xref: /openssh-portable/mac.c (revision edd1d3a6)
1 /* $OpenBSD: mac.c,v 1.35 2019/09/06 04:53:27 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 <stdlib.h>
31 #include <string.h>
32 #include <stdio.h>
33 
34 #include "digest.h"
35 #include "hmac.h"
36 #include "umac.h"
37 #include "mac.h"
38 #include "misc.h"
39 #include "ssherr.h"
40 #include "sshbuf.h"
41 
42 #include "openbsd-compat/openssl-compat.h"
43 
44 #define SSH_DIGEST	1	/* SSH_DIGEST_XXX */
45 #define SSH_UMAC	2	/* UMAC (not integrated with OpenSSL) */
46 #define SSH_UMAC128	3
47 
48 struct macalg {
49 	char		*name;
50 	int		type;
51 	int		alg;
52 	int		truncatebits;	/* truncate digest if != 0 */
53 	int		key_len;	/* just for UMAC */
54 	int		len;		/* just for UMAC */
55 	int		etm;		/* Encrypt-then-MAC */
56 };
57 
58 static const struct macalg macs[] = {
59 	/* Encrypt-and-MAC (encrypt-and-authenticate) variants */
60 	{ "hmac-sha1",				SSH_DIGEST, SSH_DIGEST_SHA1, 0, 0, 0, 0 },
61 	{ "hmac-sha1-96",			SSH_DIGEST, SSH_DIGEST_SHA1, 96, 0, 0, 0 },
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 	{ "hmac-md5",				SSH_DIGEST, SSH_DIGEST_MD5, 0, 0, 0, 0 },
65 	{ "hmac-md5-96",			SSH_DIGEST, SSH_DIGEST_MD5, 96, 0, 0, 0 },
66 	{ "umac-64@openssh.com",		SSH_UMAC, 0, 0, 128, 64, 0 },
67 	{ "umac-128@openssh.com",		SSH_UMAC128, 0, 0, 128, 128, 0 },
68 
69 	/* Encrypt-then-MAC variants */
70 	{ "hmac-sha1-etm@openssh.com",		SSH_DIGEST, SSH_DIGEST_SHA1, 0, 0, 0, 1 },
71 	{ "hmac-sha1-96-etm@openssh.com",	SSH_DIGEST, SSH_DIGEST_SHA1, 96, 0, 0, 1 },
72 	{ "hmac-sha2-256-etm@openssh.com",	SSH_DIGEST, SSH_DIGEST_SHA256, 0, 0, 0, 1 },
73 	{ "hmac-sha2-512-etm@openssh.com",	SSH_DIGEST, SSH_DIGEST_SHA512, 0, 0, 0, 1 },
74 	{ "hmac-md5-etm@openssh.com",		SSH_DIGEST, SSH_DIGEST_MD5, 0, 0, 0, 1 },
75 	{ "hmac-md5-96-etm@openssh.com",	SSH_DIGEST, SSH_DIGEST_MD5, 96, 0, 0, 1 },
76 	{ "umac-64-etm@openssh.com",		SSH_UMAC, 0, 0, 128, 64, 1 },
77 	{ "umac-128-etm@openssh.com",		SSH_UMAC128, 0, 0, 128, 128, 1 },
78 
79 	{ NULL,					0, 0, 0, 0, 0, 0 }
80 };
81 
82 /* Returns a list of supported MACs separated by the specified char. */
83 char *
mac_alg_list(char sep)84 mac_alg_list(char sep)
85 {
86 	char *ret = NULL, *tmp;
87 	size_t nlen, rlen = 0;
88 	const struct macalg *m;
89 
90 	for (m = macs; m->name != NULL; m++) {
91 		if (ret != NULL)
92 			ret[rlen++] = sep;
93 		nlen = strlen(m->name);
94 		if ((tmp = realloc(ret, rlen + nlen + 2)) == NULL) {
95 			free(ret);
96 			return NULL;
97 		}
98 		ret = tmp;
99 		memcpy(ret + rlen, m->name, nlen + 1);
100 		rlen += nlen;
101 	}
102 	return ret;
103 }
104 
105 static int
mac_setup_by_alg(struct sshmac * mac,const struct macalg * macalg)106 mac_setup_by_alg(struct sshmac *mac, const struct macalg *macalg)
107 {
108 	mac->type = macalg->type;
109 	if (mac->type == SSH_DIGEST) {
110 		if ((mac->hmac_ctx = ssh_hmac_start(macalg->alg)) == NULL)
111 			return SSH_ERR_ALLOC_FAIL;
112 		mac->key_len = mac->mac_len = ssh_hmac_bytes(macalg->alg);
113 	} else {
114 		mac->mac_len = macalg->len / 8;
115 		mac->key_len = macalg->key_len / 8;
116 		mac->umac_ctx = NULL;
117 	}
118 	if (macalg->truncatebits != 0)
119 		mac->mac_len = macalg->truncatebits / 8;
120 	mac->etm = macalg->etm;
121 	return 0;
122 }
123 
124 int
mac_setup(struct sshmac * mac,char * name)125 mac_setup(struct sshmac *mac, char *name)
126 {
127 	const struct macalg *m;
128 
129 	for (m = macs; m->name != NULL; m++) {
130 		if (strcmp(name, m->name) != 0)
131 			continue;
132 		if (mac != NULL)
133 			return mac_setup_by_alg(mac, m);
134 		return 0;
135 	}
136 	return SSH_ERR_INVALID_ARGUMENT;
137 }
138 
139 int
