libmicrohttpd

fuzz_tls.c (78790B)

---

 /*
   This file is part of libmicrohttpd
   Copyright (C) 2026 Christian Grothoff
 
   This library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public
   License as published by the Free Software Foundation; either
   version 2.1 of the License, or (at your option) any later version.
 
   This library is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   Lesser General Public License for more details.
 
   You should have received a copy of the GNU Lesser General Public
   License along with this library.
   If not, see <http://www.gnu.org/licenses/>.
 */
 
 /**
  * @file fuzz/fuzz_tls.c
  * @brief In-process fuzzer for MHD's HTTPS/TLS integration layer.
  * @author Christian Grothoff
  *
  * The target is **MHD's own TLS plumbing**, not GnuTLS.  GnuTLS has its
  * own OSS-Fuzz project and its record parser is not our bug surface, so
  * only a small part of the input budget is spent throwing raw bytes at a
  * TLS socket.  What this harness really exercises is
  *
  *  - the @c MHD_USE_TLS daemon option surface: #MHD_OPTION_HTTPS_MEM_KEY,
  *    #MHD_OPTION_HTTPS_MEM_CERT, #MHD_OPTION_HTTPS_MEM_TRUST,
  *    #MHD_OPTION_HTTPS_MEM_DHPARAMS, #MHD_OPTION_HTTPS_PRIORITIES,
  *    #MHD_OPTION_HTTPS_PRIORITIES_APPEND, #MHD_OPTION_HTTPS_CRED_TYPE,
  *    #MHD_OPTION_HTTPS_KEY_PASSWORD, #MHD_OPTION_TLS_NO_ALPN and the SNI
  *    callback #MHD_OPTION_HTTPS_CERT_CALLBACK -- with malformed PEM
  *    blobs, mismatched key/certificate pairs, bogus priority strings,
  *    credential types MHD does not support, and an SNI callback that
  *    fails or answers with garbage;
  *  - the handshake state machine of connection_https.c
  *    (#MHD_TLS_CONN_INIT -> HANDSHAKING -> CONNECTED / TLS_FAILED) and
  *    what MHD does when the handshake fails, is abandoned half way, or
  *    the peer disappears while MHD is still in it;
  *  - the transition from the handshake to the ordinary HTTP parser, and
  *    the TLS receive/send adapters and @c gnutls_bye() shutdown path that
  *    the connection uses afterwards.
  *
  * To reach that last group the harness contains a real, in-process GnuTLS
  * *client*.  Both ends of an @c AF_UNIX @c socketpair() are non-blocking
  * and everything runs in one thread: the client's @c gnutls_handshake()
  * is called until it answers @c GNUTLS_E_AGAIN, then the daemon is pumped
  * with MHD_run(), and so on.  No threads, no ports, no TCP stack, and --
  * because the client's handshake timeout is set to
  * @c GNUTLS_INDEFINITE_TIMEOUT -- no wall clock either.
  *
  * Input format (see README):
  *
  *   byte 0   certificate/key pair selector (valid, mismatched, truncated,
  *            garbage, absent, or built from the fuzzer's own bytes)
  *   byte 1   which TLS daemon options to pass at all (bitmask)
  *              0x01 MHD_OPTION_HTTPS_MEM_TRUST
  *              0x02 MHD_OPTION_HTTPS_MEM_DHPARAMS
  *              0x04 MHD_OPTION_HTTPS_CERT_CALLBACK (the SNI callback)
  *              0x08 MHD_OPTION_HTTPS_PRIORITIES[_APPEND]
  *              0x10 MHD_OPTION_HTTPS_CRED_TYPE
  *              0x20 MHD_OPTION_TLS_NO_ALPN
  *              0x40 MHD_OPTION_HTTPS_KEY_PASSWORD
  *              0x80 use _PRIORITIES_APPEND instead of _PRIORITIES
  *   byte 2   priority string selector
  *   byte 3   bits 0-2 credential type (certificate, PSK, anon, SRP, IA,
  *                     and two values GnuTLS does not define)
  *            bits 3-5 SNI callback behaviour
  *            bit  6   trust blob: CA certificate or garbage
  *            bit  7   DH parameters: valid or garbage
  *   byte 4   bits 0-1 client mode
  *                     0 raw bytes, 1 real TLS client,
  *                     2 real client, handshake abandoned half way,
  *                     3 raw bytes shaped like TLS records
  *            bit  2   client sends a server name (SNI)
  *            bit  3   client presents a client certificate
  *            bits 4-5 client priority string selector
  *            bit  6   gnutls_bye() before closing
  *            bit  7   shutdown(SHUT_WR) before closing
  *   byte 5   low nibble  MHD_OPTION_CONNECTION_MEMORY_LIMIT selector
  *            high nibble event loop: MHD_run() vs MHD_get_fdset*() +
  *                        MHD_run_from_select*()
  *   byte 6   handler behaviour and introspection
  *              bits 0-1 response constructor
  *              bit  2   MHD_get_connection_info() for the TLS members
  *              bit  3   MHD_get_daemon_info()
  *              bit  4   MHD_set_connection_option()
  *              bit  5   answer 403 instead of 200
  *              bit  6   add a response header
  *              bit  7   MHD_quiesce_daemon() before stopping
  *   byte 7   bits 0-2 handshake round budget (client mode 2)
  *            bit  3   pass the HTTPS options to a daemon started *without*
  *                     MHD_USE_TLS
  *            bit  4   MHD_ALLOW_UPGRADE
  *            bits 5-7 extra pump rounds
  *   byte 8   how many bytes of the segment stream are spliced into the
  *            fuzzer-built PEM blobs (see cred_tbl entries 12 and 13)
  *   byte 9   bits 0-2 the server name the client presents, as an index
  *            into a small built-in table; an op 1 segment overrides it
  *   byte 10. a sequence of segments, each introduced by a little-endian
  *            16 bit header  (op << 14) | length
  *              op 0  send the payload
  *              op 1  the payload is the server name the *next* client
  *                    connection presents; nothing is sent
  *              op 2  send the payload and pump the daemon extra rounds
  *              op 3  close the connection, open a fresh one (which means
  *                    a fresh handshake), then send
  *
  * All ten configuration bytes are mandatory; a shorter input is
  * rejected.
  *
  * The segment encoding is byte-for-byte the one fuzz_request uses, and
  * `corpus/` is shared by every harness in this directory (see README
  * section 3), so the seeds below deliberately contain **no op 1
  * segment**: fuzz_request reads op 1 as the declared decoded request
  * body of its own body oracle, and would report a spurious finding when
  * it replays a fuzz_tls seed.  That is what byte 9 is for.  Inputs the
  * generator or a mutator produces may use op 1 freely -- they never end
  * up in `corpus/`.
  *
  * The certificates and keys are the ones from
  * `src/testcurl/https/tls_test_keys.h` (the CA certificate, the
  * CA-signed server certificate with its key, and the self-signed server
  * certificate with its key), reproduced verbatim so that this harness
  * stays a single translation unit.  The DH parameters are RFC 3526
  * group 14, as emitted by `certtool --get-dh-params --sec-param medium`.
  *
  * The whole harness is guarded by #HTTPS_SUPPORT: `contrib/oss-fuzz/
  * build.sh` configures `--disable-https` (that is what makes the
  * MemorySanitizer build possible), and in such a build this file must
  * still compile to a valid, trivially passing fuzz target.
  */
 
 #define FUZZ_HARNESS_NAME "fuzz_tls"
 #include "fuzz_common.h"
 
 /* Pulls in MHD_config.h, which is where HTTPS_SUPPORT is defined.  It
    must come before <microhttpd.h>: it also settles FD_SETSIZE. */
 #include "mhd_options.h"
 
 #ifdef HTTPS_SUPPORT
 
 #include <microhttpd.h>
 #include <gnutls/gnutls.h>
 #include <gnutls/abstract.h>
 #include <sys/socket.h>
 #include <netinet/in.h>
 #include <sys/select.h>
 #include <arpa/inet.h>
 
 /**
  * LeakSanitizer suppressions, compiled into the harness so that they
  * cannot be forgotten on the command line.
  *
  * There is exactly one entry and it is *not* about MHD.  GnuTLS 3.8.9
  * leaks the partially parsed certificate when a PEM certificate blob
  * ends before its "-----END CERTIFICATE-----" line:
  *
  *     gnutls_certificate_allocate_credentials (&cred);
  *     gnutls_certificate_set_x509_key_mem (cred, &truncated_cert,
  *                                          &good_key,
  *                                          GNUTLS_X509_FMT_PEM);
  *        -> GNUTLS_E_BASE64_UNEXPECTED_HEADER_ERROR (-207)
  *     gnutls_certificate_free_credentials (cred);
  *
  * leaks 9672 bytes in 57 allocations with no libmicrohttpd in the
  * picture at all (reproduced with a 40 line program).  MHD passes the
  * blob straight through and frees the credentials on every path, so
  * there is nothing for MHD to fix and nothing for this harness to find;
  * GnuTLS is fuzzed separately by its own OSS-Fuzz project.
  *
  * The suppression matches only allocations made *inside* GnuTLS's
  * certificate parser.  A credential object leaked by MHD itself is a
  * direct leak from gnutls_certificate_allocate_credentials() and is
  * still reported, as is every other MHD allocation.
  */
 const char *
 __lsan_default_suppressions (void);
 
 const char *
 __lsan_default_suppressions (void)
 {
   return "leak:gnutls_x509_crt_init\n";
 }
 
 
 #define MAX_SEGMENTS 48
 #define MAX_CONNECTIONS 3
 #define RESP_BUF_SIZE 16384
 #define GEN_BUF_SIZE 4096
 #define MAX_SNI_LEN 255
 #define FUZZ_PEM_BODY_MAX 1024
 
 /** Number of client priority strings offered to the input. */
 #define CLIENT_PRIO_COUNT 4
 
 /**
  * Upper bound on the number of client/server round trips spent on one
  * handshake.  A TLS 1.3 handshake over a socketpair needs a handful; the
  * cap only has to guarantee termination.
  */
 #define HANDSHAKE_ROUNDS 64
 
 
 /* ------------------------------------------------------------------ */
 /* Test credentials                                                    */
 /* ------------------------------------------------------------------ */
 
 /*
  * Taken verbatim from src/testcurl/https/tls_test_keys.h (the CA
  * certificate, the CA-signed server certificate and its key, and the
  * self-signed server certificate and its key), so that this harness
  * stays a single translation unit.  dh_params_pem is RFC 3526 group 14,
  * as emitted by "certtool --get-dh-params --sec-param medium".
  */
 
 static const char ca_cert_pem[] =
   "-----BEGIN CERTIFICATE-----\n"
   "MIIGITCCBAmgAwIBAgIBADANBgkqhkiG9w0BAQsFADCBgTELMAkGA1UEBhMCUlUx\n"
   "DzANBgNVBAgMBk1vc2NvdzEPMA0GA1UEBwwGTW9zY293MRswGQYDVQQKDBJ0ZXN0\n"
   "LWxpYm1pY3JvaHR0cGQxITAfBgkqhkiG9w0BCQEWEm5vYm9keUBleGFtcGxlLm9y\n"
   "ZzEQMA4GA1UEAwwHdGVzdC1DQTAgFw0yMTA0MDcxNzM2MThaGA8yMTIxMDMxNDE3\n"
   "MzYxOFowgYExCzAJBgNVBAYTAlJVMQ8wDQYDVQQIDAZNb3Njb3cxDzANBgNVBAcM\n"
   "Bk1vc2NvdzEbMBkGA1UECgwSdGVzdC1saWJtaWNyb2h0dHBkMSEwHwYJKoZIhvcN\n"
   "AQkBFhJub2JvZHlAZXhhbXBsZS5vcmcxEDAOBgNVBAMMB3Rlc3QtQ0EwggIiMA0G\n"
   "CSqGSIb3DQEBAQUAA4ICDwAwggIKAoICAQDdaWupA4qZjCBNkJoJOm5xnCaizl36\n"
   "ZLUwp4xBL/YfXPWE3LkmAREiVI/YnAb8l6G7CJnz8dTsOJWkNXG6T1KVP5/2RvBI\n"
   "IaaaufRIAl7hEnj1j9E2hQlV2fxF2ZNhz+nqi0LqKV4LJSpclkXADf2FA9HsVRP/\n"
   "B7zYh+DP0fSU8V6bsu8XCeRGshroAPrc8rH8lFEEXpNLNIqQr8yKx6SmdB6hfja6\n"
   "6SQ0++qBhl0aJtn4LHWZohgjBmkIaGFPYIJLgxQ/xyp2Grz2q7lGKJ+zBkBF8iOP\n"
   "t3x+F1hSCBnr/DGYWmjEm5tYm+7pyuriPddXdCc8+qa2LxMZo3EXxLo5YISpPCyw\n"
   "Z7V3YAOZTr3m1C24LiYvPehCq1CTIkhhmqtlVJXU7ISD48cx9y+5Pi34wtbTI/gN\n"
   "x4voyTLAfyavKMmIpxxIRsWldiF2n06HdvCRVdihDQUad10ygTmWf1J/s2ZETAtH\n"
   "QaSd7MD389t6nQFtTIXigsNKnnDPlrtxt7rOLvLQeR0K04Gzrf/scheOanRAfOXH\n"
   "KNBFU7YkDFG8rqizlC65rx9qeXFYXQcHZTuqxK7tgZnSgJat3E70VbTSCsEEG7eR\n"
   "bNX/fChUKAIIpWaiW6HDlKLl6m2y+BzM91umBsKOqTvntMVFBSF9pVYlXK854aIR\n"
   "q8A2Xujd012seQIDAQABo4GfMIGcMAsGA1UdDwQEAwICpDASBgNVHRMBAf8ECDAG\n"
   "AQH/AgEBMB0GA1UdDgQWBBRYdUPApWoxw4U13Rqsjf9AHdbpLDATBgNVHSUEDDAK\n"
   "BggrBgEFBQcDATAkBglghkgBhvhCAQ0EFxYVVGVzdCBsaWJtaWNyb2h0dHBkIENB\n"
   "MB8GA1UdIwQYMBaAFFh1Q8ClajHDhTXdGqyN/0Ad1uksMA0GCSqGSIb3DQEBCwUA\n"
   "A4ICAQBvrrcTKVeI1EYnXo4BQD4oCvf9z1fYQmL21EbHwgjg1nmaPkvStgWAc5p1\n"
   "kKwySrpEMKXfu68X76RccXZyWWIamEjz2OCWYZgjX6d6FpjhLphL8WxXDy5C9eay\n"
   "ixN7+URz2XQoi22wqR+tCPDhrIzcMPyMkx/6gRgcYeDnaFrkdSeSsKsID4plfcIj\n"
   "ISWJDvv+IAgrtsG1NVHnGwpAv0od3A8/4/fR6PPyewaU3aydvjZ7Au8O9DGDjlU9\n"
   "9HdlOkkY6GVJ1pfGZib7cV7lhy0D2kj1g9xZh97YjpoUfppPl9r+6A8gDm0hXlAD\n"
   "TlzNYlwTb681ZEoSd9PiLEY8HETssHlays2dYXdcNwAEp69iIHz8q1Q98Be9LScl\n"
   "WEzgaOT9U7lpIw/MWbELoMsC+Ecs1cVWBIuiIq8aSG2kRr1x3S8yVXbAohAXif2s\n"
   "E6puieM/VJ25iaNhkbLmDkk58QVVmn9NZNv6ETxuSQMp9e0EwbVlj68vzClQ91Y/\n"
   "nmAiGcLFUEwB9G0szv9+vR+oDW4IkvdFZSUbcICd2cnynnwAD395onqS4hEZO1xM\n"
   "Gy5ZldbTMTjgn7fChNopz15ChPBnwFIjhm+S0CyiLRQAowfknRVq2IBkj7/5kOWg\n"
   "4mcxcq76HoQWK/8X/8RFL1eFVAvY7TNHYJ0RS51DMuwCNQictA==\n"
   "-----END CERTIFICATE-----\n";
 
