gnunet-android

aead.h (22675B)

---

 // Copyright 2014 The BoringSSL Authors
 //
 // 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_AEAD_H
 #define OPENSSL_HEADER_AEAD_H
 
 #include <openssl/base.h>   // IWYU pragma: export
 
 #if defined(__cplusplus)
 extern "C" {
 #endif
 
 
 // Authenticated Encryption with Additional Data.
 //
 // AEAD couples confidentiality and integrity in a single primitive. AEAD
 // algorithms take a key and then can seal and open individual messages. Each
 // message has a unique, per-message nonce and, optionally, additional data
 // which is authenticated but not included in the ciphertext.
 //
 // The |EVP_AEAD_CTX_init| function initialises an |EVP_AEAD_CTX| structure and
 // performs any precomputation needed to use |aead| with |key|. The length of
 // the key, |key_len|, is given in bytes.
 //
 // The |tag_len| argument contains the length of the tags, in bytes, and allows
 // for the processing of truncated authenticators. A zero value indicates that
 // the default tag length should be used and this is defined as
 // |EVP_AEAD_DEFAULT_TAG_LENGTH| in order to make the code clear. Using
 // truncated tags increases an attacker's chance of creating a valid forgery.
 // Be aware that the attacker's chance may increase more than exponentially as
 // would naively be expected.
 //
 // When no longer needed, the initialised |EVP_AEAD_CTX| structure must be
 // passed to |EVP_AEAD_CTX_cleanup|, which will deallocate any memory used.
 //
 // With an |EVP_AEAD_CTX| in hand, one can seal and open messages. These
 // operations are intended to meet the standard notions of privacy and
 // authenticity for authenticated encryption. For formal definitions see
 // Bellare and Namprempre, "Authenticated encryption: relations among notions
 // and analysis of the generic composition paradigm," Lecture Notes in Computer
 // Science B<1976> (2000), 531–545,
 // http://www-cse.ucsd.edu/~mihir/papers/oem.html.
 //
 // When sealing messages, a nonce must be given. The length of the nonce is
 // fixed by the AEAD in use and is returned by |EVP_AEAD_nonce_length|. *The
 // nonce must be unique for all messages with the same key*. This is critically
 // important - nonce reuse may completely undermine the security of the AEAD.
 // Nonces may be predictable and public, so long as they are unique. Uniqueness
 // may be achieved with a simple counter or, if large enough, may be generated
 // randomly. The nonce must be passed into the "open" operation by the receiver
 // so must either be implicit (e.g. a counter), or must be transmitted along
 // with the sealed message.
 //
 // The "seal" and "open" operations are atomic - an entire message must be
 // encrypted or decrypted in a single call. Large messages may have to be split
 // up in order to accommodate this. When doing so, be mindful of the need not to
 // repeat nonces and the possibility that an attacker could duplicate, reorder
 // or drop message chunks. For example, using a single key for a given (large)
 // message and sealing chunks with nonces counting from zero would be secure as
 // long as the number of chunks was securely transmitted. (Otherwise an
 // attacker could truncate the message by dropping chunks from the end.)
 //
 // The number of chunks could be transmitted by prefixing it to the plaintext,
 // for example. This also assumes that no other message would ever use the same
 // key otherwise the rule that nonces must be unique for a given key would be
 // violated.
 //
 // The "seal" and "open" operations also permit additional data to be
 // authenticated via the |ad| parameter. This data is not included in the
 // ciphertext and must be identical for both the "seal" and "open" call. This
 // permits implicit context to be authenticated but may be empty if not needed.
 //
 // The "seal" and "open" operations may work in-place if the |out| and |in|
 // arguments are equal. Otherwise, if |out| and |in| alias, input data may be
 // overwritten before it is read. This situation will cause an error.
 //
 // The "seal" and "open" operations return one on success and zero on error.
 
 
 // AEAD algorithms.
 