mac_init(struct sshmac * mac)140 mac_init(struct sshmac *mac)
141 {
142 	if (mac->key == NULL)
143 		return SSH_ERR_INVALID_ARGUMENT;
144 	switch (mac->type) {
145 	case SSH_DIGEST:
146 		if (mac->hmac_ctx == NULL ||
147 		    ssh_hmac_init(mac->hmac_ctx, mac->key, mac->key_len) < 0)
148 			return SSH_ERR_INVALID_ARGUMENT;
149 		return 0;
150 	case SSH_UMAC:
151 		if ((mac->umac_ctx = umac_new(mac->key)) == NULL)
152 			return SSH_ERR_ALLOC_FAIL;
153 		return 0;
154 	case SSH_UMAC128:
155 		if ((mac->umac_ctx = umac128_new(mac->key)) == NULL)
156 			return SSH_ERR_ALLOC_FAIL;
157 		return 0;
158 	default:
159 		return SSH_ERR_INVALID_ARGUMENT;
160 	}
161 }
162 
163 int
mac_compute(struct sshmac * mac,u_int32_t seqno,const u_char * data,int datalen,u_char * digest,size_t dlen)164 mac_compute(struct sshmac *mac, u_int32_t seqno,
165     const u_char *data, int datalen,
166     u_char *digest, size_t dlen)
167 {
168 	static union {
169 		u_char m[SSH_DIGEST_MAX_LENGTH];
170 		u_int64_t for_align;
171 	} u;
172 	u_char b[4];
173 	u_char nonce[8];
174 
175 	if (mac->mac_len > sizeof(u))
176 		return SSH_ERR_INTERNAL_ERROR;
177 
178 	switch (mac->type) {
179 	case SSH_DIGEST:
180 		put_u32(b, seqno);
181 		/* reset HMAC context */
182 		if (ssh_hmac_init(mac->hmac_ctx, NULL, 0) < 0 ||
183 		    ssh_hmac_update(mac->hmac_ctx, b, sizeof(b)) < 0 ||
184 		    ssh_hmac_update(mac->hmac_ctx, data, datalen) < 0 ||
185 		    ssh_hmac_final(mac->hmac_ctx, u.m, sizeof(u.m)) < 0)
186 			return SSH_ERR_LIBCRYPTO_ERROR;
187 		break;
188 	case SSH_UMAC:
189 		POKE_U64(nonce, seqno);
190 		umac_update(mac->umac_ctx, data, datalen);
191 		umac_final(mac->umac_ctx, u.m, nonce);
192 		break;
193 	case SSH_UMAC128:
194 		put_u64(nonce, seqno);
195 		umac128_update(mac->umac_ctx, data, datalen);
196 		umac128_final(mac->umac_ctx, u.m, nonce);
197 		break;
198 	default:
199 		return SSH_ERR_INVALID_ARGUMENT;
200 	}
201 	if (digest != NULL) {
202 		if (dlen > mac->mac_len)
203 			dlen = mac->mac_len;
204 		memcpy(digest, u.m, dlen);
205 	}
206 	return 0;
207 }
208 
209 int
mac_check(struct sshmac * mac,u_int32_t seqno,const u_char * data,size_t dlen,const u_char * theirmac,size_t mlen)210 mac_check(struct sshmac *mac, u_int32_t seqno,
211     const u_char *data, size_t dlen,
212     const u_char *theirmac, size_t mlen)
213 {
214 	u_char ourmac[SSH_DIGEST_MAX_LENGTH];
215 	int r;
216 
217 	if (mac->mac_len > mlen)
218 		return SSH_ERR_INVALID_ARGUMENT;
219 	if ((r = mac_compute(mac, seqno, data, dlen,
220 	    ourmac, sizeof(ourmac))) != 0)
221 		return r;
222 	if (timingsafe_bcmp(ourmac, theirmac, mac->mac_len) != 0)
223 		return SSH_ERR_MAC_INVALID;
224 	return 0;
225 }
226 
227 void
mac_clear(struct sshmac * mac)228 mac_clear(struct sshmac *mac)
229 {
230 	if (mac->type == SSH_UMAC) {
231 		if (mac->umac_ctx != NULL)
232 			umac_delete(mac->umac_ctx);
233 	} else if (mac->type == SSH_UMAC128) {
234 		if (mac->umac_ctx != NULL)
235 			umac128_delete(mac->umac_ctx);
236 	} else if (mac->hmac_ctx != NULL)
237 		ssh_hmac_free(mac->hmac_ctx);
238 	mac->hmac_ctx = NULL;
239 	mac->umac_ctx = NULL;
240 }
241 
242 /* XXX copied from ciphers_valid */
243 #define	MAC_SEP	","
244 int
mac_valid(const char * names)245 mac_valid(const char *names)
246 {
247 	char *maclist, *cp, *p;
248 
249 	if (names == NULL || strcmp(names, "") == 0)
250 		return 0;
251 	if ((maclist = cp = strdup(names)) == NULL)
252 		return 0;
253 	for ((p = strsep(&cp, MAC_SEP)); p && *p != '\0';
254 	    (p = strsep(&cp, MAC_SEP))) {
255 		if (mac_setup(NULL, p) < 0) {
256 			free(maclist);
257 			return 0;
258 		}
259 	}
260 	free(maclist);
261 	return 1;
262 }
263