/* * TLS 1.2 and 1.3 client-side functions * * Copyright The Mbed TLS Contributors * SPDX-License-Identifier: Apache-2.0 OR GPL-2.0-or-later */ #include "common.h" #if defined(MBEDTLS_SSL_CLI_C) #if defined(MBEDTLS_SSL_PROTO_TLS1_3) || defined(MBEDTLS_SSL_PROTO_TLS1_2) #include #include "mbedtls/debug.h" #include "mbedtls/error.h" #include "mbedtls/platform.h" #include "ssl_client.h" #include "ssl_misc.h" #include "ssl_tls13_keys.h" #include "ssl_debug_helpers.h" #if defined(MBEDTLS_SSL_SERVER_NAME_INDICATION) MBEDTLS_CHECK_RETURN_CRITICAL static int ssl_write_hostname_ext(mbedtls_ssl_context *ssl, unsigned char *buf, const unsigned char *end, size_t *olen) { unsigned char *p = buf; size_t hostname_len; *olen = 0; if (ssl->hostname == NULL) { return 0; } MBEDTLS_SSL_DEBUG_MSG(3, ("client hello, adding server name extension: %s", ssl->hostname)); hostname_len = strlen(ssl->hostname); MBEDTLS_SSL_CHK_BUF_PTR(p, end, hostname_len + 9); /* * Sect. 3, RFC 6066 (TLS Extensions Definitions) * * In order to provide any of the server names, clients MAY include an * extension of type "server_name" in the (extended) client hello. The * "extension_data" field of this extension SHALL contain * "ServerNameList" where: * * struct { * NameType name_type; * select (name_type) { * case host_name: HostName; * } name; * } ServerName; * * enum { * host_name(0), (255) * } NameType; * * opaque HostName<1..2^16-1>; * * struct { * ServerName server_name_list<1..2^16-1> * } ServerNameList; * */ MBEDTLS_PUT_UINT16_BE(MBEDTLS_TLS_EXT_SERVERNAME, p, 0); p += 2; MBEDTLS_PUT_UINT16_BE(hostname_len + 5, p, 0); p += 2; MBEDTLS_PUT_UINT16_BE(hostname_len + 3, p, 0); p += 2; *p++ = MBEDTLS_BYTE_0(MBEDTLS_TLS_EXT_SERVERNAME_HOSTNAME); MBEDTLS_PUT_UINT16_BE(hostname_len, p, 0); p += 2; memcpy(p, ssl->hostname, hostname_len); *olen = hostname_len + 9; #if defined(MBEDTLS_SSL_PROTO_TLS1_3) mbedtls_ssl_tls13_set_hs_sent_ext_mask(ssl, MBEDTLS_TLS_EXT_SERVERNAME); #endif /* MBEDTLS_SSL_PROTO_TLS1_3 */ return 0; } #endif /* MBEDTLS_SSL_SERVER_NAME_INDICATION */ #if defined(MBEDTLS_SSL_ALPN) /* * ssl_write_alpn_ext() * * Structure of the application_layer_protocol_negotiation extension in * ClientHello: * * opaque ProtocolName<1..2^8-1>; * * struct { * ProtocolName protocol_name_list<2..2^16-1> * } ProtocolNameList; * */ MBEDTLS_CHECK_RETURN_CRITICAL static int ssl_write_alpn_ext(mbedtls_ssl_context *ssl, unsigned char *buf, const unsigned char *end, size_t *out_len) { unsigned char *p = buf; *out_len = 0; if (ssl->conf->alpn_list == NULL) { return 0; } MBEDTLS_SSL_DEBUG_MSG(3, ("client hello, adding alpn extension")); /* Check we have enough space for the extension type (2 bytes), the * extension length (2 bytes) and the protocol_name_list length (2 bytes). */ MBEDTLS_SSL_CHK_BUF_PTR(p, end, 6); MBEDTLS_PUT_UINT16_BE(MBEDTLS_TLS_EXT_ALPN, p, 0); /* Skip writing extension and list length for now */ p += 6; /* * opaque ProtocolName<1..2^8-1>; * * struct { * ProtocolName protocol_name_list<2..2^16-1> * } ProtocolNameList; */ for (const char **cur = ssl->conf->alpn_list; *cur != NULL; cur++) { /* * mbedtls_ssl_conf_set_alpn_protocols() checked that the length of * protocol names is less than 255. */ size_t protocol_name_len = strlen(*cur); MBEDTLS_SSL_CHK_BUF_PTR(p, end, 1 + protocol_name_len); *p++ = (unsigned char) protocol_name_len; memcpy(p, *cur, protocol_name_len); p += protocol_name_len; } *out_len = p - buf; /* List length = *out_len - 2 (ext_type) - 2 (ext_len) - 2 (list_len) */ MBEDTLS_PUT_UINT16_BE(*out_len - 6, buf, 4); /* Extension length = *out_len - 2 (ext_type) - 2 (ext_len) */ MBEDTLS_PUT_UINT16_BE(*out_len - 4, buf, 2); #if defined(MBEDTLS_SSL_PROTO_TLS1_3) mbedtls_ssl_tls13_set_hs_sent_ext_mask(ssl, MBEDTLS_TLS_EXT_ALPN); #endif /* MBEDTLS_SSL_PROTO_TLS1_3 */ return 0; } #endif /* MBEDTLS_SSL_ALPN */ #if defined(MBEDTLS_SSL_TLS1_2_SOME_ECC) || \ defined(MBEDTLS_SSL_TLS1_3_KEY_EXCHANGE_MODE_SOME_EPHEMERAL_ENABLED) /* * Function for writing a supported groups (TLS 1.3) or supported elliptic * curves (TLS 1.2) extension. * * The "extension_data" field of a supported groups extension contains a * "NamedGroupList" value (TLS 1.3 RFC8446): * enum { * secp256r1(0x0017), secp384r1(0x0018), secp521r1(0x0019), * x25519(0x001D), x448(0x001E), * ffdhe2048(0x0100), ffdhe3072(0x0101), ffdhe4096(0x0102), * ffdhe6144(0x0103), ffdhe8192(0x0104), * ffdhe_private_use(0x01FC..0x01FF), * ecdhe_private_use(0xFE00..0xFEFF), * (0xFFFF) * } NamedGroup; * struct { * NamedGroup named_group_list<2..2^16-1>; * } NamedGroupList; * * The "extension_data" field of a supported elliptic curves extension contains * a "NamedCurveList" value (TLS 1.2 RFC 8422): * enum { * deprecated(1..22), * secp256r1 (23), secp384r1 (24), secp521r1 (25), * x25519(29), x448(30), * reserved (0xFE00..0xFEFF), * deprecated(0xFF01..0xFF02), * (0xFFFF) * } NamedCurve; * struct { * NamedCurve named_curve_list<2..2^16-1> * } NamedCurveList; * * The TLS 1.3 supported groups extension was defined to be a compatible * generalization of the TLS 1.2 supported elliptic curves extension. They both * share the same extension identifier. * */ #define SSL_WRITE_SUPPORTED_GROUPS_EXT_TLS1_2_FLAG 1 #define SSL_WRITE_SUPPORTED_GROUPS_EXT_TLS1_3_FLAG 2 MBEDTLS_CHECK_RETURN_CRITICAL static int ssl_write_supported_groups_ext(mbedtls_ssl_context *ssl, unsigned char *buf, const unsigned char *end, int flags, size_t *out_len) { unsigned char *p = buf; unsigned char *named_group_list; /* Start of named_group_list */ size_t named_group_list_len; /* Length of named_group_list */ const uint16_t *group_list = mbedtls_ssl_get_groups(ssl); *out_len = 0; MBEDTLS_SSL_DEBUG_MSG(3, ("client hello, adding supported_groups extension")); /* Check if we have space for header and length fields: * - extension_type (2 bytes) * - extension_data_length (2 bytes) * - named_group_list_length (2 bytes) */ MBEDTLS_SSL_CHK_BUF_PTR(p, end, 6); p += 6; named_group_list = p; if (group_list == NULL) { return MBEDTLS_ERR_SSL_BAD_CONFIG; } for (; *group_list != 0; group_list++) { int propose_group = 0; MBEDTLS_SSL_DEBUG_MSG(3, ("got supported group(%04x)", *group_list)); #if defined(MBEDTLS_SSL_TLS1_3_KEY_EXCHANGE_MODE_SOME_EPHEMERAL_ENABLED) if (flags & SSL_WRITE_SUPPORTED_GROUPS_EXT_TLS1_3_FLAG) { #if defined(PSA_WANT_ALG_ECDH) if (mbedtls_ssl_tls13_named_group_is_ecdhe(*group_list) && (mbedtls_ssl_get_ecp_group_id_from_tls_id(*group_list) != MBEDTLS_ECP_DP_NONE)) { propose_group = 1; } #endif #if defined(PSA_WANT_ALG_FFDH) if (mbedtls_ssl_tls13_named_group_is_ffdh(*group_list)) { propose_group = 1; } #endif } #endif /* MBEDTLS_SSL_TLS1_3_KEY_EXCHANGE_MODE_SOME_EPHEMERAL_ENABLED */ #if defined(MBEDTLS_SSL_TLS1_2_SOME_ECC) if ((flags & SSL_WRITE_SUPPORTED_GROUPS_EXT_TLS1_2_FLAG) && mbedtls_ssl_tls12_named_group_is_ecdhe(*group_list) && (mbedtls_ssl_get_ecp_group_id_from_tls_id(*group_list) != MBEDTLS_ECP_DP_NONE)) { propose_group = 1; } #endif /* MBEDTLS_SSL_TLS1_2_SOME_ECC */ if (propose_group) { MBEDTLS_SSL_CHK_BUF_PTR(p, end, 2); MBEDTLS_PUT_UINT16_BE(*group_list, p, 0); p += 2; MBEDTLS_SSL_DEBUG_MSG(3, ("NamedGroup: %s ( %x )", mbedtls_ssl_named_group_to_str(*group_list), *group_list)); } } /* Length of named_group_list */ named_group_list_len = p - named_group_list; if (named_group_list_len == 0) { MBEDTLS_SSL_DEBUG_MSG(1, ("No group available.")); return MBEDTLS_ERR_SSL_INTERNAL_ERROR; } /* Write extension_type */ MBEDTLS_PUT_UINT16_BE(MBEDTLS_TLS_EXT_SUPPORTED_GROUPS, buf, 0); /* Write extension_data_length */ MBEDTLS_PUT_UINT16_BE(named_group_list_len + 2, buf, 2); /* Write length of named_group_list */ MBEDTLS_PUT_UINT16_BE(named_group_list_len, buf, 4); MBEDTLS_SSL_DEBUG_BUF(3, "Supported groups extension", buf + 4, named_group_list_len + 2); *out_len = p - buf; #if defined(MBEDTLS_SSL_PROTO_TLS1_3) mbedtls_ssl_tls13_set_hs_sent_ext_mask( ssl, MBEDTLS_TLS_EXT_SUPPORTED_GROUPS); #endif /* MBEDTLS_SSL_PROTO_TLS1_3 */ return 0; } #endif /* MBEDTLS_SSL_TLS1_2_SOME_ECC || MBEDTLS_SSL_TLS1_3_KEY_EXCHANGE_MODE_SOME_EPHEMERAL_ENABLED */ MBEDTLS_CHECK_RETURN_CRITICAL static int ssl_write_client_hello_cipher_suites( mbedtls_ssl_context *ssl, unsigned char *buf, unsigned char *end, int *tls12_uses_ec, size_t *out_len) { unsigned char *p = buf; const int *ciphersuite_list; unsigned char *cipher_suites; /* Start of the cipher_suites list */ size_t cipher_suites_len; *tls12_uses_ec = 0; *out_len = 0; /* * Ciphersuite list * * This is a list of the symmetric cipher options supported by * the client, specifically the record protection algorithm * ( including secret key length ) and a hash to be used with * HKDF, in descending order of client preference. */ ciphersuite_list = ssl->conf->ciphersuite_list; /* Check there is space for the cipher suite list length (2 bytes). */ MBEDTLS_SSL_CHK_BUF_PTR(p, end, 2); p += 2; /* Write cipher_suites * CipherSuite cipher_suites<2..2^16-2>; */ cipher_suites = p; for (size_t i = 0; ciphersuite_list[i] != 0; i++) { int cipher_suite = ciphersuite_list[i]; const mbedtls_ssl_ciphersuite_t *ciphersuite_info; ciphersuite_info = mbedtls_ssl_ciphersuite_from_id(cipher_suite); if (mbedtls_ssl_validate_ciphersuite(ssl, ciphersuite_info, ssl->handshake->min_tls_version, ssl->tls_version) != 0) { continue; } #if defined(MBEDTLS_SSL_PROTO_TLS1_2) && \ (defined(MBEDTLS_KEY_EXCHANGE_SOME_ECDH_OR_ECDHE_1_2_ENABLED) || \ defined(MBEDTLS_KEY_EXCHANGE_ECDSA_CERT_REQ_ALLOWED_ENABLED) || \ defined(MBEDTLS_KEY_EXCHANGE_ECJPAKE_ENABLED)) *tls12_uses_ec |= mbedtls_ssl_ciphersuite_uses_ec(ciphersuite_info); #endif MBEDTLS_SSL_DEBUG_MSG(3, ("client hello, add ciphersuite: %04x, %s", (unsigned int) cipher_suite, ciphersuite_info->name)); /* Check there is space for the cipher suite identifier (2 bytes). */ MBEDTLS_SSL_CHK_BUF_PTR(p, end, 2); MBEDTLS_PUT_UINT16_BE(cipher_suite, p, 0); p += 2; } /* * Add TLS_EMPTY_RENEGOTIATION_INFO_SCSV */ int renegotiating = 0; #if defined(MBEDTLS_SSL_RENEGOTIATION) renegotiating = (ssl->renego_status != MBEDTLS_SSL_INITIAL_HANDSHAKE); #endif if (!renegotiating) { MBEDTLS_SSL_DEBUG_MSG(3, ("adding EMPTY_RENEGOTIATION_INFO_SCSV")); MBEDTLS_SSL_CHK_BUF_PTR(p, end, 2); MBEDTLS_PUT_UINT16_BE(MBEDTLS_SSL_EMPTY_RENEGOTIATION_INFO, p, 0); p += 2; } /* Write the cipher_suites length in number of bytes */ cipher_suites_len = p - cipher_suites; MBEDTLS_PUT_UINT16_BE(cipher_suites_len, buf, 