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 <sys/types.h> 27 28 #include <string.h> 29 #include <stdio.h> 30 31 #include "digest.h" 32 #include "hmac.h" 33 #include "umac.h" 34 #include "mac.h" 35 #include "misc.h" 36 #include "ssherr.h" 37 #include "sshbuf.h" 38 39 #define SSH_DIGEST 1 /* SSH_DIGEST_XXX */ 40 #define SSH_UMAC 2 /* UMAC (not integrated with OpenSSL) */ 41 #define SSH_UMAC128 3 42 43 struct macalg { 44 char *name; 45 int type; 46 int alg; 47 int truncatebits; /* truncate digest if != 0 */ 48 int key_len; /* just for UMAC */ 49 int len; /* just for UMAC */ 50 int etm; /* Encrypt-then-MAC */ 51 }; 52 53 static const struct macalg macs[] = { 54 /* Encrypt-and-MAC (encrypt-and-authenticate) variants */ 55 { "hmac-sha1", SSH_DIGEST, SSH_DIGEST_SHA1, 0, 0, 0, 0 }, 56 { "hmac-sha1-96", SSH_DIGEST, SSH_DIGEST_SHA1, 96, 0, 0, 0 }, 57 { "hmac-sha2-256", SSH_DIGEST, SSH_DIGEST_SHA256, 0, 0, 0, 0 }, 58 { "hmac-sha2-512", SSH_DIGEST, SSH_DIGEST_SHA512, 0, 0, 0, 0 }, 59 { "hmac-md5", SSH_DIGEST, SSH_DIGEST_MD5, 0, 0, 0, 0 }, 60 { "hmac-md5-96", SSH_DIGEST, SSH_DIGEST_MD5, 96, 0, 0, 0 }, 61 { "umac-64@openssh.com", SSH_UMAC, 0, 0, 128, 64, 0 }, 62 { "umac-128@openssh.com", SSH_UMAC128, 0, 0, 128, 128, 0 }, 63 64 /* Encrypt-then-MAC variants */ 65 { "hmac-sha1-etm@openssh.com", SSH_DIGEST, SSH_DIGEST_SHA1, 0, 0, 0, 1 }, 66 { "hmac-sha1-96-etm@openssh.com", SSH_DIGEST, SSH_DIGEST_SHA1, 96, 0, 0, 1 }, 67 { "hmac-sha2-256-etm@openssh.com", SSH_DIGEST, SSH_DIGEST_SHA256, 0, 0, 0, 1 }, 68 { "hmac-sha2-512-etm@openssh.com", SSH_DIGEST, SSH_DIGEST_SHA512, 0, 0, 0, 1 }, 69 { "hmac-md5-etm@openssh.com", SSH_DIGEST, SSH_DIGEST_MD5, 0, 0, 0, 1 }, 70 { "hmac-md5-96-etm@openssh.com", SSH_DIGEST, SSH_DIGEST_MD5, 96, 0, 0, 1 }, 71 { "umac-64-etm@openssh.com", SSH_UMAC, 0, 0, 128, 64, 1 }, 72 { "umac-128-etm@openssh.com", SSH_UMAC128, 0, 0, 128, 128, 1 }, 73 74 { NULL, 0, 0, 0, 0, 0, 0 } 75 }; 76 77 /* Returns a list of supported MACs separated by the specified char. */ 78 char * 79 mac_alg_list(char sep) 80 { 81 char *ret = NULL, *tmp; 82 size_t nlen, rlen = 0; 83 const struct macalg *m; 84 85 for (m = macs; m->name != NULL; m++) { 86 if (ret != NULL) 87 ret[rlen++] = sep; 88 nlen = strlen(m->name); 89 if ((tmp = realloc(ret, rlen + nlen + 2)) == NULL) { 90 free(ret); 91 return NULL; 92 } 93 ret = tmp; 94 memcpy(ret + rlen, m->name, nlen + 1); 95 rlen += nlen; 96 } 97 return ret; 98 } 99 100 static int 101 mac_setup_by_alg(struct sshmac *mac, const struct macalg *macalg) 102 { 103 mac->type = macalg->type; 104 if (mac->type == SSH_DIGEST) { 105 if ((mac->hmac_ctx = ssh_hmac_start(macalg->alg)) == NULL) 106 return SSH_ERR_ALLOC_FAIL; 107 mac->key_len = mac->mac_len = ssh_hmac_bytes(macalg->alg); 108 } else { 109 mac->mac_len = macalg->len / 8; 110 mac->key_len = macalg->key_len / 8; 111 mac->umac_ctx = NULL; 112 } 113 if (macalg->truncatebits != 0) 114 mac->mac_len = macalg->truncatebits / 8; 115 mac->etm = macalg->etm; 116 return 0; 117 } 118 119 int 120 mac_setup(struct sshmac *mac, char *name) 121 { 122 const struct macalg *m; 123 124 for (m = macs; m->name != NULL; m++) { 125 if (strcmp(name, m->name) != 0) 126 continue; 127 if (mac != NULL) 128 return mac_setup_by_alg(mac, m); 