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Damien Millera5103f42014-02-04 11:20:14 +11001/* $OpenBSD: kexdhc.c,v 1.15 2014/02/02 03:44:31 djm Exp $ */
Damien Miller8e7fb332003-02-24 12:03:03 +11002/*
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"
Damien Miller8e7fb332003-02-24 12:03:03 +110027
Damien Millerd7834352006-08-05 12:39:39 +100028#include <sys/types.h>
29
Damien Miller4499f4c2010-11-20 15:15:49 +110030#include <openssl/dh.h>
31
Damien Millerded319c2006-09-01 15:38:36 +100032#include <stdarg.h>
Damien Millera7a73ee2006-08-05 11:37:59 +100033#include <stdio.h>
Damien Millere3476ed2006-07-24 14:13:33 +100034#include <string.h>
Damien Millerd7834352006-08-05 12:39:39 +100035#include <signal.h>
Damien Millere3476ed2006-07-24 14:13:33 +100036
Damien Miller8e7fb332003-02-24 12:03:03 +110037#include "xmalloc.h"
Damien Millerd7834352006-08-05 12:39:39 +100038#include "buffer.h"
Damien Miller8e7fb332003-02-24 12:03:03 +110039#include "key.h"
Damien Millerd7834352006-08-05 12:39:39 +100040#include "cipher.h"
Damien Miller8e7fb332003-02-24 12:03:03 +110041#include "kex.h"
42#include "log.h"
43#include "packet.h"
44#include "dh.h"
45#include "ssh2.h"
46
47void
48kexdh_client(Kex *kex)
49{
50 BIGNUM *dh_server_pub = NULL, *shared_secret = NULL;
51 DH *dh;
52 Key *server_host_key;
53 u_char *server_host_key_blob = NULL, *signature = NULL;
54 u_char *kbuf, *hash;
Damien Miller570c2ab2006-11-05 05:32:02 +110055 u_int klen, slen, sbloblen, hashlen;
56 int kout;
Damien Miller8e7fb332003-02-24 12:03:03 +110057
58 /* generate and send 'e', client DH public key */
Damien Millerf675fc42004-06-15 10:30:09 +100059 switch (kex->kex_type) {
60 case KEX_DH_GRP1_SHA1:
61 dh = dh_new_group1();
62 break;
63 case KEX_DH_GRP14_SHA1:
64 dh = dh_new_group14();
65 break;
66 default:
67 fatal("%s: Unexpected KEX type %d", __func__, kex->kex_type);
68 }
Damien Miller8e7fb332003-02-24 12:03:03 +110069 dh_gen_key(dh, kex->we_need * 8);
70 packet_start(SSH2_MSG_KEXDH_INIT);
71 packet_put_bignum2(dh->pub_key);
72 packet_send();
73
74 debug("sending SSH2_MSG_KEXDH_INIT");
75#ifdef DEBUG_KEXDH
76 DHparams_print_fp(stderr, dh);
77 fprintf(stderr, "pub= ");
78 BN_print_fp(stderr, dh->pub_key);
79 fprintf(stderr, "\n");
80#endif
81
82 debug("expecting SSH2_MSG_KEXDH_REPLY");
83 packet_read_expect(SSH2_MSG_KEXDH_REPLY);
84
85 /* key, cert */
86 server_host_key_blob = packet_get_string(&sbloblen);
87 server_host_key = key_from_blob(server_host_key_blob, sbloblen);
88 if (server_host_key == NULL)
89 fatal("cannot decode server_host_key_blob");
90 if (server_host_key->type != kex->hostkey_type)
91 fatal("type mismatch for decoded server_host_key_blob");
92 if (kex->verify_host_key == NULL)
93 fatal("cannot verify server_host_key");
94 if (kex->verify_host_key(server_host_key) == -1)
95 fatal("server_host_key verification failed");
96