 
 static const char srv_signed_key_pem[] =
   "-----BEGIN PRIVATE KEY-----\n"
   "MIIEvgIBADANBgkqhkiG9w0BAQEFAASCBKgwggSkAgEAAoIBAQCff7amw9zNSE+h\n"
   "rOMhBrzbbsJluUP3gmd8nOKY5MUimoPkxmAXfp2L0il+MPZT/ZEmo11q0k6J2jfG\n"
   "UBQ+oZW9ahNZ9gCDjbYlBblo/mqTai+LdeLO3qk53d0zrZKXvCO6sA3uKpG2WR+g\n"
   "+sNKxfYpIHCpanqBU6O+degIV/+WKy3nQ2Fwp7K5HUNj1u0pg0QQ18yf68LTnKFU\n"
   "HFjZmmaaopWki5wKSBieHivzQy6w+04HSTogHHRK/y/UcoJNSG7xnHmoPPo1vLT8\n"
   "CMRIYnSSgU3wJ43XBJ80WxrC2dcoZjV2XZz+XdQwCD4ZrC1ihykcAmiQA+sauNm7\n"
   "dztOMkGzAgMBAAECggEAIbKDzlvXDG/YkxnJqrKXt+yAmak4mNQuNP+YSCEdHSBz\n"
   "+SOILa6MbnvqVETX5grOXdFp7SWdfjZiTj2g6VKOJkSA7iKxHRoVf2DkOTB3J8np\n"
   "XZd8YaRdMGKVV1O2guQ20Dxd1RGdU18k9YfFNsj4Jtw5sTFTzHr1P0n9ybV9xCXp\n"
   "znSxVfRg8U6TcMHoRDJR9EMKQMO4W3OQEmreEPoGt2/+kMuiHjclxLtbwDxKXTLP\n"
   "pD0gdg3ibvlufk/ccKl/yAglDmd0dfW22oS7NgvRKUve7tzDxY1Q6O5v8BCnLFSW\n"
   "D+z4hS1PzooYRXRkM0xYudvPkryPyu+1kEpw3fNsoQKBgQDRfXJo82XQvlX8WPdZ\n"
   "Ts3PfBKKMVu3Wf8J3SYpuvYT816qR3ot6e4Ivv5ZCQkdDwzzBKe2jAv6JddMJIhx\n"
   "pkGHc0KKOodd9HoBewOd8Td++hapJAGaGblhL5beIidLKjXDjLqtgoHRGlv5Cojo\n"
   "zHa7Viel1eOPPcBumhp83oJ+mQKBgQDC6PmdETZdrW3QPm7ZXxRzF1vvpC55wmPg\n"
   "pRfTRM059jzRzAk0QiBgVp3yk2a6Ob3mB2MLfQVDgzGf37h2oO07s5nspSFZTFnM\n"
   "KgSjFy0xVOAVDLe+0VpbmLp1YUTYvdCNowaoTE7++5rpePUDu3BjAifx07/yaSB+\n"
   "W+YPOfOuKwKBgQCGK6g5G5qcJSuBIaHZ6yTZvIdLRu2M8vDral5k3793a6m3uWvB\n"
   "OFAh/eF9ONJDcD5E7zhTLEMHhXDs7YEN+QODMwjs6yuDu27gv97DK5j1lEsrLUpx\n"
   "XgRjAE3KG2m7NF+WzO1K74khWZaKXHrvTvTEaxudlO3X8h7rN3u7ee9uEQKBgQC2\n"
   "wI1zeTUZhsiFTlTPWfgppchdHPs6zUqq0wFQ5Zzr8Pa72+zxY+NJkU2NqinTCNsG\n"
   "ePykQ/gQgk2gUrt595AYv2De40IuoYk9BlTMuql0LNniwsbykwd/BOgnsSlFdEy8\n"
   "0RQn70zOhgmNSg2qDzDklJvxghLi7zE5aV9//V1/ewKBgFRHHZN1a8q/v8AAOeoB\n"
   "ROuXfgDDpxNNUKbzLL5MO5odgZGi61PBZlxffrSOqyZoJkzawXycNtoBP47tcVzT\n"
   "QPq5ZOB3kjHTcN7dRLmPWjji9h4O3eHCX67XaPVMSWiMuNtOZIg2an06+jxGFhLE\n"
   "qdJNJ1DkyUc9dN2cliX4R+rG\n"
   "-----END PRIVATE KEY-----\n";
 
 
 static const char srv_signed_cert_pem[] =
   "-----BEGIN CERTIFICATE-----\n"
   "MIIFSzCCAzOgAwIBAgIBBDANBgkqhkiG9w0BAQsFADCBgTELMAkGA1UEBhMCUlUx\n"
   "DzANBgNVBAgMBk1vc2NvdzEPMA0GA1UEBwwGTW9zY293MRswGQYDVQQKDBJ0ZXN0\n"
   "LWxpYm1pY3JvaHR0cGQxITAfBgkqhkiG9w0BCQEWEm5vYm9keUBleGFtcGxlLm9y\n"
   "ZzEQMA4GA1UEAwwHdGVzdC1DQTAgFw0yMjA0MjAxODQzMDJaGA8yMTIyMDMyNjE4\n"
   "NDMwMlowZTELMAkGA1UEBhMCUlUxDzANBgNVBAgMBk1vc2NvdzEPMA0GA1UEBwwG\n"
   "TW9zY293MRswGQYDVQQKDBJ0ZXN0LWxpYm1pY3JvaHR0cGQxFzAVBgNVBAMMDnRl\n"
   "c3QtbWhkc2VydmVyMIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAn3+2\n"
   "psPczUhPoazjIQa8227CZblD94JnfJzimOTFIpqD5MZgF36di9IpfjD2U/2RJqNd\n"
   "atJOido3xlAUPqGVvWoTWfYAg422JQW5aP5qk2ovi3Xizt6pOd3dM62Sl7wjurAN\n"
   "7iqRtlkfoPrDSsX2KSBwqWp6gVOjvnXoCFf/list50NhcKeyuR1DY9btKYNEENfM\n"
   "n+vC05yhVBxY2ZpmmqKVpIucCkgYnh4r80MusPtOB0k6IBx0Sv8v1HKCTUhu8Zx5\n"
   "qDz6Nby0/AjESGJ0koFN8CeN1wSfNFsawtnXKGY1dl2c/l3UMAg+GawtYocpHAJo\n"
   "kAPrGrjZu3c7TjJBswIDAQABo4HmMIHjMAsGA1UdDwQEAwIFoDAMBgNVHRMBAf8E\n"
   "AjAAMBYGA1UdJQEB/wQMMAoGCCsGAQUFBwMBMDEGA1UdEQQqMCiCDnRlc3QtbWhk\n"
   "c2VydmVyhwR/AAABhxAAAAAAAAAAAAAAAAAAAAABMB0GA1UdDgQWBBQ57Z06WJae\n"
   "8fJIHId4QGx/HsRgDDAoBglghkgBhvhCAQ0EGxYZVGVzdCBsaWJtaWNyb2h0dHBk\n"
   "IHNlcnZlcjARBglghkgBhvhCAQEEBAMCBkAwHwYDVR0jBBgwFoAUWHVDwKVqMcOF\n"
   "Nd0arI3/QB3W6SwwDQYJKoZIhvcNAQELBQADggIBAI7Lggm/XzpugV93H5+KV48x\n"
   "X+Ct8unNmPCSzCaI5hAHGeBBJpvD0KME5oiJ5p2wfCtK5Dt9zzf0S0xYdRKqU8+N\n"
   "aKIvPoU1hFixXLwTte1qOp6TviGvA9Xn2Fc4n36dLt6e9aiqDnqPbJgBwcVO82ll\n"
   "HJxVr3WbrAcQTB3irFUMqgAke/Cva9Bw79VZgX4ghb5EnejDzuyup4pHGzV10Myv\n"
   "hdg+VWZbAxpCe0S4eKmstZC7mWsFCLeoRTf/9Pk1kQ6+azbTuV/9QOBNfFi8QNyb\n"
   "18jUjmm8sc2HKo8miCGqb2sFqaGD918hfkWmR+fFkzQ3DZQrT+eYbKq2un3k0pMy\n"
   "UySy8SRn1eadfab+GwBVb68I9TrPRMrJsIzysNXMX4iKYl2fFE/RSNnaHtPw0C8y\n"
   "B7memyxPRl+H2xg6UjpoKYh3+8e44/XKm0rNIzXjrwA8f8gnw2TbqmMDkj1YqGnC\n"
   "SCj5A27zUzaf2pT/YsnQXIWOJjVvbEI+YKj34wKWyTrXA093y8YI8T3mal7Kr9YM\n"
   "WiIyPts0/aVeziM0Gunglz+8Rj1VesL52FTurobqusPgM/AME82+qb/qnxuPaCKj\n"
   "OT1qAbIblaRuWqCsid8BzP7ZQiAnAWgMRSUg1gzDwSwRhrYQRRWAyn/Qipzec+27\n"
   "/w0gW9EVWzFhsFeGEssi\n"
   "-----END CERTIFICATE-----\n";
 
 
 static const char srv_self_signed_cert_pem[] =
   "-----BEGIN CERTIFICATE-----\n"
   "MIIDJzCCAg+gAwIBAgIUOKf6e6Heee2XA+yF5St3t+fVM40wDQYJKoZIhvcNAQEF\n"
   "BQAwFDESMBAGA1UEAwwJbG9jYWxob3N0MCAXDTIyMTAxMDA4MzQ0N1oYDzIxMjIw\n"
   "OTE2MDgzNDQ3WjAUMRIwEAYDVQQDDAlsb2NhbGhvc3QwggEiMA0GCSqGSIb3DQEB\n"
   "AQUAA4IBDwAwggEKAoIBAQClivgF8Xq0ekQli++0l7Q5JFwJCuLf04Cb1UKIS80U\n"
   "CfphFd1ILJepNw4bWR3OV1sRI1vFiw6LnCz53vOwVNyiZ+sMGi4bDX4AV9Xd+F83\n"
   "xhG8AjOmKTayW0TxSIvt47Qd5S/4fgraxMtvqrRRBen30iKOwX7uNF/4dYb9vdin\n"
   "OldV/e8uzbqSurMGkNDznOeSaNBmdO/7x0VMFZM2hwmHyiiw75/j4BhUlLCcMEvK\n"
   "oN+YHNCNcTt3Qm1vVuiGXmh9QreOV09Gc1SzAltxF2gmI0jzw8r/duz18QXMNsMw\n"
   "El/Ah4+02gR70L7qlgttN1NPU3RJpK/L34J7yg649wHTAgMBAAGjbzBtMB0GA1Ud\n"
   "DgQWBBROVferD+YYcV1YEnFgC0jYm5X9BjAfBgNVHSMEGDAWgBROVferD+YYcV1Y\n"
   "EnFgC0jYm5X9BjAPBgNVHRMBAf8EBTADAQH/MBoGA1UdEQQTMBGCCWxvY2FsaG9z\n"
   "dIcEfwAAATANBgkqhkiG9w0BAQUFAAOCAQEAoRbozsm5xXdNX3VO++s2LMzw5KM9\n"
   "RpIInHNkMJbnyLJFKJ8DF7nTxSGCA38YMkX3tphPNKZXbg+V64Dqr/XpzOVyiinU\n"
   "7hIwyUdSSKKyErZxIWR97lY6Q3SOyPAg8ZElbtvSsSzmd772VE23VTXGDi7AW0PQ\n"
   "hag9N2EEnHURMvID15O+UXyFpDdyUyQIbx3HuswsGDH9xBTm4irLyrZwO0KwKg5a\n"
   "JBeUiPs0SYRRfn9/MoE6VwAnmOCg3LLR6ZPU3hQtTPLHj2Op1g5fey3X3X6lC+JC\n"
   "K6dNZc1zBFPz8KANGUsFYbmoP2bvAAA+6KwCnZZEflUgE7/HFEmQhVOezw==\n"
   "-----END CERTIFICATE-----\n";
 
