Kev Mann / mbed-dev-OS5_10_4

features/mbedtls/src/hkdf.c@0:38ceb79fef03, 2018-11-28 (annotated)

Committer:
kevman
Date:
Wed Nov 28 15:10:15 2018 +0000
Revision:
0:38ceb79fef03
RTC modified

Who changed what in which revision?

UserRevisionLine numberNew contents of line
kevman 0:38ceb79fef03 1 /*
kevman 0:38ceb79fef03 2 * HKDF implementation -- RFC 5869
kevman 0:38ceb79fef03 3 *
kevman 0:38ceb79fef03 4 * Copyright (C) 2016-2018, ARM Limited, All Rights Reserved
kevman 0:38ceb79fef03 5 * SPDX-License-Identifier: Apache-2.0
kevman 0:38ceb79fef03 6 *
kevman 0:38ceb79fef03 7 * Licensed under the Apache License, Version 2.0 (the "License"); you may
kevman 0:38ceb79fef03 8 * not use this file except in compliance with the License.
kevman 0:38ceb79fef03 9 * You may obtain a copy of the License at
kevman 0:38ceb79fef03 10 *
kevman 0:38ceb79fef03 11 * http://www.apache.org/licenses/LICENSE-2.0
kevman 0:38ceb79fef03 12 *
kevman 0:38ceb79fef03 13 * Unless required by applicable law or agreed to in writing, software
kevman 0:38ceb79fef03 14 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
kevman 0:38ceb79fef03 15 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
kevman 0:38ceb79fef03 16 * See the License for the specific language governing permissions and
kevman 0:38ceb79fef03 17 * limitations under the License.
kevman 0:38ceb79fef03 18 *
kevman 0:38ceb79fef03 19 * This file is part of mbed TLS (https://tls.mbed.org)
kevman 0:38ceb79fef03 20 */
kevman 0:38ceb79fef03 21 #if !defined(MBEDTLS_CONFIG_FILE)
kevman 0:38ceb79fef03 22 #include "mbedtls/config.h"
kevman 0:38ceb79fef03 23 #else
kevman 0:38ceb79fef03 24 #include MBEDTLS_CONFIG_FILE
kevman 0:38ceb79fef03 25 #endif
kevman 0:38ceb79fef03 26
kevman 0:38ceb79fef03 27 #if defined(MBEDTLS_HKDF_C)
kevman 0:38ceb79fef03 28
kevman 0:38ceb79fef03 29 #include <string.h>
kevman 0:38ceb79fef03 30 #include "mbedtls/hkdf.h"
kevman 0:38ceb79fef03 31 #include "mbedtls/platform_util.h"
kevman 0:38ceb79fef03 32
kevman 0:38ceb79fef03 33 int mbedtls_hkdf( const mbedtls_md_info_t *md, const unsigned char *salt,
kevman 0:38ceb79fef03 34 size_t salt_len, const unsigned char *ikm, size_t ikm_len,
kevman 0:38ceb79fef03 35 const unsigned char *info, size_t info_len,
kevman 0:38ceb79fef03 36 unsigned char *okm, size_t okm_len )
kevman 0:38ceb79fef03 37 {
kevman 0:38ceb79fef03 38 int ret;
kevman 0:38ceb79fef03 39 unsigned char prk[MBEDTLS_MD_MAX_SIZE];
kevman 0:38ceb79fef03 40
kevman 0:38ceb79fef03 41 ret = mbedtls_hkdf_extract( md, salt, salt_len, ikm, ikm_len, prk );
kevman 0:38ceb79fef03 42
kevman 0:38ceb79fef03 43 if( ret == 0 )
kevman 0:38ceb79fef03 44 {
kevman 0:38ceb79fef03 45 ret = mbedtls_hkdf_expand( md, prk, mbedtls_md_get_size( md ),
kevman 0:38ceb79fef03 46 info, info_len, okm, okm_len );
kevman 0:38ceb79fef03 47 }
kevman 0:38ceb79fef03 48
kevman 0:38ceb79fef03 49 mbedtls_platform_zeroize( prk, sizeof( prk ) );
kevman 0:38ceb79fef03 50
kevman 0:38ceb79fef03 51 return( ret );
