| /* |
| * TLS 1.3 key schedule |
| * |
| * 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_PROTO_TLS1_3_EXPERIMENTAL) |
| |
| #include "mbedtls/hkdf.h" |
| #include "ssl_misc.h" |
| #include "ssl_tls13_keys.h" |
| #include "mbedtls/debug.h" |
| |
| #include <stdint.h> |
| #include <string.h> |
| |
| #define MBEDTLS_SSL_TLS1_3_LABEL( name, string ) \ |
| .name = string, |
| |
| struct mbedtls_ssl_tls1_3_labels_struct const mbedtls_ssl_tls1_3_labels = |
| { |
| /* This seems to work in C, despite the string literal being one |
| * character too long due to the 0-termination. */ |
| MBEDTLS_SSL_TLS1_3_LABEL_LIST |
| }; |
| |
| #undef MBEDTLS_SSL_TLS1_3_LABEL |
| |
| /* |
| * This function creates a HkdfLabel structure used in the TLS 1.3 key schedule. |
| * |
| * The HkdfLabel is specified in RFC 8446 as follows: |
| * |
| * struct HkdfLabel { |
| * uint16 length; // Length of expanded key material |
| * opaque label<7..255>; // Always prefixed by "tls13 " |
| * opaque context<0..255>; // Usually a communication transcript hash |
| * }; |
| * |
| * Parameters: |
| * - desired_length: Length of expanded key material |
| * Even though the standard allows expansion to up to |
| * 2**16 Bytes, TLS 1.3 never uses expansion to more than |
| * 255 Bytes, so we require `desired_length` to be at most |
| * 255. This allows us to save a few Bytes of code by |
| * hardcoding the writing of the high bytes. |
| * - (label, llen): label + label length, without "tls13 " prefix |
| * The label length MUST be less than or equal to |
| * MBEDTLS_SSL_TLS1_3_KEY_SCHEDULE_MAX_LABEL_LEN |
| * It is the caller's responsibility to ensure this. |
| * All (label, label length) pairs used in TLS 1.3 |
| * can be obtained via MBEDTLS_SSL_TLS1_3_LBL_WITH_LEN(). |
| * - (ctx, clen): context + context length |
| * The context length MUST be less than or equal to |
| * MBEDTLS_SSL_TLS1_3_KEY_SCHEDULE_MAX_CONTEXT_LEN |
| * It is the caller's responsibility to ensure this. |
| * - dst: Target buffer for HkdfLabel structure, |
| * This MUST be a writable buffer of size |
| * at least SSL_TLS1_3_KEY_SCHEDULE_MAX_HKDF_LABEL_LEN Bytes. |
| * - dlen: Pointer at which to store the actual length of |
| * the HkdfLabel structure on success. |
| */ |
| |
| static const char tls1_3_label_prefix[6] = "tls13 "; |
| |
| #define SSL_TLS1_3_KEY_SCHEDULE_HKDF_LABEL_LEN( label_len, context_len ) \ |
| ( 2 /* expansion length */ \ |
| + 1 /* label length */ \ |
| + label_len \ |
| + 1 /* context length */ \ |
| + context_len ) |
| |
| #define SSL_TLS1_3_KEY_SCHEDULE_MAX_HKDF_LABEL_LEN \ |
| SSL_TLS1_3_KEY_SCHEDULE_HKDF_LABEL_LEN( \ |
| sizeof(tls1_3_label_prefix) + \ |
| MBEDTLS_SSL_TLS1_3_KEY_SCHEDULE_MAX_LABEL_LEN, \ |
| MBEDTLS_SSL_TLS1_3_KEY_SCHEDULE_MAX_CONTEXT_LEN ) |
| |
| static void ssl_tls1_3_hkdf_encode_label( |
| size_t desired_length, |
| const unsigned char *label, size_t llen, |
| const unsigned char *ctx, size_t clen, |
| unsigned char *dst, size_t *dlen ) |
| { |