0); MBEDTLS_SSL_DEBUG_MSG(3, ("client hello, got %" MBEDTLS_PRINTF_SIZET " cipher suites", cipher_suites_len/2)); /* Output the total length of cipher_suites field. */ *out_len = p - buf; return 0; } /* * Structure of the TLS 1.3 ClientHello message: * * struct { * ProtocolVersion legacy_version = 0x0303; // TLS v1.2 * Random random; * opaque legacy_session_id<0..32>; * CipherSuite cipher_suites<2..2^16-2>; * opaque legacy_compression_methods<1..2^8-1>; * Extension extensions<8..2^16-1>; * } ClientHello; * * Structure of the (D)TLS 1.2 ClientHello message: * * struct { * ProtocolVersion client_version; * Random random; * SessionID session_id; * opaque cookie<0..2^8-1>; // DTLS 1.2 ONLY * CipherSuite cipher_suites<2..2^16-2>; * CompressionMethod compression_methods<1..2^8-1>; * select (extensions_present) { * case false: * struct {}; * case true: * Extension extensions<0..2^16-1>; * }; * } ClientHello; */ MBEDTLS_CHECK_RETURN_CRITICAL static int ssl_write_client_hello_body(mbedtls_ssl_context *ssl, unsigned char *buf, unsigned char *end, size_t *out_len, size_t *binders_len) { int ret; mbedtls_ssl_handshake_params *handshake = ssl->handshake; unsigned char *p = buf; unsigned char *p_extensions_len; /* Pointer to extensions length */ size_t output_len; /* Length of buffer used by function */ size_t extensions_len; /* Length of the list of extensions*/ int tls12_uses_ec = 0; *out_len = 0; *binders_len = 0; #if defined(MBEDTLS_SSL_PROTO_TLS1_2) unsigned char propose_tls12 = (handshake->min_tls_version <= MBEDTLS_SSL_VERSION_TLS1_2) && (MBEDTLS_SSL_VERSION_TLS1_2 <= ssl->tls_version); #endif #if defined(MBEDTLS_SSL_PROTO_TLS1_3) unsigned char propose_tls13 = (handshake->min_tls_version <= MBEDTLS_SSL_VERSION_TLS1_3) && (MBEDTLS_SSL_VERSION_TLS1_3 <= ssl->tls_version); #endif /* * Write client_version (TLS 1.2) or legacy_version (TLS 1.3) * * In all cases this is the TLS 1.2 version. */ MBEDTLS_SSL_CHK_BUF_PTR(p, end, 2); mbedtls_ssl_write_version(p, ssl->conf->transport, MBEDTLS_SSL_VERSION_TLS1_2); p += 2; /* ... * Random random; * ... * * The random bytes have been prepared by ssl_prepare_client_hello() into * the handshake->randbytes buffer and are copied here into the output * buffer. */ MBEDTLS_SSL_CHK_BUF_PTR(p, end, MBEDTLS_CLIENT_HELLO_RANDOM_LEN); memcpy(p, handshake->randbytes, MBEDTLS_CLIENT_HELLO_RANDOM_LEN); MBEDTLS_SSL_DEBUG_BUF(3, "client hello, random bytes", p, MBEDTLS_CLIENT_HELLO_RANDOM_LEN); p += MBEDTLS_CLIENT_HELLO_RANDOM_LEN; /* TLS 1.2: * ... * SessionID session_id; * ... * with * opaque SessionID<0..32>; * * TLS 1.3: * ... * opaque legacy_session_id<0..32>; * ... * * The (legacy) session identifier bytes have been prepared by * ssl_prepare_client_hello() into the ssl->session_negotiate->id buffer * and are copied here into the output buffer. */ MBEDTLS_SSL_CHK_BUF_PTR(p, end, ssl->session_negotiate->id_len + 1); *p++ = (unsigned char) ssl->session_negotiate->id_len; memcpy(p, ssl->session_negotiate->id, ssl->session_negotiate->id_len); p += ssl->session_negotiate->id_len; MBEDTLS_SSL_DEBUG_BUF(3, "session id", ssl->session_negotiate->id, ssl->session_negotiate->id_len); /* DTLS 1.2 ONLY * ... * opaque cookie<0..2^8-1>; * ... */ #if defined(MBEDTLS_SSL_PROTO_TLS1_2) && defined(MBEDTLS_SSL_PROTO_DTLS) if (ssl->conf->transport == MBEDTLS_SSL_TRANSPORT_DATAGRAM) { #if !defined(MBEDTLS_SSL_PROTO_TLS1_3) uint8_t cookie_len = 0; #else uint16_t cookie_len = 0; #endif /* !MBEDTLS_SSL_PROTO_TLS1_3 */ if (handshake->cookie != NULL) { MBEDTLS_SSL_DEBUG_BUF(3, "client hello, cookie", handshake->cookie, handshake->cookie_len); cookie_len = handshake->cookie_len; } MBEDTLS_SSL_CHK_BUF_PTR(p, end, cookie_len + 1); *p++ = (unsigned char) cookie_len; if (cookie_len > 0) { memcpy(p, handshake->cookie, cookie_len); p += cookie_len; } } #endif /* MBEDTLS_SSL_PROTO_TLS1_2 && MBEDTLS_SSL_PROTO_DTLS */ /* Write cipher_suites */ ret = ssl_write_client_hello_cipher_suites(ssl, p, end, &tls12_uses_ec, &output_len); if (ret != 0) { return ret; } p += output_len; /* Write legacy_compression_methods (TLS 1.3) or * compression_methods (TLS 1.2) * * For every TLS 1.3 ClientHello, this vector MUST contain exactly * one byte set to zero, which corresponds to the 'null' compression * method in prior versions of TLS. * * For TLS 1.2 ClientHello, for security reasons we do not support * compression anymore, thus also just the 'null' compression method. */ MBEDTLS_SSL_CHK_BUF_PTR(p, end, 2); *p++ = 1; *p++ = MBEDTLS_SSL_COMPRESS_NULL; /* Write extensions */ #if defined(MBEDTLS_SSL_PROTO_TLS1_3) /* Keeping track of the included extensions */ handshake->sent_extensions = MBEDTLS_SSL_EXT_MASK_NONE; #endif /* First write extensions, then the total length */ MBEDTLS_SSL_CHK_BUF_PTR(p, end, 2); p_extensions_len = p; p += 2; #if defined(MBEDTLS_SSL_SERVER_NAME_INDICATION) /* Write server name extension */ ret = ssl_write_hostname_ext(ssl, p, end, &output_len); if (ret != 0) { return ret; } p += output_len; #endif /* MBEDTLS_SSL_SERVER_NAME_INDICATION */ #if defined(MBEDTLS_SSL_ALPN) ret = ssl_write_alpn_ext(ssl, p, end, &output_len); if (ret != 0) { return ret; } p += output_len; #endif /* MBEDTLS_SSL_ALPN */ #if defined(MBEDTLS_SSL_PROTO_TLS1_3) if (propose_tls13) { ret = mbedtls_ssl_tls13_write_client_hello_exts(ssl, p, end, &output_len); if (ret != 0) { return ret; } p += output_len; } #endif #if defined(MBEDTLS_SSL_TLS1_2_SOME_ECC) || \ defined(MBEDTLS_SSL_TLS1_3_KEY_EXCHANGE_MODE_SOME_EPHEMERAL_ENABLED) { int ssl_write_supported_groups_ext_flags = 0; #if defined(MBEDTLS_SSL_TLS1_3_KEY_EXCHANGE_MODE_SOME_EPHEMERAL_ENABLED) if (propose_tls13 && mbedtls_ssl_conf_tls13_some_ephemeral_enabled(ssl)) { ssl_write_supported_groups_ext_flags |= SSL_WRITE_SUPPORTED_GROUPS_EXT_TLS1_3_FLAG; } #endif #if defined(MBEDTLS_SSL_TLS1_2_SOME_ECC) if (propose_tls12 && tls12_uses_ec) { ssl_write_supported_groups_ext_flags |= SSL_WRITE_SUPPORTED_GROUPS_EXT_TLS1_2_FLAG; } #endif if (ssl_write_supported_groups_ext_flags != 0) { ret = ssl_write_supported_groups_ext(ssl, p, end, ssl_write_supported_groups_ext_flags, &output_len); if (ret != 0) { return ret; } p += output_len; } } #endif /* MBEDTLS_SSL_TLS1_2_SOME_ECC || MBEDTLS_SSL_TLS1_3_KEY_EXCHANGE_MODE_SOME_EPHEMERAL_ENABLED */ #if defined(MBEDTLS_SSL_HANDSHAKE_WITH_CERT_ENABLED) int write_sig_alg_ext = 0; #if defined(MBEDTLS_SSL_PROTO_TLS1_3) write_sig_alg_ext = write_sig_alg_ext || (propose_tls13 && mbedtls_ssl_conf_tls13_ephemeral_enabled(ssl)); #endif #if defined(MBEDTLS_SSL_PROTO_TLS1_2) write_sig_alg_ext = write_sig_alg_ext || propose_tls12; #endif if (write_sig_alg_ext) { ret = mbedtls_ssl_write_sig_alg_ext(ssl, p, end, &output_len); if (ret != 0) { return ret; } p += output_len; } #endif /* MBEDTLS_SSL_HANDSHAKE_WITH_CERT_ENABLED */ #if defined(MBEDTLS_SSL_PROTO_TLS1_2) if (propose_tls12) { ret = mbedtls_ssl_tls12_write_client_hello_exts(ssl, p, end, tls12_uses_ec, &output_len); if (ret != 0) { return ret; } p += output_len; } #endif /* MBEDTLS_SSL_PROTO_TLS1_2 */ #if defined(MBEDTLS_SSL_TLS1_3_KEY_EXCHANGE_MODE_SOME_PSK_ENABLED) /* The "pre_shared_key" extension (RFC 8446 Section 4.2.11) * MUST be the last extension in the ClientHello. */ if (propose_tls13 && mbedtls_ssl_conf_tls13_some_psk_enabled(ssl)) { ret = mbedtls_ssl_tls13_write_identities_of_pre_shared_key_ext( ssl, p, end, &output_len, binders_len); if (ret != 0) { return ret; } p += output_len; } #endif /* MBEDTLS_SSL_TLS1_3_KEY_EXCHANGE_MODE_SOME_PSK_ENABLED */ /* Write the length of the list of extensions. */ extensions_len = p - p_extensions_len - 2; if (extensions_len == 0) { p = p_extensions_len; } else { MBEDTLS_PUT_UINT16_BE(extensions_len, p_extensions_len, 0); MBEDTLS_SSL_DEBUG_MSG(3, ("client hello, total extension length: %" \ MBEDTLS_PRINTF_SIZET, extensions_len)); MBEDTLS_SSL_DEBUG_BUF(3, "client hello extensions", p_extensions_len, extensions_len); } #if defined(MBEDTLS_SSL_PROTO_TLS1_3) MBEDTLS_SSL_PRINT_EXTS( 3, MBEDTLS_SSL_HS_CLIENT_HELLO, handshake->sent_extensions); #endif *out_len = p - buf; return 0; } MBEDTLS_CHECK_RETURN_CRITICAL static int ssl_generate_random(mbedtls_ssl_context *ssl) { int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; unsigned char *randbytes = ssl->handshake->randbytes; size_t gmt_unix_time_len = 0; /* * Generate the random bytes * * TLS 1.2 case: * struct { * uint32 gmt_unix_time; * opaque random_bytes[28]; * } Random; * * TLS 1.3 case: * opaque Random[32]; */ if (ssl->tls_version == MBEDTLS_SSL_VERSION_TLS1_2) { #if defined(MBEDTLS_HAVE_TIME) mbedtls_time_t gmt_unix_time = mbedtls_time(NULL); MBEDTLS_PUT_UINT32_BE(gmt_unix_time, randbytes, 0); gmt_unix_time_len = 4; MBEDTLS_SSL_DEBUG_MSG(3, ("client hello, current time: %" MBEDTLS_PRINTF_LONGLONG, (long long) gmt_unix_time)); #endif /* MBEDTLS_HAVE_TIME */ } ret = ssl->conf->f_rng(ssl->conf->p_rng, randbytes + gmt_unix_time_len, MBEDTLS_CLIENT_HELLO_RANDOM_LEN - gmt_unix_time_len); return ret; } MBEDTLS_CHECK_RETURN_CRITICAL static int ssl_prepare_client_hello(mbedtls_ssl_context *ssl) { int ret; size_t session_id_len; mbedtls_ssl_session *session_negotiate = ssl->session_negotiate; if (session_negotiate == NULL) { return MBEDTLS_ERR_SSL_INTERNAL_ERROR; } #if defined(MBEDTLS_SSL_PROTO_TLS1_3) && \ defined(MBEDTLS_SSL_SESSION_TICKETS) && \ defined(MBEDTLS_HAVE_TIME) /* Check if a tls13 ticket has been configured. */ if (ssl->handshake->resume != 0 && session_negotiate->tls_version == MBEDTLS_SSL_VERSION_TLS1_3 && session_negotiate->ticket != NULL) { mbedtls_time_t now = mbedtls_time(NULL); uint64_t age = (uint64_t) (now - session_negotiate->ticket_received); if (session_negotiate->ticket_received > now || age > session_negotiate->ticket_lifetime) { /* Without valid ticket, disable session resumption.*/ MBEDTLS_SSL_DEBUG_MSG( 3, ("Ticket expired, disable session resumption")); ssl->handshake->resume = 0; } } #endif /* MBEDTLS_SSL_PROTO_TLS1_3 && MBEDTLS_SSL_SESSION_TICKETS && MBEDTLS_HAVE_TIME */ if (ssl->conf->f_rng == NULL) { MBEDTLS_SSL_DEBUG_MSG(1, ("no RNG provided")); return MBEDTLS_ERR_SSL_NO_RNG; } /* Bet on the highest configured version if we are not in a TLS 1.2 * renegotiation or session resumption. */ #if defined(MBEDTLS_SSL_RENEGOTIATION) if (ssl->renego_status != MBEDTLS_SSL_INITIAL_HANDSHAKE) { ssl->handshake->min_tls_version = ssl->tls_version; } else #endif { if (ssl->handshake->resume) { ssl->tls_version = session_negotiate->tls_version; ssl->handshake->min_tls_version = ssl->tls_version; } else { ssl->handshake->min_tls_version = ssl->conf->min_tls_version; } } /* * Generate the random bytes, except when responding to a verify request * where we MUST reuse the previously generated random bytes * (RFC 6347 4.2.1). */ #if defined(MBEDTLS_SSL_PROTO_DTLS) if ((ssl->conf->transport != MBEDTLS_SSL_TRANSPORT_DATAGRAM) || (ssl->handshake->cookie == NULL)) #endif { ret = ssl_generate_random(ssl); if (ret != 0) { MBEDTLS_SSL_DEBUG_RET(1, "Random bytes generation failed", ret); return ret; } } /* * Prepare session identifier. At that point, the length of the session * identifier in the SSL context `ssl->session_negotiate->id_len` is equal * to zero, except in the case of a TLS 1.2 session renegotiation or * session resumption. */ session_id_len = session_negotiate->id_len; #if defined(MBEDTLS_SSL_PROTO_TLS1_2) if (ssl->tls_version == MBEDTLS_SSL_VERSION_TLS1_2) { if (session_id_len < 16 || session_id_len > 32 || #if defined(MBEDTLS_SSL_RENEGOTIATION) ssl->renego_status != MBEDTLS_SSL_INITIAL_HANDSHAKE || #endif ssl->handshake->resume == 0) { session_id_len = 0; } #if defined(MBEDTLS_SSL_SESSION_TICKETS) /* * RFC 5077 section 3.4: "When presenting a ticket, the client MAY * generate and include a Session ID in the TLS ClientHello." */ int renegotiating = 0; #if defined(MBEDTLS_SSL_RENEGOTIATION) if (ssl->renego_status != MBEDTLS_SSL_INITIAL_HANDSHAKE) { renegotiating = 1; } #endif if (!renegotiating) { if ((session_negotiate->ticket != NULL) && (session_negotiate->ticket_len != 0)) { session_id_len = 32; } } #endif /* MBEDTLS_SSL_SESSION_TICKETS */ } #endif /* MBEDTLS_SSL_PROTO_TLS1_2 */ #if defined(MBEDTLS_SSL_TLS1_3_COMPATIBILITY_MODE) if (ssl->tls_version == MBEDTLS_SSL_VERSION_TLS1_3) { /* * Create a legacy session identifier for the purpose of middlebox * compatibility only if one has not been created already, which is * the case if we are here for the TLS 1.3 second ClientHello. * * Versions of TLS before TLS 1.3 supported a "session resumption" * feature which has been merged with pre-shared keys in TLS 1.3 * version. A client which has a cached session ID set by a pre-TLS 1.3 * server SHOULD set this field to that value. In compatibility mode, * this field MUST be non-empty, so a client not offering a pre-TLS 1.3 * session MUST generate a new 32-byte value. This value need not be * random but SHOULD be unpredictable to avoid implementations fixating * on a specific value (also known as ossification). Otherwise, it MUST * be set as a zero-length vector ( i.e., a zero-valued single byte * length field ). */ session_id_len = 32; } #endif /* MBEDTLS_SSL_TLS1_3_COMPATIBILITY_MODE */ if (session_id_len != session_negotiate->id_len) { session_negotiate->id_len = session_id_len; if (session_id_len > 0) { ret = ssl->conf->f_rng(ssl->conf->p_rng, session_negotiate->id, session_id_len); if (ret != 0) { MBEDTLS_SSL_DEBUG_RET(1, "creating session id failed", ret); return ret; } } } #if defined(MBEDTLS_SSL_PROTO_TLS1_3) && \ defined(MBEDTLS_SSL_SESSION_TICKETS) && \ defined(MBEDTLS_SSL_SERVER_NAME_INDICATION) if (ssl->tls_version == MBEDTLS_SSL_VERSION_TLS1_3 && ssl->handshake->resume) { int hostname_mismatch = ssl->hostname != NULL || session_negotiate->hostname != NULL; if (ssl->hostname != NULL && session_negotiate->hostname != NULL) { hostname_mismatch = strcmp( ssl->hostname, session_negotiate->hostname) != 