 // EVP_aead_aes_128_gcm is AES-128 in Galois Counter Mode.
 //
 // Note: AES-GCM should only be used with 12-byte (96-bit) nonces. Although it
 // is specified to take a variable-length nonce, nonces with other lengths are
 // effectively randomized, which means one must consider collisions. Unless
 // implementing an existing protocol which has already specified incorrect
 // parameters, only use 12-byte nonces.
 OPENSSL_EXPORT const EVP_AEAD *EVP_aead_aes_128_gcm(void);
 
 // EVP_aead_aes_192_gcm is AES-192 in Galois Counter Mode.
 //
 // WARNING: AES-192 is superfluous and shouldn't exist. NIST should never have
 // defined it. Use only when interop with another system requires it, never
 // de novo.
 //
 // Note: AES-GCM should only be used with 12-byte (96-bit) nonces. Although it
 // is specified to take a variable-length nonce, nonces with other lengths are
 // effectively randomized, which means one must consider collisions. Unless
 // implementing an existing protocol which has already specified incorrect
 // parameters, only use 12-byte nonces.
 OPENSSL_EXPORT const EVP_AEAD *EVP_aead_aes_192_gcm(void);
 
 // EVP_aead_aes_256_gcm is AES-256 in Galois Counter Mode.
 //
 // Note: AES-GCM should only be used with 12-byte (96-bit) nonces. Although it
 // is specified to take a variable-length nonce, nonces with other lengths are
 // effectively randomized, which means one must consider collisions. Unless
 // implementing an existing protocol which has already specified incorrect
 // parameters, only use 12-byte nonces.
 OPENSSL_EXPORT const EVP_AEAD *EVP_aead_aes_256_gcm(void);
 
 // EVP_aead_chacha20_poly1305 is the AEAD built from ChaCha20 and
 // Poly1305 as described in RFC 8439.
 OPENSSL_EXPORT const EVP_AEAD *EVP_aead_chacha20_poly1305(void);
 
 // EVP_aead_xchacha20_poly1305 is ChaCha20-Poly1305 with an extended nonce that
 // makes random generation of nonces safe.
 OPENSSL_EXPORT const EVP_AEAD *EVP_aead_xchacha20_poly1305(void);
 
 // EVP_aead_aes_128_ctr_hmac_sha256 is AES-128 in CTR mode with HMAC-SHA256 for
 // authentication. The nonce is 12 bytes; the bottom 32-bits are used as the
 // block counter, thus the maximum plaintext size is 64GB.
 OPENSSL_EXPORT const EVP_AEAD *EVP_aead_aes_128_ctr_hmac_sha256(void);
 
 // EVP_aead_aes_256_ctr_hmac_sha256 is AES-256 in CTR mode with HMAC-SHA256 for
 // authentication. See |EVP_aead_aes_128_ctr_hmac_sha256| for details.
 OPENSSL_EXPORT const EVP_AEAD *EVP_aead_aes_256_ctr_hmac_sha256(void);
 
 // EVP_aead_aes_128_gcm_siv is AES-128 in GCM-SIV mode. See RFC 8452.
 OPENSSL_EXPORT const EVP_AEAD *EVP_aead_aes_128_gcm_siv(void);
 
 // EVP_aead_aes_256_gcm_siv is AES-256 in GCM-SIV mode. See RFC 8452.
 OPENSSL_EXPORT const EVP_AEAD *EVP_aead_aes_256_gcm_siv(void);
 
 // EVP_aead_aes_128_gcm_randnonce is AES-128 in Galois Counter Mode with
 // internal nonce generation. The 12-byte nonce is appended to the tag
 // and is generated internally. The "tag", for the purpurses of the API, is thus
 // 12 bytes larger. The nonce parameter when using this AEAD must be
 // zero-length. Since the nonce is random, a single key should not be used for
 // more than 2^32 seal operations.
 //
 // Warning: this is for use for FIPS compliance only. It is probably not
 // suitable for other uses. Using standard AES-GCM AEADs allows one to achieve
 // the same effect, but gives more control over nonce storage.
 OPENSSL_EXPORT const EVP_AEAD *EVP_aead_aes_128_gcm_randnonce(void);
 
 // EVP_aead_aes_256_gcm_randnonce is AES-256 in Galois Counter Mode with
 // internal nonce generation. The 12-byte nonce is appended to the tag
 // and is generated internally. The "tag", for the purpurses of the API, is thus
 // 12 bytes larger. The nonce parameter when using this AEAD must be
 // zero-length. Since the nonce is random, a single key should not be used for
 // more than 2^32 seal operations.
 //
 // Warning: this is for use for FIPS compliance only. It is probably not
 // suitable for other uses. Using standard AES-GCM AEADs allows one to achieve
 // the same effect, but gives more control over nonce storage.
 OPENSSL_EXPORT const EVP_AEAD *EVP_aead_aes_256_gcm_randnonce(void);
 
