mac.c

   1 /* $OpenBSD: mac.c,v 1.15 2008/06/13 00:51:47 dtucker 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 <openssl/hmac.h>
  31
  32 #include <stdarg.h>
  33 #include <string.h>
  34 #include <signal.h>
  35
  36 #include "xmalloc.h"
  37 #include "log.h"
  38 #include "cipher.h"
  39 #include "buffer.h"
  40 #include "key.h"
  41 #include "kex.h"
  42 #include "mac.h"
  43 #include "misc.h"
  44
  45 #include "umac.h"
  46
  47 #define SSH_EVP         1       /* OpenSSL EVP-based MAC */
  48 #define SSH_UMAC        2       /* UMAC (not integrated with OpenSSL) */
  49
  50 struct {
  51         char            *name;
  52         int             type;
  53         const EVP_MD *  (*mdfunc)(void);
  54         int             truncatebits;   /* truncate digest if != 0 */
  55         int             key_len;        /* just for UMAC */
  56         int             len;            /* just for UMAC */
  57 } macs[] = {
  58         { "hmac-sha1",                  SSH_EVP, EVP_sha1, 0, -1, -1 },
  59         { "hmac-sha1-96",               SSH_EVP, EVP_sha1, 96, -1, -1 },
  60         { "hmac-md5",                   SSH_EVP, EVP_md5, 0, -1, -1 },
  61         { "hmac-md5-96",                SSH_EVP, EVP_md5, 96, -1, -1 },
  62         { "hmac-ripemd160",             SSH_EVP, EVP_ripemd160, 0, -1, -1 },
  63         { "hmac-ripemd160@openssh.com", SSH_EVP, EVP_ripemd160, 0, -1, -1 },
  64         { "umac-64@openssh.com",        SSH_UMAC, NULL, 0, 128, 64 },
  65         { NULL,                         0, NULL, 0, -1, -1 }
  66 };
  67
  68 static void
  69 mac_setup_by_id(Mac *mac, int which)
  70 {
  71         int evp_len;
  72         mac->type = macs[which].type;
  73         if (mac->type == SSH_EVP) {
  74                 mac->evp_md = (*macs[which].mdfunc)();
  75                 if ((evp_len = EVP_MD_size(mac->evp_md)) <= 0)
  76                         fatal("mac %s len %d", mac->name, evp_len);
  77                 mac->key_len = mac->mac_len = (u_int)evp_len;
  78         } else {
  79                 mac->mac_len = macs[which].len / 8;
  80                 mac->key_len = macs[which].key_len / 8;
  81                 mac->umac_ctx = NULL;
  82         }
  83         if (macs[which].truncatebits != 0)
  84                 mac->mac_len = macs[which].truncatebits / 8;
  85 }
  86
  87 int
  88 mac_setup(Mac *mac, char *name)
  89 {
  90         int i;
  91
  92         for (i = 0; macs[i].name; i++) {
  93                 if (strcmp(name, macs[i].name) == 0) {
  94                         if (mac != NULL)
  95                                 mac_setup_by_id(mac, i);
  96                         debug2("mac_setup: found %s", name);
  97                         return (0);
  98                 }
  99         }
 100         debug2("mac_setup: unknown %s", name);
 101         return (-1);
 102 }
 103
 104 int
 105 mac_init(Mac *mac)
 106 {
 107         if (mac->key == NULL)
 108                 fatal("mac_init: no key");
 109         switch (mac->type) {
 110         case SSH_EVP:
 111                 if (mac->evp_md == NULL)
 112                         return -1;
 113                 HMAC_Init(&mac->evp_ctx, mac->key, mac->key_len, mac->evp_md);
 114                 return 0;
 115         case SSH_UMAC:
 116                 mac->umac_ctx = umac_new(mac->key);
 117                 return 0;
 118         default:
 119                 return -1;
 120         }
 121 }
 122
 123 u_char *
 124 mac_compute(Mac *mac, u_int32_t seqno, u_char *data, int datalen)
 125 {
 126         static u_char m[EVP_MAX_MD_SIZE];
 127         u_char b[4], nonce[8];
 128
 129         if (mac->mac_len > sizeof(m))
 130                 fatal("mac_compute: mac too long %u %lu",
 131                     mac->mac_len, (u_long)sizeof(m));
 132
 133         switch (mac->type) {
 134         case SSH_EVP:
 135                 put_u32(b, seqno);
 136                 /* reset HMAC context */
 137                 HMAC_Init(&mac->evp_ctx, NULL, 0, NULL);
 138                 HMAC_Update(&mac->evp_ctx, b, sizeof(b));
 139                 HMAC_Update(&mac->evp_ctx, data, datalen);
 140                 HMAC_Final(&mac->evp_ctx, m, NULL);
 141                 break;
 142         case SSH_UMAC:
 143                 put_u64(nonce, seqno);
 144                 umac_update(mac->umac_ctx, data, datalen);
 145                 umac_final(mac->umac_ctx, m, nonce);
 146                 break;
 147         default:
 148                 fatal("mac_compute: unknown MAC type");
 149         }
 150         return (m);
 151 }
 152
 153 void
 154 mac_clear(Mac *mac)
 155 {
 156         if (mac->type == SSH_UMAC) {
 157                 if (mac->umac_ctx != NULL)
 158                         umac_delete(mac->umac_ctx);
 159         } else if (mac->evp_md != NULL)
 160                 HMAC_cleanup(&mac->evp_ctx);
 161         mac->evp_md = NULL;
 162         mac->umac_ctx = NULL;
 163 }
 164
 165 /* XXX copied from ciphers_valid */
 166 #define MAC_SEP ","
 167 int
 168 mac_valid(const char *names)
 169 {
 170         char *maclist, *cp, *p;
 171
 172         if (names == NULL || strcmp(names, "") == 0)
 173                 return (0);
 174         maclist = cp = xstrdup(names);
 175         for ((p = strsep(&cp, MAC_SEP)); p && *p != '\0';
 176             (p = strsep(&cp, MAC_SEP))) {
 177                 if (mac_setup(NULL, p) < 0) {
 178                         debug("bad mac %s [%s]", p, names);
 179                         xfree(maclist);
 180                         return (0);
 181                 } else {
 182                         debug3("mac ok: %s [%s]", p, names);
 183                 }
 184         }
 185         debug3("macs ok: [%s]", names);
 186         xfree(maclist);
 187         return (1);
 188 }