| size_t total_label_len = |
| sizeof(tls1_3_label_prefix) + llen; |
| size_t total_hkdf_lbl_len = |
| SSL_TLS1_3_KEY_SCHEDULE_HKDF_LABEL_LEN( total_label_len, clen ); |
| |
| unsigned char *p = dst; |
| |
| /* Add the size of the expanded key material. |
| * We're hardcoding the high byte to 0 here assuming that we never use |
| * TLS 1.3 HKDF key expansion to more than 255 Bytes. */ |
| #if MBEDTLS_SSL_TLS1_3_KEY_SCHEDULE_MAX_EXPANSION_LEN > 255 |
| #error "The implementation of ssl_tls1_3_hkdf_encode_label() is not fit for the \ |
| value of MBEDTLS_SSL_TLS1_3_KEY_SCHEDULE_MAX_EXPANSION_LEN" |
| #endif |
| |
| *p++ = 0; |
| *p++ = (unsigned char)( ( desired_length >> 0 ) & 0xFF ); |
| |
| /* Add label incl. prefix */ |
| *p++ = (unsigned char)( total_label_len & 0xFF ); |
| memcpy( p, tls1_3_label_prefix, sizeof(tls1_3_label_prefix) ); |
| p += sizeof(tls1_3_label_prefix); |
| memcpy( p, label, llen ); |
| p += llen; |
| |
| /* Add context value */ |
| *p++ = (unsigned char)( clen & 0xFF ); |
| if( clen != 0 ) |
| memcpy( p, ctx, clen ); |
| |
| /* Return total length to the caller. */ |
| *dlen = total_hkdf_lbl_len; |
| } |
| |
| int mbedtls_ssl_tls1_3_hkdf_expand_label( |
| mbedtls_md_type_t hash_alg, |
| const unsigned char *secret, size_t slen, |
| const unsigned char *label, size_t llen, |
| const unsigned char *ctx, size_t clen, |
| unsigned char *buf, size_t blen ) |
| { |
| const mbedtls_md_info_t *md; |
| unsigned char hkdf_label[ SSL_TLS1_3_KEY_SCHEDULE_MAX_HKDF_LABEL_LEN ]; |
| size_t hkdf_label_len; |
| |
| if( llen > MBEDTLS_SSL_TLS1_3_KEY_SCHEDULE_MAX_LABEL_LEN ) |
| { |
| /* Should never happen since this is an internal |
| * function, and we know statically which labels |
| * are allowed. */ |
| return( MBEDTLS_ERR_SSL_INTERNAL_ERROR ); |
| } |
| |
| if( clen > MBEDTLS_SSL_TLS1_3_KEY_SCHEDULE_MAX_CONTEXT_LEN ) |
| { |
| /* Should not happen, as above. */ |
| return( MBEDTLS_ERR_SSL_INTERNAL_ERROR ); |
| } |
| |
| if( blen > MBEDTLS_SSL_TLS1_3_KEY_SCHEDULE_MAX_EXPANSION_LEN ) |
| { |
| /* Should not happen, as above. */ |
| return( MBEDTLS_ERR_SSL_INTERNAL_ERROR ); |
| } |
| |
| md = mbedtls_md_info_from_type( hash_alg ); |
| if( md == NULL ) |
| return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA ); |
| |
| ssl_tls1_3_hkdf_encode_label( blen, |
| label, llen, |
| ctx, clen, |
| hkdf_label, |
| &hkdf_label_len ); |
| |
| return( mbedtls_hkdf_expand( md, |
| secret, slen, |
| hkdf_label, hkdf_label_len, |
| buf, blen ) ); |
| } |
| |
| /* |
| * The traffic keying material is generated from the following inputs: |
| * |
| * - One secret value per sender. |
| * - A purpose value indicating the specific value being generated |
| * - The desired lengths of key and IV. |
| * |
| * The expansion itself is based on HKDF: |
| * |
| * [sender]_write_key = HKDF-Expand-Label( Secret, "key", "", key_length ) |
| * [sender]_write_iv = HKDF-Expand-Label( Secret, "iv" , "", iv_length ) |
| * |
