programs/pluto/cookie.c

   1 /* cookie generation/verification routines.
   2  * Copyright (C) 1997 Angelos D. Keromytis.
   3  * Copyright (C) 1998-2002  D. Hugh Redelmeier.
   4  *
   5  * This program is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License as published by the
   7  * Free Software Foundation; either version 2 of the License, or (at your
   8  * option) any later version.  See <http://www.fsf.org/copyleft/gpl.txt>.
   9  *
  10  * This program is distributed in the hope that it will be useful, but
  11  * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
  12  * or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  13  * for more details.
  14  *
  15  * RCSID $Id: cookie.c,v 1.2 2005/08/17 16:38:20 as Exp $
  16  */
  17
  18 #include <stdio.h>
  19 #include <string.h>
  20 #include <sys/types.h>
  21 #include <sys/socket.h>
  22 #include <netinet/in.h>
  23
  24 #include <freeswan.h>
  25
  26 #include "constants.h"
  27 #include "defs.h"
  28 #include "sha1.h"
  29 #include "rnd.h"
  30 #include "cookie.h"
  31
  32 const u_char zero_cookie[COOKIE_SIZE];  /* guaranteed 0 */
  33
  34 /* Generate a cookie.
  35  * First argument is true if we're to create an Initiator cookie.
  36  * Length SHOULD be a multiple of sizeof(u_int32_t).
  37  */
  38 void
  39 get_cookie(bool initiator, u_int8_t *cookie, int length, const ip_address *addr)
  40 {
  41     u_char buffer[SHA1_DIGEST_SIZE];
  42     SHA1_CTX ctx;
  43
  44     do {
  45         if (initiator)
  46         {
  47             get_rnd_bytes(cookie, length);
  48         }
  49         else  /* Responder cookie */
  50         {
  51             /* This looks as good as any way */
  52             size_t addr_length;
  53             static u_int32_t counter = 0;
  54             unsigned char addr_buff[
  55                 sizeof(union {struct in_addr A; struct in6_addr B;})];
  56
  57             addr_length = addrbytesof(addr, addr_buff, sizeof(addr_buff));
  58             SHA1Init(&ctx);
  59             SHA1Update(&ctx, addr_buff, addr_length);
  60             SHA1Update(&ctx, secret_of_the_day, sizeof(secret_of_the_day));
  61             counter++;
  62             SHA1Update(&ctx, (const void *) &counter, sizeof(counter));
  63             SHA1Final(buffer, &ctx);
  64             memcpy(cookie, buffer, length);
  65         }
  66     } while (is_zero_cookie(cookie));   /* probably never loops */
  67 }