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/**
* License: 2-clause BSD
*
* Copyright (c) 2016, Martin Belanger <nitram_67@hotmail.com>
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* 1. Redistributions of source code must retain the above copyright notice, this
* list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright notice,
* this list of conditions and the following disclaimer in the documentation
* and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR
* ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
*/
#include <string.h> /* memset(), memcpy() */
#include "md5.h"
#include "hmac.h"
struct padding
{
uint8_t inner[65]; /* inner padding - key XORd with ipad */
uint8_t outer[65]; /* outer padding - key XORd with opad */
};
static void init_pad(struct padding * pad, const uint8_t *key, size_t key_len)
{
size_t i;
uint8_t tmpkey[16];
if (key_len > 64)
{
MD5_CTX tmpctx;
MD5Init(&tmpctx);
MD5Update(&tmpctx, key, key_len);
MD5Final(tmpkey, &tmpctx);
key = tmpkey;
key_len = 16;
}
memset(pad, 0, sizeof(*pad));
memcpy(pad->inner, key, key_len);
memcpy(pad->outer, key, key_len);
for (i = 0; i < 64; i++)
{
pad->inner[i] ^= 0x36;
pad->outer[i] ^= 0x5c;
}
}
/**
* HMAC MD5 algorithm (RFC-2104)
*
* @author mbelanger (12/14/16)
*
* @param data - pointer to data to be processed
* @param data_len - length of data
* @param key - pointer to key
* @param key_len - length of key
* @param digest - caller digest to be filled in
*/
void hmac_md5(uint8_t *data, size_t data_len,
uint8_t *key, size_t key_len, uint8_t *digest)
{
MD5_CTX context;
struct padding pad;
init_pad(&pad, key, key_len);
/* inner MD5 */
MD5Init(&context);
MD5Update(&context, pad.inner, 64);
MD5Update(&context, data, data_len);
MD5Final(digest, &context);
/* outer MD5 */
MD5Init(&context);
MD5Update(&context, pad.outer, 64);
MD5Update(&context, digest, 16);
MD5Final(digest, &context);
}
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