| * [sender] denotes the sending side and the Secret value is provided |
| * by the function caller. Note that we generate server and client side |
| * keys in a single function call. |
| */ |
| int mbedtls_ssl_tls1_3_make_traffic_keys( |
| mbedtls_md_type_t hash_alg, |
| const unsigned char *client_secret, |
| const unsigned char *server_secret, |
| size_t slen, size_t key_len, size_t iv_len, |
| mbedtls_ssl_key_set *keys ) |
| { |
| int ret = 0; |
| |
| ret = mbedtls_ssl_tls1_3_hkdf_expand_label( hash_alg, |
| client_secret, slen, |
| MBEDTLS_SSL_TLS1_3_LBL_WITH_LEN( key ), |
| NULL, 0, |
| keys->client_write_key, key_len ); |
| if( ret != 0 ) |
| return( ret ); |
| |
| ret = mbedtls_ssl_tls1_3_hkdf_expand_label( hash_alg, |
| server_secret, slen, |
| MBEDTLS_SSL_TLS1_3_LBL_WITH_LEN( key ), |
| NULL, 0, |
| keys->server_write_key, key_len ); |
| if( ret != 0 ) |
| return( ret ); |
| |
| ret = mbedtls_ssl_tls1_3_hkdf_expand_label( hash_alg, |
| client_secret, slen, |
| MBEDTLS_SSL_TLS1_3_LBL_WITH_LEN( iv ), |
| NULL, 0, |
| keys->client_write_iv, iv_len ); |
| if( ret != 0 ) |
| return( ret ); |
| |
| ret = mbedtls_ssl_tls1_3_hkdf_expand_label( hash_alg, |
| server_secret, slen, |
| MBEDTLS_SSL_TLS1_3_LBL_WITH_LEN( iv ), |
| NULL, 0, |
| keys->server_write_iv, iv_len ); |
| if( ret != 0 ) |
| return( ret ); |
| |
| keys->key_len = key_len; |
| keys->iv_len = iv_len; |
| |
| return( 0 ); |
| } |
| |
| int mbedtls_ssl_tls1_3_derive_secret( |
| mbedtls_md_type_t hash_alg, |
| const unsigned char *secret, size_t slen, |
| const unsigned char *label, size_t llen, |
| const unsigned char *ctx, size_t clen, |
| int ctx_hashed, |
| unsigned char *dstbuf, size_t buflen ) |
| { |
| int ret; |
| unsigned char hashed_context[ MBEDTLS_MD_MAX_SIZE ]; |
| |
| const mbedtls_md_info_t *md; |
| md = mbedtls_md_info_from_type( hash_alg ); |
| if( md == NULL ) |
| return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA ); |
| |
| if( ctx_hashed == MBEDTLS_SSL_TLS1_3_CONTEXT_UNHASHED ) |
| { |
| ret = mbedtls_md( md, ctx, clen, hashed_context ); |
| if( ret != 0 ) |
| return( ret ); |
| clen = mbedtls_md_get_size( md ); |
| } |
| else |
| { |
| if( clen > sizeof(hashed_context) ) |
| { |
| /* This should never happen since this function is internal |
| * and the code sets `ctx_hashed` correctly. |
| * Let's double-check nonetheless to not run at the risk |
| * of getting a stack overflow. */ |
| return( MBEDTLS_ERR_SSL_INTERNAL_ERROR ); |
| } |
| |
| memcpy( hashed_context, ctx, clen ); |
| } |
| |
| return( mbedtls_ssl_tls1_3_hkdf_expand_label( hash_alg, |
| secret, slen, |
| label, llen, |
| hashed_context, clen, |
| dstbuf, buflen ) ); |
| } |
| |
| int mbedtls_ssl_tls1_3_evolve_secret( |
| mbedtls_md_type_t hash_alg, |
| const unsigned char *secret_old, |
| const unsigned char *input, size_t input_len, |
| unsigned char *secret_new ) |
| { |
| int ret = MBEDTLS_ERR_SSL_INTERNAL_ERROR; |
| size_t hlen, ilen; |
| unsigned char tmp_secret[ MBEDTLS_MD_MAX_SIZE ] = { 0 }; |
