/* * TLS 1.3 server-side functions * * Copyright The Mbed TLS Contributors * SPDX-License-Identifier: Apache-2.0 * * Licensed under the Apache License, Version 2.0 (the "License"); you may * not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ #include "common.h" #if defined(MBEDTLS_SSL_SRV_C) && defined(MBEDTLS_SSL_PROTO_TLS1_3) #include "mbedtls/debug.h" #include "ssl_misc.h" #include "ssl_tls13_keys.h" #include "ssl_debug_helpers.h" #include #if defined(MBEDTLS_ECP_C) #include "mbedtls/ecp.h" #include "ecp_internal.h" #endif /* MBEDTLS_ECP_C */ #if defined(MBEDTLS_PLATFORM_C) #include "mbedtls/platform.h" #else #include #define mbedtls_calloc calloc #define mbedtls_free free #endif /* MBEDTLS_PLATFORM_C */ /* From RFC 8446: * struct { * select (Handshake.msg_type) { * case client_hello: * ProtocolVersion versions<2..254>; * case server_hello: // and HelloRetryRequest * ProtocolVersion selected_version; * }; * } SupportedVersions; */ static int ssl_tls13_parse_supported_versions_ext( mbedtls_ssl_context *ssl, const unsigned char *buf, const unsigned char *end ) { size_t list_len; int tls13_supported = 0; int major_ver, minor_ver; const unsigned char *p = buf; const unsigned char *version_end; MBEDTLS_SSL_CHK_BUF_READ_PTR( p, end, 1 ); list_len = p[0]; p += 1; MBEDTLS_SSL_CHK_BUF_READ_PTR( p, end, list_len ); if( list_len % 2 != 0 ) { MBEDTLS_SSL_DEBUG_MSG( 1, ( "Invalid supported version list length %" MBEDTLS_PRINTF_SIZET, list_len ) ); return( MBEDTLS_ERR_SSL_DECODE_ERROR ); } version_end = p + list_len; while( p < version_end ) { mbedtls_ssl_read_version( &major_ver, &minor_ver, ssl->conf->transport, p ); /* In this implementation we only support TLS 1.3 and DTLS 1.3. */ if( major_ver == MBEDTLS_SSL_MAJOR_VERSION_3 && minor_ver == MBEDTLS_SSL_MINOR_VERSION_4 ) { tls13_supported = 1; break; } p += 2; } if( tls13_supported == 0 ) { /* When we support runtime negotiation of TLS 1.2 and TLS 1.3, we need * a graceful fallback to TLS 1.2 in this case. */ MBEDTLS_SSL_DEBUG_MSG( 1, ( "TLS 1.3 is not supported by the client" ) ); MBEDTLS_SSL_PEND_FATAL_ALERT( MBEDTLS_SSL_ALERT_MSG_PROTOCOL_VERSION, MBEDTLS_ERR_SSL_BAD_PROTOCOL_VERSION ); return( MBEDTLS_ERR_SSL_BAD_PROTOCOL_VERSION ); } MBEDTLS_SSL_DEBUG_MSG( 1, ( "Negotiated version. Supported is [%d:%d]", major_ver, minor_ver ) ); ssl->major_ver = major_ver; ssl->minor_ver = minor_ver; ssl->handshake->max_major_ver = ssl->major_ver; ssl->handshake->max_minor_ver = ssl->minor_ver; return( 0 ); } #if ( defined(MBEDTLS_ECDH_C) || defined(MBEDTLS_ECDSA_C) ) /* This function parses the TLS 1.3 supported_groups extension and * stores the received groups in ssl->handshake->curves. * * From RFC 8446: * enum { * ... (0xFFFF) * } NamedGroup; * struct { * NamedGroup named_group_list<2..2^16-1>; * } NamedGroupList; */ static int mbedtls_ssl_tls13_parse_supported_groups_ext( mbedtls_ssl_context *ssl, const unsigned char *buf, const unsigned char *end ) { size_t list_size, our_size; const unsigned char *p = buf; const mbedtls_ecp_curve_info *curve_info, **curves; const unsigned char *extentions_end; MBEDTLS_SSL_DEBUG_BUF( 3, "supported_groups extension", p, end - buf ); list_size = MBEDTLS_GET_UINT16_BE( p, 