 
 static const char srv_self_signed_key_pem[] =
   "-----BEGIN PRIVATE KEY-----\n"
   "MIIEvQIBADANBgkqhkiG9w0BAQEFAASCBKcwggSjAgEAAoIBAQClivgF8Xq0ekQl\n"
   "i++0l7Q5JFwJCuLf04Cb1UKIS80UCfphFd1ILJepNw4bWR3OV1sRI1vFiw6LnCz5\n"
   "3vOwVNyiZ+sMGi4bDX4AV9Xd+F83xhG8AjOmKTayW0TxSIvt47Qd5S/4fgraxMtv\n"
   "qrRRBen30iKOwX7uNF/4dYb9vdinOldV/e8uzbqSurMGkNDznOeSaNBmdO/7x0VM\n"
   "FZM2hwmHyiiw75/j4BhUlLCcMEvKoN+YHNCNcTt3Qm1vVuiGXmh9QreOV09Gc1Sz\n"
   "AltxF2gmI0jzw8r/duz18QXMNsMwEl/Ah4+02gR70L7qlgttN1NPU3RJpK/L34J7\n"
   "yg649wHTAgMBAAECggEAERbbCtYGakoy7cNX8Ac3Kiz4OVC/4gZWAQBPeX2FwrtS\n"
   "9yHIMbK0x1mxIZ6eBpabBpZlW2vDCSOKuxLKiloAWt2qdJnhR5apesSWhe8leT7/\n"
   "xq5dgZpAlMH6SIRKObknd2yY+qicW0A0licDrVeUcypkueL8xP9wJtiPInOuQXkI\n"
   "QROhB13eStRuRKYwOn5gtwAHJ+J1DFKKiqpBOkrSYf4625StGegJO9+bjK0ei+0W\n"
   "tp6unpiwA/lXTgz6Xim1Z3fzWs4XjFgVKzK5s/6yBJjr8spHX6lv7QsahP4w6HZ/\n"
   "VcRxP6cJNd/otiTEtJXpbxiiyccwXm/AOcOn22P1cQKBgQDAnY/0G/ap/G98pneE\n"
   "suzNXhWOQ8JoL8d66Io8vwTvfiJggfgUcwblI7pPCrSlaZMR7/q6JImE53lZtPk8\n"
   "eI3c9lN0ocr8E7+huDpYdk7cMYj9SuxySsXoMLiMqzHFi+NcIhKMF56kk6a5CFCt\n"
   "yP1Ofy76LVweGE3XvTwpwE7wUQKBgQDcBLyH1cC71s0I0Gz28AyELV9hPhasjAKO\n"
   "12CVbeBVTPd+28uk/3o80wSrTksc6H5ehAA2aTvrb4OhwssWNL+D0fS8YK2cJ3V0\n"
   "FJxGAM266+vC4d/8jRTHJnc+6PP3ix5t6vAt+K2Y0fePtefLqf4ebgXx/ODAj3J2\n"
   "aZKBldjK4wKBgGIRFpTLk/eR/dUyEBHw4x3gdAsdtqJDCUYrlQ4+ly20Q55tLbiD\n"
   "pBQP77CEm9rH+MgeLcKODbIsBB3HRUojet7wTydHpMhY6a1V1ebqPVZgpgWIGwBJ\n"
   "z59bBusf0lRo15Y2Bslq0SurvSvh7um8NjO8D1fytj7gUumvgC0lq0sxAoGBAI1+\n"
   "kkx9IBTtIDER8XGhkTsT/uoHxwcyh5abVmbjIclZ1TUFX2L+Vft17ePJVy8BKfvY\n"
   "wlY7uShBMBNAteDTDXNV/CGFv0DUc4myk4nFjIkwng9XufeuN3WX/Eo+AF/rXSdt\n"
   "VwcJjYLhTWdjoe1tppqlQTeN3HCaEA+s92ZVGvXnAoGAMCXGS6WZl1e5wsHRq0Yy\n"
   "8Ef2Wrk620bBjKHolkTfvgfhlvxeZM1sv1ioZGsOeQ0z7O7wdJhvL0M/WAG+3yQj\n"
   "HSXp81T1vOICPwNYZf8xcvbLKmvj7rHFt6ZAZF2o4EK8ReZTRyA3DUpBCDY+s3FN\n"
   "GmBv0D7N3QP0CT3SzfQrPkc=\n"
   "-----END PRIVATE KEY-----\n";
 
 
 static const char dh_params_pem[] =
   "-----BEGIN DH PARAMETERS-----\n"
   "MIIBDAKCAQEA//////////+t+FRYortKmq/cViAnPTzx2LnFg84tNpWp4TZBFGQz\n"
   "+8yTnc4kmz75fS/jY2MMddj2gbICrsRhetPfHtXV/WVhJDP1H18GbtCFY2VVPe0a\n"
   "87VXE15/V8k1mE8McODmi3fipona8+/och3xWKE2rec1MKzKT0g6eXq8CrGCsyT7\n"
   "YdEIqUuyyOP7uWrat2DX9GgdT0Kj3jlN9K5W7edjcrsZCwenyO4KbXCeAvzhzffi\n"
   "7MA0BM0oNC9hkXL+nOmFg/+OTxIy7vKBg8P+OxtMb61zO7X8vC7CIAXFjvGDfRaD\n"
   "ssbzSibBsu/6iGtCOGEoXJf//////////wIBAgICAQA=\n"
   "-----END DH PARAMETERS-----\n";
 
 /** A PEM blob whose armour is fine but whose payload is not base64. */
 static const char garbage_cert_pem[] =
   "-----BEGIN CERTIFICATE-----\n"
   "this is not base64 at all, not even close !!!! ????\n"
   "-----END CERTIFICATE-----\n";
 
 static const char garbage_key_pem[] =
   "-----BEGIN PRIVATE KEY-----\n"
   "@@@@ neither is this @@@@\n"
   "-----END PRIVATE KEY-----\n";
 
 /** Correct base64, but the armour never ends. */
 static const char truncated_cert_pem[] =
   "-----BEGIN CERTIFICATE-----\n"
   "MIIFSzCCAzOgAwIBAgIBBDANBgkqhkiG9w0BAQsFADCBgTELMAkGA1UEBhMCUlUx\n"
   "DzANBgNVBAgMBk1vc2NvdzEPMA0GA1UEBwwGTW9zY293MRswGQYDVQQKDBJ0ZXN0\n";
 
 static const char truncated_key_pem[] =
   "-----BEGIN PRIVATE KEY-----\n"
   "MIIEvgIBADANBgkqhkiG9w0BAQEFAASCBKgwggSkAgEAAoIBAQCff7amw9zNSE+h\n";
 
 /** Base64 of a certificate, but with no PEM armour at all. */
 static const char no_armour_pem[] =
   "MIIFSzCCAzOgAwIBAgIBBDANBgkqhkiG9w0BAQsFADCBgTELMAkGA1UEBhMCUlUx\n"
   "DzANBgNVBAgMBk1vc2NvdzEPMA0GA1UEBwwGTW9zY293MRswGQYDVQQKDBJ0ZXN0\n";
 
 static const char garbage_dh_pem[] =
   "-----BEGIN DH PARAMETERS-----\n"
   "not-dh-parameters\n"
   "-----END DH PARAMETERS-----\n";
 
 /**
  * PEM blobs assembled from the fuzzer's own bytes, see cred_tbl entries
  * 12 and 13.  Static so that the pointer handed to MHD stays valid for
  * the whole lifetime of the daemon.
  */
 static char fuzz_cert_pem[FUZZ_PEM_BODY_MAX + 128];
 static char fuzz_key_pem[FUZZ_PEM_BODY_MAX + 128];
 
 
 /**
  * A certificate/key pair for #MHD_OPTION_HTTPS_MEM_CERT and
  * #MHD_OPTION_HTTPS_MEM_KEY.  A NULL member means "do not pass the
  * option at all", which is a configuration MHD has to reject cleanly.
  */
 struct cred_pair
 {
   const char *cert;
   const char *key;
 };
 
 static const struct cred_pair cred_tbl[] = {
   { srv_signed_cert_pem, srv_signed_key_pem },        /*  0 valid, CA signed */
   { srv_self_signed_cert_pem, srv_self_signed_key_pem }, /* 1 valid, self signed */
   { srv_signed_cert_pem, srv_self_signed_key_pem },   /*  2 key does not match */
   { srv_self_signed_cert_pem, srv_signed_key_pem },   /*  3 key does not match */
   { srv_signed_cert_pem, NULL },                      /*  4 certificate only */
   { NULL, srv_signed_key_pem },                       /*  5 key only */
   { NULL, NULL },                                     /*  6 neither */
   { "", "" },                                         /*  7 empty strings */
   { truncated_cert_pem, srv_signed_key_pem },         /*  8 truncated armour */
   { srv_signed_cert_pem, truncated_key_pem },         /*  9 truncated armour */
   { garbage_cert_pem, garbage_key_pem },              /* 10 armour, no base64 */
   { no_armour_pem, srv_signed_key_pem },              /* 11 base64, no armour */
   { fuzz_cert_pem, srv_signed_key_pem },              /* 12 PEM from the input */
   { srv_signed_cert_pem, fuzz_key_pem },              /* 13 PEM from the input */
   { fuzz_cert_pem, fuzz_key_pem },                    /* 14 PEM from the input */
   { srv_signed_cert_pem, srv_signed_key_pem }         /* 15 valid (bias) */
 };
 
 #define CRED_COUNT (sizeof (cred_tbl) / sizeof (cred_tbl[0]))
 
 /**
  * Priority strings.  The first entries are the ones a real server would
  * use, the rest are what MHD has to reject without falling over.  MHD
  * hands these to gnutls_priority_init() (or appends them to its own
  * base string) and fails daemon startup if GnuTLS does not like them.
  */
 static const char *const prio_tbl[] = {
   "NORMAL",
   "NORMAL:-VERS-ALL:+VERS-TLS1.3",
   "NORMAL:-VERS-ALL:+VERS-TLS1.2",
   "SECURE128",
   "PERFORMANCE",
   "@LIBMICROHTTPD",
   "@SYSTEM",
   "NONE",
   "",
   "BOGUS-PRIORITY-STRING",
   "NORMAL:!!!",
   "NORMAL:-VERS-ALL",
   "NORMAL:+ANON-ECDH",
   "NORMAL:%SERVER_PRECEDENCE",
   "SECURE256:-CIPHER-ALL",
   ":::::"
 };
 
 #define PRIO_COUNT (sizeof (prio_tbl) / sizeof (prio_tbl[0]))
 
 /** Priority strings offered to the *client* side. */
 static const char *const client_prio_tbl[CLIENT_PRIO_COUNT] = {
   "NORMAL",
   "NORMAL:-VERS-ALL:+VERS-TLS1.3",
   "NORMAL:-VERS-ALL:+VERS-TLS1.2",
   "PERFORMANCE"
 };
 
 /**
  * Credential types.  Only GNUTLS_CRD_CERTIFICATE and GNUTLS_CRD_PSK are
  * accepted by MHD_TLS_init(); everything else must make daemon startup
  * fail rather than reach the MHD_PANIC() in new_connection_prepare_().
  */
 static const int cred_type_tbl[] = {
   (int) GNUTLS_CRD_CERTIFICATE,
   (int) GNUTLS_CRD_PSK,
   (int) GNUTLS_CRD_ANON,
   (int) GNUTLS_CRD_SRP,
   (int) GNUTLS_CRD_IA,
   (int) GNUTLS_CRD_CERTIFICATE,
   99,
   -1
 };
 
 #define CRED_TYPE_COUNT (sizeof (cred_type_tbl) / sizeof (cred_type_tbl[0]))
 
 static const size_t mem_limit_tbl[] = {
   0 /* MHD default */, 256, 512, 1024, 1400, 1500, 2048, 4096, 8192, 32768,
   0, 1024, 2048, 4096, 16384, 0
 };
 
 #define MEM_LIMIT_COUNT (sizeof (mem_limit_tbl) / sizeof (mem_limit_tbl[0]))
 
 static const char https_key_password[] = "not-the-password";
 
 
 /* ------------------------------------------------------------------ */
 /* Per-iteration configuration                                         */
 /* ------------------------------------------------------------------ */
 
