xref: /freebsd/crypto/openssh/mac.c (revision 642870485c089b57000fe538d3485e272b038d59)
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 
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 	{ "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. */
89 char *
90 mac_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 
111 static int
112 mac_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 
130 int
131 mac_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 
145 int
146 mac_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 
169 int
170 mac_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 
215 int
216 mac_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 
233 void
234 mac_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	","
250 int
251 mac_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