1/* $OpenBSD: mac.c,v 1.34 2017/05/08 22:57:38 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	{ "umac-64@openssh.com",		SSH_UMAC, 0, 0, 128, 64, 0 },
68	{ "umac-128@openssh.com",		SSH_UMAC128, 0, 0, 128, 128, 0 },
69
70	/* Encrypt-then-MAC variants */
71	{ "hmac-sha1-etm@openssh.com",		SSH_DIGEST, SSH_DIGEST_SHA1, 0, 0, 0, 1 },
72	{ "hmac-sha1-96-etm@openssh.com",	SSH_DIGEST, SSH_DIGEST_SHA1, 96, 0, 0, 1 },
73#ifdef HAVE_EVP_SHA256
74	{ "hmac-sha2-256-etm@openssh.com",	SSH_DIGEST, SSH_DIGEST_SHA256, 0, 0, 0, 1 },
75	{ "hmac-sha2-512-etm@openssh.com",	SSH_DIGEST, SSH_DIGEST_SHA512, 0, 0, 0, 1 },
76#endif
77	{ "hmac-md5-etm@openssh.com",		SSH_DIGEST, SSH_DIGEST_MD5, 0, 0, 0, 1 },
78	{ "hmac-md5-96-etm@openssh.com",	SSH_DIGEST, SSH_DIGEST_MD5, 96, 0, 0, 1 },
79	{ "umac-64-etm@openssh.com",		SSH_UMAC, 0, 0, 128, 64, 1 },
80	{ "umac-128-etm@openssh.com",		SSH_UMAC128, 0, 0, 128, 128, 1 },
81
82	{ NULL,					0, 0, 0, 0, 0, 0 }
83};
84
85/* Returns a list of supported MACs separated by the specified char. */
86char *
87mac_alg_list(char sep)
88{
89	char *ret = NULL, *tmp;
90	size_t nlen, rlen = 0;
91	const struct macalg *m;
92
93	for (m = macs; m->name != NULL; m++) {
94		if (ret != NULL)
95			ret[rlen++] = sep;
96		nlen = strlen(m->name);
97		if ((tmp = realloc(ret, rlen + nlen + 2)) == NULL) {
98			free(ret);
99			return NULL;
100		}
101		ret = tmp;
102		memcpy(ret + rlen, m->name, nlen + 1);
103		rlen += nlen;
104	}
105	return ret;
106}
107
108static int
109mac_setup_by_alg(struct sshmac *mac, const struct macalg *macalg)
110{
111	mac->type = macalg->type;
112	if (mac->type == SSH_DIGEST) {
113		if ((mac->hmac_ctx = ssh_hmac_start(macalg->alg)) == NULL)
114			return SSH_ERR_ALLOC_FAIL;
115		mac->key_len = mac->mac_len = ssh_hmac_bytes(macalg->alg);
116	} else {
117		mac->mac_len = macalg->len / 8;
118		mac->key_len = macalg->key_len / 8;
119		mac->umac_ctx = NULL;
120	}
121	if (macalg->truncatebits != 0)
122		mac->mac_len = macalg->truncatebits / 8;
123	mac->etm = macalg->etm;
124	return 0;
125}
126
127int
128mac_setup(struct sshmac *mac, char *name)
129{
130	const struct macalg *m;
131
132	for (m = macs; m->name != NULL; m++) {
133		if (strcmp(name, m->name) != 0)
134			continue;
135		if (mac != NULL)
136			return mac_setup_by_alg(mac, m);
137		return 0;
138	}
139	return SSH_ERR_INVALID_ARGUMENT;
140}
141
142int
143mac_init(struct sshmac *mac)
144{
145	if (mac->key == NULL)
146		return SSH_ERR_INVALID_ARGUMENT;
147	switch (mac->type) {
148	case SSH_DIGEST:
149		if (mac->hmac_ctx == NULL ||
150		    ssh_hmac_init(mac->hmac_ctx, mac->key, mac->key_len) < 0)
151			return SSH_ERR_INVALID_ARGUMENT;
152		return 0;
153	case SSH_UMAC:
154		if ((mac->umac_ctx = umac_new(mac->key)) == NULL)
155			return SSH_ERR_ALLOC_FAIL;
156		return 0;
157	case SSH_UMAC128:
