crypto/openssh/kexdhs.c

   1 /* $OpenBSD: kexdhs.c,v 1.14 2013/07/19 07:37:48 markus 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 <stdarg.h>
  31 #include <string.h>
  32 #include <signal.h>
  33
  34 #include <openssl/dh.h>
  35
  36 #include "xmalloc.h"
  37 #include "buffer.h"
  38 #include "key.h"
  39 #include "cipher.h"
  40 #include "kex.h"
  41 #include "log.h"
  42 #include "packet.h"
  43 #include "dh.h"
  44 #include "ssh2.h"
  45 #ifdef GSSAPI
  46 #include "ssh-gss.h"
  47 #endif
  48 #include "monitor_wrap.h"
  49
  50 void
  51 kexdh_server(Kex *kex)
  52 {
  53         BIGNUM *shared_secret = NULL, *dh_client_pub = NULL;
  54         DH *dh;
  55         Key *server_host_public, *server_host_private;
  56         u_char *kbuf, *hash, *signature = NULL, *server_host_key_blob = NULL;
  57         u_int sbloblen, klen, hashlen, slen;
  58         int kout;
  59
  60         /* generate server DH public key */
  61         switch (kex->kex_type) {
  62         case KEX_DH_GRP1_SHA1:
  63                 dh = dh_new_group1();
  64                 break;
  65         case KEX_DH_GRP14_SHA1:
  66                 dh = dh_new_group14();
  67                 break;
  68         default:
  69                 fatal("%s: Unexpected KEX type %d", __func__, kex->kex_type);
  70         }
  71         dh_gen_key(dh, kex->we_need * 8);
  72
  73         debug("expecting SSH2_MSG_KEXDH_INIT");
  74         packet_read_expect(SSH2_MSG_KEXDH_INIT);
  75
  76         if (kex->load_host_public_key == NULL ||
  77             kex->load_host_private_key == NULL)
  78                 fatal("Cannot load hostkey");
  79         server_host_public = kex->load_host_public_key(kex->hostkey_type);
  80         if (server_host_public == NULL)
  81                 fatal("Unsupported hostkey type %d", kex->hostkey_type);
  82         server_host_private = kex->load_host_private_key(kex->hostkey_type);
  83
  84         /* key, cert */
  85         if ((dh_client_pub = BN_new()) == NULL)
  86                 fatal("dh_client_pub == NULL");
  87         packet_get_bignum2(dh_client_pub);
  88         packet_check_eom();
  89
  90 #ifdef DEBUG_KEXDH
  91         fprintf(stderr, "dh_client_pub= ");
  92         BN_print_fp(stderr, dh_client_pub);
  93         fprintf(stderr, "\n");
  94         debug("bits %d", BN_num_bits(dh_client_pub));
  95 #endif
  96
  97 #ifdef DEBUG_KEXDH
  98         DHparams_print_fp(stderr, dh);
  99         fprintf(stderr, "pub= ");
 100         BN_print_fp(stderr, dh->pub_key);
 101         fprintf(stderr, "\n");
 102 #endif
 103         if (!dh_pub_is_valid(dh, dh_client_pub))
 104                 packet_disconnect("bad client public DH value");
 105
 106         klen = DH_size(dh);
 107         kbuf = xmalloc(klen);
 108         if ((kout = DH_compute_key(kbuf, dh_client_pub, dh)) < 0)
 109                 fatal("DH_compute_key: failed");
 110 #ifdef DEBUG_KEXDH
 111         dump_digest("shared secret", kbuf, kout);
 112 #endif
 113         if ((shared_secret = BN_new()) == NULL)
 114                 fatal("kexdh_server: BN_new failed");
 115         if (BN_bin2bn(kbuf, kout, shared_secret) == NULL)
 116                 fatal("kexdh_server: BN_bin2bn failed");
 117         memset(kbuf, 0, klen);
 118         free(kbuf);
 119
 120         key_to_blob(server_host_public, &server_host_key_blob, &sbloblen);
 121
 122         /* calc H */
 123         kex_dh_hash(
 124             kex->client_version_string,
 125             kex->server_version_string,
 126             buffer_ptr(&kex->peer), buffer_len(&kex->peer),
 127             buffer_ptr(&kex->my), buffer_len(&kex->my),
 128             server_host_key_blob, sbloblen,
 129             dh_client_pub,
 130             dh->pub_key,
 131             shared_secret,
 132             &hash, &hashlen
 133         );
 134         BN_clear_free(dh_client_pub);
 135
 136         /* save session id := H */
 137         if (kex->session_id == NULL) {
 138                 kex->session_id_len = hashlen;
 139                 kex->session_id = xmalloc(kex->session_id_len);
 140                 memcpy(kex->session_id, hash, kex->session_id_len);
 141         }
 142
 143         /* sign H */
 144         kex->sign(server_host_private, server_host_public, &signature, &slen,
 145             hash, hashlen);
 146
 147         /* destroy_sensitive_data(); */
 148
 149         /* send server hostkey, DH pubkey 'f' and singed H */
 150         packet_start(SSH2_MSG_KEXDH_REPLY);
 151         packet_put_string(server_host_key_blob, sbloblen);
 152         packet_put_bignum2(dh->pub_key);        /* f */
 153         packet_put_string(signature, slen);
 154         packet_send();
 155
 156         free(signature);
 157         free(server_host_key_blob);
 158         /* have keys, free DH */
 159         DH_free(dh);
 160
 161         kex_derive_keys(kex, hash, hashlen, shared_secret);
 162         BN_clear_free(shared_secret);
 163         kex_finish(kex);
 164 }