0; } if (hostname_mismatch) { MBEDTLS_SSL_DEBUG_MSG( 1, ("Hostname mismatch the session ticket, " "disable session resumption.")); return MBEDTLS_ERR_SSL_BAD_INPUT_DATA; } } else { return mbedtls_ssl_session_set_hostname(session_negotiate, ssl->hostname); } #endif /* MBEDTLS_SSL_PROTO_TLS1_3 && MBEDTLS_SSL_SESSION_TICKETS && MBEDTLS_SSL_SERVER_NAME_INDICATION */ return 0; } /* * Write ClientHello handshake message. * Handler for MBEDTLS_SSL_CLIENT_HELLO */ int mbedtls_ssl_write_client_hello(mbedtls_ssl_context *ssl) { int ret = 0; unsigned char *buf; size_t buf_len, msg_len, binders_len; MBEDTLS_SSL_DEBUG_MSG(2, ("=> write client hello")); MBEDTLS_SSL_PROC_CHK(ssl_prepare_client_hello(ssl)); MBEDTLS_SSL_PROC_CHK(mbedtls_ssl_start_handshake_msg( ssl, MBEDTLS_SSL_HS_CLIENT_HELLO, &buf, &buf_len)); MBEDTLS_SSL_PROC_CHK(ssl_write_client_hello_body(ssl, buf, buf + buf_len, &msg_len, &binders_len)); #if defined(MBEDTLS_SSL_PROTO_TLS1_2) && defined(MBEDTLS_SSL_PROTO_DTLS) if (ssl->conf->transport == MBEDTLS_SSL_TRANSPORT_DATAGRAM) { ssl->out_msglen = msg_len + 4; mbedtls_ssl_send_flight_completed(ssl); /* * The two functions below may try to send data on the network and * can return with the MBEDTLS_ERR_SSL_WANT_READ error code when they * fail to do so and the transmission has to be retried later. In that * case as in fatal error cases, we return immediately. But we must have * set the handshake state to the next state at that point to ensure * that we will not write and send again a ClientHello when we * eventually succeed in sending the pending data. */ mbedtls_ssl_handshake_set_state(ssl, MBEDTLS_SSL_SERVER_HELLO); if ((ret = mbedtls_ssl_write_handshake_msg(ssl)) != 0) { MBEDTLS_SSL_DEBUG_RET(1, "mbedtls_ssl_write_handshake_msg", ret); return ret; } if ((ret = mbedtls_ssl_flight_transmit(ssl)) != 0) { MBEDTLS_SSL_DEBUG_RET(1, "mbedtls_ssl_flight_transmit", ret); return ret; } } else #endif /* MBEDTLS_SSL_PROTO_TLS1_2 && MBEDTLS_SSL_PROTO_DTLS */ { ret = mbedtls_ssl_add_hs_hdr_to_checksum(ssl, MBEDTLS_SSL_HS_CLIENT_HELLO, msg_len); if (ret != 0) { MBEDTLS_SSL_DEBUG_RET(1, "mbedtls_ssl_add_hs_hdr_to_checksum", ret); return ret; } ret = ssl->handshake->update_checksum(ssl, buf, msg_len - binders_len); if (ret != 0) { MBEDTLS_SSL_DEBUG_RET(1, "update_checksum", ret); return ret; } #if defined(MBEDTLS_SSL_TLS1_3_KEY_EXCHANGE_MODE_SOME_PSK_ENABLED) if (binders_len > 0) { MBEDTLS_SSL_PROC_CHK( mbedtls_ssl_tls13_write_binders_of_pre_shared_key_ext( ssl, buf + msg_len - binders_len, buf + msg_len)); ret = ssl->handshake->update_checksum(ssl, buf + msg_len - binders_len, binders_len); if (ret != 0) { MBEDTLS_SSL_DEBUG_RET(1, "update_checksum", ret); return ret; } } #endif /* MBEDTLS_SSL_TLS1_3_KEY_EXCHANGE_MODE_SOME_PSK_ENABLED */ MBEDTLS_SSL_PROC_CHK(mbedtls_ssl_finish_handshake_msg(ssl, buf_len, msg_len)); /* * Set next state. Note that if TLS 1.3 is proposed, this may be * overwritten by mbedtls_ssl_tls13_finalize_client_hello(). */ mbedtls_ssl_handshake_set_state(ssl, MBEDTLS_SSL_SERVER_HELLO); #if defined(MBEDTLS_SSL_PROTO_TLS1_3) if (ssl->handshake->min_tls_version <= MBEDTLS_SSL_VERSION_TLS1_3 && MBEDTLS_SSL_VERSION_TLS1_3 <= ssl->tls_version) { ret = mbedtls_ssl_tls13_finalize_client_hello(ssl); } #endif } cleanup: MBEDTLS_SSL_DEBUG_MSG(2, ("<= write client hello")); return ret; } #endif /* MBEDTLS_SSL_PROTO_TLS1_3 || MBEDTLS_SSL_PROTO_TLS1_2 */ #endif /* MBEDTLS_SSL_CLI_C */