/* | |
* HKDF implementation -- RFC 5869 | |
* | |
* Copyright (C) 2016-2018, ARM Limited, All Rights Reserved | |
* 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) | |
*/ | |
#if !defined(MBEDTLS_CONFIG_FILE) | |
#include "mbedtls/config.h" | |
#else | |
#include MBEDTLS_CONFIG_FILE | |
#endif | |
#if defined(MBEDTLS_HKDF_C) | |
#include <string.h> | |
#include "mbedtls/hkdf.h" | |
#include "mbedtls/platform_util.h" | |
int mbedtls_hkdf( const mbedtls_md_info_t *md, const unsigned char *salt, | |
size_t salt_len, const unsigned char *ikm, size_t ikm_len, | |
const unsigned char *info, size_t info_len, | |
unsigned char *okm, size_t okm_len ) | |
{ | |
int ret; | |
unsigned char prk[MBEDTLS_MD_MAX_SIZE]; | |
ret = mbedtls_hkdf_extract( md, salt, salt_len, ikm, ikm_len, prk ); | |
if( ret == 0 ) | |
{ | |
ret = mbedtls_hkdf_expand( md, prk, mbedtls_md_get_size( md ), | |
info, info_len, okm, okm_len ); | |
} | |
mbedtls_platform_zeroize( prk, sizeof( prk ) ); | |
return( ret ); | |
} | |
int mbedtls_hkdf_extract( const mbedtls_md_info_t *md, | |
const unsigned char *salt, size_t salt_len, | |
const unsigned char *ikm, size_t ikm_len, | |
unsigned char *prk ) | |
{ | |
unsigned char null_salt[MBEDTLS_MD_MAX_SIZE] = { '\0' }; | |
if( salt == NULL ) | |
{ | |
size_t hash_len; | |
if( salt_len != 0 ) | |
{ | |
return MBEDTLS_ERR_HKDF_BAD_INPUT_DATA; | |
} | |
hash_len = mbedtls_md_get_size( md ); | |
if( hash_len == 0 ) | |
{ | |
return MBEDTLS_ERR_HKDF_BAD_INPUT_DATA; | |
} | |
salt = null_salt; | |
salt_len = hash_len; | |
} | |
return( mbedtls_md_hmac( md, salt, salt_len, ikm, ikm_len, prk ) ); | |
} | |
int mbedtls_hkdf_expand( const mbedtls_md_info_t *md, const unsigned char *prk, | |
size_t prk_len, const unsigned char *info, | |
size_t info_len, unsigned char *okm, size_t okm_len ) | |
{ | |
size_t hash_len; | |
size_t where = 0; | |
size_t n; | |
size_t t_len = 0; | |
size_t i; | |
int ret = 0; | |
mbedtls_md_context_t ctx; | |
unsigned char t[MBEDTLS_MD_MAX_SIZE]; | |
if( okm == NULL ) | |
{ | |
return( MBEDTLS_ERR_HKDF_BAD_INPUT_DATA ); | |
} | |
hash_len = mbedtls_md_get_size( md ); | |
if( prk_len < hash_len || hash_len == 0 ) | |
{ | |
return( MBEDTLS_ERR_HKDF_BAD_INPUT_DATA ); | |
} | |
if( info == NULL ) | |
{ | |
info = (const unsigned char *) ""; | |
info_len = 0; | |
} | |
n = okm_len / hash_len; | |
if( (okm_len % hash_len) != 0 ) | |
{ | |
n++; | |
} | |
/* | |
* Per RFC 5869 Section 2.3, okm_len must not exceed | |
* 255 times the hash length | |
*/ | |
if( n > 255 ) | |
{ | |
return( MBEDTLS_ERR_HKDF_BAD_INPUT_DATA ); | |
} | |
mbedtls_md_init( &ctx ); | |
if( (ret = mbedtls_md_setup( &ctx, md, 1) ) != 0 ) | |
{ | |
goto exit; | |
} | |
/* | |
* Compute T = T(1) | T(2) | T(3) | ... | T(N) | |
* Where T(N) is defined in RFC 5869 Section 2.3 | |
*/ | |
for( i = 1; i <= n; i++ ) | |
{ | |
size_t num_to_copy; | |
unsigned char c = i & 0xff; | |
ret = mbedtls_md_hmac_starts( &ctx, prk, prk_len ); | |
if( ret != 0 ) | |
{ | |
goto exit; | |
} | |
ret = mbedtls_md_hmac_update( &ctx, t, t_len ); | |
if( ret != 0 ) | |
{ | |
goto exit; | |
} | |
ret = mbedtls_md_hmac_update( &ctx, info, info_len ); | |
if( ret != 0 ) | |
{ | |
goto exit; | |
} | |
/* The constant concatenated to the end of each T(n) is a single octet. | |
* */ | |
ret = mbedtls_md_hmac_update( &ctx, &c, 1 ); | |
if( ret != 0 ) | |
{ | |
goto exit; | |
} | |
ret = mbedtls_md_hmac_finish( &ctx, t ); | |
if( ret != 0 ) | |
{ | |
goto exit; | |
} | |
num_to_copy = i != n ? hash_len : okm_len - where; | |
memcpy( okm + where, t, num_to_copy ); | |
where += hash_len; | |
t_len = hash_len; | |
} | |
exit: | |
mbedtls_md_free( &ctx ); | |
mbedtls_platform_zeroize( t, sizeof( t ) ); | |
return( ret ); | |
} | |
#endif /* MBEDTLS_HKDF_C */ |