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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 #ifdef HAVE_EVP_RIPEMD160
68 	{ "hmac-ripemd160",			SSH_DIGEST, SSH_DIGEST_RIPEMD160, 0, 0, 0, 0 },
69 	{ "hmac-ripemd160@openssh.com",		SSH_DIGEST, SSH_DIGEST_RIPEMD160, 0, 0, 0, 0 },
70 #endif
71 	{ "umac-64@openssh.com",		SSH_UMAC, 0, 0, 128, 64, 0 },
72 	{ "umac-128@openssh.com",		SSH_UMAC128, 0, 0, 128, 128, 0 },
73 
74 	/* Encrypt-then-MAC variants */
75 	{ "hmac-sha1-etm@openssh.com",		SSH_DIGEST, SSH_DIGEST_SHA1, 0, 0, 0, 1 },
76 	{ "hmac-sha1-96-etm@openssh.com",	SSH_DIGEST, SSH_DIGEST_SHA1, 96, 0, 0, 1 },
77 #ifdef HAVE_EVP_SHA256
78 	{ "hmac-sha2-256-etm@openssh.com",	SSH_DIGEST, SSH_DIGEST_SHA256, 0, 0, 0, 1 },
79 	{ "hmac-sha2-512-etm@openssh.com",	SSH_DIGEST, SSH_DIGEST_SHA512, 0, 0, 0, 1 },
80 #endif
81 	{ "hmac-md5-etm@openssh.com",		SSH_DIGEST, SSH_DIGEST_MD5, 0, 0, 0, 1 },
82 	{ "hmac-md5-96-etm@openssh.com",	SSH_DIGEST, SSH_DIGEST_MD5, 96, 0, 0, 1 },
83 #ifdef HAVE_EVP_RIPEMD160
84 	{ "hmac-ripemd160-etm@openssh.com",	SSH_DIGEST, SSH_DIGEST_RIPEMD160, 0, 0, 0, 1 },
85 #endif
86 	{ "umac-64-etm@openssh.com",		SSH_UMAC, 0, 0, 128, 64, 1 },
87 	{ "umac-128-etm@openssh.com",		SSH_UMAC128, 0, 0, 128, 128, 1 },
88 
89 	{ NULL,					0, 0, 0, 0, 0, 0 }
90 };
91 
92 /* Returns a list of supported MACs separated by the specified char. */
93 char *
mac_alg_list(char sep)94 mac_alg_list(char sep)
95 {
96 	char *ret = NULL, *tmp;
97 	size_t nlen, rlen = 0;
98 	const struct macalg *m;
99 
100 	for (m = macs; m->name != NULL; m++) {
101 		if (ret != NULL)
102 			ret[rlen++] = sep;
103 		nlen = strlen(m->name);
104 		if ((tmp = realloc(ret, rlen + nlen + 2)) == NULL) {
105 			free(ret);
106 			return NULL;
107 		}
108 		ret = tmp;
109 		memcpy(ret + rlen, m->name, nlen + 1);
110 		rlen += nlen;
111 	}
112 	return ret;
113 }
114 
115 static int
mac_setup_by_alg(struct sshmac * mac,const struct macalg * macalg)116 mac_setup_by_alg(struct sshmac *mac, const struct macalg *macalg)
117 {
118 	mac->type = macalg->type;
119 	if (mac->type == SSH_DIGEST) {
120 		if ((mac->hmac_ctx = ssh_hmac_start(macalg->alg)) == NULL)
121 			return SSH_ERR_ALLOC_FAIL;
122 		mac->key_len = mac->mac_len = ssh_hmac_bytes(macalg->alg);
123 	} else {
124 		mac->mac_len = macalg->len / 8;
125 		mac->key_len = macalg->key_len / 8;
126 		mac->umac_ctx = NULL;
127 	}
128 	if (macalg->truncatebits != 0)
129 		mac->mac_len = macalg->truncatebits / 8;
130 	mac->etm = macalg->etm;
131 	return 0;
132 }
133 
134 int
mac_setup(struct sshmac * mac,char * name)135 mac_setup(struct sshmac *mac, char *name)
136 {
137 	const struct macalg *m;
138 
139 	for (m = macs; m->name != NULL; m++) {
140 		if (strcmp(name, m->name) != 0)
141 			continue;
142 		if (mac != NULL)
143 			return mac_setup_by_alg(mac, m);
144 		return 0;
145 	}
146 	return SSH_ERR_INVALID_ARGUMENT;
147 }
148 
149 int
mac_init(struct sshmac * mac)150 mac_init(struct sshmac *mac)
151 {
152 	if (mac->key == NULL)
153 		return SSH_ERR_INVALID_ARGUMENT;
154 	switch (mac->type) {
155 	case SSH_DIGEST:
156 		if (mac->hmac_ctx == NULL ||
157 		    ssh_hmac_init(mac->hmac_ctx, mac->key, mac->key_len) < 0)
158 			return SSH_ERR_INVALID_ARGUMENT;
159 		return 0;
160 	case SSH_UMAC:
