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