0 ); p += 2; MBEDTLS_SSL_CHK_BUF_READ_PTR( p, end, list_size ); if( list_size % 2 != 0 ) return( MBEDTLS_ERR_SSL_DECODE_ERROR ); /* At the moment, this can happen when receiving a second * ClientHello after an HRR. We should properly reset the * state upon receiving an HRR, in which case we should * not observe handshake->curves already being allocated. */ if( ssl->handshake->curves != NULL ) { mbedtls_free( ssl->handshake->curves ); ssl->handshake->curves = NULL; } /* Don't allow our peer to make us allocate too much memory, * and leave room for a final 0 */ our_size = list_size / 2 + 1; if( our_size > MBEDTLS_ECP_DP_MAX ) our_size = MBEDTLS_ECP_DP_MAX; if( ( curves = mbedtls_calloc( our_size, sizeof( *curves ) ) ) == NULL ) return( MBEDTLS_ERR_SSL_ALLOC_FAILED ); extentions_end = p + list_size; ssl->handshake->curves = curves; while ( p < extentions_end && our_size > 1 ) { uint16_t tls_grp_id = MBEDTLS_GET_UINT16_BE( p, 0 ); curve_info = mbedtls_ecp_curve_info_from_tls_id( tls_grp_id ); /* mbedtls_ecp_curve_info_from_tls_id() uses the mbedtls_ecp_curve_info * data structure (defined in ecp.c), which only includes the list of * curves implemented. Hence, we only add curves that are also supported * and implemented by the server. */ if( curve_info != NULL ) { *curves++ = curve_info; MBEDTLS_SSL_DEBUG_MSG( 4, ( "supported curve: %s", curve_info->name ) ); our_size--; } p += 2; } return( 0 ); } #endif /* MBEDTLS_ECDH_C || ( MBEDTLS_ECDSA_C */ #if ( defined(MBEDTLS_ECDH_C) || defined(MBEDTLS_ECDSA_C) ) /* * ssl_tls13_parse_key_shares_ext() verifies whether the information in the * extension is correct and stores the provided key shares. Whether this is an * acceptable key share depends on the selected ciphersuite. * * Possible return values are: * - 0: Successful processing of the client provided key share extension. * - MBEDTLS_ERR_SSL_HRR_REQUIRED: The key share provided by the client * does not match a group supported by the server. A HelloRetryRequest will * be needed. * - Another negative return value for fatal errors. */ static int ssl_tls13_parse_key_shares_ext( mbedtls_ssl_context *ssl, const unsigned char *buf, const unsigned char *end ) { int ret = 0; unsigned char const *p = buf; unsigned char const *extentions_end; size_t total_ext_len, cur_share_len; int match_found = 0; /* From RFC 8446: * * struct { * KeyShareEntry client_shares<0..2^16-1>; * } KeyShareClientHello; * */ /* Read total legnth of KeyShareClientHello */ MBEDTLS_SSL_CHK_BUF_READ_PTR( p, end, 2 ); total_ext_len = MBEDTLS_GET_UINT16_BE( p, 0 ); p += 2; MBEDTLS_SSL_CHK_BUF_READ_PTR( p, end, total_ext_len ); ssl->handshake->offered_group_id = 0; extentions_end = p + total_ext_len; /* We try to find a suitable key share entry and copy it to the * handshake context. Later, we have to find out whether we can do * something with the provided key share or whether we have to * dismiss it and send a HelloRetryRequest message. */ for( ; p < extentions_end; p += cur_share_len ) { uint16_t their_group; mbedtls_ecp_group_id their_curve; mbedtls_ecp_curve_info const *their_curve_info; unsigned char const *end_of_share; /* * struct { * NamedGroup group; * opaque