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sign.c

/* Distributed Checksum Clearinghouse
 *
 * message authentication
 *
 * Copyright (c) 2005 by Rhyolite Software
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND RHYOLITE SOFTWARE DISCLAIMS ALL
 * WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL RHYOLITE SOFTWARE
 * BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES
 * OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
 * WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION,
 * ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
 * SOFTWARE.
 *
 * Rhyolite Software DCC 1.2.74-1.9 $Revision$
 */

#include "dcc_defs.h"
#include "dcc_md5.h"
#include <string.h>


/* sign a DCC packet */
void
dcc_sign(const char *passwd,
       int passwd_len,
       void *pkt,
       u_int pkt_len)               /* including signature */
{
      MD5_CTX ctx;

      MD5Init(&ctx);
      MD5Update(&ctx, passwd, passwd_len);
      MD5Update(&ctx, pkt, pkt_len-sizeof(DCC_SIGNATURE));
      MD5Final(&((u_char*)pkt)[pkt_len-sizeof(DCC_SIGNATURE)], &ctx);
}



/* check the signature of a DCC packet */
u_char                              /* 0=forgery, 1=good signature */
dcc_ck_signature(const char *passwd,
             int passwd_len,
             const void *pkt,
             u_int pkt_len)         /* including signature */
{
      MD5_CTX ctx;
      DCC_SIGNATURE signature;

      MD5Init(&ctx);
      MD5Update(&ctx, passwd, passwd_len);
      MD5Update(&ctx, pkt, pkt_len-sizeof(DCC_SIGNATURE));
      MD5Final(signature, &ctx);
      return !memcmp(signature, &((char*)pkt)[pkt_len-sizeof(DCC_SIGNATURE)],
                   sizeof(signature));
}

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