/* * TLS 1.3 client-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. * * This file is part of mbed TLS ( https://tls.mbed.org ) */ #include "common.h" #if defined(MBEDTLS_SSL_CLI_C) && defined(MBEDTLS_SSL_PROTO_TLS1_3) #include #include "mbedtls/debug.h" #include "mbedtls/error.h" #include "mbedtls/platform.h" #include "ssl_misc.h" #include "ssl_client.h" #include "ssl_tls13_keys.h" /* Write extensions */ /* * ssl_tls13_write_supported_versions_ext(): * * struct { * ProtocolVersion versions<2..254>; * } SupportedVersions; */ MBEDTLS_CHECK_RETURN_CRITICAL static int ssl_tls13_write_supported_versions_ext( mbedtls_ssl_context *ssl, unsigned char *buf, unsigned char *end, size_t *out_len ) { unsigned char *p = buf; unsigned char versions_len = ( ssl->handshake->min_tls_version <= MBEDTLS_SSL_VERSION_TLS1_2 ) ? 4 : 2; *out_len = 0; MBEDTLS_SSL_DEBUG_MSG( 3, ( "client hello, adding supported versions extension" ) ); /* Check if we have space to write the extension: * - extension_type (2 bytes) * - extension_data_length (2 bytes) * - versions_length (1 byte ) * - versions (2 or 4 bytes) */ MBEDTLS_SSL_CHK_BUF_PTR( p, end, 5 + versions_len ); MBEDTLS_PUT_UINT16_BE( MBEDTLS_TLS_EXT_SUPPORTED_VERSIONS, p, 0 ); MBEDTLS_PUT_UINT16_BE( versions_len + 1, p, 2 ); p += 4; /* Length of versions */ *p++ = versions_len; /* Write values of supported versions. * They are defined by the configuration. * Currently, we advertise only TLS 1.3 or both TLS 1.3 and TLS 1.2. */ mbedtls_ssl_write_version( p, MBEDTLS_SSL_TRANSPORT_STREAM, MBEDTLS_SSL_VERSION_TLS1_3 ); MBEDTLS_SSL_DEBUG_MSG( 3, ( "supported version: [3:4]" ) ); if( ssl->handshake->min_tls_version <= MBEDTLS_SSL_VERSION_TLS1_2 ) { mbedtls_ssl_write_version( p + 2, MBEDTLS_SSL_TRANSPORT_STREAM, MBEDTLS_SSL_VERSION_TLS1_2 ); MBEDTLS_SSL_DEBUG_MSG( 3, ( "supported version: [3:3]" ) ); } *out_len = 5 + versions_len; return( 0 ); } MBEDTLS_CHECK_RETURN_CRITICAL static int ssl_tls13_parse_supported_versions_ext( mbedtls_ssl_context *ssl, const unsigned char *buf, const unsigned char *end ) { ((void) ssl); MBEDTLS_SSL_CHK_BUF_READ_PTR( buf, end, 2 ); if( mbedtls_ssl_read_version( buf, ssl->conf->transport ) != MBEDTLS_SSL_VERSION_TLS1_3 ) { MBEDTLS_SSL_DEBUG_MSG( 1, ( "unexpected version" ) ); MBEDTLS_SSL_PEND_FATAL_ALERT( MBEDTLS_SSL_ALERT_MSG_ILLEGAL_PARAMETER, MBEDTLS_ERR_SSL_ILLEGAL_PARAMETER); return( MBEDTLS_ERR_SSL_ILLEGAL_PARAMETER ); } if( &buf[2] != end ) { MBEDTLS_SSL_DEBUG_MSG( 1, ( "supported_versions ext data length incorrect" ) ); MBEDTLS_SSL_PEND_FATAL_ALERT( MBEDTLS_SSL_ALERT_MSG_DECODE_ERROR, MBEDTLS_ERR_SSL_DECODE_ERROR ); return( MBEDTLS_ERR_SSL_DECODE_ERROR ); } return( 0 ); } #if defined(MBEDTLS_SSL_ALPN) MBEDTLS_CHECK_RETURN_CRITICAL static int ssl_tls13_parse_alpn_ext( mbedtls_ssl_context *ssl, const unsigned char *buf, size_t len ) { const unsigned char *p = buf; const unsigned char *end = buf + len; size_t protocol_name_list_len, protocol_name_len; const unsigned char *protocol_name_list_end; /* If we didn't send it, the server shouldn't send it */ if( ssl->conf->alpn_list == NULL ) return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA ); /* * opaque ProtocolName<1..2^8-1>; * * struct { * ProtocolName protocol_name_list<2..2^16-1> * } ProtocolNameList; * * the "ProtocolNameList" MUST contain exactly one "ProtocolName" */ MBEDTLS_SSL_CHK_BUF_READ_PTR( p, end, 2 ); protocol_name_list_len = MBEDTLS_GET_UINT16_BE( p, 0 ); p += 2; MBEDTLS_SSL_CHK_BUF_READ_PTR( p, end, protocol_name_list_len ); protocol_name_list_end = p + protocol_name_list_len; MBEDTLS_SSL_CHK_BUF_READ_PTR( p, protocol_name_list_end, 1 ); protocol_name_len = *p++; /* Check that the server chosen protocol was in our list and save it */ MBEDTLS_SSL_CHK_BUF_READ_PTR( p, protocol_name_list_end, protocol_name_len ); for( const char **alpn = ssl->conf->alpn_list; *alpn != NULL; alpn++ ) { if( protocol_name_len == strlen( *alpn ) && memcmp( p, *alpn, protocol_name_len ) == 0 ) { ssl->alpn_chosen = *alpn; return( 0 ); } } return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA ); } #endif /* MBEDTLS_SSL_ALPN */ MBEDTLS_CHECK_RETURN_CRITICAL static int ssl_tls13_reset_key_share( mbedtls_ssl_context *ssl ) { uint16_t group_id = ssl->handshake->offered_group_id; if( group_id == 0 ) return( MBEDTLS_ERR_SSL_INTERNAL_ERROR ); #if defined(MBEDTLS_ECDH_C) if( mbedtls_ssl_tls13_named_group_is_ecdhe( group_id ) ) { int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; psa_status_t status = PSA_ERROR_CORRUPTION_DETECTED; /* Destroy generated private key. */ status = psa_destroy_key( ssl->handshake->ecdh_psa_privkey ); if( status != PSA_SUCCESS ) { ret = psa_ssl_status_to_mbedtls( status ); MBEDTLS_SSL_DEBUG_RET( 1, "psa_destroy_key", ret ); return( ret ); } ssl->handshake->ecdh_psa_privkey = MBEDTLS_SVC_KEY_ID_INIT; return( 0 ); } else #endif /* MBEDTLS_ECDH_C */ if( 0 /* other KEMs? */ ) { /* Do something */ } return( MBEDTLS_ERR_SSL_INTERNAL_ERROR ); } /* * Functions for writing key_share extension. */ MBEDTLS_CHECK_RETURN_CRITICAL static int ssl_tls13_get_default_group_id( mbedtls_ssl_context *ssl, uint16_t *group_id ) { int ret = MBEDTLS_ERR_SSL_FEATURE_UNAVAILABLE; #if defined(MBEDTLS_ECDH_C) const uint16_t *group_list = mbedtls_ssl_get_groups( ssl ); /* Pick first available ECDHE group compatible with TLS 1.3 */ if( group_list == NULL ) return( MBEDTLS_ERR_SSL_BAD_CONFIG ); for ( ; *group_list != 0; group_list++ ) { const mbedtls_ecp_curve_info *curve_info; curve_info = mbedtls_ecp_curve_info_from_tls_id( *group_list ); if( curve_info != NULL && mbedtls_ssl_tls13_named_group_is_ecdhe( *group_list ) ) { *group_id = *group_list; return( 0 ); } } #else ((void) ssl); ((void) group_id); #endif /* MBEDTLS_ECDH_C */ /* * Add DHE named groups here. * Pick first available DHE group compatible with TLS 1.3 */ return( ret ); } /* * ssl_tls13_write_key_share_ext * * Structure of key_share extension in ClientHello: * * struct { * NamedGroup group; * opaque key_exchange<1..2^16-1>; * } KeyShareEntry; * struct { * KeyShareEntry client_shares<0..2^16-1>; * } KeyShareClientHello; */ MBEDTLS_CHECK_RETURN_CRITICAL static int ssl_tls13_write_key_share_ext( mbedtls_ssl_context *ssl, unsigned char *buf, unsigned char *end, size_t *out_len ) { unsigned char *p = buf; unsigned char *client_shares; /* Start of client_shares */ size_t client_shares_len; /* Length of client_shares */ uint16_t group_id; int ret = MBEDTLS_ERR_SSL_FEATURE_UNAVAILABLE; *out_len = 0; /* Check if we have space for header and length fields: * - extension_type (2 bytes) * - extension_data_length (2 bytes) * - client_shares_length (2 bytes) */ MBEDTLS_SSL_CHK_BUF_PTR( p, end, 6 ); p += 6; MBEDTLS_SSL_DEBUG_MSG( 3, ( "client hello: adding key share extension" ) ); /* HRR could already have requested something else. */ group_id = ssl->handshake->offered_group_id; if( !mbedtls_ssl_tls13_named_group_is_ecdhe( group_id ) && !mbedtls_ssl_tls13_named_group_is_dhe( group_id ) ) { MBEDTLS_SSL_PROC_CHK( ssl_tls13_get_default_group_id( ssl, &group_id ) ); } /* * Dispatch to type-specific key generation function. * * So far, we're only supporting ECDHE. With the introduction * of PQC KEMs, we'll want to have multiple branches, one per * type of KEM, and dispatch to the corresponding crypto. And * only one key share entry is allowed. */ client_shares = p; #if defined(MBEDTLS_ECDH_C) if( mbedtls_ssl_tls13_named_group_is_ecdhe( group_id ) ) { /* Pointer to group */ unsigned char *group = p; /* Length of key_exchange */ size_t key_exchange_len = 0; /* Check there is space for header of KeyShareEntry * - group (2 bytes) * - key_exchange_length (2 bytes) */ MBEDTLS_SSL_CHK_BUF_PTR( p, end, 4 ); p += 4; ret = mbedtls_ssl_tls13_generate_and_write_ecdh_key_exchange( ssl, group_id, p, end, &key_exchange_len ); p += key_exchange_len; if( ret != 0 ) return( ret ); /* Write group */ MBEDTLS_PUT_UINT16_BE( group_id, group, 0 ); /* Write key_exchange_length */ MBEDTLS_PUT_UINT16_BE( key_exchange_len, group, 2 ); } else #endif /* MBEDTLS_ECDH_C */ if( 0 /* other KEMs? */ ) { /* Do something */ } else return( MBEDTLS_ERR_SSL_INTERNAL_ERROR ); /* Length of client_shares */ client_shares_len = p - client_shares; if( client_shares_len == 0) { MBEDTLS_SSL_DEBUG_MSG( 1, ( "No key share defined." ) ); return( MBEDTLS_ERR_SSL_INTERNAL_ERROR ); } /* Write extension_type */ MBEDTLS_PUT_UINT16_BE( MBEDTLS_TLS_EXT_KEY_SHARE, buf, 0 ); /* Write extension_data_length */ MBEDTLS_PUT_UINT16_BE( client_shares_len + 2, buf, 2 ); /* Write client_shares_length */ MBEDTLS_PUT_UINT16_BE( client_shares_len, buf, 4 ); /* Update offered_group_id field */ ssl->handshake->offered_group_id = group_id; /* Output the total length of key_share extension. */ *out_len = p - buf; MBEDTLS_SSL_DEBUG_BUF( 3, "client hello, key_share extension", buf, *out_len ); ssl->handshake->extensions_present |= MBEDTLS_SSL_EXT_KEY_SHARE; cleanup: return( ret ); } /* * ssl_tls13_parse_hrr_key_share_ext() * Parse key_share extension in Hello Retry Request * * struct { * NamedGroup selected_group; * } KeyShareHelloRetryRequest; */ MBEDTLS_CHECK_RETURN_CRITICAL static int ssl_tls13_parse_hrr_key_share_ext( mbedtls_ssl_context *ssl, const unsigned char *buf, const unsigned char *end ) { const mbedtls_ecp_curve_info *curve_info = NULL; const unsigned char *p = buf; int selected_group; int found = 0; const uint16_t *group_list = mbedtls_ssl_get_groups( ssl ); if( group_list == NULL ) return( MBEDTLS_ERR_SSL_BAD_CONFIG ); MBEDTLS_SSL_DEBUG_BUF( 3, "key_share extension", p, end - buf ); /* Read selected_group */ MBEDTLS_SSL_CHK_BUF_READ_PTR( p, end, 2 ); selected_group = MBEDTLS_GET_UINT16_BE( p, 0 ); MBEDTLS_SSL_DEBUG_MSG( 3, ( "selected_group ( %d )", selected_group ) ); /* Upon receipt of this extension in a HelloRetryRequest, the client * MUST first verify that the selected_group field corresponds to a * group which was provided in the "supported_groups" extension in the * original ClientHello. * The supported_group was based on the info in ssl->conf->group_list. * * If the server provided a key share that was not sent in the ClientHello * then the client MUST abort the handshake with an "illegal_parameter" alert. */ for( ; *group_list != 0; group_list++ ) { curve_info = mbedtls_ecp_curve_info_from_tls_id( *group_list ); if( curve_info == NULL || curve_info->tls_id != selected_group ) continue; /* We found a match */ found = 1; break; } /* Client MUST verify that the selected_group field does not * correspond to a group which was provided in the "key_share" * extension in the original ClientHello. If the server sent an * HRR message with a key share already provided in the * ClientHello then the client MUST abort the handshake with * an "illegal_parameter" alert. */ if( found == 0 || selected_group == ssl->handshake->offered_group_id ) { MBEDTLS_SSL_DEBUG_MSG( 1, ( "Invalid key share in HRR" ) ); MBEDTLS_SSL_PEND_FATAL_ALERT( MBEDTLS_SSL_ALERT_MSG_ILLEGAL_PARAMETER, MBEDTLS_ERR_SSL_ILLEGAL_PARAMETER ); return( MBEDTLS_ERR_SSL_ILLEGAL_PARAMETER ); } /* Remember server's preference for next ClientHello */ ssl->handshake->offered_group_id = selected_group; return( 0 ); } /* * ssl_tls13_parse_key_share_ext() * Parse key_share extension in Server Hello * * struct { * KeyShareEntry server_share; * } KeyShareServerHello; * struct { * NamedGroup group; * opaque key_exchange<1..2^16-1>; * } KeyShareEntry; */ MBEDTLS_CHECK_RETURN_CRITICAL static int ssl_tls13_parse_key_share_ext( mbedtls_ssl_context *ssl, const unsigned char *buf, const unsigned char *end ) { int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; const unsigned char *p = buf; uint16_t group, offered_group; /* ... * NamedGroup group; (2 bytes) * ... */ MBEDTLS_SSL_CHK_BUF_READ_PTR( p, end, 2 ); group = MBEDTLS_GET_UINT16_BE( p, 0 ); p += 2; /* Check that the chosen group matches the one we offered. */ offered_group = ssl->handshake->offered_group_id; if( offered_group != group ) { MBEDTLS_SSL_DEBUG_MSG( 1, ( "Invalid server key share, our group %u, their group %u", (unsigned) offered_group, (unsigned) group ) ); MBEDTLS_SSL_PEND_FATAL_ALERT( MBEDTLS_SSL_ALERT_MSG_HANDSHAKE_FAILURE, MBEDTLS_ERR_SSL_HANDSHAKE_FAILURE ); return( MBEDTLS_ERR_SSL_HANDSHAKE_FAILURE ); } #if defined(MBEDTLS_ECDH_C) if( mbedtls_ssl_tls13_named_group_is_ecdhe( group ) ) { const mbedtls_ecp_curve_info *curve_info = mbedtls_ecp_curve_info_from_tls_id( group ); if( curve_info == NULL ) { MBEDTLS_SSL_DEBUG_MSG( 1, ( "Invalid TLS curve group id" ) ); return( MBEDTLS_ERR_SSL_INTERNAL_ERROR ); } MBEDTLS_SSL_DEBUG_MSG( 