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 <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 { "hmac-ripemd160", SSH_DIGEST, SSH_DIGEST_RIPEMD160, 0, 0, 0, 0 }, 62 { "hmac-ripemd160@openssh.com", SSH_DIGEST, SSH_DIGEST_RIPEMD160, 0, 0, 0, 0 }, 63 { "umac-64@openssh.com", SSH_UMAC, 0, 0, 128, 64, 0 }, 64 { "umac-128@openssh.com", SSH_UMAC128, 0, 0, 128, 128, 0 }, 65 66 /* Encrypt-then-MAC variants */ 67 { "hmac-sha1-etm@openssh.com", SSH_DIGEST, SSH_DIGEST_SHA1, 0, 0, 0, 1 }, 68 { "hmac-sha1-96-etm@openssh.com", SSH_DIGEST, SSH_DIGEST_SHA1, 96, 0, 0, 1 }, 69 { "hmac-sha2-256-etm@openssh.com", SSH_DIGEST, SSH_DIGEST_SHA256, 0, 0, 0, 1 }, 70 { "hmac-sha2-512-etm@openssh.com", SSH_DIGEST, SSH_DIGEST_SHA512, 0, 0, 0, 1 }, 71 { "hmac-md5-etm@openssh.com", SSH_DIGEST, SSH_DIGEST_MD5, 0, 0, 0, 1 }, 72 { "hmac-md5-96-etm@openssh.com", SSH_DIGEST, SSH_DIGEST_MD5, 96, 0, 0, 1 }, 73 { "hmac-ripemd160-etm@openssh.com", SSH_DIGEST, SSH_DIGEST_RIPEMD160, 0, 0, 0, 1 }, 74 { "umac-64-etm@openssh.com", SSH_UMAC, 0, 0, 128, 64, 1 }, 75 { "umac-128-etm@openssh.com", SSH_UMAC128, 0, 0, 128, 128, 1 }, 76 77 { NULL, 0, 0, 0, 0, 0, 0 } 78 }; 79 80 /* Returns a list of supported MACs separated by the specified char. */ 81 char * 82 mac_alg_list(char sep) 83 { 84 char *ret = NULL, *tmp; 85 size_t nlen, rlen = 0; 86 const struct macalg *m; 87 88 for (m = macs; m->name != NULL; m++) { 89 if (ret != NULL) 90 ret[rlen++] = sep; 91 nlen = strlen(m->name); 92 if ((tmp = realloc(ret, rlen + nlen + 2)) == NULL) { 93 free(ret); 94 return NULL; 95 } 96 ret = tmp; 97 memcpy(ret + rlen, m->name, nlen + 1); 98 rlen += nlen; 99 } 100 return ret; 101 } 102 103 static int 104 mac_setup_by_alg(struct sshmac *mac, const struct macalg *macalg) 105 { 106 mac->type = macalg->type; 107 if (mac->type == SSH_DIGEST) { 108 if ((mac->hmac_ctx = ssh_hmac_start(macalg->alg)) == NULL) 109 return SSH_ERR_ALLOC_FAIL; 110 mac->key_len = mac->mac_len = ssh_hmac_bytes(macalg->alg); 111 } else { 112 mac->mac_len = macalg->len / 8; 113 mac->key_len = macalg->key_len / 8; 114 mac->umac_ctx = NULL; 115 } 116 if (macalg->truncatebits != 0) 117 mac->mac_len = macalg->truncatebits / 8; 118 mac->etm = macalg->etm; 119 return 0; 120 } 121 122 int 123 mac_setup(struct sshmac *mac, char *name) 124 { 125 const struct macalg *m; 126 127 for (m = macs; m->name != NULL; m++) { 128 if (strcmp(name, m->name) != 0) 129 continue; 130 if (mac != NULL) 131 return mac_setup_by_alg(mac, m); 132 return 0; 133 } 134 return SSH_ERR_INVALID_ARGUMENT; 135 } 136 137 int 138 mac_init(struct sshmac *mac) 139 { 140 if (mac->key == NULL) 141 return SSH_ERR_INVALID_ARGUMENT; 142 switch (mac->type) { 143 case SSH_DIGEST: 144 if (mac->hmac_ctx == NULL || 145 ssh_hmac_init(mac->hmac_ctx, mac->key, mac->key_len) < 0) 146 return SSH_ERR_INVALID_ARGUMENT; 147 return 0; 148 case