1 /* $OpenBSD: mac.c,v 1.34 2017/05/08 22:57:38 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 { "umac-64@openssh.com", SSH_UMAC, 0, 0, 128, 64, 0 }, 68 { "umac-128@openssh.com", SSH_UMAC128, 0, 0, 128, 128, 0 }, 69 70 /* Encrypt-then-MAC variants */ 71 { "hmac-sha1-etm@openssh.com", SSH_DIGEST, SSH_DIGEST_SHA1, 0, 0, 0, 1 }, 72 { "hmac-sha1-96-etm@openssh.com", SSH_DIGEST, SSH_DIGEST_SHA1, 96, 0, 0, 1 }, 73 #ifdef HAVE_EVP_SHA256 74 { "hmac-sha2-256-etm@openssh.com", SSH_DIGEST, SSH_DIGEST_SHA256, 0, 0, 0, 1 }, 75 { "hmac-sha2-512-etm@openssh.com", SSH_DIGEST, SSH_DIGEST_SHA512, 0, 0, 0, 1 }, 76 #endif 77 { "hmac-md5-etm@openssh.com", SSH_DIGEST, SSH_DIGEST_MD5, 0, 0, 0, 1 }, 78 { "hmac-md5-96-etm@openssh.com", SSH_DIGEST, SSH_DIGEST_MD5, 96, 0, 0, 1 }, 79 { "umac-64-etm@openssh.com", SSH_UMAC, 0, 0, 128, 64, 1 }, 80 { "umac-128-etm@openssh.com", SSH_UMAC128, 0, 0, 128, 128, 1 }, 81 82 { NULL, 0, 0, 0, 0, 0, 0 } 83 }; 84 85 /* Returns a list of supported MACs separated by the specified char. */ 86 char * 87 mac_alg_list(char sep) 88 { 89 char *ret = NULL, *tmp; 90 size_t nlen, rlen = 0; 91 const struct macalg *m; 92 93 for (m = macs; m->name != NULL; m++) { 94 if (ret != NULL) 95 ret[rlen++] = sep; 96 nlen = strlen(m->name); 97 if ((tmp = realloc(ret, rlen + nlen + 2)) == NULL) { 98 free(ret); 99 return NULL; 100 } 101 ret = tmp; 102 memcpy(ret + rlen, m->name, nlen + 1); 103 rlen += nlen; 104 } 105 return ret; 106 } 107 108 static int 109 mac_setup_by_alg(struct sshmac *mac, const struct macalg *macalg) 110 { 111 mac->type = macalg->type; 112 if (mac->type == SSH_DIGEST) { 113 if ((mac->hmac_ctx = ssh_hmac_start(macalg->alg)) == NULL) 114 return SSH_ERR_ALLOC_FAIL; 115 mac->key_len = mac->mac_len = ssh_hmac_bytes(macalg->alg); 116 } else { 117 mac->mac_len = macalg->len / 8; 118 mac->key_len = macalg->key_len / 8; 119 mac->umac_ctx = NULL; 120 } 121 if (macalg->truncatebits != 0) 122 mac->mac_len = macalg->truncatebits / 8; 123 mac->etm = macalg->etm; 124 return 0; 125 } 126 127 int 128 mac_setup(struct sshmac *mac, char *name) 129 { 130 const struct macalg *m; 131 132 for (m = macs; m->name != NULL; m++) { 133 if (strcmp(name, m->name) != 0) 134 continue; 135 if (mac != NULL) 136 return mac_setup_by_alg(mac, m); 137 return 0; 138 } 139 return SSH_ERR_INVALID_ARGUMENT; 140 } 141 142 int 143 mac_init(struct sshmac *mac) 144 { 145 if (mac->key == NULL) 146 return SSH_ERR_INVALID_ARGUMENT; 147 switch (mac->type) { 148 case SSH_DIGEST: 149 if (mac->hmac_ctx == NULL || 150 ssh_hmac_init(mac->hmac_ctx, mac->key, mac->key_len) < 0) 151 return SSH_ERR_INVALID_ARGUMENT; 152 return 0; 153 case SSH_UMAC: 154 if ((mac->umac_ctx = umac_new(mac->key)) == NULL) 155 return SSH_ERR_ALLOC_FAIL; 156 return 0; 