // session ID or ticket. It returns zero otherwise. Note this function does not
 // ensure |session| will be resumed. It may be expired, dropped by the server,
 // or associated with incompatible parameters.
 OPENSSL_EXPORT int SSL_SESSION_is_resumable(const SSL_SESSION *session);
 
 // SSL_SESSION_has_ticket returns one if |session| has a ticket and zero
 // otherwise.
 OPENSSL_EXPORT int SSL_SESSION_has_ticket(const SSL_SESSION *session);
 
 // SSL_SESSION_get0_ticket sets |*out_ticket| and |*out_len| to |session|'s
 // ticket, or NULL and zero if it does not have one. |out_ticket| may be NULL
 // if only the ticket length is needed.
 OPENSSL_EXPORT void SSL_SESSION_get0_ticket(const SSL_SESSION *session,
                                             const uint8_t **out_ticket,
                                             size_t *out_len);
 
 // SSL_SESSION_set_ticket sets |session|'s ticket to |ticket|. It returns one on
 // success and zero on error. This function may be useful in writing tests but
 // otherwise should not be used.
 OPENSSL_EXPORT int SSL_SESSION_set_ticket(SSL_SESSION *session,
                                           const uint8_t *ticket,
                                           size_t ticket_len);
 
 // SSL_SESSION_get_ticket_lifetime_hint returns ticket lifetime hint of
 // |session| in seconds or zero if none was set.
 OPENSSL_EXPORT uint32_t
 SSL_SESSION_get_ticket_lifetime_hint(const SSL_SESSION *session);
 
 // SSL_SESSION_get0_cipher returns the cipher negotiated by the connection which
 // established |session|.
 //
 // Note that, in TLS 1.3, there is no guarantee that resumptions with |session|
 // will use that cipher. Prefer calling |SSL_get_current_cipher| on the |SSL|
 // instead.
 OPENSSL_EXPORT const SSL_CIPHER *SSL_SESSION_get0_cipher(
     const SSL_SESSION *session);
 
 // SSL_SESSION_has_peer_sha256 returns one if |session| has a SHA-256 hash of
 // the peer's certificate retained and zero if the peer did not present a
 // certificate or if this was not enabled when |session| was created. See also
 // |SSL_CTX_set_retain_only_sha256_of_client_certs|.
 OPENSSL_EXPORT int SSL_SESSION_has_peer_sha256(const SSL_SESSION *session);
 
 // SSL_SESSION_get0_peer_sha256 sets |*out_ptr| and |*out_len| to the SHA-256
 // hash of the peer certificate retained in |session|, or NULL and zero if it
 // does not have one. See also |SSL_CTX_set_retain_only_sha256_of_client_certs|.
 OPENSSL_EXPORT void SSL_SESSION_get0_peer_sha256(const SSL_SESSION *session,
                                                  const uint8_t **out_ptr,
                                                  size_t *out_len);
 
 // SSL_SESSION_is_resumable_across_names returns one if |session| may be resumed
 // with any identity in the server certificate and zero otherwise. See
 // draft-ietf-tls-cross-sni-resumption.
 OPENSSL_EXPORT int SSL_SESSION_is_resumable_across_names(
     const SSL_SESSION *session);
 
 
 // Session caching.
 //
 // Session caching allows connections to be established more efficiently based
 // on saved parameters from a previous connection, called a session (see
 // |SSL_SESSION|). The client offers a saved session, using an opaque identifier
 // from a previous connection. The server may accept the session, if it has the
 // parameters available. Otherwise, it will decline and continue with a full
 // handshake.
 //
 // This requires both the client and the server to retain session state. A
 // client does so with a stateful session cache. A server may do the same or, if
 // supported by both sides, statelessly using session tickets. For more
 // information on the latter, see the next section.
 //
 // For a server, the library implements a built-in internal session cache as an
 // in-memory hash table. Servers may also use |SSL_CTX_sess_set_get_cb| and
 // |SSL_CTX_sess_set_new_cb| to implement a custom external session cache. In
 // particular, this may be used to share a session cache between multiple
 // servers in a large deployment. An external cache may be used in addition to
 // or instead of the internal one. Use |SSL_CTX_set_session_cache_mode| to
 // toggle the internal cache.
 //
 // For a client, the only option is an external session cache. Clients may use
 // |SSL_CTX_sess_set_new_cb| to register a callback for when new sessions are
 // available. These may be cached and, in subsequent compatible connections,
 // configured with |SSL_set_session|.
 //
 // Note that offering or accepting a session short-circuits certificate
 // verification and most parameter negotiation. Resuming sessions across
 // different contexts may result in security failures and surprising
 // behavior. For a typical client, this means sessions for different hosts must
 // be cached under different keys. A client that connects to the same host with,
 // e.g., different cipher suite settings or client certificates should also use
 // separate session caches between those contexts. Servers should also partition
 // session caches between SNI hosts with |SSL_CTX_set_session_id_context|.
 //
 // Note also, in TLS 1.2 and earlier, offering sessions allows passive observers
 // to correlate different client connections. TLS 1.3 and later fix this,
 // provided clients use sessions at most once. Session caches are managed by the
 // caller in BoringSSL, so this must be implemented externally. See
 // |SSL_SESSION_should_be_single_use| for details.
 
 // SSL_SESS_CACHE_OFF disables all session caching.
 #define SSL_SESS_CACHE_OFF 0x0000
 
 // SSL_SESS_CACHE_CLIENT enables session caching for a client. The internal
 // cache is never used on a client, so this only enables the callbacks.
 #define SSL_SESS_CACHE_CLIENT 0x0001
 
 // SSL_SESS_CACHE_SERVER enables session caching for a server.
 #define SSL_SESS_CACHE_SERVER 0x0002
 
 // SSL_SESS_CACHE_BOTH enables session caching for both client and server.
 #define SSL_SESS_CACHE_BOTH (SSL_SESS_CACHE_CLIENT | SSL_SESS_CACHE_SERVER)
 
 // SSL_SESS_CACHE_NO_AUTO_CLEAR disables automatically calling
 // |SSL_CTX_flush_sessions| every 255 connections.
 #define SSL_SESS_CACHE_NO_AUTO_CLEAR 0x0080
 
 // SSL_SESS_CACHE_NO_INTERNAL_LOOKUP, on a server, disables looking up a session
 // from the internal session cache.
 #define SSL_SESS_CACHE_NO_INTERNAL_LOOKUP 0x0100
 
 // SSL_SESS_CACHE_NO_INTERNAL_STORE, on a server, disables storing sessions in
 // the internal session cache.
 #define SSL_SESS_CACHE_NO_INTERNAL_STORE 0x0200
 
 // SSL_SESS_CACHE_NO_INTERNAL, on a server, disables the internal session
 // cache.
 #define SSL_SESS_CACHE_NO_INTERNAL \
   (SSL_SESS_CACHE_NO_INTERNAL_LOOKUP | SSL_SESS_CACHE_NO_INTERNAL_STORE)
 
 // SSL_CTX_set_session_cache_mode sets the session cache mode bits for |ctx| to
 // |mode|. It returns the previous value.
 OPENSSL_EXPORT int SSL_CTX_set_session_cache_mode(SSL_CTX *ctx, int mode);
 
 // SSL_CTX_get_session_cache_mode returns the session cache mode bits for
 // |ctx|
 OPENSSL_EXPORT int SSL_CTX_get_session_cache_mode(const SSL_CTX *ctx);
 
 // SSL_set_session, for a client, configures |ssl| to offer to resume |session|
 // in the initial handshake and returns one. The caller retains ownership of
 // |session|. Note that configuring a session assumes the authentication in the
 // session is valid. For callers that wish to revalidate the session before
 // offering, see |SSL_SESSION_get0_peer_certificates|,
 // |SSL_SESSION_get0_signed_cert_timestamp_list|, and
 // |SSL_SESSION_get0_ocsp_response|.
 //
 // It is an error to call this function after the handshake has begun.
 OPENSSL_EXPORT int SSL_set_session(SSL *ssl, SSL_SESSION *session);
 
 // SSL_DEFAULT_SESSION_TIMEOUT is the default lifetime, in seconds, of a
 // session in TLS 1.2 or earlier. This is how long we are willing to use the
 // secret to encrypt traffic without fresh key material.
 #define SSL_DEFAULT_SESSION_TIMEOUT (2 * 60 * 60)
 
 // SSL_DEFAULT_SESSION_PSK_DHE_TIMEOUT is the default lifetime, in seconds, of a
 // session for TLS 1.3 psk_dhe_ke. This is how long we are willing to use the
 // secret as an authenticator.
 #define SSL_DEFAULT_SESSION_PSK_DHE_TIMEOUT (2 * 24 * 60 * 60)
 
 // SSL_DEFAULT_SESSION_AUTH_TIMEOUT is the default non-renewable lifetime, in
 // seconds, of a TLS 1.3 session. This is how long we are willing to trust the
 // signature in the initial handshake.
 #define SSL_DEFAULT_SESSION_AUTH_TIMEOUT (7 * 24 * 60 * 60)
 
 // SSL_CTX_set_timeout sets the lifetime, in seconds, of TLS 1.2 (or earlier)
 // sessions created in |ctx| to |timeout|.
 OPENSSL_EXPORT uint32_t SSL_CTX_set_timeout(SSL_CTX *ctx, uint32_t timeout);
 
 // SSL_CTX_set_session_psk_dhe_timeout sets the lifetime, in seconds, of TLS 1.3
 // sessions created in |ctx| to |timeout|.
 OPENSSL_EXPORT void SSL_CTX_set_session_psk_dhe_timeout(SSL_CTX *ctx,
                                                         uint32_t timeout);
 
 // SSL_CTX_get_timeout returns the lifetime, in seconds, of TLS 1.2 (or earlier)
 // sessions created in |ctx|.
 OPENSSL_EXPORT uint32_t SSL_CTX_get_timeout(const SSL_CTX *ctx);
 
 // SSL_MAX_SID_CTX_LENGTH is the maximum length of a session ID context.
 #define SSL_MAX_SID_CTX_LENGTH 32
 
 // SSL_CTX_set_session_id_context sets |ctx|'s session ID context to |sid_ctx|.
 // It returns one on success and zero on error. The session ID context is an
 // application-defined opaque byte string. A session will not be used in a
 // connection without a matching session ID context.
 //
 // For a server, if |SSL_VERIFY_PEER| is enabled, it is an error to not set a
 // session ID context.
 OPENSSL_EXPORT int SSL_CTX_set_session_id_context(SSL_CTX *ctx,
                                                   const uint8_t *sid_ctx,
                                                   size_t sid_ctx_len);
 
 // SSL_set_session_id_context sets |ssl|'s session ID context to |sid_ctx|. It
 // returns one on success and zero on error. See also
 // |SSL_CTX_set_session_id_context|.
 OPENSSL_EXPORT int SSL_set_session_id_context(SSL *ssl, const uint8_t *sid_ctx,
                                               size_t sid_ctx_len);
 
 // SSL_get0_session_id_context returns a pointer to |ssl|'s session ID context
 // and sets |*out_len| to its length.  It returns NULL on error.
 OPENSSL_EXPORT const uint8_t *SSL_get0_session_id_context(const SSL *ssl,
                                                           size_t *out_len);
 
 // SSL_SESSION_CACHE_MAX_SIZE_DEFAULT is the default maximum size of a session
 // cache.
 #define SSL_SESSION_CACHE_MAX_SIZE_DEFAULT (1024 * 20)
 
 // SSL_CTX_sess_set_cache_size sets the maximum size of |ctx|'s internal session
 // cache to |size|. It returns the previous value.
 OPENSSL_EXPORT unsigned long SSL_CTX_sess_set_cache_size(SSL_CTX *ctx,
                                                          unsigned long size);
 
 // SSL_CTX_sess_get_cache_size returns the maximum size of |ctx|'s internal
 // session cache.
 OPENSSL_EXPORT unsigned long SSL_CTX_sess_get_cache_size(const SSL_CTX *ctx);
 
 // SSL_CTX_sess_number returns the number of sessions in |ctx|'s internal
 // session cache.
 OPENSSL_EXPORT size_t SSL_CTX_sess_number(const SSL_CTX *ctx);
 
 // SSL_CTX_add_session inserts |session| into |ctx|'s internal session cache. It
 // returns one on success and zero on error or if |session| is already in the
 // cache. The caller retains its reference to |session|.
 OPENSSL_EXPORT int SSL_CTX_add_session(SSL_CTX *ctx, SSL_SESSION *session);
 
 // SSL_CTX_remove_session removes |session| from |ctx|'s internal session cache.
 // It returns one on success and zero if |session| was not in the cache.
 OPENSSL_EXPORT int SSL_CTX_remove_session(SSL_CTX *ctx, SSL_SESSION *session);
 
 // SSL_CTX_flush_sessions removes all sessions from |ctx| which have expired as
 // of time |time|. If |time| is zero, all sessions are removed.
 OPENSSL_EXPORT void SSL_CTX_flush_sessions(SSL_CTX *ctx, uint64_t time);
 
 // SSL_CTX_sess_set_new_cb sets the callback to be called when a new session is
 // established and ready to be cached. If the session cache is disabled (the
 // appropriate one of |SSL_SESS_CACHE_CLIENT| or |SSL_SESS_CACHE_SERVER| is
 // unset), the callback is not called.
 //
 // The callback is passed a reference to |session|. It returns one if it takes
 // ownership (and then calls |SSL_SESSION_free| when done) and zero otherwise. A
 // consumer which places |session| into an in-memory cache will likely return
 // one, with the cache calling |SSL_SESSION_free|. A consumer which serializes
 // |session| with |SSL_SESSION_to_bytes| may not need to retain |session| and
 // will likely return zero. Returning one is equivalent to calling
 // |SSL_SESSION_up_ref| and then returning zero.
 //
 // Note: For a client, the callback may be called on abbreviated handshakes if a
 // ticket is renewed. Further, it may not be called until some time after
 // |SSL_do_handshake| or |SSL_connect| completes if False Start is enabled. Thus
 // it's recommended to use this callback over calling |SSL_get_session| on
 // handshake completion.
 OPENSSL_EXPORT void SSL_CTX_sess_set_new_cb(
     SSL_CTX *ctx, int (*new_session_cb)(SSL *ssl, SSL_SESSION *session));
 
 // SSL_CTX_sess_get_new_cb returns the callback set by
 // |SSL_CTX_sess_set_new_cb|.
 OPENSSL_EXPORT int (*SSL_CTX_sess_get_new_cb(SSL_CTX *ctx))(
     SSL *ssl, SSL_SESSION *session);
 
 // SSL_CTX_sess_set_remove_cb sets a callback which is called when a session is
 // removed from the internal session cache.
 //
 // TODO(davidben): What is the point of this callback? It seems useless since it
 // only fires on sessions in the internal cache.
 OPENSSL_EXPORT void SSL_CTX_sess_set_remove_cb(
     SSL_CTX *ctx,
     void (*remove_session_cb)(SSL_CTX *ctx, SSL_SESSION *session));
 
 // SSL_CTX_sess_get_remove_cb returns the callback set by
 // |SSL_CTX_sess_set_remove_cb|.
 OPENSSL_EXPORT void (*SSL_CTX_sess_get_remove_cb(SSL_CTX *ctx))(
     SSL_CTX *ctx, SSL_SESSION *session);
 
 // SSL_CTX_sess_set_get_cb sets a callback to look up a session by ID for a
 // server. The callback is passed the session ID and should return a matching
 // |SSL_SESSION| or NULL if not found. It should set |*out_copy| to zero and
 // return a new reference to the session. This callback is not used for a
 // client.
 //
 // For historical reasons, if |*out_copy| is set to one (default), the SSL
 // library will take a new reference to the returned |SSL_SESSION|, expecting
 // the callback to return a non-owning pointer. This is not recommended. If
 // |ctx| and thus the callback is used on multiple threads, the session may be
 // removed and invalidated before the SSL library calls |SSL_SESSION_up_ref|,
 // whereas the callback may synchronize internally.
 //
 // To look up a session asynchronously, the callback may return
 // |SSL_magic_pending_session_ptr|. See the documentation for that function and
 // |SSL_ERROR_PENDING_SESSION|.
 //
 // If the internal session cache is enabled, the callback is only consulted if
 // the internal cache does not return a match.
 OPENSSL_EXPORT void SSL_CTX_sess_set_get_cb(
     SSL_CTX *ctx, SSL_SESSION *(*get_session_cb)(SSL *ssl, const uint8_t *id,
                                                  int id_len, int *out_copy));
 
 // SSL_CTX_sess_get_get_cb returns the callback set by
 // |SSL_CTX_sess_set_get_cb|.
 OPENSSL_EXPORT SSL_SESSION *(*SSL_CTX_sess_get_get_cb(SSL_CTX *ctx))(
     SSL *ssl, const uint8_t *id, int id_len, int *out_copy);
 
 // SSL_magic_pending_session_ptr returns a magic |SSL_SESSION|* which indicates
 // that the session isn't currently unavailable. |SSL_get_error| will then
 // return |SSL_ERROR_PENDING_SESSION| and the handshake can be retried later
 // when the lookup has completed.
 OPENSSL_EXPORT SSL_SESSION *SSL_magic_pending_session_ptr(void);
 
 // SSL_CTX_set_resumption_across_names_enabled configures whether |ctx|, as a
 // TLS 1.3 server, signals its sessions are compatible with any identity in the
 // server certificate, e.g. all DNS names in the subjectAlternateNames list.
 // This does not change BoringSSL's resumption behavior, only whether it signals
 // this to the client. See draft-ietf-tls-cross-sni-resumption.
 //
 // When this is enabled, all identities in the server certificate should by
 // hosted by servers that accept TLS 1.3 tickets issued by |ctx|. The connection
 // will otherwise function, but performance may suffer from clients wasting
 // single-use tickets.
 OPENSSL_EXPORT void SSL_CTX_set_resumption_across_names_enabled(SSL_CTX *ctx,
                                                                 int enabled);
 
 // SSL_set_resumption_across_names_enabled configures whether |ssl|, as a
 // TLS 1.3 server, signals its sessions are compatible with any identity in the
 // server certificate, e.g. all DNS names in the subjectAlternateNames list.
 // This does not change BoringSSL's resumption behavior, only whether it signals
 // this to the client. See draft-ietf-tls-cross-sni-resumption.
 //
 // When this is enabled, all identities in the server certificate should by
 // hosted by servers that accept TLS 1.3 tickets issued by |ssl|. The connection
 // will otherwise function, but performance may suffer from clients wasting
 // single-use tickets.
 OPENSSL_EXPORT void SSL_set_resumption_across_names_enabled(SSL *ssl,
                                                             int enabled);
 
 
 // Session tickets.
 //
 // Session tickets, from RFC 5077, allow session resumption without server-side
 // state. The server maintains a secret ticket key and sends the client opaque
 // encrypted session parameters, called a ticket. When offering the session, the
 // client sends the ticket which the server decrypts to recover session state.
 // Session tickets are enabled by default but may be disabled with
 // |SSL_OP_NO_TICKET|.
 //
 // On the client, ticket-based sessions use the same APIs as ID-based tickets.
 // Callers do not need to handle them differently.
 //
 // On the server, tickets are encrypted and authenticated with a secret key.
 // By default, an |SSL_CTX| will manage session ticket encryption keys by
 // generating them internally and rotating every 48 hours. Tickets are minted
 // and processed transparently. The following functions may be used to configure
 // a persistent key or implement more custom behavior, including key rotation
 // and sharing keys between multiple servers in a large deployment. There are
 // three levels of customisation possible:
 //
 // 1) One can simply set the keys with |SSL_CTX_set_tlsext_ticket_keys|.
 // 2) One can configure an |EVP_CIPHER_CTX| and |HMAC_CTX| directly for
 //    encryption and authentication.
 // 3) One can configure an |SSL_TICKET_AEAD_METHOD| to have more control
 //    and the option of asynchronous decryption.
 //
 // An attacker that compromises a server's session ticket key can impersonate
 // the server and, prior to TLS 1.3, retroactively decrypt all application
 // traffic from sessions using that ticket key. Thus ticket keys must be
 // regularly rotated for forward secrecy. Note the default key is rotated
 // automatically once every 48 hours but manually configured keys are not.
 
 // SSL_DEFAULT_TICKET_KEY_ROTATION_INTERVAL is the interval with which the
 // default session ticket encryption key is rotated, if in use. If any
 // non-default ticket encryption mechanism is configured, automatic rotation is
 // disabled.
 #define SSL_DEFAULT_TICKET_KEY_ROTATION_INTERVAL (2 * 24 * 60 * 60)
 
 // SSL_CTX_get_tlsext_ticket_keys writes |ctx|'s session ticket key material to
 // |len| bytes of |out|. It returns one on success and zero if |len| is not
 // 48. If |out| is NULL, it returns 48 instead.
 OPENSSL_EXPORT int SSL_CTX_get_tlsext_ticket_keys(SSL_CTX *ctx, void *out,
                                                   size_t len);
 
 // SSL_CTX_set_tlsext_ticket_keys sets |ctx|'s session ticket key material to
 // |len| bytes of |in|. It returns one on success and zero if |len| is not
 // 48. If |in| is NULL, it returns 48 instead.
 OPENSSL_EXPORT int SSL_CTX_set_tlsext_ticket_keys(SSL_CTX *ctx, const void *in,
                                                   size_t len);
 
 // SSL_TICKET_KEY_NAME_LEN is the length of the key name prefix of a session
 // ticket.
 #define SSL_TICKET_KEY_NAME_LEN 16
 
 // SSL_CTX_set_tlsext_ticket_key_cb sets the ticket callback to |callback| and
 // returns one. |callback| will be called when encrypting a new ticket and when
 // decrypting a ticket from the client.
 //
 // In both modes, |ctx| and |hmac_ctx| will already have been initialized with
 // |EVP_CIPHER_CTX_init| and |HMAC_CTX_init|, respectively. |callback|
 // configures |hmac_ctx| with an HMAC digest and key, and configures |ctx|
 // for encryption or decryption, based on the mode.
 //
 // When encrypting a new ticket, |encrypt| will be one. It writes a public
 // 16-byte key name to |key_name| and a fresh IV to |iv|. The output IV length
 // must match |EVP_CIPHER_CTX_iv_length| of the cipher selected. In this mode,
 // |callback| returns 1 on success, 0 to decline sending a ticket, and -1 on
 // error.
 //
 // When decrypting a ticket, |encrypt| will be zero. |key_name| will point to a
 // 16-byte key name and |iv| points to an IV. The length of the IV consumed must
 // match |EVP_CIPHER_CTX_iv_length| of the cipher selected. In this mode,
 // |callback| returns -1 to abort the handshake, 0 if the ticket key was
 // unrecognized, and 1 or 2 on success. If it returns 2, the ticket will be
 // renewed. This may be used to re-key the ticket.
 //
 // WARNING: |callback| wildly breaks the usual return value convention and is
 // called in two different modes.
 OPENSSL_EXPORT int SSL_CTX_set_tlsext_ticket_key_cb(
     SSL_CTX *ctx,
     int (*callback)(SSL *ssl, uint8_t *key_name, uint8_t *iv,
                     EVP_CIPHER_CTX *ctx, HMAC_CTX *hmac_ctx, int encrypt));
 
 // ssl_ticket_aead_result_t enumerates the possible results from decrypting a
 // ticket with an |SSL_TICKET_AEAD_METHOD|.
 enum ssl_ticket_aead_result_t BORINGSSL_ENUM_INT {
   // ssl_ticket_aead_success indicates that the ticket was successfully
   // decrypted.
   ssl_ticket_aead_success,
   // ssl_ticket_aead_retry indicates that the operation could not be
   // immediately completed and must be reattempted, via |open|, at a later
   // point.
   ssl_ticket_aead_retry,
   // ssl_ticket_aead_ignore_ticket indicates that the ticket should be ignored
   // (i.e. is corrupt or otherwise undecryptable).
   ssl_ticket_aead_ignore_ticket,
   // ssl_ticket_aead_error indicates that a fatal error occured and the
   // handshake should be terminated.
   ssl_ticket_aead_error,
 };
 
 // ssl_ticket_aead_method_st (aka |SSL_TICKET_AEAD_METHOD|) contains methods
 // for encrypting and decrypting session tickets.
 struct ssl_ticket_aead_method_st {
   // max_overhead returns the maximum number of bytes of overhead that |seal|
   // may add.
   size_t (*max_overhead)(SSL *ssl);
 
   // seal encrypts and authenticates |in_len| bytes from |in|, writes, at most,
   // |max_out_len| bytes to |out|, and puts the number of bytes written in
   // |*out_len|. The |in| and |out| buffers may be equal but will not otherwise
   // alias. It returns one on success or zero on error. If the function returns
   // but |*out_len| is zero, BoringSSL will skip sending a ticket.
   int (*seal)(SSL *ssl, uint8_t *out, size_t *out_len, size_t max_out_len,
               const uint8_t *in, size_t in_len);
 
   // open authenticates and decrypts |in_len| bytes from |in|, writes, at most,
   // |max_out_len| bytes of plaintext to |out|, and puts the number of bytes
   // written in |*out_len|. The |in| and |out| buffers may be equal but will
   // not otherwise alias. See |ssl_ticket_aead_result_t| for details of the
   // return values. In the case that a retry is indicated, the caller should
   // arrange for the high-level operation on |ssl| to be retried when the
   // operation is completed, which will result in another call to |open|.
   enum ssl_ticket_aead_result_t (*open)(SSL *ssl, uint8_t *out, size_t *out_len,
                                         size_t max_out_len, const uint8_t *in,
                                         size_t in_len);
 };
 
 // SSL_CTX_set_ticket_aead_method configures a custom ticket AEAD method table
 // on |ctx|. |aead_method| must remain valid for the lifetime of |ctx|.
 OPENSSL_EXPORT void SSL_CTX_set_ticket_aead_method(
     SSL_CTX *ctx, const SSL_TICKET_AEAD_METHOD *aead_method);
 
 // SSL_process_tls13_new_session_ticket processes an unencrypted TLS 1.3
 // NewSessionTicket message from |buf| and returns a resumable |SSL_SESSION|,
 // or NULL on error. The caller takes ownership of the returned session and
 // must call |SSL_SESSION_free| to free it.
 //
 // |buf| contains |buf_len| bytes that represents a complete NewSessionTicket
 // message including its header, i.e., one byte for the type (0x04) and three
 // bytes for the length. |buf| must contain only one such message.
 //
 // This function may be used to process NewSessionTicket messages in TLS 1.3
 // clients that are handling the record layer externally.
 OPENSSL_EXPORT SSL_SESSION *SSL_process_tls13_new_session_ticket(
     SSL *ssl, const uint8_t *buf, size_t buf_len);
 
 // SSL_CTX_set_num_tickets configures |ctx| to send |num_tickets| immediately
 // after a successful TLS 1.3 handshake as a server. It returns one. Large
 // values of |num_tickets| will be capped within the library.
 //
 // By default, BoringSSL sends two tickets.
 OPENSSL_EXPORT int SSL_CTX_set_num_tickets(SSL_CTX *ctx, size_t num_tickets);
 
 // SSL_CTX_get_num_tickets returns the number of tickets |ctx| will send
 // immediately after a successful TLS 1.3 handshake as a server.
 OPENSSL_EXPORT size_t SSL_CTX_get_num_tickets(const SSL_CTX *ctx);
 
 
 // Diffie-Hellman groups and ephemeral key exchanges.
 //
 // Most TLS handshakes (ECDHE cipher suites in TLS 1.2, and all supported TLS
 // 1.3 modes) incorporate an ephemeral key exchange, most commonly using
 // Elliptic Curve Diffie-Hellman (ECDH), as described in RFC 8422. The key
 // exchange algorithm is negotiated separately from the cipher suite, using
 // NamedGroup values, which define Diffie-Hellman groups.
 //
 // Historically, these values were known as "curves", in reference to ECDH, and
 // some APIs refer to the original name. RFC 7919 renamed them to "groups" in
 // reference to Diffie-Hellman in general. These values are also used to select
 // experimental post-quantum KEMs. Though not Diffie-Hellman groups, KEMs can
 // fill a similar role in TLS, so they use the same codepoints.
 //
 // In TLS 1.2, the ECDH values also negotiate elliptic curves used in ECDSA. In
 // TLS 1.3 and later, ECDSA curves are part of the signature algorithm. See
 // |SSL_SIGN_*|.
 
 // SSL_GROUP_* define TLS group IDs.
 #define SSL_GROUP_SECP256R1 23
 #define SSL_GROUP_SECP384R1 24
 #define SSL_GROUP_SECP521R1 25
 #define SSL_GROUP_X25519 29
 #define SSL_GROUP_X25519_MLKEM768 0x11ec
 #define SSL_GROUP_X25519_KYBER768_DRAFT00 0x6399
 
 // SSL_CTX_set1_group_ids sets the preferred groups for |ctx| to |group_ids|.
 // Each element of |group_ids| should be one of the |SSL_GROUP_*| constants. It
 // returns one on success and zero on failure.
 OPENSSL_EXPORT int SSL_CTX_set1_group_ids(SSL_CTX *ctx,
                                           const uint16_t *group_ids,
                                           size_t num_group_ids);
 
 // SSL_set1_group_ids sets the preferred groups for |ssl| to |group_ids|. Each
 // element of |group_ids| should be one of the |SSL_GROUP_*| constants. It
 // returns one on success and zero on failure.
 OPENSSL_EXPORT int SSL_set1_group_ids(SSL *ssl, const uint16_t *group_ids,
                                       size_t num_group_ids);
 
 // SSL_get_group_id returns the ID of the group used by |ssl|'s most recently
 // completed handshake, or 0 if not applicable.
 OPENSSL_EXPORT uint16_t SSL_get_group_id(const SSL *ssl);
 
 // SSL_get_group_name returns a human-readable name for the group specified by
 // the given TLS group ID, or NULL if the group is unknown.
 OPENSSL_EXPORT const char *SSL_get_group_name(uint16_t group_id);
 
 // SSL_get_all_group_names outputs a list of possible strings
 // |SSL_get_group_name| may return in this version of BoringSSL. It writes at
 // most |max_out| entries to |out| and returns the total number it would have
 // written, if |max_out| had been large enough. |max_out| may be initially set
 // to zero to size the output.
 //
 // This function is only intended to help initialize tables in callers that want
 // possible strings pre-declared. This list would not be suitable to set a list
 // of supported features. It is in no particular order, and may contain
 // placeholder, experimental, or deprecated values that do not apply to every
 // caller. Future versions of BoringSSL may also return strings not in this
 // list, so this does not apply if, say, sending strings across services.
 OPENSSL_EXPORT size_t SSL_get_all_group_names(const char **out, size_t max_out);
 
 // The following APIs also configure Diffie-Hellman groups, but use |NID_*|
 // constants instead of |SSL_GROUP_*| constants. These are provided for OpenSSL
 // compatibility. Where NIDs are unstable constants specific to OpenSSL and
 // BoringSSL, group IDs are defined by the TLS protocol. Prefer the group ID
 // representation if storing persistently, or exporting to another process or
 // library.
 