| unsigned char tmp_input [ MBEDTLS_MD_MAX_SIZE ] = { 0 }; |
| |
| const mbedtls_md_info_t *md; |
| md = mbedtls_md_info_from_type( hash_alg ); |
| if( md == NULL ) |
| return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA ); |
| |
| hlen = mbedtls_md_get_size( md ); |
| |
| /* For non-initial runs, call Derive-Secret( ., "derived", "") |
| * on the old secret. */ |
| if( secret_old != NULL ) |
| { |
| ret = mbedtls_ssl_tls1_3_derive_secret( |
| hash_alg, |
| secret_old, hlen, |
| MBEDTLS_SSL_TLS1_3_LBL_WITH_LEN( derived ), |
| NULL, 0, /* context */ |
| MBEDTLS_SSL_TLS1_3_CONTEXT_UNHASHED, |
| tmp_secret, hlen ); |
| if( ret != 0 ) |
| goto cleanup; |
| } |
| |
| if( input != NULL ) |
| { |
| memcpy( tmp_input, input, input_len ); |
| ilen = input_len; |
| } |
| else |
| { |
| ilen = hlen; |
| } |
| |
| /* HKDF-Extract takes a salt and input key material. |
| * The salt is the old secret, and the input key material |
| * is the input secret (PSK / ECDHE). */ |
| ret = mbedtls_hkdf_extract( md, |
| tmp_secret, hlen, |
| tmp_input, ilen, |
| secret_new ); |
| if( ret != 0 ) |
| goto cleanup; |
| |
| ret = 0; |
| |
| cleanup: |
| |
| mbedtls_platform_zeroize( tmp_secret, sizeof(tmp_secret) ); |
| mbedtls_platform_zeroize( tmp_input, sizeof(tmp_input) ); |
| return( ret ); |
| } |
| |
| int mbedtls_ssl_tls1_3_derive_early_secrets( |
| mbedtls_md_type_t md_type, |
| unsigned char const *early_secret, |
| unsigned char const *transcript, size_t transcript_len, |
| mbedtls_ssl_tls1_3_early_secrets *derived ) |
| { |
| int ret; |
| mbedtls_md_info_t const * const md_info = mbedtls_md_info_from_type( md_type ); |
| size_t const md_size = mbedtls_md_get_size( md_info ); |
| |
| /* We should never call this function with an unknown hash, |
| * but add an assertion anyway. */ |
| if( md_info == 0 ) |
| return( MBEDTLS_ERR_SSL_INTERNAL_ERROR ); |
| |
| /* |
| * 0 |
| * | |
| * v |
| * PSK -> HKDF-Extract = Early Secret |
| * | |
| * +-----> Derive-Secret(., "c e traffic", ClientHello) |
| * | = client_early_traffic_secret |
| * | |
| * +-----> Derive-Secret(., "e exp master", ClientHello) |
| * | = early_exporter_master_secret |
| * v |
| */ |
| |
| /* Create client_early_traffic_secret */ |
| ret = mbedtls_ssl_tls1_3_derive_secret( md_type, |
| early_secret, md_size, |
| MBEDTLS_SSL_TLS1_3_LBL_WITH_LEN( c_e_traffic ), |
| transcript, transcript_len, |
| MBEDTLS_SSL_TLS1_3_CONTEXT_HASHED, |
| derived->client_early_traffic_secret, |
| md_size ); |
| if( ret != 0 ) |
| return( ret ); |
| |
| /* Create early exporter */ |
| ret = mbedtls_ssl_tls1_3_derive_secret( md_type, |
| early_secret, md_size, |
| MBEDTLS_SSL_TLS1_3_LBL_WITH_LEN( e_exp_master ), |
| transcript, transcript_len, |
| MBEDTLS_SSL_TLS1_3_CONTEXT_HASHED, |
| derived->early_exporter_master_secret, |
| md_size ); |
| if( ret != 0 ) |
| return( ret ); |
| |
| return( 0 ); |
| } |
| |
| int mbedtls_ssl_tls1_3_derive_handshake_secrets( |
| mbedtls_md_type_t md_type, |
