crypto/openssh/mac.c

   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 "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         { "hmac-ripemd160",                     SSH_DIGEST, SSH_DIGEST_RIPEMD160, 0, 0, 0, 0 },
  68         { "hmac-ripemd160@openssh.com",         SSH_DIGEST, SSH_DIGEST_RIPEMD160, 0, 0, 0, 0 },
  69         { "umac-64@openssh.com",                SSH_UMAC, 0, 0, 128, 64, 0 },
  70         { "umac-128@openssh.com",               SSH_UMAC128, 0, 0, 128, 128, 0 },
  71
  72         /* Encrypt-then-MAC variants */
  73         { "hmac-sha1-etm@openssh.com",          SSH_DIGEST, SSH_DIGEST_SHA1, 0, 0, 0, 1 },
  74         { "hmac-sha1-96-etm@openssh.com",       SSH_DIGEST, SSH_DIGEST_SHA1, 96, 0, 0, 1 },
  75 #ifdef HAVE_EVP_SHA256
  76         { "hmac-sha2-256-etm@openssh.com",      SSH_DIGEST, SSH_DIGEST_SHA256, 0, 0, 0, 1 },
  77         { "hmac-sha2-512-etm@openssh.com",      SSH_DIGEST, SSH_DIGEST_SHA512, 0, 0, 0, 1 },
  78 #endif
  79         { "hmac-md5-etm@openssh.com",           SSH_DIGEST, SSH_DIGEST_MD5, 0, 0, 0, 1 },
  80         { "hmac-md5-96-etm@openssh.com",        SSH_DIGEST, SSH_DIGEST_MD5, 96, 0, 0, 1 },
  81         { "hmac-ripemd160-etm@openssh.com",     SSH_DIGEST, SSH_DIGEST_RIPEMD160, 0, 0, 0, 1 },
  82         { "umac-64-etm@openssh.com",            SSH_UMAC, 0, 0, 128, 64, 1 },
  83         { "umac-128-etm@openssh.com",           SSH_UMAC128, 0, 0, 128, 128, 1 },
  84
  85         { NULL,                                 0, 0, 0, 0, 0, 0 }
  86 };
  87
  88 /* Returns a list of supported MACs separated by the specified char. */
  89 char *
  90 mac_alg_list(char sep)
  91 {
  92         char *ret = NULL, *tmp;
  93         size_t nlen, rlen = 0;
  94         const struct macalg *m;
  95
  96         for (m = macs; m->name != NULL; m++) {
  97                 if (ret != NULL)
  98                         ret[rlen++] = sep;
  99                 nlen = strlen(m->name);
 100                 if ((tmp = realloc(ret, rlen + nlen + 2)) == NULL) {
 101                         free(ret);
 102                         return NULL;
 103                 }
 104                 ret = tmp;
 105                 memcpy(ret + rlen, m->name, nlen + 1);
 106                 rlen += nlen;
 107         }
 108         return ret;
 109 }
 110
 111 static int
 112 mac_setup_by_alg(struct sshmac *mac, const struct macalg *macalg)
 113 {
 114         mac->type = macalg->type;
 115         if (mac->type == SSH_DIGEST) {
 116                 if ((mac->hmac_ctx = ssh_hmac_start(macalg->alg)) == NULL)
 117                         return SSH_ERR_ALLOC_FAIL;
 118                 mac->key_len = mac->mac_len = ssh_hmac_bytes(macalg->alg);
 119         } else {
 120                 mac->mac_len = macalg->len / 8;
 121                 mac->key_len = macalg->key_len / 8;
 122                 mac->umac_ctx = NULL;
 123         }
 124         if (macalg->truncatebits != 0)
 125                 mac->mac_len = macalg->truncatebits / 8;
 126         mac->etm = macalg->etm;
 127         return 0;
 128 }
 129
 130 int
 131 mac_setup(struct sshmac *mac, char *name)
 132 {
 133         const struct macalg *m;
 134
 135         for (m = macs; m->name != NULL; m++) {
 136                 if (strcmp(name, m->name) != 0)
 137                         continue;
 138                 if (mac != NULL)
 139                         return mac_setup_by_alg(mac, m);
 140                 return 0;
 141         }
 142         return SSH_ERR_INVALID_ARGUMENT;
 143 }
 144
 145 int
 146 mac_init(struct sshmac *mac)
 147 {
 148         if (mac->key == NULL)
 149                 return SSH_ERR_INVALID_ARGUMENT;
 150         switch (mac->type) {
 151         case SSH_DIGEST:
 152                 if (mac->hmac_ctx == NULL ||
 153                     ssh_hmac_init(mac->hmac_ctx, mac->key, mac->key_len) < 0)
 154                         return SSH_ERR_INVALID_ARGUMENT;
 155                 return 0;
 156         case SSH_UMAC:
 157                 if ((mac->umac_ctx = umac_new(mac->key)) == NULL)