 // SSL_CTX_set1_groups sets the preferred groups for |ctx| to be |groups|. Each
 // element of |groups| should be a |NID_*| constant from nid.h. It returns one
 // on success and zero on failure.
 OPENSSL_EXPORT int SSL_CTX_set1_groups(SSL_CTX *ctx, const int *groups,
                                        size_t num_groups);
 
 // SSL_set1_groups sets the preferred groups for |ssl| to be |groups|. Each
 // element of |groups| should be a |NID_*| constant from nid.h. It returns one
 // on success and zero on failure.
 OPENSSL_EXPORT int SSL_set1_groups(SSL *ssl, const int *groups,
                                    size_t num_groups);
 
 // SSL_CTX_set1_groups_list decodes |groups| as a colon-separated list of group
 // names (e.g. "X25519" or "P-256") and sets |ctx|'s preferred groups to the
 // result. It returns one on success and zero on failure.
 OPENSSL_EXPORT int SSL_CTX_set1_groups_list(SSL_CTX *ctx, const char *groups);
 
 // SSL_set1_groups_list decodes |groups| as a colon-separated list of group
 // names (e.g. "X25519" or "P-256") and sets |ssl|'s preferred groups to the
 // result. It returns one on success and zero on failure.
 OPENSSL_EXPORT int SSL_set1_groups_list(SSL *ssl, const char *groups);
 
 // SSL_get_negotiated_group returns the NID of the group used by |ssl|'s most
 // recently completed handshake, or |NID_undef| if not applicable.
 OPENSSL_EXPORT int SSL_get_negotiated_group(const SSL *ssl);
 
 
 // Certificate verification.
 //
 // SSL may authenticate either endpoint with an X.509 certificate. Typically
 // this is used to authenticate the server to the client. These functions
 // configure certificate verification.
 //
 // WARNING: By default, certificate verification errors on a client are not
 // fatal. See |SSL_VERIFY_NONE| This may be configured with
 // |SSL_CTX_set_verify|.
 //
 // By default clients are anonymous but a server may request a certificate from
 // the client by setting |SSL_VERIFY_PEER|.
 //
 // Many of these functions use OpenSSL's legacy X.509 stack which is
 // underdocumented and deprecated, but the replacement isn't ready yet. For
 // now, consumers may use the existing stack or bypass it by performing
 // certificate verification externally. This may be done with
 // |SSL_CTX_set_cert_verify_callback| or by extracting the chain with
 // |SSL_get_peer_cert_chain| after the handshake. In the future, functions will
 // be added to use the SSL stack without dependency on any part of the legacy
 // X.509 and ASN.1 stack.
 //
 // To augment certificate verification, a client may also enable OCSP stapling
 // (RFC 6066) and Certificate Transparency (RFC 6962) extensions.
 
 // SSL_VERIFY_NONE, on a client, verifies the server certificate but does not
 // make errors fatal. The result may be checked with |SSL_get_verify_result|. On
 // a server it does not request a client certificate. This is the default.
 #define SSL_VERIFY_NONE 0x00
 
 // SSL_VERIFY_PEER, on a client, makes server certificate errors fatal. On a
 // server it requests a client certificate and makes errors fatal. However,
 // anonymous clients are still allowed. See
 // |SSL_VERIFY_FAIL_IF_NO_PEER_CERT|.
 #define SSL_VERIFY_PEER 0x01
 
 // SSL_VERIFY_FAIL_IF_NO_PEER_CERT configures a server to reject connections if
 // the client declines to send a certificate. This flag must be used together
 // with |SSL_VERIFY_PEER|, otherwise it won't work.
 #define SSL_VERIFY_FAIL_IF_NO_PEER_CERT 0x02
 
 // SSL_CTX_set_verify configures certificate verification behavior. |mode| is
 // one of the |SSL_VERIFY_*| values defined above. |callback| should be NULL.
 //
 // If |callback| is non-NULL, it is called as in |X509_STORE_CTX_set_verify_cb|,
 // which is a deprecated and fragile mechanism to run the default certificate
 // verification process, but suppress individual errors in it. See
 // |X509_STORE_CTX_set_verify_cb| for details, If set, the callback may use
 // |SSL_get_ex_data_X509_STORE_CTX_idx| with |X509_STORE_CTX_get_ex_data| to
 // look up the |SSL| from |store_ctx|.
 //
 // WARNING: |callback| is not suitable for implementing custom certificate
 // check, accepting all certificates, or extracting the certificate after
 // verification. It does not replace the default process and is called multiple
 // times throughout that process. It is also very difficult to implement this
 // callback safely, without inadvertently relying on implementation details or
 // making incorrect assumptions about when the callback is called.
 //
 // Instead, use |SSL_CTX_set_custom_verify| or
 // |SSL_CTX_set_cert_verify_callback| to customize certificate verification.
 // Those callbacks can inspect the peer-sent chain, call |X509_verify_cert| and
 // inspect the result, or perform other operations more straightforwardly.
 OPENSSL_EXPORT void SSL_CTX_set_verify(
     SSL_CTX *ctx, int mode, int (*callback)(int ok, X509_STORE_CTX *store_ctx));
 
 // SSL_set_verify configures certificate verification behavior. |mode| is one of
 // the |SSL_VERIFY_*| values defined above. |callback| should be NULL.
 //
 // If |callback| is non-NULL, it is called as in |X509_STORE_CTX_set_verify_cb|,
 // which is a deprecated and fragile mechanism to run the default certificate
 // verification process, but suppress individual errors in it. See
 // |X509_STORE_CTX_set_verify_cb| for details, If set, the callback may use
 // |SSL_get_ex_data_X509_STORE_CTX_idx| with |X509_STORE_CTX_get_ex_data| to
 // look up the |SSL| from |store_ctx|.
 //
 // WARNING: |callback| is not suitable for implementing custom certificate
 // check, accepting all certificates, or extracting the certificate after
 // verification. It does not replace the default process and is called multiple
 // times throughout that process. It is also very difficult to implement this
 // callback safely, without inadvertently relying on implementation details or
 // making incorrect assumptions about when the callback is called.
 //
 // Instead, use |SSL_set_custom_verify| or |SSL_set_cert_verify_callback| to
 // customize certificate verification. Those callbacks can inspect the peer-sent
 // chain, call |X509_verify_cert| and inspect the result, or perform other
 // operations more straightforwardly.
 OPENSSL_EXPORT void SSL_set_verify(SSL *ssl, int mode,
                                    int (*callback)(int ok,
                                                    X509_STORE_CTX *store_ctx));
 
 enum ssl_verify_result_t BORINGSSL_ENUM_INT {
   ssl_verify_ok,
   ssl_verify_invalid,
   ssl_verify_retry,
 };
 
 // SSL_CTX_set_custom_verify configures certificate verification. |mode| is one
 // of the |SSL_VERIFY_*| values defined above. |callback| performs the
 // certificate verification.
 //
 // The callback may call |SSL_get0_peer_certificates| for the certificate chain
 // to validate. The callback should return |ssl_verify_ok| if the certificate is
 // valid. If the certificate is invalid, the callback should return
 // |ssl_verify_invalid| and optionally set |*out_alert| to an alert to send to
 // the peer. Some useful alerts include |SSL_AD_CERTIFICATE_EXPIRED|,
 // |SSL_AD_CERTIFICATE_REVOKED|, |SSL_AD_UNKNOWN_CA|, |SSL_AD_BAD_CERTIFICATE|,
 // |SSL_AD_CERTIFICATE_UNKNOWN|, and |SSL_AD_INTERNAL_ERROR|. See RFC 5246
 // section 7.2.2 for their precise meanings. If unspecified,
 // |SSL_AD_CERTIFICATE_UNKNOWN| will be sent by default.
 //
 // To verify a certificate asynchronously, the callback may return
 // |ssl_verify_retry|. The handshake will then pause with |SSL_get_error|
 // returning |SSL_ERROR_WANT_CERTIFICATE_VERIFY|.
 OPENSSL_EXPORT void SSL_CTX_set_custom_verify(
     SSL_CTX *ctx, int mode,
     enum ssl_verify_result_t (*callback)(SSL *ssl, uint8_t *out_alert));
 
 // SSL_set_custom_verify behaves like |SSL_CTX_set_custom_verify| but configures
 // an individual |SSL|.
 OPENSSL_EXPORT void SSL_set_custom_verify(
     SSL *ssl, int mode,
     enum ssl_verify_result_t (*callback)(SSL *ssl, uint8_t *out_alert));
 
 // SSL_CTX_get_verify_mode returns |ctx|'s verify mode, set by
 // |SSL_CTX_set_verify|.
 OPENSSL_EXPORT int SSL_CTX_get_verify_mode(const SSL_CTX *ctx);
 
 // SSL_get_verify_mode returns |ssl|'s verify mode, set by |SSL_CTX_set_verify|
 // or |SSL_set_verify|.  It returns -1 on error.
 OPENSSL_EXPORT int SSL_get_verify_mode(const SSL *ssl);
 
 // SSL_CTX_get_verify_callback returns the callback set by
 // |SSL_CTX_set_verify|.
 OPENSSL_EXPORT int (*SSL_CTX_get_verify_callback(const SSL_CTX *ctx))(
     int ok, X509_STORE_CTX *store_ctx);
 
 // SSL_get_verify_callback returns the callback set by |SSL_CTX_set_verify| or
 // |SSL_set_verify|.
 OPENSSL_EXPORT int (*SSL_get_verify_callback(const SSL *ssl))(
     int ok, X509_STORE_CTX *store_ctx);
 
 // SSL_set1_host sets a DNS name that will be required to be present in the
 // verified leaf certificate. It returns one on success and zero on error.
 //
 // Note: unless _some_ name checking is performed, certificate validation is
 // ineffective. Simply checking that a host has some certificate from a CA is
 // rarely meaningful—you have to check that the CA believed that the host was
 // who you expect to be talking to.
 //
 // By default, both subject alternative names and the subject's common name
 // attribute are checked. The latter has long been deprecated, so callers should
 // call |SSL_set_hostflags| with |X509_CHECK_FLAG_NEVER_CHECK_SUBJECT| to use
 // the standard behavior. https://crbug.com/boringssl/464 tracks fixing the
 // default.
 OPENSSL_EXPORT int SSL_set1_host(SSL *ssl, const char *hostname);
 
 // SSL_set_hostflags calls |X509_VERIFY_PARAM_set_hostflags| on the
 // |X509_VERIFY_PARAM| associated with this |SSL*|. |flags| should be some
 // combination of the |X509_CHECK_*| constants.
 OPENSSL_EXPORT void SSL_set_hostflags(SSL *ssl, unsigned flags);
 
 // SSL_CTX_set_verify_depth sets the maximum depth of a certificate chain
 // accepted in verification. This count excludes both the target certificate and
 // the trust anchor (root certificate).
 OPENSSL_EXPORT void SSL_CTX_set_verify_depth(SSL_CTX *ctx, int depth);
 
 // SSL_set_verify_depth sets the maximum depth of a certificate chain accepted
 // in verification. This count excludes both the target certificate and the
 // trust anchor (root certificate).
 OPENSSL_EXPORT void SSL_set_verify_depth(SSL *ssl, int depth);
 
 // SSL_CTX_get_verify_depth returns the maximum depth of a certificate accepted
 // in verification.
 OPENSSL_EXPORT int SSL_CTX_get_verify_depth(const SSL_CTX *ctx);
 
 // SSL_get_verify_depth returns the maximum depth of a certificate accepted in
 // verification.
 OPENSSL_EXPORT int SSL_get_verify_depth(const SSL *ssl);
 
 // SSL_CTX_set1_param sets verification parameters from |param|. It returns one
 // on success and zero on failure. The caller retains ownership of |param|.
 OPENSSL_EXPORT int SSL_CTX_set1_param(SSL_CTX *ctx,
                                       const X509_VERIFY_PARAM *param);
 
 // SSL_set1_param sets verification parameters from |param|. It returns one on
 // success and zero on failure. The caller retains ownership of |param|.
 OPENSSL_EXPORT int SSL_set1_param(SSL *ssl, const X509_VERIFY_PARAM *param);
 
 // SSL_CTX_get0_param returns |ctx|'s |X509_VERIFY_PARAM| for certificate
 // verification. The caller must not release the returned pointer but may call
 // functions on it to configure it.
 OPENSSL_EXPORT X509_VERIFY_PARAM *SSL_CTX_get0_param(SSL_CTX *ctx);
 
 // SSL_get0_param returns |ssl|'s |X509_VERIFY_PARAM| for certificate
 // verification. The caller must not release the returned pointer but may call
 // functions on it to configure it.
 OPENSSL_EXPORT X509_VERIFY_PARAM *SSL_get0_param(SSL *ssl);
 
 // SSL_CTX_set_purpose sets |ctx|'s |X509_VERIFY_PARAM|'s 'purpose' parameter to
 // |purpose|. It returns one on success and zero on error.
 OPENSSL_EXPORT int SSL_CTX_set_purpose(SSL_CTX *ctx, int purpose);
 
 // SSL_set_purpose sets |ssl|'s |X509_VERIFY_PARAM|'s 'purpose' parameter to
 // |purpose|. It returns one on success and zero on error.
 OPENSSL_EXPORT int SSL_set_purpose(SSL *ssl, int purpose);
 
 // SSL_CTX_set_trust sets |ctx|'s |X509_VERIFY_PARAM|'s 'trust' parameter to
 // |trust|. It returns one on success and zero on error.
 OPENSSL_EXPORT int SSL_CTX_set_trust(SSL_CTX *ctx, int trust);
 
 // SSL_set_trust sets |ssl|'s |X509_VERIFY_PARAM|'s 'trust' parameter to
 // |trust|. It returns one on success and zero on error.
 OPENSSL_EXPORT int SSL_set_trust(SSL *ssl, int trust);
 
 // SSL_CTX_set_cert_store sets |ctx|'s certificate store to |store|. It takes
 // ownership of |store|. The store is used for certificate verification.
 //
 // The store is also used for the auto-chaining feature, but this is deprecated.
 // See also |SSL_MODE_NO_AUTO_CHAIN|.
 OPENSSL_EXPORT void SSL_CTX_set_cert_store(SSL_CTX *ctx, X509_STORE *store);
 
 // SSL_CTX_get_cert_store returns |ctx|'s certificate store.
 OPENSSL_EXPORT X509_STORE *SSL_CTX_get_cert_store(const SSL_CTX *ctx);
 
 // SSL_CTX_set_default_verify_paths calls |X509_STORE_set_default_paths| on
 // |ctx|'s store. See that function for details.
 //
 // Using this function is not recommended. In OpenSSL, these defaults are
 // determined by OpenSSL's install prefix. There is no corresponding concept for
 // BoringSSL. Future versions of BoringSSL may change or remove this
 // functionality.
 OPENSSL_EXPORT int SSL_CTX_set_default_verify_paths(SSL_CTX *ctx);
 
 // SSL_CTX_load_verify_locations calls |X509_STORE_load_locations| on |ctx|'s
 // store. See that function for details.
 OPENSSL_EXPORT int SSL_CTX_load_verify_locations(SSL_CTX *ctx,
                                                  const char *ca_file,
                                                  const char *ca_dir);
 
 // SSL_get_verify_result returns the result of certificate verification. It is
 // either |X509_V_OK| or a |X509_V_ERR_*| value.
 OPENSSL_EXPORT long SSL_get_verify_result(const SSL *ssl);
 
 // SSL_alert_from_verify_result returns the SSL alert code, such as
 // |SSL_AD_CERTIFICATE_EXPIRED|, that corresponds to an |X509_V_ERR_*| value.
 // The return value is always an alert, even when |result| is |X509_V_OK|.
 OPENSSL_EXPORT int SSL_alert_from_verify_result(long result);
 
 // SSL_get_ex_data_X509_STORE_CTX_idx returns the ex_data index used to look up
 // the |SSL| associated with an |X509_STORE_CTX| in the verify callback.
 OPENSSL_EXPORT int SSL_get_ex_data_X509_STORE_CTX_idx(void);
 
 // SSL_CTX_set_cert_verify_callback sets a custom callback to be called on
 // certificate verification rather than |X509_verify_cert|. |store_ctx| contains
 // the verification parameters. The callback should return one on success and
 // zero on fatal error. It may use |X509_STORE_CTX_set_error| to set a
 // verification result.
 //
 // The callback may use |SSL_get_ex_data_X509_STORE_CTX_idx| to recover the
 // |SSL| object from |store_ctx|.
 OPENSSL_EXPORT void SSL_CTX_set_cert_verify_callback(
     SSL_CTX *ctx, int (*callback)(X509_STORE_CTX *store_ctx, void *arg),
     void *arg);
 
 // SSL_enable_signed_cert_timestamps causes |ssl| (which must be the client end
 // of a connection) to request SCTs from the server. See
 // https://tools.ietf.org/html/rfc6962.
 //
 // Call |SSL_get0_signed_cert_timestamp_list| to recover the SCT after the
 // handshake.
 OPENSSL_EXPORT void SSL_enable_signed_cert_timestamps(SSL *ssl);
 
 // SSL_CTX_enable_signed_cert_timestamps enables SCT requests on all client SSL
 // objects created from |ctx|.
 //
 // Call |SSL_get0_signed_cert_timestamp_list| to recover the SCT after the
 // handshake.
 OPENSSL_EXPORT void SSL_CTX_enable_signed_cert_timestamps(SSL_CTX *ctx);
 
 // SSL_enable_ocsp_stapling causes |ssl| (which must be the client end of a
 // connection) to request a stapled OCSP response from the server.
 //
 // Call |SSL_get0_ocsp_response| to recover the OCSP response after the
 // handshake.
 OPENSSL_EXPORT void SSL_enable_ocsp_stapling(SSL *ssl);
 
 // SSL_CTX_enable_ocsp_stapling enables OCSP stapling on all client SSL objects
 // created from |ctx|.
 //
 // Call |SSL_get0_ocsp_response| to recover the OCSP response after the
 // handshake.
 OPENSSL_EXPORT void SSL_CTX_enable_ocsp_stapling(SSL_CTX *ctx);
 
 // SSL_CTX_set0_verify_cert_store sets an |X509_STORE| that will be used
 // exclusively for certificate verification and returns one. Ownership of
 // |store| is transferred to the |SSL_CTX|.
 OPENSSL_EXPORT int SSL_CTX_set0_verify_cert_store(SSL_CTX *ctx,
                                                   X509_STORE *store);
 
 // SSL_CTX_set1_verify_cert_store sets an |X509_STORE| that will be used
 // exclusively for certificate verification and returns one. An additional
 // reference to |store| will be taken.
 OPENSSL_EXPORT int SSL_CTX_set1_verify_cert_store(SSL_CTX *ctx,
                                                   X509_STORE *store);
 
 // SSL_set0_verify_cert_store sets an |X509_STORE| that will be used
 // exclusively for certificate verification and returns one. Ownership of
 // |store| is transferred to the |SSL|.
 OPENSSL_EXPORT int SSL_set0_verify_cert_store(SSL *ssl, X509_STORE *store);
 
 // SSL_set1_verify_cert_store sets an |X509_STORE| that will be used
 // exclusively for certificate verification and returns one. An additional
 // reference to |store| will be taken.
 OPENSSL_EXPORT int SSL_set1_verify_cert_store(SSL *ssl, X509_STORE *store);
 
 // SSL_CTX_set_verify_algorithm_prefs configures |ctx| to use |prefs| as the
 // preference list when verifying signatures from the peer's long-term key in
 // TLS 1.2 and up. It returns one on zero on error. |prefs| should not include
 // the internal-only TLS 1.0 value |SSL_SIGN_RSA_PKCS1_MD5_SHA1|.
 //
 // This setting is not used in TLS 1.0 and 1.1. Those protocols always sign a
 // hardcoded algorithm (an MD5/SHA-1 concatenation for RSA, and SHA-1 for
 // ECDSA). BoringSSL will accept those algorithms if and only if those versions
 // are used. To disable them, set the minimum version to TLS 1.2 (default) or
 // higher.
 OPENSSL_EXPORT int SSL_CTX_set_verify_algorithm_prefs(SSL_CTX *ctx,
                                                       const uint16_t *prefs,
                                                       size_t num_prefs);
 
 // SSL_set_verify_algorithm_prefs configures |ssl| to use |prefs| as the
 // preference list when verifying signatures from the peer's long-term key in
 // TLS 1.2 and up. It returns one on zero on error. |prefs| should not include
 // the internal-only TLS 1.0 value |SSL_SIGN_RSA_PKCS1_MD5_SHA1|.
 //
 // This setting is not used in TLS 1.0 and 1.1. Those protocols always sign a
 // hardcoded algorithm (an MD5/SHA-1 concatenation for RSA, and SHA-1 for
 // ECDSA). BoringSSL will accept those algorithms if and only if those versions
 // are used. To disable them, set the minimum version to TLS 1.2 (default) or
 // higher.
 OPENSSL_EXPORT int SSL_set_verify_algorithm_prefs(SSL *ssl,
                                                   const uint16_t *prefs,
                                                   size_t num_prefs);
 
 
 // Certificate authorities.
 //
 // TLS implementations can send a list of supported certificate authorities to
 // guide the peer in selecting a certificate. This was originally defined for
 // servers requesting client certificates, but TLS 1.3 generalized it to server
 // certificates with the certificate_authorities extension.
 //
 // The following functions can be used to configure and query this list. They do
 // not directly impact certificate verification, only the list of certificate
 // authorities sent to the peer.
 
 // SSL_set_client_CA_list sets |ssl|'s client certificate CA list to
 // |name_list|. It takes ownership of |name_list|.
 OPENSSL_EXPORT void SSL_set_client_CA_list(SSL *ssl,
                                            STACK_OF(X509_NAME) *name_list);
 
 // SSL_CTX_set_client_CA_list sets |ctx|'s client certificate CA list to
 // |name_list|. It takes ownership of |name_list|.
 OPENSSL_EXPORT void SSL_CTX_set_client_CA_list(SSL_CTX *ctx,
                                                STACK_OF(X509_NAME) *name_list);
 
 // SSL_set0_client_CAs sets |ssl|'s client certificate CA list to |name_list|,
 // which should contain DER-encoded distinguished names (RFC 5280). It takes
 // ownership of |name_list|.
 OPENSSL_EXPORT void SSL_set0_client_CAs(SSL *ssl,
                                         STACK_OF(CRYPTO_BUFFER) *name_list);
 
 // SSL_set0_CA_names sets |ssl|'s CA name list for the certificate authorities
 // extension to |name_list|, which should contain DER-encoded distinguished
 // names (RFC 5280). It takes ownership of |name_list|.
 OPENSSL_EXPORT void SSL_set0_CA_names(SSL *ssl,
                                       STACK_OF(CRYPTO_BUFFER) *name_list);
 
 // SSL_CTX_set0_client_CAs sets |ctx|'s client certificate CA list to
 // |name_list|, which should contain DER-encoded distinguished names (RFC 5280).
 // It takes ownership of |name_list|.
 OPENSSL_EXPORT void SSL_CTX_set0_client_CAs(SSL_CTX *ctx,
                                             STACK_OF(CRYPTO_BUFFER) *name_list);
 
 // SSL_get_client_CA_list returns |ssl|'s client certificate CA list. If |ssl|
 // has not been configured as a client, this is the list configured by
 // |SSL_CTX_set_client_CA_list|.
 //
 // If configured as a client, it returns the client certificate CA list sent by
 // the server. In this mode, the behavior is undefined except during the
 // callbacks set by |SSL_CTX_set_cert_cb| and |SSL_CTX_set_client_cert_cb| or
 // when the handshake is paused because of them.
 OPENSSL_EXPORT STACK_OF(X509_NAME) *SSL_get_client_CA_list(const SSL *ssl);
 
 // SSL_get0_server_requested_CAs returns the CAs sent by a server to guide a
 // client in certificate selection. They are a series of DER-encoded X.509
 // names. This function may only be called during a callback set by
 // |SSL_CTX_set_cert_cb| or when the handshake is paused because of it.
 //
 // The returned stack is owned by |ssl|, as are its contents. It should not be
 // used past the point where the handshake is restarted after the callback.
 OPENSSL_EXPORT const STACK_OF(CRYPTO_BUFFER) *SSL_get0_server_requested_CAs(
     const SSL *ssl);
 
 // SSL_CTX_get_client_CA_list returns |ctx|'s client certificate CA list.
 OPENSSL_EXPORT STACK_OF(X509_NAME) *SSL_CTX_get_client_CA_list(
     const SSL_CTX *ctx);
 
 // SSL_add_client_CA appends |x509|'s subject to the client certificate CA list.
 // It returns one on success or zero on error. The caller retains ownership of
 // |x509|.
 OPENSSL_EXPORT int SSL_add_client_CA(SSL *ssl, X509 *x509);
 
 // SSL_CTX_add_client_CA appends |x509|'s subject to the client certificate CA
 // list. It returns one on success or zero on error. The caller retains
 // ownership of |x509|.
 OPENSSL_EXPORT int SSL_CTX_add_client_CA(SSL_CTX *ctx, X509 *x509);
 
 // SSL_load_client_CA_file opens |file| and reads PEM-encoded certificates from
 // it. It returns a newly-allocated stack of the certificate subjects or NULL
 // on error. Duplicates in |file| are ignored.
 OPENSSL_EXPORT STACK_OF(X509_NAME) *SSL_load_client_CA_file(const char *file);
 
 // SSL_dup_CA_list makes a deep copy of |list|. It returns the new list on
 // success or NULL on allocation error.
 OPENSSL_EXPORT STACK_OF(X509_NAME) *SSL_dup_CA_list(STACK_OF(X509_NAME) *list);
 
 // SSL_add_file_cert_subjects_to_stack behaves like |SSL_load_client_CA_file|
 // but appends the result to |out|. It returns one on success or zero on
 // error.
 OPENSSL_EXPORT int SSL_add_file_cert_subjects_to_stack(STACK_OF(X509_NAME) *out,
                                                        const char *file);
 
 // SSL_add_bio_cert_subjects_to_stack behaves like
 // |SSL_add_file_cert_subjects_to_stack| but reads from |bio|.
 OPENSSL_EXPORT int SSL_add_bio_cert_subjects_to_stack(STACK_OF(X509_NAME) *out,
                                                       BIO *bio);
 
 
 // Trust Anchor Identifiers.
 //
 // The trust_anchors extension, like certificate_authorities, allows clients to
 // communicate supported CAs to guide server certificate selection, or vice
 // versa. It better supports larger PKIs by referring to CAs by short "trust
 // anchor IDs" and, in the server certificate direction, allowing a client to
 // advertise only a subset of its full list, with DNS hinting and a retry
 // mechanism to manage the subset.
 //
 // See https://datatracker.ietf.org/doc/draft-ietf-tls-trust-anchor-ids/
 //
 // BoringSSL currently only implements this for server certificates, and not yet
 // client certificates.
 
 // SSL_CREDENTIAL_set1_trust_anchor_id sets |cred|'s trust anchor ID to |id|, or
 // clears it if |id_len| is zero. It returns one on success and zero on
 // error. If not clearing, |id| must be in binary format (Section 3 of
 // draft-ietf-tls-trust-anchor-ids-00) of length |id_len|, and describe the
 // issuer of the final certificate in |cred|'s certificate chain.
 //
 // Additionally, |cred| must enable issuer matching (see
 // SSL_CREDENTIAL_set_must_match_issuer|) for this value to take effect.
 //
 // For better extensibility, callers are recommended to configure this
 // information with a CertificatePropertyList instead. See
 // |SSL_CREDENTIAL_set1_certificate_properties|.
 OPENSSL_EXPORT int SSL_CREDENTIAL_set1_trust_anchor_id(SSL_CREDENTIAL *cred,
                                                        const uint8_t *id,
                                                        size_t id_len);
 
 // SSL_CTX_set1_requested_trust_anchors configures |ctx| to request a
 // certificate issued by one of the trust anchors in |ids|. It returns one on
 // success and zero on error. |ids| must be a list of trust anchor IDs in
 // wire-format (a series of non-empty, 8-bit length-prefixed strings).
 //
 // The list may describe application's full list of supported trust anchors, or
 // a, possibly empty, subset. Applications can select this subset using
 // out-of-band information, such as the DNS hint in Section 5 of
 // draft-ietf-tls-trust-anchor-ids-00. Client applications sending a subset
 // should use |SSL_get0_peer_available_trust_anchors| to implement the retry
 // flow from Section 4.3 of draft-ietf-tls-trust-anchor-ids-00.
 //
 // If empty (|ids_len| is zero), the trust_anchors extension will still be sent
 // in ClientHello. This may be used by a client application to signal support
 // for the retry flow without requesting specific trust anchors.
 //
 // This function does not directly impact certificate verification, only the
 // list of trust anchors sent to the peer.
 OPENSSL_EXPORT int SSL_CTX_set1_requested_trust_anchors(SSL_CTX *ctx,
                                                         const uint8_t *ids,
                                                         size_t ids_len);
 
 // SSL_set1_requested_trust_anchors behaves like
 // |SSL_CTX_set1_requested_trust_anchors| but configures the value on |ssl|.
 OPENSSL_EXPORT int SSL_set1_requested_trust_anchors(SSL *ssl,
                                                     const uint8_t *ids,
                                                     size_t ids_len);
 
 // SSL_peer_matched_trust_anchor returns one if the peer reported that its
 // certificate chain matched one of the trust anchor IDs requested by |ssl|, and
 // zero otherwise.
 //
 // This value is only available during the handshake and is expected to be
 // called during certificate verification, e.g. during |SSL_set_custom_verify|
 // or |SSL_CTX_set_cert_verify_callback| callbacks. If the value is one, callers
 // can safely treat the peer's certificate chain as a pre-built path and skip
 // path-building in certificate verification.
 OPENSSL_EXPORT int SSL_peer_matched_trust_anchor(const SSL *ssl);
 
 // SSL_get0_peer_available_trust_anchors gets the peer's available trust anchor
 // IDs. It sets |*out| and |*out_len| so that |*out| points to |*out_len| bytes
 // containing the list in wire format (i.e. a series of non-empty
 // 8-bit-length-prefixed strings). If the peer did not provide a list, the
 // function will output zero bytes. Only servers can provide available trust
 // anchor IDs, so this API will only output a list when |ssl| is a client.
 //
 // This value is only available during the handshake and is expected to be
 // called in the event of certificate verification failure. Client applications
 // can use it to retry the connection, requesting different trust anchors. See
 // Section 4.3 of draft-ietf-tls-trust-anchor-ids-00 for details.
 // |CBS_get_u8_length_prefixed| may be used to iterate over the format.
 //
 // If needed in other contexts, callers may save the value during certificate
 // verification, or at |SSL_CB_HANDSHAKE_DONE| with |SSL_CTX_set_info_callback|.
 OPENSSL_EXPORT void SSL_get0_peer_available_trust_anchors(const SSL *ssl,
                                                           const uint8_t **out,
                                                           size_t *out_len);
 
 
 // Server name indication.
 //
 // The server_name extension (RFC 3546) allows the client to advertise the name
 // of the server it is connecting to. This is used in virtual hosting
 // deployments to select one of a several certificates on a single IP. Only the
 // host_name name type is supported.
 