| unsigned char const *handshake_secret, |
| unsigned char const *transcript, size_t transcript_len, |
| mbedtls_ssl_tls1_3_handshake_secrets *derived ) |
| { |
| int ret; |
| mbedtls_md_info_t const * const md_info = mbedtls_md_info_from_type( md_type ); |
| size_t const md_size = mbedtls_md_get_size( md_info ); |
| |
| /* We should never call this function with an unknown hash, |
| * but add an assertion anyway. */ |
| if( md_info == 0 ) |
| return( MBEDTLS_ERR_SSL_INTERNAL_ERROR ); |
| |
| /* |
| * |
| * Handshake Secret |
| * | |
| * +-----> Derive-Secret( ., "c hs traffic", |
| * | ClientHello...ServerHello ) |
| * | = client_handshake_traffic_secret |
| * | |
| * +-----> Derive-Secret( ., "s hs traffic", |
| * | ClientHello...ServerHello ) |
| * | = server_handshake_traffic_secret |
| * |
| */ |
| |
| /* |
| * Compute client_handshake_traffic_secret with |
| * Derive-Secret( ., "c hs traffic", ClientHello...ServerHello ) |
| */ |
| |
| ret = mbedtls_ssl_tls1_3_derive_secret( md_type, |
| handshake_secret, md_size, |
| MBEDTLS_SSL_TLS1_3_LBL_WITH_LEN( c_hs_traffic ), |
| transcript, transcript_len, |
| MBEDTLS_SSL_TLS1_3_CONTEXT_HASHED, |
| derived->client_handshake_traffic_secret, |
| md_size ); |
| if( ret != 0 ) |
| return( ret ); |
| |
| /* |
| * Compute server_handshake_traffic_secret with |
| * Derive-Secret( ., "s hs traffic", ClientHello...ServerHello ) |
| */ |
| |
| ret = mbedtls_ssl_tls1_3_derive_secret( md_type, |
| handshake_secret, md_size, |
| MBEDTLS_SSL_TLS1_3_LBL_WITH_LEN( s_hs_traffic ), |
| transcript, transcript_len, |
| MBEDTLS_SSL_TLS1_3_CONTEXT_HASHED, |
| derived->server_handshake_traffic_secret, |
| md_size ); |
| if( ret != 0 ) |
| return( ret ); |
| |
| return( 0 ); |
| } |
| |
| int mbedtls_ssl_tls1_3_derive_application_secrets( |
| mbedtls_md_type_t md_type, |
| unsigned char const *application_secret, |
| unsigned char const *transcript, size_t transcript_len, |
| mbedtls_ssl_tls1_3_application_secrets *derived ) |
| { |
| int ret; |
| mbedtls_md_info_t const * const md_info = mbedtls_md_info_from_type( md_type ); |
| size_t const md_size = mbedtls_md_get_size( md_info ); |
| |
| /* We should never call this function with an unknown hash, |
| * but add an assertion anyway. */ |
| if( md_info == 0 ) |
| return( MBEDTLS_ERR_SSL_INTERNAL_ERROR ); |
| |
| /* Generate {client,server}_application_traffic_secret_0 |
| * |
| * Master Secret |
| * | |
| * +-----> Derive-Secret( ., "c ap traffic", |
| * | ClientHello...server Finished ) |
| * | = client_application_traffic_secret_0 |
| * | |
| * +-----> Derive-Secret( ., "s ap traffic", |
| * | ClientHello...Server Finished ) |
| * | = server_application_traffic_secret_0 |
| * | |
| * +-----> Derive-Secret( ., "exp master", |
| * | ClientHello...server Finished) |
| * | = exporter_master_secret |
| * |
| */ |
| |
| ret = mbedtls_ssl_tls1_3_derive_secret( md_type, |
| application_secret, md_size, |
| MBEDTLS_SSL_TLS1_3_LBL_WITH_LEN( c_ap_traffic ), |
| transcript, transcript_len, |
