1 /* $NetBSD: mac.c,v 1.15 2017/10/07 19:39:19 christos Exp $ */ 2 /* $OpenBSD: mac.c,v 1.34 2017/05/08 22:57:38 djm Exp $ */ 3 /* 4 * Copyright (c) 2001 Markus Friedl. All rights reserved. 5 * 6 * Redistribution and use in source and binary forms, with or without 7 * modification, are permitted provided that the following conditions 8 * are met: 9 * 1. Redistributions of source code must retain the above copyright 10 * notice, this list of conditions and the following disclaimer. 11 * 2. Redistributions in binary form must reproduce the above copyright 12 * notice, this list of conditions and the following disclaimer in the 13 * documentation and/or other materials provided with the distribution. 14 * 15 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 16 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 17 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 18 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 19 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 20 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 21 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 22 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 23 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 24 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 25 */ 26 27 #include "includes.h" 28 __RCSID("$NetBSD: mac.c,v 1.15 2017/10/07 19:39:19 christos Exp $"); 29 #include <sys/types.h> 30 31 #include <string.h> 32 #include <stdio.h> 33 #include <time.h> 34 35 #include "digest.h" 36 #include "hmac.h" 37 #include "umac.h" 38 #include "mac.h" 39 #include "misc.h" 40 #include "ssherr.h" 41 #include "sshbuf.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 const 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 { "hmac-sha2-256", SSH_DIGEST, SSH_DIGEST_SHA256, 0, 0, 0, 0 }, 62 { "hmac-sha2-512", SSH_DIGEST, SSH_DIGEST_SHA512, 0, 0, 0, 0 }, 63 { "hmac-md5", SSH_DIGEST, SSH_DIGEST_MD5, 0, 0, 0, 0 }, 64 { "hmac-md5-96", SSH_DIGEST, SSH_DIGEST_MD5, 96, 0, 0, 0 }, 65 { "umac-64@openssh.com", SSH_UMAC, 0, 0, 128, 64, 0 }, 66 { "umac-128@openssh.com", SSH_UMAC128, 0, 0, 128, 128, 0 }, 67 68 /* Encrypt-then-MAC variants */ 69 { "hmac-sha1-etm@openssh.com", SSH_DIGEST, SSH_DIGEST_SHA1, 0, 0, 0, 1 }, 70 { "hmac-sha1-96-etm@openssh.com", SSH_DIGEST, SSH_DIGEST_SHA1, 96, 0, 0, 1 }, 71 { "hmac-sha2-256-etm@openssh.com", SSH_DIGEST, SSH_DIGEST_SHA256, 0, 0, 0, 1 }, 72 { "hmac-sha2-512-etm@openssh.com", SSH_DIGEST, SSH_DIGEST_SHA512, 0, 0, 0, 1 }, 73 { "hmac-md5-etm@openssh.com", SSH_DIGEST, SSH_DIGEST_MD5, 0, 0, 0, 1 }, 74 { "hmac-md5-96-etm@openssh.com", SSH_DIGEST, SSH_DIGEST_MD5, 96, 0, 0, 1 }, 75 { "umac-64-etm@openssh.com", SSH_UMAC, 0, 0, 128, 64, 1 }, 76 { "umac-128-etm@openssh.com", SSH_UMAC128, 0, 0, 128, 128, 1 }, 77 78 { NULL, 0, 0, 0, 0, 0, 0 } 79 }; 80 81 /* Returns a list of supported MACs separated by the specified char. */ 82 char * 83 mac_alg_list(char sep) 84 { 85 char *ret = NULL, *tmp; 86 size_t nlen, rlen = 0; 87 const struct macalg *m; 88 89 for (m = macs; m->name != NULL; m++) { 90 if (ret != NULL) 91 ret[rlen++] = sep; 92 nlen = strlen(m->name); 93 if ((tmp = realloc(ret, rlen + nlen + 2)) == NULL) { 94 free(ret); 95 return NULL; 96 } 97 ret = tmp; 98 memcpy(ret + rlen, m->name, nlen + 1); 99 rlen += nlen; 100 } 101 return ret; 102 } 103 104 static int 105 mac_setup_by_alg(struct sshmac *mac, const struct macalg *macalg) 106 { 107 mac->type = macalg->type; 108 if (mac->type == SSH_DIGEST) { 109 if ((mac->hmac_ctx = ssh_hmac_start(macalg->alg)) == NULL) 110 return SSH_ERR_ALLOC_FAIL; 111 mac->key_len = mac->mac_len = ssh_hmac_bytes(macalg->alg); 112 } else { 113 mac->mac_len = macalg->len / 8; 