key_exchange<1..2^16-1>; * } KeyShareEntry; */ MBEDTLS_SSL_CHK_BUF_READ_PTR( p, extentions_end, 4 ); their_group = MBEDTLS_GET_UINT16_BE( p, 0 ); p += 2; cur_share_len = MBEDTLS_GET_UINT16_BE( p, 0 ); p += 2; end_of_share = p + cur_share_len; /* Continue parsing even if we have already found a match, * for input validation purposes. */ if( match_found == 1 ) continue; /* * NamedGroup matching * * For now, we only support ECDHE groups, but e.g. * PQC KEMs will need to be added at a later stage. */ /* Type 1: ECDHE shares * * - Check if we recognize the group * - Check if it's supported */ their_curve = mbedtls_ecp_named_group_to_id( their_group ); if( mbedtls_ssl_check_curve( ssl, their_curve ) != 0 ) continue; /* Skip if we no match succeeded. */ if( their_curve == MBEDTLS_ECP_DP_NONE ) { MBEDTLS_SSL_DEBUG_MSG( 4, ( "Unrecognized NamedGroup %u", (unsigned) their_group ) ); continue; } match_found = 1; /* KeyShare parsing * * Once we add more key share types, this needs to be a switch * over the (type of) the named curve */ /* Type 1: ECDHE shares * * - Setup ECDHE context * - Import client's public key * - Apply further curve checks */ their_curve_info = mbedtls_ecp_curve_info_from_grp_id( their_curve ); MBEDTLS_SSL_DEBUG_MSG( 2, ( "ECDH curve: %s", their_curve_info->name ) ); ret = mbedtls_ecdh_setup( &ssl->handshake->ecdh_ctx, their_curve ); if( ret != 0 ) { MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ecdh_setup()", ret ); return( ret ); } ret = mbedtls_ecdh_import_public_raw( &ssl->handshake->ecdh_ctx, p, end_of_share ); if( ret != 0 ) { MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ecdh_import_public_raw()", ret ); return( ret ); } ssl->handshake->offered_group_id = their_group; } if( match_found == 0 ) { MBEDTLS_SSL_DEBUG_MSG( 1, ( "no matching key share" ) ); return( MBEDTLS_ERR_SSL_HRR_REQUIRED ); } return( 0 ); } #endif /* MBEDTLS_ECDH_C || MBEDTLS_ECDSA_C */ #if defined(MBEDTLS_SSL_COOKIE_C) static int ssl_tls13_parse_cookie_ext( mbedtls_ssl_context *ssl, const unsigned char *buf, const unsigned char *end ) { int ret = 0; size_t cookie_len; unsigned char const *p = buf; mbedtls_ssl_handshake_params *handshake = ssl->handshake; MBEDTLS_SSL_DEBUG_MSG( 3, ( "parse cookie extension" ) ); if( ssl->conf->f_cookie_check != NULL ) { MBEDTLS_SSL_CHK_BUF_READ_PTR( p, end, 2 ); cookie_len = MBEDTLS_GET_UINT16_BE( p, 0 ); p += 2; MBEDTLS_SSL_CHK_BUF_READ_PTR( p, end, cookie_len ); MBEDTLS_SSL_DEBUG_BUF( 3, "Received cookie", p, cookie_len ); if( ssl->conf->f_cookie_check( ssl->conf->p_cookie, p, cookie_len, ssl->cli_id, ssl->cli_id_len ) != 0 ) { MBEDTLS_SSL_DEBUG_MSG( 2, ( "cookie verification failed" ) ); handshake->verify_cookie_len = 1; ret = MBEDTLS_ERR_SSL_HRR_REQUIRED; } else { MBEDTLS_SSL_DEBUG_MSG( 2, ( "cookie verification passed" ) ); handshake->verify_cookie_len = 0; } } else { MBEDTLS_SSL_DEBUG_MSG( 2, ( "cookie verification skipped" ) ); } return( ret ); } #endif /* MBEDTLS_SSL_COOKIE_C */ /* * * STATE HANDLING: ClientHello * * There are three possible classes of outcomes when parsing the CH: * * 1) The CH was well-formed and matched the server's configuration. * * In this case, the server progresses to