2, ( "ECDH curve: %s", curve_info->name ) ); ret = mbedtls_ssl_tls13_read_public_ecdhe_share( ssl, p, end - p ); if( ret != 0 ) return( ret ); } else #endif /* MBEDTLS_ECDH_C */ if( 0 /* other KEMs? */ ) { /* Do something */ } else return( MBEDTLS_ERR_SSL_INTERNAL_ERROR ); ssl->handshake->extensions_present |= MBEDTLS_SSL_EXT_KEY_SHARE; return( ret ); } /* * ssl_tls13_parse_cookie_ext() * Parse cookie extension in Hello Retry Request * * struct { * opaque cookie<1..2^16-1>; * } Cookie; * * When sending a HelloRetryRequest, the server MAY provide a "cookie" * extension to the client (this is an exception to the usual rule that * the only extensions that may be sent are those that appear in the * ClientHello). When sending the new ClientHello, the client MUST copy * the contents of the extension received in the HelloRetryRequest into * a "cookie" extension in the new ClientHello. Clients MUST NOT use * cookies in their initial ClientHello in subsequent connections. */ MBEDTLS_CHECK_RETURN_CRITICAL static int ssl_tls13_parse_cookie_ext( mbedtls_ssl_context *ssl, const unsigned char *buf, const unsigned char *end ) { uint16_t cookie_len; const unsigned char *p = buf; mbedtls_ssl_handshake_params *handshake = ssl->handshake; /* Retrieve length field of cookie */ 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, "cookie extension", p, cookie_len ); mbedtls_free( handshake->cookie ); handshake->hrr_cookie_len = 0; handshake->cookie = mbedtls_calloc( 1, cookie_len ); if( handshake->cookie == NULL ) { MBEDTLS_SSL_DEBUG_MSG( 1, ( "alloc failed ( %ud bytes )", cookie_len ) ); return( MBEDTLS_ERR_SSL_ALLOC_FAILED ); } memcpy( handshake->cookie, p, cookie_len ); handshake->hrr_cookie_len = cookie_len; return( 0 ); } MBEDTLS_CHECK_RETURN_CRITICAL static int ssl_tls13_write_cookie_ext( mbedtls_ssl_context *ssl, unsigned char *buf, unsigned char *end, size_t *out_len ) { unsigned char *p = buf; *out_len = 0; mbedtls_ssl_handshake_params *handshake = ssl->handshake; if( handshake->cookie == NULL ) { MBEDTLS_SSL_DEBUG_MSG( 3, ( "no cookie to send; skip extension" ) ); return( 0 ); } MBEDTLS_SSL_DEBUG_BUF( 3, "client hello, cookie", handshake->cookie, handshake->hrr_cookie_len ); MBEDTLS_SSL_CHK_BUF_PTR( p, end, handshake->hrr_cookie_len + 6 ); MBEDTLS_SSL_DEBUG_MSG( 3, ( "client hello, adding cookie extension" ) ); MBEDTLS_PUT_UINT16_BE( MBEDTLS_TLS_EXT_COOKIE, p, 0 ); MBEDTLS_PUT_UINT16_BE( handshake->hrr_cookie_len + 2, p, 2 ); MBEDTLS_PUT_UINT16_BE( handshake->hrr_cookie_len, p, 4 ); p += 6; /* Cookie */ memcpy( p, handshake->cookie, handshake->hrr_cookie_len ); *out_len = handshake->hrr_cookie_len + 6; return( 0 ); } int mbedtls_ssl_tls13_write_client_hello_exts( mbedtls_ssl_context *ssl, unsigned char *buf, unsigned char *end, size_t *out_len ) { int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; unsigned char *p = buf; size_t ext_len; *out_len = 0; /* Write supported_versions extension * * Supported Versions Extension is mandatory with TLS 1.3. */ ret = ssl_tls13_write_supported_versions_ext( ssl, p, end, &ext_len ); if( ret != 0 ) return( ret ); p += ext_len; /* Echo the cookie if the server provided one in its preceding * HelloRetryRequest message. */ ret = ssl_tls13_write_cookie_ext( ssl, p, end, &ext_len ); if( ret != 0 ) return( ret ); p += ext_len; if( mbedtls_ssl_conf_tls13_some_ephemeral_enabled( ssl ) ) { ret = ssl_tls13_write_key_share_ext( ssl, p, end, &ext_len ); if( ret != 0 ) return( ret ); p += ext_len; } *out_len = p - buf; return( 0 ); } /* * Functions for parsing and processing Server Hello */ /** * \brief Detect if the ServerHello contains a supported_versions extension * or not. * * \param[in] ssl SSL context * \param[in] buf Buffer containing the ServerHello message * \param[in] end End of the buffer containing the ServerHello message * * \return 0 if the ServerHello does not contain a supported_versions extension * \return 1 if the ServerHello contains a supported_versions extension * \return A negative value if an error occurred while parsing the ServerHello. */ MBEDTLS_CHECK_RETURN_CRITICAL static int ssl_tls13_is_supported_versions_ext_present( mbedtls_ssl_context *ssl, const unsigned char *buf, const unsigned char *end ) { const unsigned char *p = buf; size_t legacy_session_id_echo_len; size_t extensions_len; const unsigned char *extensions_end; /* * Check there is enough data to access the legacy_session_id_echo vector * length: * - legacy_version 2 bytes * - random MBEDTLS_SERVER_HELLO_RANDOM_LEN bytes * - legacy_session_id_echo length 1 byte */ MBEDTLS_SSL_CHK_BUF_READ_PTR( p, end, MBEDTLS_SERVER_HELLO_RANDOM_LEN + 3 ); p += MBEDTLS_SERVER_HELLO_RANDOM_LEN + 2; legacy_session_id_echo_len = *p; /* * Jump to the extensions, jumping over: * - legacy_session_id_echo (legacy_session_id_echo_len + 1) bytes * - cipher_suite 2 bytes * - legacy_compression_method 1 byte */ MBEDTLS_SSL_CHK_BUF_READ_PTR( p, end, legacy_session_id_echo_len + 4 ); p += legacy_session_id_echo_len + 4; /* Case of no extension */ if( p == end ) return( 0 ); /* ... * Extension extensions<6..2^16-1>; * ... * struct { * ExtensionType extension_type; (2 bytes) * opaque extension_data<0..2^16-1>; * } Extension; */ MBEDTLS_SSL_CHK_BUF_READ_PTR( p, end, 2 ); extensions_len = MBEDTLS_GET_UINT16_BE( p, 0 ); p += 2; /* Check extensions do not go beyond the buffer of data. */ MBEDTLS_SSL_CHK_BUF_READ_PTR( p, end, extensions_len ); extensions_end = p + extensions_len; while( p < extensions_end ) { unsigned int extension_type; size_t extension_data_len; MBEDTLS_SSL_CHK_BUF_READ_PTR( p, extensions_end, 4 ); extension_type = MBEDTLS_GET_UINT16_BE( p, 0 ); extension_data_len = MBEDTLS_GET_UINT16_BE( p, 2 ); p += 4; if( extension_type == MBEDTLS_TLS_EXT_SUPPORTED_VERSIONS ) return( 1 ); MBEDTLS_SSL_CHK_BUF_READ_PTR( p, extensions_end, extension_data_len ); p += extension_data_len; } return( 0 ); } /* Returns a negative value on failure, and otherwise * - 1 if the last eight bytes of the ServerHello random bytes indicate that * the server is TLS 1.3 capable but negotiating TLS 1.2 or below. * - 0 otherwise */ MBEDTLS_CHECK_RETURN_CRITICAL static int ssl_tls13_is_downgrade_negotiation( mbedtls_ssl_context *ssl, const unsigned char *buf, const unsigned char *end ) { /* First seven bytes of the