 158                         return SSH_ERR_ALLOC_FAIL;
 159                 return 0;
 160         case SSH_UMAC128:
 161                 if ((mac->umac_ctx = umac128_new(mac->key)) == NULL)
 162                         return SSH_ERR_ALLOC_FAIL;
 163                 return 0;
 164         default:
 165                 return SSH_ERR_INVALID_ARGUMENT;
 166         }
 167 }
 168
 169 int
 170 mac_compute(struct sshmac *mac, u_int32_t seqno,
 171     const u_char *data, int datalen,
 172     u_char *digest, size_t dlen)
 173 {
 174         static union {
 175                 u_char m[SSH_DIGEST_MAX_LENGTH];
 176                 u_int64_t for_align;
 177         } u;
 178         u_char b[4];
 179         u_char nonce[8];
 180
 181         if (mac->mac_len > sizeof(u))
 182                 return SSH_ERR_INTERNAL_ERROR;
 183
 184         switch (mac->type) {
 185         case SSH_DIGEST:
 186                 put_u32(b, seqno);
 187                 /* reset HMAC context */
 188                 if (ssh_hmac_init(mac->hmac_ctx, NULL, 0) < 0 ||
 189                     ssh_hmac_update(mac->hmac_ctx, b, sizeof(b)) < 0 ||
 190                     ssh_hmac_update(mac->hmac_ctx, data, datalen) < 0 ||
 191                     ssh_hmac_final(mac->hmac_ctx, u.m, sizeof(u.m)) < 0)
 192                         return SSH_ERR_LIBCRYPTO_ERROR;
 193                 break;
 194         case SSH_UMAC:
 195                 POKE_U64(nonce, seqno);
 196                 umac_update(mac->umac_ctx, data, datalen);
 197                 umac_final(mac->umac_ctx, u.m, nonce);
 198                 break;
 199         case SSH_UMAC128:
 200                 put_u64(nonce, seqno);
 201                 umac128_update(mac->umac_ctx, data, datalen);
 202                 umac128_final(mac->umac_ctx, u.m, nonce);
 203                 break;
 204         default:
 205                 return SSH_ERR_INVALID_ARGUMENT;
 206         }
 207         if (digest != NULL) {
 208                 if (dlen > mac->mac_len)
 209                         dlen = mac->mac_len;
 210                 memcpy(digest, u.m, dlen);
 211         }
 212         return 0;
 213 }
 214
 215 int
 216 mac_check(struct sshmac *mac, u_int32_t seqno,
 217     const u_char *data, size_t dlen,
 218     const u_char *theirmac, size_t mlen)
 219 {
 220         u_char ourmac[SSH_DIGEST_MAX_LENGTH];
 221         int r;
 222
 223         if (mac->mac_len > mlen)
 224                 return SSH_ERR_INVALID_ARGUMENT;
 225         if ((r = mac_compute(mac, seqno, data, dlen,
 226             ourmac, sizeof(ourmac))) != 0)
 227                 return r;
 228         if (timingsafe_bcmp(ourmac, theirmac, mac->mac_len) != 0)
 229                 return SSH_ERR_MAC_INVALID;
 230         return 0;
 231 }
 232
 233 void
 234 mac_clear(struct sshmac *mac)
 235 {
 236         if (mac->type == SSH_UMAC) {
 237                 if (mac->umac_ctx != NULL)
 238                         umac_delete(mac->umac_ctx);
 239         } else if (mac->type == SSH_UMAC128) {
 240                 if (mac->umac_ctx != NULL)
 241                         umac128_delete(mac->umac_ctx);
 242         } else if (mac->hmac_ctx != NULL)
 243                 ssh_hmac_free(mac->hmac_ctx);
 244         mac->hmac_ctx = NULL;
 245         mac->umac_ctx = NULL;
 246 }
 247
 248 /* XXX copied from ciphers_valid */
 249 #define MAC_SEP ","
 250 int
 251 mac_valid(const char *names)
 252 {
 253         char *maclist, *cp, *p;
 254
 255         if (names == NULL || strcmp(names, "") == 0)
 256                 return 0;
 257         if ((maclist = cp = strdup(names)) == NULL)
 258                 return 0;
 259         for ((p = strsep(&cp, MAC_SEP)); p && *p != '\0';
 260             (p = strsep(&cp, MAC_SEP))) {
 261                 if (mac_setup(NULL, p) < 0) {
 262                         free(maclist);
 263                         return 0;
 264                 }
 265         }
 266         free(maclist);
 267         return 1;
 268 }