Damien Millerad6b14d2006-06-13 13:00:41 +100097 /* DH parameter f, server public DH key */
Damien Miller8e7fb332003-02-24 12:03:03 +110098 if ((dh_server_pub = BN_new()) == NULL)
99 fatal("dh_server_pub == NULL");
100 packet_get_bignum2(dh_server_pub);
101
102#ifdef DEBUG_KEXDH
103 fprintf(stderr, "dh_server_pub= ");
104 BN_print_fp(stderr, dh_server_pub);
105 fprintf(stderr, "\n");
106 debug("bits %d", BN_num_bits(dh_server_pub));
107#endif
108
109 /* signed H */
110 signature = packet_get_string(&slen);
111 packet_check_eom();
112
113 if (!dh_pub_is_valid(dh, dh_server_pub))
114 packet_disconnect("bad server public DH value");
115
116 klen = DH_size(dh);
117 kbuf = xmalloc(klen);
Damien Miller570c2ab2006-11-05 05:32:02 +1100118 if ((kout = DH_compute_key(kbuf, dh_server_pub, dh)) < 0)
119 fatal("DH_compute_key: failed");
Damien Miller8e7fb332003-02-24 12:03:03 +1100120#ifdef DEBUG_KEXDH
121 dump_digest("shared secret", kbuf, kout);
122#endif
123 if ((shared_secret = BN_new()) == NULL)
124 fatal("kexdh_client: BN_new failed");
Darren Tucker0bc85572006-11-07 23:14:41 +1100125 if (BN_bin2bn(kbuf, kout, shared_secret) == NULL)
126 fatal("kexdh_client: BN_bin2bn failed");
Damien Millera5103f42014-02-04 11:20:14 +1100127 explicit_bzero(kbuf, klen);
Darren Tuckera627d422013-06-02 07:31:17 +1000128 free(kbuf);
Damien Miller8e7fb332003-02-24 12:03:03 +1100129
130 /* calc and verify H */
Damien Miller19bb3a52005-11-05 15:19:35 +1100131 kex_dh_hash(
Damien Miller8e7fb332003-02-24 12:03:03 +1100132 kex->client_version_string,
133 kex->server_version_string,
134 buffer_ptr(&kex->my), buffer_len(&kex->my),
135 buffer_ptr(&kex->peer), buffer_len(&kex->peer),
136 server_host_key_blob, sbloblen,
137 dh->pub_key,
138 dh_server_pub,
Damien Miller19bb3a52005-11-05 15:19:35 +1100139 shared_secret,
140 &hash, &hashlen
Damien Miller8e7fb332003-02-24 12:03:03 +1100141 );
Darren Tuckera627d422013-06-02 07:31:17 +1000142 free(server_host_key_blob);
Damien Miller8e7fb332003-02-24 12:03:03 +1100143 BN_clear_free(dh_server_pub);
144 DH_free(dh);
145
Damien Miller19bb3a52005-11-05 15:19:35 +1100146 if (key_verify(server_host_key, signature, slen, hash, hashlen) != 1)
Damien Miller8e7fb332003-02-24 12:03:03 +1100147 fatal("key_verify failed for server_host_key");
148 key_free(server_host_key);
Darren Tuckera627d422013-06-02 07:31:17 +1000149 free(signature);
Damien Miller8e7fb332003-02-24 12:03:03 +1100150
151 /* save session id */
152 if (kex->session_id == NULL) {
Damien Miller19bb3a52005-11-05 15:19:35 +1100153 kex->session_id_len = hashlen;
Damien Miller8e7fb332003-02-24 12:03:03 +1100154 kex->session_id = xmalloc(kex->session_id_len);
155 memcpy(kex->session_id, hash, kex->session_id_len);
156 }
157
Damien Miller91b580e2014-01-12 19:21:22 +1100158 kex_derive_keys_bn(kex, hash, hashlen, shared_secret);
Damien Miller8e7fb332003-02-24 12:03:03 +1100159 BN_clear_free(shared_secret);
160 kex_finish(kex);
161}