sending its ServerHello. * * 2) The CH was well-formed but didn't match the server's configuration. * * For example, the client might not have offered a key share which * the server supports, or the server might require a cookie. * * In this case, the server sends a HelloRetryRequest. * * 3) The CH was ill-formed * * In this case, we abort the handshake. * */ /* * Overview */ /* Main entry point from the state machine; orchestrates the otherfunctions. */ static int ssl_client_hello_process( mbedtls_ssl_context *ssl ); static int ssl_client_hello_parse( mbedtls_ssl_context *ssl, const unsigned char *buf, const unsigned char *end ); /* Update the handshake state machine */ static int ssl_client_hello_postprocess( mbedtls_ssl_context *ssl, int hrr_required ); /* * Implementation */ #define SSL_CLIENT_HELLO_OK 0 #define SSL_CLIENT_HELLO_HRR_REQUIRED 1 static int ssl_client_hello_process( mbedtls_ssl_context *ssl ) { int ret = 0; int hrr_required = SSL_CLIENT_HELLO_OK; unsigned char* buf = NULL; size_t buflen = 0; MBEDTLS_SSL_DEBUG_MSG( 2, ( "=> parse client hello" ) ); ssl->major_ver = MBEDTLS_SSL_MAJOR_VERSION_3; MBEDTLS_SSL_PROC_CHK( mbedtls_ssl_tls13_fetch_handshake_msg( ssl, MBEDTLS_SSL_HS_CLIENT_HELLO, &buf, &buflen ) ); mbedtls_ssl_tls13_add_hs_hdr_to_checksum( ssl, MBEDTLS_SSL_HS_CLIENT_HELLO, buflen ); MBEDTLS_SSL_PROC_CHK_NEG( ssl_client_hello_parse( ssl, buf, buf + buflen ) ); hrr_required = ret; MBEDTLS_SSL_DEBUG_MSG( 1, ( "postprocess" ) ); MBEDTLS_SSL_PROC_CHK( ssl_client_hello_postprocess( ssl, hrr_required ) ); cleanup: MBEDTLS_SSL_DEBUG_MSG( 2, ( "<= parse client hello" ) ); return( ret ); } static void ssl_debug_print_client_hello_exts( mbedtls_ssl_context *ssl ) { ((void) ssl); MBEDTLS_SSL_DEBUG_MSG( 3, ( "Supported Extensions:" ) ); MBEDTLS_SSL_DEBUG_MSG( 3, ( "- KEY_SHARE_EXTENSION ( %s )", ( ( ssl->handshake->extensions_present & MBEDTLS_SSL_EXT_KEY_SHARE ) > 0 ) ? "TRUE" : "FALSE" ) ); MBEDTLS_SSL_DEBUG_MSG( 3, ( "- PSK_KEY_EXCHANGE_MODES_EXTENSION ( %s )", ( ( ssl->handshake->extensions_present & MBEDTLS_SSL_EXT_PSK_KEY_EXCHANGE_MODES ) > 0 ) ? "TRUE" : "FALSE" ) ); MBEDTLS_SSL_DEBUG_MSG( 3, ( "- PRE_SHARED_KEY_EXTENSION ( %s )", ( ( ssl->handshake->extensions_present & MBEDTLS_SSL_EXT_PRE_SHARED_KEY ) > 0 ) ? "TRUE" : "FALSE" ) ); MBEDTLS_SSL_DEBUG_MSG( 3, ( "- SIGNATURE_ALGORITHM_EXTENSION ( %s )", ( ( ssl->handshake->extensions_present & MBEDTLS_SSL_EXT_SIG_ALG ) > 0 ) ? "TRUE" : "FALSE" ) ); MBEDTLS_SSL_DEBUG_MSG( 3, ( "- SUPPORTED_GROUPS_EXTENSION ( %s )", ( ( ssl->handshake->extensions_present & MBEDTLS_SSL_EXT_SUPPORTED_GROUPS ) >0 ) ? "TRUE" : "FALSE" ) ); MBEDTLS_SSL_DEBUG_MSG( 3, ( "- SUPPORTED_VERSION_EXTENSION ( %s )", ( ( ssl->handshake->extensions_present & MBEDTLS_SSL_EXT_SUPPORTED_VERSIONS ) > 0 ) ? "TRUE" : "FALSE" ) ); #if defined ( MBEDTLS_SSL_SERVER_NAME_INDICATION ) MBEDTLS_SSL_DEBUG_MSG( 3, ( "- SERVERNAME_EXTENSION ( %s )", ( ( ssl->handshake->extensions_present & MBEDTLS_SSL_EXT_SERVERNAME ) > 0 ) ? "TRUE" : "FALSE" ) ); #endif /* MBEDTLS_SSL_SERVER_NAME_INDICATION */ #if defined ( MBEDTLS_SSL_COOKIE_C ) MBEDTLS_SSL_DEBUG_MSG( 3, ( "- COOKIE_EXTENSION ( %s )", ( ( ssl->handshake->extensions_present & MBEDTLS_SSL_EXT_COOKIE ) >0 ) ? "TRUE" : "FALSE" ) ); #endif /* MBEDTLS_SSL_COOKIE_C */ } static int ssl_client_hello_has_exts( mbedtls_ssl_context *ssl, int ext_id_mask ) { int masked = ssl->handshake->extensions_present & ext_id_mask; return( masked == ext_id_mask ); } static int ssl_client_hello_has_cert_extensions( mbedtls_ssl_context *ssl ) { return( ssl_client_hello_has_exts( ssl, MBEDTLS_SSL_EXT_SUPPORTED_GROUPS | MBEDTLS_SSL_EXT_KEY_SHARE | MBEDTLS_SSL_EXT_SIG_ALG ) ); } static int ssl_check_certificate_key_exchange( mbedtls_ssl_context *ssl ) { if( !mbedtls_ssl_conf_tls13_ephemeral_enabled( ssl ) ) return( 0 ); if( !ssl_client_hello_has_cert_extensions( ssl ) ) return( 0 ); ssl->handshake->tls13_kex_modes = MBEDTLS_SSL_TLS1_3_KEY_EXCHANGE_MODE_EPHEMERAL; return( 1 ); } static int ssl_client_hello_parse( mbedtls_ssl_context *ssl, const unsigned char *buf, const unsigned char *end ) { int ret; size_t i, j; size_t comp_len, sess_len; size_t cipher_suites_len; size_t ext_len; const unsigned char *ciph_offset; const unsigned char *p = buf; const unsigned char *extensions_end; const int* ciphersuites; const mbedtls_ssl_ciphersuite_t* ciphersuite_info; int hrr_required = 0; ssl->handshake->extensions_present = MBEDTLS_SSL_EXT_NONE; /* * ClientHello layer: * 0 . 1 protocol version * 2 . 33 random bytes ( starting with 4 bytes of Unix time ) * 34 . 34 session id length ( 1 byte ) * 35 . 34+x session id * 35+x . 35+x DTLS only: cookie length ( 1 byte ) * 36+x . .. DTLS only: cookie * .. . .. ciphersuite list length ( 2 bytes ) * .. . .. ciphersuite list * .. . .. compression alg. list length ( 1 byte ) * .. . .. compression alg. list * .. . .. extensions length ( 2 bytes, optional ) * .. . .. extensions ( optional ) */ /* Needs to be updated due to mandatory extensions * Minimal length ( with everything empty and extensions ommitted ) is * 2 + 32 + 1 + 2 + 1 = 38 bytes. Check that first, so that we can * read at least up to session id length without worrying. */ MBEDTLS_SSL_CHK_BUF_READ_PTR( p, end, 38 ); /* ... * ProtocolVersion legacy_version = 0x0303; // TLS 1.2 * ... * with ProtocolVersion defined as: * uint16 ProtocolVersion; */ if( !( p[0] == MBEDTLS_SSL_MAJOR_VERSION_3 && p[1] == MBEDTLS_SSL_MINOR_VERSION_3 ) ) { MBEDTLS_SSL_DEBUG_MSG( 1, ( "Unsupported version of TLS." ) ); MBEDTLS_SSL_PEND_FATAL_ALERT( MBEDTLS_SSL_ALERT_MSG_PROTOCOL_VERSION, MBEDTLS_ERR_SSL_BAD_PROTOCOL_VERSION ); ret = MBEDTLS_ERR_SSL_BAD_PROTOCOL_VERSION; return ret; } p += 2; /* * Save client random */ MBEDTLS_SSL_DEBUG_BUF( 3, "client hello, random bytes", p, 32 ); memcpy( &ssl->handshake->randbytes[0], p, 32 ); /* skip random bytes */ p += 32; /* * Parse session ID */ sess_len = p[0]; p++; if( sess_len > 32 ) { MBEDTLS_SSL_DEBUG_MSG( 1, ( "bad client hello message" ) ); return( MBEDTLS_ERR_SSL_DECODE_ERROR ); } ssl->session_negotiate->id_len = sess_len; /* Note that this field is echoed even if * the client's value corresponded to a cached pre-TLS 1.3 session * which the server has chosen not to resume. A client which * receives a legacy_session_id_echo field that does not match what * it sent in the ClientHello MUST abort the handshake with