129 return 0; 130 } 131 return SSH_ERR_INVALID_ARGUMENT; 132 } 133 134 int 135 mac_init(struct sshmac *mac) 136 { 137 if (mac->key == NULL) 138 return SSH_ERR_INVALID_ARGUMENT; 139 switch (mac->type) { 140 case SSH_DIGEST: 141 if (mac->hmac_ctx == NULL || 142 ssh_hmac_init(mac->hmac_ctx, mac->key, mac->key_len) < 0) 143 return SSH_ERR_INVALID_ARGUMENT; 144 return 0; 145 case SSH_UMAC: 146 if ((mac->umac_ctx = umac_new(mac->key)) == NULL) 147 return SSH_ERR_ALLOC_FAIL; 148 return 0; 149 case SSH_UMAC128: 150 if ((mac->umac_ctx = umac128_new(mac->key)) == NULL) 151 return SSH_ERR_ALLOC_FAIL; 152 return 0; 153 default: 154 return SSH_ERR_INVALID_ARGUMENT; 155 } 156 } 157 158 int 159 mac_compute(struct sshmac *mac, u_int32_t seqno, 160 const u_char *data, int datalen, 161 u_char *digest, size_t dlen) 162 { 163 static union { 164 u_char m[SSH_DIGEST_MAX_LENGTH]; 165 u_int64_t for_align; 166 } u; 167 u_char b[4]; 168 u_char nonce[8]; 169 170 if (mac->mac_len > sizeof(u)) 171 return SSH_ERR_INTERNAL_ERROR; 172 173 switch (mac->type) { 174 case SSH_DIGEST: 175 put_u32(b, seqno); 176 /* reset HMAC context */ 177 if (ssh_hmac_init(mac->hmac_ctx, NULL, 0) < 0 || 178 ssh_hmac_update(mac->hmac_ctx, b, sizeof(b)) < 0 || 179 ssh_hmac_update(mac->hmac_ctx, data, datalen) < 0 || 180 ssh_hmac_final(mac->hmac_ctx, u.m, sizeof(u.m)) < 0) 181 return SSH_ERR_LIBCRYPTO_ERROR; 182 break; 183 case SSH_UMAC: 184 POKE_U64(nonce, seqno); 185 umac_update(mac->umac_ctx, data, datalen); 186 umac_final(mac->umac_ctx, u.m, nonce); 187 break; 188 case SSH_UMAC128: 189 put_u64(nonce, seqno); 190 umac128_update(mac->umac_ctx, data, datalen); 191 umac128_final(mac->umac_ctx, u.m, nonce); 192 break; 193 default: 194 return SSH_ERR_INVALID_ARGUMENT; 195 } 196 if (digest != NULL) { 197 if (dlen > mac->mac_len) 198 dlen = mac->mac_len; 199 memcpy(digest, u.m, dlen); 200 } 201 return 0; 202 } 203 204 int 205 mac_check(struct sshmac *mac, u_int32_t seqno, 206 const u_char *data, size_t dlen, 207 const u_char *theirmac, size_t mlen) 208 { 209 u_char ourmac[SSH_DIGEST_MAX_LENGTH]; 210 int r; 211 212 if (mac->mac_len > mlen) 213 return SSH_ERR_INVALID_ARGUMENT; 214 if ((r = mac_compute(mac, seqno, data, dlen, 215 ourmac, sizeof(ourmac))) != 0) 216 return r; 217 if (timingsafe_bcmp(ourmac, theirmac, mac->mac_len) != 0) 218 return SSH_ERR_MAC_INVALID; 219 return 0; 220 } 221 222 void 223 mac_clear(struct sshmac *mac) 224 { 225 if (mac->type == SSH_UMAC) { 226 if (mac->umac_ctx != NULL) 227 umac_delete(mac->umac_ctx); 228 } else if (mac->type == SSH_UMAC128) { 229 if (mac->umac_ctx != NULL) 230 umac128_delete(mac->umac_ctx); 231 } else if (mac->hmac_ctx != NULL) 232 ssh_hmac_free(mac->hmac_ctx); 233 mac->hmac_ctx = NULL; 234 mac->umac_ctx = NULL; 235 } 236 237 /* XXX copied from ciphers_valid */ 238 #define MAC_SEP "," 239 int 240 mac_valid(const char *names) 241 { 242 char *maclist, *cp, *p; 243 244 if (names == NULL || strcmp(names, "") == 0) 245 return 0; 246 if ((maclist = cp = strdup(names)) == NULL) 247 return 0; 248 for ((p = strsep(&cp, MAC_SEP)); p && *p != '\0'; 249 (p = strsep(&cp, MAC_SEP))) { 250 if (mac_setup(NULL, p) < 0) { 251 free(maclist); 252 return 0; 253 } 254 } 255 free(maclist); 256 return 1; 257 } 258