 #define TLSEXT_NAMETYPE_host_name 0
 
 // SSL_set_tlsext_host_name, for a client, configures |ssl| to advertise |name|
 // in the server_name extension. It returns one on success and zero on error.
 OPENSSL_EXPORT int SSL_set_tlsext_host_name(SSL *ssl, const char *name);
 
 // SSL_get_servername, for a server, returns the hostname supplied by the
 // client or NULL if there was none. The |type| argument must be
 // |TLSEXT_NAMETYPE_host_name|.
 OPENSSL_EXPORT const char *SSL_get_servername(const SSL *ssl, const int type);
 
 // SSL_get_servername_type, for a server, returns |TLSEXT_NAMETYPE_host_name|
 // if the client sent a hostname and -1 otherwise.
 OPENSSL_EXPORT int SSL_get_servername_type(const SSL *ssl);
 
 // SSL_CTX_set_tlsext_servername_callback configures |callback| to be called on
 // the server after ClientHello extensions have been parsed and returns one.
 // The callback may use |SSL_get_servername| to examine the server_name
 // extension and returns a |SSL_TLSEXT_ERR_*| value. The value of |arg| may be
 // set by calling |SSL_CTX_set_tlsext_servername_arg|.
 //
 // If the callback returns |SSL_TLSEXT_ERR_NOACK|, the server_name extension is
 // not acknowledged in the ServerHello. If the return value is
 // |SSL_TLSEXT_ERR_ALERT_FATAL|, then |*out_alert| is the alert to send,
 // defaulting to |SSL_AD_UNRECOGNIZED_NAME|. |SSL_TLSEXT_ERR_ALERT_WARNING| is
 // ignored and treated as |SSL_TLSEXT_ERR_OK|.
 OPENSSL_EXPORT int SSL_CTX_set_tlsext_servername_callback(
     SSL_CTX *ctx, int (*callback)(SSL *ssl, int *out_alert, void *arg));
 
 // SSL_CTX_set_tlsext_servername_arg sets the argument to the servername
 // callback and returns one. See |SSL_CTX_set_tlsext_servername_callback|.
 OPENSSL_EXPORT int SSL_CTX_set_tlsext_servername_arg(SSL_CTX *ctx, void *arg);
 
 // SSL_TLSEXT_ERR_* are values returned by some extension-related callbacks.
 #define SSL_TLSEXT_ERR_OK 0
 #define SSL_TLSEXT_ERR_ALERT_WARNING 1
 #define SSL_TLSEXT_ERR_ALERT_FATAL 2
 #define SSL_TLSEXT_ERR_NOACK 3
 
 // SSL_set_SSL_CTX changes |ssl|'s |SSL_CTX|. |ssl| will use the
 // certificate-related settings from |ctx|, and |SSL_get_SSL_CTX| will report
 // |ctx|. This function may be used during the callbacks registered by
 // |SSL_CTX_set_select_certificate_cb|,
 // |SSL_CTX_set_tlsext_servername_callback|, and |SSL_CTX_set_cert_cb| or when
 // the handshake is paused from them. It is typically used to switch
 // certificates based on SNI.
 //
 // Note the session cache and related settings will continue to use the initial
 // |SSL_CTX|. Callers should use |SSL_CTX_set_session_id_context| to partition
 // the session cache between different domains.
 //
 // TODO(davidben): Should other settings change after this call?
 OPENSSL_EXPORT SSL_CTX *SSL_set_SSL_CTX(SSL *ssl, SSL_CTX *ctx);
 
 
 // Application-layer protocol negotiation.
 //
 // The ALPN extension (RFC 7301) allows negotiating different application-layer
 // protocols over a single port. This is used, for example, to negotiate
 // HTTP/2.
 
 // SSL_CTX_set_alpn_protos sets the client ALPN protocol list on |ctx| to
 // |protos|. |protos| must be in wire-format (i.e. a series of non-empty, 8-bit
 // length-prefixed strings), or the empty string to disable ALPN. It returns
 // zero on success and one on failure. Configuring a non-empty string enables
 // ALPN on a client.
 //
 // WARNING: this function is dangerous because it breaks the usual return value
 // convention.
 OPENSSL_EXPORT int SSL_CTX_set_alpn_protos(SSL_CTX *ctx, const uint8_t *protos,
                                            size_t protos_len);
 
 // SSL_set_alpn_protos sets the client ALPN protocol list on |ssl| to |protos|.
 // |protos| must be in wire-format (i.e. a series of non-empty, 8-bit
 // length-prefixed strings), or the empty string to disable ALPN. It returns
 // zero on success and one on failure. Configuring a non-empty string enables
 // ALPN on a client.
 //
 // WARNING: this function is dangerous because it breaks the usual return value
 // convention.
 OPENSSL_EXPORT int SSL_set_alpn_protos(SSL *ssl, const uint8_t *protos,
                                        size_t protos_len);
 
 // SSL_CTX_set_alpn_select_cb sets a callback function on |ctx| that is called
 // during ClientHello processing in order to select an ALPN protocol from the
 // client's list of offered protocols. |SSL_select_next_proto| is an optional
 // utility function which may be useful in implementing this callback.
 //
 // The callback is passed a wire-format (i.e. a series of non-empty, 8-bit
 // length-prefixed strings) ALPN protocol list in |in|. To select a protocol,
 // the callback should set |*out| and |*out_len| to the selected protocol and
 // return |SSL_TLSEXT_ERR_OK| on success. It does not pass ownership of the
 // buffer, so |*out| should point to a static string, a buffer that outlives the
 // callback call, or the corresponding entry in |in|.
 //
 // If the server supports ALPN, but there are no protocols in common, the
 // callback should return |SSL_TLSEXT_ERR_ALERT_FATAL| to abort the connection
 // with a no_application_protocol alert.
 //
 // If the server does not support ALPN, it can return |SSL_TLSEXT_ERR_NOACK| to
 // continue the handshake without negotiating a protocol. This may be useful if
 // multiple server configurations share an |SSL_CTX|, only some of which have
 // ALPN protocols configured.
 //
 // |SSL_TLSEXT_ERR_ALERT_WARNING| is ignored and will be treated as
 // |SSL_TLSEXT_ERR_NOACK|.
 //
 // The callback will only be called if the client supports ALPN. Callers that
 // wish to require ALPN for all clients must check |SSL_get0_alpn_selected|
 // after the handshake. In QUIC connections, this is done automatically.
 //
 // The cipher suite is selected before negotiating ALPN. The callback may use
 // |SSL_get_pending_cipher| to query the cipher suite. This may be used to
 // implement HTTP/2's cipher suite constraints.
 OPENSSL_EXPORT void SSL_CTX_set_alpn_select_cb(
     SSL_CTX *ctx,
     int (*cb)(SSL *ssl, const uint8_t **out, uint8_t *out_len,
               const uint8_t *in, unsigned in_len, void *arg),
     void *arg);
 
 // SSL_get0_alpn_selected gets the selected ALPN protocol (if any) from |ssl|.
 // On return it sets |*out_data| to point to |*out_len| bytes of protocol name
 // (not including the leading length-prefix byte). If the server didn't respond
 // with a negotiated protocol then |*out_len| will be zero.
 OPENSSL_EXPORT void SSL_get0_alpn_selected(const SSL *ssl,
                                            const uint8_t **out_data,
                                            unsigned *out_len);
 
 // SSL_CTX_set_allow_unknown_alpn_protos configures client connections on |ctx|
 // to allow unknown ALPN protocols from the server. Otherwise, by default, the
 // client will require that the protocol be advertised in
 // |SSL_CTX_set_alpn_protos|.
 OPENSSL_EXPORT void SSL_CTX_set_allow_unknown_alpn_protos(SSL_CTX *ctx,
                                                           int enabled);
 
 
 // Application-layer protocol settings
 //
 // The ALPS extension (draft-vvv-tls-alps) allows exchanging application-layer
 // settings in the TLS handshake for applications negotiated with ALPN. Note
 // that, when ALPS is negotiated, the client and server each advertise their own
 // settings, so there are functions to both configure setting to send and query
 // received settings.
 
 // SSL_add_application_settings configures |ssl| to enable ALPS with ALPN
 // protocol |proto|, sending an ALPS value of |settings|. It returns one on
 // success and zero on error. If |proto| is negotiated via ALPN and the peer
 // supports ALPS, |settings| will be sent to the peer. The peer's ALPS value can
 // be retrieved with |SSL_get0_peer_application_settings|.
 //
 // On the client, this function should be called before the handshake, once for
 // each supported ALPN protocol which uses ALPS. |proto| must be included in the
 // client's ALPN configuration (see |SSL_CTX_set_alpn_protos| and
 // |SSL_set_alpn_protos|). On the server, ALPS can be preconfigured for each
 // protocol as in the client, or configuration can be deferred to the ALPN
 // callback (see |SSL_CTX_set_alpn_select_cb|), in which case only the selected
 // protocol needs to be configured.
 //
 // ALPS can be independently configured from 0-RTT, however changes in protocol
 // settings will fallback to 1-RTT to negotiate the new value, so it is
 // recommended for |settings| to be relatively stable.
 OPENSSL_EXPORT int SSL_add_application_settings(SSL *ssl, const uint8_t *proto,
                                                 size_t proto_len,
                                                 const uint8_t *settings,
                                                 size_t settings_len);
 
 // SSL_get0_peer_application_settings sets |*out_data| and |*out_len| to a
 // buffer containing the peer's ALPS value, or the empty string if ALPS was not
 // negotiated. Note an empty string could also indicate the peer sent an empty
 // settings value. Use |SSL_has_application_settings| to check if ALPS was
 // negotiated. The output buffer is owned by |ssl| and is valid until the next
 // time |ssl| is modified.
 OPENSSL_EXPORT void SSL_get0_peer_application_settings(const SSL *ssl,
                                                        const uint8_t **out_data,
                                                        size_t *out_len);
 
 // SSL_has_application_settings returns one if ALPS was negotiated on this
 // connection and zero otherwise.
 OPENSSL_EXPORT int SSL_has_application_settings(const SSL *ssl);
 
 // SSL_set_alps_use_new_codepoint configures whether to use the new ALPS
 // codepoint. By default, the old codepoint is used.
 OPENSSL_EXPORT void SSL_set_alps_use_new_codepoint(SSL *ssl, int use_new);
 
 
 // Certificate compression.
 //
 // Certificates in TLS 1.3 can be compressed (RFC 8879). BoringSSL supports this
 // as both a client and a server, but does not link against any specific
 // compression libraries in order to keep dependencies to a minimum. Instead,
 // hooks for compression and decompression can be installed in an |SSL_CTX| to
 // enable support.
 
 // ssl_cert_compression_func_t is a pointer to a function that performs
 // compression. It must write the compressed representation of |in| to |out|,
 // returning one on success and zero on error. The results of compressing
 // certificates are not cached internally. Implementations may wish to implement
 // their own cache if they expect it to be useful given the certificates that
 // they serve.
 typedef int (*ssl_cert_compression_func_t)(SSL *ssl, CBB *out,
                                            const uint8_t *in, size_t in_len);
 
 // ssl_cert_decompression_func_t is a pointer to a function that performs
 // decompression. The compressed data from the peer is passed as |in| and the
 // decompressed result must be exactly |uncompressed_len| bytes long. It returns
 // one on success, in which case |*out| must be set to the result of
 // decompressing |in|, or zero on error. Setting |*out| transfers ownership,
 // i.e. |CRYPTO_BUFFER_free| will be called on |*out| at some point in the
 // future. The results of decompressions are not cached internally.
 // Implementations may wish to implement their own cache if they expect it to be
 // useful.
 typedef int (*ssl_cert_decompression_func_t)(SSL *ssl, CRYPTO_BUFFER **out,
                                              size_t uncompressed_len,
                                              const uint8_t *in, size_t in_len);
 
 // SSL_CTX_add_cert_compression_alg registers a certificate compression
 // algorithm on |ctx| with ID |alg_id|. (The value of |alg_id| should be an IANA
 // assigned value and each can only be registered once.)
 //
 // One of the function pointers may be NULL to avoid having to implement both
 // sides of a compression algorithm if you're only going to use it in one
 // direction. In this case, the unimplemented direction acts like it was never
 // configured.
 //
 // For a server, algorithms are registered in preference order with the most
 // preferable first. It returns one on success or zero on error.
 OPENSSL_EXPORT int SSL_CTX_add_cert_compression_alg(
     SSL_CTX *ctx, uint16_t alg_id, ssl_cert_compression_func_t compress,
     ssl_cert_decompression_func_t decompress);
 
 
 // Next protocol negotiation.
 //
 // The NPN extension (draft-agl-tls-nextprotoneg-03) is the predecessor to ALPN
 // and deprecated in favor of it.
 
 // SSL_CTX_set_next_protos_advertised_cb sets a callback that is called when a
 // TLS server needs a list of supported protocols for Next Protocol Negotiation.
 //
 // If the callback wishes to advertise NPN to the client, it should return
 // |SSL_TLSEXT_ERR_OK| and then set |*out| and |*out_len| to describe to a
 // buffer containing a (possibly empty) list of supported protocols in wire
 // format. That is, each protocol is prefixed with a 1-byte length, then
 // concatenated. From there, the client will select a protocol, possibly one not
 // on the server's list. The caller can use |SSL_get0_next_proto_negotiated|
 // after the handshake completes to query the final protocol.
 //
 // The returned buffer must remain valid and unmodified for at least the
 // duration of the |SSL| operation (e.g. |SSL_do_handshake|) that triggered the
 // callback.
 //
 // If the caller wishes not to advertise NPN, it should return
 // |SSL_TLSEXT_ERR_NOACK|. No NPN extension will be included in the ServerHello,
 // and the TLS server will behave as if it does not implement NPN.
 OPENSSL_EXPORT void SSL_CTX_set_next_protos_advertised_cb(
     SSL_CTX *ctx,
     int (*cb)(SSL *ssl, const uint8_t **out, unsigned *out_len, void *arg),
     void *arg);
 
 // SSL_CTX_set_next_proto_select_cb sets a callback that is called when a client
 // needs to select a protocol from the server's provided list, passed in wire
 // format in |in_len| bytes from |in|. The callback can assume that |in| is
 // syntactically valid. |SSL_select_next_proto| is an optional utility function
 // which may be useful in implementing this callback.
 //
 // On success, the callback should return |SSL_TLSEXT_ERR_OK| and set |*out| and
 // |*out_len| to describe a buffer containing the selected protocol, or an
 // empty buffer to select no protocol. The returned buffer may point within
 // |in|, or it may point to some other buffer that remains valid and unmodified
 // for at least the duration of the |SSL| operation (e.g. |SSL_do_handshake|)
 // that triggered the callback.
 //
 // Returning any other value indicates a fatal error and will terminate the TLS
 // connection. To proceed without selecting a protocol, the callback must return
 // |SSL_TLSEXT_ERR_OK| and set |*out| and |*out_len| to an empty buffer. (E.g.
 // NULL and zero, respectively.)
 //
 // Configuring this callback enables NPN on a client. Although the callback can
 // then decline to negotiate a protocol, merely configuring the callback causes
 // the client to offer NPN in the ClientHello. Callers thus should not configure
 // this callback in TLS client contexts that are not intended to use NPN.
 OPENSSL_EXPORT void SSL_CTX_set_next_proto_select_cb(
     SSL_CTX *ctx,
     int (*cb)(SSL *ssl, uint8_t **out, uint8_t *out_len, const uint8_t *in,
               unsigned in_len, void *arg),
     void *arg);
 
 // SSL_get0_next_proto_negotiated sets |*out_data| and |*out_len| to point to
 // the client's requested protocol for this connection. If the client didn't
 // request any protocol, then |*out_len| is set to zero.
 //
 // Note that the client can request any protocol it chooses. The value returned
 // from this function need not be a member of the list of supported protocols
 // provided by the server.
 OPENSSL_EXPORT void SSL_get0_next_proto_negotiated(const SSL *ssl,
                                                    const uint8_t **out_data,
                                                    unsigned *out_len);
 
 // SSL_select_next_proto implements the standard protocol selection for either
 // ALPN servers or NPN clients. It is expected that this function is called from
 // the callback set by |SSL_CTX_set_alpn_select_cb| or
 // |SSL_CTX_set_next_proto_select_cb|.
 //
 // |peer| and |supported| contain the peer and locally-configured protocols,
 // respectively. This function finds the first protocol in |peer| which is also
 // in |supported|. If one was found, it sets |*out| and |*out_len| to point to
 // it and returns |OPENSSL_NPN_NEGOTIATED|. Otherwise, it returns
 // |OPENSSL_NPN_NO_OVERLAP| and sets |*out| and |*out_len| to the first
 // supported protocol.
 //
 // In ALPN, the server should only select protocols among those that the client
 // offered. Thus, if this function returns |OPENSSL_NPN_NO_OVERLAP|, the caller
 // should ignore |*out| and return |SSL_TLSEXT_ERR_ALERT_FATAL| from
 // |SSL_CTX_set_alpn_select_cb|'s callback to indicate there was no match.
 //
 // In NPN, the client may either select one of the server's protocols, or an
 // "opportunistic" protocol as described in Section 6 of
 // draft-agl-tls-nextprotoneg-03. When this function returns
 // |OPENSSL_NPN_NO_OVERLAP|, |*out| implicitly selects the first supported
 // protocol for use as the opportunistic protocol. The caller may use it,
 // ignore it and select a different opportunistic protocol, or ignore it and
 // select no protocol (empty string).
 //
 // |peer| and |supported| must be vectors of 8-bit, length-prefixed byte
 // strings. The length byte itself is not included in the length. A byte string
 // of length 0 is invalid. No byte string may be truncated. |supported| must be
 // non-empty; a caller that supports no ALPN/NPN protocols should skip
 // negotiating the extension, rather than calling this function. If any of these
 // preconditions do not hold, this function will return |OPENSSL_NPN_NO_OVERLAP|
 // and set |*out| and |*out_len| to an empty buffer for robustness, but callers
 // are not recommended to rely on this. An empty buffer is not a valid output
 // for |SSL_CTX_set_alpn_select_cb|'s callback.
 //
 // WARNING: |*out| and |*out_len| may alias either |peer| or |supported| and may
 // not be used after one of those buffers is modified or released. Additionally,
 // this function is not const-correct for compatibility reasons. Although |*out|
 // is a non-const pointer, callers may not modify the buffer though |*out|.
 OPENSSL_EXPORT int SSL_select_next_proto(uint8_t **out, uint8_t *out_len,
                                          const uint8_t *peer, unsigned peer_len,
                                          const uint8_t *supported,
                                          unsigned supported_len);
 
 #define OPENSSL_NPN_UNSUPPORTED 0
 #define OPENSSL_NPN_NEGOTIATED 1
 #define OPENSSL_NPN_NO_OVERLAP 2
 
 
 // Channel ID.
 //
 // See draft-balfanz-tls-channelid-01. This is an old, experimental mechanism
 // and should not be used in new code.
 
 // SSL_CTX_set_tls_channel_id_enabled configures whether connections associated
 // with |ctx| should enable Channel ID as a server.
 OPENSSL_EXPORT void SSL_CTX_set_tls_channel_id_enabled(SSL_CTX *ctx,
                                                        int enabled);
 
 // SSL_set_tls_channel_id_enabled configures whether |ssl| should enable Channel
 // ID as a server.
 OPENSSL_EXPORT void SSL_set_tls_channel_id_enabled(SSL *ssl, int enabled);
 
 // SSL_CTX_set1_tls_channel_id configures a TLS client to send a TLS Channel ID
 // to compatible servers. |private_key| must be a P-256 EC key. It returns one
 // on success and zero on error.
 OPENSSL_EXPORT int SSL_CTX_set1_tls_channel_id(SSL_CTX *ctx,
                                                EVP_PKEY *private_key);
 
 // SSL_set1_tls_channel_id configures a TLS client to send a TLS Channel ID to
 // compatible servers. |private_key| must be a P-256 EC key. It returns one on
 // success and zero on error.
 OPENSSL_EXPORT int SSL_set1_tls_channel_id(SSL *ssl, EVP_PKEY *private_key);
 
 // SSL_get_tls_channel_id gets the client's TLS Channel ID from a server |SSL|
 // and copies up to the first |max_out| bytes into |out|. The Channel ID
 // consists of the client's P-256 public key as an (x,y) pair where each is a
 // 32-byte, big-endian field element. It returns 0 if the client didn't offer a
 // Channel ID and the length of the complete Channel ID otherwise. This function
 // always returns zero if |ssl| is a client.
 OPENSSL_EXPORT size_t SSL_get_tls_channel_id(SSL *ssl, uint8_t *out,
                                              size_t max_out);
 
 
 // DTLS-SRTP.
 //
 // See RFC 5764.
 
 // srtp_protection_profile_st (aka |SRTP_PROTECTION_PROFILE|) is an SRTP
 // profile for use with the use_srtp extension.
 struct srtp_protection_profile_st {
   const char *name;
   unsigned long id;
 } /* SRTP_PROTECTION_PROFILE */;
 
 DEFINE_CONST_STACK_OF(SRTP_PROTECTION_PROFILE)
 
 // SRTP_* define constants for SRTP profiles.
 #define SRTP_AES128_CM_SHA1_80 0x0001
 #define SRTP_AES128_CM_SHA1_32 0x0002
 #define SRTP_AES128_F8_SHA1_80 0x0003
 #define SRTP_AES128_F8_SHA1_32 0x0004
 #define SRTP_NULL_SHA1_80 0x0005
 #define SRTP_NULL_SHA1_32 0x0006
 #define SRTP_AEAD_AES_128_GCM 0x0007
 #define SRTP_AEAD_AES_256_GCM 0x0008
 
 // SSL_CTX_set_srtp_profiles enables SRTP for all SSL objects created from
 // |ctx|. |profile| contains a colon-separated list of profile names. It returns
 // one on success and zero on failure.
 OPENSSL_EXPORT int SSL_CTX_set_srtp_profiles(SSL_CTX *ctx,
                                              const char *profiles);
 
 // SSL_set_srtp_profiles enables SRTP for |ssl|.  |profile| contains a
 // colon-separated list of profile names. It returns one on success and zero on
 // failure.
 OPENSSL_EXPORT int SSL_set_srtp_profiles(SSL *ssl, const char *profiles);
 
 // SSL_get_srtp_profiles returns the SRTP profiles supported by |ssl|.
 OPENSSL_EXPORT const STACK_OF(SRTP_PROTECTION_PROFILE) *SSL_get_srtp_profiles(
     const SSL *ssl);
 
 // SSL_get_selected_srtp_profile returns the selected SRTP profile, or NULL if
 // SRTP was not negotiated.
 OPENSSL_EXPORT const SRTP_PROTECTION_PROFILE *SSL_get_selected_srtp_profile(
     SSL *ssl);
 
 
 // Pre-shared keys.
 //
 // Connections may be configured with PSK (Pre-Shared Key) cipher suites. These
 // authenticate using out-of-band pre-shared keys rather than certificates. See
 // RFC 4279.
 //
 // This implementation uses NUL-terminated C strings for identities and identity
 // hints, so values with a NUL character are not supported. (RFC 4279 does not
 // specify the format of an identity.)
 
 // PSK_MAX_IDENTITY_LEN is the maximum supported length of a PSK identity,
 // excluding the NUL terminator.
 #define PSK_MAX_IDENTITY_LEN 128
 
 // PSK_MAX_PSK_LEN is the maximum supported length of a pre-shared key.
 #define PSK_MAX_PSK_LEN 256
 
 // SSL_CTX_set_psk_client_callback sets the callback to be called when PSK is
 // negotiated on the client. This callback must be set to enable PSK cipher
 // suites on the client.
 //
 // The callback is passed the identity hint in |hint| or NULL if none was
 // provided. It should select a PSK identity and write the identity and the
 // corresponding PSK to |identity| and |psk|, respectively. The identity is
 // written as a NUL-terminated C string of length (excluding the NUL terminator)
 // at most |max_identity_len|. The PSK's length must be at most |max_psk_len|.
 // The callback returns the length of the PSK or 0 if no suitable identity was
 // found.
 OPENSSL_EXPORT void SSL_CTX_set_psk_client_callback(
     SSL_CTX *ctx, unsigned (*cb)(SSL *ssl, const char *hint, char *identity,
                                  unsigned max_identity_len, uint8_t *psk,
                                  unsigned max_psk_len));
 
 // SSL_set_psk_client_callback sets the callback to be called when PSK is
 // negotiated on the client. This callback must be set to enable PSK cipher
 // suites on the client. See also |SSL_CTX_set_psk_client_callback|.
 OPENSSL_EXPORT void SSL_set_psk_client_callback(
     SSL *ssl, unsigned (*cb)(SSL *ssl, const char *hint, char *identity,
                              unsigned max_identity_len, uint8_t *psk,
                              unsigned max_psk_len));
 
 // SSL_CTX_set_psk_server_callback sets the callback to be called when PSK is
 // negotiated on the server. This callback must be set to enable PSK cipher
 // suites on the server.
 //
 // The callback is passed the identity in |identity|. It should write a PSK of
 // length at most |max_psk_len| to |psk| and return the number of bytes written
 // or zero if the PSK identity is unknown.
 OPENSSL_EXPORT void SSL_CTX_set_psk_server_callback(
     SSL_CTX *ctx, unsigned (*cb)(SSL *ssl, const char *identity, uint8_t *psk,
                                  unsigned max_psk_len));
 
 // SSL_set_psk_server_callback sets the callback to be called when PSK is
 // negotiated on the server. This callback must be set to enable PSK cipher
 // suites on the server. See also |SSL_CTX_set_psk_server_callback|.
 OPENSSL_EXPORT void SSL_set_psk_server_callback(
     SSL *ssl, unsigned (*cb)(SSL *ssl, const char *identity, uint8_t *psk,
                              unsigned max_psk_len));
 
 // SSL_CTX_use_psk_identity_hint configures server connections to advertise an
 // identity hint of |identity_hint|. It returns one on success and zero on
 // error.
 OPENSSL_EXPORT int SSL_CTX_use_psk_identity_hint(SSL_CTX *ctx,
                                                  const char *identity_hint);
 
 // SSL_use_psk_identity_hint configures server connections to advertise an
 // identity hint of |identity_hint|. It returns one on success and zero on
 // error.
 OPENSSL_EXPORT int SSL_use_psk_identity_hint(SSL *ssl,
                                              const char *identity_hint);
 
 // SSL_get_psk_identity_hint returns the PSK identity hint advertised for |ssl|
 // or NULL if there is none.
 OPENSSL_EXPORT const char *SSL_get_psk_identity_hint(const SSL *ssl);
 
 // SSL_get_psk_identity, after the handshake completes, returns the PSK identity
 // that was negotiated by |ssl| or NULL if PSK was not used.
 OPENSSL_EXPORT const char *SSL_get_psk_identity(const SSL *ssl);
 
 
 // Delegated credentials.
 //
 // Delegated credentials (RFC 9345) allow a TLS 1.3 endpoint to use its
 // certificate to issue new credentials for authentication. Once issued,
 // credentials can't be revoked. In order to mitigate the damage in case the
 // credential secret key is compromised, the credential is only valid for a
 // short time (days, hours, or even minutes).
 //
 // Currently only the authenticating side, as a server, is implemented. To
 // authenticate with delegated credentials, construct an |SSL_CREDENTIAL| with
 // |SSL_CREDENTIAL_new_delegated| and add it to the credential list. See also
 // |SSL_CTX_add1_credential|. Callers may configure a mix of delegated
 // credentials and X.509 credentials on the same |SSL| or |SSL_CTX| to support a
 // range of clients.
 
 // SSL_CREDENTIAL_new_delegated returns a new, empty delegated credential, or
 // NULL on error. Callers should release the result with |SSL_CREDENTIAL_free|
 // when done.
 //
 // Callers should configure a delegated credential, certificate chain and
 // private key on the credential, along with other properties, then add it with
 // |SSL_CTX_add1_credential|.
 OPENSSL_EXPORT SSL_CREDENTIAL *SSL_CREDENTIAL_new_delegated(void);
 
 // SSL_CREDENTIAL_set1_delegated_credential sets |cred|'s delegated credentials
 // structure to |dc|. It returns one on success and zero on error, including if
 // |dc| is malformed. This should be a DelegatedCredential structure, signed by
 // the end-entity certificate, as described in RFC 9345.
 OPENSSL_EXPORT int SSL_CREDENTIAL_set1_delegated_credential(
     SSL_CREDENTIAL *cred, CRYPTO_BUFFER *dc);
 
 
 // Password Authenticated Key Exchange (PAKE).
 //
 // Password Authenticated Key Exchange protocols allow client and server to
 // mutually authenticate one another using knowledge of a password or other
 // low-entropy secret. While the TLS 1.3 pre-shared key (PSK) mechanism can
 // authenticate a high-entropy secret, it cannot be used with low-entropy
 // secrets as the PSK binder values can be used to mount a dictionary attack on
 // a low-entropy PSK. Using TLS 1.3 with a PAKE limits an attacker to confirming
 // one password guess per handshake attempt.
 //
 // WARNING: The PAKE mode in TLS is not a general-purpose authentication scheme.
 // As the underlying secret is still low-entropy, callers must limit brute force
 // attacks across multiple connections, especially in multi-connection protocols
 // such as HTTP. The |error_limit| and |rate_limit| parameters in the functions
 // below may be used to implement this, provided the same |SSL_CREDENTIAL|
 // object is used across connections. Applications using multiple connections
 // should use the PAKE credential only once to authenticate a high-entropy
 // secret, e.g. exporting a PSK from |SSL_export_keying_material|, and use the
 // high-entropy secret for subsequent connections.
 //
 // TODO(crbug.com/369963041): Implement RFC 9258 so one can actually do that.
 //
 // WARNING: PAKE support in TLS is still experimental and may change as the
 // standard evolves. See
 // https://chris-wood.github.io/draft-bmw-tls-pake13/draft-bmw-tls-pake13.html
 //
 // Currently, only the SPAKE2PLUS_V1 named PAKE algorithm is implemented; see
 // https://chris-wood.github.io/draft-bmw-tls-pake13/draft-bmw-tls-pake13.html#section-8.1.
 
