diff options
Diffstat (limited to 'lib/mbedtls-2.27.0/library/ssl_tls13_keys.c')
| -rw-r--r-- | lib/mbedtls-2.27.0/library/ssl_tls13_keys.c | 349 |
1 files changed, 349 insertions, 0 deletions
diff --git a/lib/mbedtls-2.27.0/library/ssl_tls13_keys.c b/lib/mbedtls-2.27.0/library/ssl_tls13_keys.c new file mode 100644 index 0000000..c39e032 --- /dev/null +++ b/lib/mbedtls-2.27.0/library/ssl_tls13_keys.c @@ -0,0 +1,349 @@ +/* + * 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 "mbedtls/ssl_internal.h" +#include "ssl_tls13_keys.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 ); +} + +#endif /* MBEDTLS_SSL_PROTO_TLS1_3_EXPERIMENTAL */ |