mac.c

   1 /* $OpenBSD: mac.c,v 1.11 2006/07/22 20:48:23 stevesk 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 <openssl/hmac.h>
  29
  30 #include <string.h>
  31
  32 #include "xmalloc.h"
  33 #include "log.h"
  34 #include "cipher.h"
  35 #include "kex.h"
  36 #include "mac.h"
  37 #include "misc.h"
  38
  39 struct {
  40         char            *name;
  41         const EVP_MD *  (*mdfunc)(void);
  42         int             truncatebits;   /* truncate digest if != 0 */
  43 } macs[] = {
  44         { "hmac-sha1",                  EVP_sha1, 0, },
  45         { "hmac-sha1-96",               EVP_sha1, 96 },
  46         { "hmac-md5",                   EVP_md5, 0 },
  47         { "hmac-md5-96",                EVP_md5, 96 },
  48         { "hmac-ripemd160",             EVP_ripemd160, 0 },
  49         { "hmac-ripemd160@openssh.com", EVP_ripemd160, 0 },
  50         { NULL,                         NULL, 0 }
  51 };
  52
  53 int
  54 mac_init(Mac *mac, char *name)
  55 {
  56         int i, evp_len;
  57
  58         for (i = 0; macs[i].name; i++) {
  59                 if (strcmp(name, macs[i].name) == 0) {
  60                         if (mac != NULL) {
  61                                 mac->md = (*macs[i].mdfunc)();
  62                                 if ((evp_len = EVP_MD_size(mac->md)) <= 0)
  63                                         fatal("mac %s len %d", name, evp_len);
  64                                 mac->key_len = mac->mac_len = (u_int)evp_len;
  65                                 if (macs[i].truncatebits != 0)
  66                                         mac->mac_len = macs[i].truncatebits/8;
  67                         }
  68                         debug2("mac_init: found %s", name);
  69                         return (0);
  70                 }
  71         }
  72         debug2("mac_init: unknown %s", name);
  73         return (-1);
  74 }
  75
  76 u_char *
  77 mac_compute(Mac *mac, u_int32_t seqno, u_char *data, int datalen)
  78 {
  79         HMAC_CTX c;
  80         static u_char m[EVP_MAX_MD_SIZE];
  81         u_char b[4];
  82
  83         if (mac->key == NULL)
  84                 fatal("mac_compute: no key");
  85         if (mac->mac_len > sizeof(m))
  86                 fatal("mac_compute: mac too long");
  87         HMAC_Init(&c, mac->key, mac->key_len, mac->md);
  88         put_u32(b, seqno);
  89         HMAC_Update(&c, b, sizeof(b));
  90         HMAC_Update(&c, data, datalen);
  91         HMAC_Final(&c, m, NULL);
  92         HMAC_cleanup(&c);
  93         return (m);
  94 }
  95
  96 /* XXX copied from ciphers_valid */
  97 #define MAC_SEP ","
  98 int
  99 mac_valid(const char *names)
 100 {
 101         char *maclist, *cp, *p;
 102
 103         if (names == NULL || strcmp(names, "") == 0)
 104                 return (0);
 105         maclist = cp = xstrdup(names);
 106         for ((p = strsep(&cp, MAC_SEP)); p && *p != '\0';
 107             (p = strsep(&cp, MAC_SEP))) {
 108                 if (mac_init(NULL, p) < 0) {
 109                         debug("bad mac %s [%s]", p, names);
 110                         xfree(maclist);
 111                         return (0);
 112                 } else {
 113                         debug3("mac ok: %s [%s]", p, names);
 114                 }
 115         }
 116         debug3("macs ok: [%s]", names);
 117         xfree(maclist);
 118         return (1);
 119 }