 // SSL_PAKE_SPAKE2PLUSV1 is the codepoint for SPAKE2PLUS_V1. See
 // https://chris-wood.github.io/draft-bmw-tls-pake13/draft-bmw-tls-pake13.html#name-named-pake-registry.
 #define SSL_PAKE_SPAKE2PLUSV1 0x7d96
 
 // SSL_spake2plusv1_register computes the values that the client (w0,
 // w1) and server (w0, registration_record) require to run SPAKE2+. These values
 // can be used when calling |SSL_CREDENTIAL_new_spake2plusv1_client| and
 // |SSL_CREDENTIAL_new_spake2plusv1_server|. The client and server identities
 // must match the values passed to those functions.
 //
 // Returns one on success and zero on error.
 OPENSSL_EXPORT int SSL_spake2plusv1_register(
     uint8_t out_w0[32], uint8_t out_w1[32], uint8_t out_registration_record[65],
     const uint8_t *password, size_t password_len,
     const uint8_t *client_identity, size_t client_identity_len,
     const uint8_t *server_identity, size_t server_identity_len);
 
 // SSL_CREDENTIAL_new_spake2plusv1_client creates a new |SSL_CREDENTIAL| that
 // authenticates using SPAKE2+. It is to be used with a TLS client.
 //
 // The |context|, |client_identity|, and |server_identity| fields serve to
 // identity the SPAKE2+ settings and both sides of a connection must agree on
 // these values. If |context| is |NULL|, a default value will be used.
 //
 // |error_limit| is the number of failed handshakes allowed on the credential.
 // After the limit is reached, using the credential will fail. Ideally this
 // value is set to 1. Setting it to a higher value allows an attacker to have
 // that many attempts at guessing the password using this |SSL_CREDENTIAL|.
 // (Assuming that multiple TLS connections are allowed.)
 //
 // |w0| and |w1| come from calling |SSL_spake2plusv1_register|.
 //
 // Unlike most |SSL_CREDENTIAL|s, PAKE client credentials must be the only
 // credential configured on the connection. BoringSSL does not currently support
 // configuring multiple PAKE credentials as a client, or configuring a mix of
 // PAKE and non-PAKE credentials. Once a PAKE credential is configured, the
 // connection will require the server to authenticate with the same secret, so a
 // successful connection then implies that the server supported the PAKE and
 // knew the password.
 OPENSSL_EXPORT SSL_CREDENTIAL *SSL_CREDENTIAL_new_spake2plusv1_client(
     const uint8_t *context, size_t context_len, const uint8_t *client_identity,
     size_t client_identity_len, const uint8_t *server_identity,
     size_t server_identity_len, uint32_t error_limit, const uint8_t *w0,
     size_t w0_len, const uint8_t *w1, size_t w1_len);
 
 // SSL_CREDENTIAL_new_spake2plusv1_server creates a new |SSL_CREDENTIAL| that
 // authenticates using SPAKE2+. It is to be used with a TLS server.
 //
 // The |context|, |client_identity|, and |server_identity| fields serve to
 // identity the SPAKE2+ settings and both sides of a connection must agree on
 // these values. If |context| is |NULL|, a default value will be used.
 //
 // |rate_limit| is the number of failed or unfinished handshakes allowed on the
 // credential. After the limit is reached, using the credential will fail.
 // Ideally this value is set to 1. Setting it to a higher value allows an
 // attacker to have that many attempts at guessing the password using this
 // |SSL_CREDENTIAL|. (Assuming that multiple TLS connections are allowed.)
 //
 // WARNING: |rate_limit| differs from the client's |error_limit| parameter.
 // Server PAKE credentials must temporarily deduct incomplete handshakes from
 // the limit, until the peer completes the handshake correctly. Thus
 // applications that use multiple connections in parallel may need a higher
 // limit, and thus higher attacker exposure, to avoid failures. Such
 // applications should instead use one PAKE-based connection to established a
 // high-entropy secret (e.g. with |SSL_export_keying_material|) instead of
 // repeating the PAKE exchange for each connection.
 //
 // |w0| and |registration_record| come from calling |SSL_spake2plusv1_register|,
 // which may be computed externally so that the server does not know the
 // password, or a password-equivalent secret.
 //
 // A server wishing to support a PAKE should install one of these credentials.
 // It is also possible to install certificate-based credentials, in which case
 // both PAKE and non-PAKE clients can be supported. However, if only a PAKE
 // credential is installed then the server knows that any successfully-connected
 // clients also knows the password. Otherwise, the server must be careful to
 // inspect the credential used for a connection before assuming that.
 OPENSSL_EXPORT SSL_CREDENTIAL *SSL_CREDENTIAL_new_spake2plusv1_server(
     const uint8_t *context, size_t context_len, const uint8_t *client_identity,
     size_t client_identity_len, const uint8_t *server_identity,
     size_t server_identity_len, uint32_t rate_limit, const uint8_t *w0,
     size_t w0_len, const uint8_t *registration_record,
     size_t registration_record_len);
 
 
 // QUIC integration.
 //
 // QUIC acts as an underlying transport for the TLS 1.3 handshake. The following
 // functions allow a QUIC implementation to serve as the underlying transport as
 // described in RFC 9001.
 //
 // When configured for QUIC, |SSL_do_handshake| will drive the handshake as
 // before, but it will not use the configured |BIO|. It will call functions on
 // |SSL_QUIC_METHOD| to configure secrets and send data. If data is needed from
 // the peer, it will return |SSL_ERROR_WANT_READ|. As the caller receives data
 // it can decrypt, it calls |SSL_provide_quic_data|. Subsequent
 // |SSL_do_handshake| calls will then consume that data and progress the
 // handshake. After the handshake is complete, the caller should continue to
 // call |SSL_provide_quic_data| for any post-handshake data, followed by
 // |SSL_process_quic_post_handshake| to process it. It is an error to call
 // |SSL_read| and |SSL_write| in QUIC.
 //
 // 0-RTT behaves similarly to |TLS_method|'s usual behavior. |SSL_do_handshake|
 // returns early as soon as the client (respectively, server) is allowed to send
 // 0-RTT (respectively, half-RTT) data. The caller should then call
 // |SSL_do_handshake| again to consume the remaining handshake messages and
 // confirm the handshake. As a client, |SSL_ERROR_EARLY_DATA_REJECTED| and
 // |SSL_reset_early_data_reject| behave as usual.
 //
 // See https://www.rfc-editor.org/rfc/rfc9001.html#section-4.1 for more details.
 //
 // To avoid DoS attacks, the QUIC implementation must limit the amount of data
 // being queued up. The implementation can call
 // |SSL_quic_max_handshake_flight_len| to get the maximum buffer length at each
 // encryption level.
 //
 // QUIC implementations must additionally configure transport parameters with
 // |SSL_set_quic_transport_params|. |SSL_get_peer_quic_transport_params| may be
 // used to query the value received from the peer. BoringSSL handles this
 // extension as an opaque byte string. The caller is responsible for serializing
 // and parsing them. See https://www.rfc-editor.org/rfc/rfc9000#section-7.4 for
 // details.
 //
 // QUIC additionally imposes restrictions on 0-RTT. In particular, the QUIC
 // transport layer requires that if a server accepts 0-RTT data, then the
 // transport parameters sent on the resumed connection must not lower any limits
 // compared to the transport parameters that the server sent on the connection
 // where the ticket for 0-RTT was issued. In effect, the server must remember
 // the transport parameters with the ticket. Application protocols running on
 // QUIC may impose similar restrictions, for example HTTP/3's restrictions on
 // SETTINGS frames.
 //
 // BoringSSL implements this check by doing a byte-for-byte comparison of an
 // opaque context passed in by the server. This context must be the same on the
 // connection where the ticket was issued and the connection where that ticket
 // is used for 0-RTT. If there is a mismatch, or the context was not set,
 // BoringSSL will reject early data (but not reject the resumption attempt).
 // This context is set via |SSL_set_quic_early_data_context| and should cover
 // both transport parameters and any application state.
 // |SSL_set_quic_early_data_context| must be called on the server with a
 // non-empty context if the server is to support 0-RTT in QUIC.
 //
 // BoringSSL does not perform any client-side checks on the transport
 // parameters received from a server that also accepted early data. It is up to
 // the caller to verify that the received transport parameters do not lower any
 // limits, and to close the QUIC connection if that is not the case. The same
 // holds for any application protocol state remembered for 0-RTT, e.g. HTTP/3
 // SETTINGS.
 
 // ssl_encryption_level_t represents an encryption level in TLS 1.3. Values in
 // this enum match the first 4 epochs used in DTLS 1.3 (section 6.1).
 enum ssl_encryption_level_t BORINGSSL_ENUM_INT {
   ssl_encryption_initial = 0,
   ssl_encryption_early_data = 1,
   ssl_encryption_handshake = 2,
   ssl_encryption_application = 3,
 };
 
 // ssl_quic_method_st (aka |SSL_QUIC_METHOD|) describes custom QUIC hooks.
 struct ssl_quic_method_st {
   // set_read_secret configures the read secret and cipher suite for the given
   // encryption level. It returns one on success and zero to terminate the
   // handshake with an error. It will be called at most once per encryption
   // level.
   //
   // BoringSSL will not release read keys before QUIC may use them. Once a level
   // has been initialized, QUIC may begin processing data from it. Handshake
   // data should be passed to |SSL_provide_quic_data| and application data (if
   // |level| is |ssl_encryption_early_data| or |ssl_encryption_application|) may
   // be processed according to the rules of the QUIC protocol.
   //
   // QUIC ACKs packets at the same encryption level they were received at,
   // except that client |ssl_encryption_early_data| (0-RTT) packets trigger
   // server |ssl_encryption_application| (1-RTT) ACKs. BoringSSL will always
   // install ACK-writing keys with |set_write_secret| before the packet-reading
   // keys with |set_read_secret|. This ensures the caller can always ACK any
   // packet it decrypts. Note this means the server installs 1-RTT write keys
   // before 0-RTT read keys.
   //
   // The converse is not true. An encryption level may be configured with write
   // secrets a roundtrip before the corresponding secrets for reading ACKs is
   // available.
   int (*set_read_secret)(SSL *ssl, enum ssl_encryption_level_t level,
                          const SSL_CIPHER *cipher, const uint8_t *secret,
                          size_t secret_len);
   // set_write_secret behaves like |set_read_secret| but configures the write
   // secret and cipher suite for the given encryption level. It will be called
   // at most once per encryption level.
   //
   // BoringSSL will not release write keys before QUIC may use them. If |level|
   // is |ssl_encryption_early_data| or |ssl_encryption_application|, QUIC may
   // begin sending application data at |level|. However, note that BoringSSL
   // configures server |ssl_encryption_application| write keys before the client
   // Finished. This allows QUIC to send half-RTT data, but the handshake is not
   // confirmed at this point and, if requesting client certificates, the client
   // is not yet authenticated.
   //
   // See |set_read_secret| for additional invariants between packets and their
   // ACKs.
   //
   // Note that, on 0-RTT reject, the |ssl_encryption_early_data| write secret
   // may use a different cipher suite from the other keys.
   int (*set_write_secret)(SSL *ssl, enum ssl_encryption_level_t level,
                           const SSL_CIPHER *cipher, const uint8_t *secret,
                           size_t secret_len);
   // add_handshake_data adds handshake data to the current flight at the given
   // encryption level. It returns one on success and zero on error.
   //
   // BoringSSL will pack data from a single encryption level together, but a
   // single handshake flight may include multiple encryption levels. Callers
   // should defer writing data to the network until |flush_flight| to better
   // pack QUIC packets into transport datagrams.
   //
   // If |level| is not |ssl_encryption_initial|, this function will not be
   // called before |level| is initialized with |set_write_secret|.
   int (*add_handshake_data)(SSL *ssl, enum ssl_encryption_level_t level,
                             const uint8_t *data, size_t len);
   // flush_flight is called when the current flight is complete and should be
   // written to the transport. Note a flight may contain data at several
   // encryption levels. It returns one on success and zero on error.
   int (*flush_flight)(SSL *ssl);
   // send_alert sends a fatal alert at the specified encryption level. It
   // returns one on success and zero on error.
   //
   // If |level| is not |ssl_encryption_initial|, this function will not be
   // called before |level| is initialized with |set_write_secret|.
   int (*send_alert)(SSL *ssl, enum ssl_encryption_level_t level, uint8_t alert);
 };
 
 // SSL_quic_max_handshake_flight_len returns returns the maximum number of bytes
 // that may be received at the given encryption level. This function should be
 // used to limit buffering in the QUIC implementation.
 //
 // See https://www.rfc-editor.org/rfc/rfc9000#section-7.5
 OPENSSL_EXPORT size_t SSL_quic_max_handshake_flight_len(
     const SSL *ssl, enum ssl_encryption_level_t level);
 
 // SSL_quic_read_level returns the current read encryption level.
 //
 // TODO(davidben): Is it still necessary to expose this function to callers?
 // QUICHE does not use it.
 OPENSSL_EXPORT enum ssl_encryption_level_t SSL_quic_read_level(const SSL *ssl);
 
 // SSL_quic_write_level returns the current write encryption level.
 //
 // TODO(davidben): Is it still necessary to expose this function to callers?
 // QUICHE does not use it.
 OPENSSL_EXPORT enum ssl_encryption_level_t SSL_quic_write_level(const SSL *ssl);
 
 // SSL_provide_quic_data provides data from QUIC at a particular encryption
 // level |level|. It returns one on success and zero on error. Note this
 // function will return zero if the handshake is not expecting data from |level|
 // at this time. The QUIC implementation should then close the connection with
 // an error.
 OPENSSL_EXPORT int SSL_provide_quic_data(SSL *ssl,
                                          enum ssl_encryption_level_t level,
                                          const uint8_t *data, size_t len);
 
 
 // SSL_process_quic_post_handshake processes any data that QUIC has provided
 // after the handshake has completed. This includes NewSessionTicket messages
 // sent by the server. It returns one on success and zero on error.
 OPENSSL_EXPORT int SSL_process_quic_post_handshake(SSL *ssl);
 
 // SSL_CTX_set_quic_method configures the QUIC hooks. This should only be
 // configured with a minimum version of TLS 1.3. |quic_method| must remain valid
 // for the lifetime of |ctx|. It returns one on success and zero on error.
 OPENSSL_EXPORT int SSL_CTX_set_quic_method(SSL_CTX *ctx,
                                            const SSL_QUIC_METHOD *quic_method);
 
 // SSL_set_quic_method configures the QUIC hooks. This should only be
 // configured with a minimum version of TLS 1.3. |quic_method| must remain valid
 // for the lifetime of |ssl|. It returns one on success and zero on error.
 OPENSSL_EXPORT int SSL_set_quic_method(SSL *ssl,
                                        const SSL_QUIC_METHOD *quic_method);
 
 // SSL_set_quic_transport_params configures |ssl| to send |params| (of length
 // |params_len|) in the quic_transport_parameters extension in either the
 // ClientHello or EncryptedExtensions handshake message. It is an error to set
 // transport parameters if |ssl| is not configured for QUIC. The buffer pointed
 // to by |params| only need be valid for the duration of the call to this
 // function. This function returns 1 on success and 0 on failure.
 OPENSSL_EXPORT int SSL_set_quic_transport_params(SSL *ssl,
                                                  const uint8_t *params,
                                                  size_t params_len);
 
 // SSL_get_peer_quic_transport_params provides the caller with the value of the
 // quic_transport_parameters extension sent by the peer. A pointer to the buffer
 // containing the TransportParameters will be put in |*out_params|, and its
 // length in |*params_len|. This buffer will be valid for the lifetime of the
 // |SSL|. If no params were received from the peer, |*out_params_len| will be 0.
 OPENSSL_EXPORT void SSL_get_peer_quic_transport_params(
     const SSL *ssl, const uint8_t **out_params, size_t *out_params_len);
 
 // SSL_set_quic_use_legacy_codepoint configures whether to use the legacy QUIC
 // extension codepoint 0xffa5 as opposed to the official value 57. Call with
 // |use_legacy| set to 1 to use 0xffa5 and call with 0 to use 57. By default,
 // the standard code point is used.
 OPENSSL_EXPORT void SSL_set_quic_use_legacy_codepoint(SSL *ssl, int use_legacy);
 
 // SSL_set_quic_early_data_context configures a context string in QUIC servers
 // for accepting early data. If a resumption connection offers early data, the
 // server will check if the value matches that of the connection which minted
 // the ticket. If not, resumption still succeeds but early data is rejected.
 // This should include all QUIC Transport Parameters except ones specified that
 // the client MUST NOT remember. This should also include any application
 // protocol-specific state. For HTTP/3, this should be the serialized server
 // SETTINGS frame and the QUIC Transport Parameters (except the stateless reset
 // token).
 //
 // This function may be called before |SSL_do_handshake| or during server
 // certificate selection. It returns 1 on success and 0 on failure.
 OPENSSL_EXPORT int SSL_set_quic_early_data_context(SSL *ssl,
                                                    const uint8_t *context,
                                                    size_t context_len);
 
 
 // Early data.
 //
 // WARNING: 0-RTT support in BoringSSL is currently experimental and not fully
 // implemented. It may cause interoperability or security failures when used.
 //
 // Early data, or 0-RTT, is a feature in TLS 1.3 which allows clients to send
 // data on the first flight during a resumption handshake. This can save a
 // round-trip in some application protocols.
 //
 // WARNING: A 0-RTT handshake has different security properties from normal
 // handshake, so it is off by default unless opted in. In particular, early data
 // is replayable by a network attacker. Callers must account for this when
 // sending or processing data before the handshake is confirmed. See RFC 8446
 // for more information.
 //
 // As a server, if early data is accepted, |SSL_do_handshake| will complete as
 // soon as the ClientHello is processed and server flight sent. |SSL_write| may
 // be used to send half-RTT data. |SSL_read| will consume early data and
 // transition to 1-RTT data as appropriate. Prior to the transition,
 // |SSL_in_init| will report the handshake is still in progress. Callers may use
 // it or |SSL_in_early_data| to defer or reject requests as needed.
 //
 // Early data as a client is more complex. If the offered session (see
 // |SSL_set_session|) is 0-RTT-capable, the handshake will return after sending
 // the ClientHello. The predicted peer certificates and ALPN protocol will be
 // available via the usual APIs. |SSL_write| will write early data, up to the
 // session's limit. Writes past this limit and |SSL_read| will complete the
 // handshake before continuing. Callers may also call |SSL_do_handshake| again
 // to complete the handshake sooner.
 //
 // If the server accepts early data, the handshake will succeed. |SSL_read| and
 // |SSL_write| will then act as in a 1-RTT handshake. The peer certificates and
 // ALPN protocol will be as predicted and need not be re-queried.
 //
 // If the server rejects early data, |SSL_do_handshake| (and thus |SSL_read| and
 // |SSL_write|) will then fail with |SSL_get_error| returning
 // |SSL_ERROR_EARLY_DATA_REJECTED|. The caller should treat this as a connection
 // error and most likely perform a high-level retry. Note the server may still
 // have processed the early data due to attacker replays.
 //
 // To then continue the handshake on the original connection, use
 // |SSL_reset_early_data_reject|. The connection will then behave as one which
 // had not yet completed the handshake. This allows a faster retry than making a
 // fresh connection. |SSL_do_handshake| will complete the full handshake,
 // possibly resulting in different peer certificates, ALPN protocol, and other
 // properties. The caller must disregard any values from before the reset and
 // query again.
 //
 // Finally, to implement the fallback described in RFC 8446 appendix D.3, retry
 // on a fresh connection without 0-RTT if the handshake fails with
 // |SSL_R_WRONG_VERSION_ON_EARLY_DATA|.
 
 // SSL_CTX_set_early_data_enabled sets whether early data is allowed to be used
 // with resumptions using |ctx|.
 OPENSSL_EXPORT void SSL_CTX_set_early_data_enabled(SSL_CTX *ctx, int enabled);
 
 // SSL_set_early_data_enabled sets whether early data is allowed to be used
 // with resumptions using |ssl|. See |SSL_CTX_set_early_data_enabled| for more
 // information.
 OPENSSL_EXPORT void SSL_set_early_data_enabled(SSL *ssl, int enabled);
 
 // SSL_in_early_data returns one if |ssl| has a pending handshake that has
 // progressed enough to send or receive early data. Clients may call |SSL_write|
 // to send early data, but |SSL_read| will complete the handshake before
 // accepting application data. Servers may call |SSL_read| to read early data
 // and |SSL_write| to send half-RTT data.
 OPENSSL_EXPORT int SSL_in_early_data(const SSL *ssl);
 
 // SSL_SESSION_early_data_capable returns whether early data would have been
 // attempted with |session| if enabled.
 OPENSSL_EXPORT int SSL_SESSION_early_data_capable(const SSL_SESSION *session);
 
 // SSL_SESSION_copy_without_early_data returns a copy of |session| with early
 // data disabled. If |session| already does not support early data, it returns
 // |session| with the reference count increased. The caller takes ownership of
 // the result and must release it with |SSL_SESSION_free|.
 //
 // This function may be used on the client to clear early data support from
 // existing sessions when the server rejects early data. In particular,
 // |SSL_R_WRONG_VERSION_ON_EARLY_DATA| requires a fresh connection to retry, and
 // the client would not want 0-RTT enabled for the next connection attempt.
 OPENSSL_EXPORT SSL_SESSION *SSL_SESSION_copy_without_early_data(
     SSL_SESSION *session);
 
 // SSL_early_data_accepted returns whether early data was accepted on the
 // handshake performed by |ssl|.
 OPENSSL_EXPORT int SSL_early_data_accepted(const SSL *ssl);
 
 // SSL_reset_early_data_reject resets |ssl| after an early data reject. All
 // 0-RTT state is discarded, including any pending |SSL_write| calls. The caller
 // should treat |ssl| as a logically fresh connection, usually by driving the
 // handshake to completion using |SSL_do_handshake|.
 //
 // It is an error to call this function on an |SSL| object that is not signaling
 // |SSL_ERROR_EARLY_DATA_REJECTED|.
 OPENSSL_EXPORT void SSL_reset_early_data_reject(SSL *ssl);
 
 // SSL_get_ticket_age_skew returns the difference, in seconds, between the
 // client-sent ticket age and the server-computed value in TLS 1.3 server
 // connections which resumed a session.
 OPENSSL_EXPORT int32_t SSL_get_ticket_age_skew(const SSL *ssl);
 
 // An ssl_early_data_reason_t describes why 0-RTT was accepted or rejected.
 // These values are persisted to logs. Entries should not be renumbered and
 // numeric values should never be reused.
 enum ssl_early_data_reason_t BORINGSSL_ENUM_INT {
   // The handshake has not progressed far enough for the 0-RTT status to be
   // known.
   ssl_early_data_unknown = 0,
   // 0-RTT is disabled for this connection.
   ssl_early_data_disabled = 1,
   // 0-RTT was accepted.
   ssl_early_data_accepted = 2,
   // The negotiated protocol version does not support 0-RTT.
   ssl_early_data_protocol_version = 3,
   // The peer declined to offer or accept 0-RTT for an unknown reason.
   ssl_early_data_peer_declined = 4,
   // The client did not offer a session.
   ssl_early_data_no_session_offered = 5,
   // The server declined to resume the session.
   ssl_early_data_session_not_resumed = 6,
   // The session does not support 0-RTT.
   ssl_early_data_unsupported_for_session = 7,
   // The server sent a HelloRetryRequest.
   ssl_early_data_hello_retry_request = 8,
   // The negotiated ALPN protocol did not match the session.
   ssl_early_data_alpn_mismatch = 9,
   // The connection negotiated Channel ID, which is incompatible with 0-RTT.
   ssl_early_data_channel_id = 10,
   // Value 11 is reserved. (It has historically |ssl_early_data_token_binding|.)
   // The client and server ticket age were too far apart.
   ssl_early_data_ticket_age_skew = 12,
   // QUIC parameters differ between this connection and the original.
   ssl_early_data_quic_parameter_mismatch = 13,
   // The application settings did not match the session.
   ssl_early_data_alps_mismatch = 14,
   // The value of the largest entry.
   ssl_early_data_reason_max_value = ssl_early_data_alps_mismatch,
 };
 
 // SSL_get_early_data_reason returns details why 0-RTT was accepted or rejected
 // on |ssl|. This is primarily useful on the server.
 OPENSSL_EXPORT enum ssl_early_data_reason_t SSL_get_early_data_reason(
     const SSL *ssl);
 
 // SSL_early_data_reason_string returns a string representation for |reason|, or
 // NULL if |reason| is unknown. This function may be used for logging.
 OPENSSL_EXPORT const char *SSL_early_data_reason_string(
     enum ssl_early_data_reason_t reason);
 
 
 // Encrypted ClientHello.
 //
 // ECH is a mechanism for encrypting the entire ClientHello message in TLS 1.3.
 // This can prevent observers from seeing cleartext information about the
 // connection, such as the server_name extension.
 //
 // By default, BoringSSL will treat the server name, session ticket, and client
 // certificate as secret, but most other parameters, such as the ALPN protocol
 // list will be treated as public and sent in the cleartext ClientHello. Other
 // APIs may be added for applications with different secrecy requirements.
 //
 // ECH support in BoringSSL is still experimental and under development.
 //
 // See https://tools.ietf.org/html/draft-ietf-tls-esni-13.
 
 // SSL_set_enable_ech_grease configures whether the client will send a GREASE
 // ECH extension when no supported ECHConfig is available.
 OPENSSL_EXPORT void SSL_set_enable_ech_grease(SSL *ssl, int enable);
 
 // SSL_set1_ech_config_list configures |ssl| to, as a client, offer ECH with the
 // specified configuration. |ech_config_list| should contain a serialized
 // ECHConfigList structure. It returns one on success and zero on error.
 //
 // This function returns an error if the input is malformed. If the input is
 // valid but none of the ECHConfigs implement supported parameters, it will
 // return success and proceed without ECH.
 //
 // If a supported ECHConfig is found, |ssl| will encrypt the true ClientHello
 // parameters. If the server cannot decrypt it, e.g. due to a key mismatch, ECH
 // has a recovery flow. |ssl| will handshake using the cleartext parameters,
 // including a public name in the ECHConfig. If using
 // |SSL_CTX_set_custom_verify|, callers should use |SSL_get0_ech_name_override|
 // to verify the certificate with the public name. If using the built-in
 // verifier, the |X509_STORE_CTX| will be configured automatically.
 //
 // If no other errors are found in this handshake, it will fail with
 // |SSL_R_ECH_REJECTED|. Since it didn't use the true parameters, the connection
 // cannot be used for application data. Instead, callers should handle this
 // error by calling |SSL_get0_ech_retry_configs| and retrying the connection
 // with updated ECH parameters. If the retry also fails with
 // |SSL_R_ECH_REJECTED|, the caller should report a connection failure.
 OPENSSL_EXPORT int SSL_set1_ech_config_list(SSL *ssl,
                                             const uint8_t *ech_config_list,
                                             size_t ech_config_list_len);
 
 // SSL_get0_ech_name_override, if |ssl| is a client and the server rejected ECH,
 // sets |*out_name| and |*out_name_len| to point to a buffer containing the ECH
 // public name. Otherwise, the buffer will be empty.
 //
 // When offering ECH as a client, this function should be called during the
 // certificate verification callback (see |SSL_CTX_set_custom_verify|). If
 // |*out_name_len| is non-zero, the caller should verify the certificate against
 // the result, interpreted as a DNS name, rather than the true server name. In
 // this case, the handshake will never succeed and is only used to authenticate
 // retry configs. See also |SSL_get0_ech_retry_configs|.
 OPENSSL_EXPORT void SSL_get0_ech_name_override(const SSL *ssl,
                                                const char **out_name,
                                                size_t *out_name_len);
 
 // SSL_get0_ech_retry_configs sets |*out_retry_configs| and
 // |*out_retry_configs_len| to a buffer containing a serialized ECHConfigList.
 // If the server did not provide an ECHConfigList, |*out_retry_configs_len| will
 // be zero.
 //
 // When handling an |SSL_R_ECH_REJECTED| error code as a client, callers should
 // use this function to recover from potential key mismatches. If the result is
 // non-empty, the caller should retry the connection, passing this buffer to
 // |SSL_set1_ech_config_list|. If the result is empty, the server has rolled
 // back ECH support, and the caller should retry without ECH.
 //
 // This function must only be called in response to an |SSL_R_ECH_REJECTED|
 // error code. Calling this function on |ssl|s that have not authenticated the
 // rejection handshake will assert in debug builds and otherwise return an
 // unparsable list.
 OPENSSL_EXPORT void SSL_get0_ech_retry_configs(
     const SSL *ssl, const uint8_t **out_retry_configs,
     size_t *out_retry_configs_len);
 
 // SSL_marshal_ech_config constructs a new serialized ECHConfig. On success, it
 // sets |*out| to a newly-allocated buffer containing the result and |*out_len|
 // to the size of the buffer. The caller must call |OPENSSL_free| on |*out| to
 // release the memory. On failure, it returns zero.
 //
 // The |config_id| field is a single byte identifier for the ECHConfig. Reusing
 // config IDs is allowed, but if multiple ECHConfigs with the same config ID are
 // active at a time, server load may increase. See
 // |SSL_ECH_KEYS_has_duplicate_config_id|.
 //
 // The public key and KEM algorithm are taken from |key|. |public_name| is the
 // DNS name used to authenticate the recovery flow. |max_name_len| should be the
 // length of the longest name in the ECHConfig's anonymity set and influences
 // client padding decisions.
 OPENSSL_EXPORT int SSL_marshal_ech_config(uint8_t **out, size_t *out_len,
                                           uint8_t config_id,
                                           const EVP_HPKE_KEY *key,
                                           const char *public_name,
                                           size_t max_name_len);
 
 // SSL_ECH_KEYS_new returns a newly-allocated |SSL_ECH_KEYS| or NULL on error.
 OPENSSL_EXPORT SSL_ECH_KEYS *SSL_ECH_KEYS_new(void);
 
 // SSL_ECH_KEYS_up_ref increments the reference count of |keys|.
 OPENSSL_EXPORT void SSL_ECH_KEYS_up_ref(SSL_ECH_KEYS *keys);
 
 // SSL_ECH_KEYS_free releases memory associated with |keys|.
 OPENSSL_EXPORT void SSL_ECH_KEYS_free(SSL_ECH_KEYS *keys);
 
 // SSL_ECH_KEYS_add decodes |ech_config| as an ECHConfig and appends it with
 // |key| to |keys|. If |is_retry_config| is non-zero, this config will be
 // returned to the client on configuration mismatch. It returns one on success
 // and zero on error.
 //
 // This function should be called successively to register each ECHConfig in
 // decreasing order of preference. This configuration must be completed before
 // setting |keys| on an |SSL_CTX| with |SSL_CTX_set1_ech_keys|. After that
 // point, |keys| is immutable; no more ECHConfig values may be added.
 //
 // See also |SSL_CTX_set1_ech_keys|.
 OPENSSL_EXPORT int SSL_ECH_KEYS_add(SSL_ECH_KEYS *keys, int is_retry_config,
                                     const uint8_t *ech_config,
                                     size_t ech_config_len,
                                     const EVP_HPKE_KEY *key);
 
 // SSL_ECH_KEYS_has_duplicate_config_id returns one if |keys| has duplicate
 // config IDs or zero otherwise. Duplicate config IDs still work, but may
 // increase server load due to trial decryption.
 OPENSSL_EXPORT int SSL_ECH_KEYS_has_duplicate_config_id(
     const SSL_ECH_KEYS *keys);
 
 // SSL_ECH_KEYS_marshal_retry_configs serializes the retry configs in |keys| as
 // an ECHConfigList. On success, it sets |*out| to a newly-allocated buffer
 // containing the result and |*out_len| to the size of the buffer. The caller
 // must call |OPENSSL_free| on |*out| to release the memory. On failure, it
 // returns zero.
 //
 // This output may be advertised to clients in DNS.
 OPENSSL_EXPORT int SSL_ECH_KEYS_marshal_retry_configs(const SSL_ECH_KEYS *keys,
                                                       uint8_t **out,
                                                       size_t *out_len);
 
 // SSL_CTX_set1_ech_keys configures |ctx| to use |keys| to decrypt encrypted
 // ClientHellos. It returns one on success, and zero on failure. If |keys| does
 // not contain any retry configs, this function will fail. Retry configs are
 // marked as such when they are added to |keys| with |SSL_ECH_KEYS_add|.
 //
 // Once |keys| has been passed to this function, it is immutable. Unlike most
 // |SSL_CTX| configuration functions, this function may be called even if |ctx|
 // already has associated connections on multiple threads. This may be used to
 // rotate keys in a long-lived server process.
 //
 // The configured ECHConfig values should also be advertised out-of-band via DNS
 // (see draft-ietf-dnsop-svcb-https). Before advertising an ECHConfig in DNS,
 // deployments should ensure all instances of the service are configured with
 // the ECHConfig and corresponding private key.
 //
 // Only the most recent fully-deployed ECHConfigs should be advertised in DNS.
 // |keys| may contain a newer set if those ECHConfigs are mid-deployment. It
 // should also contain older sets, until the DNS change has rolled out and the
 // old records have expired from caches.
 //
 // If there is a mismatch, |SSL| objects associated with |ctx| will complete the
 // handshake using the cleartext ClientHello and send updated ECHConfig values
 // to the client. The client will then retry to recover, but with a latency
 // penalty. This recovery flow depends on the public name in the ECHConfig.
 // Before advertising an ECHConfig in DNS, deployments must ensure all instances
 // of the service can present a valid certificate for the public name.
 //
 // BoringSSL negotiates ECH before certificate selection callbacks are called,
 // including |SSL_CTX_set_select_certificate_cb|. If ECH is negotiated, the
 // reported |SSL_CLIENT_HELLO| structure and |SSL_get_servername| function will
 // transparently reflect the inner ClientHello. Callers should select parameters
 // based on these values to correctly handle ECH as well as the recovery flow.
 OPENSSL_EXPORT int SSL_CTX_set1_ech_keys(SSL_CTX *ctx, SSL_ECH_KEYS *keys);
 
 // SSL_ech_accepted returns one if |ssl| negotiated ECH and zero otherwise.
 OPENSSL_EXPORT int SSL_ech_accepted(const SSL *ssl);
 
 
 // Alerts.
 //
 // TLS uses alerts to signal error conditions. Alerts have a type (warning or
 // fatal) and description. OpenSSL internally handles fatal alerts with
 // dedicated error codes (see |SSL_AD_REASON_OFFSET|). Except for close_notify,
 // warning alerts are silently ignored and may only be surfaced with
 // |SSL_CTX_set_info_callback|.
 
