xref: /openssh-portable/mac.c (revision 7bdb2eeb)
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 
47 struct 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 
57 static 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. */
86 char *
87 mac_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 
108 static int
109 mac_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 
127 int
128 mac_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 
142 int
143 mac_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 
166 int
167 mac_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 
212 int
213 mac_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 
230 void
231 mac_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	","
247 int
248 mac_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