 // EVP_aead_aes_128_ccm_bluetooth is AES-128-CCM with M=4 and L=2 (4-byte tags
 // and 13-byte nonces), as decribed in the Bluetooth Core Specification v5.0,
 // Volume 6, Part E, Section 1.
 OPENSSL_EXPORT const EVP_AEAD *EVP_aead_aes_128_ccm_bluetooth(void);
 
 // EVP_aead_aes_128_ccm_bluetooth_8 is AES-128-CCM with M=8 and L=2 (8-byte tags
 // and 13-byte nonces), as used in the Bluetooth Mesh Networking Specification
 // v1.0.
 OPENSSL_EXPORT const EVP_AEAD *EVP_aead_aes_128_ccm_bluetooth_8(void);
 
 // EVP_aead_aes_128_ccm_matter is AES-128-CCM with M=16 and L=2 (16-byte tags
 // and 13-byte nonces), as used in the Matter specification.
 OPENSSL_EXPORT const EVP_AEAD *EVP_aead_aes_128_ccm_matter(void);
 
 // EVP_has_aes_hardware returns one if we enable hardware support for fast and
 // constant-time AES-GCM.
 OPENSSL_EXPORT int EVP_has_aes_hardware(void);
 
 // EVP_aead_aes_128_eax is AES-128 in EAX mode. Nonce size is either 12 or 16
 // bytes, tag length is 16 bytes.
 // See https://doi.org/10.1007/978-3-540-25937-4_25.
 OPENSSL_EXPORT const EVP_AEAD *EVP_aead_aes_128_eax(void);
 
 // EVP_aead_aes_256_eax is AES-256 in EAX mode. Nonce size is either 12 or 16
 // bytes, tag length is 16 bytes.
 // See https://doi.org/10.1007/978-3-540-25937-4_25.
 OPENSSL_EXPORT const EVP_AEAD *EVP_aead_aes_256_eax(void);
 
 
 // Utility functions.
 
 // EVP_AEAD_key_length returns the length, in bytes, of the keys used by
 // |aead|.
 OPENSSL_EXPORT size_t EVP_AEAD_key_length(const EVP_AEAD *aead);
 
 // EVP_AEAD_nonce_length returns the length, in bytes, of the per-message nonce
 // for |aead|.
 OPENSSL_EXPORT size_t EVP_AEAD_nonce_length(const EVP_AEAD *aead);
 
 // EVP_AEAD_max_overhead returns the maximum number of additional bytes added
 // by the act of sealing data with |aead|.
 OPENSSL_EXPORT size_t EVP_AEAD_max_overhead(const EVP_AEAD *aead);
 
 // EVP_AEAD_max_tag_len returns the maximum tag length when using |aead|. This
 // is the largest value that can be passed as |tag_len| to
 // |EVP_AEAD_CTX_init|.
 OPENSSL_EXPORT size_t EVP_AEAD_max_tag_len(const EVP_AEAD *aead);
 
 
 // AEAD operations.
 
 union evp_aead_ctx_st_state {
   uint8_t opaque[560];
   uint64_t alignment;
 };
 
 // An evp_aead_ctx_st (typedefed as |EVP_AEAD_CTX| in base.h) represents an AEAD
 // algorithm configured with a specific key and message-independent IV.
 struct evp_aead_ctx_st {
   const EVP_AEAD *aead;
   union evp_aead_ctx_st_state state;
   // tag_len may contain the actual length of the authentication tag if it is
   // known at initialization time.
   uint8_t tag_len;
 };
 
 // EVP_AEAD_MAX_KEY_LENGTH contains the maximum key length used by
 // any AEAD defined in this header.
 #define EVP_AEAD_MAX_KEY_LENGTH 80
 
 // EVP_AEAD_MAX_NONCE_LENGTH contains the maximum nonce length used by
 // any AEAD defined in this header.
 #define EVP_AEAD_MAX_NONCE_LENGTH 24
 
 // EVP_AEAD_MAX_OVERHEAD contains the maximum overhead used by any AEAD
 // defined in this header.
 #define EVP_AEAD_MAX_OVERHEAD 64
 
 // EVP_AEAD_DEFAULT_TAG_LENGTH is a magic value that can be passed to
 // EVP_AEAD_CTX_init to indicate that the default tag length for an AEAD should
 // be used.
 #define EVP_AEAD_DEFAULT_TAG_LENGTH 0
 