| MBEDTLS_SSL_TLS1_3_CONTEXT_HASHED, |
| derived->client_application_traffic_secret_N, |
| md_size ); |
| if( ret != 0 ) |
| return( ret ); |
| |
| ret = mbedtls_ssl_tls1_3_derive_secret( md_type, |
| application_secret, md_size, |
| MBEDTLS_SSL_TLS1_3_LBL_WITH_LEN( s_ap_traffic ), |
| transcript, transcript_len, |
| MBEDTLS_SSL_TLS1_3_CONTEXT_HASHED, |
| derived->server_application_traffic_secret_N, |
| md_size ); |
| if( ret != 0 ) |
| return( ret ); |
| |
| ret = mbedtls_ssl_tls1_3_derive_secret( md_type, |
| application_secret, md_size, |
| MBEDTLS_SSL_TLS1_3_LBL_WITH_LEN( exp_master ), |
| transcript, transcript_len, |
| MBEDTLS_SSL_TLS1_3_CONTEXT_HASHED, |
| derived->exporter_master_secret, |
| md_size ); |
| if( ret != 0 ) |
| return( ret ); |
| |
| return( 0 ); |
| } |
| |
| /* Generate resumption_master_secret for use with the ticket exchange. |
| * |
| * This is not integrated with mbedtls_ssl_tls1_3_derive_application_secrets() |
| * because it uses the transcript hash up to and including ClientFinished. */ |
| int mbedtls_ssl_tls1_3_derive_resumption_master_secret( |
| mbedtls_md_type_t md_type, |
| unsigned char const *application_secret, |
| unsigned char const *transcript, size_t transcript_len, |
| mbedtls_ssl_tls1_3_application_secrets *derived ) |
| { |
| int ret; |
| mbedtls_md_info_t const * const md_info = mbedtls_md_info_from_type( md_type ); |
| size_t const md_size = mbedtls_md_get_size( md_info ); |
| |
| /* We should never call this function with an unknown hash, |
| * but add an assertion anyway. */ |
| if( md_info == 0 ) |
| return( MBEDTLS_ERR_SSL_INTERNAL_ERROR ); |
| |
| ret = mbedtls_ssl_tls1_3_derive_secret( md_type, |
| application_secret, md_size, |
| MBEDTLS_SSL_TLS1_3_LBL_WITH_LEN( res_master ), |
| transcript, transcript_len, |
| MBEDTLS_SSL_TLS1_3_CONTEXT_HASHED, |
| derived->resumption_master_secret, |
| md_size ); |
| |
| if( ret != 0 ) |
| return( ret ); |
| |
| return( 0 ); |
| } |
| |
| static int ssl_tls1_3_calc_finished_core( mbedtls_md_type_t md_type, |
| unsigned char const *base_key, |
| unsigned char const *transcript, |
| unsigned char *dst ) |
| { |
| const mbedtls_md_info_t* const md_info = mbedtls_md_info_from_type( md_type ); |
| size_t const md_size = mbedtls_md_get_size( md_info ); |
| unsigned char finished_key[MBEDTLS_MD_MAX_SIZE]; |
| int ret; |
| |
| /* We should never call this function with an unknown hash, |
| * but add an assertion anyway. */ |
| if( md_info == 0 ) |
| return( MBEDTLS_ERR_SSL_INTERNAL_ERROR ); |
| |
| /* TLS 1.3 Finished message |
| * |
| * struct { |
| * opaque verify_data[Hash.length]; |
| * } Finished; |
| * |
| * verify_data = |
| * HMAC( finished_key, |
| * Hash( Handshake Context + |
| * Certificate* + |
| * CertificateVerify* ) |
| * ) |
| * |
| * finished_key = |
| * HKDF-Expand-Label( BaseKey, "finished", "", Hash.length ) |
| */ |
| |
| ret = mbedtls_ssl_tls1_3_hkdf_expand_label( |
| md_type, base_key, md_size, |