 /** Behaviour of the SNI callback, selected by bits 3-5 of byte 3. */
 enum sni_behaviour
 {
   SNI_ALWAYS_OK = 0,      /**< always answer with the signed pair */
   SNI_FAIL,               /**< always answer -1 */
   SNI_EMPTY,              /**< answer 0 with an empty certificate list */
   SNI_BY_NAME,            /**< look the server name up, -1 if unknown */
   SNI_MISMATCH,           /**< answer with a key that is not the cert's */
   SNI_NO_KEY,             /**< answer 0, certificate but no key */
   SNI_SELF_SIGNED,        /**< always answer with the self-signed pair */
   SNI_BEHAVIOUR_COUNT
 };
 
 /** Client behaviour, selected by bits 0-1 of byte 4. */
 enum client_mode
 {
   CLIENT_RAW = 0,         /**< raw bytes straight at the TLS socket */
   CLIENT_TLS,             /**< a real GnuTLS client */
   CLIENT_TLS_ABANDON,     /**< a real client that stops mid-handshake */
   CLIENT_RECORDS          /**< raw bytes shaped like TLS records */
 };
 
 struct fuzz_cfg
 {
   /* ---- daemon ---- */
   const char *cert;
   const char *key;
   int use_tls;                 /**< set MHD_USE_TLS at all */
   int use_trust;
   int trust_garbage;
   int use_dhparams;
   int dh_garbage;
   int use_sni;
   int use_prio;
   int prio_append;
   unsigned int prio_idx;
   int use_cred_type;
   unsigned int cred_type_idx;
   int no_alpn;
   int key_password;
   int allow_upgrade;
   size_t mem_limit;
   unsigned int loop_mode;
 
   /* ---- SNI callback ---- */
   enum sni_behaviour sni_mode;
 
   /* ---- client ---- */
   enum client_mode mode;
   int client_sni;
   int client_cert;
   unsigned int client_prio_idx;
   int client_bye;
   int client_shut_wr;
   unsigned int hs_budget;      /**< handshake rounds in CLIENT_TLS_ABANDON */
   unsigned int extra_pump;
 
   /* ---- handler ---- */
   unsigned int resp_kind;
   int conn_info;
   int daemon_info;
   int conn_option;
   int error_reply;
   int resp_header;
   int quiesce;
 };
 
 static struct fuzz_cfg cfg;
 
 /**
  * Server names the client can present.  Which one is used comes from
  * byte 9 of the input; an op 1 segment overrides it.  MHD itself never
  * looks at the name -- GnuTLS parses the extension and the application
  * callback reads it back -- so a fixed table costs no MHD coverage.
  */
 static const char *const sni_name_tbl[] = {
   "test-mhdserver",
   "localhost",
   "mhdhost1",
   "nobody.example.org",
   "",
   "example.org",
   "TEST-MHDSERVER",
   "a.very.long.name.that.nobody.has.a.certificate.for.example.org"
 };
 
 #define SNI_NAME_COUNT (sizeof (sni_name_tbl) / sizeof (sni_name_tbl[0]))
 
 /** Server name the next client connection presents. */
 static char sni_name[MAX_SNI_LEN + 1];
 static size_t sni_name_len;
 
 /** Bytes received from the daemon during the current iteration. */
 static char resp_buf[RESP_BUF_SIZE];
 static size_t resp_len;
 
 /** Statistics, printed at exit with --verbose. */
 static unsigned long stat_daemons;
 static unsigned long stat_daemons_failed;
 static unsigned long stat_connections;
 static unsigned long stat_handshakes_ok;
 static unsigned long stat_handshakes_failed;
 static unsigned long stat_handler_calls;
 static unsigned long stat_sni_calls;
 static int stats_registered;
 
 
 static void
 print_stats (void)
 {
   if (! fuzz_verbose)
     return;
   fprintf (stderr,
            "%s: daemons=%lu (start failed=%lu) connections=%lu "
            "handshakes ok=%lu failed=%lu handler calls=%lu SNI calls=%lu\n",
            FUZZ_HARNESS_NAME,
            stat_daemons, stat_daemons_failed, stat_connections,
            stat_handshakes_ok, stat_handshakes_failed, stat_handler_calls,
            stat_sni_calls);
 }
 
 
 /* ------------------------------------------------------------------ */
 /* The SNI (certificate retrieve) callback                             */
 /* ------------------------------------------------------------------ */
 
 /**
  * Certificates for the SNI callback, parsed once and then kept in these
  * statics for the whole life of the process: they are configuration, not
  * per-iteration state, and re-parsing them on every execution would cost
  * more than everything else the harness does.  They are reachable from
  * globals, so LeakSanitizer does not count them.
  */
 struct sni_host
 {
   const char *name;
   const char *cert_pem;
   const char *key_pem;
   gnutls_pcert_st pcrt;
   gnutls_privkey_t key;
   int loaded;
 };
 
 static struct sni_host sni_hosts[2] = {
   { "test-mhdserver", NULL, NULL, { 0, { NULL, 0 }, 0 }, NULL, 0 },
   { "localhost", NULL, NULL, { 0, { NULL, 0 }, 0 }, NULL, 0 }
 };
 
 static int sni_hosts_ready;
 
 
 /**
  * @return 0 if the certificates are usable
  */
 static int
 sni_hosts_init (void)
 {
   unsigned int i;
 
   if (0 != sni_hosts_ready)
     return (1 == sni_hosts_ready) ? 0 : -1;
   sni_hosts[0].cert_pem = srv_signed_cert_pem;
   sni_hosts[0].key_pem = srv_signed_key_pem;
   sni_hosts[1].cert_pem = srv_self_signed_cert_pem;
   sni_hosts[1].key_pem = srv_self_signed_key_pem;
   sni_hosts_ready = 1;
   for (i = 0; i < sizeof (sni_hosts) / sizeof (sni_hosts[0]); i++)
   {
     struct sni_host *h = &sni_hosts[i];
     gnutls_datum_t d;
 
     d.data = (unsigned char *) (intptr_t) h->cert_pem;
     d.size = (unsigned int) strlen (h->cert_pem);
     if (GNUTLS_E_SUCCESS !=
         gnutls_pcert_import_x509_raw (&h->pcrt, &d, GNUTLS_X509_FMT_PEM, 0))
     {
       sni_hosts_ready = -1;
       continue;
     }
     if (GNUTLS_E_SUCCESS != gnutls_privkey_init (&h->key))
     {
       gnutls_pcert_deinit (&h->pcrt);
       sni_hosts_ready = -1;
       continue;
     }
     d.data = (unsigned char *) (intptr_t) h->key_pem;
     d.size = (unsigned int) strlen (h->key_pem);
     if (GNUTLS_E_SUCCESS !=
         gnutls_privkey_import_x509_raw (h->key, &d, GNUTLS_X509_FMT_PEM,
                                         NULL, 0))
     {
       gnutls_privkey_deinit (h->key);
       h->key = NULL;
       gnutls_pcert_deinit (&h->pcrt);
       sni_hosts_ready = -1;
       continue;
     }
     h->loaded = 1;
   }
   return (1 == sni_hosts_ready) ? 0 : -1;
 }
 
 
 /**
  * #MHD_OPTION_HTTPS_CERT_CALLBACK.  Deliberately badly behaved for most
  * of the settings of @e cfg.sni_mode: an application callback that fails
  * or answers with nothing is exactly the case MHD has to survive.
  */
 static int
 sni_callback (gnutls_session_t session,
               const gnutls_datum_t *req_ca_dn,
               int nreqs,
               const gnutls_pk_algorithm_t *pk_algos,
               int pk_algos_length,
               gnutls_pcert_st **pcert,
               unsigned int *pcert_length,
               gnutls_privkey_t *pkey)
 {
   char name[MAX_SNI_LEN + 1];
   size_t name_len = sizeof (name);
   unsigned int type;
   unsigned int i;
 
   (void) req_ca_dn;
   (void) nreqs;
   (void) pk_algos;
   (void) pk_algos_length;
   stat_sni_calls++;
   if (! sni_hosts[0].loaded)
     return -1;
   switch (cfg.sni_mode)
   {
   case SNI_FAIL:
     return -1;
   case SNI_EMPTY:
     *pcert = NULL;
     *pcert_length = 0;
     *pkey = NULL;
     return 0;
   case SNI_NO_KEY:
     *pcert = &sni_hosts[0].pcrt;
     *pcert_length = 1;
     *pkey = NULL;
     return 0;
   case SNI_MISMATCH:
     if (! sni_hosts[1].loaded)
       return -1;
     *pcert = &sni_hosts[0].pcrt;
     *pcert_length = 1;
     *pkey = sni_hosts[1].key;
     return 0;
   case SNI_SELF_SIGNED:
     if (! sni_hosts[1].loaded)
       return -1;
     *pcert = &sni_hosts[1].pcrt;
     *pcert_length = 1;
     *pkey = sni_hosts[1].key;
     return 0;
   case SNI_BY_NAME:
     if (GNUTLS_E_SUCCESS !=
         gnutls_server_name_get (session, name, &name_len, &type, 0))
       return -1;
     for (i = 0; i < sizeof (sni_hosts) / sizeof (sni_hosts[0]); i++)
       if ( (sni_hosts[i].loaded) &&
            (0 == strncmp (name, sni_hosts[i].name, name_len)) )
       {
         *pcert = &sni_hosts[i].pcrt;
         *pcert_length = 1;
         *pkey = sni_hosts[i].key;
         return 0;
       }
     return -1;
   case SNI_ALWAYS_OK:
   case SNI_BEHAVIOUR_COUNT:
   default:
     break;
   }
   *pcert = &sni_hosts[0].pcrt;
   *pcert_length = 1;
   *pkey = sni_hosts[0].key;
   return 0;
 }
 
 
 /* ------------------------------------------------------------------ */
 /* The application                                                     */
 /* ------------------------------------------------------------------ */
 
 static const char resp_body[] = "hello world over TLS";
 
 
 static enum MHD_Result
 ahc (void *cls,
      struct MHD_Connection *connection,
      const char *url,
      const char *method,
      const char *version,
      const char *upload_data,
      size_t *upload_data_size,
      void **req_cls)
 {
   static int marker;
   struct MHD_Response *r;
   enum MHD_Result ret;
 
   (void) cls;
   (void) url;
   (void) method;
   (void) version;
   (void) upload_data;
   stat_handler_calls++;
   if (NULL == *req_cls)
   {
     /* first call: MHD only wants to know that we are interested */
     *req_cls = &marker;
     return MHD_YES;
   }
   if (0 != *upload_data_size)
   {
     /* discard the request body */
     *upload_data_size = 0;
     return MHD_YES;
   }
   if (cfg.conn_info)
   {
     /* The TLS-specific members of MHD_ConnectionInfo; all three answer
        NULL on a connection without a session, which is a state this
        harness can produce. */
     (void) MHD_get_connection_info (connection,
                                     MHD_CONNECTION_INFO_CIPHER_ALGO);
     (void) MHD_get_connection_info (connection,
                                     MHD_CONNECTION_INFO_PROTOCOL);
     (void) MHD_get_connection_info (connection,
                                     MHD_CONNECTION_INFO_GNUTLS_SESSION);
     (void) MHD_get_connection_info (connection,
                                     MHD_CONNECTION_INFO_GNUTLS_CLIENT_CERT);
     (void) MHD_get_connection_info (connection,
                                     MHD_CONNECTION_INFO_CLIENT_ADDRESS);
     (void) MHD_get_connection_info (connection,
                                     MHD_CONNECTION_INFO_CONNECTION_FD);
   }
   if (cfg.conn_option)
     (void) MHD_set_connection_option (connection,
                                       MHD_CONNECTION_OPTION_TIMEOUT,
                                       (unsigned int) 0);
   switch (cfg.resp_kind)
   {
   case 1:
     r = MHD_create_response_from_buffer_copy (sizeof (resp_body) - 1,
                                               resp_body);
     break;
   case 2:
     r = MHD_create_response_empty (MHD_RF_NONE);
     break;
   case 3:
     r = MHD_create_response_from_buffer_static (0, "");
     break;
   case 0:
   default:
     r = MHD_create_response_from_buffer_static (sizeof (resp_body) - 1,
                                                 resp_body);
     break;
   }
   if (NULL == r)
     return MHD_NO;
   if (cfg.resp_header)
     (void) MHD_add_response_header (r, "X-Fuzz", "tls");
   ret = MHD_queue_response (connection,
                             cfg.error_reply
                             ? MHD_HTTP_FORBIDDEN
                             : MHD_HTTP_OK,
                             r);
   MHD_destroy_response (r);
   return ret;
 }
 
 
 static void
 panic_cb (void *cls,
           const char *file,
           unsigned int line,
           const char *reason)
 {
   char msg[512];
 
   (void) cls;
   (void) snprintf (msg, sizeof (msg),
                    "MHD_PANIC() reached at %s:%u: %s",
                    (NULL != file) ? file : "?",
                    line,
                    (NULL != reason) ? reason : "?");
   fuzz_report_finding (msg);
 }
 
 
 /* ------------------------------------------------------------------ */
 /* Driving the daemon                                                  */
 /* ------------------------------------------------------------------ */
 
