mac.c revision 323129 
1/* $OpenBSD: mac.c,v 1.33 2016/07/08 03:44:42 djm 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 <string.h>
31#include <stdio.h>
32
33#include "digest.h"
34#include "hmac.h"
35#include "umac.h"
36#include "mac.h"
37#include "misc.h"
38#include "ssherr.h"
39#include "sshbuf.h"
40
41#include "openbsd-compat/openssl-compat.h"
42
43#define SSH_DIGEST	1	/* SSH_DIGEST_XXX */
44#define SSH_UMAC	2	/* UMAC (not integrated with OpenSSL) */
45#define SSH_UMAC128	3
46
47struct macalg {
48	char		*name;
49	int		type;
50	int		alg;
51	int		truncatebits;	/* truncate digest if != 0 */
52	int		key_len;	/* just for UMAC */
53	int		len;		/* just for UMAC */
54	int		etm;		/* Encrypt-then-MAC */
55};
56
57static const struct macalg macs[] = {
58	/* Encrypt-and-MAC (encrypt-and-authenticate) variants */
59	{ "hmac-sha1",				SSH_DIGEST, SSH_DIGEST_SHA1, 0, 0, 0, 0 },
60	{ "hmac-sha1-96",			SSH_DIGEST, SSH_DIGEST_SHA1, 96, 0, 0, 0 },
61#ifdef HAVE_EVP_SHA256
62	{ "hmac-sha2-256",			SSH_DIGEST, SSH_DIGEST_SHA256, 0, 0, 0, 0 },
63	{ "hmac-sha2-512",			SSH_DIGEST, SSH_DIGEST_SHA512, 0, 0, 0, 0 },
64#endif
65	{ "hmac-md5",				SSH_DIGEST, SSH_DIGEST_MD5, 0, 0, 0, 0 },
66	{ "hmac-md5-96",			SSH_DIGEST, SSH_DIGEST_MD5, 96, 0, 0, 0 },
67	{ "hmac-ripemd160",			SSH_DIGEST, SSH_DIGEST_RIPEMD160, 0, 0, 0, 0 },
68	{ "hmac-ripemd160@openssh.com",		SSH_DIGEST, SSH_DIGEST_RIPEMD160, 0, 0, 0, 0 },
69	{ "umac-64@openssh.com",		SSH_UMAC, 0, 0, 128, 64, 0 },
70	{ "umac-128@openssh.com",		SSH_UMAC128, 0, 0, 128, 128, 0 },
71
72	/* Encrypt-then-MAC variants */
73	{ "hmac-sha1-etm@openssh.com",		SSH_DIGEST, SSH_DIGEST_SHA1, 0, 0, 0, 1 },
74	{ "hmac-sha1-96-etm@openssh.com",	SSH_DIGEST, SSH_DIGEST_SHA1, 96, 0, 0, 1 },
75#ifdef HAVE_EVP_SHA256
76	{ "hmac-sha2-256-etm@openssh.com",	SSH_DIGEST, SSH_DIGEST_SHA256, 0, 0, 0, 1 },
77	{ "hmac-sha2-512-etm@openssh.com",	SSH_DIGEST, SSH_DIGEST_SHA512, 0, 0, 0, 1 },
78#endif
79	{ "hmac-md5-etm@openssh.com",		SSH_DIGEST, SSH_DIGEST_MD5, 0, 0, 0, 1 },
80	{ "hmac-md5-96-etm@openssh.com",	SSH_DIGEST, SSH_DIGEST_MD5, 96, 0, 0, 1 },
81	{ "hmac-ripemd160-etm@openssh.com",	SSH_DIGEST, SSH_DIGEST_RIPEMD160, 0, 0, 0, 1 },
82	{ "umac-64-etm@openssh.com",		SSH_UMAC, 0, 0, 128, 64, 1 },
83	{ "umac-128-etm@openssh.com",		SSH_UMAC128, 0, 0, 128, 128, 1 },
84
85	{ NULL,					0, 0, 0, 0, 0, 0 }
86};
87
88/* Returns a list of supported MACs separated by the specified char. */
89char *
90mac_alg_list(char sep)
91{
92	char *ret = NULL, *tmp;
93	size_t nlen, rlen = 0;
94	const struct macalg *m;
95
96	for (m = macs; m->name != NULL; m++) {
97		if (ret != NULL)
98			ret[rlen++] = sep;
99		nlen = strlen(m->name);
100		if ((tmp = realloc(ret, rlen + nlen + 2)) == NULL) {
101			free(ret);
102			return NULL;
103		}
104		ret = tmp;
105		memcpy(ret + rlen, m->name, nlen + 1);
106		rlen += nlen;
107	}
108	return ret;
109}
110
111static int
112mac_setup_by_alg(struct sshmac *mac, const struct macalg *macalg)
113{
114	mac->type = macalg->type;
115	if (mac->type == SSH_DIGEST) {
116		if ((mac->hmac_ctx = ssh_hmac_start(macalg->alg)) == NULL)
117			return SSH_ERR_ALLOC_FAIL;
118		mac->key_len = mac->mac_len = ssh_hmac_bytes(macalg->alg);
119	} else {
120		mac->mac_len = macalg->len / 8;
121		mac->key_len = macalg->key_len / 8;
122		mac->umac_ctx = NULL;
123	}
124	if (macalg->truncatebits != 0)
125		mac->mac_len = macalg->truncatebits / 8;
126	mac->etm = macalg->etm;
127	return 0;
128}
129
130int
131mac_setup(struct sshmac *mac, char *name)
132{