 // SSL_AD_REASON_OFFSET is the offset between error reasons and |SSL_AD_*|
 // values. Any error code under |ERR_LIB_SSL| with an error reason above this
 // value corresponds to an alert description. Consumers may add or subtract
 // |SSL_AD_REASON_OFFSET| to convert between them.
 //
 // make_errors.go reserves error codes above 1000 for manually-assigned errors.
 // This value must be kept in sync with reservedReasonCode in make_errors.h
 #define SSL_AD_REASON_OFFSET 1000
 
 // SSL_AD_* are alert descriptions.
 #define SSL_AD_CLOSE_NOTIFY SSL3_AD_CLOSE_NOTIFY
 #define SSL_AD_UNEXPECTED_MESSAGE SSL3_AD_UNEXPECTED_MESSAGE
 #define SSL_AD_BAD_RECORD_MAC SSL3_AD_BAD_RECORD_MAC
 #define SSL_AD_DECRYPTION_FAILED TLS1_AD_DECRYPTION_FAILED
 #define SSL_AD_RECORD_OVERFLOW TLS1_AD_RECORD_OVERFLOW
 #define SSL_AD_DECOMPRESSION_FAILURE SSL3_AD_DECOMPRESSION_FAILURE
 #define SSL_AD_HANDSHAKE_FAILURE SSL3_AD_HANDSHAKE_FAILURE
 #define SSL_AD_NO_CERTIFICATE SSL3_AD_NO_CERTIFICATE  // Legacy SSL 3.0 value
 #define SSL_AD_BAD_CERTIFICATE SSL3_AD_BAD_CERTIFICATE
 #define SSL_AD_UNSUPPORTED_CERTIFICATE SSL3_AD_UNSUPPORTED_CERTIFICATE
 #define SSL_AD_CERTIFICATE_REVOKED SSL3_AD_CERTIFICATE_REVOKED
 #define SSL_AD_CERTIFICATE_EXPIRED SSL3_AD_CERTIFICATE_EXPIRED
 #define SSL_AD_CERTIFICATE_UNKNOWN SSL3_AD_CERTIFICATE_UNKNOWN
 #define SSL_AD_ILLEGAL_PARAMETER SSL3_AD_ILLEGAL_PARAMETER
 #define SSL_AD_UNKNOWN_CA TLS1_AD_UNKNOWN_CA
 #define SSL_AD_ACCESS_DENIED TLS1_AD_ACCESS_DENIED
 #define SSL_AD_DECODE_ERROR TLS1_AD_DECODE_ERROR
 #define SSL_AD_DECRYPT_ERROR TLS1_AD_DECRYPT_ERROR
 #define SSL_AD_EXPORT_RESTRICTION TLS1_AD_EXPORT_RESTRICTION
 #define SSL_AD_PROTOCOL_VERSION TLS1_AD_PROTOCOL_VERSION
 #define SSL_AD_INSUFFICIENT_SECURITY TLS1_AD_INSUFFICIENT_SECURITY
 #define SSL_AD_INTERNAL_ERROR TLS1_AD_INTERNAL_ERROR
 #define SSL_AD_INAPPROPRIATE_FALLBACK SSL3_AD_INAPPROPRIATE_FALLBACK
 #define SSL_AD_USER_CANCELLED TLS1_AD_USER_CANCELLED
 #define SSL_AD_NO_RENEGOTIATION TLS1_AD_NO_RENEGOTIATION
 #define SSL_AD_MISSING_EXTENSION TLS1_AD_MISSING_EXTENSION
 #define SSL_AD_UNSUPPORTED_EXTENSION TLS1_AD_UNSUPPORTED_EXTENSION
 #define SSL_AD_CERTIFICATE_UNOBTAINABLE TLS1_AD_CERTIFICATE_UNOBTAINABLE
 #define SSL_AD_UNRECOGNIZED_NAME TLS1_AD_UNRECOGNIZED_NAME
 #define SSL_AD_BAD_CERTIFICATE_STATUS_RESPONSE \
   TLS1_AD_BAD_CERTIFICATE_STATUS_RESPONSE
 #define SSL_AD_BAD_CERTIFICATE_HASH_VALUE TLS1_AD_BAD_CERTIFICATE_HASH_VALUE
 #define SSL_AD_UNKNOWN_PSK_IDENTITY TLS1_AD_UNKNOWN_PSK_IDENTITY
 #define SSL_AD_CERTIFICATE_REQUIRED TLS1_AD_CERTIFICATE_REQUIRED
 #define SSL_AD_NO_APPLICATION_PROTOCOL TLS1_AD_NO_APPLICATION_PROTOCOL
 #define SSL_AD_ECH_REQUIRED TLS1_AD_ECH_REQUIRED
 
 // SSL_alert_type_string_long returns a string description of |value| as an
 // alert type (warning or fatal).
 OPENSSL_EXPORT const char *SSL_alert_type_string_long(int value);
 
 // SSL_alert_desc_string_long returns a string description of |value| as an
 // alert description or "unknown" if unknown.
 OPENSSL_EXPORT const char *SSL_alert_desc_string_long(int value);
 
 // SSL_send_fatal_alert sends a fatal alert over |ssl| of the specified type,
 // which should be one of the |SSL_AD_*| constants. It returns one on success
 // and <= 0 on error. The caller should pass the return value into
 // |SSL_get_error| to determine how to proceed. Once this function has been
 // called, future calls to |SSL_write| will fail.
 //
 // If retrying a failed operation due to |SSL_ERROR_WANT_WRITE|, subsequent
 // calls must use the same |alert| parameter.
 OPENSSL_EXPORT int SSL_send_fatal_alert(SSL *ssl, uint8_t alert);
 
 
 // ex_data functions.
 //
 // See |ex_data.h| for details.
 
 OPENSSL_EXPORT int SSL_set_ex_data(SSL *ssl, int idx, void *data);
 OPENSSL_EXPORT void *SSL_get_ex_data(const SSL *ssl, int idx);
 OPENSSL_EXPORT int SSL_get_ex_new_index(long argl, void *argp,
                                         CRYPTO_EX_unused *unused,
                                         CRYPTO_EX_dup *dup_unused,
                                         CRYPTO_EX_free *free_func);
 
 OPENSSL_EXPORT int SSL_SESSION_set_ex_data(SSL_SESSION *session, int idx,
                                            void *data);
 OPENSSL_EXPORT void *SSL_SESSION_get_ex_data(const SSL_SESSION *session,
                                              int idx);
 OPENSSL_EXPORT int SSL_SESSION_get_ex_new_index(long argl, void *argp,
                                                 CRYPTO_EX_unused *unused,
                                                 CRYPTO_EX_dup *dup_unused,
                                                 CRYPTO_EX_free *free_func);
 
 OPENSSL_EXPORT int SSL_CTX_set_ex_data(SSL_CTX *ctx, int idx, void *data);
 OPENSSL_EXPORT void *SSL_CTX_get_ex_data(const SSL_CTX *ctx, int idx);
 OPENSSL_EXPORT int SSL_CTX_get_ex_new_index(long argl, void *argp,
                                             CRYPTO_EX_unused *unused,
                                             CRYPTO_EX_dup *dup_unused,
                                             CRYPTO_EX_free *free_func);
 
 OPENSSL_EXPORT int SSL_CREDENTIAL_set_ex_data(SSL_CREDENTIAL *cred, int idx,
                                               void *data);
 OPENSSL_EXPORT void *SSL_CREDENTIAL_get_ex_data(const SSL_CREDENTIAL *cred,
                                                 int idx);
 OPENSSL_EXPORT int SSL_CREDENTIAL_get_ex_new_index(long argl, void *argp,
                                                    CRYPTO_EX_unused *unused,
                                                    CRYPTO_EX_dup *dup_unused,
                                                    CRYPTO_EX_free *free_func);
 
 
 // Low-level record-layer state.
 
 // SSL_get_ivs sets |*out_iv_len| to the length of the IVs for the ciphers
 // underlying |ssl| and sets |*out_read_iv| and |*out_write_iv| to point to the
 // current IVs for the read and write directions. This is only meaningful for
 // connections with implicit IVs (i.e. CBC mode with TLS 1.0).
 //
 // It returns one on success or zero on error.
 OPENSSL_EXPORT int SSL_get_ivs(const SSL *ssl, const uint8_t **out_read_iv,
                                const uint8_t **out_write_iv,
                                size_t *out_iv_len);
 
 // SSL_get_key_block_len returns the length of |ssl|'s key block, for TLS 1.2
 // and below. It is an error to call this function during a handshake, or if
 // |ssl| negotiated TLS 1.3.
 OPENSSL_EXPORT size_t SSL_get_key_block_len(const SSL *ssl);
 
 // SSL_generate_key_block generates |out_len| bytes of key material for |ssl|'s
 // current connection state, for TLS 1.2 and below. It is an error to call this
 // function during a handshake, or if |ssl| negotiated TLS 1.3.
 OPENSSL_EXPORT int SSL_generate_key_block(const SSL *ssl, uint8_t *out,
                                           size_t out_len);
 
 // SSL_get_read_sequence returns, in TLS, the expected sequence number of the
 // next incoming record in the current epoch.
 //
 // TODO(crbug.com/42290608): In DTLS, it returns the maximum sequence number
 // received in the current epoch (for some notion of "current" specific to
 // BoringSSL) and includes the epoch number in the two most significant bytes,
 // but this is deprecated. Use |SSL_get_dtls_read_sequence| instead.
 OPENSSL_EXPORT uint64_t SSL_get_read_sequence(const SSL *ssl);
 
 // SSL_get_write_sequence returns the sequence number of the next outgoing
 // record in the current epoch.
 //
 // TODO(crbug.com/42290608): In DTLS, it includes the epoch number in the two
 // most significant bytes, but this is deprecated. Use
 // |SSL_get_dtls_write_sequence| instead.
 OPENSSL_EXPORT uint64_t SSL_get_write_sequence(const SSL *ssl);
 
 // SSL_CTX_set_record_protocol_version returns whether |version| is zero.
 OPENSSL_EXPORT int SSL_CTX_set_record_protocol_version(SSL_CTX *ctx,
                                                        int version);
 
 // SSL_is_dtls_handshake_idle returns one |ssl|'s handshake is idle and zero if
 // it is busy. The handshake is considered idle if all of the following are
 // true:
 //
 // - |ssl| is not mid handshake or post-handshake transaction.
 // - In DTLS 1.3, all sent handshake messages have been acknowledged. That is,
 //   |ssl| does not have data to retransmit.
 // - All received handshake data has been processed. That is, |ssl| has no
 //   buffered partial or out-of-order messages.
 //
 // If any condition is false, the handshake is considered busy. If this function
 // reports the handshake is busy, it is expected that the handshake will become
 // idle after short timers and a few roundtrips of successful communication.
 // However, this is not guaranteed if, e.g., the peer misbehaves or sends many
 // KeyUpdates.
 //
 // WARNING: In DTLS 1.3, this function may return one while multiple active read
 // epochs exist in |ssl|.
 //
 // WARNING: In DTLS 1.2 (or earlier), if |ssl| is the role that speaks last, it
 // retains its final flight for retransmission in case of loss. There is no
 // explicit protocol signal for when this completes, though after receiving
 // application data and/or a timeout it is likely that this is no longer needed.
 // BoringSSL does not currently evaluate either condition and leaves it it to
 // the caller to determine whether this is now unnecessary. This applies when
 // |ssl| is a server for full handshakes and when |ssl| is a client for full
 // handshakes.
 OPENSSL_EXPORT int SSL_is_dtls_handshake_idle(const SSL *ssl);
 
 // SSL_get_dtls_handshake_read_seq returns the 16-bit sequence number of the
 // next DTLS handshake message to be read, or 0x10000 if handshake message
 // 0xffff (the maximum) has already been read.
 OPENSSL_EXPORT uint32_t SSL_get_dtls_handshake_read_seq(const SSL *ssl);
 
 // SSL_get_dtls_handshake_write_seq returns the 16-bit sequence number of the
 // next DTLS handshake message to be written or 0x10000 if handshake message
 // 0xffff (the maximum) has already been written.
 OPENSSL_EXPORT uint32_t SSL_get_dtls_handshake_write_seq(const SSL *ssl);
 
 // SSL_get_dtls_read_epoch returns the highest available DTLS read epoch in
 // |ssl|. In DTLS 1.3, |ssl| may have earlier epochs also active, sometimes to
 // optionally improve handling of reordered packets and sometimes as an
 // important part of the protocol correctness in the face of packet loss.
 //
 // The failure conditions of |SSL_get_dtls_read_traffic_secret| and
 // |SSL_get_dtls_read_sequence| can be used to determine if past epochs are
 // active.
 OPENSSL_EXPORT uint16_t SSL_get_dtls_read_epoch(const SSL *ssl);
 
 // SSL_get_dtls_write_epoch returns the current DTLS write epoch. If the
 // handshake is idle (see |SSL_is_dtls_handshake_idle|), no other write epochs
 // will be active.
 OPENSSL_EXPORT uint16_t SSL_get_dtls_write_epoch(const SSL *ssl);
 
 // SSL_get_dtls_read_sequence returns one more than the sequence number of the
 // highest record received in |epoch|. If no records have been received in
 // |epoch|. If the epoch does not exist, it returns |UINT64_MAX|.
 //
 // It is safe to discard all sequence numbers less than the return value of this
 // function. The sequence numbers returned by this function do not include the
 // epoch number in the upper 16 bits.
 OPENSSL_EXPORT uint64_t SSL_get_dtls_read_sequence(const SSL *ssl,
                                                    uint16_t epoch);
 
 // SSL_get_dtls_write_sequence returns the sequence number of the next record to
 // be sent in |epoch|. If the epoch does not exist, it returns |UINT64_MAX|.
 //
 // The sequence numbers returned by this function do not include the epoch
 // number in the upper 16 bits.
 OPENSSL_EXPORT uint64_t SSL_get_dtls_write_sequence(const SSL *ssl,
                                                     uint16_t epoch);
 
 // SSL_get_dtls_read_traffic_secret looks up the traffic secret for read epoch
 // |epoch|. If the epoch exists and is an encrypted (not epoch zero) DTLS 1.3
 // epoch, it sets |*out_data| and |*out_len| to a buffer containing the secrets
 // and returns one. Otherwise, it returns zero. The buffer is valid until the
 // next operation on |ssl|.
 OPENSSL_EXPORT int SSL_get_dtls_read_traffic_secret(const SSL *ssl,
                                                     const uint8_t **out_data,
                                                     size_t *out_len,
                                                     uint16_t epoch);
 
 // SSL_get_dtls_write_traffic_secret looks up the traffic secret for write epoch
 // |epoch|. If the epoch exists and is an encrypted (not epoch zero) DTLS 1.3
 // epoch, it sets |*out_data| and |*out_len| to a buffer containing the secrets
 // and returns one. Otherwise, it returns zero. The buffer is valid until the
 // next operation on |ssl|.
 OPENSSL_EXPORT int SSL_get_dtls_write_traffic_secret(const SSL *ssl,
                                                      const uint8_t **out_data,
                                                      size_t *out_len,
                                                      uint16_t epoch);
 
 
 // Handshake hints.
 //
 // WARNING: Contact the BoringSSL team before using this API. While this
 // mechanism was designed to gracefully recover from version skew and
 // configuration mismatch, splitting a single TLS server into multiple services
 // is complex.
 //
 // Some server deployments make asynchronous RPC calls in both ClientHello
 // dispatch and private key operations. In TLS handshakes where the private key
 // operation occurs in the first round-trip, this results in two consecutive RPC
 // round-trips. Handshake hints allow the RPC service to predict a signature.
 // If correctly predicted, this can skip the second RPC call.
 //
 // First, the server installs a certificate selection callback (see
 // |SSL_CTX_set_select_certificate_cb|). When that is called, it performs the
 // RPC as before, but includes the ClientHello and a capabilities string from
 // |SSL_serialize_capabilities|.
 //
 // Next, the RPC service creates its own |SSL| object, applies the results of
 // certificate selection, calls |SSL_request_handshake_hints|, and runs the
 // handshake. If this successfully computes handshake hints (see
 // |SSL_serialize_handshake_hints|), the RPC server should send the hints
 // alongside any certificate selection results.
 //
 // Finally, the server calls |SSL_set_handshake_hints| and applies any
 // configuration from the RPC server. It then completes the handshake as before.
 // If the hints apply, BoringSSL will use the predicted signature and skip the
 // private key callbacks. Otherwise, BoringSSL will call private key callbacks
 // to generate a signature as before.
 //
 // Callers should synchronize configuration across the two services.
 // Configuration mismatches and some cases of version skew are not fatal, but
 // may result in the hints not applying. Additionally, some handshake flows use
 // the private key in later round-trips, such as TLS 1.3 HelloRetryRequest. In
 // those cases, BoringSSL will not predict a signature as there is no benefit.
 // Callers must allow for handshakes to complete without a predicted signature.
 
 // SSL_serialize_capabilities writes an opaque byte string to |out| describing
 // some of |ssl|'s capabilities. It returns one on success and zero on error.
 //
 // This string is used by BoringSSL internally to reduce the impact of version
 // skew.
 OPENSSL_EXPORT int SSL_serialize_capabilities(const SSL *ssl, CBB *out);
 
 // SSL_request_handshake_hints configures |ssl| to generate a handshake hint for
 // |client_hello|. It returns one on success and zero on error. |client_hello|
 // should contain a serialized ClientHello structure, from the |client_hello|
 // and |client_hello_len| fields of the |SSL_CLIENT_HELLO| structure.
 // |capabilities| should contain the output of |SSL_serialize_capabilities|.
 //
 // When configured, |ssl| will perform no I/O (so there is no need to configure
 // |BIO|s). For QUIC, the caller should still configure an |SSL_QUIC_METHOD|,
 // but the callbacks themselves will never be called and may be left NULL or
 // report failure. |SSL_provide_quic_data| also should not be called.
 //
 // If hint generation is successful, |SSL_do_handshake| will stop the handshake
 // early with |SSL_get_error| returning |SSL_ERROR_HANDSHAKE_HINTS_READY|. At
 // this point, the caller should run |SSL_serialize_handshake_hints| to extract
 // the resulting hints.
 //
 // Hint generation may fail if, e.g., |ssl| was unable to process the
 // ClientHello. Callers should then complete the certificate selection RPC and
 // continue the original handshake with no hint. It will likely fail, but this
 // reports the correct alert to the client and is more robust in case of
 // mismatch.
 OPENSSL_EXPORT int SSL_request_handshake_hints(SSL *ssl,
                                                const uint8_t *client_hello,
                                                size_t client_hello_len,
                                                const uint8_t *capabilities,
                                                size_t capabilities_len);
 
 // SSL_serialize_handshake_hints writes an opaque byte string to |out|
 // containing the handshake hints computed by |out|. It returns one on success
 // and zero on error. This function should only be called if
 // |SSL_request_handshake_hints| was configured and the handshake terminated
 // with |SSL_ERROR_HANDSHAKE_HINTS_READY|.
 //
 // This string may be passed to |SSL_set_handshake_hints| on another |SSL| to
 // avoid an extra signature call.
 OPENSSL_EXPORT int SSL_serialize_handshake_hints(const SSL *ssl, CBB *out);
 
 // SSL_set_handshake_hints configures |ssl| to use |hints| as handshake hints.
 // It returns one on success and zero on error. The handshake will then continue
 // as before, but apply predicted values from |hints| where applicable.
 //
 // Hints may contain connection and session secrets, so they must not leak and
 // must come from a source trusted to terminate the connection. However, they
 // will not change |ssl|'s configuration. The caller is responsible for
 // serializing and applying options from the RPC server as needed. This ensures
 // |ssl|'s behavior is self-consistent and consistent with the caller's local
 // decisions.
 OPENSSL_EXPORT int SSL_set_handshake_hints(SSL *ssl, const uint8_t *hints,
                                            size_t hints_len);
 
 
 // Obscure functions.
 
 // SSL_CTX_set_msg_callback installs |cb| as the message callback for |ctx|.
 // This callback will be called when sending or receiving low-level record
 // headers, complete handshake messages, ChangeCipherSpec, alerts, and DTLS
 // ACKs. |write_p| is one for outgoing messages and zero for incoming messages.
 //
 // For each record header, |cb| is called with |version| = 0 and |content_type|
 // = |SSL3_RT_HEADER|. The |len| bytes from |buf| contain the header. Note that
 // this does not include the record body. If the record is sealed, the length
 // in the header is the length of the ciphertext.
 //
 // For each handshake message, ChangeCipherSpec, alert, and DTLS ACK, |version|
 // is the protocol version and |content_type| is the corresponding record type.
 // The |len| bytes from |buf| contain the handshake message, one-byte
 // ChangeCipherSpec body, two-byte alert, and ACK respectively.
 //
 // In connections that enable ECH, |cb| is additionally called with
 // |content_type| = |SSL3_RT_CLIENT_HELLO_INNER| for each ClientHelloInner that
 // is encrypted or decrypted. The |len| bytes from |buf| contain the
 // ClientHelloInner, including the reconstructed outer extensions and handshake
 // header.
 //
 // For a V2ClientHello, |version| is |SSL2_VERSION|, |content_type| is zero, and
 // the |len| bytes from |buf| contain the V2ClientHello structure.
 OPENSSL_EXPORT void SSL_CTX_set_msg_callback(
     SSL_CTX *ctx, void (*cb)(int is_write, int version, int content_type,
                              const void *buf, size_t len, SSL *ssl, void *arg));
 
 // SSL_CTX_set_msg_callback_arg sets the |arg| parameter of the message
 // callback.
 OPENSSL_EXPORT void SSL_CTX_set_msg_callback_arg(SSL_CTX *ctx, void *arg);
 
 // SSL_set_msg_callback installs |cb| as the message callback of |ssl|. See
 // |SSL_CTX_set_msg_callback| for when this callback is called.
 OPENSSL_EXPORT void SSL_set_msg_callback(
     SSL *ssl, void (*cb)(int write_p, int version, int content_type,
                          const void *buf, size_t len, SSL *ssl, void *arg));
 
 // SSL_set_msg_callback_arg sets the |arg| parameter of the message callback.
 OPENSSL_EXPORT void SSL_set_msg_callback_arg(SSL *ssl, void *arg);
 
 // SSL_CTX_set_keylog_callback configures a callback to log key material. This
 // is intended for debugging use with tools like Wireshark. The |cb| function
 // should log |line| followed by a newline, synchronizing with any concurrent
 // access to the log.
 //
 // The format is described in
 // https://www.ietf.org/archive/id/draft-ietf-tls-keylogfile-01.html
 //
 // WARNING: The data in |line| allows an attacker to break security properties
 // of the TLS protocol, including confidentiality, integrity, and forward
 // secrecy. This impacts both the current connection, and, in TLS 1.2, future
 // connections that resume a session from it. Both direct access to the data and
 // side channel leaks from application code are possible attack vectors. This
 // callback is intended for debugging and should not be used in production
 // connections.
 OPENSSL_EXPORT void SSL_CTX_set_keylog_callback(SSL_CTX *ctx,
                                                 void (*cb)(const SSL *ssl,
                                                            const char *line));
 
 // SSL_CTX_get_keylog_callback returns the callback configured by
 // |SSL_CTX_set_keylog_callback|.
 OPENSSL_EXPORT void (*SSL_CTX_get_keylog_callback(const SSL_CTX *ctx))(
     const SSL *ssl, const char *line);
 
 // SSL_CTX_set_current_time_cb configures a callback to retrieve the current
 // time, which should be set in |*out_clock|. This can be used for testing
 // purposes; for example, a callback can be configured that returns a time
 // set explicitly by the test. The |ssl| pointer passed to |cb| is always null.
 OPENSSL_EXPORT void SSL_CTX_set_current_time_cb(
     SSL_CTX *ctx, void (*cb)(const SSL *ssl, struct timeval *out_clock));
 
 // SSL_set_shed_handshake_config allows some of the configuration of |ssl| to be
 // freed after its handshake completes.  Once configuration has been shed, APIs
 // that query it may fail.  "Configuration" in this context means anything that
 // was set by the caller, as distinct from information derived from the
 // handshake.  For example, |SSL_get_ciphers| queries how the |SSL| was
 // configured by the caller, and fails after configuration has been shed,
 // whereas |SSL_get_cipher| queries the result of the handshake, and is
 // unaffected by configuration shedding.
 //
 // If configuration shedding is enabled, it is an error to call |SSL_clear|.
 //
 // Note that configuration shedding as a client additionally depends on
 // renegotiation being disabled (see |SSL_set_renegotiate_mode|). If
 // renegotiation is possible, the configuration will be retained. If
 // configuration shedding is enabled and renegotiation later disabled after the
 // handshake, |SSL_set_renegotiate_mode| will shed configuration then. This may
 // be useful for clients which support renegotiation with some ALPN protocols,
 // such as HTTP/1.1, and not others, such as HTTP/2.
 OPENSSL_EXPORT void SSL_set_shed_handshake_config(SSL *ssl, int enable);
 
 enum ssl_renegotiate_mode_t BORINGSSL_ENUM_INT {
   ssl_renegotiate_never = 0,
   ssl_renegotiate_once,
   ssl_renegotiate_freely,
   ssl_renegotiate_ignore,
   ssl_renegotiate_explicit,
 };
 
 // SSL_set_renegotiate_mode configures how |ssl|, a client, reacts to
 // renegotiation attempts by a server. If |ssl| is a server, peer-initiated
 // renegotiations are *always* rejected and this function does nothing.
 //
 // WARNING: Renegotiation is error-prone, complicates TLS's security properties,
 // and increases its attack surface. When enabled, many common assumptions about
 // BoringSSL's behavior no longer hold, and the calling application must handle
 // more cases. Renegotiation is also incompatible with many application
 // protocols, e.g. section 9.2.1 of RFC 7540. Many functions behave in ambiguous
 // or undefined ways during a renegotiation.
 //
 // The renegotiation mode defaults to |ssl_renegotiate_never|, but may be set
 // at any point in a connection's lifetime. Set it to |ssl_renegotiate_once| to
 // allow one renegotiation, |ssl_renegotiate_freely| to allow all
 // renegotiations or |ssl_renegotiate_ignore| to ignore HelloRequest messages.
 // Note that ignoring HelloRequest messages may cause the connection to stall
 // if the server waits for the renegotiation to complete.
 //
 // If set to |ssl_renegotiate_explicit|, |SSL_read| and |SSL_peek| calls which
 // encounter a HelloRequest will pause with |SSL_ERROR_WANT_RENEGOTIATE|.
 // |SSL_write| will continue to work while paused. The caller may call
 // |SSL_renegotiate| to begin the renegotiation at a later point. This mode may
 // be used if callers wish to eagerly call |SSL_peek| without triggering a
 // renegotiation.
 //
 // If configuration shedding is enabled (see |SSL_set_shed_handshake_config|),
 // configuration is released if, at any point after the handshake, renegotiation
 // is disabled. It is not possible to switch from disabling renegotiation to
 // enabling it on a given connection. Callers that condition renegotiation on,
 // e.g., ALPN must enable renegotiation before the handshake and conditionally
 // disable it afterwards.
 //
 // When enabled, renegotiation can cause properties of |ssl|, such as the cipher
 // suite, to change during the lifetime of the connection. More over, during a
 // renegotiation, not all properties of the new handshake are available or fully
 // established. In BoringSSL, most functions, such as |SSL_get_current_cipher|,
 // report information from the most recently completed handshake, not the
 // pending one. However, renegotiation may rerun handshake callbacks, such as
 // |SSL_CTX_set_cert_cb|. Such callbacks must ensure they are acting on the
 // desired versions of each property.
 //
 // BoringSSL does not reverify peer certificates on renegotiation and instead
 // requires they match between handshakes, so certificate verification callbacks
 // (see |SSL_CTX_set_custom_verify|) may assume |ssl| is in the initial
 // handshake and use |SSL_get0_peer_certificates|, etc.
 //
 // There is no support in BoringSSL for initiating renegotiations as a client
 // or server.
 OPENSSL_EXPORT void SSL_set_renegotiate_mode(SSL *ssl,
                                              enum ssl_renegotiate_mode_t mode);
 
 // SSL_renegotiate starts a deferred renegotiation on |ssl| if it was configured
 // with |ssl_renegotiate_explicit| and has a pending HelloRequest. It returns
 // one on success and zero on error.
 //
 // This function does not do perform any I/O. On success, a subsequent
 // |SSL_do_handshake| call will run the handshake. |SSL_write| and
 // |SSL_read| will also complete the handshake before sending or receiving
 // application data.
 OPENSSL_EXPORT int SSL_renegotiate(SSL *ssl);
 
 // SSL_renegotiate_pending returns one if |ssl| is in the middle of a
 // renegotiation.
 OPENSSL_EXPORT int SSL_renegotiate_pending(SSL *ssl);
 
 // SSL_total_renegotiations returns the total number of renegotiation handshakes
 // performed by |ssl|. This includes the pending renegotiation, if any.
 OPENSSL_EXPORT int SSL_total_renegotiations(const SSL *ssl);
 
 // SSL_MAX_CERT_LIST_DEFAULT is the default maximum length, in bytes, of a peer
 // certificate chain.
 #define SSL_MAX_CERT_LIST_DEFAULT (1024 * 100)
 
 // SSL_CTX_get_max_cert_list returns the maximum length, in bytes, of a peer
 // certificate chain accepted by |ctx|.
 OPENSSL_EXPORT size_t SSL_CTX_get_max_cert_list(const SSL_CTX *ctx);
 
 // SSL_CTX_set_max_cert_list sets the maximum length, in bytes, of a peer
 // certificate chain to |max_cert_list|. This affects how much memory may be
 // consumed during the handshake.
 OPENSSL_EXPORT void SSL_CTX_set_max_cert_list(SSL_CTX *ctx,
                                               size_t max_cert_list);
 
 // SSL_get_max_cert_list returns the maximum length, in bytes, of a peer
 // certificate chain accepted by |ssl|.
 OPENSSL_EXPORT size_t SSL_get_max_cert_list(const SSL *ssl);
 
 // SSL_set_max_cert_list sets the maximum length, in bytes, of a peer
 // certificate chain to |max_cert_list|. This affects how much memory may be
 // consumed during the handshake.
 OPENSSL_EXPORT void SSL_set_max_cert_list(SSL *ssl, size_t max_cert_list);
 
 // SSL_CTX_set_max_send_fragment sets the maximum length, in bytes, of records
 // sent by |ctx|. Beyond this length, handshake messages and application data
 // will be split into multiple records. It returns one on success or zero on
 // error.
 OPENSSL_EXPORT int SSL_CTX_set_max_send_fragment(SSL_CTX *ctx,
                                                  size_t max_send_fragment);
 
 // SSL_set_max_send_fragment sets the maximum length, in bytes, of records sent
 // by |ssl|. Beyond this length, handshake messages and application data will
 // be split into multiple records. It returns one on success or zero on
 // error.
 OPENSSL_EXPORT int SSL_set_max_send_fragment(SSL *ssl,
                                              size_t max_send_fragment);
 
 // ssl_early_callback_ctx (aka |SSL_CLIENT_HELLO|) is passed to certain
 // callbacks that are called very early on during the server handshake. At this
 // point, much of the SSL* hasn't been filled out and only the ClientHello can
 // be depended on.
 struct ssl_early_callback_ctx {
   SSL *ssl;
   const uint8_t *client_hello;
   size_t client_hello_len;
   uint16_t version;
   const uint8_t *random;
   size_t random_len;
   const uint8_t *session_id;
   size_t session_id_len;
   const uint8_t *dtls_cookie;
   size_t dtls_cookie_len;
   const uint8_t *cipher_suites;
   size_t cipher_suites_len;
   const uint8_t *compression_methods;
   size_t compression_methods_len;
   const uint8_t *extensions;
   size_t extensions_len;
 } /* SSL_CLIENT_HELLO */;
 