157 case SSH_UMAC128: 158 if ((mac->umac_ctx = umac128_new(mac->key)) == NULL) 159 return SSH_ERR_ALLOC_FAIL; 160 return 0; 161 default: 162 return SSH_ERR_INVALID_ARGUMENT; 163 } 164 } 165 166 int 167 mac_compute(struct sshmac *mac, u_int32_t seqno, 168 const u_char *data, int datalen, 169 u_char *digest, size_t dlen) 170 { 171 static union { 172 u_char m[SSH_DIGEST_MAX_LENGTH]; 173 u_int64_t for_align; 174 } u; 175 u_char b[4]; 176 u_char nonce[8]; 177 178 if (mac->mac_len > sizeof(u)) 179 return SSH_ERR_INTERNAL_ERROR; 180 181 switch (mac->type) { 182 case SSH_DIGEST: 183 put_u32(b, seqno); 184 /* reset HMAC context */ 185 if (ssh_hmac_init(mac->hmac_ctx, NULL, 0) < 0 || 186 ssh_hmac_update(mac->hmac_ctx, b, sizeof(b)) < 0 || 187 ssh_hmac_update(mac->hmac_ctx, data, datalen) < 0 || 188 ssh_hmac_final(mac->hmac_ctx, u.m, sizeof(u.m)) < 0) 189 return SSH_ERR_LIBCRYPTO_ERROR; 190 break; 191 case SSH_UMAC: 192 POKE_U64(nonce, seqno); 193 umac_update(mac->umac_ctx, data, datalen); 194 umac_final(mac->umac_ctx, u.m, nonce); 195 break; 196 case SSH_UMAC128: 197 put_u64(nonce, seqno); 198 umac128_update(mac->umac_ctx, data, datalen); 199 umac128_final(mac->umac_ctx, u.m, nonce); 200 break; 201 default: 202 return SSH_ERR_INVALID_ARGUMENT; 203 } 204 if (digest != NULL) { 205 if (dlen > mac->mac_len) 206 dlen = mac->mac_len; 207 memcpy(digest, u.m, dlen); 208 } 209 return 0; 210 } 211 212 int 213 mac_check(struct sshmac *mac, u_int32_t seqno, 214 const u_char *data, size_t dlen, 215 const u_char *theirmac, size_t mlen) 216 { 217 u_char ourmac[SSH_DIGEST_MAX_LENGTH]; 218 int r; 219 220 if (mac->mac_len > mlen) 221 return SSH_ERR_INVALID_ARGUMENT; 222 if ((r = mac_compute(mac, seqno, data, dlen, 223 ourmac, sizeof(ourmac))) != 0) 224 return r; 225 if (timingsafe_bcmp(ourmac, theirmac, mac->mac_len) != 0) 226 return SSH_ERR_MAC_INVALID; 227 return 0; 228 } 229 230 void 231 mac_clear(struct sshmac *mac) 232 { 233 if (mac->type == SSH_UMAC) { 234 if (mac->umac_ctx != NULL) 235 umac_delete(mac->umac_ctx); 236 } else if (mac->type == SSH_UMAC128) { 237 if (mac->umac_ctx != NULL) 238 umac128_delete(mac->umac_ctx); 239 } else if (mac->hmac_ctx != NULL) 240 ssh_hmac_free(mac->hmac_ctx); 241 mac->hmac_ctx = NULL; 242 mac->umac_ctx = NULL; 243 } 244 245 /* XXX copied from ciphers_valid */ 246 #define MAC_SEP "," 247 int 248 mac_valid(const char *names) 249 { 250 char *maclist, *cp, *p; 251 252 if (names == NULL || strcmp(names, "") == 0) 253 return 0; 254 if ((maclist = cp = strdup(names)) == NULL) 255 return 0; 256 for ((p = strsep(&cp, MAC_SEP)); p && *p != '\0'; 257 (p = strsep(&cp, MAC_SEP))) { 258 if (mac_setup(NULL, p) < 0) { 259 free(maclist); 260 return 0; 261 } 262 } 263 free(maclist); 264 return 1; 265 } 266