 // EVP_AEAD_CTX_zero sets an uninitialized |ctx| to the zero state. It must be
 // initialized with |EVP_AEAD_CTX_init| before use. It is safe, but not
 // necessary, to call |EVP_AEAD_CTX_cleanup| in this state. This may be used for
 // more uniform cleanup of |EVP_AEAD_CTX|.
 OPENSSL_EXPORT void EVP_AEAD_CTX_zero(EVP_AEAD_CTX *ctx);
 
 // EVP_AEAD_CTX_new allocates an |EVP_AEAD_CTX|, calls |EVP_AEAD_CTX_init| and
 // returns the |EVP_AEAD_CTX|, or NULL on error.
 OPENSSL_EXPORT EVP_AEAD_CTX *EVP_AEAD_CTX_new(const EVP_AEAD *aead,
                                               const uint8_t *key,
                                               size_t key_len, size_t tag_len);
 
 // EVP_AEAD_CTX_free calls |EVP_AEAD_CTX_cleanup| and |OPENSSL_free| on
 // |ctx|.
 OPENSSL_EXPORT void EVP_AEAD_CTX_free(EVP_AEAD_CTX *ctx);
 
 // EVP_AEAD_CTX_init initializes |ctx| for the given AEAD algorithm. The |impl|
 // argument is ignored and should be NULL. Authentication tags may be truncated
 // by passing a size as |tag_len|. A |tag_len| of zero indicates the default
 // tag length and this is defined as EVP_AEAD_DEFAULT_TAG_LENGTH for
 // readability.
 //
 // Returns 1 on success. Otherwise returns 0 and pushes to the error stack. In
 // the error case, you do not need to call |EVP_AEAD_CTX_cleanup|, but it's
 // harmless to do so.
 OPENSSL_EXPORT int EVP_AEAD_CTX_init(EVP_AEAD_CTX *ctx, const EVP_AEAD *aead,
                                      const uint8_t *key, size_t key_len,
                                      size_t tag_len, ENGINE *impl);
 
 // EVP_AEAD_CTX_cleanup frees any data allocated by |ctx|. It is a no-op to
 // call |EVP_AEAD_CTX_cleanup| on a |EVP_AEAD_CTX| that has been |memset| to
 // all zeros.
 OPENSSL_EXPORT void EVP_AEAD_CTX_cleanup(EVP_AEAD_CTX *ctx);
 
 // EVP_AEAD_CTX_seal encrypts and authenticates |in_len| bytes from |in| and
 // authenticates |ad_len| bytes from |ad| and writes the result to |out|. It
 // returns one on success and zero otherwise.
 //
 // This function may be called concurrently with itself or any other seal/open
 // function on the same |EVP_AEAD_CTX|.
 //
 // At most |max_out_len| bytes are written to |out| and, in order to ensure
 // success, |max_out_len| should be |in_len| plus the result of
 // |EVP_AEAD_max_overhead|. On successful return, |*out_len| is set to the
 // actual number of bytes written.
 //
 // The length of |nonce|, |nonce_len|, must be equal to the result of
 // |EVP_AEAD_nonce_length| for this AEAD.
 //
 // |EVP_AEAD_CTX_seal| never results in a partial output. If |max_out_len| is
 // insufficient, zero will be returned. If any error occurs, |out| will be
 // filled with zero bytes and |*out_len| set to zero.
 //
 // If |in| and |out| alias then |out| must be == |in|.
 OPENSSL_EXPORT int EVP_AEAD_CTX_seal(const EVP_AEAD_CTX *ctx, uint8_t *out,
                                      size_t *out_len, size_t max_out_len,
                                      const uint8_t *nonce, size_t nonce_len,
                                      const uint8_t *in, size_t in_len,
                                      const uint8_t *ad, size_t ad_len);
 
 // EVP_AEAD_CTX_open authenticates |in_len| bytes from |in| and |ad_len| bytes
 // from |ad| and decrypts at most |in_len| bytes into |out|. It returns one on
 // success and zero otherwise.
 //
 // This function may be called concurrently with itself or any other seal/open
 // function on the same |EVP_AEAD_CTX|.
 //
 // At most |in_len| bytes are written to |out|. In order to ensure success,
 // |max_out_len| should be at least |in_len|. On successful return, |*out_len|
 // is set to the the actual number of bytes written.
 //
 // The length of |nonce|, |nonce_len|, must be equal to the result of
 // |EVP_AEAD_nonce_length| for this AEAD.
 //
 // |EVP_AEAD_CTX_open| never results in a partial output. If |max_out_len| is
 // insufficient, zero will be returned. If any error occurs, |out| will be
 // filled with zero bytes and |*out_len| set to zero.
 //
 // If |in| and |out| alias then |out| must be == |in|.
 OPENSSL_EXPORT int EVP_AEAD_CTX_open(const EVP_AEAD_CTX *ctx, uint8_t *out,
                                      size_t *out_len, size_t max_out_len,
                                      const uint8_t *nonce, size_t nonce_len,
                                      const uint8_t *in, size_t in_len,
                                      const uint8_t *ad, size_t ad_len);
 