 // ssl_select_cert_result_t enumerates the possible results from selecting a
 // certificate with |select_certificate_cb|.
 enum ssl_select_cert_result_t BORINGSSL_ENUM_INT {
   // ssl_select_cert_success indicates that the certificate selection was
   // successful.
   ssl_select_cert_success = 1,
   // ssl_select_cert_retry indicates that the operation could not be
   // immediately completed and must be reattempted at a later point.
   ssl_select_cert_retry = 0,
   // ssl_select_cert_error indicates that a fatal error occured and the
   // handshake should be terminated.
   ssl_select_cert_error = -1,
   // ssl_select_cert_disable_ech indicates that, although an encrypted
   // ClientHelloInner was decrypted, it should be discarded. The certificate
   // selection callback will then be called again, passing in the
   // ClientHelloOuter instead. From there, the handshake will proceed
   // without retry_configs, to signal to the client to disable ECH.
   //
   // This value may only be returned when |SSL_ech_accepted| returnes one. It
   // may be useful if the ClientHelloInner indicated a service which does not
   // support ECH, e.g. if it is a TLS-1.2 only service.
   ssl_select_cert_disable_ech = -2,
 };
 
 // SSL_early_callback_ctx_extension_get searches the extensions in
 // |client_hello| for an extension of the given type. If not found, it returns
 // zero. Otherwise it sets |out_data| to point to the extension contents (not
 // including the type and length bytes), sets |out_len| to the length of the
 // extension contents and returns one.
 OPENSSL_EXPORT int SSL_early_callback_ctx_extension_get(
     const SSL_CLIENT_HELLO *client_hello, uint16_t extension_type,
     const uint8_t **out_data, size_t *out_len);
 
 // SSL_CTX_set_select_certificate_cb sets a callback that is called before most
 // ClientHello processing and before the decision whether to resume a session
 // is made. The callback may inspect the ClientHello and configure the
 // connection. See |ssl_select_cert_result_t| for details of the return values.
 //
 // In the case that a retry is indicated, |SSL_get_error| will return
 // |SSL_ERROR_PENDING_CERTIFICATE| and the caller should arrange for the
 // high-level operation on |ssl| to be retried at a later time, which will
 // result in another call to |cb|.
 //
 // |SSL_get_servername| may be used during this callback.
 //
 // Note: The |SSL_CLIENT_HELLO| is only valid for the duration of the callback
 // and is not valid while the handshake is paused.
 OPENSSL_EXPORT void SSL_CTX_set_select_certificate_cb(
     SSL_CTX *ctx,
     enum ssl_select_cert_result_t (*cb)(const SSL_CLIENT_HELLO *));
 
 // SSL_CTX_set_dos_protection_cb sets a callback that is called once the
 // resumption decision for a ClientHello has been made. It can return one to
 // allow the handshake to continue or zero to cause the handshake to abort.
 OPENSSL_EXPORT void SSL_CTX_set_dos_protection_cb(
     SSL_CTX *ctx, int (*cb)(const SSL_CLIENT_HELLO *));
 
 // SSL_CTX_set_reverify_on_resume configures whether the certificate
 // verification callback will be used to reverify stored certificates
 // when resuming a session. This only works with |SSL_CTX_set_custom_verify|.
 // For now, this is incompatible with |SSL_VERIFY_NONE| mode, and is only
 // respected on clients.
 OPENSSL_EXPORT void SSL_CTX_set_reverify_on_resume(SSL_CTX *ctx, int enabled);
 
 // SSL_set_enforce_rsa_key_usage configures whether, when |ssl| is a client
 // negotiating TLS 1.2 or below, the keyUsage extension of RSA leaf server
 // certificates will be checked for consistency with the TLS usage. In all other
 // cases, this check is always enabled.
 //
 // This parameter may be set late; it will not be read until after the
 // certificate verification callback.
 OPENSSL_EXPORT void SSL_set_enforce_rsa_key_usage(SSL *ssl, int enabled);
 
 // SSL_was_key_usage_invalid returns one if |ssl|'s handshake succeeded despite
 // using TLS parameters which were incompatible with the leaf certificate's
 // keyUsage extension. Otherwise, it returns zero.
 //
 // If |SSL_set_enforce_rsa_key_usage| is enabled or not applicable, this
 // function will always return zero because key usages will be consistently
 // checked.
 OPENSSL_EXPORT int SSL_was_key_usage_invalid(const SSL *ssl);
 
 // SSL_ST_* are possible values for |SSL_state|, the bitmasks that make them up,
 // and some historical values for compatibility. Only |SSL_ST_INIT| and
 // |SSL_ST_OK| are ever returned.
 #define SSL_ST_CONNECT 0x1000
 #define SSL_ST_ACCEPT 0x2000
 #define SSL_ST_MASK 0x0FFF
 #define SSL_ST_INIT (SSL_ST_CONNECT | SSL_ST_ACCEPT)
 #define SSL_ST_OK 0x03
 #define SSL_ST_RENEGOTIATE (0x04 | SSL_ST_INIT)
 #define SSL_ST_BEFORE (0x05 | SSL_ST_INIT)
 
 // TLS_ST_* are aliases for |SSL_ST_*| for OpenSSL 1.1.0 compatibility.
 #define TLS_ST_OK SSL_ST_OK
 #define TLS_ST_BEFORE SSL_ST_BEFORE
 
 // SSL_CB_* are possible values for the |type| parameter in the info
 // callback and the bitmasks that make them up.
 #define SSL_CB_LOOP 0x01
 #define SSL_CB_EXIT 0x02
 #define SSL_CB_READ 0x04
 #define SSL_CB_WRITE 0x08
 #define SSL_CB_ALERT 0x4000
 #define SSL_CB_READ_ALERT (SSL_CB_ALERT | SSL_CB_READ)
 #define SSL_CB_WRITE_ALERT (SSL_CB_ALERT | SSL_CB_WRITE)
 #define SSL_CB_ACCEPT_LOOP (SSL_ST_ACCEPT | SSL_CB_LOOP)
 #define SSL_CB_ACCEPT_EXIT (SSL_ST_ACCEPT | SSL_CB_EXIT)
 #define SSL_CB_CONNECT_LOOP (SSL_ST_CONNECT | SSL_CB_LOOP)
 #define SSL_CB_CONNECT_EXIT (SSL_ST_CONNECT | SSL_CB_EXIT)
 #define SSL_CB_HANDSHAKE_START 0x10
 #define SSL_CB_HANDSHAKE_DONE 0x20
 
 // SSL_CTX_set_info_callback configures a callback to be run when various
 // events occur during a connection's lifetime. The |type| argument determines
 // the type of event and the meaning of the |value| argument. Callbacks must
 // ignore unexpected |type| values.
 //
 // |SSL_CB_READ_ALERT| is signaled for each alert received, warning or fatal.
 // The |value| argument is a 16-bit value where the alert level (either
 // |SSL3_AL_WARNING| or |SSL3_AL_FATAL|) is in the most-significant eight bits
 // and the alert type (one of |SSL_AD_*|) is in the least-significant eight.
 //
 // |SSL_CB_WRITE_ALERT| is signaled for each alert sent. The |value| argument
 // is constructed as with |SSL_CB_READ_ALERT|.
 //
 // |SSL_CB_HANDSHAKE_START| is signaled when a handshake begins. The |value|
 // argument is always one.
 //
 // |SSL_CB_HANDSHAKE_DONE| is signaled when a handshake completes successfully.
 // The |value| argument is always one. If a handshake False Starts, this event
 // may be used to determine when the Finished message is received.
 //
 // The following event types expose implementation details of the handshake
 // state machine. Consuming them is deprecated.
 //
 // |SSL_CB_ACCEPT_LOOP| (respectively, |SSL_CB_CONNECT_LOOP|) is signaled when
 // a server (respectively, client) handshake progresses. The |value| argument
 // is always one.
 //
 // |SSL_CB_ACCEPT_EXIT| (respectively, |SSL_CB_CONNECT_EXIT|) is signaled when
 // a server (respectively, client) handshake completes, fails, or is paused.
 // The |value| argument is one if the handshake succeeded and <= 0
 // otherwise.
 OPENSSL_EXPORT void SSL_CTX_set_info_callback(SSL_CTX *ctx,
                                               void (*cb)(const SSL *ssl,
                                                          int type, int value));
 
 // SSL_CTX_get_info_callback returns the callback set by
 // |SSL_CTX_set_info_callback|.
 OPENSSL_EXPORT void (*SSL_CTX_get_info_callback(SSL_CTX *ctx))(const SSL *ssl,
                                                                int type,
                                                                int value);
 
 // SSL_set_info_callback configures a callback to be run at various events
 // during a connection's lifetime. See |SSL_CTX_set_info_callback|.
 OPENSSL_EXPORT void SSL_set_info_callback(SSL *ssl,
                                           void (*cb)(const SSL *ssl, int type,
                                                      int value));
 
 // SSL_get_info_callback returns the callback set by |SSL_set_info_callback|.
 OPENSSL_EXPORT void (*SSL_get_info_callback(const SSL *ssl))(const SSL *ssl,
                                                              int type,
                                                              int value);
 
 // SSL_state_string_long returns the current state of the handshake state
 // machine as a string. This may be useful for debugging and logging.
 OPENSSL_EXPORT const char *SSL_state_string_long(const SSL *ssl);
 
 #define SSL_SENT_SHUTDOWN 1
 #define SSL_RECEIVED_SHUTDOWN 2
 
 // SSL_get_shutdown returns a bitmask with a subset of |SSL_SENT_SHUTDOWN| and
 // |SSL_RECEIVED_SHUTDOWN| to query whether close_notify was sent or received,
 // respectively.
 OPENSSL_EXPORT int SSL_get_shutdown(const SSL *ssl);
 
 // SSL_get_peer_signature_algorithm returns the signature algorithm used by the
 // peer. If not applicable, it returns zero.
 OPENSSL_EXPORT uint16_t SSL_get_peer_signature_algorithm(const SSL *ssl);
 
 // SSL_get_client_random writes up to |max_out| bytes of the most recent
 // handshake's client_random to |out| and returns the number of bytes written.
 // If |max_out| is zero, it returns the size of the client_random.
 OPENSSL_EXPORT size_t SSL_get_client_random(const SSL *ssl, uint8_t *out,
                                             size_t max_out);
 
 // SSL_get_server_random writes up to |max_out| bytes of the most recent
 // handshake's server_random to |out| and returns the number of bytes written.
 // If |max_out| is zero, it returns the size of the server_random.
 OPENSSL_EXPORT size_t SSL_get_server_random(const SSL *ssl, uint8_t *out,
                                             size_t max_out);
 
 // SSL_get_pending_cipher returns the cipher suite for the current handshake or
 // NULL if one has not been negotiated yet or there is no pending handshake.
 OPENSSL_EXPORT const SSL_CIPHER *SSL_get_pending_cipher(const SSL *ssl);
 
 // SSL_set_retain_only_sha256_of_client_certs, on a server, sets whether only
 // the SHA-256 hash of peer's certificate should be saved in memory and in the
 // session. This can save memory, ticket size and session cache space. If
 // enabled, |SSL_get_peer_certificate| will return NULL after the handshake
 // completes. See |SSL_SESSION_has_peer_sha256| and
 // |SSL_SESSION_get0_peer_sha256| to query the hash.
 OPENSSL_EXPORT void SSL_set_retain_only_sha256_of_client_certs(SSL *ssl,
                                                                int enable);
 
 // SSL_CTX_set_retain_only_sha256_of_client_certs, on a server, sets whether
 // only the SHA-256 hash of peer's certificate should be saved in memory and in
 // the session. This can save memory, ticket size and session cache space. If
 // enabled, |SSL_get_peer_certificate| will return NULL after the handshake
 // completes. See |SSL_SESSION_has_peer_sha256| and
 // |SSL_SESSION_get0_peer_sha256| to query the hash.
 OPENSSL_EXPORT void SSL_CTX_set_retain_only_sha256_of_client_certs(SSL_CTX *ctx,
                                                                    int enable);
 
 // SSL_CTX_set_grease_enabled configures whether sockets on |ctx| should enable
 // GREASE. See RFC 8701.
 OPENSSL_EXPORT void SSL_CTX_set_grease_enabled(SSL_CTX *ctx, int enabled);
 
 // SSL_CTX_set_permute_extensions configures whether sockets on |ctx| should
 // permute extensions. For now, this is only implemented for the ClientHello.
 OPENSSL_EXPORT void SSL_CTX_set_permute_extensions(SSL_CTX *ctx, int enabled);
 
 // SSL_set_permute_extensions configures whether sockets on |ssl| should
 // permute extensions. For now, this is only implemented for the ClientHello.
 OPENSSL_EXPORT void SSL_set_permute_extensions(SSL *ssl, int enabled);
 
 // SSL_max_seal_overhead returns the maximum overhead, in bytes, of sealing a
 // record with |ssl|.
 OPENSSL_EXPORT size_t SSL_max_seal_overhead(const SSL *ssl);
 
 // SSL_CTX_set_false_start_allowed_without_alpn configures whether connections
 // on |ctx| may use False Start (if |SSL_MODE_ENABLE_FALSE_START| is enabled)
 // without negotiating ALPN.
 OPENSSL_EXPORT void SSL_CTX_set_false_start_allowed_without_alpn(SSL_CTX *ctx,
                                                                  int allowed);
 
 // SSL_used_hello_retry_request returns one if the TLS 1.3 HelloRetryRequest
 // message has been either sent by the server or received by the client. It
 // returns zero otherwise.
 OPENSSL_EXPORT int SSL_used_hello_retry_request(const SSL *ssl);
 
 // SSL_set_jdk11_workaround configures whether to workaround various bugs in
 // JDK 11's TLS 1.3 implementation by disabling TLS 1.3 for such clients.
 //
 // https://bugs.openjdk.java.net/browse/JDK-8211806
 // https://bugs.openjdk.java.net/browse/JDK-8212885
 // https://bugs.openjdk.java.net/browse/JDK-8213202
 OPENSSL_EXPORT void SSL_set_jdk11_workaround(SSL *ssl, int enable);
 
 // SSL_parse_client_hello decodes a ClientHello structure from |len| bytes in
 // |in|. On success, it returns one and writes the result to |*out|. Otherwise,
 // it returns zero. |ssl| will be saved into |*out| and determines how the
 // ClientHello is parsed, notably TLS vs DTLS. The fields in |*out| will alias
 // |in| and are only valid as long as |in| is valid and unchanged.
 //
 // |in| should contain just the ClientHello structure (RFC 8446 and RFC 9147),
 // excluding the handshake header and already reassembled from record layer.
 // That is, |in| should begin with the legacy_version field, not the
 // client_hello HandshakeType constant or the handshake ContentType constant.
 OPENSSL_EXPORT int SSL_parse_client_hello(const SSL *ssl, SSL_CLIENT_HELLO *out,
                                           const uint8_t *in, size_t len);
 
 
 // Deprecated functions.
 
 // SSL_library_init returns one.
 OPENSSL_EXPORT int SSL_library_init(void);
 
 // SSL_CIPHER_description writes a description of |cipher| into |buf| and
 // returns |buf|. If |buf| is NULL, it returns a newly allocated string, to be
 // freed with |OPENSSL_free|, or NULL on error.
 //
 // The description includes a trailing newline and has the form:
 // AES128-SHA              Kx=RSA      Au=RSA  Enc=AES(128)  Mac=SHA1
 //
 // Consider |SSL_CIPHER_standard_name| or |SSL_CIPHER_get_name| instead.
 OPENSSL_EXPORT const char *SSL_CIPHER_description(const SSL_CIPHER *cipher,
                                                   char *buf, int len);
 
 // SSL_CIPHER_get_version returns the string "TLSv1/SSLv3".
 OPENSSL_EXPORT const char *SSL_CIPHER_get_version(const SSL_CIPHER *cipher);
 
 typedef void COMP_METHOD;
 typedef struct ssl_comp_st SSL_COMP;
 
 // SSL_COMP_get_compression_methods returns NULL.
 OPENSSL_EXPORT STACK_OF(SSL_COMP) *SSL_COMP_get_compression_methods(void);
 
 // SSL_COMP_add_compression_method returns one.
 OPENSSL_EXPORT int SSL_COMP_add_compression_method(int id, COMP_METHOD *cm);
 
 // SSL_COMP_get_name returns NULL.
 OPENSSL_EXPORT const char *SSL_COMP_get_name(const COMP_METHOD *comp);
 
 // SSL_COMP_get0_name returns the |name| member of |comp|.
 OPENSSL_EXPORT const char *SSL_COMP_get0_name(const SSL_COMP *comp);
 
 // SSL_COMP_get_id returns the |id| member of |comp|.
 OPENSSL_EXPORT int SSL_COMP_get_id(const SSL_COMP *comp);
 
 // SSL_COMP_free_compression_methods does nothing.
 OPENSSL_EXPORT void SSL_COMP_free_compression_methods(void);
 
 // SSLv23_method calls |TLS_method|.
 OPENSSL_EXPORT const SSL_METHOD *SSLv23_method(void);
 
 // These version-specific methods behave exactly like |TLS_method| and
 // |DTLS_method| except they also call |SSL_CTX_set_min_proto_version| and
 // |SSL_CTX_set_max_proto_version| to lock connections to that protocol
 // version.
 OPENSSL_EXPORT const SSL_METHOD *TLSv1_method(void);
 OPENSSL_EXPORT const SSL_METHOD *TLSv1_1_method(void);
 OPENSSL_EXPORT const SSL_METHOD *TLSv1_2_method(void);
 OPENSSL_EXPORT const SSL_METHOD *DTLSv1_method(void);
 OPENSSL_EXPORT const SSL_METHOD *DTLSv1_2_method(void);
 
 // These client- and server-specific methods call their corresponding generic
 // methods.
 OPENSSL_EXPORT const SSL_METHOD *TLS_server_method(void);
 OPENSSL_EXPORT const SSL_METHOD *TLS_client_method(void);
 OPENSSL_EXPORT const SSL_METHOD *SSLv23_server_method(void);
 OPENSSL_EXPORT const SSL_METHOD *SSLv23_client_method(void);
 OPENSSL_EXPORT const SSL_METHOD *TLSv1_server_method(void);
 OPENSSL_EXPORT const SSL_METHOD *TLSv1_client_method(void);
 OPENSSL_EXPORT const SSL_METHOD *TLSv1_1_server_method(void);
 OPENSSL_EXPORT const SSL_METHOD *TLSv1_1_client_method(void);
 OPENSSL_EXPORT const SSL_METHOD *TLSv1_2_server_method(void);
 OPENSSL_EXPORT const SSL_METHOD *TLSv1_2_client_method(void);
 OPENSSL_EXPORT const SSL_METHOD *DTLS_server_method(void);
 OPENSSL_EXPORT const SSL_METHOD *DTLS_client_method(void);
 OPENSSL_EXPORT const SSL_METHOD *DTLSv1_server_method(void);
 OPENSSL_EXPORT const SSL_METHOD *DTLSv1_client_method(void);
 OPENSSL_EXPORT const SSL_METHOD *DTLSv1_2_server_method(void);
 OPENSSL_EXPORT const SSL_METHOD *DTLSv1_2_client_method(void);
 
 // SSL_clear resets |ssl| to allow another connection and returns one on success
 // or zero on failure. It returns most configuration state but releases memory
 // associated with the current connection.
 //
 // Free |ssl| and create a new one instead.
 OPENSSL_EXPORT int SSL_clear(SSL *ssl);
 
 // SSL_CTX_set_tmp_rsa_callback does nothing.
 OPENSSL_EXPORT void SSL_CTX_set_tmp_rsa_callback(
     SSL_CTX *ctx, RSA *(*cb)(SSL *ssl, int is_export, int keylength));
 
 // SSL_set_tmp_rsa_callback does nothing.
 OPENSSL_EXPORT void SSL_set_tmp_rsa_callback(SSL *ssl,
                                              RSA *(*cb)(SSL *ssl, int is_export,
                                                         int keylength));
 
 // SSL_CTX_sess_connect returns zero.
 OPENSSL_EXPORT int SSL_CTX_sess_connect(const SSL_CTX *ctx);
 
 // SSL_CTX_sess_connect_good returns zero.
 OPENSSL_EXPORT int SSL_CTX_sess_connect_good(const SSL_CTX *ctx);
 
 // SSL_CTX_sess_connect_renegotiate returns zero.
 OPENSSL_EXPORT int SSL_CTX_sess_connect_renegotiate(const SSL_CTX *ctx);
 
 // SSL_CTX_sess_accept returns zero.
 OPENSSL_EXPORT int SSL_CTX_sess_accept(const SSL_CTX *ctx);
 
 // SSL_CTX_sess_accept_renegotiate returns zero.
 OPENSSL_EXPORT int SSL_CTX_sess_accept_renegotiate(const SSL_CTX *ctx);
 
 // SSL_CTX_sess_accept_good returns zero.
 OPENSSL_EXPORT int SSL_CTX_sess_accept_good(const SSL_CTX *ctx);
 
 // SSL_CTX_sess_hits returns zero.
 OPENSSL_EXPORT int SSL_CTX_sess_hits(const SSL_CTX *ctx);
 
 // SSL_CTX_sess_cb_hits returns zero.
 OPENSSL_EXPORT int SSL_CTX_sess_cb_hits(const SSL_CTX *ctx);
 
 // SSL_CTX_sess_misses returns zero.
 OPENSSL_EXPORT int SSL_CTX_sess_misses(const SSL_CTX *ctx);
 
 // SSL_CTX_sess_timeouts returns zero.
 OPENSSL_EXPORT int SSL_CTX_sess_timeouts(const SSL_CTX *ctx);
 
 // SSL_CTX_sess_cache_full returns zero.
 OPENSSL_EXPORT int SSL_CTX_sess_cache_full(const SSL_CTX *ctx);
 
 // SSL_cutthrough_complete calls |SSL_in_false_start|.
 OPENSSL_EXPORT int SSL_cutthrough_complete(const SSL *ssl);
 
 // SSL_num_renegotiations calls |SSL_total_renegotiations|.
 OPENSSL_EXPORT int SSL_num_renegotiations(const SSL *ssl);
 
 // SSL_CTX_need_tmp_RSA returns zero.
 OPENSSL_EXPORT int SSL_CTX_need_tmp_RSA(const SSL_CTX *ctx);
 
 // SSL_need_tmp_RSA returns zero.
 OPENSSL_EXPORT int SSL_need_tmp_RSA(const SSL *ssl);
 
 // SSL_CTX_set_tmp_rsa returns one.
 OPENSSL_EXPORT int SSL_CTX_set_tmp_rsa(SSL_CTX *ctx, const RSA *rsa);
 
 // SSL_set_tmp_rsa returns one.
 OPENSSL_EXPORT int SSL_set_tmp_rsa(SSL *ssl, const RSA *rsa);
 
 // SSL_CTX_get_read_ahead returns zero.
 OPENSSL_EXPORT int SSL_CTX_get_read_ahead(const SSL_CTX *ctx);
 
 // SSL_CTX_set_read_ahead returns one.
 OPENSSL_EXPORT int SSL_CTX_set_read_ahead(SSL_CTX *ctx, int yes);
 
 // SSL_get_read_ahead returns zero.
 OPENSSL_EXPORT int SSL_get_read_ahead(const SSL *ssl);
 
 // SSL_set_read_ahead returns one.
 OPENSSL_EXPORT int SSL_set_read_ahead(SSL *ssl, int yes);
 
 // SSL_set_state does nothing.
 OPENSSL_EXPORT void SSL_set_state(SSL *ssl, int state);
 
 // SSL_get_shared_ciphers writes an empty string to |buf| and returns a
 // pointer to |buf|, or NULL if |len| is less than or equal to zero.
 OPENSSL_EXPORT char *SSL_get_shared_ciphers(const SSL *ssl, char *buf, int len);
 
 // SSL_get_shared_sigalgs returns zero.
 OPENSSL_EXPORT int SSL_get_shared_sigalgs(SSL *ssl, int idx, int *psign,
                                           int *phash, int *psignandhash,
                                           uint8_t *rsig, uint8_t *rhash);
 
 // SSL_MODE_HANDSHAKE_CUTTHROUGH is the same as SSL_MODE_ENABLE_FALSE_START.
 #define SSL_MODE_HANDSHAKE_CUTTHROUGH SSL_MODE_ENABLE_FALSE_START
 
 // i2d_SSL_SESSION serializes |in|, as described in |i2d_SAMPLE|.
 //
 // Use |SSL_SESSION_to_bytes| instead.
 OPENSSL_EXPORT int i2d_SSL_SESSION(SSL_SESSION *in, uint8_t **pp);
 
 // d2i_SSL_SESSION parses a serialized session from the |length| bytes pointed
 // to by |*pp|, as described in |d2i_SAMPLE|.
 //
 // Use |SSL_SESSION_from_bytes| instead.
 OPENSSL_EXPORT SSL_SESSION *d2i_SSL_SESSION(SSL_SESSION **a, const uint8_t **pp,
                                             long length);
 
 // i2d_SSL_SESSION_bio serializes |session| and writes the result to |bio|. It
 // returns the number of bytes written on success and <= 0 on error.
 OPENSSL_EXPORT int i2d_SSL_SESSION_bio(BIO *bio, const SSL_SESSION *session);
 
 // d2i_SSL_SESSION_bio reads a serialized |SSL_SESSION| from |bio| and returns a
 // newly-allocated |SSL_SESSION| or NULL on error. If |out| is not NULL, it also
 // frees |*out| and sets |*out| to the new |SSL_SESSION|.
 OPENSSL_EXPORT SSL_SESSION *d2i_SSL_SESSION_bio(BIO *bio, SSL_SESSION **out);
 
 // ERR_load_SSL_strings does nothing.
 OPENSSL_EXPORT void ERR_load_SSL_strings(void);
 
 // SSL_load_error_strings does nothing.
 OPENSSL_EXPORT void SSL_load_error_strings(void);
 
 // SSL_CTX_set_tlsext_use_srtp calls |SSL_CTX_set_srtp_profiles|. It returns
 // zero on success and one on failure.
 //
 // WARNING: this function is dangerous because it breaks the usual return value
 // convention. Use |SSL_CTX_set_srtp_profiles| instead.
 OPENSSL_EXPORT int SSL_CTX_set_tlsext_use_srtp(SSL_CTX *ctx,
                                                const char *profiles);
 
 // SSL_set_tlsext_use_srtp calls |SSL_set_srtp_profiles|. It returns zero on
 // success and one on failure.
 //
 // WARNING: this function is dangerous because it breaks the usual return value
 // convention. Use |SSL_set_srtp_profiles| instead.
 OPENSSL_EXPORT int SSL_set_tlsext_use_srtp(SSL *ssl, const char *profiles);
 
 // SSL_get_current_compression returns NULL.
 OPENSSL_EXPORT const COMP_METHOD *SSL_get_current_compression(SSL *ssl);
 
 // SSL_get_current_expansion returns NULL.
 OPENSSL_EXPORT const COMP_METHOD *SSL_get_current_expansion(SSL *ssl);
 
 // SSL_get_server_tmp_key returns zero.
 OPENSSL_EXPORT int SSL_get_server_tmp_key(SSL *ssl, EVP_PKEY **out_key);
 
 // SSL_CTX_set_tmp_dh returns 1.
 OPENSSL_EXPORT int SSL_CTX_set_tmp_dh(SSL_CTX *ctx, const DH *dh);
 
 // SSL_set_tmp_dh returns 1.
 OPENSSL_EXPORT int SSL_set_tmp_dh(SSL *ssl, const DH *dh);
 
 // SSL_CTX_set_tmp_dh_callback does nothing.
 OPENSSL_EXPORT void SSL_CTX_set_tmp_dh_callback(
     SSL_CTX *ctx, DH *(*cb)(SSL *ssl, int is_export, int keylength));
 
 // SSL_set_tmp_dh_callback does nothing.
 OPENSSL_EXPORT void SSL_set_tmp_dh_callback(SSL *ssl,
                                             DH *(*cb)(SSL *ssl, int is_export,
                                                       int keylength));
 
 // SSL_CTX_set1_sigalgs takes |num_values| ints and interprets them as pairs
 // where the first is the nid of a hash function and the second is an
 // |EVP_PKEY_*| value. It configures the signature algorithm preferences for
 // |ctx| based on them and returns one on success or zero on error.
 //
 // This API is compatible with OpenSSL. However, BoringSSL-specific code should
 // prefer |SSL_CTX_set_signing_algorithm_prefs| because it's clearer and it's
 // more convenient to codesearch for specific algorithm values.
 OPENSSL_EXPORT int SSL_CTX_set1_sigalgs(SSL_CTX *ctx, const int *values,
                                         size_t num_values);
 
 // SSL_set1_sigalgs takes |num_values| ints and interprets them as pairs where
 // the first is the nid of a hash function and the second is an |EVP_PKEY_*|
 // value. It configures the signature algorithm preferences for |ssl| based on
 // them and returns one on success or zero on error.
 //
 // This API is compatible with OpenSSL. However, BoringSSL-specific code should
 // prefer |SSL_CTX_set_signing_algorithm_prefs| because it's clearer and it's
 // more convenient to codesearch for specific algorithm values.
 OPENSSL_EXPORT int SSL_set1_sigalgs(SSL *ssl, const int *values,
                                     size_t num_values);
 
 // SSL_CTX_set1_sigalgs_list takes a textual specification of a set of signature
 // algorithms and configures them on |ctx|. It returns one on success and zero
 // on error. See
 // https://www.openssl.org/docs/man1.1.0/man3/SSL_CTX_set1_sigalgs_list.html for
 // a description of the text format. Also note that TLS 1.3 names (e.g.
 // "rsa_pkcs1_md5_sha1") can also be used (as in OpenSSL, although OpenSSL
 // doesn't document that).
 //
 // This API is compatible with OpenSSL. However, BoringSSL-specific code should
 // prefer |SSL_CTX_set_signing_algorithm_prefs| because it's clearer and it's
 // more convenient to codesearch for specific algorithm values.
 OPENSSL_EXPORT int SSL_CTX_set1_sigalgs_list(SSL_CTX *ctx, const char *str);
 
 // SSL_set1_sigalgs_list takes a textual specification of a set of signature
 // algorithms and configures them on |ssl|. It returns one on success and zero
 // on error. See
 // https://www.openssl.org/docs/man1.1.0/man3/SSL_CTX_set1_sigalgs_list.html for
 // a description of the text format. Also note that TLS 1.3 names (e.g.
 // "rsa_pkcs1_md5_sha1") can also be used (as in OpenSSL, although OpenSSL
 // doesn't document that).
 //
 // This API is compatible with OpenSSL. However, BoringSSL-specific code should
 // prefer |SSL_CTX_set_signing_algorithm_prefs| because it's clearer and it's
 // more convenient to codesearch for specific algorithm values.
 OPENSSL_EXPORT int SSL_set1_sigalgs_list(SSL *ssl, const char *str);
 
 #define SSL_set_app_data(s, arg) (SSL_set_ex_data(s, 0, (char *)(arg)))
 #define SSL_get_app_data(s) (SSL_get_ex_data(s, 0))
 #define SSL_SESSION_set_app_data(s, a) \
   (SSL_SESSION_set_ex_data(s, 0, (char *)(a)))
 #define SSL_SESSION_get_app_data(s) (SSL_SESSION_get_ex_data(s, 0))
 #define SSL_CTX_get_app_data(ctx) (SSL_CTX_get_ex_data(ctx, 0))
 #define SSL_CTX_set_app_data(ctx, arg) \
   (SSL_CTX_set_ex_data(ctx, 0, (char *)(arg)))
 
 #define OpenSSL_add_ssl_algorithms() SSL_library_init()
 #define SSLeay_add_ssl_algorithms() SSL_library_init()
 