 /**
  * Advance the daemon by one cycle, through the event-loop API selected
  * by byte 5 of the input.  The select() timeout is always zero: the
  * harness is single threaded, whatever the daemon is waiting for has
  * already been written into the socketpair, and blocking would only burn
  * wall clock.
  */
 static void
 run_once (struct MHD_Daemon *d)
 {
   fd_set rs;
   fd_set ws;
   fd_set es;
   MHD_socket max_fd = MHD_INVALID_SOCKET;
   struct timeval tv;
 
   if (0 == cfg.loop_mode)
   {
     (void) MHD_run (d);
     return;
   }
   FD_ZERO (&rs);
   FD_ZERO (&ws);
   FD_ZERO (&es);
   if (1 == cfg.loop_mode)
   {
     /* Parenthesised so that the real v1 function is called: microhttpd.h
        also defines MHD_get_fdset as a macro forwarding to
        MHD_get_fdset2.  Same trick for MHD_run_from_select below. */
     if (MHD_YES != (MHD_get_fdset) (d, &rs, &ws, &es, &max_fd))
     {
       (void) MHD_run (d);
       return;
     }
   }
   else
   {
     if (MHD_YES != MHD_get_fdset2 (d, &rs, &ws, &es, &max_fd,
                                    (unsigned int) FD_SETSIZE))
     {
       (void) MHD_run (d);
       return;
     }
   }
   tv.tv_sec = 0;
   tv.tv_usec = 0;
   if (MHD_INVALID_SOCKET != max_fd)
     (void) select ((int) max_fd + 1, &rs, &ws, &es, &tv);
   if (1 == cfg.loop_mode)
     (void) (MHD_run_from_select) (d, &rs, &ws, &es);
   else
     (void) MHD_run_from_select2 (d, &rs, &ws, &es, (unsigned int) FD_SETSIZE);
 }
 
 
 /* ------------------------------------------------------------------ */
 /* The in-process TLS client                                           */
 /* ------------------------------------------------------------------ */
 
 struct tls_client
 {
   gnutls_session_t sess;                    /**< NULL in the raw modes */
   gnutls_certificate_credentials_t cred;
   int fd;                                   /**< our end of the socketpair */
   int hs_done;
   int dead;
 };
 
 
 static void
 pump (struct MHD_Daemon *d,
       unsigned int rounds)
 {
   unsigned int i;
 
   for (i = 0; i < rounds; i++)
     run_once (d);
 }
 
 
 /**
  * Read whatever the daemon has produced so far.  In the raw modes this
  * is a plain recv(); with a real client it goes through GnuTLS, which is
  * what actually drives MHD's send path and its TLS shutdown handling.
  */
 static void
 tc_drain (struct tls_client *tc)
 {
   unsigned int i;
   char tmp[4096];
 
   if (0 > tc->fd)
     return;
   if (NULL == tc->sess)
   {
     for (;;)
     {
       ssize_t n = recv (tc->fd, tmp, sizeof (tmp), MSG_DONTWAIT);
 
       if (0 >= n)
         break;
       if (resp_len + (size_t) n < RESP_BUF_SIZE)
       {
         memcpy (resp_buf + resp_len, tmp, (size_t) n);
         resp_len += (size_t) n;
       }
     }
     return;
   }
   if (tc->dead || (! tc->hs_done))
     return;
   for (i = 0; i < 8; i++)
   {
     ssize_t n = gnutls_record_recv (tc->sess, tmp, sizeof (tmp));
 
     if (0 < n)
     {
       if (resp_len + (size_t) n < RESP_BUF_SIZE)
       {
         memcpy (resp_buf + resp_len, tmp, (size_t) n);
         resp_len += (size_t) n;
       }
       continue;
     }
     if (0 == n)
       break;                    /* peer closed the TLS connection */
     if ( (GNUTLS_E_AGAIN == n) ||
          (GNUTLS_E_INTERRUPTED == n) )
       break;
     if (0 != gnutls_error_is_fatal ((int) n))
       tc->dead = 1;
     break;
   }
 }
 
 
 static void
 pump_and_drain (struct MHD_Daemon *d,
                 struct tls_client *tc,
                 unsigned int rounds)
 {
   unsigned int i;
 
   for (i = 0; i < rounds; i++)
   {
     run_once (d);
     tc_drain (tc);
   }
 }
 
 
 /**
  * Let the client and the daemon take turns at the handshake until it
  * completes, fails, or @a rounds is exhausted.  Exhausting @a rounds on
  * purpose (client mode 2) is what leaves MHD's connection parked in
  * #MHD_TLS_CONN_HANDSHAKING.
  */
 static void
 tc_handshake (struct MHD_Daemon *d,
               struct tls_client *tc,
               unsigned int rounds)
 {
   unsigned int i;
 
   if ( (NULL == tc->sess) ||
        (0 != tc->dead) ||
        (0 != tc->hs_done) )
     return;
   for (i = 0; i < rounds; i++)
   {
     int ret = gnutls_handshake (tc->sess);
 
     if (GNUTLS_E_SUCCESS == ret)
     {
       tc->hs_done = 1;
       stat_handshakes_ok++;
       return;
     }
     if (0 != gnutls_error_is_fatal (ret))
     {
       tc->dead = 1;
       stat_handshakes_failed++;
       return;
     }
     /* GNUTLS_E_AGAIN / GNUTLS_E_INTERRUPTED / a warning alert: give the
        daemon a chance to answer. */
     run_once (d);
   }
 }
 
 
 /**
  * Open a fresh connection: a socketpair, one end handed to MHD with
  * MHD_add_connection(), the other end ours.  With a real client the
  * GnuTLS session is set up here too, but the handshake itself is driven
  * by tc_handshake().
  *
  * @return 0 on success
  */
 static int
 tc_open (struct MHD_Daemon *d,
          struct tls_client *tc)
 {
   int sv[2];
   struct sockaddr_in sa;
   int fl;
 #if GNUTLS_VERSION_NUMBER >= 0x030500
   gnutls_init_flags_t flags;
 #else
   unsigned int flags;
 #endif
 
   memset (tc, 0, sizeof (*tc));
   tc->fd = -1;
   if (0 != socketpair (AF_UNIX, SOCK_STREAM, 0, sv))
     return -1;
   memset (&sa, 0, sizeof (sa));
   sa.sin_family = AF_INET;
   sa.sin_port = htons (44444);
   sa.sin_addr.s_addr = htonl (INADDR_LOOPBACK);
   if (MHD_YES != MHD_add_connection (d,
                                      (MHD_socket) sv[1],
                                      (const struct sockaddr *) &sa,
                                      (socklen_t) sizeof (sa)))
   {
     /* MHD has already closed sv[1] in that case */
     (void) close (sv[0]);
     return -1;
   }
   tc->fd = sv[0];
   stat_connections++;
   /* Our end must never block: the daemon is pumped from this very
      thread, so a blocking write would deadlock the process. */
   fl = fcntl (tc->fd, F_GETFL, 0);
   if (0 <= fl)
     (void) fcntl (tc->fd, F_SETFL, fl | O_NONBLOCK);
   if ( (CLIENT_TLS != cfg.mode) &&
        (CLIENT_TLS_ABANDON != cfg.mode) )
     return 0;
 
   if (GNUTLS_E_SUCCESS !=
       gnutls_certificate_allocate_credentials (&tc->cred))
   {
     tc->cred = NULL;
     tc->dead = 1;
     return 0;
   }
   if (cfg.client_cert)
   {
     gnutls_datum_t c;
     gnutls_datum_t k;
 
     c.data = (unsigned char *) (intptr_t) srv_self_signed_cert_pem;
     c.size = (unsigned int) strlen (srv_self_signed_cert_pem);
     k.data = (unsigned char *) (intptr_t) srv_self_signed_key_pem;
     k.size = (unsigned int) strlen (srv_self_signed_key_pem);
     (void) gnutls_certificate_set_x509_key_mem (tc->cred, &c, &k,
                                                 GNUTLS_X509_FMT_PEM);
   }
   flags = GNUTLS_CLIENT;
 #if GNUTLS_VERSION_MAJOR >= 3
   flags |= GNUTLS_NONBLOCK;
 #endif
 #if GNUTLS_VERSION_NUMBER >= 0x030402
   flags |= GNUTLS_NO_SIGNAL;
 #endif
   if (GNUTLS_E_SUCCESS != gnutls_init (&tc->sess, flags))
   {
     tc->sess = NULL;
     tc->dead = 1;
     return 0;
   }
   if (GNUTLS_E_SUCCESS !=
       gnutls_priority_set_direct (tc->sess,
                                   client_prio_tbl[cfg.client_prio_idx],
                                   NULL))
     (void) gnutls_priority_set_direct (tc->sess, "NORMAL", NULL);
   if (GNUTLS_E_SUCCESS !=
       gnutls_credentials_set (tc->sess, GNUTLS_CRD_CERTIFICATE, tc->cred))
     tc->dead = 1;
   if ( (cfg.client_sni) &&
        (0 != sni_name_len) )
     (void) gnutls_server_name_set (tc->sess,
                                    GNUTLS_NAME_DNS,
                                    sni_name,
                                    sni_name_len);
   gnutls_transport_set_int (tc->sess, tc->fd);
   /* GNUTLS_INDEFINITE_TIMEOUT: the default handshake timeout is a wall
      clock deadline, and this harness must not depend on the clock. */
   gnutls_handshake_set_timeout (tc->sess, 0);
   return 0;
 }
 
 
 static void
 tc_send (struct MHD_Daemon *d,
          struct tls_client *tc,
          const uint8_t *buf,
          size_t len)
 {
   size_t off = 0;
   unsigned int stall = 0;
 
   if ( (0 > tc->fd) ||
        (0 == len) )
     return;
   if (NULL == tc->sess)
   {
     while ( (off < len) &&
             (stall < 64) )
     {
       ssize_t s = send (tc->fd, buf + off, len - off, MSG_DONTWAIT);
 
       if (0 < s)
       {
         off += (size_t) s;
         stall = 0;
         continue;
       }
       stall++;
       pump_and_drain (d, tc, 2);
       if ( (0 > s) &&
            (EAGAIN != errno) &&
            (EWOULDBLOCK != errno) &&
            (EINTR != errno) )
         break;
     }
     return;
   }
   if ( (0 != tc->dead) ||
        (0 == tc->hs_done) )
     return;
   while ( (off < len) &&
           (stall < 64) )
   {
     /* On GNUTLS_E_AGAIN the call has to be repeated with exactly the
        same arguments, which is why @a off is only advanced on success. */
     ssize_t s = gnutls_record_send (tc->sess, buf + off, len - off);
 
     if (0 < s)
     {
       off += (size_t) s;
       stall = 0;
       continue;
     }
     if ( (GNUTLS_E_AGAIN == s) ||
          (GNUTLS_E_INTERRUPTED == s) )
     {
       stall++;
       pump_and_drain (d, tc, 2);
       continue;
     }
     if (0 != gnutls_error_is_fatal ((int) s))
       tc->dead = 1;
     break;
   }
 }
 
 
 /**
  * Tear the client end down.  Every GnuTLS object is released on every
  * path, including the ones where the session never got off the ground.
  */
 static void
 tc_close (struct MHD_Daemon *d,
           struct tls_client *tc)
 {
   if (NULL != tc->sess)
   {
     if ( (cfg.client_bye) &&
          (0 == tc->dead) &&
          (0 != tc->hs_done) )
     {
       unsigned int i;
 
       for (i = 0; i < 8; i++)
       {
         int ret = gnutls_bye (tc->sess, GNUTLS_SHUT_WR);
 
         if ( (GNUTLS_E_AGAIN != ret) &&
              (GNUTLS_E_INTERRUPTED != ret) )
           break;
         run_once (d);
       }
     }
     gnutls_deinit (tc->sess);
     tc->sess = NULL;
   }
   if (NULL != tc->cred)
   {
     gnutls_certificate_free_credentials (tc->cred);
     tc->cred = NULL;
   }
   if (0 <= tc->fd)
   {
     if (cfg.client_shut_wr)
       (void) shutdown (tc->fd, SHUT_WR);
     pump (d, 2);
     (void) close (tc->fd);
     tc->fd = -1;
   }
   tc->hs_done = 0;
   tc->dead = 1;
   pump (d, 4);
 }
 
 
 /**
  * Bring a fresh connection up to the point where payload can be sent.
  */
 static void
 tc_start (struct MHD_Daemon *d,
           struct tls_client *tc)
 {
   if (0 != tc_open (d, tc))
   {
     tc->fd = -1;
     return;
   }
   if (CLIENT_TLS == cfg.mode)
     tc_handshake (d, tc, HANDSHAKE_ROUNDS);
   else if (CLIENT_TLS_ABANDON == cfg.mode)
     tc_handshake (d, tc, cfg.hs_budget);
   else
     pump (d, 1);
 }
 
 
 /* ------------------------------------------------------------------ */
 /* PEM blobs assembled from the input                                  */
 /* ------------------------------------------------------------------ */
 
 /**
  * Build @a out as "-----BEGIN @a label-----\n<body>\n-----END @a
  * label-----\n", with @a body_len bytes of @a body as the payload.  The
  * result is always NUL terminated, because MHD calls strlen() on it.
  */
 static void
 build_fuzz_pem (char *out,
                 size_t out_size,
                 const char *label,
                 const uint8_t *body,
                 size_t body_len)
 {
   size_t o = 0;
   size_t i;
   int n;
 
   n = snprintf (out, out_size, "-----BEGIN %s-----\n", label);
   if ( (0 > n) ||
        ((size_t) n >= out_size) )
   {
     out[0] = '\0';
     return;
   }
   o = (size_t) n;
   if (body_len > FUZZ_PEM_BODY_MAX)
     body_len = FUZZ_PEM_BODY_MAX;
   for (i = 0; (i < body_len) && (o + 32 < out_size); i++)
   {
     /* Keep the blob a C string; a NUL inside would simply truncate it
        for MHD's strlen(), which is a less interesting shape. */
     out[o++] = (char) ((0 == body[i]) ? 'A' : body[i]);
   }
   n = snprintf (out + o, out_size - o, "\n-----END %s-----\n", label);
   if (0 > n)
     out[o] = '\0';
 }
 