| MBEDTLS_SSL_TLS1_3_LBL_WITH_LEN( finished ), |
| NULL, 0, |
| finished_key, md_size ); |
| if( ret != 0 ) |
| goto exit; |
| |
| ret = mbedtls_md_hmac( md_info, finished_key, md_size, transcript, md_size, dst ); |
| if( ret != 0 ) |
| goto exit; |
| |
| exit: |
| |
| mbedtls_platform_zeroize( finished_key, sizeof( finished_key ) ); |
| return( ret ); |
| } |
| |
| int mbedtls_ssl_tls1_3_create_psk_binder( mbedtls_ssl_context *ssl, |
| const mbedtls_md_type_t md_type, |
| unsigned char const *psk, size_t psk_len, |
| int psk_type, |
| unsigned char const *transcript, |
| unsigned char *result ) |
| { |
| int ret = 0; |
| unsigned char binder_key[MBEDTLS_MD_MAX_SIZE]; |
| unsigned char early_secret[MBEDTLS_MD_MAX_SIZE]; |
| mbedtls_md_info_t const *md_info = mbedtls_md_info_from_type( md_type ); |
| size_t const md_size = mbedtls_md_get_size( md_info ); |
| |
| #if !defined(MBEDTLS_DEBUG_C) |
| ssl = NULL; /* make sure we don't use it except for debug */ |
| ((void) ssl); |
| #endif |
| |
| /* We should never call this function with an unknown hash, |
| * but add an assertion anyway. */ |
| if( md_info == 0 ) |
| return( MBEDTLS_ERR_SSL_INTERNAL_ERROR ); |
| |
| /* |
| * 0 |
| * | |
| * v |
| * PSK -> HKDF-Extract = Early Secret |
| * | |
| * +-----> Derive-Secret(., "ext binder" | "res binder", "") |
| * | = binder_key |
| * v |
| */ |
| |
| ret = mbedtls_ssl_tls1_3_evolve_secret( md_type, |
| NULL, /* Old secret */ |
| psk, psk_len, /* Input */ |
| early_secret ); |
| if( ret != 0 ) |
| { |
| MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ssl_tls1_3_evolve_secret", ret ); |
| goto exit; |
| } |
| |
| if( psk_type == MBEDTLS_SSL_TLS1_3_PSK_RESUMPTION ) |
| { |
| ret = mbedtls_ssl_tls1_3_derive_secret( md_type, |
| early_secret, md_size, |
| MBEDTLS_SSL_TLS1_3_LBL_WITH_LEN( res_binder ), |
| NULL, 0, MBEDTLS_SSL_TLS1_3_CONTEXT_UNHASHED, |
| binder_key, md_size ); |
| MBEDTLS_SSL_DEBUG_MSG( 4, ( "Derive Early Secret with 'res binder'" ) ); |
| } |
| else |
| { |
| ret = mbedtls_ssl_tls1_3_derive_secret( md_type, |
| early_secret, md_size, |
| MBEDTLS_SSL_TLS1_3_LBL_WITH_LEN( ext_binder ), |
| NULL, 0, MBEDTLS_SSL_TLS1_3_CONTEXT_UNHASHED, |
| binder_key, md_size ); |
| MBEDTLS_SSL_DEBUG_MSG( 4, ( "Derive Early Secret with 'ext binder'" ) ); |
| } |
| |
| if( ret != 0 ) |
| { |
| MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ssl_tls1_3_derive_secret", ret ); |
| goto exit; |
| } |
| |
| /* |
| * The binding_value is computed in the same way as the Finished message |
| * but with the BaseKey being the binder_key. |
| */ |
| |
| ret = ssl_tls1_3_calc_finished_core( md_type, binder_key, transcript, result ); |
| if( ret != 0 ) |
| goto exit; |
| |
| MBEDTLS_SSL_DEBUG_BUF( 3, "psk binder", result, md_size ); |
| |
| exit: |
| |
| mbedtls_platform_zeroize( early_secret, sizeof( early_secret ) ); |
| mbedtls_platform_zeroize( binder_key, sizeof( binder_key ) ); |
| return( ret ); |
| } |
| |
| #endif /* MBEDTLS_SSL_PROTO_TLS1_3_EXPERIMENTAL */ |