 #define SSL_get_cipher(ssl) SSL_CIPHER_get_name(SSL_get_current_cipher(ssl))
 #define SSL_get_cipher_bits(ssl, out_alg_bits) \
   SSL_CIPHER_get_bits(SSL_get_current_cipher(ssl), out_alg_bits)
 #define SSL_get_cipher_version(ssl) \
   SSL_CIPHER_get_version(SSL_get_current_cipher(ssl))
 #define SSL_get_cipher_name(ssl) \
   SSL_CIPHER_get_name(SSL_get_current_cipher(ssl))
 #define SSL_get_time(session) SSL_SESSION_get_time(session)
 #define SSL_set_time(session, time) SSL_SESSION_set_time((session), (time))
 #define SSL_get_timeout(session) SSL_SESSION_get_timeout(session)
 #define SSL_set_timeout(session, timeout) \
   SSL_SESSION_set_timeout((session), (timeout))
 
 struct ssl_comp_st {
   int id;
   const char *name;
   char *method;
 };
 
 DEFINE_STACK_OF(SSL_COMP)
 
 // The following flags do nothing and are included only to make it easier to
 // compile code with BoringSSL.
 #define SSL_MODE_AUTO_RETRY 0
 #define SSL_MODE_RELEASE_BUFFERS 0
 #define SSL_MODE_SEND_CLIENTHELLO_TIME 0
 #define SSL_MODE_SEND_SERVERHELLO_TIME 0
 #define SSL_OP_ALL 0
 #define SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION 0
 #define SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS 0
 #define SSL_OP_EPHEMERAL_RSA 0
 #define SSL_OP_LEGACY_SERVER_CONNECT 0
 #define SSL_OP_MICROSOFT_BIG_SSLV3_BUFFER 0
 #define SSL_OP_MICROSOFT_SESS_ID_BUG 0
 #define SSL_OP_MSIE_SSLV2_RSA_PADDING 0
 #define SSL_OP_NETSCAPE_CA_DN_BUG 0
 #define SSL_OP_NETSCAPE_CHALLENGE_BUG 0
 #define SSL_OP_NETSCAPE_DEMO_CIPHER_CHANGE_BUG 0
 #define SSL_OP_NETSCAPE_REUSE_CIPHER_CHANGE_BUG 0
 #define SSL_OP_NO_COMPRESSION 0
 #define SSL_OP_NO_RENEGOTIATION 0  // ssl_renegotiate_never is the default
 #define SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION 0
 #define SSL_OP_NO_SSLv2 0
 #define SSL_OP_NO_SSLv3 0
 #define SSL_OP_PKCS1_CHECK_1 0
 #define SSL_OP_PKCS1_CHECK_2 0
 #define SSL_OP_SINGLE_DH_USE 0
 #define SSL_OP_SINGLE_ECDH_USE 0
 #define SSL_OP_SSLEAY_080_CLIENT_DH_BUG 0
 #define SSL_OP_SSLREF2_REUSE_CERT_TYPE_BUG 0
 #define SSL_OP_TLS_BLOCK_PADDING_BUG 0
 #define SSL_OP_TLS_D5_BUG 0
 #define SSL_OP_TLS_ROLLBACK_BUG 0
 #define SSL_VERIFY_CLIENT_ONCE 0
 
 // SSL_cache_hit calls |SSL_session_reused|.
 OPENSSL_EXPORT int SSL_cache_hit(SSL *ssl);
 
 // SSL_get_default_timeout returns |SSL_DEFAULT_SESSION_TIMEOUT|.
 OPENSSL_EXPORT long SSL_get_default_timeout(const SSL *ssl);
 
 // SSL_get_version returns a string describing the TLS version used by |ssl|.
 // For example, "TLSv1.2" or "DTLSv1".
 OPENSSL_EXPORT const char *SSL_get_version(const SSL *ssl);
 
 // SSL_get_all_version_names outputs a list of possible strings
 // |SSL_get_version| may return in this version of BoringSSL. It writes at most
 // |max_out| entries to |out| and returns the total number it would have
 // written, if |max_out| had been large enough. |max_out| may be initially set
 // to zero to size the output.
 //
 // This function is only intended to help initialize tables in callers that want
 // possible strings pre-declared. This list would not be suitable to set a list
 // of supported features. It is in no particular order, and may contain
 // placeholder, experimental, or deprecated values that do not apply to every
 // caller. Future versions of BoringSSL may also return strings not in this
 // list, so this does not apply if, say, sending strings across services.
 OPENSSL_EXPORT size_t SSL_get_all_version_names(const char **out,
                                                 size_t max_out);
 
 // SSL_get_cipher_list returns the name of the |n|th cipher in the output of
 // |SSL_get_ciphers| or NULL if out of range. Use |SSL_get_ciphers| instead.
 OPENSSL_EXPORT const char *SSL_get_cipher_list(const SSL *ssl, int n);
 
 // SSL_CTX_set_client_cert_cb sets a callback which is called on the client if
 // the server requests a client certificate and none is configured. On success,
 // the callback should return one and set |*out_x509| to |*out_pkey| to a leaf
 // certificate and private key, respectively, passing ownership. It should
 // return zero to send no certificate and -1 to fail or pause the handshake. If
 // the handshake is paused, |SSL_get_error| will return
 // |SSL_ERROR_WANT_X509_LOOKUP|.
 //
 // The callback may call |SSL_get0_certificate_types| and
 // |SSL_get_client_CA_list| for information on the server's certificate request.
 //
 // Use |SSL_CTX_set_cert_cb| instead. Configuring intermediate certificates with
 // this function is confusing. This callback may not be registered concurrently
 // with |SSL_CTX_set_cert_cb| or |SSL_set_cert_cb|.
 OPENSSL_EXPORT void SSL_CTX_set_client_cert_cb(
     SSL_CTX *ctx, int (*cb)(SSL *ssl, X509 **out_x509, EVP_PKEY **out_pkey));
 
 #define SSL_NOTHING SSL_ERROR_NONE
 #define SSL_WRITING SSL_ERROR_WANT_WRITE
 #define SSL_READING SSL_ERROR_WANT_READ
 
 // SSL_want returns one of the above values to determine what the most recent
 // operation on |ssl| was blocked on. Use |SSL_get_error| instead.
 OPENSSL_EXPORT int SSL_want(const SSL *ssl);
 
 #define SSL_want_read(ssl) (SSL_want(ssl) == SSL_READING)
 #define SSL_want_write(ssl) (SSL_want(ssl) == SSL_WRITING)
 
 // SSL_get_finished writes up to |count| bytes of the Finished message sent by
 // |ssl| to |buf|. It returns the total untruncated length or zero if none has
 // been sent yet. At TLS 1.3 and later, it returns zero.
 //
 // Use |SSL_get_tls_unique| instead.
 OPENSSL_EXPORT size_t SSL_get_finished(const SSL *ssl, void *buf, size_t count);
 
 // SSL_get_peer_finished writes up to |count| bytes of the Finished message
 // received from |ssl|'s peer to |buf|. It returns the total untruncated length
 // or zero if none has been received yet. At TLS 1.3 and later, it returns
 // zero.
 //
 // Use |SSL_get_tls_unique| instead.
 OPENSSL_EXPORT size_t SSL_get_peer_finished(const SSL *ssl, void *buf,
                                             size_t count);
 
 // SSL_alert_type_string returns "!". Use |SSL_alert_type_string_long|
 // instead.
 OPENSSL_EXPORT const char *SSL_alert_type_string(int value);
 
 // SSL_alert_desc_string returns "!!". Use |SSL_alert_desc_string_long|
 // instead.
 OPENSSL_EXPORT const char *SSL_alert_desc_string(int value);
 
 // SSL_state_string returns "!!!!!!". Use |SSL_state_string_long| for a more
 // intelligible string.
 OPENSSL_EXPORT const char *SSL_state_string(const SSL *ssl);
 
 // SSL_TXT_* expand to strings.
 #define SSL_TXT_MEDIUM "MEDIUM"
 #define SSL_TXT_HIGH "HIGH"
 #define SSL_TXT_FIPS "FIPS"
 #define SSL_TXT_kRSA "kRSA"
 #define SSL_TXT_kDHE "kDHE"
 #define SSL_TXT_kEDH "kEDH"
 #define SSL_TXT_kECDHE "kECDHE"
 #define SSL_TXT_kEECDH "kEECDH"
 #define SSL_TXT_kPSK "kPSK"
 #define SSL_TXT_aRSA "aRSA"
 #define SSL_TXT_aECDSA "aECDSA"
 #define SSL_TXT_aPSK "aPSK"
 #define SSL_TXT_DH "DH"
 #define SSL_TXT_DHE "DHE"
 #define SSL_TXT_EDH "EDH"
 #define SSL_TXT_RSA "RSA"
 #define SSL_TXT_ECDH "ECDH"
 #define SSL_TXT_ECDHE "ECDHE"
 #define SSL_TXT_EECDH "EECDH"
 #define SSL_TXT_ECDSA "ECDSA"
 #define SSL_TXT_PSK "PSK"
 #define SSL_TXT_3DES "3DES"
 #define SSL_TXT_RC4 "RC4"
 #define SSL_TXT_AES128 "AES128"
 #define SSL_TXT_AES256 "AES256"
 #define SSL_TXT_AES "AES"
 #define SSL_TXT_AES_GCM "AESGCM"
 #define SSL_TXT_CHACHA20 "CHACHA20"
 #define SSL_TXT_MD5 "MD5"
 #define SSL_TXT_SHA1 "SHA1"
 #define SSL_TXT_SHA "SHA"
 #define SSL_TXT_SHA256 "SHA256"
 #define SSL_TXT_SHA384 "SHA384"
 #define SSL_TXT_SSLV3 "SSLv3"
 #define SSL_TXT_TLSV1 "TLSv1"
 #define SSL_TXT_TLSV1_1 "TLSv1.1"
 #define SSL_TXT_TLSV1_2 "TLSv1.2"
 #define SSL_TXT_TLSV1_3 "TLSv1.3"
 #define SSL_TXT_ALL "ALL"
 #define SSL_TXT_CMPDEF "COMPLEMENTOFDEFAULT"
 
 typedef struct ssl_conf_ctx_st SSL_CONF_CTX;
 
 // SSL_state returns |SSL_ST_INIT| if a handshake is in progress and |SSL_ST_OK|
 // otherwise.
 //
 // Use |SSL_is_init| instead.
 OPENSSL_EXPORT int SSL_state(const SSL *ssl);
 
 #define SSL_get_state(ssl) SSL_state(ssl)
 
 // SSL_set_shutdown causes |ssl| to behave as if the shutdown bitmask (see
 // |SSL_get_shutdown|) were |mode|. This may be used to skip sending or
 // receiving close_notify in |SSL_shutdown| by causing the implementation to
 // believe the events already happened.
 //
 // It is an error to use |SSL_set_shutdown| to unset a bit that has already been
 // set. Doing so will trigger an |assert| in debug builds and otherwise be
 // ignored.
 //
 // Use |SSL_CTX_set_quiet_shutdown| instead.
 OPENSSL_EXPORT void SSL_set_shutdown(SSL *ssl, int mode);
 
 // SSL_CTX_set_tmp_ecdh calls |SSL_CTX_set1_groups| with a one-element list
 // containing |ec_key|'s curve. The remainder of |ec_key| is ignored.
 OPENSSL_EXPORT int SSL_CTX_set_tmp_ecdh(SSL_CTX *ctx, const EC_KEY *ec_key);
 
 // SSL_set_tmp_ecdh calls |SSL_set1_groups| with a one-element list containing
 // |ec_key|'s curve. The remainder of |ec_key| is ignored.
 OPENSSL_EXPORT int SSL_set_tmp_ecdh(SSL *ssl, const EC_KEY *ec_key);
 
 #if !defined(OPENSSL_NO_FILESYSTEM)
 // SSL_add_dir_cert_subjects_to_stack lists files in directory |dir|. It calls
 // |SSL_add_file_cert_subjects_to_stack| on each file and returns one on success
 // or zero on error. This function is only available from the libdecrepit
 // library.
 OPENSSL_EXPORT int SSL_add_dir_cert_subjects_to_stack(STACK_OF(X509_NAME) *out,
                                                       const char *dir);
 #endif
 
 // SSL_CTX_enable_tls_channel_id calls |SSL_CTX_set_tls_channel_id_enabled|.
 OPENSSL_EXPORT int SSL_CTX_enable_tls_channel_id(SSL_CTX *ctx);
 
 // SSL_enable_tls_channel_id calls |SSL_set_tls_channel_id_enabled|.
 OPENSSL_EXPORT int SSL_enable_tls_channel_id(SSL *ssl);
 
 // BIO_f_ssl returns a |BIO_METHOD| that can wrap an |SSL*| in a |BIO*|. Note
 // that this has quite different behaviour from the version in OpenSSL (notably
 // that it doesn't try to auto renegotiate).
 //
 // IMPORTANT: if you are not curl, don't use this.
 OPENSSL_EXPORT const BIO_METHOD *BIO_f_ssl(void);
 
 // BIO_set_ssl sets |ssl| as the underlying connection for |bio|, which must
 // have been created using |BIO_f_ssl|. If |take_owership| is true, |bio| will
 // call |SSL_free| on |ssl| when closed. It returns one on success or something
 // other than one on error.
 OPENSSL_EXPORT long BIO_set_ssl(BIO *bio, SSL *ssl, int take_owership);
 
 // SSL_CTX_set_ecdh_auto returns one.
 #define SSL_CTX_set_ecdh_auto(ctx, onoff) 1
 
 // SSL_set_ecdh_auto returns one.
 #define SSL_set_ecdh_auto(ssl, onoff) 1
 
 // SSL_get_session returns a non-owning pointer to |ssl|'s session. For
 // historical reasons, which session it returns depends on |ssl|'s state.
 //
 // Prior to the start of the initial handshake, it returns the session the
 // caller set with |SSL_set_session|. After the initial handshake has finished
 // and if no additional handshakes are in progress, it returns the currently
 // active session. Its behavior is undefined while a handshake is in progress.
 //
 // If trying to add new sessions to an external session cache, use
 // |SSL_CTX_sess_set_new_cb| instead. In particular, using the callback is
 // required as of TLS 1.3. For compatibility, this function will return an
 // unresumable session which may be cached, but will never be resumed.
 //
 // If querying properties of the connection, use APIs on the |SSL| object.
 OPENSSL_EXPORT SSL_SESSION *SSL_get_session(const SSL *ssl);
 
 // SSL_get0_session is an alias for |SSL_get_session|.
 #define SSL_get0_session SSL_get_session
 
 // SSL_get1_session acts like |SSL_get_session| but returns a new reference to
 // the session.
 OPENSSL_EXPORT SSL_SESSION *SSL_get1_session(SSL *ssl);
 
 #define OPENSSL_INIT_NO_LOAD_SSL_STRINGS 0
 #define OPENSSL_INIT_LOAD_SSL_STRINGS 0
 #define OPENSSL_INIT_SSL_DEFAULT 0
 
 // OPENSSL_init_ssl returns one.
 OPENSSL_EXPORT int OPENSSL_init_ssl(uint64_t opts,
                                     const OPENSSL_INIT_SETTINGS *settings);
 
 // The following constants are legacy aliases for RSA-PSS with rsaEncryption
 // keys. Use the new names instead.
 #define SSL_SIGN_RSA_PSS_SHA256 SSL_SIGN_RSA_PSS_RSAE_SHA256
 #define SSL_SIGN_RSA_PSS_SHA384 SSL_SIGN_RSA_PSS_RSAE_SHA384
 #define SSL_SIGN_RSA_PSS_SHA512 SSL_SIGN_RSA_PSS_RSAE_SHA512
 
 // SSL_set_tlsext_status_type configures a client to request OCSP stapling if
 // |type| is |TLSEXT_STATUSTYPE_ocsp| and disables it otherwise. It returns one
 // on success and zero if handshake configuration has already been shed.
 //
 // Use |SSL_enable_ocsp_stapling| instead.
 OPENSSL_EXPORT int SSL_set_tlsext_status_type(SSL *ssl, int type);
 
 // SSL_get_tlsext_status_type returns |TLSEXT_STATUSTYPE_ocsp| if the client
 // requested OCSP stapling and |TLSEXT_STATUSTYPE_nothing| otherwise. On the
 // client, this reflects whether OCSP stapling was enabled via, e.g.,
 // |SSL_set_tlsext_status_type|. On the server, this is determined during the
 // handshake. It may be queried in callbacks set by |SSL_CTX_set_cert_cb|. The
 // result is undefined after the handshake completes.
 OPENSSL_EXPORT int SSL_get_tlsext_status_type(const SSL *ssl);
 
 // SSL_set_tlsext_status_ocsp_resp sets the OCSP response. It returns one on
 // success and zero on error. On success, |ssl| takes ownership of |resp|, which
 // must have been allocated by |OPENSSL_malloc|.
 //
 // Use |SSL_set_ocsp_response| instead.
 OPENSSL_EXPORT int SSL_set_tlsext_status_ocsp_resp(SSL *ssl, uint8_t *resp,
                                                    size_t resp_len);
 
 // SSL_get_tlsext_status_ocsp_resp sets |*out| to point to the OCSP response
 // from the server. It returns the length of the response. If there was no
 // response, it sets |*out| to NULL and returns zero.
 //
 // Use |SSL_get0_ocsp_response| instead.
 //
 // WARNING: the returned data is not guaranteed to be well formed.
 OPENSSL_EXPORT size_t SSL_get_tlsext_status_ocsp_resp(const SSL *ssl,
                                                       const uint8_t **out);
 
 // SSL_CTX_set_tlsext_status_cb configures the legacy OpenSSL OCSP callback and
 // returns one. Though the type signature is the same, this callback has
 // different behavior for client and server connections:
 //
 // For clients, the callback is called after certificate verification. It should
 // return one for success, zero for a bad OCSP response, and a negative number
 // for internal error. Instead, handle this as part of certificate verification.
 // (Historically, OpenSSL verified certificates just before parsing stapled OCSP
 // responses, but BoringSSL fixes this ordering. All server credentials are
 // available during verification.)
 //
 // Do not use this callback as a server. It is provided for compatibility
 // purposes only. For servers, it is called to configure server credentials. It
 // should return |SSL_TLSEXT_ERR_OK| on success, |SSL_TLSEXT_ERR_NOACK| to
 // ignore OCSP requests, or |SSL_TLSEXT_ERR_ALERT_FATAL| on error. It is usually
 // used to fetch OCSP responses on demand, which is not ideal. Instead, treat
 // OCSP responses like other server credentials, such as certificates or SCT
 // lists. Configure, store, and refresh them eagerly. This avoids downtime if
 // the CA's OCSP responder is briefly offline.
 OPENSSL_EXPORT int SSL_CTX_set_tlsext_status_cb(SSL_CTX *ctx,
                                                 int (*callback)(SSL *ssl,
                                                                 void *arg));
 
 // SSL_CTX_set_tlsext_status_arg sets additional data for
 // |SSL_CTX_set_tlsext_status_cb|'s callback and returns one.
 OPENSSL_EXPORT int SSL_CTX_set_tlsext_status_arg(SSL_CTX *ctx, void *arg);
 
 // The following symbols are compatibility aliases for reason codes used when
 // receiving an alert from the peer. Use the other names instead, which fit the
 // naming convention.
 //
 // TODO(davidben): Fix references to |SSL_R_TLSV1_CERTIFICATE_REQUIRED| and
 // remove the compatibility value. The others come from OpenSSL.
 #define SSL_R_TLSV1_UNSUPPORTED_EXTENSION \
   SSL_R_TLSV1_ALERT_UNSUPPORTED_EXTENSION
 #define SSL_R_TLSV1_CERTIFICATE_UNOBTAINABLE \
   SSL_R_TLSV1_ALERT_CERTIFICATE_UNOBTAINABLE
 #define SSL_R_TLSV1_UNRECOGNIZED_NAME SSL_R_TLSV1_ALERT_UNRECOGNIZED_NAME
 #define SSL_R_TLSV1_BAD_CERTIFICATE_STATUS_RESPONSE \
   SSL_R_TLSV1_ALERT_BAD_CERTIFICATE_STATUS_RESPONSE
 #define SSL_R_TLSV1_BAD_CERTIFICATE_HASH_VALUE \
   SSL_R_TLSV1_ALERT_BAD_CERTIFICATE_HASH_VALUE
 #define SSL_R_TLSV1_CERTIFICATE_REQUIRED SSL_R_TLSV1_ALERT_CERTIFICATE_REQUIRED
 
 // The following symbols are compatibility aliases for |SSL_GROUP_*|.
 #define SSL_CURVE_SECP256R1 SSL_GROUP_SECP256R1
 #define SSL_CURVE_SECP384R1 SSL_GROUP_SECP384R1
 #define SSL_CURVE_SECP521R1 SSL_GROUP_SECP521R1
 #define SSL_CURVE_X25519 SSL_GROUP_X25519
 #define SSL_CURVE_X25519_KYBER768_DRAFT00 SSL_GROUP_X25519_KYBER768_DRAFT00
 
 // SSL_get_curve_id calls |SSL_get_group_id|.
 OPENSSL_EXPORT uint16_t SSL_get_curve_id(const SSL *ssl);
 
 // SSL_get_curve_name calls |SSL_get_group_name|.
 OPENSSL_EXPORT const char *SSL_get_curve_name(uint16_t curve_id);
 
 // SSL_get_all_curve_names calls |SSL_get_all_group_names|.
 OPENSSL_EXPORT size_t SSL_get_all_curve_names(const char **out, size_t max_out);
 
 // SSL_CTX_set1_curves calls |SSL_CTX_set1_groups|.
 OPENSSL_EXPORT int SSL_CTX_set1_curves(SSL_CTX *ctx, const int *curves,
                                        size_t num_curves);
 
 // SSL_set1_curves calls |SSL_set1_groups|.
 OPENSSL_EXPORT int SSL_set1_curves(SSL *ssl, const int *curves,
                                    size_t num_curves);
 
 // SSL_CTX_set1_curves_list calls |SSL_CTX_set1_groups_list|.
 OPENSSL_EXPORT int SSL_CTX_set1_curves_list(SSL_CTX *ctx, const char *curves);
 
 // SSL_set1_curves_list calls |SSL_set1_groups_list|.
 OPENSSL_EXPORT int SSL_set1_curves_list(SSL *ssl, const char *curves);
 
 // TLSEXT_nid_unknown is a constant used in OpenSSL for
 // |SSL_get_negotiated_group| to return an unrecognized group. BoringSSL never
 // returns this value, but we define this constant for compatibility.
 #define TLSEXT_nid_unknown 0x1000000
 
 // SSL_CTX_check_private_key returns one if |ctx| has both a certificate and
 // private key, and zero otherwise.
 //
 // This function does not check consistency because the library checks when the
 // certificate and key are individually configured. However, if the private key
 // is configured before the certificate, inconsistent private keys are silently
 // dropped. Some callers are inadvertently relying on this function to detect
 // when this happens.
 //
 // Instead, callers should configure the certificate first, then the private
 // key, checking for errors in each. This function is then unnecessary.
 OPENSSL_EXPORT int SSL_CTX_check_private_key(const SSL_CTX *ctx);
 
 // SSL_check_private_key returns one if |ssl| has both a certificate and private
 // key, and zero otherwise.
 //
 // See discussion in |SSL_CTX_check_private_key|.
 OPENSSL_EXPORT int SSL_check_private_key(const SSL *ssl);
 
 
 // Compliance policy configurations
 //
 // A TLS connection has a large number of different parameters. Some are well
 // known, like cipher suites, but many are obscure and configuration functions
 // for them may not exist. These policy controls allow broad configuration
 // goals to be specified so that they can flow down to all the different
 // parameters of a TLS connection.
 
 enum ssl_compliance_policy_t BORINGSSL_ENUM_INT {
   // ssl_compliance_policy_none does nothing. However, since setting this
   // doesn't undo other policies it's an error to try and set it.
   ssl_compliance_policy_none,
 
   // ssl_compliance_policy_fips_202205 configures a TLS connection to use:
   //   * TLS 1.2 or 1.3
   //   * For TLS 1.2, only ECDHE_[RSA|ECDSA]_WITH_AES_*_GCM_SHA*.
   //   * For TLS 1.3, only AES-GCM
   //   * P-256 or P-384 for key agreement.
   //   * For server signatures, only PKCS#1/PSS with SHA256/384/512, or ECDSA
   //     with P-256 or P-384.
   //
   // Note: this policy can be configured even if BoringSSL has not been built in
   // FIPS mode. Call |FIPS_mode| to check that.
   //
   // Note: this setting aids with compliance with NIST requirements but does not
   // guarantee it. Careful reading of SP 800-52r2 is recommended.
   ssl_compliance_policy_fips_202205,
 
   // ssl_compliance_policy_wpa3_192_202304 configures a TLS connection to use:
   //   * TLS 1.2 or 1.3.
   //   * For TLS 1.2, only TLS_ECDHE_[ECDSA|RSA]_WITH_AES_256_GCM_SHA384.
   //   * For TLS 1.3, only AES-256-GCM.
   //   * P-384 for key agreement.
   //   * For handshake signatures, only ECDSA with P-384 and SHA-384, or RSA
   //     with SHA-384 or SHA-512.
   //
   // No limitations on the certificate chain nor leaf public key are imposed,
   // other than by the supported signature algorithms. But WPA3's "192-bit"
   // mode requires at least P-384 or 3072-bit along the chain. The caller must
   // enforce this themselves on the verified chain using functions such as
   // |X509_STORE_CTX_get0_chain|.
   //
   // Note that this setting is less secure than the default. The
   // implementation risks of using a more obscure primitive like P-384
   // dominate other considerations.
   ssl_compliance_policy_wpa3_192_202304,
 
   // ssl_compliance_policy_cnsa_202407 confingures a TLS connection to use:
   //   * For TLS 1.3, AES-256-GCM over AES-128-GCM over ChaCha20-Poly1305.
   //
   // I.e. it ensures that AES-GCM will be used whenever the client supports it.
   // The cipher suite configuration mini-language can be used to similarly
   // configure prior TLS versions if they are enabled.
   ssl_compliance_policy_cnsa_202407,
 };
 
 // SSL_CTX_set_compliance_policy configures various aspects of |ctx| based on
 // the given policy requirements. Subsequently calling other functions that
 // configure |ctx| may override |policy|, or may not. This should be the final
 // configuration function called in order to have defined behaviour. It's a
 // fatal error if |policy| is |ssl_compliance_policy_none|.
 OPENSSL_EXPORT int SSL_CTX_set_compliance_policy(
     SSL_CTX *ctx, enum ssl_compliance_policy_t policy);
 
 // SSL_CTX_get_compliance_policy returns the compliance policy configured on
 // |ctx|.
 OPENSSL_EXPORT enum ssl_compliance_policy_t SSL_CTX_get_compliance_policy(
     const SSL_CTX *ctx);
 
 // SSL_set_compliance_policy acts the same as |SSL_CTX_set_compliance_policy|,
 // but only configures a single |SSL*|.
 OPENSSL_EXPORT int SSL_set_compliance_policy(
     SSL *ssl, enum ssl_compliance_policy_t policy);
 
 // SSL_get_compliance_policy returns the compliance policy configured on
 // |ssl|.
 OPENSSL_EXPORT enum ssl_compliance_policy_t SSL_get_compliance_policy(
     const SSL *ssl);
 
 // Nodejs compatibility section (hidden).
 //
 // These defines exist for node.js, with the hope that we can eliminate the
 // need for them over time.
 