magic downgrade strings, see RFC 8446 4.1.3 */ static const unsigned char magic_downgrade_string[] = { 0x44, 0x4F, 0x57, 0x4E, 0x47, 0x52, 0x44 }; const unsigned char *last_eight_bytes_of_random; unsigned char last_byte_of_random; MBEDTLS_SSL_CHK_BUF_READ_PTR( buf, end, MBEDTLS_SERVER_HELLO_RANDOM_LEN + 2 ); last_eight_bytes_of_random = buf + 2 + MBEDTLS_SERVER_HELLO_RANDOM_LEN - 8; if( memcmp( last_eight_bytes_of_random, magic_downgrade_string, sizeof( magic_downgrade_string ) ) == 0 ) { last_byte_of_random = last_eight_bytes_of_random[7]; return( last_byte_of_random == 0 || last_byte_of_random == 1 ); } return( 0 ); } /* Returns a negative value on failure, and otherwise * - SSL_SERVER_HELLO or * - SSL_SERVER_HELLO_HRR * to indicate which message is expected and to be parsed next. */ #define SSL_SERVER_HELLO 0 #define SSL_SERVER_HELLO_HRR 1 MBEDTLS_CHECK_RETURN_CRITICAL static int ssl_server_hello_is_hrr( mbedtls_ssl_context *ssl, const unsigned char *buf, const unsigned char *end ) { /* Check whether this message is a HelloRetryRequest ( HRR ) message. * * Server Hello and HRR are only distinguished by Random set to the * special value of the SHA-256 of "HelloRetryRequest". * * struct { * ProtocolVersion legacy_version = 0x0303; * Random random; * opaque legacy_session_id_echo<0..32>; * CipherSuite cipher_suite; * uint8 legacy_compression_method = 0; * Extension extensions<6..2^16-1>; * } ServerHello; * */ MBEDTLS_SSL_CHK_BUF_READ_PTR( buf, end, 2 + sizeof( mbedtls_ssl_tls13_hello_retry_request_magic ) ); if( memcmp( buf + 2, mbedtls_ssl_tls13_hello_retry_request_magic, sizeof( mbedtls_ssl_tls13_hello_retry_request_magic ) ) == 0 ) { return( SSL_SERVER_HELLO_HRR ); } return( SSL_SERVER_HELLO ); } /* * Returns a negative value on failure, and otherwise * - SSL_SERVER_HELLO or * - SSL_SERVER_HELLO_HRR or * - SSL_SERVER_HELLO_TLS1_2 */ #define SSL_SERVER_HELLO_TLS1_2 2 MBEDTLS_CHECK_RETURN_CRITICAL static int ssl_tls13_preprocess_server_hello( mbedtls_ssl_context *ssl, const unsigned char *buf, const unsigned char *end ) { int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; mbedtls_ssl_handshake_params *handshake = ssl->handshake; MBEDTLS_SSL_PROC_CHK_NEG( ssl_tls13_is_supported_versions_ext_present( ssl, buf, end ) ); if( ret == 0 ) { MBEDTLS_SSL_PROC_CHK_NEG( ssl_tls13_is_downgrade_negotiation( ssl, buf, end ) ); /* If the server is negotiating TLS 1.2 or below and: * . we did not propose TLS 1.2 or * . the server responded it is TLS 1.3 capable but negotiating a lower * version of the protocol and thus we are under downgrade attack * abort the handshake with an "illegal parameter" alert. */ if( handshake->min_tls_version > MBEDTLS_SSL_VERSION_TLS1_2 || ret ) { MBEDTLS_SSL_PEND_FATAL_ALERT( MBEDTLS_SSL_ALERT_MSG_ILLEGAL_PARAMETER, MBEDTLS_ERR_SSL_ILLEGAL_PARAMETER ); return( MBEDTLS_ERR_SSL_ILLEGAL_PARAMETER ); } ssl->keep_current_message = 1; ssl->tls_version = MBEDTLS_SSL_VERSION_TLS1_2; mbedtls_ssl_add_hs_msg_to_checksum( ssl, MBEDTLS_SSL_HS_SERVER_HELLO, buf, (size_t)(end - buf) ); if( mbedtls_ssl_conf_tls13_some_ephemeral_enabled( ssl ) ) { ret = ssl_tls13_reset_key_share( ssl ); if( ret != 0 ) return( ret ); } return( SSL_SERVER_HELLO_TLS1_2 ); } handshake->extensions_present = MBEDTLS_SSL_EXT_NONE; ret = ssl_server_hello_is_hrr( ssl, buf, end ); switch( ret ) { case SSL_SERVER_HELLO: MBEDTLS_SSL_DEBUG_MSG( 2, ( "received ServerHello message" ) ); break; case SSL_SERVER_HELLO_HRR: MBEDTLS_SSL_DEBUG_MSG( 2, ( "received HelloRetryRequest message" ) ); /* If a client receives a second * HelloRetryRequest in the same connection (i.e., where the ClientHello * was itself in response to a HelloRetryRequest), it MUST abort the * handshake with an "unexpected_message" alert. */ if( handshake->hello_retry_request_count > 0 ) { MBEDTLS_SSL_DEBUG_MSG( 1, ( "Multiple HRRs received" ) ); MBEDTLS_SSL_PEND_FATAL_ALERT( MBEDTLS_SSL_ALERT_MSG_UNEXPECTED_MESSAGE, MBEDTLS_ERR_SSL_UNEXPECTED_MESSAGE ); return( MBEDTLS_ERR_SSL_UNEXPECTED_MESSAGE ); } /* * Clients must abort the handshake with an "illegal_parameter" * alert if the HelloRetryRequest would not result in any change * in the ClientHello. * In a PSK only key exchange that what we expect. */ if( ! mbedtls_ssl_conf_tls13_some_ephemeral_enabled( ssl ) ) { MBEDTLS_SSL_DEBUG_MSG( 1, ( "Unexpected HRR in pure PSK key exchange." ) ); MBEDTLS_SSL_PEND_FATAL_ALERT( MBEDTLS_SSL_ALERT_MSG_ILLEGAL_PARAMETER, MBEDTLS_ERR_SSL_ILLEGAL_PARAMETER); return( MBEDTLS_ERR_SSL_ILLEGAL_PARAMETER ); } handshake->hello_retry_request_count++; break; } cleanup: return( ret ); } MBEDTLS_CHECK_RETURN_CRITICAL static int ssl_tls13_check_server_hello_session_id_echo( mbedtls_ssl_context *ssl, const unsigned char **buf, const unsigned char *end ) { const unsigned char *p = *buf; size_t legacy_session_id_echo_len; MBEDTLS_SSL_CHK_BUF_READ_PTR( p, end, 1 ); legacy_session_id_echo_len = *p++ ; MBEDTLS_SSL_CHK_BUF_READ_PTR( p, end, legacy_session_id_echo_len ); /* legacy_session_id_echo */ if( ssl->session_negotiate->id_len != legacy_session_id_echo_len || memcmp( ssl->session_negotiate->id, p , legacy_session_id_echo_len ) != 0 ) { MBEDTLS_SSL_DEBUG_BUF( 3, "Expected Session ID", ssl->session_negotiate->id, ssl->session_negotiate->id_len ); MBEDTLS_SSL_DEBUG_BUF( 3, "Received Session ID", p, legacy_session_id_echo_len ); MBEDTLS_SSL_PEND_FATAL_ALERT( MBEDTLS_SSL_ALERT_MSG_ILLEGAL_PARAMETER, MBEDTLS_ERR_SSL_ILLEGAL_PARAMETER); return( MBEDTLS_ERR_SSL_ILLEGAL_PARAMETER ); } p += legacy_session_id_echo_len; *buf = p; MBEDTLS_SSL_DEBUG_BUF( 3, "Session ID", ssl->session_negotiate->id, ssl->session_negotiate->id_len ); return( 0 ); } /* Parse ServerHello message and configure context * * struct { * ProtocolVersion legacy_version = 0x0303; // TLS 1.2 * Random random; * opaque legacy_session_id_echo<0..32>; * CipherSuite cipher_suite; * uint8 legacy_compression_method = 0; * Extension extensions<6..2^16-1>; * } ServerHello; */ MBEDTLS_CHECK_RETURN_CRITICAL static int ssl_tls13_parse_server_hello( mbedtls_ssl_context *ssl, const unsigned char *buf, const unsigned char *end, int is_hrr ) { int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; const unsigned char *p = buf; mbedtls_ssl_handshake_params *handshake = ssl->handshake; size_t extensions_len; const