 
 /* ------------------------------------------------------------------ */
 /* The fuzz target                                                     */
 /* ------------------------------------------------------------------ */
 
 int
 LLVMFuzzerTestOneInput (const uint8_t *data,
                         size_t size)
 {
   struct MHD_Daemon *d;
   struct MHD_OptionItem opts[12];
   unsigned int nopt = 0;
   unsigned int flags;
   struct tls_client tc;
   size_t pos;
   unsigned int nseg = 0;
   unsigned int nconn = 1;
 
   /* Must happen before the first write() into the socketpair; see
      fuzz_ignore_sigpipe() in fuzz_common.h for why the process dies
      without it.  Idempotent. */
   fuzz_ignore_sigpipe ();
 
   /* The ten configuration bytes are mandatory. */
   if (size < 10)
     return 0;
 
   resp_len = 0;
   memset (&cfg, 0, sizeof (cfg));
 
   {
     const char *nm = sni_name_tbl[(data[9] & 0x07) % SNI_NAME_COUNT];
 
     sni_name_len = strlen (nm);
     memcpy (sni_name, nm, sni_name_len + 1);
   }
 
   cfg.cert = cred_tbl[data[0] % CRED_COUNT].cert;
   cfg.key = cred_tbl[data[0] % CRED_COUNT].key;
 
   cfg.use_trust = (0 != (data[1] & 0x01));
   cfg.use_dhparams = (0 != (data[1] & 0x02));
   cfg.use_sni = (0 != (data[1] & 0x04));
   cfg.use_prio = (0 != (data[1] & 0x08));
   cfg.use_cred_type = (0 != (data[1] & 0x10));
   cfg.no_alpn = (0 != (data[1] & 0x20));
   cfg.key_password = (0 != (data[1] & 0x40));
   cfg.prio_append = (0 != (data[1] & 0x80));
 
   cfg.prio_idx = (unsigned int) (data[2] % PRIO_COUNT);
 
   cfg.cred_type_idx = (unsigned int) (data[3] & 0x07) % CRED_TYPE_COUNT;
   cfg.sni_mode =
     (enum sni_behaviour) (((unsigned int) (data[3] >> 3) & 0x07)
                           % (unsigned int) SNI_BEHAVIOUR_COUNT);
   cfg.trust_garbage = (0 != (data[3] & 0x40));
   cfg.dh_garbage = (0 != (data[3] & 0x80));
 
   cfg.mode = (enum client_mode) (data[4] & 0x03);
   cfg.client_sni = (0 != (data[4] & 0x04));
   cfg.client_cert = (0 != (data[4] & 0x08));
   cfg.client_prio_idx = (unsigned int) ((data[4] >> 4) & 0x03);
   cfg.client_bye = (0 != (data[4] & 0x40));
   cfg.client_shut_wr = (0 != (data[4] & 0x80));
 
   cfg.mem_limit = mem_limit_tbl[(data[5] & 0x0F) % MEM_LIMIT_COUNT];
   cfg.loop_mode = (unsigned int) ((data[5] >> 4) & 0x03);
 
   cfg.resp_kind = (unsigned int) (data[6] & 0x03);
   cfg.conn_info = (0 != (data[6] & 0x04));
   cfg.daemon_info = (0 != (data[6] & 0x08));
   cfg.conn_option = (0 != (data[6] & 0x10));
   cfg.error_reply = (0 != (data[6] & 0x20));
   cfg.resp_header = (0 != (data[6] & 0x40));
   cfg.quiesce = (0 != (data[6] & 0x80));
 
   cfg.hs_budget = 1u + (unsigned int) (data[7] & 0x07);
   cfg.use_tls = (0 == (data[7] & 0x08));
   cfg.allow_upgrade =
     (0 != (data[7] & 0x10)) &&
     (MHD_YES == MHD_is_feature_supported (MHD_FEATURE_UPGRADE));
   cfg.extra_pump = (unsigned int) ((data[7] >> 5) & 0x07);
 
   /* A real handshake is pointless without a working credential setup on
      our own side; fall back to the raw modes if the SNI certificates
      could not be parsed. */
   if ( (cfg.use_sni) &&
        (0 != sni_hosts_init ()) )
     cfg.use_sni = 0;
 
   /* The PEM blobs built from the input.  They are only referenced by
      cred_tbl entries 12-14, but filling them unconditionally keeps this
      out of the option assembly below. */
   {
     size_t body = (size_t) data[8] * 4u;
 
     if (body > size - 10)
       body = size - 10;
     build_fuzz_pem (fuzz_cert_pem, sizeof (fuzz_cert_pem),
                     "CERTIFICATE", data + 10, body);
     build_fuzz_pem (fuzz_key_pem, sizeof (fuzz_key_pem),
                     "PRIVATE KEY", data + 10, body);
   }
 
   if (0 != cfg.mem_limit)
   {
     opts[nopt].option = MHD_OPTION_CONNECTION_MEMORY_LIMIT;
     opts[nopt].value = (intptr_t) cfg.mem_limit;
     opts[nopt].ptr_value = NULL;
     nopt++;
   }
   if (NULL != cfg.key)
   {
     opts[nopt].option = MHD_OPTION_HTTPS_MEM_KEY;
     opts[nopt].value = 0;
     opts[nopt].ptr_value = (void *) (intptr_t) cfg.key;
     nopt++;
   }
   if (NULL != cfg.cert)
   {
     opts[nopt].option = MHD_OPTION_HTTPS_MEM_CERT;
     opts[nopt].value = 0;
     opts[nopt].ptr_value = (void *) (intptr_t) cfg.cert;
     nopt++;
   }
   if (cfg.key_password)
   {
     opts[nopt].option = MHD_OPTION_HTTPS_KEY_PASSWORD;
     opts[nopt].value = 0;
     opts[nopt].ptr_value = (void *) (intptr_t) https_key_password;
     nopt++;
   }
   if (cfg.use_trust)
   {
     opts[nopt].option = MHD_OPTION_HTTPS_MEM_TRUST;
     opts[nopt].value = 0;
     opts[nopt].ptr_value = (void *) (intptr_t)
                            (cfg.trust_garbage ? garbage_cert_pem
                             : ca_cert_pem);
     nopt++;
   }
   if (cfg.use_dhparams)
   {
     opts[nopt].option = MHD_OPTION_HTTPS_MEM_DHPARAMS;
     opts[nopt].value = 0;
     opts[nopt].ptr_value = (void *) (intptr_t)
                            (cfg.dh_garbage ? garbage_dh_pem : dh_params_pem);
     nopt++;
   }
   if (cfg.use_prio)
   {
     opts[nopt].option = cfg.prio_append
                         ? MHD_OPTION_HTTPS_PRIORITIES_APPEND
                         : MHD_OPTION_HTTPS_PRIORITIES;
     opts[nopt].value = 0;
     opts[nopt].ptr_value = (void *) (intptr_t) prio_tbl[cfg.prio_idx];
     nopt++;
   }
   if (cfg.use_cred_type)
   {
     opts[nopt].option = MHD_OPTION_HTTPS_CRED_TYPE;
     opts[nopt].value = (intptr_t) cred_type_tbl[cfg.cred_type_idx];
     opts[nopt].ptr_value = NULL;
     nopt++;
   }
   if (cfg.no_alpn)
   {
     opts[nopt].option = MHD_OPTION_TLS_NO_ALPN;
     opts[nopt].value = 1;
     opts[nopt].ptr_value = NULL;
     nopt++;
   }
   opts[nopt].option = MHD_OPTION_END;
   opts[nopt].value = 0;
   opts[nopt].ptr_value = NULL;
 
   flags = MHD_USE_NO_LISTEN_SOCKET;
   if (cfg.use_tls)
     flags |= MHD_USE_TLS;
   if (fuzz_verbose)
     flags |= MHD_USE_ERROR_LOG;
   if (cfg.allow_upgrade)
     flags |= MHD_ALLOW_UPGRADE;
 
   MHD_set_panic_func (&panic_cb, NULL);
   d = MHD_start_daemon (flags,
                         0,
                         NULL, NULL,
                         &ahc, NULL,
                         MHD_OPTION_ARRAY, opts,
                         /* Passed through the varargs rather than through
                            the option array: the array's ptr_value is a
                            void *, and a function pointer does not
                            portably fit in one.  A NULL here is exactly
                            equivalent to not passing the option. */
                         MHD_OPTION_HTTPS_CERT_CALLBACK,
                         cfg.use_sni ? &sni_callback : NULL,
                         MHD_OPTION_END);
   if (NULL == d)
   {
     stat_daemons_failed++;
     return 0;
   }
   stat_daemons++;
   if (! stats_registered)
   {
     stats_registered = 1;
     (void) atexit (&print_stats);
   }
   if (cfg.daemon_info)
   {
     (void) MHD_get_daemon_info (d, MHD_DAEMON_INFO_LISTEN_FD);
     (void) MHD_get_daemon_info (d, MHD_DAEMON_INFO_FLAGS);
     (void) MHD_get_daemon_info (d, MHD_DAEMON_INFO_CURRENT_CONNECTIONS);
     (void) MHD_get_daemon_info (d, MHD_DAEMON_INFO_BIND_PORT);
   }
 
   /* The connection is opened lazily, when the first segment that carries
      wire data is reached, so that a leading op 1 segment can still
      override the server name byte 9 selected. */
   tc.sess = NULL;
   tc.cred = NULL;
   tc.fd = -1;
   tc.hs_done = 0;
   tc.dead = 1;
 
   pos = 10u;
   while ( (pos + 2 <= size) &&
           (nseg < MAX_SEGMENTS) )
   {
     unsigned int hdr = (unsigned int) data[pos]
                        | ((unsigned int) data[pos + 1] << 8);
     unsigned int op = hdr >> 14;
     size_t slen = (size_t) (hdr & 0x3FFF);
 
     pos += 2;
     nseg++;
     if (slen > size - pos)
       slen = size - pos;
 
     if (1 == op)
     {
       /* Server name declaration for the next connection, not wire data. */
       size_t n = slen;
 
       if (n > MAX_SNI_LEN)
         n = MAX_SNI_LEN;
       memcpy (sni_name, data + pos, n);
       /* GnuTLS wants a plain host name, and an embedded NUL would only
          shorten it behind our back. */
       while ( (0 != n) &&
               ('\0' == sni_name[n - 1]) )
         n--;
       sni_name[n] = '\0';
       sni_name_len = n;
       pos += slen;
       continue;
     }
     if (0 > tc.fd)
     {
       tc_start (d, &tc);
       if (0 > tc.fd)
         break;
     }
     else if ( (3 == op) &&
               (nconn < MAX_CONNECTIONS) )
     {
       tc_close (d, &tc);
       tc_start (d, &tc);
       nconn++;
       if (0 > tc.fd)
         break;
     }
     if (0 != slen)
       tc_send (d, &tc, data + pos, slen);
     pos += slen;
     pump_and_drain (d, &tc, (2 == op) ? (6u + cfg.extra_pump) : 3u);
   }
   if (0 > tc.fd)
     tc_start (d, &tc);
   pump_and_drain (d, &tc, 2u + cfg.extra_pump);
   tc_close (d, &tc);
 
   if (cfg.quiesce)
     (void) MHD_quiesce_daemon (d);
   MHD_stop_daemon (d);
   return 0;
 }
 
 
 /* ------------------------------------------------------------------ */
 /* Structure-aware generator                                           */
 /* ------------------------------------------------------------------ */
 
 struct sbuf
 {
   uint8_t *p;
   size_t len;
   size_t cap;
 };
 
 
 static void
 sb_raw (struct sbuf *b,
         const void *v,
         size_t n)
 {
   if (b->len + n > b->cap)
     n = b->cap - b->len;
   memcpy (b->p + b->len, v, n);
   b->len += n;
 }
 
 
 static void
 sb_str (struct sbuf *b,
         const char *s)
 {
   sb_raw (b, s, strlen (s));
 }
 
 
 static void
 sb_u32 (struct sbuf *b,
         uint32_t v)
 {
   char tmp[16];
   unsigned int n = 0;
 
   do
   {
     tmp[n++] = (char) ('0' + (v % 10u));
     v /= 10u;
   }
   while ( (0 != v) &&
           (n < sizeof (tmp)) );
   while (0 != n)
   {
     char c = tmp[--n];
 
     sb_raw (b, &c, 1);
   }
 }
 
 
 enum gen_shape
 {
   SHAPE_TLS_HTTP = 0,   /**< good credentials, real handshake, HTTP over TLS */
   SHAPE_RAW_BYTES,      /**< good credentials, junk at the TLS socket */
   SHAPE_ABANDON,        /**< a real client that walks away mid-handshake */
   SHAPE_BAD_CREDS,      /**< mismatched/garbage/absent key or certificate */
   SHAPE_BAD_OPTIONS,    /**< bogus priorities, credential types, no MHD_USE_TLS */
   SHAPE_SNI,            /**< the certificate callback, all behaviours */
   SHAPE_PEM_FUZZ,       /**< PEM blobs built from the generator's own bytes */
   SHAPE_RECORDS,        /**< hand-built TLS records */
   SHAPE_COUNT
 };
 
 static int forced_shape = -1;
 static int forced_shape_read;
 
 static const char *const gen_methods[] = {
   "GET", "POST", "HEAD", "PUT", "OPTIONS", "BREW"
 };
 
 static const char *const gen_targets[] = {
   "/", "/a", "/index.html", "/a?b=c", "/%41%42", "*", "//"
 };
 
 static const char *const gen_versions[] = {
   "HTTP/1.1", "HTTP/1.0", "HTTP/1.2", "HTTP/9.9"
 };
 
 static const char *const gen_hdr_names[] = {
   "Host", "User-Agent", "Accept", "Connection", "X-Fuzz", "Cookie",
   "Content-Type", "Expect"
 };
 
 static const char *const gen_hdr_values[] = {
   "x", "localhost", "*/*", "keep-alive", "close", "100-continue",
   "text/plain", "a=b"
 };
 
