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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