1*0Sstevel@tonic-gate /*
2*0Sstevel@tonic-gate * Copyright (c) 2000 Niels Provos. All rights reserved.
3*0Sstevel@tonic-gate * Copyright (c) 2001 Markus Friedl. All rights reserved.
4*0Sstevel@tonic-gate *
5*0Sstevel@tonic-gate * Redistribution and use in source and binary forms, with or without
6*0Sstevel@tonic-gate * modification, are permitted provided that the following conditions
7*0Sstevel@tonic-gate * are met:
8*0Sstevel@tonic-gate * 1. Redistributions of source code must retain the above copyright
9*0Sstevel@tonic-gate * notice, this list of conditions and the following disclaimer.
10*0Sstevel@tonic-gate * 2. Redistributions in binary form must reproduce the above copyright
11*0Sstevel@tonic-gate * notice, this list of conditions and the following disclaimer in the
12*0Sstevel@tonic-gate * documentation and/or other materials provided with the distribution.
13*0Sstevel@tonic-gate *
14*0Sstevel@tonic-gate * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
15*0Sstevel@tonic-gate * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
16*0Sstevel@tonic-gate * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
17*0Sstevel@tonic-gate * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
18*0Sstevel@tonic-gate * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
19*0Sstevel@tonic-gate * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
20*0Sstevel@tonic-gate * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
21*0Sstevel@tonic-gate * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
22*0Sstevel@tonic-gate * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
23*0Sstevel@tonic-gate * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
24*0Sstevel@tonic-gate */
25*0Sstevel@tonic-gate
26*0Sstevel@tonic-gate #include "includes.h"
27*0Sstevel@tonic-gate RCSID("$OpenBSD: kexgex.c,v 1.22 2002/03/24 17:27:03 stevesk Exp $");
28*0Sstevel@tonic-gate
29*0Sstevel@tonic-gate #pragma ident "%Z%%M% %I% %E% SMI"
30*0Sstevel@tonic-gate
31*0Sstevel@tonic-gate #include <openssl/bn.h>
32*0Sstevel@tonic-gate
33*0Sstevel@tonic-gate #include "xmalloc.h"
34*0Sstevel@tonic-gate #include "buffer.h"
35*0Sstevel@tonic-gate #include "bufaux.h"
36*0Sstevel@tonic-gate #include "key.h"
37*0Sstevel@tonic-gate #include "kex.h"
38*0Sstevel@tonic-gate #include "log.h"
39*0Sstevel@tonic-gate #include "packet.h"
40*0Sstevel@tonic-gate #include "dh.h"
41*0Sstevel@tonic-gate #include "ssh2.h"
42*0Sstevel@tonic-gate #include "compat.h"
43*0Sstevel@tonic-gate
44*0Sstevel@tonic-gate void
kexgex_client(Kex * kex)45*0Sstevel@tonic-gate kexgex_client(Kex *kex)
46*0Sstevel@tonic-gate {
47*0Sstevel@tonic-gate BIGNUM *dh_server_pub = NULL, *shared_secret = NULL;
48*0Sstevel@tonic-gate BIGNUM *p = NULL, *g = NULL;
49*0Sstevel@tonic-gate Key *server_host_key;
50*0Sstevel@tonic-gate u_char *kbuf, *hash, *signature = NULL, *server_host_key_blob = NULL;
51*0Sstevel@tonic-gate u_int klen, kout, slen, sbloblen;
52*0Sstevel@tonic-gate int min, max, nbits;
53*0Sstevel@tonic-gate DH *dh;
54*0Sstevel@tonic-gate
55*0Sstevel@tonic-gate nbits = dh_estimate(kex->we_need * 8);
56*0Sstevel@tonic-gate
57*0Sstevel@tonic-gate if (datafellows & SSH_OLD_DHGEX) {
58*0Sstevel@tonic-gate debug("SSH2_MSG_KEX_DH_GEX_REQUEST_OLD sent");
59*0Sstevel@tonic-gate
60*0Sstevel@tonic-gate /* Old GEX request */
