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
45static void
46chap_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
56static int
57chap_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
87static void
88chap_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
104static 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
113void
114chap_md5_init(void)
115{
116	chap_register_digest(&md5_digest);
117}
118