SSH_UMAC: 149 if ((mac->umac_ctx = umac_new(mac->key)) == NULL) 150 return SSH_ERR_ALLOC_FAIL; 151 return 0; 152 case SSH_UMAC128: 153 if ((mac->umac_ctx = umac128_new(mac->key)) == NULL) 154 return SSH_ERR_ALLOC_FAIL; 155 return 0; 156 default: 157 return SSH_ERR_INVALID_ARGUMENT; 158 } 159 } 160 161 int 162 mac_compute(struct sshmac *mac, u_int32_t seqno, 163 const u_char *data, int datalen, 164 u_char *digest, size_t dlen) 165 { 166 static union { 167 u_char m[SSH_DIGEST_MAX_LENGTH]; 168 u_int64_t for_align; 169 } u; 170 u_char b[4]; 171 u_char nonce[8]; 172 173 if (mac->mac_len > sizeof(u)) 174 return SSH_ERR_INTERNAL_ERROR; 175 176 switch (mac->type) { 177 case SSH_DIGEST: 178 put_u32(b, seqno); 179 /* reset HMAC context */ 180 if (ssh_hmac_init(mac->hmac_ctx, NULL, 0) < 0 || 181 ssh_hmac_update(mac->hmac_ctx, b, sizeof(b)) < 0 || 182 ssh_hmac_update(mac->hmac_ctx, data, datalen) < 0 || 183 ssh_hmac_final(mac->hmac_ctx, u.m, sizeof(u.m)) < 0) 184 return SSH_ERR_LIBCRYPTO_ERROR; 185 break; 186 case SSH_UMAC: 187 POKE_U64(nonce, seqno); 188 umac_update(mac->umac_ctx, data, datalen); 189 umac_final(mac->umac_ctx, u.m, nonce); 190 break; 191 case SSH_UMAC128: 192 put_u64(nonce, seqno); 193 umac128_update(mac->umac_ctx, data, datalen); 194 umac128_final(mac->umac_ctx, u.m, nonce); 195 break; 196 default: 197 return SSH_ERR_INVALID_ARGUMENT; 198 } 199 if (digest != NULL) { 200 if (dlen > mac->mac_len) 201 dlen = mac->mac_len; 202 memcpy(digest, u.m, dlen); 203 } 204 return 0; 205 } 206 207 int 208 mac_check(struct sshmac *mac, u_int32_t seqno, 209 const u_char *data, size_t dlen, 210 const u_char *theirmac, size_t mlen) 211 { 212 u_char ourmac[SSH_DIGEST_MAX_LENGTH]; 213 int r; 214 215 if (mac->mac_len > mlen) 216 return SSH_ERR_INVALID_ARGUMENT; 217 if ((r = mac_compute(mac, seqno, data, dlen, 218 ourmac, sizeof(ourmac))) != 0) 219 return r; 220 if (timingsafe_bcmp(ourmac, theirmac, mac->mac_len) != 0) 221 return SSH_ERR_MAC_INVALID; 222 return 0; 223 } 224 225 void 226 mac_clear(struct sshmac *mac) 227 { 228 if (mac->type == SSH_UMAC) { 229 if (mac->umac_ctx != NULL) 230 umac_delete(mac->umac_ctx); 231 } else if (mac->type == SSH_UMAC128) { 232 if (mac->umac_ctx != NULL) 233 umac128_delete(mac->umac_ctx); 234 } else if (mac->hmac_ctx != NULL) 235 ssh_hmac_free(mac->hmac_ctx); 236 mac->hmac_ctx = NULL; 237 mac->umac_ctx = NULL; 238 } 239 240 /* XXX copied from ciphers_valid */ 241 #define MAC_SEP "," 242 int 243 mac_valid(const char *names) 244 { 245 char *maclist, *cp, *p; 246 247 if (names == NULL || strcmp(names, "") == 0) 248 return 0; 249 if ((maclist = cp = strdup(names)) == NULL) 250 return 0; 251 for ((p = strsep(&cp, MAC_SEP)); p && *p != '\0'; 252 (p = strsep(&cp, MAC_SEP))) { 253 if (mac_setup(NULL, p) < 0) { 254 free(maclist); 255 return 0; 256 } 257 } 258 free(maclist); 259 return 1; 260 } 261