crypto/openssh/mac.c

   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 "includes.h"
  27
  28 #include <sys/types.h>
  29
  30 #include <string.h>
  31 #include <stdio.h>
  32
  33 #include "digest.h"
  34 #include "hmac.h"
  35 #include "umac.h"
  36 #include "mac.h"
  37 #include "misc.h"
  38 #include "ssherr.h"
  39 #include "sshbuf.h"
  40
  41 #include "openbsd-compat/openssl-compat.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         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 #ifdef HAVE_EVP_SHA256
  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 #endif
  65         { "hmac-md5",                           SSH_DIGEST, SSH_DIGEST_MD5, 0, 0, 0, 0 },
  66         { "hmac-md5-96",                        SSH_DIGEST, SSH_DIGEST_MD5, 96, 0, 0, 0 },
  67         { "umac-64@openssh.com",                SSH_UMAC, 0, 0, 128, 64, 0 },
  68         { "umac-128@openssh.com",               SSH_UMAC128, 0, 0, 128, 128, 0 },
  69
  70         /* Encrypt-then-MAC variants */
  71         { "hmac-sha1-etm@openssh.com",          SSH_DIGEST, SSH_DIGEST_SHA1, 0, 0, 0, 1 },
  72         { "hmac-sha1-96-etm@openssh.com",       SSH_DIGEST, SSH_DIGEST_SHA1, 96, 0, 0, 1 },
  73 #ifdef HAVE_EVP_SHA256
  74         { "hmac-sha2-256-etm@openssh.com",      SSH_DIGEST, SSH_DIGEST_SHA256, 0, 0, 0, 1 },
  75         { "hmac-sha2-512-etm@openssh.com",      SSH_DIGEST, SSH_DIGEST_SHA512, 0, 0, 0, 1 },
  76 #endif
  77         { "hmac-md5-etm@openssh.com",           SSH_DIGEST, SSH_DIGEST_MD5, 0, 0, 0, 1 },
  78         { "hmac-md5-96-etm@openssh.com",        SSH_DIGEST, SSH_DIGEST_MD5, 96, 0, 0, 1 },
  79         { "umac-64-etm@openssh.com",            SSH_UMAC, 0, 0, 128, 64, 1 },
  80         { "umac-128-etm@openssh.com",           SSH_UMAC128, 0, 0, 128, 128, 1 },
  81
  82         { NULL,                                 0, 0, 0, 0, 0, 0 }
  83 };
  84
  85 /* Returns a list of supported MACs separated by the specified char. */
  86 char *
  87 mac_alg_list(char sep)
  88 {
  89         char *ret = NULL, *tmp;
  90         size_t nlen, rlen = 0;
  91         const struct macalg *m;
  92
  93         for (m = macs; m->name != NULL; m++) {
  94                 if (ret != NULL)
  95                         ret[rlen++] = sep;
  96                 nlen = strlen(m->name);
  97                 if ((tmp = realloc(ret, rlen + nlen + 2)) == NULL) {
  98                         free(ret);
  99                         return NULL;
 100                 }
 101                 ret = tmp;
 102                 memcpy(ret + rlen, m->name, nlen + 1);
 103                 rlen += nlen;
 104         }
 105         return ret;
 106 }
 107
 108 static int
 109 mac_setup_by_alg(struct sshmac *mac, const struct macalg *macalg)
 110 {
 111         mac->type = macalg->type;
 112         if (mac->type == SSH_DIGEST) {
 113                 if ((mac->hmac_ctx = ssh_hmac_start(macalg->alg)) == NULL)
 114                         return SSH_ERR_ALLOC_FAIL;
 115                 mac->key_len = mac->mac_len = ssh_hmac_bytes(macalg->alg);
 116         } else {
 117                 mac->mac_len = macalg->len / 8;
 118                 mac->key_len = macalg->key_len / 8;
 119                 mac->umac_ctx = NULL;
 120         }
 121         if (macalg->truncatebits != 0)
 122                 mac->mac_len = macalg->truncatebits / 8;
 123         mac->etm = macalg->etm;
 124         return 0;
 125 }
 126
 127 int
 128 mac_setup(struct sshmac *mac, char *name)
 129 {
 130         const struct macalg *m;
 131
 132         for (m = macs; m->name != NULL; m++) {
 133                 if (strcmp(name, m->name) != 0)
 134                         continue;
 135                 if (mac != NULL)
 136                         return mac_setup_by_alg(mac, m);
 137                 return 0;
 138         }
 139         return SSH_ERR_INVALID_ARGUMENT;
 140 }
 141
 142 int
 143 mac_init(struct sshmac *mac)
 144 {
 145         if (mac->key == NULL)
 146                 return SSH_ERR_INVALID_ARGUMENT;
 147         switch (mac->type) {
 148         case SSH_DIGEST:
 149                 if (mac->hmac_ctx == NULL ||
 150                     ssh_hmac_init(mac->hmac_ctx, mac->key, mac->key_len) < 0)
