mac.c

   1 /* $OpenBSD: mac.c,v 1.35 2019/09/06 04:53:27 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 <stdlib.h>
  31 #include <string.h>
  32 #include <stdio.h>
  33
  34 #include "digest.h"
  35 #include "hmac.h"
  36 #include "umac.h"
  37 #include "mac.h"
  38 #include "misc.h"
  39 #include "ssherr.h"
  40 #include "sshbuf.h"
  41
  42 #include "openbsd-compat/openssl-compat.h"
  43
  44 #define SSH_DIGEST      1       /* SSH_DIGEST_XXX */
  45 #define SSH_UMAC        2       /* UMAC (not integrated with OpenSSL) */
  46 #define SSH_UMAC128     3
  47
  48 struct macalg {
  49         char            *name;
  50         int             type;
  51         int             alg;
  52         int             truncatebits;   /* truncate digest if != 0 */
  53         int             key_len;        /* just for UMAC */
  54         int             len;            /* just for UMAC */
  55         int             etm;            /* Encrypt-then-MAC */
  56 };
  57
  58 static const struct macalg macs[] = {
  59         /* Encrypt-and-MAC (encrypt-and-authenticate) variants */
  60         { "hmac-sha1",                          SSH_DIGEST, SSH_DIGEST_SHA1, 0, 0, 0, 0 },
  61         { "hmac-sha1-96",                       SSH_DIGEST, SSH_DIGEST_SHA1, 96, 0, 0, 0 },
  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         { "hmac-md5",                           SSH_DIGEST, SSH_DIGEST_MD5, 0, 0, 0, 0 },
  65         { "hmac-md5-96",                        SSH_DIGEST, SSH_DIGEST_MD5, 96, 0, 0, 0 },
  66         { "umac-64@openssh.com",                SSH_UMAC, 0, 0, 128, 64, 0 },
  67         { "umac-128@openssh.com",               SSH_UMAC128, 0, 0, 128, 128, 0 },
  68
  69         /* Encrypt-then-MAC variants */
  70         { "hmac-sha1-etm@openssh.com",          SSH_DIGEST, SSH_DIGEST_SHA1, 0, 0, 0, 1 },
  71         { "hmac-sha1-96-etm@openssh.com",       SSH_DIGEST, SSH_DIGEST_SHA1, 96, 0, 0, 1 },
  72         { "hmac-sha2-256-etm@openssh.com",      SSH_DIGEST, SSH_DIGEST_SHA256, 0, 0, 0, 1 },
  73         { "hmac-sha2-512-etm@openssh.com",      SSH_DIGEST, SSH_DIGEST_SHA512, 0, 0, 0, 1 },
  74         { "hmac-md5-etm@openssh.com",           SSH_DIGEST, SSH_DIGEST_MD5, 0, 0, 0, 1 },
  75         { "hmac-md5-96-etm@openssh.com",        SSH_DIGEST, SSH_DIGEST_MD5, 96, 0, 0, 1 },
  76         { "umac-64-etm@openssh.com",            SSH_UMAC, 0, 0, 128, 64, 1 },
  77         { "umac-128-etm@openssh.com",           SSH_UMAC128, 0, 0, 128, 128, 1 },
  78
  79         { NULL,                                 0, 0, 0, 0, 0, 0 }
  80 };
  81
  82 /* Returns a list of supported MACs separated by the specified char. */
  83 char *
  84 mac_alg_list(char sep)
  85 {
  86         char *ret = NULL, *tmp;
  87         size_t nlen, rlen = 0;
  88         const struct macalg *m;
  89
  90         for (m = macs; m->name != NULL; m++) {
  91                 if (ret != NULL)
  92                         ret[rlen++] = sep;
  93                 nlen = strlen(m->name);
  94                 if ((tmp = realloc(ret, rlen + nlen + 2)) == NULL) {
  95                         free(ret);
  96                         return NULL;
  97                 }
  98                 ret = tmp;
  99                 memcpy(ret + rlen, m->name, nlen + 1);
 100                 rlen += nlen;
 101         }
 102         return ret;
 103 }
 104
 105 static int
 106 mac_setup_by_alg(struct sshmac *mac, const struct macalg *macalg)
 107 {
 108         mac->type = macalg->type;
 109         if (mac->type == SSH_DIGEST) {
 110                 if ((mac->hmac_ctx = ssh_hmac_start(macalg->alg)) == NULL)
 111                         return SSH_ERR_ALLOC_FAIL;
 112                 mac->key_len = mac->mac_len = ssh_hmac_bytes(macalg->alg);
 113         } else {
 114                 mac->mac_len = macalg->len / 8;
 115                 mac->key_len = macalg->key_len / 8;
 116                 mac->umac_ctx = NULL;
 117         }
 118         if (macalg->truncatebits != 0)
 119                 mac->mac_len = macalg->truncatebits / 8;
 120         mac->etm = macalg->etm;
 121         return 0;
 122 }
 123
 124 int
 125 mac_setup(struct sshmac *mac, char *name)
 126 {
 127         const struct macalg *m;
 128
 129         for (m = macs; m->name != NULL; m++) {
 130                 if (strcmp(name, m->name) != 0)
 131                         continue;
 132                 if (mac != NULL)
 133                         return mac_setup_by_alg(mac, m);
 134                 return 0;
 135         }