unsigned char *extensions_end; uint16_t cipher_suite; const mbedtls_ssl_ciphersuite_t *ciphersuite_info; int fatal_alert = 0; /* * Check there is space for minimal fields * * - legacy_version ( 2 bytes) * - random (MBEDTLS_SERVER_HELLO_RANDOM_LEN bytes) * - legacy_session_id_echo ( 1 byte ), minimum size * - cipher_suite ( 2 bytes) * - legacy_compression_method ( 1 byte ) */ MBEDTLS_SSL_CHK_BUF_READ_PTR( p, end, MBEDTLS_SERVER_HELLO_RANDOM_LEN + 6 ); MBEDTLS_SSL_DEBUG_BUF( 4, "server hello", p, end - p ); MBEDTLS_SSL_DEBUG_BUF( 3, "server hello, version", p, 2 ); /* ... * ProtocolVersion legacy_version = 0x0303; // TLS 1.2 * ... * with ProtocolVersion defined as: * uint16 ProtocolVersion; */ if( mbedtls_ssl_read_version( p, ssl->conf->transport ) != MBEDTLS_SSL_VERSION_TLS1_2 ) { 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; goto cleanup; } p += 2; /* ... * Random random; * ... * with Random defined as: * opaque Random[MBEDTLS_SERVER_HELLO_RANDOM_LEN]; */ if( !is_hrr ) { memcpy( &handshake->randbytes[MBEDTLS_CLIENT_HELLO_RANDOM_LEN], p, MBEDTLS_SERVER_HELLO_RANDOM_LEN ); MBEDTLS_SSL_DEBUG_BUF( 3, "server hello, random bytes", p, MBEDTLS_SERVER_HELLO_RANDOM_LEN ); } p += MBEDTLS_SERVER_HELLO_RANDOM_LEN; /* ... * opaque legacy_session_id_echo<0..32>; * ... */ if( ssl_tls13_check_server_hello_session_id_echo( ssl, &p, end ) != 0 ) { fatal_alert = MBEDTLS_SSL_ALERT_MSG_ILLEGAL_PARAMETER; goto cleanup; } /* ... * CipherSuite cipher_suite; * ... * with CipherSuite defined as: * uint8 CipherSuite[2]; */ MBEDTLS_SSL_CHK_BUF_READ_PTR( p, end, 2 ); cipher_suite = MBEDTLS_GET_UINT16_BE( p, 0 ); p += 2; ciphersuite_info = mbedtls_ssl_ciphersuite_from_id( cipher_suite ); /* * Check whether this ciphersuite is valid and offered. */ if( ( mbedtls_ssl_validate_ciphersuite( ssl, ciphersuite_info, ssl->tls_version, ssl->tls_version ) != 0 ) || !mbedtls_ssl_tls13_cipher_suite_is_offered( ssl, cipher_suite ) ) { fatal_alert = MBEDTLS_SSL_ALERT_MSG_ILLEGAL_PARAMETER; } /* * If we received an HRR before and that the proposed selected * ciphersuite in this server hello is not the same as the one * proposed in the HRR, we abort the handshake and send an * "illegal_parameter" alert. */ else if( ( !is_hrr ) && ( handshake->hello_retry_request_count > 0 ) && ( cipher_suite != ssl->session_negotiate->ciphersuite ) ) { fatal_alert = MBEDTLS_SSL_ALERT_MSG_ILLEGAL_PARAMETER; } if( fatal_alert == MBEDTLS_SSL_ALERT_MSG_ILLEGAL_PARAMETER ) { MBEDTLS_SSL_DEBUG_MSG( 1, ( "invalid ciphersuite(%04x) parameter", cipher_suite ) ); goto cleanup; } /* Configure ciphersuites */ mbedtls_ssl_optimize_checksum( ssl, ciphersuite_info ); handshake->ciphersuite_info = ciphersuite_info; ssl->session_negotiate->ciphersuite = cipher_suite; MBEDTLS_SSL_DEBUG_MSG( 3, ( "server hello, chosen ciphersuite: ( %04x ) - %s", cipher_suite, ciphersuite_info->name ) ); #if defined(MBEDTLS_HAVE_TIME) ssl->session_negotiate->start = time( NULL ); #endif /* MBEDTLS_HAVE_TIME */ /* ... * uint8 legacy_compression_method = 0; * ... */ MBEDTLS_SSL_CHK_BUF_READ_PTR( p, end, 1 ); if( p[0] != 0 ) { MBEDTLS_SSL_DEBUG_MSG( 1, ( "bad legacy compression method" ) ); fatal_alert = MBEDTLS_SSL_ALERT_MSG_ILLEGAL_PARAMETER; goto cleanup; } p++; /* ... * Extension extensions<6..2^16-1>; * ... * struct { * ExtensionType extension_type; (2 bytes) * opaque extension_data<0..2^16-1>; * } Extension; */ MBEDTLS_SSL_CHK_BUF_READ_PTR( p, end, 2 ); extensions_len = MBEDTLS_GET_UINT16_BE( p, 0 ); p += 2; /* Check extensions do not go beyond the buffer of data. */ MBEDTLS_SSL_CHK_BUF_READ_PTR( p, end, extensions_len ); extensions_end = p + extensions_len; MBEDTLS_SSL_DEBUG_BUF( 3, "server hello extensions", p, extensions_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, extensions_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 ) { case MBEDTLS_TLS_EXT_COOKIE: if( !is_hrr ) { fatal_alert = MBEDTLS_SSL_ALERT_MSG_UNSUPPORTED_EXT; goto cleanup; } ret = ssl_tls13_parse_cookie_ext( ssl, p, extension_data_end ); if( ret != 0 ) { MBEDTLS_SSL_DEBUG_RET( 1, "ssl_tls13_parse_cookie_ext", ret ); goto cleanup; } break; case MBEDTLS_TLS_EXT_SUPPORTED_VERSIONS: ret = ssl_tls13_parse_supported_versions_ext( ssl, p, extension_data_end ); if( ret != 0 ) goto cleanup; break; case MBEDTLS_TLS_EXT_PRE_SHARED_KEY: MBEDTLS_SSL_DEBUG_MSG( 3, ( "found pre_shared_key extension." ) ); MBEDTLS_SSL_DEBUG_MSG( 3, ( "pre_shared_key:Not supported yet" ) ); fatal_alert = MBEDTLS_SSL_ALERT_MSG_UNSUPPORTED_EXT; goto cleanup; case MBEDTLS_TLS_EXT_KEY_SHARE: MBEDTLS_SSL_DEBUG_MSG( 3, ( "found key_shares extension" ) ); if( ! mbedtls_ssl_conf_tls13_some_ephemeral_enabled( ssl ) ) { fatal_alert = MBEDTLS_SSL_ALERT_MSG_UNSUPPORTED_EXT; goto cleanup; } if( is_hrr ) ret = ssl_tls13_parse_hrr_key_share_ext( ssl, p, extension_data_end ); else ret = ssl_tls13_parse_key_share_ext( ssl, p, extension_data_end ); if( ret != 0 ) { MBEDTLS_SSL_DEBUG_RET( 1, "ssl_tls13_parse_key_share_ext", ret ); goto cleanup; } break; default: MBEDTLS_SSL_DEBUG_MSG( 3, ( "unknown extension found: %u ( ignoring )", extension_type ) ); fatal_alert = MBEDTLS_SSL_ALERT_MSG_UNSUPPORTED_EXT; goto cleanup; } p += extension_data_len; } cleanup: if( fatal_alert == MBEDTLS_SSL_ALERT_MSG_UNSUPPORTED_EXT ) { MBEDTLS_SSL_PEND_FATAL_ALERT( MBEDTLS_SSL_ALERT_MSG_UNSUPPORTED_EXT, MBEDTLS_ERR_SSL_UNSUPPORTED_EXTENSION ); ret = MBEDTLS_ERR_SSL_UNSUPPORTED_EXTENSION; } else if ( fatal_alert == MBEDTLS_SSL_ALERT_MSG_ILLEGAL_PARAMETER ) { MBEDTLS_SSL_PEND_FATAL_ALERT( MBEDTLS_SSL_ALERT_MSG_ILLEGAL_PARAMETER, MBEDTLS_ERR_SSL_ILLEGAL_PARAMETER ); ret = MBEDTLS_ERR_SSL_ILLEGAL_PARAMETER; } return( ret ); } MBEDTLS_CHECK_RETURN_CRITICAL static int ssl_tls13_postprocess_server_hello( mbedtls_ssl_context *ssl ) { int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; mbedtls_ssl_handshake_params *handshake = ssl->handshake; /* Determine the key exchange mode: * 1) If both the pre_shared_key and key_share extensions were received * then the key exchange mode is PSK with EPHEMERAL. * 2) If only the pre_shared_key extension was received then the key * exchange mode is PSK-only. * 3) If only the key_share extension was received then the key * exchange mode is EPHEMERAL-only. */ switch( handshake->extensions_present & ( MBEDTLS_SSL_EXT_PRE_SHARED_KEY | MBEDTLS_SSL_EXT_KEY_SHARE ) ) { /* Only the pre_shared_key extension was received */ case MBEDTLS_SSL_EXT_PRE_SHARED_KEY: handshake->tls13_kex_modes = MBEDTLS_SSL_TLS1_3_KEY_EXCHANGE_MODE_PSK; break; /* Only the key_share extension was received */ case MBEDTLS_SSL_EXT_KEY_SHARE: handshake->tls13_kex_modes = MBEDTLS_SSL_TLS1_3_KEY_EXCHANGE_MODE_EPHEMERAL; break; /* Both the pre_shared_key and key_share extensions were received */ case ( MBEDTLS_SSL_EXT_PRE_SHARED_KEY | MBEDTLS_SSL_EXT_KEY_SHARE ): handshake->tls13_kex_modes = MBEDTLS_SSL_TLS1_3_KEY_EXCHANGE_MODE_PSK_EPHEMERAL; break; /* Neither pre_shared_key nor key_share extension was received */ default: MBEDTLS_SSL_DEBUG_MSG( 1, ( "Unknown key exchange." ) ); ret = MBEDTLS_ERR_SSL_HANDSHAKE_FAILURE; goto cleanup; } /* Start the TLS 1.3 key schedule: Set the PSK and derive early secret. * * TODO: We don't have to do this in case we offered 0-RTT and the * server accepted it. In this case, we could skip generating * the early secret. */ ret = mbedtls_ssl_tls13_key_schedule_stage_early( ssl ); if( ret != 0 ) { MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ssl_tls13_key_schedule_stage_early", ret ); goto cleanup; } ret = mbedtls_ssl_tls13_compute_handshake_transform( ssl ); if( ret != 0 ) { MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ssl_tls13_compute_handshake_transform", ret ); goto cleanup; } mbedtls_ssl_set_inbound_transform( ssl, handshake->transform_handshake ); MBEDTLS_SSL_DEBUG_MSG( 1, ( "Switch to handshake keys for inbound traffic" ) ); ssl->session_in = ssl->session_negotiate; cleanup: if( ret != 0 ) { MBEDTLS_SSL_PEND_FATAL_ALERT( MBEDTLS_SSL_ALERT_MSG_HANDSHAKE_FAILURE, MBEDTLS_ERR_SSL_HANDSHAKE_FAILURE ); } return( ret ); } MBEDTLS_CHECK_RETURN_CRITICAL static int ssl_tls13_postprocess_hrr( mbedtls_ssl_context *ssl ) { int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; mbedtls_ssl_session_reset_msg_layer( ssl, 0 ); /* * We are going to re-generate a shared secret corresponding to the group * selected by the server, which is different from the group for which we * generated a shared secret in the first client hello. * Thus, reset the shared secret. */ ret = ssl_tls13_reset_key_share( ssl ); if( ret != 0 ) return( ret ); return( 0 ); } /* * Wait and parse ServerHello handshake message. * Handler for MBEDTLS_SSL_SERVER_HELLO */ MBEDTLS_CHECK_RETURN_CRITICAL static int ssl_tls13_process_server_hello( mbedtls_ssl_context *ssl ) { int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; unsigned char *buf = NULL; size_t buf_len = 0; int is_hrr = 0; MBEDTLS_SSL_DEBUG_MSG( 2, ( "=> %s", __func__ ) ); MBEDTLS_SSL_PROC_CHK( mbedtls_ssl_tls13_fetch_handshake_msg( ssl, MBEDTLS_SSL_HS_SERVER_HELLO, &buf, &buf_len ) ); ret = ssl_tls13_preprocess_server_hello( ssl, buf, buf + buf_len ); if( ret < 0 ) goto cleanup; else is_hrr = ( ret == SSL_SERVER_HELLO_HRR ); if( ret == SSL_SERVER_HELLO_TLS1_2 ) { ret = 0; goto cleanup; } MBEDTLS_SSL_PROC_CHK( ssl_tls13_parse_server_hello( ssl, buf, buf + buf_len, is_hrr ) ); if( is_hrr ) MBEDTLS_SSL_PROC_CHK( mbedtls_ssl_reset_transcript_for_hrr( ssl ) ); mbedtls_ssl_add_hs_msg_to_checksum( ssl, MBEDTLS_SSL_HS_SERVER_HELLO, buf, buf_len ); if( is_hrr ) { MBEDTLS_SSL_PROC_CHK( ssl_tls13_postprocess_hrr( ssl ) ); #if defined(MBEDTLS_SSL_TLS1_3_COMPATIBILITY_MODE) /* If not offering early data, the client sends a dummy CCS record * immediately before its second flight. This may either be before * its second ClientHello or before its encrypted handshake flight. */ mbedtls_ssl_handshake_set_state( ssl, MBEDTLS_SSL_CLIENT_CCS_BEFORE_2ND_CLIENT_HELLO ); #else mbedtls_ssl_handshake_set_state( ssl, MBEDTLS_SSL_CLIENT_HELLO ); #endif /* MBEDTLS_SSL_TLS1_3_COMPATIBILITY_MODE */ } else { MBEDTLS_SSL_PROC_CHK( ssl_tls13_postprocess_server_hello( ssl ) ); mbedtls_ssl_handshake_set_state( ssl, MBEDTLS_SSL_ENCRYPTED_EXTENSIONS ); } cleanup: MBEDTLS_SSL_DEBUG_MSG( 2, ( "<= %s ( %s )", __func__, is_hrr?"HelloRetryRequest":"ServerHello" ) ); return( ret ); } /* * * Handler for MBEDTLS_SSL_ENCRYPTED_EXTENSIONS * * The EncryptedExtensions message contains any extensions which * should be protected, i.e., any which are not needed to establish * the cryptographic context. */ /* Parse EncryptedExtensions message * struct { * Extension extensions<0..2^16-1>; * } EncryptedExtensions; */ MBEDTLS_CHECK_RETURN_CRITICAL static int ssl_tls13_parse_encrypted_extensions( mbedtls_ssl_context *ssl, const unsigned char *buf, const unsigned char *end ) { int ret = 0; size_t extensions_len; const unsigned char *p = buf; const unsigned char *extensions_end; MBEDTLS_SSL_CHK_BUF_READ_PTR( p, end, 2 ); extensions_len = MBEDTLS_GET_UINT16_BE( p, 0 ); p += 2; MBEDTLS_SSL_DEBUG_BUF( 3, "encrypted extensions", p, extensions_len ); MBEDTLS_SSL_CHK_BUF_READ_PTR( p, end, extensions_len ); extensions_end = p + extensions_len; while( p < extensions_end ) { unsigned int extension_type; size_t extension_data_len; /* * struct { * ExtensionType extension_type; (2 bytes) * opaque extension_data<0..2^16-1>; * } Extension; */ MBEDTLS_SSL_CHK_BUF_READ_PTR( p, extensions_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 ); /* The client MUST check EncryptedExtensions for the * presence of any forbidden extensions and if any are found MUST abort * the handshake with an "unsupported_extension" alert. */ switch( extension_type ) { case MBEDTLS_TLS_EXT_SUPPORTED_GROUPS: MBEDTLS_SSL_DEBUG_MSG( 3, ( "found extensions supported groups" ) ); break; #if defined(MBEDTLS_SSL_ALPN) case MBEDTLS_TLS_EXT_ALPN: MBEDTLS_SSL_DEBUG_MSG( 3, ( "found alpn extension" ) ); if( ( ret = ssl_tls13_parse_alpn_ext( ssl, p, (size_t)extension_data_len ) ) != 0 ) { return( ret ); } break; #endif /* MBEDTLS_SSL_ALPN */ default: MBEDTLS_SSL_DEBUG_MSG( 3, ( "unsupported extension found: %u ", extension_type) ); MBEDTLS_SSL_PEND_FATAL_ALERT( MBEDTLS_SSL_ALERT_MSG_UNSUPPORTED_EXT, MBEDTLS_ERR_SSL_UNSUPPORTED_EXTENSION ); return ( MBEDTLS_ERR_SSL_UNSUPPORTED_EXTENSION ); } p += extension_data_len; } /* Check that we consumed all the message. */ if( p != end ) { MBEDTLS_SSL_DEBUG_MSG( 1, ( "EncryptedExtension lengths misaligned" ) ); MBEDTLS_SSL_PEND_FATAL_ALERT( MBEDTLS_SSL_ALERT_MSG_DECODE_ERROR, MBEDTLS_ERR_SSL_DECODE_ERROR ); return( MBEDTLS_ERR_SSL_DECODE_ERROR ); } return( ret ); } MBEDTLS_CHECK_RETURN_CRITICAL static int ssl_tls13_process_encrypted_extensions( mbedtls_ssl_context *ssl ) { int ret; unsigned char *buf; size_t buf_len; MBEDTLS_SSL_DEBUG_MSG( 2, ( "=> parse encrypted extensions" ) ); MBEDTLS_SSL_PROC_CHK( mbedtls_ssl_tls13_fetch_handshake_msg( ssl, MBEDTLS_SSL_HS_ENCRYPTED_EXTENSIONS, &buf, &buf_len ) ); /* Process the message contents */ MBEDTLS_SSL_PROC_CHK( ssl_tls13_parse_encrypted_extensions( ssl, buf, buf + buf_len ) ); mbedtls_ssl_add_hs_msg_to_checksum( ssl, MBEDTLS_SSL_HS_ENCRYPTED_EXTENSIONS, buf, buf_len ); #if defined(MBEDTLS_KEY_EXCHANGE_WITH_CERT_ENABLED) if( mbedtls_ssl_tls13_some_psk_enabled( ssl ) ) mbedtls_ssl_handshake_set_state( ssl, MBEDTLS_SSL_SERVER_FINISHED ); else mbedtls_ssl_handshake_set_state( ssl, MBEDTLS_SSL_CERTIFICATE_REQUEST ); #else ((void) ssl); mbedtls_ssl_handshake_set_state( ssl, MBEDTLS_SSL_SERVER_FINISHED ); #endif cleanup: MBEDTLS_SSL_DEBUG_MSG( 2, ( "<= parse encrypted extensions" ) ); return( ret ); } #if defined(MBEDTLS_KEY_EXCHANGE_WITH_CERT_ENABLED) /* * STATE HANDLING: CertificateRequest * */ #define SSL_CERTIFICATE_REQUEST_EXPECT_REQUEST 0 #define SSL_CERTIFICATE_REQUEST_SKIP 1 /* Coordination: * Deals with the ambiguity of not knowing if a CertificateRequest * will be sent. Returns a negative code on failure, or * - SSL_CERTIFICATE_REQUEST_EXPECT_REQUEST * - SSL_CERTIFICATE_REQUEST_SKIP * indicating if a Certificate Request is expected or not. */ MBEDTLS_CHECK_RETURN_CRITICAL static int ssl_tls13_certificate_request_coordinate( mbedtls_ssl_context *ssl ) { int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; if( mbedtls_ssl_tls13_some_psk_enabled( ssl ) ) { MBEDTLS_SSL_DEBUG_MSG( 3, ( "<= skip parse certificate request" ) ); return( SSL_CERTIFICATE_REQUEST_SKIP ); } if( ( ret = mbedtls_ssl_read_record( ssl, 0 ) ) != 0 ) { MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ssl_read_record", ret ); return( ret ); } ssl->keep_current_message = 1; if( ( ssl->in_msgtype == MBEDTLS_SSL_MSG_HANDSHAKE ) && ( ssl->in_msg[0] == MBEDTLS_SSL_HS_CERTIFICATE_REQUEST ) ) { MBEDTLS_SSL_DEBUG_MSG( 3, ( "got a certificate request" ) ); return( SSL_CERTIFICATE_REQUEST_EXPECT_REQUEST ); } MBEDTLS_SSL_DEBUG_MSG( 3, ( "got no certificate request" ) ); return( SSL_CERTIFICATE_REQUEST_SKIP ); } /* * ssl_tls13_parse_certificate_request() * Parse certificate request * struct { * opaque certificate_request_context<0..2^8-1>; * Extension extensions<2..2^16-1>; * } CertificateRequest; */ MBEDTLS_CHECK_RETURN_CRITICAL static int ssl_tls13_parse_certificate_request( mbedtls_ssl_context *ssl, const unsigned char *buf, const unsigned char *end ) { int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; const unsigned char *p = buf; size_t certificate_request_context_len = 0; size_t extensions_len = 0; const unsigned char *extensions_end; unsigned char sig_alg_ext_found = 0; /* ... * opaque certificate_request_context<0..2^8-1> * ... */ MBEDTLS_SSL_CHK_BUF_READ_PTR( p, end, 1 ); certificate_request_context_len = (size_t) p[0]; p += 1; if( certificate_request_context_len > 0 ) { MBEDTLS_SSL_CHK_BUF_READ_PTR( p, end, certificate_request_context_len ); MBEDTLS_SSL_DEBUG_BUF( 3, "Certificate Request Context", p, certificate_request_context_len ); mbedtls_ssl_handshake_params *handshake = ssl->handshake; handshake->certificate_request_context = mbedtls_calloc( 1, certificate_request_context_len ); if( handshake->certificate_request_context == NULL ) { MBEDTLS_SSL_DEBUG_MSG( 1, ( "buffer too small" ) ); return ( MBEDTLS_ERR_SSL_ALLOC_FAILED ); } memcpy( handshake->certificate_request_context, p, certificate_request_context_len ); p += certificate_request_context_len; } /* ... * Extension extensions<2..2^16-1>; * ... */ MBEDTLS_SSL_CHK_BUF_READ_PTR( p, end, 2 ); extensions_len = MBEDTLS_GET_UINT16_BE( p, 0 ); p += 2; MBEDTLS_SSL_CHK_BUF_READ_PTR( p, end, extensions_len ); extensions_end = p + extensions_len; while( p < extensions_end ) { unsigned int extension_type; size_t extension_data_len; MBEDTLS_SSL_CHK_BUF_READ_PTR( p, extensions_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 ); switch( extension_type ) { case MBEDTLS_TLS_EXT_SIG_ALG: MBEDTLS_SSL_DEBUG_MSG( 3, ( "found signature algorithms extension" ) ); ret = mbedtls_ssl_parse_sig_alg_ext( ssl, p, p + extension_data_len ); if( ret != 0 ) return( ret ); if( ! sig_alg_ext_found ) sig_alg_ext_found = 1; else { MBEDTLS_SSL_DEBUG_MSG( 3, ( "Duplicate signature algorithms extensions found" ) ); goto decode_error; } break; default: MBEDTLS_SSL_DEBUG_MSG( 3, ( "unknown extension found: %u ( ignoring )", extension_type ) ); break; } p += extension_data_len; } /* Check that we consumed all the message. */ if( p != end ) { MBEDTLS_SSL_DEBUG_MSG( 1, ( "CertificateRequest misaligned" ) ); goto decode_error; } /* Check that we found signature algorithms extension */ if( ! sig_alg_ext_found ) { MBEDTLS_SSL_DEBUG_MSG( 3, ( "no signature algorithms extension found" ) ); goto decode_error; } ssl->handshake->client_auth = 1; return( 0 ); decode_error: MBEDTLS_SSL_PEND_FATAL_ALERT( MBEDTLS_SSL_ALERT_MSG_DECODE_ERROR, MBEDTLS_ERR_SSL_DECODE_ERROR ); return( MBEDTLS_ERR_SSL_DECODE_ERROR ); } /* * Handler for MBEDTLS_SSL_CERTIFICATE_REQUEST */ MBEDTLS_CHECK_RETURN_CRITICAL static int ssl_tls13_process_certificate_request( mbedtls_ssl_context *ssl ) { int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; MBEDTLS_SSL_DEBUG_MSG( 2, ( "=> parse certificate request" ) ); MBEDTLS_SSL_PROC_CHK_NEG( ssl_tls13_certificate_request_coordinate( ssl ) ); if( ret == SSL_CERTIFICATE_REQUEST_EXPECT_REQUEST ) { unsigned char *buf; size_t buf_len; MBEDTLS_SSL_PROC_CHK( mbedtls_ssl_tls13_fetch_handshake_msg( ssl, MBEDTLS_SSL_HS_CERTIFICATE_REQUEST, &buf, &buf_len ) ); MBEDTLS_SSL_PROC_CHK( ssl_tls13_parse_certificate_request( ssl, buf, buf + buf_len ) ); mbedtls_ssl_add_hs_msg_to_checksum( ssl, MBEDTLS_SSL_HS_CERTIFICATE_REQUEST, buf, buf_len ); } else if( ret == SSL_CERTIFICATE_REQUEST_SKIP ) { ret = 0; } else { MBEDTLS_SSL_DEBUG_MSG( 1, ( "should never happen" ) ); ret = MBEDTLS_ERR_SSL_INTERNAL_ERROR; goto cleanup; } mbedtls_ssl_handshake_set_state( ssl, MBEDTLS_SSL_SERVER_CERTIFICATE ); cleanup: MBEDTLS_SSL_DEBUG_MSG( 2, ( "<= parse