 #define SSLerr(function, reason) \
   ERR_put_error(ERR_LIB_SSL, 0, reason, __FILE__, __LINE__)
 
 
 // Preprocessor compatibility section (hidden).
 //
 // Historically, a number of APIs were implemented in OpenSSL as macros and
 // constants to 'ctrl' functions. To avoid breaking #ifdefs in consumers, this
 // section defines a number of legacy macros.
 //
 // Although using either the CTRL values or their wrapper macros in #ifdefs is
 // still supported, the CTRL values may not be passed to |SSL_ctrl| and
 // |SSL_CTX_ctrl|. Call the functions (previously wrapper macros) instead.
 //
 // See PORTING.md in the BoringSSL source tree for a table of corresponding
 // functions.
 // https://boringssl.googlesource.com/boringssl/+/main/PORTING.md#Replacements-for-values
 
 #define DTLS_CTRL_GET_TIMEOUT doesnt_exist
 #define DTLS_CTRL_HANDLE_TIMEOUT doesnt_exist
 #define SSL_CTRL_CHAIN doesnt_exist
 #define SSL_CTRL_CHAIN_CERT doesnt_exist
 #define SSL_CTRL_CHANNEL_ID doesnt_exist
 #define SSL_CTRL_CLEAR_EXTRA_CHAIN_CERTS doesnt_exist
 #define SSL_CTRL_CLEAR_MODE doesnt_exist
 #define SSL_CTRL_CLEAR_OPTIONS doesnt_exist
 #define SSL_CTRL_EXTRA_CHAIN_CERT doesnt_exist
 #define SSL_CTRL_GET_CHAIN_CERTS doesnt_exist
 #define SSL_CTRL_GET_CHANNEL_ID doesnt_exist
 #define SSL_CTRL_GET_CLIENT_CERT_TYPES doesnt_exist
 #define SSL_CTRL_GET_EXTRA_CHAIN_CERTS doesnt_exist
 #define SSL_CTRL_GET_MAX_CERT_LIST doesnt_exist
 #define SSL_CTRL_GET_NEGOTIATED_GROUP doesnt_exist
 #define SSL_CTRL_GET_NUM_RENEGOTIATIONS doesnt_exist
 #define SSL_CTRL_GET_READ_AHEAD doesnt_exist
 #define SSL_CTRL_GET_RI_SUPPORT doesnt_exist
 #define SSL_CTRL_GET_SERVER_TMP_KEY doesnt_exist
 #define SSL_CTRL_GET_SESSION_REUSED doesnt_exist
 #define SSL_CTRL_GET_SESS_CACHE_MODE doesnt_exist
 #define SSL_CTRL_GET_SESS_CACHE_SIZE doesnt_exist
 #define SSL_CTRL_GET_TLSEXT_TICKET_KEYS doesnt_exist
 #define SSL_CTRL_GET_TOTAL_RENEGOTIATIONS doesnt_exist
 #define SSL_CTRL_MODE doesnt_exist
 #define SSL_CTRL_NEED_TMP_RSA doesnt_exist
 #define SSL_CTRL_OPTIONS doesnt_exist
 #define SSL_CTRL_SESS_NUMBER doesnt_exist
 #define SSL_CTRL_SET_CURVES doesnt_exist
 #define SSL_CTRL_SET_CURVES_LIST doesnt_exist
 #define SSL_CTRL_SET_GROUPS doesnt_exist
 #define SSL_CTRL_SET_GROUPS_LIST doesnt_exist
 #define SSL_CTRL_SET_ECDH_AUTO doesnt_exist
 #define SSL_CTRL_SET_MAX_CERT_LIST doesnt_exist
 #define SSL_CTRL_SET_MAX_SEND_FRAGMENT doesnt_exist
 #define SSL_CTRL_SET_MSG_CALLBACK doesnt_exist
 #define SSL_CTRL_SET_MSG_CALLBACK_ARG doesnt_exist
 #define SSL_CTRL_SET_MTU doesnt_exist
 #define SSL_CTRL_SET_READ_AHEAD doesnt_exist
 #define SSL_CTRL_SET_SESS_CACHE_MODE doesnt_exist
 #define SSL_CTRL_SET_SESS_CACHE_SIZE doesnt_exist
 #define SSL_CTRL_SET_TLSEXT_HOSTNAME doesnt_exist
 #define SSL_CTRL_SET_TLSEXT_SERVERNAME_ARG doesnt_exist
 #define SSL_CTRL_SET_TLSEXT_SERVERNAME_CB doesnt_exist
 #define SSL_CTRL_SET_TLSEXT_TICKET_KEYS doesnt_exist
 #define SSL_CTRL_SET_TLSEXT_TICKET_KEY_CB doesnt_exist
 #define SSL_CTRL_SET_TMP_DH doesnt_exist
 #define SSL_CTRL_SET_TMP_DH_CB doesnt_exist
 #define SSL_CTRL_SET_TMP_ECDH doesnt_exist
 #define SSL_CTRL_SET_TMP_ECDH_CB doesnt_exist
 #define SSL_CTRL_SET_TMP_RSA doesnt_exist
 #define SSL_CTRL_SET_TMP_RSA_CB doesnt_exist
 
 // |BORINGSSL_PREFIX| already makes each of these symbols into macros, so there
 // is no need to define conflicting macros.
 #if !defined(BORINGSSL_PREFIX)
 
 #define DTLSv1_get_timeout DTLSv1_get_timeout
 #define DTLSv1_handle_timeout DTLSv1_handle_timeout
 #define SSL_CTX_add0_chain_cert SSL_CTX_add0_chain_cert
 #define SSL_CTX_add1_chain_cert SSL_CTX_add1_chain_cert
 #define SSL_CTX_add_extra_chain_cert SSL_CTX_add_extra_chain_cert
 #define SSL_CTX_clear_extra_chain_certs SSL_CTX_clear_extra_chain_certs
 #define SSL_CTX_clear_chain_certs SSL_CTX_clear_chain_certs
 #define SSL_CTX_clear_mode SSL_CTX_clear_mode
 #define SSL_CTX_clear_options SSL_CTX_clear_options
 #define SSL_CTX_get0_chain_certs SSL_CTX_get0_chain_certs
 #define SSL_CTX_get_extra_chain_certs SSL_CTX_get_extra_chain_certs
 #define SSL_CTX_get_max_cert_list SSL_CTX_get_max_cert_list
 #define SSL_CTX_get_mode SSL_CTX_get_mode
 #define SSL_CTX_get_options SSL_CTX_get_options
 #define SSL_CTX_get_read_ahead SSL_CTX_get_read_ahead
 #define SSL_CTX_get_session_cache_mode SSL_CTX_get_session_cache_mode
 #define SSL_CTX_get_tlsext_ticket_keys SSL_CTX_get_tlsext_ticket_keys
 #define SSL_CTX_need_tmp_RSA SSL_CTX_need_tmp_RSA
 #define SSL_CTX_sess_get_cache_size SSL_CTX_sess_get_cache_size
 #define SSL_CTX_sess_number SSL_CTX_sess_number
 #define SSL_CTX_sess_set_cache_size SSL_CTX_sess_set_cache_size
 #define SSL_CTX_set0_chain SSL_CTX_set0_chain
 #define SSL_CTX_set1_chain SSL_CTX_set1_chain
 #define SSL_CTX_set1_curves SSL_CTX_set1_curves
 #define SSL_CTX_set1_groups SSL_CTX_set1_groups
 #define SSL_CTX_set_max_cert_list SSL_CTX_set_max_cert_list
 #define SSL_CTX_set_max_send_fragment SSL_CTX_set_max_send_fragment
 #define SSL_CTX_set_mode SSL_CTX_set_mode
 #define SSL_CTX_set_msg_callback_arg SSL_CTX_set_msg_callback_arg
 #define SSL_CTX_set_options SSL_CTX_set_options
 #define SSL_CTX_set_read_ahead SSL_CTX_set_read_ahead
 #define SSL_CTX_set_session_cache_mode SSL_CTX_set_session_cache_mode
 #define SSL_CTX_set_tlsext_servername_arg SSL_CTX_set_tlsext_servername_arg
 #define SSL_CTX_set_tlsext_servername_callback \
   SSL_CTX_set_tlsext_servername_callback
 #define SSL_CTX_set_tlsext_ticket_key_cb SSL_CTX_set_tlsext_ticket_key_cb
 #define SSL_CTX_set_tlsext_ticket_keys SSL_CTX_set_tlsext_ticket_keys
 #define SSL_CTX_set_tmp_dh SSL_CTX_set_tmp_dh
 #define SSL_CTX_set_tmp_ecdh SSL_CTX_set_tmp_ecdh
 #define SSL_CTX_set_tmp_rsa SSL_CTX_set_tmp_rsa
 #define SSL_add0_chain_cert SSL_add0_chain_cert
 #define SSL_add1_chain_cert SSL_add1_chain_cert
 #define SSL_clear_chain_certs SSL_clear_chain_certs
 #define SSL_clear_mode SSL_clear_mode
 #define SSL_clear_options SSL_clear_options
 #define SSL_get0_certificate_types SSL_get0_certificate_types
 #define SSL_get0_chain_certs SSL_get0_chain_certs
 #define SSL_get_max_cert_list SSL_get_max_cert_list
 #define SSL_get_mode SSL_get_mode
 #define SSL_get_negotiated_group SSL_get_negotiated_group
 #define SSL_get_options SSL_get_options
 #define SSL_get_secure_renegotiation_support \
   SSL_get_secure_renegotiation_support
 #define SSL_need_tmp_RSA SSL_need_tmp_RSA
 #define SSL_num_renegotiations SSL_num_renegotiations
 #define SSL_session_reused SSL_session_reused
 #define SSL_set0_chain SSL_set0_chain
 #define SSL_set1_chain SSL_set1_chain
 #define SSL_set1_curves SSL_set1_curves
 #define SSL_set1_groups SSL_set1_groups
 #define SSL_set_max_cert_list SSL_set_max_cert_list
 #define SSL_set_max_send_fragment SSL_set_max_send_fragment
 #define SSL_set_mode SSL_set_mode
 #define SSL_set_msg_callback_arg SSL_set_msg_callback_arg
 #define SSL_set_mtu SSL_set_mtu
 #define SSL_set_options SSL_set_options
 #define SSL_set_tlsext_host_name SSL_set_tlsext_host_name
 #define SSL_set_tmp_dh SSL_set_tmp_dh
 #define SSL_set_tmp_ecdh SSL_set_tmp_ecdh
 #define SSL_set_tmp_rsa SSL_set_tmp_rsa
 #define SSL_total_renegotiations SSL_total_renegotiations
 
 #endif  // !defined(BORINGSSL_PREFIX)
 
 
 #if defined(__cplusplus)
 }  // extern C
 
 #if !defined(BORINGSSL_NO_CXX)
 
 extern "C++" {
 
 BSSL_NAMESPACE_BEGIN
 
 BORINGSSL_MAKE_DELETER(SSL, SSL_free)
 BORINGSSL_MAKE_DELETER(SSL_CREDENTIAL, SSL_CREDENTIAL_free)
 BORINGSSL_MAKE_UP_REF(SSL_CREDENTIAL, SSL_CREDENTIAL_up_ref)
 BORINGSSL_MAKE_DELETER(SSL_CTX, SSL_CTX_free)
 BORINGSSL_MAKE_UP_REF(SSL_CTX, SSL_CTX_up_ref)
 BORINGSSL_MAKE_DELETER(SSL_ECH_KEYS, SSL_ECH_KEYS_free)
 BORINGSSL_MAKE_UP_REF(SSL_ECH_KEYS, SSL_ECH_KEYS_up_ref)
 BORINGSSL_MAKE_DELETER(SSL_SESSION, SSL_SESSION_free)
 BORINGSSL_MAKE_UP_REF(SSL_SESSION, SSL_SESSION_up_ref)
 
 
 // *** DEPRECATED EXPERIMENT — DO NOT USE ***
 //
 // Split handshakes.
 //
 // WARNING: This mechanism is deprecated and should not be used. It is very
 // fragile and difficult to use correctly. The relationship between
 // configuration options across the two halves is ill-defined and not
 // self-consistent. Additionally, version skew across the two halves risks
 // unusual behavior and connection failure. New development should use the
 // handshake hints API. Existing deployments should migrate to handshake hints
 // to reduce the risk of service outages.
 //
 // Split handshakes allows the handshake part of a TLS connection to be
 // performed in a different process (or on a different machine) than the data
 // exchange. This only applies to servers.
 //
 // In the first part of a split handshake, an |SSL| (where the |SSL_CTX| has
 // been configured with |SSL_CTX_set_handoff_mode|) is used normally. Once the
 // ClientHello message has been received, the handshake will stop and
 // |SSL_get_error| will indicate |SSL_ERROR_HANDOFF|. At this point (and only
 // at this point), |SSL_serialize_handoff| can be called to write the “handoff”
 // state of the connection.
 //
 // Elsewhere, a fresh |SSL| can be used with |SSL_apply_handoff| to continue
 // the connection. The connection from the client is fed into this |SSL|, and
 // the handshake resumed. When the handshake stops again and |SSL_get_error|
 // indicates |SSL_ERROR_HANDBACK|, |SSL_serialize_handback| should be called to
 // serialize the state of the handshake again.
 //
 // Back at the first location, a fresh |SSL| can be used with
 // |SSL_apply_handback|. Then the client's connection can be processed mostly
 // as normal.
 //
 // Lastly, when a connection is in the handoff state, whether or not
 // |SSL_serialize_handoff| is called, |SSL_decline_handoff| will move it back
 // into a normal state where the connection can proceed without impact.
 //
 // WARNING: Currently only works with TLS 1.0–1.2.
 // WARNING: The serialisation formats are not yet stable: version skew may be
 //     fatal.
 // WARNING: The handback data contains sensitive key material and must be
 //     protected.
 // WARNING: Some calls on the final |SSL| will not work. Just as an example,
 //     calls like |SSL_get0_session_id_context| and |SSL_get_privatekey| won't
 //     work because the certificate used for handshaking isn't available.
 // WARNING: |SSL_apply_handoff| may trigger “msg” callback calls.
 
 OPENSSL_EXPORT void SSL_CTX_set_handoff_mode(SSL_CTX *ctx, bool on);
 OPENSSL_EXPORT void SSL_set_handoff_mode(SSL *SSL, bool on);
 OPENSSL_EXPORT bool SSL_serialize_handoff(const SSL *ssl, CBB *out,
                                           SSL_CLIENT_HELLO *out_hello);
 OPENSSL_EXPORT bool SSL_decline_handoff(SSL *ssl);
 OPENSSL_EXPORT bool SSL_apply_handoff(SSL *ssl, Span<const uint8_t> handoff);
 OPENSSL_EXPORT bool SSL_serialize_handback(const SSL *ssl, CBB *out);
 OPENSSL_EXPORT bool SSL_apply_handback(SSL *ssl, Span<const uint8_t> handback);
 
 // SSL_get_traffic_secrets sets |*out_read_traffic_secret| and
 // |*out_write_traffic_secret| to reference the current TLS 1.3 traffic secrets
 // for |ssl|. It returns true on success and false on error.
 //
 // This function is only valid on TLS 1.3 connections that have completed the
 // handshake. It is not valid for QUIC or DTLS, where multiple traffic secrets
 // may be active at a time.
 OPENSSL_EXPORT bool SSL_get_traffic_secrets(
     const SSL *ssl, Span<const uint8_t> *out_read_traffic_secret,
     Span<const uint8_t> *out_write_traffic_secret);
 
 // SSL_CTX_set_aes_hw_override_for_testing sets |override_value| to
 // override checking for aes hardware support for testing. If |override_value|
 // is set to true, the library will behave as if aes hardware support is
 // present. If it is set to false, the library will behave as if aes hardware
 // support is not present.
 OPENSSL_EXPORT void SSL_CTX_set_aes_hw_override_for_testing(
     SSL_CTX *ctx, bool override_value);
 
 // SSL_set_aes_hw_override_for_testing acts the same as
 // |SSL_CTX_set_aes_override_for_testing| but only configures a single |SSL*|.
 OPENSSL_EXPORT void SSL_set_aes_hw_override_for_testing(SSL *ssl,
                                                         bool override_value);
 
 BSSL_NAMESPACE_END
 
 }  // extern C++
 
 #endif  // !defined(BORINGSSL_NO_CXX)
 
 #endif
 
 #define SSL_R_APP_DATA_IN_HANDSHAKE 100
 #define SSL_R_ATTEMPT_TO_REUSE_SESSION_IN_DIFFERENT_CONTEXT 101
 #define SSL_R_BAD_ALERT 102
 #define SSL_R_BAD_CHANGE_CIPHER_SPEC 103
 #define SSL_R_BAD_DATA_RETURNED_BY_CALLBACK 104
 #define SSL_R_BAD_DH_P_LENGTH 105
 #define SSL_R_BAD_DIGEST_LENGTH 106
 #define SSL_R_BAD_ECC_CERT 107
 #define SSL_R_BAD_ECPOINT 108
 #define SSL_R_BAD_HANDSHAKE_RECORD 109
 #define SSL_R_BAD_HELLO_REQUEST 110
 #define SSL_R_BAD_LENGTH 111
 #define SSL_R_BAD_PACKET_LENGTH 112
 #define SSL_R_BAD_RSA_ENCRYPT 113
 #define SSL_R_BAD_SIGNATURE 114
 #define SSL_R_BAD_SRTP_MKI_VALUE 115
 #define SSL_R_BAD_SRTP_PROTECTION_PROFILE_LIST 116
 #define SSL_R_BAD_SSL_FILETYPE 117
 #define SSL_R_BAD_WRITE_RETRY 118
 #define SSL_R_BIO_NOT_SET 119
 #define SSL_R_BN_LIB 120
 #define SSL_R_BUFFER_TOO_SMALL 121
 #define SSL_R_CA_DN_LENGTH_MISMATCH 122
 #define SSL_R_CA_DN_TOO_LONG 123
 #define SSL_R_CCS_RECEIVED_EARLY 124
 #define SSL_R_CERTIFICATE_VERIFY_FAILED 125
 #define SSL_R_CERT_CB_ERROR 126
 #define SSL_R_CERT_LENGTH_MISMATCH 127
 #define SSL_R_CHANNEL_ID_NOT_P256 128
 #define SSL_R_CHANNEL_ID_SIGNATURE_INVALID 129
 #define SSL_R_CIPHER_OR_HASH_UNAVAILABLE 130
 #define SSL_R_CLIENTHELLO_PARSE_FAILED 131
 #define SSL_R_CLIENTHELLO_TLSEXT 132
 #define SSL_R_CONNECTION_REJECTED 133
 #define SSL_R_CONNECTION_TYPE_NOT_SET 134
 #define SSL_R_CUSTOM_EXTENSION_ERROR 135
 #define SSL_R_DATA_LENGTH_TOO_LONG 136
 #define SSL_R_DECODE_ERROR 137
 #define SSL_R_DECRYPTION_FAILED 138
 #define SSL_R_DECRYPTION_FAILED_OR_BAD_RECORD_MAC 139
 #define SSL_R_DH_PUBLIC_VALUE_LENGTH_IS_WRONG 140
 #define SSL_R_DH_P_TOO_LONG 141
 #define SSL_R_DIGEST_CHECK_FAILED 142
 #define SSL_R_DTLS_MESSAGE_TOO_BIG 143
 #define SSL_R_ECC_CERT_NOT_FOR_SIGNING 144
 #define SSL_R_EMS_STATE_INCONSISTENT 145
 #define SSL_R_ENCRYPTED_LENGTH_TOO_LONG 146
 #define SSL_R_ERROR_ADDING_EXTENSION 147
 #define SSL_R_ERROR_IN_RECEIVED_CIPHER_LIST 148
 #define SSL_R_ERROR_PARSING_EXTENSION 149
 #define SSL_R_EXCESSIVE_MESSAGE_SIZE 150
 #define SSL_R_EXTRA_DATA_IN_MESSAGE 151
 #define SSL_R_FRAGMENT_MISMATCH 152
 #define SSL_R_GOT_NEXT_PROTO_WITHOUT_EXTENSION 153
 #define SSL_R_HANDSHAKE_FAILURE_ON_CLIENT_HELLO 154
 #define SSL_R_HTTPS_PROXY_REQUEST 155
 #define SSL_R_HTTP_REQUEST 156
 #define SSL_R_INAPPROPRIATE_FALLBACK 157
 #define SSL_R_INVALID_COMMAND 158
 #define SSL_R_INVALID_MESSAGE 159
 #define SSL_R_INVALID_SSL_SESSION 160
 #define SSL_R_INVALID_TICKET_KEYS_LENGTH 161
 #define SSL_R_LENGTH_MISMATCH 162
 #define SSL_R_MISSING_EXTENSION 164
 #define SSL_R_MISSING_RSA_CERTIFICATE 165
 #define SSL_R_MISSING_TMP_DH_KEY 166
 #define SSL_R_MISSING_TMP_ECDH_KEY 167
 #define SSL_R_MIXED_SPECIAL_OPERATOR_WITH_GROUPS 168
 #define SSL_R_MTU_TOO_SMALL 169
 #define SSL_R_NEGOTIATED_BOTH_NPN_AND_ALPN 170
 #define SSL_R_NESTED_GROUP 171
 #define SSL_R_NO_CERTIFICATES_RETURNED 172
 #define SSL_R_NO_CERTIFICATE_ASSIGNED 173
 #define SSL_R_NO_CERTIFICATE_SET 174
 #define SSL_R_NO_CIPHERS_AVAILABLE 175
 #define SSL_R_NO_CIPHERS_PASSED 176
 #define SSL_R_NO_CIPHER_MATCH 177
 #define SSL_R_NO_COMPRESSION_SPECIFIED 178
 #define SSL_R_NO_METHOD_SPECIFIED 179
 #define SSL_R_NO_PRIVATE_KEY_ASSIGNED 181
 #define SSL_R_NO_RENEGOTIATION 182
 #define SSL_R_NO_REQUIRED_DIGEST 183
 #define SSL_R_NO_SHARED_CIPHER 184
 #define SSL_R_NULL_SSL_CTX 185
 #define SSL_R_NULL_SSL_METHOD_PASSED 186
 #define SSL_R_OLD_SESSION_CIPHER_NOT_RETURNED 187
 #define SSL_R_OLD_SESSION_VERSION_NOT_RETURNED 188
 #define SSL_R_OUTPUT_ALIASES_INPUT 189
 #define SSL_R_PARSE_TLSEXT 190
 #define SSL_R_PATH_TOO_LONG 191
 #define SSL_R_PEER_DID_NOT_RETURN_A_CERTIFICATE 192
 #define SSL_R_PEER_ERROR_UNSUPPORTED_CERTIFICATE_TYPE 193
 #define SSL_R_PROTOCOL_IS_SHUTDOWN 194
 #define SSL_R_PSK_IDENTITY_NOT_FOUND 195
 #define SSL_R_PSK_NO_CLIENT_CB 196
 #define SSL_R_PSK_NO_SERVER_CB 197
 #define SSL_R_READ_TIMEOUT_EXPIRED 198
 #define SSL_R_RECORD_LENGTH_MISMATCH 199
 #define SSL_R_RECORD_TOO_LARGE 200
 #define SSL_R_RENEGOTIATION_ENCODING_ERR 201
 #define SSL_R_RENEGOTIATION_MISMATCH 202
 #define SSL_R_REQUIRED_CIPHER_MISSING 203
 #define SSL_R_RESUMED_EMS_SESSION_WITHOUT_EMS_EXTENSION 204
 #define SSL_R_RESUMED_NON_EMS_SESSION_WITH_EMS_EXTENSION 205
 #define SSL_R_SCSV_RECEIVED_WHEN_RENEGOTIATING 206
 #define SSL_R_SERVERHELLO_TLSEXT 207
 #define SSL_R_SESSION_ID_CONTEXT_UNINITIALIZED 208
 #define SSL_R_SESSION_MAY_NOT_BE_CREATED 209
 #define SSL_R_SIGNATURE_ALGORITHMS_EXTENSION_SENT_BY_SERVER 210
 #define SSL_R_SRTP_COULD_NOT_ALLOCATE_PROFILES 211
 #define SSL_R_SRTP_UNKNOWN_PROTECTION_PROFILE 212
 #define SSL_R_SSL3_EXT_INVALID_SERVERNAME 213
 #define SSL_R_SSL_CTX_HAS_NO_DEFAULT_SSL_VERSION 214
 #define SSL_R_SSL_HANDSHAKE_FAILURE 215
 #define SSL_R_SSL_SESSION_ID_CONTEXT_TOO_LONG 216
 #define SSL_R_TLS_PEER_DID_NOT_RESPOND_WITH_CERTIFICATE_LIST 217
 #define SSL_R_TLS_RSA_ENCRYPTED_VALUE_LENGTH_IS_WRONG 218
 #define SSL_R_TOO_MANY_EMPTY_FRAGMENTS 219
 #define SSL_R_TOO_MANY_WARNING_ALERTS 220
 #define SSL_R_UNABLE_TO_FIND_ECDH_PARAMETERS 221
 #define SSL_R_UNEXPECTED_EXTENSION 222
 #define SSL_R_UNEXPECTED_MESSAGE 223
 #define SSL_R_UNEXPECTED_OPERATOR_IN_GROUP 224
 #define SSL_R_UNEXPECTED_RECORD 225
 #define SSL_R_UNINITIALIZED 226
 #define SSL_R_UNKNOWN_ALERT_TYPE 227
 #define SSL_R_UNKNOWN_CERTIFICATE_TYPE 228
 #define SSL_R_UNKNOWN_CIPHER_RETURNED 229
 #define SSL_R_UNKNOWN_CIPHER_TYPE 230
 #define SSL_R_UNKNOWN_DIGEST 231
 #define SSL_R_UNKNOWN_KEY_EXCHANGE_TYPE 232
 #define SSL_R_UNKNOWN_PROTOCOL 233
 #define SSL_R_UNKNOWN_SSL_VERSION 234
 #define SSL_R_UNKNOWN_STATE 235
 #define SSL_R_UNSAFE_LEGACY_RENEGOTIATION_DISABLED 236
 #define SSL_R_UNSUPPORTED_CIPHER 237
 #define SSL_R_UNSUPPORTED_COMPRESSION_ALGORITHM 238
 #define SSL_R_UNSUPPORTED_ELLIPTIC_CURVE 239
 #define SSL_R_UNSUPPORTED_PROTOCOL 240
 #define SSL_R_WRONG_CERTIFICATE_TYPE 241
 #define SSL_R_WRONG_CIPHER_RETURNED 242
 #define SSL_R_WRONG_CURVE 243
 #define SSL_R_WRONG_MESSAGE_TYPE 244
 #define SSL_R_WRONG_SIGNATURE_TYPE 245
 #define SSL_R_WRONG_SSL_VERSION 246
 #define SSL_R_WRONG_VERSION_NUMBER 247
 #define SSL_R_X509_LIB 248
 #define SSL_R_X509_VERIFICATION_SETUP_PROBLEMS 249
 #define SSL_R_SHUTDOWN_WHILE_IN_INIT 250
 #define SSL_R_INVALID_OUTER_RECORD_TYPE 251
 #define SSL_R_UNSUPPORTED_PROTOCOL_FOR_CUSTOM_KEY 252
 #define SSL_R_NO_COMMON_SIGNATURE_ALGORITHMS 253
 #define SSL_R_DOWNGRADE_DETECTED 254
 #define SSL_R_EXCESS_HANDSHAKE_DATA 255
 #define SSL_R_INVALID_COMPRESSION_LIST 256
 #define SSL_R_DUPLICATE_EXTENSION 257
 #define SSL_R_MISSING_KEY_SHARE 258
 #define SSL_R_INVALID_ALPN_PROTOCOL 259
 #define SSL_R_TOO_MANY_KEY_UPDATES 260
 #define SSL_R_BLOCK_CIPHER_PAD_IS_WRONG 261
 #define SSL_R_NO_CIPHERS_SPECIFIED 262
 #define SSL_R_RENEGOTIATION_EMS_MISMATCH 263
 #define SSL_R_DUPLICATE_KEY_SHARE 264
 #define SSL_R_NO_GROUPS_SPECIFIED 265
 #define SSL_R_NO_SHARED_GROUP 266
 #define SSL_R_PRE_SHARED_KEY_MUST_BE_LAST 267
 #define SSL_R_OLD_SESSION_PRF_HASH_MISMATCH 268
 #define SSL_R_INVALID_SCT_LIST 269
 #define SSL_R_TOO_MUCH_SKIPPED_EARLY_DATA 270
 #define SSL_R_PSK_IDENTITY_BINDER_COUNT_MISMATCH 271
 #define SSL_R_CANNOT_PARSE_LEAF_CERT 272
 #define SSL_R_SERVER_CERT_CHANGED 273
 #define SSL_R_CERTIFICATE_AND_PRIVATE_KEY_MISMATCH 274
 #define SSL_R_CANNOT_HAVE_BOTH_PRIVKEY_AND_METHOD 275
 #define SSL_R_TICKET_ENCRYPTION_FAILED 276
 #define SSL_R_ALPN_MISMATCH_ON_EARLY_DATA 277
 #define SSL_R_WRONG_VERSION_ON_EARLY_DATA 278
 #define SSL_R_UNEXPECTED_EXTENSION_ON_EARLY_DATA 279
 #define SSL_R_NO_SUPPORTED_VERSIONS_ENABLED 280
 #define SSL_R_EMPTY_HELLO_RETRY_REQUEST 282
 #define SSL_R_EARLY_DATA_NOT_IN_USE 283
 #define SSL_R_HANDSHAKE_NOT_COMPLETE 284
 #define SSL_R_NEGOTIATED_TB_WITHOUT_EMS_OR_RI 285
 #define SSL_R_SERVER_ECHOED_INVALID_SESSION_ID 286
 #define SSL_R_PRIVATE_KEY_OPERATION_FAILED 287
 #define SSL_R_SECOND_SERVERHELLO_VERSION_MISMATCH 288
 #define SSL_R_OCSP_CB_ERROR 289
 #define SSL_R_SSL_SESSION_ID_TOO_LONG 290
 #define SSL_R_APPLICATION_DATA_ON_SHUTDOWN 291
 #define SSL_R_CERT_DECOMPRESSION_FAILED 292
 #define SSL_R_UNCOMPRESSED_CERT_TOO_LARGE 293
 #define SSL_R_UNKNOWN_CERT_COMPRESSION_ALG 294
 #define SSL_R_INVALID_SIGNATURE_ALGORITHM 295
 #define SSL_R_DUPLICATE_SIGNATURE_ALGORITHM 296
 #define SSL_R_TLS13_DOWNGRADE 297
 #define SSL_R_QUIC_INTERNAL_ERROR 298
 #define SSL_R_WRONG_ENCRYPTION_LEVEL_RECEIVED 299
 #define SSL_R_TOO_MUCH_READ_EARLY_DATA 300
 #define SSL_R_INVALID_DELEGATED_CREDENTIAL 301
 #define SSL_R_KEY_USAGE_BIT_INCORRECT 302
 #define SSL_R_INCONSISTENT_CLIENT_HELLO 303
 #define SSL_R_CIPHER_MISMATCH_ON_EARLY_DATA 304
 #define SSL_R_QUIC_TRANSPORT_PARAMETERS_MISCONFIGURED 305
 #define SSL_R_UNEXPECTED_COMPATIBILITY_MODE 306
 #define SSL_R_NO_APPLICATION_PROTOCOL 307
 #define SSL_R_NEGOTIATED_ALPS_WITHOUT_ALPN 308
 #define SSL_R_ALPS_MISMATCH_ON_EARLY_DATA 309
 #define SSL_R_ECH_SERVER_CONFIG_AND_PRIVATE_KEY_MISMATCH 310
 #define SSL_R_ECH_SERVER_CONFIG_UNSUPPORTED_EXTENSION 311
 #define SSL_R_UNSUPPORTED_ECH_SERVER_CONFIG 312
 #define SSL_R_ECH_SERVER_WOULD_HAVE_NO_RETRY_CONFIGS 313
 #define SSL_R_INVALID_CLIENT_HELLO_INNER 314
 #define SSL_R_INVALID_ALPN_PROTOCOL_LIST 315
 #define SSL_R_COULD_NOT_PARSE_HINTS 316
 #define SSL_R_INVALID_ECH_PUBLIC_NAME 317
 #define SSL_R_INVALID_ECH_CONFIG_LIST 318
 #define SSL_R_ECH_REJECTED 319
 #define SSL_R_INVALID_OUTER_EXTENSION 320
 #define SSL_R_INCONSISTENT_ECH_NEGOTIATION 321
 #define SSL_R_INVALID_ALPS_CODEPOINT 322
 #define SSL_R_NO_MATCHING_ISSUER 323
 #define SSL_R_INVALID_SPAKE2PLUSV1_VALUE 324
 #define SSL_R_PAKE_EXHAUSTED 325
 #define SSL_R_PEER_PAKE_MISMATCH 326
 #define SSL_R_UNSUPPORTED_CREDENTIAL_LIST 327
 #define SSL_R_INVALID_TRUST_ANCHOR_LIST 328
 #define SSL_R_INVALID_CERTIFICATE_PROPERTY_LIST 329
 #define SSL_R_SSLV3_ALERT_CLOSE_NOTIFY 1000
 #define SSL_R_SSLV3_ALERT_UNEXPECTED_MESSAGE 1010
 #define SSL_R_SSLV3_ALERT_BAD_RECORD_MAC 1020
 #define SSL_R_TLSV1_ALERT_DECRYPTION_FAILED 1021
 #define SSL_R_TLSV1_ALERT_RECORD_OVERFLOW 1022
 #define SSL_R_SSLV3_ALERT_DECOMPRESSION_FAILURE 1030
 #define SSL_R_SSLV3_ALERT_HANDSHAKE_FAILURE 1040
 #define SSL_R_SSLV3_ALERT_NO_CERTIFICATE 1041
 #define SSL_R_SSLV3_ALERT_BAD_CERTIFICATE 1042
 #define SSL_R_SSLV3_ALERT_UNSUPPORTED_CERTIFICATE 1043
 #define SSL_R_SSLV3_ALERT_CERTIFICATE_REVOKED 1044
 #define SSL_R_SSLV3_ALERT_CERTIFICATE_EXPIRED 1045
 #define SSL_R_SSLV3_ALERT_CERTIFICATE_UNKNOWN 1046
 #define SSL_R_SSLV3_ALERT_ILLEGAL_PARAMETER 1047
 #define SSL_R_TLSV1_ALERT_UNKNOWN_CA 1048
 #define SSL_R_TLSV1_ALERT_ACCESS_DENIED 1049
 #define SSL_R_TLSV1_ALERT_DECODE_ERROR 1050
 #define SSL_R_TLSV1_ALERT_DECRYPT_ERROR 1051
 #define SSL_R_TLSV1_ALERT_EXPORT_RESTRICTION 1060
 #define SSL_R_TLSV1_ALERT_PROTOCOL_VERSION 1070
 #define SSL_R_TLSV1_ALERT_INSUFFICIENT_SECURITY 1071
 #define SSL_R_TLSV1_ALERT_INTERNAL_ERROR 1080
 #define SSL_R_TLSV1_ALERT_INAPPROPRIATE_FALLBACK 1086
 #define SSL_R_TLSV1_ALERT_USER_CANCELLED 1090
 #define SSL_R_TLSV1_ALERT_NO_RENEGOTIATION 1100
 #define SSL_R_TLSV1_ALERT_UNSUPPORTED_EXTENSION 1110
 #define SSL_R_TLSV1_ALERT_CERTIFICATE_UNOBTAINABLE 1111
 #define SSL_R_TLSV1_ALERT_UNRECOGNIZED_NAME 1112
 #define SSL_R_TLSV1_ALERT_BAD_CERTIFICATE_STATUS_RESPONSE 1113
 #define SSL_R_TLSV1_ALERT_BAD_CERTIFICATE_HASH_VALUE 1114
 #define SSL_R_TLSV1_ALERT_UNKNOWN_PSK_IDENTITY 1115
 #define SSL_R_TLSV1_ALERT_CERTIFICATE_REQUIRED 1116
 #define SSL_R_TLSV1_ALERT_NO_APPLICATION_PROTOCOL 1120
 #define SSL_R_TLSV1_ALERT_ECH_REQUIRED 1121
 #define SSL_R_PAKE_AND_KEY_SHARE_NOT_ALLOWED 1122
 
 #endif  // OPENSSL_HEADER_SSL_H