an * "illegal_parameter" alert. */ MBEDTLS_SSL_DEBUG_MSG( 3, ( "client hello, session id length ( %" MBEDTLS_PRINTF_SIZET " )", sess_len ) ); MBEDTLS_SSL_DEBUG_BUF( 3, "client hello, session id", buf, sess_len ); memcpy( &ssl->session_negotiate->id[0], p, sess_len ); /* write session id */ p += sess_len; MBEDTLS_SSL_CHK_BUF_READ_PTR( p, end, 2 ); cipher_suites_len = MBEDTLS_GET_UINT16_BE( p, 0 ); p += 2; MBEDTLS_SSL_CHK_BUF_READ_PTR( p, end, cipher_suites_len ); /* store pointer to ciphersuite list */ ciph_offset = p; MBEDTLS_SSL_DEBUG_BUF( 3, "client hello, ciphersuitelist", p, cipher_suites_len ); /* skip ciphersuites for now */ p += cipher_suites_len; /* * For TLS 1.3 we are not using compression. */ comp_len = p[0]; p++; MBEDTLS_SSL_CHK_BUF_READ_PTR( p, end, comp_len ); MBEDTLS_SSL_DEBUG_BUF( 3, "client hello, compression", p, comp_len ); /* Determine whether we are indeed using null compression */ if( ( comp_len != 1 ) && ( p[0] == 0 ) ) { MBEDTLS_SSL_DEBUG_MSG( 1, ( "bad client hello message" ) ); return( MBEDTLS_ERR_SSL_ILLEGAL_PARAMETER ); } /* skip compression */ p++; /* * Check the extension length */ MBEDTLS_SSL_CHK_BUF_READ_PTR( p, end, 2 ); ext_len = MBEDTLS_GET_UINT16_BE( p, 0 ); p += 2; extensions_end = p + ext_len; MBEDTLS_SSL_CHK_BUF_READ_PTR( p, end, ext_len ); MBEDTLS_SSL_DEBUG_BUF( 3, "client hello extensions", p, ext_len ); while( p < extensions_end ) { unsigned int extension_type; size_t extension_data_len; const unsigned char *extension_data_end; MBEDTLS_SSL_CHK_BUF_READ_PTR( p, end, 4 ); extension_type = MBEDTLS_GET_UINT16_BE( p, 0 ); extension_data_len = MBEDTLS_GET_UINT16_BE( p, 2 ); p += 4; MBEDTLS_SSL_CHK_BUF_READ_PTR( p, extensions_end, extension_data_len ); extension_data_end = p + extension_data_len; switch( extension_type ) { #if defined(MBEDTLS_SSL_COOKIE_C) case MBEDTLS_TLS_EXT_COOKIE: MBEDTLS_SSL_DEBUG_MSG( 3, ( "found cookie extension" ) ); ret = ssl_tls13_parse_cookie_ext( ssl, p, extension_data_end ); /* if cookie verification failed then we return a hello retry * message, or return success and set cookie extension present */ if( ret == MBEDTLS_ERR_SSL_HRR_REQUIRED ) { hrr_required = 1; } else if( ret == 0 ) { ssl->handshake->extensions_present |= MBEDTLS_SSL_EXT_COOKIE; } break; #endif /* MBEDTLS_SSL_COOKIE_C */ #if defined(MBEDTLS_ECDH_C) || defined(MBEDTLS_ECDSA_C) case MBEDTLS_TLS_EXT_SUPPORTED_GROUPS: MBEDTLS_SSL_DEBUG_MSG( 3, ( "found supported group extension" ) ); /* Supported Groups Extension * * When sent by the client, the "supported_groups" extension * indicates the named groups which the client supports, * ordered from most preferred to least preferred. */ ret = mbedtls_ssl_tls13_parse_supported_groups_ext( ssl, p, extension_data_end ); if( ret != 0 ) { MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ssl_parse_supported_groups_ext", ret ); return( ret ); } ssl->handshake->extensions_present |= MBEDTLS_SSL_EXT_SUPPORTED_GROUPS; break; #endif /* MBEDTLS_ECDH_C || MBEDTLS_ECDSA_C */ #if ( defined(MBEDTLS_ECDH_C) || defined(MBEDTLS_ECDSA_C) ) case MBEDTLS_TLS_EXT_KEY_SHARE: MBEDTLS_SSL_DEBUG_MSG( 3, ( "found key share extension" ) ); /* * Key Share Extension * * When sent by the