kevman 0:38ceb79fef03 52 }
kevman 0:38ceb79fef03 53
kevman 0:38ceb79fef03 54 int mbedtls_hkdf_extract( const mbedtls_md_info_t *md,
kevman 0:38ceb79fef03 55 const unsigned char *salt, size_t salt_len,
kevman 0:38ceb79fef03 56 const unsigned char *ikm, size_t ikm_len,
kevman 0:38ceb79fef03 57 unsigned char *prk )
kevman 0:38ceb79fef03 58 {
kevman 0:38ceb79fef03 59 unsigned char null_salt[MBEDTLS_MD_MAX_SIZE] = { '\0' };
kevman 0:38ceb79fef03 60
kevman 0:38ceb79fef03 61 if( salt == NULL )
kevman 0:38ceb79fef03 62 {
kevman 0:38ceb79fef03 63 size_t hash_len;
kevman 0:38ceb79fef03 64
kevman 0:38ceb79fef03 65 if( salt_len != 0 )
kevman 0:38ceb79fef03 66 {
kevman 0:38ceb79fef03 67 return MBEDTLS_ERR_HKDF_BAD_INPUT_DATA;
kevman 0:38ceb79fef03 68 }
kevman 0:38ceb79fef03 69
kevman 0:38ceb79fef03 70 hash_len = mbedtls_md_get_size( md );
kevman 0:38ceb79fef03 71
kevman 0:38ceb79fef03 72 if( hash_len == 0 )
kevman 0:38ceb79fef03 73 {
kevman 0:38ceb79fef03 74 return MBEDTLS_ERR_HKDF_BAD_INPUT_DATA;
kevman 0:38ceb79fef03 75 }
kevman 0:38ceb79fef03 76
kevman 0:38ceb79fef03 77 salt = null_salt;
kevman 0:38ceb79fef03 78 salt_len = hash_len;
kevman 0:38ceb79fef03 79 }
kevman 0:38ceb79fef03 80
kevman 0:38ceb79fef03 81 return( mbedtls_md_hmac( md, salt, salt_len, ikm, ikm_len, prk ) );
kevman 0:38ceb79fef03 82 }
kevman 0:38ceb79fef03 83
kevman 0:38ceb79fef03 84 int mbedtls_hkdf_expand( const mbedtls_md_info_t *md, const unsigned char *prk,
kevman 0:38ceb79fef03 85 size_t prk_len, const unsigned char *info,
kevman 0:38ceb79fef03 86 size_t info_len, unsigned char *okm, size_t okm_len )
kevman 0:38ceb79fef03 87 {
kevman 0:38ceb79fef03 88 size_t hash_len;
kevman 0:38ceb79fef03 89 size_t where = 0;
kevman 0:38ceb79fef03 90 size_t n;
kevman 0:38ceb79fef03 91 size_t t_len = 0;
kevman 0:38ceb79fef03 92 size_t i;
kevman 0:38ceb79fef03 93 int ret = 0;
kevman 0:38ceb79fef03 94 mbedtls_md_context_t ctx;
kevman 0:38ceb79fef03 95 unsigned char t[MBEDTLS_MD_MAX_SIZE];
kevman 0:38ceb79fef03 96
kevman 0:38ceb79fef03 97 if( okm == NULL )
kevman 0:38ceb79fef03 98 {
kevman 0:38ceb79fef03 99 return( MBEDTLS_ERR_HKDF_BAD_INPUT_DATA );
kevman 0:38ceb79fef03 100 }
kevman 0:38ceb79fef03 101
kevman 0:38ceb79fef03 102 hash_len = mbedtls_md_get_size( md );
kevman 0:38ceb79fef03 103
kevman 0:38ceb79fef03 104 if( prk_len < hash_len || hash_len == 0 )
kevman 0:38ceb79fef03 105 {
kevman 0:38ceb79fef03 106 return( MBEDTLS_ERR_HKDF_BAD_INPUT_DATA );
kevman 0:38ceb79fef03 107 }
kevman 0:38ceb79fef03 108
kevman 0:38ceb79fef03 109 if( info == NULL )
kevman 0:38ceb79fef03 110 {
kevman 0:38ceb79fef03 111 info = (const unsigned char *) "";
kevman 0:38ceb79fef03 112 info_len = 0;
kevman 0:38ceb79fef03 113 }
kevman 0:38ceb79fef03 114
kevman 0:38ceb79fef03 115 n = okm_len / hash_len;
kevman 0:38ceb79fef03 116
kevman 0:38ceb79fef03 117 if( (okm_len % hash_len) != 0 )
kevman 0:38ceb79fef03 118 {
kevman 0:38ceb79fef03 119 n++;
kevman 0:38ceb79fef03 120 }
kevman 0:38ceb79fef03 121
