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/* hmac-md5.c -- hashed message authentication codes
Copyright (C) 2005, 2006 Free Software Foundation, Inc.
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2, or (at your option)
any later version.
This program 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 General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software Foundation,
Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */
/* Written by Simon Josefsson. */
#include <config.h>
#include "hmac.h"
#include "memxor.h"
#include "md5.h"
#include <string.h>
#define IPAD 0x36
#define OPAD 0x5c
int
hmac_md5 (const void *key, size_t keylen,
const void *in, size_t inlen, void *resbuf)
{
struct md5_ctx inner;
struct md5_ctx outer;
char optkeybuf[16];
char block[64];
char innerhash[16];
/* Reduce the key's size, so that it becomes <= 64 bytes large. */
if (keylen > 64)
{
struct md5_ctx keyhash;
md5_init_ctx (&keyhash);
md5_process_bytes (key, keylen, &keyhash);
md5_finish_ctx (&keyhash, optkeybuf);
key = optkeybuf;
keylen = 16;
}
/* Compute INNERHASH from KEY and IN. */
md5_init_ctx (&inner);
memset (block, IPAD, sizeof (block));
memxor (block, key, keylen);
md5_process_block (block, 64, &inner);
md5_process_bytes (in, inlen, &inner);
md5_finish_ctx (&inner, innerhash);
/* Compute result from KEY and INNERHASH. */
md5_init_ctx (&outer);
memset (block, OPAD, sizeof (block));
memxor (block, key, keylen);
md5_process_block (block, 64, &outer);
md5_process_bytes (innerhash, 16, &outer);
md5_finish_ctx (&outer, resbuf);
return 0;
}
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