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Damien Millerad6b14d2006-06-13 13:00:41 +10001/* $OpenBSD: kexdhc.c,v 1.6 2006/05/18 21:27:25 miod 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
28#include "xmalloc.h"
29#include "key.h"
30#include "kex.h"
31#include "log.h"
32#include "packet.h"
33#include "dh.h"
34#include "ssh2.h"
35
36void
37kexdh_client(Kex *kex)
38{
39 BIGNUM *dh_server_pub = NULL, *shared_secret = NULL;
40 DH *dh;
41 Key *server_host_key;
42 u_char *server_host_key_blob = NULL, *signature = NULL;
43 u_char *kbuf, *hash;
Damien Miller19bb3a52005-11-05 15:19:35 +110044 u_int klen, kout, slen, sbloblen, hashlen;
Damien Miller8e7fb332003-02-24 12:03:03 +110045
46 /* generate and send 'e', client DH public key */
Damien Millerf675fc42004-06-15 10:30:09 +100047 switch (kex->kex_type) {
48 case KEX_DH_GRP1_SHA1:
49 dh = dh_new_group1();
50 break;
51 case KEX_DH_GRP14_SHA1:
52 dh = dh_new_group14();
53 break;
54 default:
55 fatal("%s: Unexpected KEX type %d", __func__, kex->kex_type);
56 }
Damien Miller8e7fb332003-02-24 12:03:03 +110057 dh_gen_key(dh, kex->we_need * 8);
58 packet_start(SSH2_MSG_KEXDH_INIT);
59 packet_put_bignum2(dh->pub_key);
60 packet_send();
61
62 debug("sending SSH2_MSG_KEXDH_INIT");
63#ifdef DEBUG_KEXDH
64 DHparams_print_fp(stderr, dh);
65 fprintf(stderr, "pub= ");
66 BN_print_fp(stderr, dh->pub_key);
67 fprintf(stderr, "\n");
68#endif
69
70 debug("expecting SSH2_MSG_KEXDH_REPLY");
71 packet_read_expect(SSH2_MSG_KEXDH_REPLY);
72
73 /* key, cert */
74 server_host_key_blob = packet_get_string(&sbloblen);
75 server_host_key = key_from_blob(server_host_key_blob, sbloblen);
76 if (server_host_key == NULL)
77 fatal("cannot decode server_host_key_blob");
78 if (server_host_key->type != kex->hostkey_type)
79 fatal("type mismatch for decoded server_host_key_blob");
80 if (kex->verify_host_key == NULL)
81 fatal("cannot verify server_host_key");
82 if (kex->verify_host_key(server_host_key) == -1)
83 fatal("server_host_key verification failed");
84
Damien Millerad6b14d2006-06-13 13:00:41 +100085 /* DH parameter f, server public DH key */
Damien Miller8e7fb332003-02-24 12:03:03 +110086 if ((dh_server_pub = BN_new()) == NULL)
87 fatal("dh_server_pub == NULL");
88 packet_get_bignum2(dh_server_pub);
89
90#ifdef DEBUG_KEXDH
91 fprintf(stderr, "dh_server_pub= ");
92 BN_print_fp(stderr, dh_server_pub);
93 fprintf(stderr, "\n");
94 debug("bits %d", BN_num_bits(dh_server_pub));
95#endif
96
97 /* signed H */
98 signature = packet_get_string(&slen);
99 packet_check_eom();
100
101 if (!dh_pub_is_valid(dh, dh_server_pub))
102 packet_disconnect("bad server public DH value");
103
104 klen = DH_size(dh);
105 kbuf = xmalloc(klen);
106 kout = DH_compute_key(kbuf, dh_server_pub, dh);
107#ifdef DEBUG_KEXDH
108 dump_digest("shared secret", kbuf, kout);
109#endif
110 if ((shared_secret = BN_new()) == NULL)
111 fatal("kexdh_client: BN_new failed");
112 BN_bin2bn(kbuf, kout, shared_secret);
113 memset(kbuf, 0, klen);
114 xfree(kbuf);
115
116 /* calc and verify H */
Damien Miller19bb3a52005-11-05 15:19:35 +1100117 kex_dh_hash(
Damien Miller8e7fb332003-02-24 12:03:03 +1100118 kex->client_version_string,
119 kex->server_version_string,
120 buffer_ptr(&kex->my), buffer_len(&kex->my),
121 buffer_ptr(&kex->peer), buffer_len(&kex->peer),
122 server_host_key_blob, sbloblen,
123 dh->pub_key,
124 dh_server_pub,
Damien Miller19bb3a52005-11-05 15:19:35 +1100125 shared_secret,
126 &hash, &hashlen
Damien Miller8e7fb332003-02-24 12:03:03 +1100127 );
128 xfree(server_host_key_blob);
129 BN_clear_free(dh_server_pub);
130 DH_free(dh);
131
Damien Miller19bb3a52005-11-05 15:19:35 +1100132 if (key_verify(server_host_key, signature, slen, hash, hashlen) != 1)
Damien Miller8e7fb332003-02-24 12:03:03 +1100133 fatal("key_verify failed for server_host_key");
134 key_free(server_host_key);
135 xfree(signature);
136
137 /* save session id */
138 if (kex->session_id == NULL) {
Damien Miller19bb3a52005-11-05 15:19:35 +1100139 kex->session_id_len = hashlen;
Damien Miller8e7fb332003-02-24 12:03:03 +1100140 kex->session_id = xmalloc(kex->session_id_len);
141 memcpy(kex->session_id, hash, kex->session_id_len);
142 }
143
Damien Miller19bb3a52005-11-05 15:19:35 +1100144 kex_derive_keys(kex, hash, hashlen, shared_secret);
Damien Miller8e7fb332003-02-24 12:03:03 +1100145 BN_clear_free(shared_secret);
146 kex_finish(kex);
147}