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/*
* This file is part of libESMTP, a library for submission of RFC 2822
* formatted electronic mail messages using the SMTP protocol described
* in RFC 2821.
*
* Copyright (C) 2001,2002 Brian Stafford <brian@stafford.uklinux.net>
*
* This 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.
*
* This 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 this library; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
#ifdef HAVE_CONFIG_H
#include <config.h>
#endif
#include <string.h>
#include <sys/types.h>
#include "hmacmd5.h"
#define PAD_SIZE 64
/*
* the HMAC_MD5 transform looks like:
*
* MD5(K XOR opad, MD5(K XOR ipad, challenge))
*
* where K is an n byte secret
* ipad is the byte 0x36 repeated 64 times
* opad is the byte 0x5c repeated 64 times
* and challenge is the data being protected
*/
/* Precompute HMAC-MD5 contexts from a secret
*/
void
hmac_md5_pre (const void *secret, size_t secret_len,
MD5_CTX *inner, MD5_CTX *outer)
{
unsigned char ipad[PAD_SIZE];
unsigned char opad[PAD_SIZE];
unsigned char tk[16];
int i;
/* If secret is longer than 64 bytes reset it to secret = MD5 (secret)
*/
if (secret_len > PAD_SIZE)
{
MD5_CTX tctx;
MD5_Init (&tctx);
MD5_Update (&tctx, secret, secret_len);
MD5_Final (tk, &tctx);
secret = tk;
secret_len = sizeof tk;
}
/* start out by storing secret in pads */
memcpy (ipad, secret, secret_len);
if (secret_len < sizeof ipad)
memset (ipad + secret_len, 0, sizeof ipad - secret_len);
memcpy (opad, secret, secret_len);
if (secret_len < sizeof opad)
memset (opad + secret_len, 0, sizeof opad - secret_len);
/* XOR secret with ipad and opad values */
for (i = 0; i < PAD_SIZE; i++)
{
ipad[i] ^= 0x36;
opad[i] ^= 0x5c;
}
/* perform inner MD5 */
MD5_Init (inner);
MD5_Update (inner, ipad, sizeof ipad);
/* perform outer MD5 */
MD5_Init (outer);
MD5_Update (outer, opad, sizeof opad);
}
/* Finalise HMAC-MD5 contexts from a challenge
*/
void
hmac_md5_post (const void *challenge, size_t challenge_len,
MD5_CTX *inner, MD5_CTX *outer, unsigned char digest[16])
{
unsigned char id[16];
/* perform inner MD5 */
MD5_Update (inner, challenge, challenge_len);
MD5_Final (id, inner);
/* perform outer MD5 */
MD5_Update (outer, id, sizeof id);
MD5_Final (digest, outer);
}
/* Digest a challenge and a secret.
*/
void
hmac_md5 (const void *challenge, size_t challenge_len,
const void *secret, size_t secret_len,
unsigned char digest[16])
{
MD5_CTX inner, outer;
hmac_md5_pre (secret, secret_len, &inner, &outer);
hmac_md5_post (challenge, challenge_len, &inner, &outer, digest);
}
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