114 mac->key_len = macalg->key_len / 8; 115 mac->umac_ctx = NULL; 116 } 117 if (macalg->truncatebits != 0) 118 mac->mac_len = macalg->truncatebits / 8; 119 mac->etm = macalg->etm; 120 return 0; 121 } 122 123 int 124 mac_setup(struct sshmac *mac, char *name) 125 { 126 const struct macalg *m; 127 128 for (m = macs; m->name != NULL; m++) { 129 if (strcmp(name, m->name) != 0) 130 continue; 131 if (mac != NULL) 132 return mac_setup_by_alg(mac, m); 133 return 0; 134 } 135 return SSH_ERR_INVALID_ARGUMENT; 136 } 137 138 int 139 mac_init(struct sshmac *mac) 140 { 141 if (mac->key == NULL) 142 return SSH_ERR_INVALID_ARGUMENT; 143 switch (mac->type) { 144 case SSH_DIGEST: 145 if (mac->hmac_ctx == NULL || 146 ssh_hmac_init(mac->hmac_ctx, mac->key, mac->key_len) < 0) 147 return SSH_ERR_INVALID_ARGUMENT; 148 return 0; 149 case SSH_UMAC: 150 if ((mac->umac_ctx = umac_new(mac->key)) == NULL) 151 return SSH_ERR_ALLOC_FAIL; 152 return 0; 153 case SSH_UMAC128: 154 if ((mac->umac_ctx = umac128_new(mac->key)) == NULL) 155 return SSH_ERR_ALLOC_FAIL; 156 return 0; 157 default: 158 return SSH_ERR_INVALID_ARGUMENT; 159 } 160 } 161 162 int 163 mac_compute(struct sshmac *mac, u_int32_t seqno, 164 const u_char *data, int datalen, 165 u_char *digest, size_t dlen) 166 { 167 static union { 168 u_char m[SSH_DIGEST_MAX_LENGTH]; 169 u_int64_t for_align; 170 } u; 171 u_char b[4]; 172 u_char nonce[8]; 173 174 if (mac->mac_len > sizeof(u)) 175 return SSH_ERR_INTERNAL_ERROR; 176 177 switch (mac->type) { 178 case SSH_DIGEST: 179 put_u32(b, seqno); 180 /* reset HMAC context */ 181 if (ssh_hmac_init(mac->hmac_ctx, NULL, 0) < 0 || 182 ssh_hmac_update(mac->hmac_ctx, b, sizeof(b)) < 0 || 183 ssh_hmac_update(mac->hmac_ctx, data, datalen) < 0 || 184 ssh_hmac_final(mac->hmac_ctx, u.m, sizeof(u.m)) < 0) 185 return SSH_ERR_LIBCRYPTO_ERROR; 186 break; 187 case SSH_UMAC: 188 POKE_U64(nonce, seqno); 189 umac_update(mac->umac_ctx, data, datalen); 190 umac_final(mac->umac_ctx, u.m, nonce); 191 break; 192 case SSH_UMAC128: 193 put_u64(nonce, seqno); 194 umac128_update(mac->umac_ctx, data, datalen); 195 umac128_final(mac->umac_ctx, u.m, nonce); 196 break; 197 default: 198 return SSH_ERR_INVALID_ARGUMENT; 199 } 200 if (digest != NULL) { 201 if (dlen > mac->mac_len) 202 dlen = mac->mac_len; 203 memcpy(digest, u.m, dlen); 204 } 205 return 0; 206 } 207 208 int 209 mac_check(struct sshmac *mac, u_int32_t seqno, 210 const u_char *data, size_t dlen, 211 const u_char *theirmac, size_t mlen) 212 { 213 u_char ourmac[SSH_DIGEST_MAX_LENGTH]; 214 int r; 215 216 if (mac->mac_len > mlen) 217 return SSH_ERR_INVALID_ARGUMENT; 218 if ((r = mac_compute(mac, seqno, data, dlen, 219 ourmac, sizeof(ourmac))) != 0) 220 return r; 221 if (timingsafe_bcmp(ourmac, theirmac, mac->mac_len) != 0) 222 return SSH_ERR_MAC_INVALID; 223 return 0; 224 } 225 226 void 227 mac_clear(struct sshmac *mac) 228 { 229 if (mac->type == SSH_UMAC) { 230 if (mac->umac_ctx != NULL) 231 umac_delete(mac->umac_ctx); 232 } else if (mac->type == SSH_UMAC128) { 233 if (mac->umac_ctx != NULL) 234 umac128_delete(mac->umac_ctx); 235 } else if (mac->hmac_ctx != NULL) 236 ssh_hmac_free(mac->hmac_ctx); 237 mac->hmac_ctx = NULL; 238 mac->umac_ctx = NULL; 239 } 240 241 /* XXX copied from ciphers_valid */ 242 #define MAC_SEP "," 243 int 244 mac_valid(const char *names) 245 { 246 char *maclist, *cp, *p; 247 248 if (names == NULL || strcmp(names, "") == 0) 249 return 0; 250 if ((maclist = cp = strdup(names)) == NULL) 251 return 0; 252 for ((p = strsep(&cp, MAC_SEP)); p && *p != '\0'; 253 (p = strsep(&cp, MAC_SEP))) { 254 if (mac_setup(NULL, p) < 0) { 255 free(maclist); 256 return 0; 257 } 258 } 259 free(maclist); 260 return 1; 261 } 262