61*0Sstevel@tonic-gate packet_start(SSH2_MSG_KEX_DH_GEX_REQUEST_OLD);
62*0Sstevel@tonic-gate packet_put_int(nbits);
63*0Sstevel@tonic-gate min = DH_GRP_MIN;
64*0Sstevel@tonic-gate max = DH_GRP_MAX;
65*0Sstevel@tonic-gate } else {
66*0Sstevel@tonic-gate debug("SSH2_MSG_KEX_DH_GEX_REQUEST sent");
67*0Sstevel@tonic-gate
68*0Sstevel@tonic-gate /* New GEX request */
69*0Sstevel@tonic-gate min = DH_GRP_MIN;
70*0Sstevel@tonic-gate max = DH_GRP_MAX;
71*0Sstevel@tonic-gate packet_start(SSH2_MSG_KEX_DH_GEX_REQUEST);
72*0Sstevel@tonic-gate packet_put_int(min);
73*0Sstevel@tonic-gate packet_put_int(nbits);
74*0Sstevel@tonic-gate packet_put_int(max);
75*0Sstevel@tonic-gate }
76*0Sstevel@tonic-gate #ifdef DEBUG_KEXDH
77*0Sstevel@tonic-gate fprintf(stderr, "\nmin = %d, nbits = %d, max = %d\n",
78*0Sstevel@tonic-gate min, nbits, max);
79*0Sstevel@tonic-gate #endif
80*0Sstevel@tonic-gate packet_send();
81*0Sstevel@tonic-gate
82*0Sstevel@tonic-gate debug("expecting SSH2_MSG_KEX_DH_GEX_GROUP");
83*0Sstevel@tonic-gate packet_read_expect(SSH2_MSG_KEX_DH_GEX_GROUP);
84*0Sstevel@tonic-gate
85*0Sstevel@tonic-gate if ((p = BN_new()) == NULL)
86*0Sstevel@tonic-gate fatal("BN_new");
87*0Sstevel@tonic-gate packet_get_bignum2(p);
88*0Sstevel@tonic-gate if ((g = BN_new()) == NULL)
89*0Sstevel@tonic-gate fatal("BN_new");
90*0Sstevel@tonic-gate packet_get_bignum2(g);
91*0Sstevel@tonic-gate packet_check_eom();
92*0Sstevel@tonic-gate
93*0Sstevel@tonic-gate if (BN_num_bits(p) < min || BN_num_bits(p) > max)
94*0Sstevel@tonic-gate fatal("DH_GEX group out of range: %d !< %d !< %d",
95*0Sstevel@tonic-gate min, BN_num_bits(p), max);
96*0Sstevel@tonic-gate
97*0Sstevel@tonic-gate dh = dh_new_group(g, p);
98*0Sstevel@tonic-gate dh_gen_key(dh, kex->we_need * 8);
99*0Sstevel@tonic-gate
100*0Sstevel@tonic-gate #ifdef DEBUG_KEXDH
101*0Sstevel@tonic-gate DHparams_print_fp(stderr, dh);
102*0Sstevel@tonic-gate fprintf(stderr, "pub= ");
103*0Sstevel@tonic-gate BN_print_fp(stderr, dh->pub_key);
104*0Sstevel@tonic-gate fprintf(stderr, "\n");
105*0Sstevel@tonic-gate #endif
106*0Sstevel@tonic-gate
107*0Sstevel@tonic-gate debug("SSH2_MSG_KEX_DH_GEX_INIT sent");
108*0Sstevel@tonic-gate /* generate and send 'e', client DH public key */
109*0Sstevel@tonic-gate packet_start(SSH2_MSG_KEX_DH_GEX_INIT);
110*0Sstevel@tonic-gate packet_put_bignum2(dh->pub_key);
111*0Sstevel@tonic-gate packet_send();
112*0Sstevel@tonic-gate
113*0Sstevel@tonic-gate debug("expecting SSH2_MSG_KEX_DH_GEX_REPLY");
114*0Sstevel@tonic-gate packet_read_expect(SSH2_MSG_KEX_DH_GEX_REPLY);
115*0Sstevel@tonic-gate
116*0Sstevel@tonic-gate /* key, cert */
117*0Sstevel@tonic-gate server_host_key_blob = packet_get_string(&sbloblen);
118*0Sstevel@tonic-gate server_host_key = key_from_blob(server_host_key_blob, sbloblen);
119*0Sstevel@tonic-gate if (server_host_key == NULL)
120*0Sstevel@tonic-gate fatal("cannot decode server_host_key_blob");
121*0Sstevel@tonic-gate if (server_host_key->type != kex->hostkey_type)
122*0Sstevel@tonic-gate fatal("type mismatch for decoded server_host_key_blob");
123*0Sstevel@tonic-gate if (kex->verify_host_key == NULL)
124*0Sstevel@tonic-gate fatal("cannot verify server_host_key");
125*0Sstevel@tonic-gate if (kex->verify_host_key(server_host_key) == -1)
126*0Sstevel@tonic-gate fatal("server_host_key verification failed");
