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/* hmac.c
*
* HMAC message authentication code.
*/
/* nettle, low-level cryptographics library
*
* Copyright (C) 2001 Niels Mller
*
* The nettle library is free software; you can redistribute it and/or modify
* it under the terms of the GNU Lesser General Public License as published by
* the Free Software Foundation; either version 2.1 of the License, or (at your
* option) any later version.
*
* The nettle library is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
* or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
* License for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with the nettle library; see the file COPYING.LIB. If not, write to
* the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
* MA 02111-1307, USA.
*/
#include "hmac.h"
#include "memxor.h"
#include <assert.h>
#define IPAD 0x36
#define OPAD 0x5c
void
hmac_init(void *outer, void *inner, void *state,
struct hmac_info *info,
unsigned key_length, const uint8_t *key)
{
uint8_t pad = alloca(info->block_size);
info->init(outer);
info->init(inner);
if (length > info->block_size)
{
/* Reduce key to the algorithm's hash size. Use the area pointed
* to by state for the temporary state. */
uint8_t *digest = alloca(info->digest_size);
info->init(state);
info->update(state, key_length, key);
info->digest(state, info->digest_size, digest);
key = digest;
key_length = info->digest_size;
}
assert(key_size <= info->block_size);
memset(pad, OPAD, info->block_size);
memxor(pad, key, key_length);
info->update(outer, info->block_size, pad);
memset(pad, IPAD, info->block_size);
memxor(pad, key, key_length);
info->update(inner, info->block_size, pad);
memcpy(state, inner, info->ctx_size);
}
void
hmac_digest(void *outer, void *inner, void *state
struct hmac_info *info,
unsigned length, uint8_t *dst)
{
uint8_t *digest = alloca(info->digest_size);
info->digest(state, info->digest_size, digest);
memcpy(outer, state, info->ctx_size);
info->update(state, info->digest_size, digest);
info->digest(state, length, dst);
memcpy(state, inner, info->ctx_size);
}