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 (at) openssh.com", SSH_DIGEST, SSH_DIGEST_RIPEMD160, 0, 0, 0, 0 }, 70 #endif 71 { "umac-64 (at) openssh.com", SSH_UMAC, 0, 0, 128, 64, 0 }, 72 { "umac-128 (at) openssh.com", SSH_UMAC128, 0, 0, 128, 128, 0 }, 73 74 /* Encrypt-then-MAC variants */ 75 { "hmac-sha1-etm (at) openssh.com", SSH_DIGEST, SSH_DIGEST_SHA1, 0, 0, 0, 1 }, 76 { "hmac-sha1-96-etm (at) openssh.com", SSH_DIGEST, SSH_DIGEST_SHA1, 96, 0, 0, 1 }, 77 #ifdef HAVE_EVP_SHA256 78 { "hmac-sha2-256-etm (at) openssh.com", SSH_DIGEST, SSH_DIGEST_SHA256, 0, 0, 0, 1 }, 79 { "hmac-sha2-512-etm (at) openssh.com", SSH_DIGEST, SSH_DIGEST_SHA512, 0, 0, 0, 1 }, 80 #endif 81 { "hmac-md5-etm (at) openssh.com", SSH_DIGEST, SSH_DIGEST_MD5, 0, 0, 0, 1 }, 82 { "hmac-md5-96-etm (at) openssh.com", SSH_DIGEST, SSH_DIGEST_MD5, 96, 0, 0, 1 }, 83 #ifdef HAVE_EVP_RIPEMD160 84 { "hmac-ripemd160-etm (at) openssh.com", SSH_DIGEST, SSH_DIGEST_RIPEMD160, 0, 0, 0, 1 }, 85 #endif 86 { "umac-64-etm (at) openssh.com", SSH_UMAC, 0, 0, 128, 64, 1 }, 87 { "umac-128-etm (at) 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 * 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 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 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 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 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 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 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 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