158		if ((mac->umac_ctx = umac128_new(mac->key)) == NULL)
159			return SSH_ERR_ALLOC_FAIL;
160		return 0;
161	default:
162		return SSH_ERR_INVALID_ARGUMENT;
163	}
164}
165
166int
167mac_compute(struct sshmac *mac, u_int32_t seqno,
168    const u_char *data, int datalen,
169    u_char *digest, size_t dlen)
170{
171	static union {
172		u_char m[SSH_DIGEST_MAX_LENGTH];
173		u_int64_t for_align;
174	} u;
175	u_char b[4];
176	u_char nonce[8];
177
178	if (mac->mac_len > sizeof(u))
179		return SSH_ERR_INTERNAL_ERROR;
180
181	switch (mac->type) {
182	case SSH_DIGEST:
183		put_u32(b, seqno);
184		/* reset HMAC context */
185		if (ssh_hmac_init(mac->hmac_ctx, NULL, 0) < 0 ||
186		    ssh_hmac_update(mac->hmac_ctx, b, sizeof(b)) < 0 ||
187		    ssh_hmac_update(mac->hmac_ctx, data, datalen) < 0 ||
188		    ssh_hmac_final(mac->hmac_ctx, u.m, sizeof(u.m)) < 0)
189			return SSH_ERR_LIBCRYPTO_ERROR;
190		break;
191	case SSH_UMAC:
192		POKE_U64(nonce, seqno);
193		umac_update(mac->umac_ctx, data, datalen);
194		umac_final(mac->umac_ctx, u.m, nonce);
195		break;
196	case SSH_UMAC128:
197		put_u64(nonce, seqno);
198		umac128_update(mac->umac_ctx, data, datalen);
199		umac128_final(mac->umac_ctx, u.m, nonce);
200		break;
201	default:
202		return SSH_ERR_INVALID_ARGUMENT;
203	}
204	if (digest != NULL) {
205		if (dlen > mac->mac_len)
206			dlen = mac->mac_len;
207		memcpy(digest, u.m, dlen);
208	}
209	return 0;
210}
211
212int
213mac_check(struct sshmac *mac, u_int32_t seqno,
214    const u_char *data, size_t dlen,
215    const u_char *theirmac, size_t mlen)
216{
217	u_char ourmac[SSH_DIGEST_MAX_LENGTH];
218	int r;
219
220	if (mac->mac_len > mlen)
221		return SSH_ERR_INVALID_ARGUMENT;
222	if ((r = mac_compute(mac, seqno, data, dlen,
223	    ourmac, sizeof(ourmac))) != 0)
224		return r;
225	if (timingsafe_bcmp(ourmac, theirmac, mac->mac_len) != 0)
226		return SSH_ERR_MAC_INVALID;
227	return 0;
228}
229
230void
231mac_clear(struct sshmac *mac)
232{
233	if (mac->type == SSH_UMAC) {
234		if (mac->umac_ctx != NULL)
235			umac_delete(mac->umac_ctx);
236	} else if (mac->type == SSH_UMAC128) {
237		if (mac->umac_ctx != NULL)
238			umac128_delete(mac->umac_ctx);
239	} else if (mac->hmac_ctx != NULL)
240		ssh_hmac_free(mac->hmac_ctx);
241	mac->hmac_ctx = NULL;
242	mac->umac_ctx = NULL;
243}
244
245/* XXX copied from ciphers_valid */
246#define	MAC_SEP	","
247int
248mac_valid(const char *names)
249{
250	char *maclist, *cp, *p;
251
252	if (names == NULL || strcmp(names, "") == 0)
253		return 0;
254	if ((maclist = cp = strdup(names)) == NULL)
255		return 0;
256	for ((p = strsep(&cp, MAC_SEP)); p && *p != '\0';
257	    (p = strsep(&cp, MAC_SEP))) {
258		if (mac_setup(NULL, p) < 0) {
259			free(maclist);
260			return 0;
261		}
262	}
263	free(maclist);
264	return 1;
265}
266