mac.c revision 225736 
1/* $OpenBSD: mac.c,v 1.15 2008/06/13 00:51:47 dtucker Exp $ */
2/*
3 * Copyright (c) 2001 Markus Friedl.  All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 *    notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 *    notice, this list of conditions and the following disclaimer in the
12 *    documentation and/or other materials provided with the distribution.
13 *
14 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
15 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
16 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
17 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
18 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
19 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
20 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
21 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
22 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
23 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
24 */
25
26#include "includes.h"
27
28#include <sys/types.h>
29
30#include <openssl/hmac.h>
31
32#include <stdarg.h>
33#include <string.h>
34#include <signal.h>
35
36#include "xmalloc.h"
37#include "log.h"
38#include "cipher.h"
39#include "buffer.h"
40#include "key.h"
41#include "kex.h"
42#include "mac.h"
43#include "misc.h"
44
45#include "umac.h"
46
47#define SSH_EVP		1	/* OpenSSL EVP-based MAC */
48#define SSH_UMAC	2	/* UMAC (not integrated with OpenSSL) */
49
50struct {
51	char		*name;
52	int		type;
53	const EVP_MD *	(*mdfunc)(void);
54	int		truncatebits;	/* truncate digest if != 0 */
55	int		key_len;	/* just for UMAC */
56	int		len;		/* just for UMAC */
57} macs[] = {
58	{ "hmac-sha1",			SSH_EVP, EVP_sha1, 0, -1, -1 },
59	{ "hmac-sha1-96",		SSH_EVP, EVP_sha1, 96, -1, -1 },
60	{ "hmac-md5",			SSH_EVP, EVP_md5, 0, -1, -1 },
61	{ "hmac-md5-96",		SSH_EVP, EVP_md5, 96, -1, -1 },
62	{ "hmac-ripemd160",		SSH_EVP, EVP_ripemd160, 0, -1, -1 },
63	{ "hmac-ripemd160@openssh.com",	SSH_EVP, EVP_ripemd160, 0, -1, -1 },
64	{ "umac-64@openssh.com",	SSH_UMAC, NULL, 0, 128, 64 },
65	{ NULL,				0, NULL, 0, -1, -1 }
66};
67
68static void
69mac_setup_by_id(Mac *mac, int which)
70{
71	int evp_len;
72	mac->type = macs[which].type;
73	if (mac->type == SSH_EVP) {
74		mac->evp_md = (*macs[which].mdfunc)();
75		if ((evp_len = EVP_MD_size(mac->evp_md)) <= 0)
76			fatal("mac %s len %d", mac->name, evp_len);
77		mac->key_len = mac->mac_len = (u_int)evp_len;
78	} else {
79		mac->mac_len = macs[which].len / 8;
80		mac->key_len = macs[which].key_len / 8;
81		mac->umac_ctx = NULL;
82	}
83	if (macs[which].truncatebits != 0)
84		mac->mac_len = macs[which].truncatebits / 8;
85}
86
87int
88mac_setup(Mac *mac, char *name)
89{
90	int i;
91
92	for (i = 0; macs[i].name; i++) {
93		if (strcmp(name, macs[i].name) == 0) {
94			if (mac != NULL)
95				mac_setup_by_id(mac, i);
96			debug2("mac_setup: found %s", name);
97			return (0);
98		}
99	}
100	debug2("mac_setup: unknown %s", name);
101	return (-1);
102}
103
104int
105mac_init(Mac *mac)
106{
107	if (mac->key == NULL)
108		fatal("mac_init: no key");
109	switch (mac->type) {
110	case SSH_EVP:
111		if (mac->evp_md == NULL)
112			return -1;
113		HMAC_Init(&mac->evp_ctx, mac->key, mac->key_len, mac->evp_md);
114		return 0;
115	case SSH_UMAC:
116		mac->umac_ctx = umac_new(mac->key);
117		return 0;
118	default:
119		return -1;
120	}
121}
122
123u_char *
124mac_compute(Mac *mac, u_int32_t seqno, u_char *data, int datalen)
125{
126	static u_char m[EVP_MAX_MD_SIZE];
127	u_char b[4], nonce[8];
128
129	if (mac->mac_len > sizeof(m))
130		fatal("mac_compute: mac too long %u %lu",
131		    mac->mac_len, (u_long)sizeof(m));
132
133	switch (mac->type) {
134	case SSH_EVP:
135		put_u32(b, seqno);
136		/* reset HMAC context */
137		HMAC_Init(&mac->evp_ctx, NULL, 0, NULL);
138		HMAC_Update(&mac->evp_ctx, b, sizeof(b));
139		HMAC_Update(&mac->evp_ctx, data, datalen);
140		HMAC_Final(&mac->evp_ctx, m, NULL);
141		break;
142	case SSH_UMAC:
143		put_u64(nonce, seqno);
144		umac_update(mac->umac_ctx, data, datalen);
145		umac_final(mac->umac_ctx, m, nonce);
146		break;
147	default:
148		fatal("mac_compute: unknown MAC type");
149	}
150	return (m);
151}
152
153void
154mac_clear(Mac *mac)
155{
156	if (mac->type == SSH_UMAC) {
157		if (mac->umac_ctx != NULL)
158			umac_delete(mac->umac_ctx);
159	} else if (mac->evp_md != NULL)
160		HMAC_cleanup(&mac->evp_ctx);
161	mac->evp_md = NULL;
162	mac->umac_ctx = NULL;
163}
164
165/* XXX copied from ciphers_valid */
166#define	MAC_SEP	","
167int
168mac_valid(const char *names)
169{
170	char *maclist, *cp, *p;
171
172	if (names == NULL || strcmp(names, "") == 0)
173		return (0);
174	maclist = cp = xstrdup(names);
175	for ((p = strsep(&cp, MAC_SEP)); p && *p != '\0';
176	    (p = strsep(&cp, MAC_SEP))) {
177		if (mac_setup(NULL, p) < 0) {
178			debug("bad mac %s [%s]", p, names);
179			xfree(maclist);
180			return (0);
181		} else {
182			debug3("mac ok: %s [%s]", p, names);
183		}
184	}
185	debug3("macs ok: [%s]", names);
186	xfree(maclist);
187	return (1);
188}
189