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
chap_md5_generate_challenge(unsigned char * cp)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
chap_md5_verify_response(int id,char * name,unsigned char * secret,int secret_len,unsigned char * challenge,unsigned char * response,char * message,int message_space)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
chap_md5_make_response(unsigned char * response,int id,char * our_name,unsigned char * challenge,char * secret,int secret_len,unsigned char * private)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, (u_char *)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
chap_md5_init(void)114 chap_md5_init(void)
115 {
116 chap_register_digest(&md5_digest);
117 }
118