mac.c revision 149749 
1/*
2 * Copyright (c) 2001 Markus Friedl.  All rights reserved.
3 *
4 * Redistribution and use in source and binary forms, with or without
5 * modification, are permitted provided that the following conditions
6 * are met:
7 * 1. Redistributions of source code must retain the above copyright
8 *    notice, this list of conditions and the following disclaimer.
9 * 2. Redistributions in binary form must reproduce the above copyright
10 *    notice, this list of conditions and the following disclaimer in the
11 *    documentation and/or other materials provided with the distribution.
12 *
13 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
14 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
15 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
16 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
17 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
18 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
19 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
20 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
21 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
22 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
23 */
24
25#include "includes.h"
26RCSID("$OpenBSD: mac.c,v 1.7 2005/06/17 02:44:32 djm Exp $");
27
28#include <openssl/hmac.h>
29
30#include "xmalloc.h"
31#include "getput.h"
32#include "log.h"
33#include "cipher.h"
34#include "kex.h"
35#include "mac.h"
36
37struct {
38	char		*name;
39	const EVP_MD *	(*mdfunc)(void);
40	int		truncatebits;	/* truncate digest if != 0 */
41} macs[] = {
42	{ "hmac-sha1",			EVP_sha1, 0, },
43	{ "hmac-sha1-96",		EVP_sha1, 96 },
44	{ "hmac-md5",			EVP_md5, 0 },
45	{ "hmac-md5-96",		EVP_md5, 96 },
46	{ "hmac-ripemd160",		EVP_ripemd160, 0 },
47	{ "hmac-ripemd160@openssh.com",	EVP_ripemd160, 0 },
48	{ NULL,				NULL, 0 }
49};
50
51int
52mac_init(Mac *mac, char *name)
53{
54	int i, evp_len;
55
56	for (i = 0; macs[i].name; i++) {
57		if (strcmp(name, macs[i].name) == 0) {
58			if (mac != NULL) {
59				mac->md = (*macs[i].mdfunc)();
60				if ((evp_len = EVP_MD_size(mac->md)) <= 0)
61					fatal("mac %s len %d", name, evp_len);
62				mac->key_len = mac->mac_len = (u_int)evp_len;
63				if (macs[i].truncatebits != 0)
64					mac->mac_len = macs[i].truncatebits/8;
65			}
66			debug2("mac_init: found %s", name);
67			return (0);
68		}
69	}
70	debug2("mac_init: unknown %s", name);
71	return (-1);
72}
73
74u_char *
75mac_compute(Mac *mac, u_int32_t seqno, u_char *data, int datalen)
76{
77	HMAC_CTX c;
78	static u_char m[EVP_MAX_MD_SIZE];
79	u_char b[4];
80
81	if (mac->key == NULL)
82		fatal("mac_compute: no key");
83	if (mac->mac_len > sizeof(m))
84		fatal("mac_compute: mac too long");
85	HMAC_Init(&c, mac->key, mac->key_len, mac->md);
86	PUT_32BIT(b, seqno);
87	HMAC_Update(&c, b, sizeof(b));
88	HMAC_Update(&c, data, datalen);
89	HMAC_Final(&c, m, NULL);
90	HMAC_cleanup(&c);
91	return (m);
92}
93
94/* XXX copied from ciphers_valid */
95#define	MAC_SEP	","
96int
97mac_valid(const char *names)
98{
99	char *maclist, *cp, *p;
100
101	if (names == NULL || strcmp(names, "") == 0)
102		return (0);
103	maclist = cp = xstrdup(names);
104	for ((p = strsep(&cp, MAC_SEP)); p && *p != '\0';
105	    (p = strsep(&cp, MAC_SEP))) {
106		if (mac_init(NULL, p) < 0) {
107			debug("bad mac %s [%s]", p, names);
108			xfree(maclist);
109			return (0);
110		} else {
111			debug3("mac ok: %s [%s]", p, names);
112		}
113	}
114	debug3("macs ok: [%s]", names);
115	xfree(maclist);
116	return (1);
117}
118