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/*
* Off-the-Record Messaging Toolkit
* Copyright (C) 2004-2012 Ian Goldberg, Chris Alexander, Nikita Borisov
* <otr@cypherpunks.ca>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of version 2 of the GNU General Public License as
* published by the Free Software Foundation.
*
* 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
*/
/* system headers */
#include <stdio.h>
#include <stdlib.h>
/* libgcrypt headers */
#include <gcrypt.h>
/* Implementation of SHA1-HMAC. We're rolling our own just to
* double-check that the calls libotr makes to libgcrypt are in fact
* doing the right thing. */
void sha1hmac(unsigned char digest[20], unsigned char key[20],
unsigned char *data, size_t datalen)
{
unsigned char ipad[64], opad[64];
size_t i;
gcry_md_hd_t sha1;
gcry_error_t err;
unsigned char hash[20];
memset(ipad, 0, 64);
memset(opad, 0, 64);
memmove(ipad, key, 20);
memmove(opad, key, 20);
for(i=0;i<64;++i) {
ipad[i] ^= 0x36;
opad[i] ^= 0x5c;
}
err = gcry_md_open(&sha1, GCRY_MD_SHA1, 0);
if (err) {
fprintf(stderr, "Error: %s\n", gcry_strerror(err));
exit(1);
}
gcry_md_write(sha1, ipad, 64);
gcry_md_write(sha1, data, datalen);
memmove(hash, gcry_md_read(sha1, 0), 20);
gcry_md_reset(sha1);
gcry_md_write(sha1, opad, 64);
gcry_md_write(sha1, hash, 20);
memmove(digest, gcry_md_read(sha1, 0), 20);
gcry_md_close(sha1);
}