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