127*0Sstevel@tonic-gate
128*0Sstevel@tonic-gate /* DH paramter f, server public DH key */
129*0Sstevel@tonic-gate if ((dh_server_pub = BN_new()) == NULL)
130*0Sstevel@tonic-gate fatal("dh_server_pub == NULL");
131*0Sstevel@tonic-gate packet_get_bignum2(dh_server_pub);
132*0Sstevel@tonic-gate
133*0Sstevel@tonic-gate #ifdef DEBUG_KEXDH
134*0Sstevel@tonic-gate fprintf(stderr, "dh_server_pub= ");
135*0Sstevel@tonic-gate BN_print_fp(stderr, dh_server_pub);
136*0Sstevel@tonic-gate fprintf(stderr, "\n");
137*0Sstevel@tonic-gate debug("bits %d", BN_num_bits(dh_server_pub));
138*0Sstevel@tonic-gate #endif
139*0Sstevel@tonic-gate
140*0Sstevel@tonic-gate /* signed H */
141*0Sstevel@tonic-gate signature = packet_get_string(&slen);
142*0Sstevel@tonic-gate packet_check_eom();
143*0Sstevel@tonic-gate
144*0Sstevel@tonic-gate if (!dh_pub_is_valid(dh, dh_server_pub))
145*0Sstevel@tonic-gate packet_disconnect("bad server public DH value");
146*0Sstevel@tonic-gate
147*0Sstevel@tonic-gate klen = DH_size(dh);
148*0Sstevel@tonic-gate kbuf = xmalloc(klen);
149*0Sstevel@tonic-gate kout = DH_compute_key(kbuf, dh_server_pub, dh);
150*0Sstevel@tonic-gate #ifdef DEBUG_KEXDH
151*0Sstevel@tonic-gate dump_digest("shared secret", kbuf, kout);
152*0Sstevel@tonic-gate #endif
153*0Sstevel@tonic-gate if ((shared_secret = BN_new()) == NULL)
154*0Sstevel@tonic-gate fatal("kexgex_client: BN_new failed");
155*0Sstevel@tonic-gate BN_bin2bn(kbuf, kout, shared_secret);
156*0Sstevel@tonic-gate memset(kbuf, 0, klen);
157*0Sstevel@tonic-gate xfree(kbuf);
158*0Sstevel@tonic-gate
159*0Sstevel@tonic-gate if (datafellows & SSH_OLD_DHGEX)
160*0Sstevel@tonic-gate min = max = -1;
161*0Sstevel@tonic-gate
162*0Sstevel@tonic-gate /* calc and verify H */
163*0Sstevel@tonic-gate hash = kexgex_hash(
164*0Sstevel@tonic-gate kex->client_version_string,
165*0Sstevel@tonic-gate kex->server_version_string,
166*0Sstevel@tonic-gate buffer_ptr(&kex->my), buffer_len(&kex->my),
167*0Sstevel@tonic-gate buffer_ptr(&kex->peer), buffer_len(&kex->peer),
168*0Sstevel@tonic-gate server_host_key_blob, sbloblen,
169*0Sstevel@tonic-gate min, nbits, max,
170*0Sstevel@tonic-gate dh->p, dh->g,
171*0Sstevel@tonic-gate dh->pub_key,
172*0Sstevel@tonic-gate dh_server_pub,
173*0Sstevel@tonic-gate shared_secret
174*0Sstevel@tonic-gate );
175*0Sstevel@tonic-gate /* have keys, free DH */
176*0Sstevel@tonic-gate DH_free(dh);
177*0Sstevel@tonic-gate xfree(server_host_key_blob);
178*0Sstevel@tonic-gate BN_clear_free(dh_server_pub);
179*0Sstevel@tonic-gate
180*0Sstevel@tonic-gate if (key_verify(server_host_key, signature, slen, hash, 20) != 1)
181*0Sstevel@tonic-gate fatal("key_verify failed for server_host_key");
182*0Sstevel@tonic-gate key_free(server_host_key);
183*0Sstevel@tonic-gate xfree(signature);
184*0Sstevel@tonic-gate
185*0Sstevel@tonic-gate /* save session id */
186*0Sstevel@tonic-gate if (kex->session_id == NULL) {
187*0Sstevel@tonic-gate kex->session_id_len = 20;
188*0Sstevel@tonic-gate kex->session_id = xmalloc(kex->session_id_len);
189*0Sstevel@tonic-gate memcpy(kex->session_id, hash, kex->session_id_len);
190*0Sstevel@tonic-gate }
191*0Sstevel@tonic-gate kex_derive_keys(kex, hash, shared_secret);
192*0Sstevel@tonic-gate BN_clear_free(shared_secret);
193*0Sstevel@tonic-gate
194*0Sstevel@tonic-gate kex_finish(kex);
195*0Sstevel@tonic-gate }
196