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 * 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 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 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 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 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 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 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 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