 // EVP_AEAD_CTX_seal_scatter encrypts and authenticates |in_len| bytes from |in|
 // and authenticates |ad_len| bytes from |ad|. It writes |in_len| bytes of
 // ciphertext to |out| and the authentication tag to |out_tag|. It returns one
 // on success and zero otherwise.
 //
 // This function may be called concurrently with itself or any other seal/open
 // function on the same |EVP_AEAD_CTX|.
 //
 // Exactly |in_len| bytes are written to |out|, and up to
 // |EVP_AEAD_max_overhead+extra_in_len| bytes to |out_tag|. On successful
 // return, |*out_tag_len| is set to the actual number of bytes written to
 // |out_tag|.
 //
 // |extra_in| may point to an additional plaintext input buffer if the cipher
 // supports it. If present, |extra_in_len| additional bytes of plaintext are
 // encrypted and authenticated, and the ciphertext is written (before the tag)
 // to |out_tag|. |max_out_tag_len| must be sized to allow for the additional
 // |extra_in_len| bytes.
 //
 // The length of |nonce|, |nonce_len|, must be equal to the result of
 // |EVP_AEAD_nonce_length| for this AEAD.
 //
 // |EVP_AEAD_CTX_seal_scatter| never results in a partial output. If
 // |max_out_tag_len| is insufficient, zero will be returned. If any error
 // occurs, |out| and |out_tag| will be filled with zero bytes and |*out_tag_len|
 // set to zero.
 //
 // If |in| and |out| alias then |out| must be == |in|. |out_tag| may not alias
 // any other argument.
 OPENSSL_EXPORT int EVP_AEAD_CTX_seal_scatter(
     const EVP_AEAD_CTX *ctx, uint8_t *out, uint8_t *out_tag,
     size_t *out_tag_len, size_t max_out_tag_len, const uint8_t *nonce,
     size_t nonce_len, const uint8_t *in, size_t in_len, const uint8_t *extra_in,
     size_t extra_in_len, const uint8_t *ad, size_t ad_len);
 
 // EVP_AEAD_CTX_open_gather decrypts and authenticates |in_len| bytes from |in|
 // and authenticates |ad_len| bytes from |ad| using |in_tag_len| bytes of
 // authentication tag from |in_tag|. If successful, it writes |in_len| bytes of
 // plaintext to |out|. It returns one on success and zero otherwise.
 //
 // This function may be called concurrently with itself or any other seal/open
 // function on the same |EVP_AEAD_CTX|.
 //
 // The length of |nonce|, |nonce_len|, must be equal to the result of
 // |EVP_AEAD_nonce_length| for this AEAD.
 //
 // |EVP_AEAD_CTX_open_gather| never results in a partial output. If any error
 // occurs, |out| will be filled with zero bytes.
 //
 // If |in| and |out| alias then |out| must be == |in|.
 OPENSSL_EXPORT int EVP_AEAD_CTX_open_gather(
     const EVP_AEAD_CTX *ctx, uint8_t *out, const uint8_t *nonce,
     size_t nonce_len, const uint8_t *in, size_t in_len, const uint8_t *in_tag,
     size_t in_tag_len, const uint8_t *ad, size_t ad_len);
 
 // EVP_AEAD_CTX_aead returns the underlying AEAD for |ctx|, or NULL if one has
 // not been set.
 OPENSSL_EXPORT const EVP_AEAD *EVP_AEAD_CTX_aead(const EVP_AEAD_CTX *ctx);
 
 
 // TLS-specific AEAD algorithms.
 //
 // These AEAD primitives do not meet the definition of generic AEADs. They are
 // all specific to TLS and should not be used outside of that context. They must
 // be initialized with |EVP_AEAD_CTX_init_with_direction|, are stateful, and may
 // not be used concurrently. Any nonces are used as IVs, so they must be
 // unpredictable. They only accept an |ad| parameter of length 11 (the standard
 // TLS one with length omitted).
 
