1 /* $OpenBSD: kexgexc.c,v 1.11 2006/11/06 21:25:28 markus Exp $ */
3 * Copyright (c) 2000 Niels Provos. All rights reserved.
4 * Copyright (c) 2001 Markus Friedl. All rights reserved.
6 * Redistribution and use in source and binary forms, with or without
7 * modification, are permitted provided that the following conditions
9 * 1. Redistributions of source code must retain the above copyright
10 * notice, this list of conditions and the following disclaimer.
11 * 2. Redistributions in binary form must reproduce the above copyright
12 * notice, this list of conditions and the following disclaimer in the
13 * documentation and/or other materials provided with the distribution.
15 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
16 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
17 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
18 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
19 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
20 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
21 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
22 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
23 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
24 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
29 #include <sys/types.h>
48 kexgex_client(Kex *kex)
50 BIGNUM *dh_server_pub = NULL, *shared_secret = NULL;
51 BIGNUM *p = NULL, *g = NULL;
53 u_char *kbuf, *hash, *signature = NULL, *server_host_key_blob = NULL;
54 u_int klen, slen, sbloblen, hashlen;
59 nbits = dh_estimate(kex->we_need * 8);
61 if (datafellows & SSH_OLD_DHGEX) {
63 packet_start(SSH2_MSG_KEX_DH_GEX_REQUEST_OLD);
64 packet_put_int(nbits);
68 debug("SSH2_MSG_KEX_DH_GEX_REQUEST_OLD(%u) sent", nbits);
73 packet_start(SSH2_MSG_KEX_DH_GEX_REQUEST);
75 packet_put_int(nbits);
78 debug("SSH2_MSG_KEX_DH_GEX_REQUEST(%u<%u<%u) sent",
82 fprintf(stderr, "\nmin = %d, nbits = %d, max = %d\n",
87 debug("expecting SSH2_MSG_KEX_DH_GEX_GROUP");
88 packet_read_expect(SSH2_MSG_KEX_DH_GEX_GROUP);
90 if ((p = BN_new()) == NULL)
92 packet_get_bignum2(p);
93 if ((g = BN_new()) == NULL)
95 packet_get_bignum2(g);
98 if (BN_num_bits(p) < min || BN_num_bits(p) > max)
99 fatal("DH_GEX group out of range: %d !< %d !< %d",
100 min, BN_num_bits(p), max);
102 dh = dh_new_group(g, p);
103 dh_gen_key(dh, kex->we_need * 8);
106 DHparams_print_fp(stderr, dh);
107 fprintf(stderr, "pub= ");
108 BN_print_fp(stderr, dh->pub_key);
109 fprintf(stderr, "\n");
112 debug("SSH2_MSG_KEX_DH_GEX_INIT sent");
113 /* generate and send 'e', client DH public key */
114 packet_start(SSH2_MSG_KEX_DH_GEX_INIT);
115 packet_put_bignum2(dh->pub_key);
118 debug("expecting SSH2_MSG_KEX_DH_GEX_REPLY");
119 packet_read_expect(SSH2_MSG_KEX_DH_GEX_REPLY);
122 server_host_key_blob = packet_get_string(&sbloblen);
123 server_host_key = key_from_blob(server_host_key_blob, sbloblen);
124 if (server_host_key == NULL)
125 fatal("cannot decode server_host_key_blob");
126 if (server_host_key->type != kex->hostkey_type)
127 fatal("type mismatch for decoded server_host_key_blob");
128 if (kex->verify_host_key == NULL)
129 fatal("cannot verify server_host_key");
130 if (kex->verify_host_key(server_host_key) == -1)
131 fatal("server_host_key verification failed");
133 /* DH parameter f, server public DH key */
134 if ((dh_server_pub = BN_new()) == NULL)
135 fatal("dh_server_pub == NULL");
136 packet_get_bignum2(dh_server_pub);
139 fprintf(stderr, "dh_server_pub= ");
140 BN_print_fp(stderr, dh_server_pub);
141 fprintf(stderr, "\n");
142 debug("bits %d", BN_num_bits(dh_server_pub));
146 signature = packet_get_string(&slen);
149 if (!dh_pub_is_valid(dh, dh_server_pub))
150 packet_disconnect("bad server public DH value");
153 kbuf = xmalloc(klen);
154 if ((kout = DH_compute_key(kbuf, dh_server_pub, dh)) < 0)
155 fatal("DH_compute_key: failed");
157 dump_digest("shared secret", kbuf, kout);
159 if ((shared_secret = BN_new()) == NULL)
160 fatal("kexgex_client: BN_new failed");
161 if (BN_bin2bn(kbuf, kout, shared_secret) == NULL)
162 fatal("kexgex_client: BN_bin2bn failed");
163 memset(kbuf, 0, klen);
166 if (datafellows & SSH_OLD_DHGEX)
169 /* calc and verify H */
172 kex->client_version_string,
173 kex->server_version_string,
174 buffer_ptr(&kex->my), buffer_len(&kex->my),
175 buffer_ptr(&kex->peer), buffer_len(&kex->peer),
176 server_host_key_blob, sbloblen,
185 /* have keys, free DH */
187 xfree(server_host_key_blob);
188 BN_clear_free(dh_server_pub);
190 if (key_verify(server_host_key, signature, slen, hash, hashlen) != 1)
191 fatal("key_verify failed for server_host_key");
192 key_free(server_host_key);
195 /* save session id */
196 if (kex->session_id == NULL) {
197 kex->session_id_len = hashlen;
198 kex->session_id = xmalloc(kex->session_id_len);
199 memcpy(kex->session_id, hash, kex->session_id_len);
201 kex_derive_keys(kex, hash, hashlen, shared_secret);
202 BN_clear_free(shared_secret);