client, the "key_share" extension * contains the endpoint's cryptographic parameters for * ECDHE/DHE key establishment methods. */ ret = ssl_tls13_parse_key_shares_ext( ssl, p, extension_data_end ); if( ret == MBEDTLS_ERR_SSL_HRR_REQUIRED ) { hrr_required = 1; ret = 0; } if( ret != 0 ) return( ret ); ssl->handshake->extensions_present |= MBEDTLS_SSL_EXT_KEY_SHARE; break; #endif /* MBEDTLS_ECDH_C || MBEDTLS_ECDSA_C */ case MBEDTLS_TLS_EXT_SUPPORTED_VERSIONS: MBEDTLS_SSL_DEBUG_MSG( 3, ( "found supported versions extension" ) ); ret = ssl_tls13_parse_supported_versions_ext( ssl, p, extension_data_end ); if( ret != 0 ) { MBEDTLS_SSL_DEBUG_RET( 1, ( "ssl_tls13_parse_supported_versions_ext" ), ret ); return( ret ); } ssl->handshake->extensions_present |= MBEDTLS_SSL_EXT_SUPPORTED_VERSIONS; break; #if defined(MBEDTLS_KEY_EXCHANGE_WITH_CERT_ENABLED) case MBEDTLS_TLS_EXT_SIG_ALG: MBEDTLS_SSL_DEBUG_MSG( 3, ( "found signature_algorithms extension" ) ); ret = mbedtls_ssl_tls13_parse_sig_alg_ext( ssl, p, extension_data_end ); if( ret != 0 ) { MBEDTLS_SSL_DEBUG_MSG( 1, ( "ssl_parse_supported_signature_algorithms_server_ext ( %d )", ret ) ); return( ret ); } ssl->handshake->extensions_present |= MBEDTLS_SSL_EXT_SIG_ALG; break; #endif /* MBEDTLS_KEY_EXCHANGE_WITH_CERT_ENABLED */ default: MBEDTLS_SSL_DEBUG_MSG( 3, ( "unknown extension found: %ud ( ignoring )", extension_type ) ); } p += extension_data_len; } /* Update checksum with either * - The entire content of the CH message, if no PSK extension is present * - The content up to but excluding the PSK extension, if present. */ ssl->handshake->update_checksum( ssl, buf, p - buf ); /* * Search for a matching ciphersuite */ ciphersuites = ssl->conf->ciphersuite_list; ciphersuite_info = NULL; for ( j = 0, p = ciph_offset; j < cipher_suites_len; j += 2, p += 2 ) { for ( i = 0; ciphersuites[i] != 0; i++ ) { if( p[0] != ( ( ciphersuites[i] >> 8 ) & 0xFF ) || p[1] != ( ( ciphersuites[i] ) & 0xFF ) ) continue; ciphersuite_info = mbedtls_ssl_ciphersuite_from_id( ciphersuites[i] ); if( ciphersuite_info == NULL ) { MBEDTLS_SSL_DEBUG_MSG( 1, ( "mbedtls_ssl_ciphersuite_from_id: should never happen" ) ); return( MBEDTLS_ERR_SSL_INTERNAL_ERROR ); } goto have_ciphersuite; } } return( MBEDTLS_ERR_SSL_HANDSHAKE_FAILURE ); have_ciphersuite: MBEDTLS_SSL_DEBUG_MSG( 2, ( "selected ciphersuite: %s", ciphersuite_info->name ) ); ssl->session_negotiate->ciphersuite = ciphersuites[i]; ssl->handshake->ciphersuite_info = ciphersuite_info; /* List all the extensions we have received */ ssl_debug_print_client_hello_exts( ssl ); /* * Determine the key exchange algorithm to use. * There are three types of key exchanges supported in TLS 1.3: * - (EC)DH with ECDSA, * - (EC)DH with PSK, * - plain PSK. * * The PSK-based key exchanges may additionally be used with 0-RTT. * * Our built-in order of preference is * 1 ) Plain PSK Mode * 2 ) (EC)DHE-PSK Mode * 3 ) Certificate Mode */ if( !ssl_check_certificate_key_exchange( ssl ) ) { MBEDTLS_SSL_DEBUG_MSG( 1, ( "ClientHello message misses mandatory extensions." ) ); MBEDTLS_SSL_PEND_FATAL_ALERT( MBEDTLS_SSL_ALERT_MSG_MISSING_EXTENSION , MBEDTLS_ERR_SSL_ILLEGAL_PARAMETER ); return( MBEDTLS_ERR_SSL_ILLEGAL_PARAMETER ); } #if defined(MBEDTLS_SSL_COOKIE_C) /* If we failed to see a cookie extension, and we required it through the * configuration settings ( rr_config ), then we need to send a HRR msg. * Conceptually, this is similiar to having received a cookie that failed * the verification check. */ if( ( ssl->conf->rr_config == MBEDTLS_SSL_FORCE_RR_CHECK_ON ) && !