 151                         return SSH_ERR_INVALID_ARGUMENT;
 152                 return 0;
 153         case SSH_UMAC:
 154                 if ((mac->umac_ctx = umac_new(mac->key)) == NULL)
 155                         return SSH_ERR_ALLOC_FAIL;
 156                 return 0;
 157         case SSH_UMAC128:
 158                 if ((mac->umac_ctx = umac128_new(mac->key)) == NULL)
 159                         return SSH_ERR_ALLOC_FAIL;
 160                 return 0;
 161         default:
 162                 return SSH_ERR_INVALID_ARGUMENT;
 163         }
 164 }
 165
 166 int
 167 mac_compute(struct sshmac *mac, u_int32_t seqno,
 168     const u_char *data, int datalen,
 169     u_char *digest, size_t dlen)
 170 {
 171         static union {
 172                 u_char m[SSH_DIGEST_MAX_LENGTH];
 173                 u_int64_t for_align;
 174         } u;
 175         u_char b[4];
 176         u_char nonce[8];
 177
 178         if (mac->mac_len > sizeof(u))
 179                 return SSH_ERR_INTERNAL_ERROR;
 180
 181         switch (mac->type) {
 182         case SSH_DIGEST:
 183                 put_u32(b, seqno);
 184                 /* reset HMAC context */
 185                 if (ssh_hmac_init(mac->hmac_ctx, NULL, 0) < 0 ||
 186                     ssh_hmac_update(mac->hmac_ctx, b, sizeof(b)) < 0 ||
 187                     ssh_hmac_update(mac->hmac_ctx, data, datalen) < 0 ||
 188                     ssh_hmac_final(mac->hmac_ctx, u.m, sizeof(u.m)) < 0)
 189                         return SSH_ERR_LIBCRYPTO_ERROR;
 190                 break;
 191         case SSH_UMAC:
 192                 POKE_U64(nonce, seqno);
 193                 umac_update(mac->umac_ctx, data, datalen);
 194                 umac_final(mac->umac_ctx, u.m, nonce);
 195                 break;
 196         case SSH_UMAC128:
 197                 put_u64(nonce, seqno);
 198                 umac128_update(mac->umac_ctx, data, datalen);
 199                 umac128_final(mac->umac_ctx, u.m, nonce);
 200                 break;
 201         default:
 202                 return SSH_ERR_INVALID_ARGUMENT;
 203         }
 204         if (digest != NULL) {
 205                 if (dlen > mac->mac_len)
 206                         dlen = mac->mac_len;
 207                 memcpy(digest, u.m, dlen);
 208         }
 209         return 0;
 210 }
 211
 212 int
 213 mac_check(struct sshmac *mac, u_int32_t seqno,
 214     const u_char *data, size_t dlen,
 215     const u_char *theirmac, size_t mlen)
 216 {
 217         u_char ourmac[SSH_DIGEST_MAX_LENGTH];
 218         int r;
 219
 220         if (mac->mac_len > mlen)
 221                 return SSH_ERR_INVALID_ARGUMENT;
 222         if ((r = mac_compute(mac, seqno, data, dlen,
 223             ourmac, sizeof(ourmac))) != 0)
 224                 return r;
 225         if (timingsafe_bcmp(ourmac, theirmac, mac->mac_len) != 0)
 226                 return SSH_ERR_MAC_INVALID;
 227         return 0;
 228 }
 229
 230 void
 231 mac_clear(struct sshmac *mac)
 232 {
 233         if (mac->type == SSH_UMAC) {
 234                 if (mac->umac_ctx != NULL)
 235                         umac_delete(mac->umac_ctx);
 236         } else if (mac->type == SSH_UMAC128) {
 237                 if (mac->umac_ctx != NULL)
 238                         umac128_delete(mac->umac_ctx);
 239         } else if (mac->hmac_ctx != NULL)
 240                 ssh_hmac_free(mac->hmac_ctx);
 241         mac->hmac_ctx = NULL;
 242         mac->umac_ctx = NULL;
 243 }
 244
 245 /* XXX copied from ciphers_valid */
 246 #define MAC_SEP ","
 247 int
 248 mac_valid(const char *names)
 249 {
 250         char *maclist, *cp, *p;
 251
 252         if (names == NULL || strcmp(names, "") == 0)
 253                 return 0;
 254         if ((maclist = cp = strdup(names)) == NULL)
 255                 return 0;
 256         for ((p = strsep(&cp, MAC_SEP)); p && *p != '\0';
 257             (p = strsep(&cp, MAC_SEP))) {
 258                 if (mac_setup(NULL, p) < 0) {
 259                         free(maclist);
 260                         return 0;
 261                 }
 262         }
 263         free(maclist);
 264         return 1;
 265 }