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 * 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 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 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 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 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 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 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 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