( ssl->handshake->extensions_present & MBEDTLS_SSL_EXT_COOKIE ) ) { MBEDTLS_SSL_DEBUG_MSG( 2, ( "Cookie extension missing. Need to send a HRR." ) ); hrr_required = 1; } #endif /* MBEDTLS_SSL_COOKIE_C */ if( hrr_required == 1 ) return( SSL_CLIENT_HELLO_HRR_REQUIRED ); return( 0 ); } static int ssl_client_hello_postprocess( mbedtls_ssl_context* ssl, int hrr_required ) { int ret = 0; if( ssl->handshake->hello_retry_requests_sent == 0 && ssl->conf->rr_config == MBEDTLS_SSL_FORCE_RR_CHECK_ON ) { hrr_required = SSL_CLIENT_HELLO_HRR_REQUIRED; } if( hrr_required == SSL_CLIENT_HELLO_HRR_REQUIRED ) { /* * Create stateless transcript hash for HRR */ MBEDTLS_SSL_DEBUG_MSG( 4, ( "Reset transcript for HRR" ) ); ret = mbedtls_ssl_reset_transcript_for_hrr( ssl ); if( ret != 0 ) { MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ssl_reset_transcript_for_hrr", ret ); return( ret ); } mbedtls_ssl_session_reset_msg_layer( ssl, 0 ); /* Transmit Hello Retry Request */ mbedtls_ssl_handshake_set_state( ssl, MBEDTLS_SSL_HELLO_RETRY_REQUEST ); return( 0 ); } ret = mbedtls_ssl_tls13_key_schedule_stage_early( ssl ); if( ret != 0 ) { MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ssl_tls1_3_key_schedule_stage_early", ret ); return( ret ); } mbedtls_ssl_handshake_set_state( ssl, MBEDTLS_SSL_SERVER_HELLO ); return( 0 ); } /* * TLS and DTLS 1.3 State Maschine -- server side */ int mbedtls_ssl_tls13_handshake_server_step( mbedtls_ssl_context *ssl ) { int ret = 0; if( ssl->state == MBEDTLS_SSL_HANDSHAKE_OVER || ssl->handshake == NULL ) return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA ); MBEDTLS_SSL_DEBUG_MSG( 2, ( "tls13 server state: %s(%d)", mbedtls_ssl_states_str( ssl->state ), ssl->state ) ); if( ( ret = mbedtls_ssl_flush_output( ssl ) ) != 0 ) return( ret ); switch( ssl->state ) { /* start state */ case MBEDTLS_SSL_HELLO_REQUEST: ssl->handshake->hello_retry_requests_sent = 0; mbedtls_ssl_handshake_set_state( ssl, MBEDTLS_SSL_CLIENT_HELLO ); break; /* ----- READ CLIENT HELLO ----*/ case MBEDTLS_SSL_CLIENT_HELLO: ret = ssl_client_hello_process( ssl ); if( ret != 0 ) MBEDTLS_SSL_DEBUG_RET( 1, "ssl_client_hello_process", ret ); break; case MBEDTLS_SSL_HANDSHAKE_WRAPUP: MBEDTLS_SSL_DEBUG_MSG( 2, ( "handshake: done" ) ); MBEDTLS_SSL_DEBUG_MSG( 1, ( "Switch to application keys for all traffic" ) ); mbedtls_ssl_set_inbound_transform ( ssl, ssl->transform_application ); mbedtls_ssl_set_outbound_transform( ssl, ssl->transform_application ); mbedtls_ssl_tls13_handshake_wrapup( ssl ); mbedtls_ssl_handshake_set_state( ssl, MBEDTLS_SSL_SERVER_NEW_SESSION_TICKET ); break; default: MBEDTLS_SSL_DEBUG_MSG( 1, ( "invalid state %d", ssl->state ) ); return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA ); } return( ret ); } #endif /* MBEDTLS_SSL_SRV_C && MBEDTLS_SSL_PROTO_TLS1_3 */