161 		if ((mac->umac_ctx = umac_new(mac->key)) == NULL)
162 			return SSH_ERR_ALLOC_FAIL;
163 		return 0;
164 	case SSH_UMAC128:
165 		if ((mac->umac_ctx = umac128_new(mac->key)) == NULL)
166 			return SSH_ERR_ALLOC_FAIL;
167 		return 0;
168 	default:
169 		return SSH_ERR_INVALID_ARGUMENT;
170 	}
171 }
172 
173 int
mac_compute(struct sshmac * mac,u_int32_t seqno,const u_char * data,int datalen,u_char * digest,size_t dlen)174 mac_compute(struct sshmac *mac, u_int32_t seqno,
175     const u_char *data, int datalen,
176     u_char *digest, size_t dlen)
177 {
178 	static union {
179 		u_char m[SSH_DIGEST_MAX_LENGTH];
180 		u_int64_t for_align;
181 	} u;
182 	u_char b[4];
183 	u_char nonce[8];
184 
185 	if (mac->mac_len > sizeof(u))
186 		return SSH_ERR_INTERNAL_ERROR;
187 
188 	switch (mac->type) {
189 	case SSH_DIGEST:
190 		put_u32(b, seqno);
191 		/* reset HMAC context */
192 		if (ssh_hmac_init(mac->hmac_ctx, NULL, 0) < 0 ||
193 		    ssh_hmac_update(mac->hmac_ctx, b, sizeof(b)) < 0 ||
194 		    ssh_hmac_update(mac->hmac_ctx, data, datalen) < 0 ||
195 		    ssh_hmac_final(mac->hmac_ctx, u.m, sizeof(u.m)) < 0)
196 			return SSH_ERR_LIBCRYPTO_ERROR;
197 		break;
198 	case SSH_UMAC:
199 		POKE_U64(nonce, seqno);
200 		umac_update(mac->umac_ctx, data, datalen);
201 		umac_final(mac->umac_ctx, u.m, nonce);
202 		break;
203 	case SSH_UMAC128:
204 		put_u64(nonce, seqno);
205 		umac128_update(mac->umac_ctx, data, datalen);
206 		umac128_final(mac->umac_ctx, u.m, nonce);
207 		break;
208 	default:
209 		return SSH_ERR_INVALID_ARGUMENT;
210 	}
211 	if (digest != NULL) {
212 		if (dlen > mac->mac_len)
213 			dlen = mac->mac_len;
214 		memcpy(digest, u.m, dlen);
215 	}
216 	return 0;
217 }
218 
219 int
mac_check(struct sshmac * mac,u_int32_t seqno,const u_char * data,size_t dlen,const u_char * theirmac,size_t mlen)220 mac_check(struct sshmac *mac, u_int32_t seqno,
221     const u_char *data, size_t dlen,
222     const u_char *theirmac, size_t mlen)
223 {
224 	u_char ourmac[SSH_DIGEST_MAX_LENGTH];
225 	int r;
226 
227 	if (mac->mac_len > mlen)
228 		return SSH_ERR_INVALID_ARGUMENT;
229 	if ((r = mac_compute(mac, seqno, data, dlen,
230 	    ourmac, sizeof(ourmac))) != 0)
231 		return r;
232 	if (timingsafe_bcmp(ourmac, theirmac, mac->mac_len) != 0)
233 		return SSH_ERR_MAC_INVALID;
234 	return 0;
235 }
236 
237 void
mac_clear(struct sshmac * mac)238 mac_clear(struct sshmac *mac)
239 {
240 	if (mac->type == SSH_UMAC) {
241 		if (mac->umac_ctx != NULL)
242 			umac_delete(mac->umac_ctx);
243 	} else if (mac->type == SSH_UMAC128) {
244 		if (mac->umac_ctx != NULL)
245 			umac128_delete(mac->umac_ctx);
246 	} else if (mac->hmac_ctx != NULL)
247 		ssh_hmac_free(mac->hmac_ctx);
248 	mac->hmac_ctx = NULL;
249 	mac->umac_ctx = NULL;
250 }
251 
252 /* XXX copied from ciphers_valid */
253 #define	MAC_SEP	","
254 int
mac_valid(const char * names)255 mac_valid(const char *names)
256 {
257 	char *maclist, *cp, *p;
258 
259 	if (names == NULL || strcmp(names, "") == 0)
260 		return 0;
261 	if ((maclist = cp = strdup(names)) == NULL)
262 		return 0;
263 	for ((p = strsep(&cp, MAC_SEP)); p && *p != '\0';
264 	    (p = strsep(&cp, MAC_SEP))) {
265 		if (mac_setup(NULL, p) < 0) {
266 			free(maclist);
267 			return 0;
268 		}
269 	}
270 	free(maclist);
271 	return 1;
272 }
273