blob: f14ac44ca04321eb4eb85efdcdb9c11833e92392 [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"
27RCSID("$OpenBSD: kexgexc.c,v 1.1 2003/02/16 17:09:57 markus Exp $");
28
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) {
52 debug("SSH2_MSG_KEX_DH_GEX_REQUEST_OLD sent");
53
54 /* Old GEX request */
55 packet_start(SSH2_MSG_KEX_DH_GEX_REQUEST_OLD);
56 packet_put_int(nbits);
57 min = DH_GRP_MIN;
58 max = DH_GRP_MAX;
59 } else {
60 debug("SSH2_MSG_KEX_DH_GEX_REQUEST sent");
61
62 /* New GEX request */
63 min = DH_GRP_MIN;
64 max = DH_GRP_MAX;
65 packet_start(SSH2_MSG_KEX_DH_GEX_REQUEST);
66 packet_put_int(min);
67 packet_put_int(nbits);
68 packet_put_int(max);
69 }
70#ifdef DEBUG_KEXDH
71 fprintf(stderr, "\nmin = %d, nbits = %d, max = %d\n",
72 min, nbits, max);
73#endif
74 packet_send();
75
76 debug("expecting SSH2_MSG_KEX_DH_GEX_GROUP");
77 packet_read_expect(SSH2_MSG_KEX_DH_GEX_GROUP);
78
79 if ((p = BN_new()) == NULL)
80 fatal("BN_new");
81 packet_get_bignum2(p);
82 if ((g = BN_new()) == NULL)
83 fatal("BN_new");
84 packet_get_bignum2(g);
85 packet_check_eom();
86
87 if (BN_num_bits(p) < min || BN_num_bits(p) > max)
88 fatal("DH_GEX group out of range: %d !< %d !< %d",
89 min, BN_num_bits(p), max);
90
91 dh = dh_new_group(g, p);
92 dh_gen_key(dh, kex->we_need * 8);
93
94#ifdef DEBUG_KEXDH
95 DHparams_print_fp(stderr, dh);
96 fprintf(stderr, "pub= ");
97 BN_print_fp(stderr, dh->pub_key);
98 fprintf(stderr, "\n");
99#endif
100
101 debug("SSH2_MSG_KEX_DH_GEX_INIT sent");
102 /* generate and send 'e', client DH public key */
103 packet_start(SSH2_MSG_KEX_DH_GEX_INIT);
104 packet_put_bignum2(dh->pub_key);
105 packet_send();
106
107 debug("expecting SSH2_MSG_KEX_DH_GEX_REPLY");
108 packet_read_expect(SSH2_MSG_KEX_DH_GEX_REPLY);
109
110 /* key, cert */
111 server_host_key_blob = packet_get_string(&sbloblen);
112 server_host_key = key_from_blob(server_host_key_blob, sbloblen);
113 if (server_host_key == NULL)
114 fatal("cannot decode server_host_key_blob");
115 if (server_host_key->type != kex->hostkey_type)
116 fatal("type mismatch for decoded server_host_key_blob");
117 if (kex->verify_host_key == NULL)
118 fatal("cannot verify server_host_key");
119 if (kex->verify_host_key(server_host_key) == -1)
120 fatal("server_host_key verification failed");
121
122 /* DH paramter f, server public DH key */
123 if ((dh_server_pub = BN_new()) == NULL)
124 fatal("dh_server_pub == NULL");
125 packet_get_bignum2(dh_server_pub);
126
127#ifdef DEBUG_KEXDH
128 fprintf(stderr, "dh_server_pub= ");
129 BN_print_fp(stderr, dh_server_pub);
130 fprintf(stderr, "\n");
131 debug("bits %d", BN_num_bits(dh_server_pub));
132#endif
133
134 /* signed H */
135 signature = packet_get_string(&slen);
136 packet_check_eom();
137
138 if (!dh_pub_is_valid(dh, dh_server_pub))
139 packet_disconnect("bad server public DH value");
140
141 klen = DH_size(dh);
142 kbuf = xmalloc(klen);
143 kout = DH_compute_key(kbuf, dh_server_pub, dh);
144#ifdef DEBUG_KEXDH
145 dump_digest("shared secret", kbuf, kout);
146#endif
147 if ((shared_secret = BN_new()) == NULL)
148 fatal("kexgex_client: BN_new failed");
149 BN_bin2bn(kbuf, kout, shared_secret);
150 memset(kbuf, 0, klen);
151 xfree(kbuf);
152
153 if (datafellows & SSH_OLD_DHGEX)
154 min = max = -1;
155
156 /* calc and verify H */
157 hash = kexgex_hash(
158 kex->client_version_string,
159 kex->server_version_string,
160 buffer_ptr(&kex->my), buffer_len(&kex->my),
161 buffer_ptr(&kex->peer), buffer_len(&kex->peer),
162 server_host_key_blob, sbloblen,
163 min, nbits, max,
164 dh->p, dh->g,
165 dh->pub_key,
166 dh_server_pub,
167 shared_secret
168 );
169 /* have keys, free DH */
170 DH_free(dh);
171 xfree(server_host_key_blob);
172 BN_clear_free(dh_server_pub);
173
174 if (key_verify(server_host_key, signature, slen, hash, 20) != 1)
175 fatal("key_verify failed for server_host_key");
176 key_free(server_host_key);
177 xfree(signature);
178
179 /* save session id */
180 if (kex->session_id == NULL) {
181 kex->session_id_len = 20;
182 kex->session_id = xmalloc(kex->session_id_len);
183 memcpy(kex->session_id, hash, kex->session_id_len);
184 }
185 kex_derive_keys(kex, hash, shared_secret);
186 BN_clear_free(shared_secret);
187
188 kex_finish(kex);
189}