kevman 0:38ceb79fef03 122 /*
kevman 0:38ceb79fef03 123 * Per RFC 5869 Section 2.3, okm_len must not exceed
kevman 0:38ceb79fef03 124 * 255 times the hash length
kevman 0:38ceb79fef03 125 */
kevman 0:38ceb79fef03 126 if( n > 255 )
kevman 0:38ceb79fef03 127 {
kevman 0:38ceb79fef03 128 return( MBEDTLS_ERR_HKDF_BAD_INPUT_DATA );
kevman 0:38ceb79fef03 129 }
kevman 0:38ceb79fef03 130
kevman 0:38ceb79fef03 131 mbedtls_md_init( &ctx );
kevman 0:38ceb79fef03 132
kevman 0:38ceb79fef03 133 if( (ret = mbedtls_md_setup( &ctx, md, 1) ) != 0 )
kevman 0:38ceb79fef03 134 {
kevman 0:38ceb79fef03 135 goto exit;
kevman 0:38ceb79fef03 136 }
kevman 0:38ceb79fef03 137
kevman 0:38ceb79fef03 138 /*
kevman 0:38ceb79fef03 139 * Compute T = T(1) | T(2) | T(3) | ... | T(N)
kevman 0:38ceb79fef03 140 * Where T(N) is defined in RFC 5869 Section 2.3
kevman 0:38ceb79fef03 141 */
kevman 0:38ceb79fef03 142 for( i = 1; i <= n; i++ )
kevman 0:38ceb79fef03 143 {
kevman 0:38ceb79fef03 144 size_t num_to_copy;
kevman 0:38ceb79fef03 145 unsigned char c = i & 0xff;
kevman 0:38ceb79fef03 146
kevman 0:38ceb79fef03 147 ret = mbedtls_md_hmac_starts( &ctx, prk, prk_len );
kevman 0:38ceb79fef03 148 if( ret != 0 )
kevman 0:38ceb79fef03 149 {
kevman 0:38ceb79fef03 150 goto exit;
kevman 0:38ceb79fef03 151 }
kevman 0:38ceb79fef03 152
kevman 0:38ceb79fef03 153 ret = mbedtls_md_hmac_update( &ctx, t, t_len );
kevman 0:38ceb79fef03 154 if( ret != 0 )
kevman 0:38ceb79fef03 155 {
kevman 0:38ceb79fef03 156 goto exit;
kevman 0:38ceb79fef03 157 }
kevman 0:38ceb79fef03 158
kevman 0:38ceb79fef03 159 ret = mbedtls_md_hmac_update( &ctx, info, info_len );
kevman 0:38ceb79fef03 160 if( ret != 0 )
kevman 0:38ceb79fef03 161 {
kevman 0:38ceb79fef03 162 goto exit;
kevman 0:38ceb79fef03 163 }
kevman 0:38ceb79fef03 164
kevman 0:38ceb79fef03 165 /* The constant concatenated to the end of each T(n) is a single octet.
kevman 0:38ceb79fef03 166 * */
kevman 0:38ceb79fef03 167 ret = mbedtls_md_hmac_update( &ctx, &c, 1 );
kevman 0:38ceb79fef03 168 if( ret != 0 )
kevman 0:38ceb79fef03 169 {
kevman 0:38ceb79fef03 170 goto exit;
kevman 0:38ceb79fef03 171 }
kevman 0:38ceb79fef03 172
kevman 0:38ceb79fef03 173 ret = mbedtls_md_hmac_finish( &ctx, t );
kevman 0:38ceb79fef03 174 if( ret != 0 )
kevman 0:38ceb79fef03 175 {
kevman 0:38ceb79fef03 176 goto exit;
kevman 0:38ceb79fef03 177 }
kevman 0:38ceb79fef03 178
kevman 0:38ceb79fef03 179 num_to_copy = i != n ? hash_len : okm_len - where;
kevman 0:38ceb79fef03 180 memcpy( okm + where, t, num_to_copy );
kevman 0:38ceb79fef03 181 where += hash_len;
kevman 0:38ceb79fef03 182 t_len = hash_len;
kevman 0:38ceb79fef03 183 }
kevman 0:38ceb79fef03 184
kevman 0:38ceb79fef03 185 exit:
kevman 0:38ceb79fef03 186 mbedtls_md_free( &ctx );
kevman 0:38ceb79fef03 187 mbedtls_platform_zeroize( t, sizeof( t ) );
kevman 0:38ceb79fef03 188
kevman 0:38ceb79fef03 189 return( ret );
kevman 0:38ceb79fef03 190 }
kevman 0:38ceb79fef03 191
kevman 0:38ceb79fef03 192 #endif /* MBEDTLS_HKDF_C */