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