 
 /**
  * A plain HTTP request; over TLS this is what makes MHD leave the
  * handshake state machine and enter the ordinary parser.
  */
 static void
 gen_http_request (struct fuzz_rng *rng,
                   struct sbuf *b)
 {
   unsigned int nh;
   unsigned int i;
   int with_body;
 
   sb_str (b, gen_methods[fuzz_below (rng, (uint32_t)
                                      (sizeof (gen_methods)
                                       / sizeof (gen_methods[0])))]);
   sb_str (b, " ");
   sb_str (b, gen_targets[fuzz_below (rng, (uint32_t)
                                      (sizeof (gen_targets)
                                       / sizeof (gen_targets[0])))]);
   sb_str (b, " ");
   sb_str (b, gen_versions[fuzz_below (rng, (uint32_t)
                                       (sizeof (gen_versions)
                                        / sizeof (gen_versions[0])))]);
   sb_str (b, "\r\n");
   with_body = fuzz_chance (rng, 3);
   nh = fuzz_below (rng, 4);
   for (i = 0; i < nh; i++)
   {
     sb_str (b, gen_hdr_names[fuzz_below (rng, (uint32_t)
                                          (sizeof (gen_hdr_names)
                                           / sizeof (gen_hdr_names[0])))]);
     sb_str (b, ": ");
     sb_str (b, gen_hdr_values[fuzz_below (rng, (uint32_t)
                                           (sizeof (gen_hdr_values)
                                            / sizeof (gen_hdr_values[0])))]);
     sb_str (b, "\r\n");
   }
   if (with_body)
   {
     unsigned int blen = fuzz_below (rng, 64);
 
     sb_str (b, "Content-Length: ");
     sb_u32 (b, blen);
     sb_str (b, "\r\n\r\n");
     for (i = 0; i < blen; i++)
     {
       char c = (char) ('a' + (int) fuzz_below (rng, 26));
 
       sb_raw (b, &c, 1);
     }
     return;
   }
   sb_str (b, "\r\n");
 }
 
 
 /**
  * Something that looks like a TLS record: a content type, a version, a
  * length and a payload.  Most of this lands in GnuTLS's record parser
  * rather than in MHD, which is why the generator spends only one shape
  * on it.
  */
 static void
 gen_tls_records (struct fuzz_rng *rng,
                  struct sbuf *b)
 {
   unsigned int n = 1 + fuzz_below (rng, 4);
   unsigned int i;
   unsigned int j;
 
   for (i = 0; i < n; i++)
   {
     uint8_t hdr[5];
     unsigned int plen = fuzz_below (rng, 96);
     unsigned int declared = fuzz_chance (rng, 3)
                             ? fuzz_below (rng, 0x4000)
                             : plen;
 
     hdr[0] = fuzz_chance (rng, 4)
              ? fuzz_byte (rng)
              : (uint8_t) (20 + fuzz_below (rng, 4));
     hdr[1] = 0x03;
     hdr[2] = (uint8_t) fuzz_below (rng, 5);
     hdr[3] = (uint8_t) ((declared >> 8) & 0xFF);
     hdr[4] = (uint8_t) (declared & 0xFF);
     sb_raw (b, hdr, sizeof (hdr));
     for (j = 0; j < plen; j++)
     {
       uint8_t v = fuzz_byte (rng);
 
       sb_raw (b, &v, 1);
     }
   }
 }
 
 
 /**
  * Number of leading entries of #prio_tbl that GnuTLS accepts.  Beyond
  * that the daemon refuses to start, which is a fine thing to fuzz but a
  * poor way to reach the handshake.
  */
 #define PRIO_VALID_COUNT 7
 
 
 /**
  * Constrain the configuration bytes so that MHD_start_daemon() actually
  * succeeds.  Used by the shapes whose point is what happens *after* the
  * daemon is up; the option surface itself is fuzzed by the shapes that
  * do not call this.
  */
 static void
 make_daemon_startable (struct fuzz_rng *rng,
                        uint8_t *cfg_bytes)
 {
   cfg_bytes[1] &= (uint8_t) ~0x10u;      /* no credential type override */
   cfg_bytes[3] &= (uint8_t) ~0xC0u;      /* valid trust store, valid DH */
   if (0 != (cfg_bytes[1] & 0x08u))
     cfg_bytes[2] = (uint8_t) fuzz_below (rng, PRIO_VALID_COUNT);
   cfg_bytes[7] &= (uint8_t) ~0x08u;      /* keep MHD_USE_TLS */
 }
 
 
 /**
  * Emit one segment with the given op code.
  */
 static void
 emit_segment (struct sbuf *out,
               unsigned int op,
               const uint8_t *payload,
               size_t len)
 {
   unsigned int hv;
   uint8_t hdr[2];
 
   if (len > 0x3FFF)
     len = 0x3FFF;
   hv = (op << 14) | (unsigned int) len;
   hdr[0] = (uint8_t) (hv & 0xFF);
   hdr[1] = (uint8_t) (hv >> 8);
   sb_raw (out, hdr, 2);
   sb_raw (out, payload, len);
 }
 
 
 static size_t
 fuzz_generate (struct fuzz_rng *rng,
                uint8_t *buf,
                size_t cap)
 {
   struct sbuf out;
   struct sbuf rb;
   uint8_t req[GEN_BUF_SIZE];
   uint8_t cfg_bytes[10];
   enum gen_shape shape;
   unsigned int nreq;
   unsigned int i;
 
   out.p = buf;
   out.len = 0;
   out.cap = cap;
 
   if (! forced_shape_read)
   {
     const char *e = getenv ("MHD_FUZZ_SHAPE");
 
     forced_shape_read = 1;
     if (NULL != e)
       forced_shape = atoi (e);
   }
   if (0 <= forced_shape)
     shape = (enum gen_shape) (forced_shape % (int) SHAPE_COUNT);
   else
     shape = (enum gen_shape) fuzz_below (rng, (uint32_t) SHAPE_COUNT);
 
   for (i = 0; i < sizeof (cfg_bytes); i++)
     cfg_bytes[i] = fuzz_byte (rng);
 
   /* Byte 0 picks the credentials, byte 4 (bits 0-1) the client, and byte
      1 which options are passed at all; every shape below narrows exactly
      those and leaves the rest of the configuration space random. */
   cfg_bytes[7] &= (uint8_t) ~0x08u;      /* keep MHD_USE_TLS by default */
   switch (shape)
   {
   case SHAPE_TLS_HTTP:
     cfg_bytes[0] = (uint8_t) (fuzz_chance (rng, 2) ? 0 : 1);
     cfg_bytes[4] = (uint8_t) ((cfg_bytes[4] & ~0x03u) | CLIENT_TLS);
     cfg_bytes[1] &= (uint8_t) ~0x04u;    /* no SNI callback */
     make_daemon_startable (rng, cfg_bytes);
     break;
   case SHAPE_RAW_BYTES:
     cfg_bytes[0] = 0;
     cfg_bytes[4] = (uint8_t) ((cfg_bytes[4] & ~0x03u) | CLIENT_RAW);
     make_daemon_startable (rng, cfg_bytes);
     break;
   case SHAPE_ABANDON:
     cfg_bytes[0] = (uint8_t) (fuzz_chance (rng, 2) ? 0 : 1);
     cfg_bytes[4] = (uint8_t) ((cfg_bytes[4] & ~0x03u) | CLIENT_TLS_ABANDON);
     cfg_bytes[7] = (uint8_t) ((cfg_bytes[7] & ~0x07u)
                               + fuzz_below (rng, 6));
     make_daemon_startable (rng, cfg_bytes);
     break;
   case SHAPE_BAD_CREDS:
     /* entries 2-11 of cred_tbl are the broken ones */
     cfg_bytes[0] = (uint8_t) (2 + fuzz_below (rng, 10));
     cfg_bytes[4] = (uint8_t) ((cfg_bytes[4] & ~0x03u)
                               | (fuzz_chance (rng, 2) ? CLIENT_TLS
                                  : CLIENT_RAW));
     break;
   case SHAPE_BAD_OPTIONS:
     cfg_bytes[1] |= 0x18u;               /* priorities + credential type */
     cfg_bytes[2] = (uint8_t) fuzz_below (rng, (uint32_t) PRIO_COUNT);
     cfg_bytes[3] = fuzz_byte (rng);
     if (fuzz_chance (rng, 4))
       cfg_bytes[7] |= 0x08u;             /* HTTPS options, but no MHD_USE_TLS */
     cfg_bytes[4] = (uint8_t) ((cfg_bytes[4] & ~0x03u)
                               | (fuzz_chance (rng, 2) ? CLIENT_TLS
                                  : CLIENT_RAW));
     break;
   case SHAPE_SNI:
     cfg_bytes[0] = (uint8_t) (fuzz_chance (rng, 3) ? 6 : 0);
     cfg_bytes[3] = (uint8_t)
                    ((cfg_bytes[3] & ~0x38u)
                     | (fuzz_below (rng, (uint32_t) SNI_BEHAVIOUR_COUNT) << 3));
     cfg_bytes[4] = (uint8_t) ((cfg_bytes[4] & ~0x03u) | CLIENT_TLS | 0x04u);
     cfg_bytes[9] = (uint8_t) fuzz_below (rng, (uint32_t) SNI_NAME_COUNT);
     make_daemon_startable (rng, cfg_bytes);
     cfg_bytes[1] |= 0x04u;               /* the certificate callback */
     break;
   case SHAPE_PEM_FUZZ:
     cfg_bytes[0] = (uint8_t) (12 + fuzz_below (rng, 3));
     cfg_bytes[8] = (uint8_t) (1 + fuzz_below (rng, 64));
     cfg_bytes[4] = (uint8_t) ((cfg_bytes[4] & ~0x03u)
                               | (fuzz_chance (rng, 2) ? CLIENT_TLS
                                  : CLIENT_RAW));
     break;
   case SHAPE_RECORDS:
     cfg_bytes[0] = 0;
     cfg_bytes[4] = (uint8_t) ((cfg_bytes[4] & ~0x03u) | CLIENT_RECORDS);
     make_daemon_startable (rng, cfg_bytes);
     break;
   case SHAPE_COUNT:
   default:
     break;
   }
   /* Byte 9 already carries a server name; now and then hand the same
      one over as an op 1 segment instead, so that the segment form is
      exercised too.  Generated inputs are never written to corpus/, so
      unlike the seeds they may use op 1 (see the note at the top). */
   sb_raw (&out, cfg_bytes, sizeof (cfg_bytes));
   if (fuzz_chance (rng, 4))
   {
     const char *nm = sni_name_tbl[cfg_bytes[9] & 0x07];
 
     emit_segment (&out, 1u, (const uint8_t *) nm, strlen (nm));
   }
 
   nreq = 1u + (fuzz_chance (rng, 4) ? 1u : 0u);
   for (i = 0; i < nreq; i++)
   {
     unsigned int op;
 
     rb.p = req;
     rb.len = 0;
     rb.cap = sizeof (req);
     switch (shape)
     {
     case SHAPE_RECORDS:
       gen_tls_records (rng, &rb);
       break;
     case SHAPE_RAW_BYTES:
       {
         unsigned int n = 1 + fuzz_below (rng, 256);
         unsigned int j;
 
         for (j = 0; j < n; j++)
         {
           uint8_t v = fuzz_byte (rng);
 
           sb_raw (&rb, &v, 1);
         }
         break;
       }
     default:
       gen_http_request (rng, &rb);
       break;
     }
     if (0 != i)
       op = 3u;                           /* a fresh connection */
     else
       op = fuzz_chance (rng, 3) ? 2u : 0u;
     /* Split the payload now and then: MHD's parser is incremental and
        the TLS record boundaries move with the split. */
     if ( (rb.len > 8) &&
          fuzz_chance (rng, 3) )
     {
       size_t cut = 1 + fuzz_below (rng, (uint32_t) (rb.len - 1));
 
       emit_segment (&out, op, req, cut);
       emit_segment (&out, 2u, req + cut, rb.len - cut);
     }
     else
     {
       emit_segment (&out, op, req, rb.len);
     }
   }
   return out.len;
 }
 
 
 /* ------------------------------------------------------------------ */
 /* Built-in seed corpus                                                */
 /* ------------------------------------------------------------------ */
 
 struct seed_part
 {
   unsigned int op;              /**< 0 send, 1 server name, 2 send+pump, 3 new */
   const char *txt;              /**< NUL terminated payload */
 };
 
 struct seed_def
 {
   const char *name;
   unsigned char cfg[10];
   struct seed_part parts[4];
 };
 