133	const struct macalg *m;
134
135	for (m = macs; m->name != NULL; m++) {
136		if (strcmp(name, m->name) != 0)
137			continue;
138		if (mac != NULL)
139			return mac_setup_by_alg(mac, m);
140		return 0;
141	}
142	return SSH_ERR_INVALID_ARGUMENT;
143}
144
145int
146mac_init(struct sshmac *mac)
147{
148	if (mac->key == NULL)
149		return SSH_ERR_INVALID_ARGUMENT;
150	switch (mac->type) {
151	case SSH_DIGEST:
152		if (mac->hmac_ctx == NULL ||
153		    ssh_hmac_init(mac->hmac_ctx, mac->key, mac->key_len) < 0)
154			return SSH_ERR_INVALID_ARGUMENT;
155		return 0;
156	case SSH_UMAC:
157		if ((mac->umac_ctx = umac_new(mac->key)) == NULL)
158			return SSH_ERR_ALLOC_FAIL;
159		return 0;
160	case SSH_UMAC128:
161		if ((mac->umac_ctx = umac128_new(mac->key)) == NULL)
162			return SSH_ERR_ALLOC_FAIL;
163		return 0;
164	default:
165		return SSH_ERR_INVALID_ARGUMENT;
166	}
167}
168
169int
170mac_compute(struct sshmac *mac, u_int32_t seqno,
171    const u_char *data, int datalen,
172    u_char *digest, size_t dlen)
173{
174	static union {
175		u_char m[SSH_DIGEST_MAX_LENGTH];
176		u_int64_t for_align;
177	} u;
178	u_char b[4];
179	u_char nonce[8];
180
181	if (mac->mac_len > sizeof(u))
182		return SSH_ERR_INTERNAL_ERROR;
183
184	switch (mac->type) {
185	case SSH_DIGEST:
186		put_u32(b, seqno);
187		/* reset HMAC context */
188		if (ssh_hmac_init(mac->hmac_ctx, NULL, 0) < 0 ||
189		    ssh_hmac_update(mac->hmac_ctx, b, sizeof(b)) < 0 ||
190		    ssh_hmac_update(mac->hmac_ctx, data, datalen) < 0 ||
191		    ssh_hmac_final(mac->hmac_ctx, u.m, sizeof(u.m)) < 0)
192			return SSH_ERR_LIBCRYPTO_ERROR;
193		break;
194	case SSH_UMAC:
195		POKE_U64(nonce, seqno);
196		umac_update(mac->umac_ctx, data, datalen);
197		umac_final(mac->umac_ctx, u.m, nonce);
198		break;
199	case SSH_UMAC128:
200		put_u64(nonce, seqno);
201		umac128_update(mac->umac_ctx, data, datalen);
202		umac128_final(mac->umac_ctx, u.m, nonce);
203		break;
204	default:
205		return SSH_ERR_INVALID_ARGUMENT;
206	}
207	if (digest != NULL) {
208		if (dlen > mac->mac_len)
209			dlen = mac->mac_len;
210		memcpy(digest, u.m, dlen);
211	}
212	return 0;
213}
214
215int
216mac_check(struct sshmac *mac, u_int32_t seqno,
217    const u_char *data, size_t dlen,
218    const u_char *theirmac, size_t mlen)
219{
220	u_char ourmac[SSH_DIGEST_MAX_LENGTH];
221	int r;
222
223	if (mac->mac_len > mlen)
224		return SSH_ERR_INVALID_ARGUMENT;
225	if ((r = mac_compute(mac, seqno, data, dlen,
226	    ourmac, sizeof(ourmac))) != 0)
227		return r;
228	if (timingsafe_bcmp(ourmac, theirmac, mac->mac_len) != 0)
229		return SSH_ERR_MAC_INVALID;
230	return 0;
231}
232
233void
234mac_clear(struct sshmac *mac)
235{
236	if (mac->type == SSH_UMAC) {
237		if (mac->umac_ctx != NULL)
238			umac_delete(mac->umac_ctx);
239	} else if (mac->type == SSH_UMAC128) {
240		if (mac->umac_ctx != NULL)
241			umac128_delete(mac->umac_ctx);
242	} else if (mac->hmac_ctx != NULL)
243		ssh_hmac_free(mac->hmac_ctx);
244	mac->hmac_ctx = NULL;
245	mac->umac_ctx = NULL;
246}
247
248/* XXX copied from ciphers_valid */
249#define	MAC_SEP	","
250int
251mac_valid(const char *names)
252{
253	char *maclist, *cp, *p;
254
255	if (names == NULL || strcmp(names, "") == 0)
256		return 0;
257	if ((maclist = cp = strdup(names)) == NULL)
258		return 0;
259	for ((p = strsep(&cp, MAC_SEP)); p && *p != '\0';
260	    (p = strsep(&cp, MAC_SEP))) {
261		if (mac_setup(NULL, p) < 0) {
262			free(maclist);
263			return 0;
264		}
265	}
266	free(maclist);
267	return 1;
268}
269