certificate request" ) ); return( ret ); } /* * Handler for MBEDTLS_SSL_SERVER_CERTIFICATE */ MBEDTLS_CHECK_RETURN_CRITICAL static int ssl_tls13_process_server_certificate( mbedtls_ssl_context *ssl ) { int ret; ret = mbedtls_ssl_tls13_process_certificate( ssl ); if( ret != 0 ) return( ret ); mbedtls_ssl_handshake_set_state( ssl, MBEDTLS_SSL_CERTIFICATE_VERIFY ); return( 0 ); } /* * Handler for MBEDTLS_SSL_CERTIFICATE_VERIFY */ MBEDTLS_CHECK_RETURN_CRITICAL static int ssl_tls13_process_certificate_verify( mbedtls_ssl_context *ssl ) { int ret; ret = mbedtls_ssl_tls13_process_certificate_verify( ssl ); if( ret != 0 ) return( ret ); mbedtls_ssl_handshake_set_state( ssl, MBEDTLS_SSL_SERVER_FINISHED ); return( 0 ); } #endif /* MBEDTLS_KEY_EXCHANGE_WITH_CERT_ENABLED */ /* * Handler for MBEDTLS_SSL_SERVER_FINISHED */ MBEDTLS_CHECK_RETURN_CRITICAL static int ssl_tls13_process_server_finished( mbedtls_ssl_context *ssl ) { int ret; ret = mbedtls_ssl_tls13_process_finished_message( ssl ); if( ret != 0 ) return( ret ); ret = mbedtls_ssl_tls13_compute_application_transform( ssl ); if( ret != 0 ) { MBEDTLS_SSL_PEND_FATAL_ALERT( MBEDTLS_SSL_ALERT_MSG_HANDSHAKE_FAILURE, MBEDTLS_ERR_SSL_HANDSHAKE_FAILURE ); return( ret ); } #if defined(MBEDTLS_SSL_TLS1_3_COMPATIBILITY_MODE) mbedtls_ssl_handshake_set_state( ssl, MBEDTLS_SSL_CLIENT_CCS_AFTER_SERVER_FINISHED ); #else mbedtls_ssl_handshake_set_state( ssl, MBEDTLS_SSL_CLIENT_CERTIFICATE ); #endif /* MBEDTLS_SSL_TLS1_3_COMPATIBILITY_MODE */ return( 0 ); } /* * Handler for MBEDTLS_SSL_CLIENT_CERTIFICATE */ MBEDTLS_CHECK_RETURN_CRITICAL static int ssl_tls13_write_client_certificate( mbedtls_ssl_context *ssl ) { int non_empty_certificate_msg = 0; MBEDTLS_SSL_DEBUG_MSG( 1, ( "Switch to handshake traffic keys for outbound traffic" ) ); mbedtls_ssl_set_outbound_transform( ssl, ssl->handshake->transform_handshake ); #if defined(MBEDTLS_KEY_EXCHANGE_WITH_CERT_ENABLED) if( ssl->handshake->client_auth ) { int ret = mbedtls_ssl_tls13_write_certificate( ssl ); if( ret != 0 ) return( ret ); if( mbedtls_ssl_own_cert( ssl ) != NULL ) non_empty_certificate_msg = 1; } else { MBEDTLS_SSL_DEBUG_MSG( 2, ( "skip write certificate" ) ); } #endif if( non_empty_certificate_msg ) { mbedtls_ssl_handshake_set_state( ssl, MBEDTLS_SSL_CLIENT_CERTIFICATE_VERIFY ); } else { MBEDTLS_SSL_DEBUG_MSG( 2, ( "skip write certificate verify" ) ); mbedtls_ssl_handshake_set_state( ssl, MBEDTLS_SSL_CLIENT_FINISHED ); } return( 0 ); } #if defined(MBEDTLS_KEY_EXCHANGE_WITH_CERT_ENABLED) /* * Handler for MBEDTLS_SSL_CLIENT_CERTIFICATE_VERIFY */ MBEDTLS_CHECK_RETURN_CRITICAL static int ssl_tls13_write_client_certificate_verify( mbedtls_ssl_context *ssl ) { int ret = mbedtls_ssl_tls13_write_certificate_verify( ssl ); if( ret == 0 ) mbedtls_ssl_handshake_set_state( ssl, MBEDTLS_SSL_CLIENT_FINISHED ); return( ret ); } #endif /* MBEDTLS_KEY_EXCHANGE_WITH_CERT_ENABLED */ /* * Handler for MBEDTLS_SSL_CLIENT_FINISHED */ MBEDTLS_CHECK_RETURN_CRITICAL static int ssl_tls13_write_client_finished( mbedtls_ssl_context *ssl ) { int ret; ret = mbedtls_ssl_tls13_write_finished_message( ssl ); if( ret != 0 ) return( ret ); ret = mbedtls_ssl_tls13_generate_resumption_master_secret( ssl ); if( ret != 0 ) { MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ssl_tls13_generate_resumption_master_secret ", ret ); return ( ret ); } mbedtls_ssl_handshake_set_state( ssl, MBEDTLS_SSL_FLUSH_BUFFERS ); return( 0 ); } /* * Handler for MBEDTLS_SSL_FLUSH_BUFFERS */ MBEDTLS_CHECK_RETURN_CRITICAL static int ssl_tls13_flush_buffers( mbedtls_ssl_context *ssl ) { MBEDTLS_SSL_DEBUG_MSG( 2, ( "handshake: done" ) ); mbedtls_ssl_handshake_set_state( ssl, MBEDTLS_SSL_HANDSHAKE_WRAPUP ); return( 0 ); } /* * Handler for MBEDTLS_SSL_HANDSHAKE_WRAPUP */ MBEDTLS_CHECK_RETURN_CRITICAL static int ssl_tls13_handshake_wrapup( mbedtls_ssl_context *ssl ) { mbedtls_ssl_tls13_handshake_wrapup( ssl ); mbedtls_ssl_handshake_set_state( ssl, MBEDTLS_SSL_HANDSHAKE_OVER ); return( 0 ); } int mbedtls_ssl_tls13_handshake_client_step( mbedtls_ssl_context *ssl ) { int ret = 0; switch( ssl->state ) { /* * ssl->state is initialized as HELLO_REQUEST. It is the same * as CLIENT_HELLO state. */ case MBEDTLS_SSL_HELLO_REQUEST: case MBEDTLS_SSL_CLIENT_HELLO: ret = mbedtls_ssl_write_client_hello( ssl ); break; case MBEDTLS_SSL_SERVER_HELLO: ret = ssl_tls13_process_server_hello( ssl ); break; case MBEDTLS_SSL_ENCRYPTED_EXTENSIONS: ret = ssl_tls13_process_encrypted_extensions( ssl ); break; #if defined(MBEDTLS_KEY_EXCHANGE_WITH_CERT_ENABLED) case MBEDTLS_SSL_CERTIFICATE_REQUEST: ret = ssl_tls13_process_certificate_request( ssl ); break; case MBEDTLS_SSL_SERVER_CERTIFICATE: ret = ssl_tls13_process_server_certificate( ssl ); break; case MBEDTLS_SSL_CERTIFICATE_VERIFY: ret = ssl_tls13_process_certificate_verify( ssl ); break; #endif /* MBEDTLS_KEY_EXCHANGE_WITH_CERT_ENABLED */ case MBEDTLS_SSL_SERVER_FINISHED: ret = ssl_tls13_process_server_finished( ssl ); break; case MBEDTLS_SSL_CLIENT_CERTIFICATE: ret = ssl_tls13_write_client_certificate( ssl ); break; #if defined(MBEDTLS_KEY_EXCHANGE_WITH_CERT_ENABLED) case MBEDTLS_SSL_CLIENT_CERTIFICATE_VERIFY: ret = ssl_tls13_write_client_certificate_verify( ssl ); break; #endif /* MBEDTLS_KEY_EXCHANGE_WITH_CERT_ENABLED */ case MBEDTLS_SSL_CLIENT_FINISHED: ret = ssl_tls13_write_client_finished( ssl ); break; case MBEDTLS_SSL_FLUSH_BUFFERS: ret = ssl_tls13_flush_buffers( ssl ); break; case MBEDTLS_SSL_HANDSHAKE_WRAPUP: ret = ssl_tls13_handshake_wrapup( ssl ); break; /* * Injection of dummy-CCS's for middlebox compatibility */ #if defined(MBEDTLS_SSL_TLS1_3_COMPATIBILITY_MODE) case MBEDTLS_SSL_CLIENT_CCS_BEFORE_2ND_CLIENT_HELLO: ret = mbedtls_ssl_tls13_write_change_cipher_spec( ssl ); if( ret == 0 ) mbedtls_ssl_handshake_set_state( ssl, MBEDTLS_SSL_CLIENT_HELLO ); break; case MBEDTLS_SSL_CLIENT_CCS_AFTER_SERVER_FINISHED: ret = mbedtls_ssl_tls13_write_change_cipher_spec( ssl ); if( ret == 0 ) mbedtls_ssl_handshake_set_state( ssl, MBEDTLS_SSL_CLIENT_CERTIFICATE ); break; #endif /* MBEDTLS_SSL_TLS1_3_COMPATIBILITY_MODE */ default: MBEDTLS_SSL_DEBUG_MSG( 1, ( "invalid state %d", ssl->state ) ); return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA ); } return( ret ); } #endif /* MBEDTLS_SSL_CLI_C && MBEDTLS_SSL_PROTO_TLS1_3 */