 #define P_END { 0, NULL }
 
 /* The configuration bytes are written out in full so that a seed can be
    read without decoding: see the input format at the top of this file. */
 static const struct seed_def seeds[] = {
   /* A complete TLS 1.3 handshake followed by an ordinary request: the
      only shape that reaches the handshake -> HTTP parser transition. */
   { "tls-handshake-get",
     { 0, 0x00, 0, 0, 0x41, 0x00, 0x04, 0x00, 0, 0 },
     { { 0, "GET / HTTP/1.1\r\nHost: x\r\n\r\n" }, P_END, P_END, P_END } },
 
   /* The same, but the request arrives in two TLS records. */
   { "tls-handshake-split",
     { 0, 0x00, 0, 0, 0x41, 0x00, 0x04, 0x00, 0, 0 },
     { { 0, "GET / HTTP/1.1\r\nHo" },
       { 2, "st: x\r\n\r\n" }, P_END, P_END } },
 
   /* Keep-alive over TLS: two requests on one session, then gnutls_bye(). */
   { "tls-keepalive",
     { 0, 0x00, 0, 0, 0x41, 0x00, 0x00, 0x00, 0, 0 },
     { { 0, "GET /a HTTP/1.1\r\nHost: x\r\n\r\n" },
       { 2, "GET /b HTTP/1.1\r\nHost: x\r\nConnection: close\r\n\r\n" },
       P_END, P_END } },
 
   /* A second connection, i.e. a second handshake on the same daemon. */
   { "tls-second-connection",
     { 0, 0x00, 0, 0, 0x41, 0x00, 0x00, 0x00, 0, 0 },
     { { 0, "GET /a HTTP/1.1\r\nHost: x\r\n\r\n" },
       { 3, "GET /b HTTP/1.1\r\nHost: x\r\n\r\n" },
       P_END, P_END } },
 
   /* Plain HTTP at a TLS port: the record layer sees "GET ..." and the
      handshake fails, which is MHD_run_tls_handshake_()'s error arm. */
   { "plain-http-at-tls-port",
     { 0, 0x00, 0, 0, 0x00, 0x00, 0x00, 0x00, 0, 0 },
     { { 0, "GET / HTTP/1.1\r\nHost: x\r\n\r\n" }, P_END, P_END, P_END } },
 
   /* Nothing at all, then EOF: the connection dies in MHD_TLS_CONN_INIT. */
   { "eof-in-init",
     { 0, 0x00, 0, 0, 0x80, 0x00, 0x00, 0x00, 0, 0 },
     { { 0, "" }, P_END, P_END, P_END } },
 
   /* A real client that walks away after a single handshake round: MHD is
      left in MHD_TLS_CONN_HANDSHAKING when the socket closes. */
   { "abandon-handshake",
     { 0, 0x00, 0, 0, 0x02, 0x00, 0x00, 0x00, 0, 0 },
     { { 0, "" }, P_END, P_END, P_END } },
 
   /* Certificate and key do not belong together. */
   { "mismatched-key",
     { 2, 0x00, 0, 0, 0x01, 0x00, 0x00, 0x00, 0, 0 },
     { { 0, "GET / HTTP/1.1\r\nHost: x\r\n\r\n" }, P_END, P_END, P_END } },
 
   /* No certificate at all: MHD_start_daemon() has to fail cleanly. */
   { "no-certificate",
     { 6, 0x00, 0, 0, 0x01, 0x00, 0x00, 0x00, 0, 0 },
     { { 0, "GET / HTTP/1.1\r\nHost: x\r\n\r\n" }, P_END, P_END, P_END } },
 
   /* PEM armour with a payload that is not base64. */
   { "garbage-pem",
     { 10, 0x00, 0, 0, 0x01, 0x00, 0x00, 0x00, 0, 0 },
     { { 0, "GET / HTTP/1.1\r\nHost: x\r\n\r\n" }, P_END, P_END, P_END } },
 
   /* A priority string GnuTLS rejects (index 9 of prio_tbl). */
   { "bogus-priorities",
     { 0, 0x08, 9, 0, 0x01, 0x00, 0x00, 0x00, 0, 0 },
     { { 0, "GET / HTTP/1.1\r\nHost: x\r\n\r\n" }, P_END, P_END, P_END } },
 
   /* The same string through MHD_OPTION_HTTPS_PRIORITIES_APPEND. */
   { "bogus-priorities-append",
     { 0, 0x88, 10, 0, 0x01, 0x00, 0x00, 0x00, 0, 0 },
     { { 0, "GET / HTTP/1.1\r\nHost: x\r\n\r\n" }, P_END, P_END, P_END } },
 
   /* TLS 1.2 only on both ends, with the trust store and a client
      certificate request. */
   { "tls12-with-trust",
     { 0, 0x01, 2, 0, 0x29, 0x00, 0x04, 0x00, 0, 0 },
     { { 0, "GET / HTTP/1.1\r\nHost: x\r\n\r\n" }, P_END, P_END, P_END } },
 
   /* Valid Diffie-Hellman parameters (RFC 3526 group 14). */
   { "valid-dhparams",
     { 0, 0x02, 0, 0, 0x21, 0x00, 0x00, 0x00, 0, 0 },
     { { 0, "GET / HTTP/1.1\r\nHost: x\r\n\r\n" }, P_END, P_END, P_END } },
 
   /* Malformed Diffie-Hellman parameters: MHD_start_daemon() must fail. */
   { "garbage-dhparams",
     { 0, 0x02, 0, 0x80, 0x01, 0x00, 0x00, 0x00, 0, 0 },
     { { 0, "GET / HTTP/1.1\r\nHost: x\r\n\r\n" }, P_END, P_END, P_END } },
 
   /* A credential type MHD does not support (GNUTLS_CRD_ANON). */
   { "cred-type-anon",
     { 0, 0x10, 0, 0x02, 0x01, 0x00, 0x00, 0x00, 0, 0 },
     { { 0, "GET / HTTP/1.1\r\nHost: x\r\n\r\n" }, P_END, P_END, P_END } },
 
   /* GNUTLS_CRD_PSK without a PSK callback: the daemon starts, the
      handshake cannot. */
   { "cred-type-psk",
     { 0, 0x10, 0, 0x01, 0x01, 0x00, 0x00, 0x00, 0, 0 },
     { { 0, "GET / HTTP/1.1\r\nHost: x\r\n\r\n" }, P_END, P_END, P_END } },
 
   /* The SNI callback, answering for the presented name (byte 9 = 0,
      "test-mhdserver").  No op 1 segment here or below: see the note on
      the shared corpus at the top of this file. */
   { "sni-by-name",
     { 6, 0x04, 0, 0x18, 0x05, 0x00, 0x04, 0x00, 0, 0 },
     { { 0, "GET / HTTP/1.1\r\nHost: test-mhdserver\r\n\r\n" },
       P_END, P_END, P_END } },
 
   /* The SNI callback failing outright. */
   { "sni-callback-fails",
     { 6, 0x04, 0, 0x08, 0x05, 0x00, 0x00, 0x00, 0, 0 },
     { { 0, "GET / HTTP/1.1\r\nHost: x\r\n\r\n" },
       P_END, P_END, P_END } },
 
   /* The SNI callback answering with an empty certificate list. */
   { "sni-callback-empty",
     { 6, 0x04, 0, 0x10, 0x05, 0x00, 0x00, 0x00, 0, 0 },
     { { 0, "GET / HTTP/1.1\r\nHost: x\r\n\r\n" },
       P_END, P_END, P_END } },
 
   /* The SNI callback answering with a key that is not the certificate's
      (byte 9 = 1, "localhost"). */
   { "sni-callback-mismatch",
     { 6, 0x04, 0, 0x20, 0x05, 0x00, 0x00, 0x00, 0, 1 },
     { { 0, "GET / HTTP/1.1\r\nHost: x\r\n\r\n" },
       P_END, P_END, P_END } },
 
   /* The SNI callback answering with a certificate but no key. */
   { "sni-callback-no-key",
     { 6, 0x04, 0, 0x28, 0x05, 0x00, 0x00, 0x00, 0, 0 },
     { { 0, "GET / HTTP/1.1\r\nHost: x\r\n\r\n" },
       P_END, P_END, P_END } },
 
   /* An unknown server name with the by-name callback (byte 9 = 3,
      "nobody.example.org"): no certificate. */
   { "sni-unknown-name",
     { 6, 0x04, 0, 0x18, 0x05, 0x00, 0x00, 0x00, 0, 3 },
     { { 0, "GET / HTTP/1.1\r\nHost: x\r\n\r\n" },
       P_END, P_END, P_END } },
 
   /* A PEM blob assembled from the payload below (cred_tbl entry 14). */
   { "fuzzed-pem",
     { 14, 0x00, 0, 0, 0x01, 0x00, 0x00, 0x00, 32, 0 },
     { { 0, "MIIFSzCCAzOgAwIBAgIBBDANBgkqhkiG9w0BAQsFADCBgTELMAkGA1UEBhMCUlUx" },
       P_END, P_END, P_END } },
 
   /* A truncated TLS record header, then EOF. */
   { "short-record",
     { 0, 0x00, 0, 0, 0x00, 0x00, 0x00, 0x00, 0, 0 },
     { { 0, "\x16\x03\x01" }, P_END, P_END, P_END } },
 
   /* A record that promises far more data than it delivers. */
   { "record-length-lie",
     { 0, 0x00, 0, 0, 0x00, 0x00, 0x00, 0x00, 0, 0 },
     { { 0, "\x16\x03\x01\x3f\xff\x01\x02\x03\x04" }, P_END, P_END, P_END } },
 
   /* The HTTPS options on a daemon started without MHD_USE_TLS. */
   { "no-use-tls-flag",
     { 0, 0x0F, 0, 0, 0x00, 0x00, 0x00, 0x08, 0, 0 },
     { { 0, "GET / HTTP/1.1\r\nHost: x\r\n\r\n" }, P_END, P_END, P_END } },
 
   /* A tiny connection memory pool with a real TLS session. */
   { "small-pool-tls",
     { 0, 0x00, 0, 0, 0x41, 0x01, 0x00, 0x00, 0, 0 },
     { { 0, "GET /aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa HTTP/1.1\r\n"
         "Host: x\r\nX-Long: aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa\r\n\r\n" },
       P_END, P_END, P_END } },
 
   /* A request body over TLS, so that the receive adapter is used for
      more than the request line. */
   { "tls-request-body",
     { 0, 0x00, 0, 0, 0x41, 0x00, 0x00, 0x00, 0, 0 },
     { { 0, "POST /a HTTP/1.1\r\nHost: x\r\nContent-Length: 11\r\n\r\n"
         "hello world" },
       P_END, P_END, P_END } },
 
   /* The external event loop (MHD_get_fdset() + MHD_run_from_select()). */
   { "tls-external-loop",
     { 0, 0x00, 0, 0, 0x41, 0x10, 0x04, 0x00, 0, 0 },
     { { 0, "GET / HTTP/1.1\r\nHost: x\r\n\r\n" }, P_END, P_END, P_END } },
 
   /* MHD_quiesce_daemon() with a live TLS connection. */
   { "tls-quiesce",
     { 0, 0x00, 0, 0, 0x41, 0x00, 0x80, 0x00, 0, 0 },
     { { 0, "GET / HTTP/1.1\r\nHost: x\r\n\r\n" }, P_END, P_END, P_END } }
 };
 
 static uint8_t seed_render_buf[2048];
 
 
 static size_t
 fuzz_seed_count (void)
 {
   return sizeof (seeds) / sizeof (seeds[0]);
 }
 
 
 static const uint8_t *
 fuzz_seed_get (size_t idx,
                size_t *len)
 {
   const struct seed_def *sd = &seeds[idx];
   struct sbuf b;
   unsigned int i;
 
   b.p = seed_render_buf;
   b.len = 0;
   b.cap = sizeof (seed_render_buf);
   sb_raw (&b, sd->cfg, sizeof (sd->cfg));
   for (i = 0; i < sizeof (sd->parts) / sizeof (sd->parts[0]); i++)
   {
     if (NULL == sd->parts[i].txt)
       break;
     emit_segment (&b, sd->parts[i].op,
                   (const uint8_t *) sd->parts[i].txt,
                   strlen (sd->parts[i].txt));
   }
   *len = b.len;
   return seed_render_buf;
 }
 
 
 #else  /* ! HTTPS_SUPPORT */
 
 /*
  * MHD was configured without HTTPS (which is what
  * contrib/oss-fuzz/build.sh does for the MemorySanitizer build), so
  * there is no TLS layer to fuzz.  The file still has to produce a valid
  * fuzz target: LLVMFuzzerTestOneInput() must exist unconditionally, or
  * an OSS-Fuzz build of this harness would silently be an empty binary.
  */
 
 int
 LLVMFuzzerTestOneInput (const uint8_t *data,
                         size_t size)
 {
   fuzz_ignore_sigpipe ();
   (void) data;
   (void) size;
   return 0;
 }
 
 
 static size_t
 fuzz_generate (struct fuzz_rng *rng,
                uint8_t *buf,
                size_t cap)
 {
   (void) rng;
   if (0 == cap)
     return 0;
   buf[0] = 0;
   return 1;
 }
 
 
 static const uint8_t no_https_seed[] = { 0 };
 
 
 static size_t
 fuzz_seed_count (void)
 {
   return 1;
 }
 
 
 static const uint8_t *
 fuzz_seed_get (size_t idx,
                size_t *len)
 {
   (void) idx;
   *len = sizeof (no_https_seed);
   return no_https_seed;
 }
 
 
 #endif /* ! HTTPS_SUPPORT */
 
 /* end of fuzz_tls.c */