pppd/chap-md5.c

   1 /*
   2  * chap-md5.c - New CHAP/MD5 implementation.
   3  *
   4  * Copyright (c) 2003 Paul Mackerras. All rights reserved.
   5  *
   6  * Redistribution and use in source and binary forms, with or without
   7  * modification, are permitted provided that the following conditions
   8  * are met:
   9  *
  10  * 1. Redistributions of source code must retain the above copyright
  11  *    notice, this list of conditions and the following disclaimer.
  12  *
  13  * 2. The name(s) of the authors of this software must not be used to
  14  *    endorse or promote products derived from this software without
  15  *    prior written permission.
  16  *
  17  * 3. Redistributions of any form whatsoever must retain the following
  18  *    acknowledgment:
  19  *    "This product includes software developed by Paul Mackerras
  20  *     <paulus@samba.org>".
  21  *
  22  * THE AUTHORS OF THIS SOFTWARE DISCLAIM ALL WARRANTIES WITH REGARD TO
  23  * THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
  24  * AND FITNESS, IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY
  25  * SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
  26  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN
  27  * AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING
  28  * OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  29  */
  30
  31 #define RCSID   "$Id: chap-md5.c,v 1.4 2004/11/09 22:39:25 paulus Exp $"
  32
  33 #include <stdlib.h>
  34 #include <string.h>
  35 #include "pppd.h"
  36 #include "chap-new.h"
  37 #include "chap-md5.h"
  38 #include "magic.h"
  39 #include "md5.h"
  40
  41 #define MD5_HASH_SIZE           16
  42 #define MD5_MIN_CHALLENGE       16
  43 #define MD5_MAX_CHALLENGE       24
  44
  45 static void
  46 chap_md5_generate_challenge(unsigned char *cp)
  47 {
  48         int clen;
  49
  50         clen = (int)(drand48() * (MD5_MAX_CHALLENGE - MD5_MIN_CHALLENGE))
  51                 + MD5_MIN_CHALLENGE;
  52         *cp++ = clen;
  53         random_bytes(cp, clen);
  54 }
  55
  56 static int
  57 chap_md5_verify_response(int id, char *name,
  58                          unsigned char *secret, int secret_len,
  59                          unsigned char *challenge, unsigned char *response,
  60                          char *message, int message_space)
  61 {
  62         MD5_CTX ctx;
  63         unsigned char idbyte = id;
  64         unsigned char hash[MD5_HASH_SIZE];
  65         int challenge_len, response_len;
  66
  67         challenge_len = *challenge++;
  68         response_len = *response++;
  69         if (response_len == MD5_HASH_SIZE) {
  70                 /* Generate hash of ID, secret, challenge */
  71                 MD5_Init(&ctx);
  72                 MD5_Update(&ctx, &idbyte, 1);
  73                 MD5_Update(&ctx, secret, secret_len);
  74                 MD5_Update(&ctx, challenge, challenge_len);
  75                 MD5_Final(hash, &ctx);
  76
  77                 /* Test if our hash matches the peer's response */
  78                 if (memcmp(hash, response, MD5_HASH_SIZE) == 0) {
  79                         slprintf(message, message_space, "Access granted");
  80                         return 1;
  81                 }
  82         }
  83         slprintf(message, message_space, "Access denied");
  84         return 0;
  85 }
  86
  87 static void
  88 chap_md5_make_response(unsigned char *response, int id, char *our_name,
  89                        unsigned char *challenge, char *secret, int secret_len,
  90                        unsigned char *private)
  91 {
  92         MD5_CTX ctx;
  93         unsigned char idbyte = id;
  94         int challenge_len = *challenge++;
  95
  96         MD5_Init(&ctx);
  97         MD5_Update(&ctx, &idbyte, 1);
  98         MD5_Update(&ctx, secret, secret_len);
  99         MD5_Update(&ctx, challenge, challenge_len);
 100         MD5_Final(&response[1], &ctx);
 101         response[0] = MD5_HASH_SIZE;
 102 }
 103
 104 static struct chap_digest_type md5_digest = {
 105         CHAP_MD5,               /* code */
 106         chap_md5_generate_challenge,
 107         chap_md5_verify_response,
 108         chap_md5_make_response,
 109         NULL,                   /* check_success */
 110         NULL,                   /* handle_failure */
 111 };
 112
 113 void
 114 chap_md5_init(void)
 115 {
 116         chap_register_digest(&md5_digest);
 117 }