blob: 0193183b954aa0307632e78b10f87b753748467b [file] [log] [blame]
Damien Miller8e7fb332003-02-24 12:03:03 +11001/*
2 * Copyright (c) 2000 Niels Provos. All rights reserved.
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"
Darren Tucker564f19e2003-12-09 19:18:07 +110027RCSID("$OpenBSD: kexgexc.c,v 1.2 2003/12/08 11:00:47 markus Exp $");
Damien Miller8e7fb332003-02-24 12:03:03 +110028
29#include "xmalloc.h"
30#include "key.h"
31#include "kex.h"
32#include "log.h"
33#include "packet.h"
34#include "dh.h"
35#include "ssh2.h"
36#include "compat.h"
37
38void
39kexgex_client(Kex *kex)
40{
41 BIGNUM *dh_server_pub = NULL, *shared_secret = NULL;
42 BIGNUM *p = NULL, *g = NULL;
43 Key *server_host_key;
44 u_char *kbuf, *hash, *signature = NULL, *server_host_key_blob = NULL;
45 u_int klen, kout, slen, sbloblen;
46 int min, max, nbits;
47 DH *dh;
48
49 nbits = dh_estimate(kex->we_need * 8);
50
51 if (datafellows & SSH_OLD_DHGEX) {
Damien Miller8e7fb332003-02-24 12:03:03 +110052 /* Old GEX request */
53 packet_start(SSH2_MSG_KEX_DH_GEX_REQUEST_OLD);
54 packet_put_int(nbits);
55 min = DH_GRP_MIN;
56 max = DH_GRP_MAX;
Damien Miller8e7fb332003-02-24 12:03:03 +110057
Darren Tucker564f19e2003-12-09 19:18:07 +110058 debug("SSH2_MSG_KEX_DH_GEX_REQUEST_OLD(%u) sent", nbits);
59 } else {
Damien Miller8e7fb332003-02-24 12:03:03 +110060 /* New GEX request */
61 min = DH_GRP_MIN;
62 max = DH_GRP_MAX;
63 packet_start(SSH2_MSG_KEX_DH_GEX_REQUEST);
64 packet_put_int(min);
65 packet_put_int(nbits);
66 packet_put_int(max);
Darren Tucker564f19e2003-12-09 19:18:07 +110067
68 debug("SSH2_MSG_KEX_DH_GEX_REQUEST(%u<%u<%u) sent",
69 min, nbits, max);
Damien Miller8e7fb332003-02-24 12:03:03 +110070 }
71#ifdef DEBUG_KEXDH
72 fprintf(stderr, "\nmin = %d, nbits = %d, max = %d\n",
73 min, nbits, max);
74#endif
75 packet_send();
76
77 debug("expecting SSH2_MSG_KEX_DH_GEX_GROUP");
78 packet_read_expect(SSH2_MSG_KEX_DH_GEX_GROUP);
79
80 if ((p = BN_new()) == NULL)
81 fatal("BN_new");
82 packet_get_bignum2(p);
83 if ((g = BN_new()) == NULL)
84 fatal("BN_new");
85 packet_get_bignum2(g);
86 packet_check_eom();
87
88 if (BN_num_bits(p) < min || BN_num_bits(p) > max)
89 fatal("DH_GEX group out of range: %d !< %d !< %d",
90 min, BN_num_bits(p), max);
91
92 dh = dh_new_group(g, p);
93 dh_gen_key(dh, kex->we_need * 8);
94
95#ifdef DEBUG_KEXDH
96 DHparams_print_fp(stderr, dh);
97 fprintf(stderr, "pub= ");
98 BN_print_fp(stderr, dh->pub_key);
99 fprintf(stderr, "\n");
100#endif
101
102 debug("SSH2_MSG_KEX_DH_GEX_INIT sent");
103 /* generate and send 'e', client DH public key */
104 packet_start(SSH2_MSG_KEX_DH_GEX_INIT);
105 packet_put_bignum2(dh->pub_key);
106 packet_send();
107
108 debug("expecting SSH2_MSG_KEX_DH_GEX_REPLY");
109 packet_read_expect(SSH2_MSG_KEX_DH_GEX_REPLY);
110
111 /* key, cert */
112 server_host_key_blob = packet_get_string(&sbloblen);
113 server_host_key = key_from_blob(server_host_key_blob, sbloblen);
114 if (server_host_key == NULL)
115 fatal("cannot decode server_host_key_blob");
116 if (server_host_key->type != kex->hostkey_type)
117 fatal("type mismatch for decoded server_host_key_blob");
118 if (kex->verify_host_key == NULL)
119 fatal("cannot verify server_host_key");
120 if (kex->verify_host_key(server_host_key) == -1)
121 fatal("server_host_key verification failed");
122
123 /* DH paramter f, server public DH key */
124 if ((dh_server_pub = BN_new()) == NULL)
125 fatal("dh_server_pub == NULL");
126 packet_get_bignum2(dh_server_pub);
127
128#ifdef DEBUG_KEXDH
129 fprintf(stderr, "dh_server_pub= ");
130 BN_print_fp(stderr, dh_server_pub);
131 fprintf(stderr, "\n");
132 debug("bits %d", BN_num_bits(dh_server_pub));
133#endif
134
135 /* signed H */
136 signature = packet_get_string(&slen);
137 packet_check_eom();
138
139 if (!dh_pub_is_valid(dh, dh_server_pub))
140 packet_disconnect("bad server public DH value");
141
142 klen = DH_size(dh);
143 kbuf = xmalloc(klen);
144 kout = DH_compute_key(kbuf, dh_server_pub, dh);
145#ifdef DEBUG_KEXDH
146 dump_digest("shared secret", kbuf, kout);
147#endif
148 if ((shared_secret = BN_new()) == NULL)
149 fatal("kexgex_client: BN_new failed");
150 BN_bin2bn(kbuf, kout, shared_secret);
151 memset(kbuf, 0, klen);
152 xfree(kbuf);
153
154 if (datafellows & SSH_OLD_DHGEX)
155 min = max = -1;
156
157 /* calc and verify H */
158 hash = kexgex_hash(
159 kex->client_version_string,
160 kex->server_version_string,
161 buffer_ptr(&kex->my), buffer_len(&kex->my),
162 buffer_ptr(&kex->peer), buffer_len(&kex->peer),
163 server_host_key_blob, sbloblen,
164 min, nbits, max,
165 dh->p, dh->g,
166 dh->pub_key,
167 dh_server_pub,
168 shared_secret
169 );
170 /* have keys, free DH */
171 DH_free(dh);
172 xfree(server_host_key_blob);
173 BN_clear_free(dh_server_pub);
174
175 if (key_verify(server_host_key, signature, slen, hash, 20) != 1)
176 fatal("key_verify failed for server_host_key");
177 key_free(server_host_key);
178 xfree(signature);
179
180 /* save session id */
181 if (kex->session_id == NULL) {
182 kex->session_id_len = 20;
183 kex->session_id = xmalloc(kex->session_id_len);
184 memcpy(kex->session_id, hash, kex->session_id_len);
185 }
186 kex_derive_keys(kex, hash, shared_secret);
187 BN_clear_free(shared_secret);
188
189 kex_finish(kex);
190}