mac.c

   1 /*
   2  * Copyright (c) 2001 Markus Friedl.  All rights reserved.
   3  *
   4  * Redistribution and use in source and binary forms, with or without
   5  * modification, are permitted provided that the following conditions
   6  * are met:
   7  * 1. Redistributions of source code must retain the above copyright
   8  *    notice, this list of conditions and the following disclaimer.
   9  * 2. Redistributions in binary form must reproduce the above copyright
  10  *    notice, this list of conditions and the following disclaimer in the
  11  *    documentation and/or other materials provided with the distribution.
  12  *
  13  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  14  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  15  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  16  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  17  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  18  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  19  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  20  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  21  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  22  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  23  */
  24
  25 #include "includes.h"
  26 RCSID("$OpenBSD: mac.c,v 1.6 2003/09/18 13:02:21 miod Exp $");
  27
  28 #include <openssl/hmac.h>
  29
  30 #include "xmalloc.h"
  31 #include "getput.h"
  32 #include "log.h"
  33 #include "cipher.h"
  34 #include "kex.h"
  35 #include "mac.h"
  36
  37 struct {
  38         char            *name;
  39         const EVP_MD *  (*mdfunc)(void);
  40         int             truncatebits;   /* truncate digest if != 0 */
  41 } macs[] = {
  42         { "hmac-sha1",                  EVP_sha1, 0, },
  43         { "hmac-sha1-96",               EVP_sha1, 96 },
  44         { "hmac-md5",                   EVP_md5, 0 },
  45         { "hmac-md5-96",                EVP_md5, 96 },
  46         { "hmac-ripemd160",             EVP_ripemd160, 0 },
  47         { "hmac-ripemd160@openssh.com", EVP_ripemd160, 0 },
  48         { NULL,                         NULL, 0 }
  49 };
  50
  51 int
  52 mac_init(Mac *mac, char *name)
  53 {
  54         int i;
  55         for (i = 0; macs[i].name; i++) {
  56                 if (strcmp(name, macs[i].name) == 0) {
  57                         if (mac != NULL) {
  58                                 mac->md = (*macs[i].mdfunc)();
  59                                 mac->key_len = mac->mac_len = EVP_MD_size(mac->md);
  60                                 if (macs[i].truncatebits != 0)
  61                                         mac->mac_len = macs[i].truncatebits/8;
  62                         }
  63                         debug2("mac_init: found %s", name);
  64                         return (0);
  65                 }
  66         }
  67         debug2("mac_init: unknown %s", name);
  68         return (-1);
  69 }
  70
  71 u_char *
  72 mac_compute(Mac *mac, u_int32_t seqno, u_char *data, int datalen)
  73 {
  74         HMAC_CTX c;
  75         static u_char m[EVP_MAX_MD_SIZE];
  76         u_char b[4];
  77
  78         if (mac->key == NULL)
  79                 fatal("mac_compute: no key");
  80         if ((u_int)mac->mac_len > sizeof(m))
  81                 fatal("mac_compute: mac too long");
  82         HMAC_Init(&c, mac->key, mac->key_len, mac->md);
  83         PUT_32BIT(b, seqno);
  84         HMAC_Update(&c, b, sizeof(b));
  85         HMAC_Update(&c, data, datalen);
  86         HMAC_Final(&c, m, NULL);
  87         HMAC_cleanup(&c);
  88         return (m);
  89 }
  90
  91 /* XXX copied from ciphers_valid */
  92 #define MAC_SEP ","
  93 int
  94 mac_valid(const char *names)
  95 {
  96         char *maclist, *cp, *p;
  97
  98         if (names == NULL || strcmp(names, "") == 0)
  99                 return (0);
 100         maclist = cp = xstrdup(names);
 101         for ((p = strsep(&cp, MAC_SEP)); p && *p != '\0';
 102             (p = strsep(&cp, MAC_SEP))) {
 103                 if (mac_init(NULL, p) < 0) {
 104                         debug("bad mac %s [%s]", p, names);
 105                         xfree(maclist);
 106                         return (0);
 107                 } else {
 108                         debug3("mac ok: %s [%s]", p, names);
 109                 }
 110         }
 111         debug3("macs ok: [%s]", names);
 112         xfree(maclist);
 113         return (1);
 114 }