 136         return SSH_ERR_INVALID_ARGUMENT;
 137 }
 138
 139 int
 140 mac_init(struct sshmac *mac)
 141 {
 142         if (mac->key == NULL)
 143                 return SSH_ERR_INVALID_ARGUMENT;
 144         switch (mac->type) {
 145         case SSH_DIGEST:
 146                 if (mac->hmac_ctx == NULL ||
 147                     ssh_hmac_init(mac->hmac_ctx, mac->key, mac->key_len) < 0)
 148                         return SSH_ERR_INVALID_ARGUMENT;
 149                 return 0;
 150         case SSH_UMAC:
 151                 if ((mac->umac_ctx = umac_new(mac->key)) == NULL)
 152                         return SSH_ERR_ALLOC_FAIL;
 153                 return 0;
 154         case SSH_UMAC128:
 155                 if ((mac->umac_ctx = umac128_new(mac->key)) == NULL)
 156                         return SSH_ERR_ALLOC_FAIL;
 157                 return 0;
 158         default:
 159                 return SSH_ERR_INVALID_ARGUMENT;
 160         }
 161 }
 162
 163 int
 164 mac_compute(struct sshmac *mac, u_int32_t seqno,
 165     const u_char *data, int datalen,
 166     u_char *digest, size_t dlen)
 167 {
 168         static union {
 169                 u_char m[SSH_DIGEST_MAX_LENGTH];
 170                 u_int64_t for_align;
 171         } u;
 172         u_char b[4];
 173         u_char nonce[8];
 174
 175         if (mac->mac_len > sizeof(u))
 176                 return SSH_ERR_INTERNAL_ERROR;
 177
 178         switch (mac->type) {
 179         case SSH_DIGEST:
 180                 put_u32(b, seqno);
 181                 /* reset HMAC context */
 182                 if (ssh_hmac_init(mac->hmac_ctx, NULL, 0) < 0 ||
 183                     ssh_hmac_update(mac->hmac_ctx, b, sizeof(b)) < 0 ||
 184                     ssh_hmac_update(mac->hmac_ctx, data, datalen) < 0 ||
 185                     ssh_hmac_final(mac->hmac_ctx, u.m, sizeof(u.m)) < 0)
 186                         return SSH_ERR_LIBCRYPTO_ERROR;
 187                 break;
 188         case SSH_UMAC:
 189                 POKE_U64(nonce, seqno);
 190                 umac_update(mac->umac_ctx, data, datalen);
 191                 umac_final(mac->umac_ctx, u.m, nonce);
 192                 break;
 193         case SSH_UMAC128:
 194                 put_u64(nonce, seqno);
 195                 umac128_update(mac->umac_ctx, data, datalen);
 196                 umac128_final(mac->umac_ctx, u.m, nonce);
 197                 break;
 198         default:
 199                 return SSH_ERR_INVALID_ARGUMENT;
 200         }
 201         if (digest != NULL) {
 202                 if (dlen > mac->mac_len)
 203                         dlen = mac->mac_len;
 204                 memcpy(digest, u.m, dlen);
 205         }
 206         return 0;
 207 }
 208
 209 int
 210 mac_check(struct sshmac *mac, u_int32_t seqno,
 211     const u_char *data, size_t dlen,
 212     const u_char *theirmac, size_t mlen)
 213 {
 214         u_char ourmac[SSH_DIGEST_MAX_LENGTH];
 215         int r;
 216
 217         if (mac->mac_len > mlen)
 218                 return SSH_ERR_INVALID_ARGUMENT;
 219         if ((r = mac_compute(mac, seqno, data, dlen,
 220             ourmac, sizeof(ourmac))) != 0)
 221                 return r;
 222         if (timingsafe_bcmp(ourmac, theirmac, mac->mac_len) != 0)
 223                 return SSH_ERR_MAC_INVALID;
 224         return 0;
 225 }
 226
 227 void
 228 mac_clear(struct sshmac *mac)
 229 {
 230         if (mac->type == SSH_UMAC) {
 231                 if (mac->umac_ctx != NULL)
 232                         umac_delete(mac->umac_ctx);
 233         } else if (mac->type == SSH_UMAC128) {
 234                 if (mac->umac_ctx != NULL)
 235                         umac128_delete(mac->umac_ctx);
 236         } else if (mac->hmac_ctx != NULL)
 237                 ssh_hmac_free(mac->hmac_ctx);
 238         mac->hmac_ctx = NULL;
 239         mac->umac_ctx = NULL;
 240 }
 241
 242 /* XXX copied from ciphers_valid */
 243 #define MAC_SEP ","
 244 int
 245 mac_valid(const char *names)
 246 {
 247         char *maclist, *cp, *p;
 248
 249         if (names == NULL || strcmp(names, "") == 0)
 250                 return 0;
 251         if ((maclist = cp = strdup(names)) == NULL)
 252                 return 0;
 253         for ((p = strsep(&cp, MAC_SEP)); p && *p != '\0';
 254             (p = strsep(&cp, MAC_SEP))) {
 255                 if (mac_setup(NULL, p) < 0) {
 256                         free(maclist);
 257                         return 0;
 258                 }
 259         }
 260         free(maclist);
 261         return 1;
 262 }