blob: f48bd46785b4fe1d24cfa02e10efab5b4bfde87c [file] [log] [blame]
Damien Miller8e7fb332003-02-24 12:03:03 +11001/*
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"
Damien Millerf675fc42004-06-15 10:30:09 +100026RCSID("$OpenBSD: kexdhc.c,v 1.2 2004/06/13 12:53:24 djm Exp $");
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;
44 u_int klen, kout, slen, sbloblen;
45
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
85 /* DH paramter f, server public DH key */
86 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 */
117 hash = kex_dh_hash(
118 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,
125 shared_secret
126 );
127 xfree(server_host_key_blob);
128 BN_clear_free(dh_server_pub);
129 DH_free(dh);
130
131 if (key_verify(server_host_key, signature, slen, hash, 20) != 1)
132 fatal("key_verify failed for server_host_key");
133 key_free(server_host_key);
134 xfree(signature);
135
136 /* save session id */
137 if (kex->session_id == NULL) {
138 kex->session_id_len = 20;
139 kex->session_id = xmalloc(kex->session_id_len);
140 memcpy(kex->session_id, hash, kex->session_id_len);
141 }
142
143 kex_derive_keys(kex, hash, shared_secret);
144 BN_clear_free(shared_secret);
145 kex_finish(kex);
146}