 OPENSSL_EXPORT const EVP_AEAD *EVP_aead_aes_128_cbc_sha1_tls(void);
 OPENSSL_EXPORT const EVP_AEAD *EVP_aead_aes_128_cbc_sha1_tls_implicit_iv(void);
 
 OPENSSL_EXPORT const EVP_AEAD *EVP_aead_aes_128_cbc_sha256_tls(void);
 
 OPENSSL_EXPORT const EVP_AEAD *EVP_aead_aes_256_cbc_sha1_tls(void);
 OPENSSL_EXPORT const EVP_AEAD *EVP_aead_aes_256_cbc_sha1_tls_implicit_iv(void);
 
 OPENSSL_EXPORT const EVP_AEAD *EVP_aead_des_ede3_cbc_sha1_tls(void);
 OPENSSL_EXPORT const EVP_AEAD *EVP_aead_des_ede3_cbc_sha1_tls_implicit_iv(void);
 
 // EVP_aead_aes_128_gcm_tls12 is AES-128 in Galois Counter Mode using the TLS
 // 1.2 nonce construction.
 OPENSSL_EXPORT const EVP_AEAD *EVP_aead_aes_128_gcm_tls12(void);
 
 // EVP_aead_aes_256_gcm_tls12 is AES-256 in Galois Counter Mode using the TLS
 // 1.2 nonce construction.
 OPENSSL_EXPORT const EVP_AEAD *EVP_aead_aes_256_gcm_tls12(void);
 
 // EVP_aead_aes_128_gcm_tls13 is AES-128 in Galois Counter Mode using the TLS
 // 1.3 nonce construction.
 OPENSSL_EXPORT const EVP_AEAD *EVP_aead_aes_128_gcm_tls13(void);
 
 // EVP_aead_aes_256_gcm_tls13 is AES-256 in Galois Counter Mode using the TLS
 // 1.3 nonce construction.
 OPENSSL_EXPORT const EVP_AEAD *EVP_aead_aes_256_gcm_tls13(void);
 
 
 // Obscure functions.
 
 // evp_aead_direction_t denotes the direction of an AEAD operation.
 enum evp_aead_direction_t {
   evp_aead_open,
   evp_aead_seal,
 };
 
 // EVP_AEAD_CTX_init_with_direction calls |EVP_AEAD_CTX_init| for normal
 // AEADs. For TLS-specific and SSL3-specific AEADs, it initializes |ctx| for a
 // given direction.
 OPENSSL_EXPORT int EVP_AEAD_CTX_init_with_direction(
     EVP_AEAD_CTX *ctx, const EVP_AEAD *aead, const uint8_t *key, size_t key_len,
     size_t tag_len, enum evp_aead_direction_t dir);
 
 // EVP_AEAD_CTX_get_iv sets |*out_len| to the length of the IV for |ctx| and
 // sets |*out_iv| to point to that many bytes of the current IV. This is only
 // meaningful for AEADs with implicit IVs (i.e. CBC mode in TLS 1.0).
 //
 // It returns one on success or zero on error.
 OPENSSL_EXPORT int EVP_AEAD_CTX_get_iv(const EVP_AEAD_CTX *ctx,
                                        const uint8_t **out_iv, size_t *out_len);
 
 // EVP_AEAD_CTX_tag_len computes the exact byte length of the tag written by
 // |EVP_AEAD_CTX_seal_scatter| and writes it to |*out_tag_len|. It returns one
 // on success or zero on error. |in_len| and |extra_in_len| must equal the
 // arguments of the same names passed to |EVP_AEAD_CTX_seal_scatter|.
 OPENSSL_EXPORT int EVP_AEAD_CTX_tag_len(const EVP_AEAD_CTX *ctx,
                                         size_t *out_tag_len,
                                         const size_t in_len,
                                         const size_t extra_in_len);
 
 
 #if defined(__cplusplus)
 }  // extern C
 
 #if !defined(BORINGSSL_NO_CXX)
 extern "C++" {
 
 BSSL_NAMESPACE_BEGIN
 
 using ScopedEVP_AEAD_CTX =
     internal::StackAllocated<EVP_AEAD_CTX, void, EVP_AEAD_CTX_zero,
                              EVP_AEAD_CTX_cleanup>;
 
 BORINGSSL_MAKE_DELETER(EVP_AEAD_CTX, EVP_AEAD_CTX_free)
 
 BSSL_NAMESPACE_END
 
 }  // extern C++
 #endif
 
 #endif
 
 #endif  // OPENSSL_HEADER_AEAD_H