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: kexdh.c,v 1.18 2002/03/18 17:50:31 provos Exp $");
  27 
  28 #pragma ident   "%Z%%M% %I%     %E% SMI"
  29 
  30 #include <openssl/crypto.h>
  31 #include <openssl/bn.h>
  32 
  33 #include "xmalloc.h"
  34 #include "buffer.h"
  35 #include "bufaux.h"
  36 #include "key.h"
  37 #include "kex.h"
  38 #include "log.h"
  39 #include "packet.h"
  40 #include "dh.h"
  41 #include "ssh2.h"
  42 
  43 u_char *
  44 kex_dh_hash(
  45     char *client_version_string,
  46     char *server_version_string,
  47     char *ckexinit, int ckexinitlen,
  48     char *skexinit, int skexinitlen,
  49     u_char *serverhostkeyblob, int sbloblen,
  50     BIGNUM *client_dh_pub,
  51     BIGNUM *server_dh_pub,
  52     BIGNUM *shared_secret)
  53 {
  54         Buffer b;
  55         static u_char digest[EVP_MAX_MD_SIZE];
  56         const EVP_MD *evp_md = EVP_sha1();
  57         EVP_MD_CTX md;
  58 
  59         buffer_init(&b);
  60         buffer_put_cstring(&b, client_version_string);
  61         buffer_put_cstring(&b, server_version_string);
  62 
  63         /* kexinit messages: fake header: len+SSH2_MSG_KEXINIT */
  64         buffer_put_int(&b, ckexinitlen+1);
  65         buffer_put_char(&b, SSH2_MSG_KEXINIT);
  66         buffer_append(&b, ckexinit, ckexinitlen);
  67         buffer_put_int(&b, skexinitlen+1);
  68         buffer_put_char(&b, SSH2_MSG_KEXINIT);
  69         buffer_append(&b, skexinit, skexinitlen);
  70 
  71         buffer_put_string(&b, serverhostkeyblob, sbloblen);
  72         buffer_put_bignum2(&b, client_dh_pub);
  73         buffer_put_bignum2(&b, server_dh_pub);
  74         buffer_put_bignum2(&b, shared_secret);
  75 
  76 #ifdef DEBUG_KEX
  77         buffer_dump(&b);
  78 #endif
  79         EVP_DigestInit(&md, evp_md);
  80         EVP_DigestUpdate(&md, buffer_ptr(&b), buffer_len(&b));
  81         EVP_DigestFinal(&md, digest, NULL);
  82 
  83         buffer_free(&b);
  84 
  85 #ifdef DEBUG_KEX
  86         dump_digest("hash", digest, EVP_MD_size(evp_md));
  87 #endif
  88         return digest;
  89 }