1*0Sstevel@tonic-gate /*
2*0Sstevel@tonic-gate * Copyright (c) 2001 Markus Friedl. All rights reserved.
3*0Sstevel@tonic-gate *
4*0Sstevel@tonic-gate * Redistribution and use in source and binary forms, with or without
5*0Sstevel@tonic-gate * modification, are permitted provided that the following conditions
6*0Sstevel@tonic-gate * are met:
7*0Sstevel@tonic-gate * 1. Redistributions of source code must retain the above copyright
8*0Sstevel@tonic-gate * notice, this list of conditions and the following disclaimer.
9*0Sstevel@tonic-gate * 2. Redistributions in binary form must reproduce the above copyright
10*0Sstevel@tonic-gate * notice, this list of conditions and the following disclaimer in the
11*0Sstevel@tonic-gate * documentation and/or other materials provided with the distribution.
12*0Sstevel@tonic-gate *
13*0Sstevel@tonic-gate * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
14*0Sstevel@tonic-gate * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
15*0Sstevel@tonic-gate * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
16*0Sstevel@tonic-gate * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
17*0Sstevel@tonic-gate * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
18*0Sstevel@tonic-gate * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
19*0Sstevel@tonic-gate * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
20*0Sstevel@tonic-gate * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
21*0Sstevel@tonic-gate * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
22*0Sstevel@tonic-gate * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
23*0Sstevel@tonic-gate */
24*0Sstevel@tonic-gate
25*0Sstevel@tonic-gate #include "includes.h"
26*0Sstevel@tonic-gate RCSID("$OpenBSD: kexdh.c,v 1.18 2002/03/18 17:50:31 provos Exp $");
27*0Sstevel@tonic-gate
28*0Sstevel@tonic-gate #pragma ident "%Z%%M% %I% %E% SMI"
29*0Sstevel@tonic-gate
30*0Sstevel@tonic-gate #include <openssl/crypto.h>
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
43*0Sstevel@tonic-gate void
kexdh_client(Kex * kex)44*0Sstevel@tonic-gate kexdh_client(Kex *kex)
45*0Sstevel@tonic-gate {
46*0Sstevel@tonic-gate BIGNUM *dh_server_pub = NULL, *shared_secret = NULL;
47*0Sstevel@tonic-gate DH *dh;
48*0Sstevel@tonic-gate Key *server_host_key;
49*0Sstevel@tonic-gate u_char *server_host_key_blob = NULL, *signature = NULL;
50*0Sstevel@tonic-gate u_char *kbuf, *hash;
51*0Sstevel@tonic-gate u_int klen, kout, slen, sbloblen;
52*0Sstevel@tonic-gate
53*0Sstevel@tonic-gate /* generate and send 'e', client DH public key */
54*0Sstevel@tonic-gate dh = dh_new_group1();
55*0Sstevel@tonic-gate dh_gen_key(dh, kex->we_need * 8);
56*0Sstevel@tonic-gate packet_start(SSH2_MSG_KEXDH_INIT);
57*0Sstevel@tonic-gate packet_put_bignum2(dh->pub_key);
58*0Sstevel@tonic-gate packet_send();
59*0Sstevel@tonic-gate
60*0Sstevel@tonic-gate debug("sending SSH2_MSG_KEXDH_INIT");
61*0Sstevel@tonic-gate #ifdef DEBUG_KEXDH
62*0Sstevel@tonic-gate DHparams_print_fp(stderr, dh);
63*0Sstevel@tonic-gate fprintf(stderr, "pub= ");
64*0Sstevel@tonic-gate BN_print_fp(stderr, dh->pub_key);
65*0Sstevel@tonic-gate fprintf(stderr, "\n");
66*0Sstevel@tonic-gate #endif
67*0Sstevel@tonic-gate
68*0Sstevel@tonic-gate debug("expecting SSH2_MSG_KEXDH_REPLY");
69*0Sstevel@tonic-gate packet_read_expect(SSH2_MSG_KEXDH_REPLY);
70*0Sstevel@tonic-gate
71*0Sstevel@tonic-gate /* key, cert */
72*0Sstevel@tonic-gate server_host_key_blob = packet_get_string(&sbloblen);
73*0Sstevel@tonic-gate server_host_key = key_from_blob(server_host_key_blob, sbloblen);
74*0Sstevel@tonic-gate if (server_host_key == NULL)
75*0Sstevel@tonic-gate fatal("cannot decode server_host_key_blob");
76*0Sstevel@tonic-gate if (server_host_key->type != kex->hostkey_type)
77*0Sstevel@tonic-gate fatal("type mismatch for decoded server_host_key_blob");
78*0Sstevel@tonic-gate if (kex->verify_host_key == NULL)
79*0Sstevel@tonic-gate fatal("cannot verify server_host_key");
80*0Sstevel@tonic-gate if (kex->verify_host_key(server_host_key) == -1)
81*0Sstevel@tonic-gate fatal("server_host_key verification failed");
82*0Sstevel@tonic-gate
83*0Sstevel@tonic-gate /* DH paramter f, server public DH key */
84*0Sstevel@tonic-gate if ((dh_server_pub = BN_new()) == NULL)
85*0Sstevel@tonic-gate fatal("dh_server_pub == NULL");
86*0Sstevel@tonic-gate packet_get_bignum2(dh_server_pub);
87*0Sstevel@tonic-gate
88*0Sstevel@tonic-gate #ifdef DEBUG_KEXDH
89*0Sstevel@tonic-gate fprintf(stderr, "dh_server_pub= ");
90*0Sstevel@tonic-gate BN_print_fp(stderr, dh_server_pub);
91*0Sstevel@tonic-gate fprintf(stderr, "\n");
92*0Sstevel@tonic-gate debug("bits %d", BN_num_bits(dh_server_pub));
93*0Sstevel@tonic-gate #endif
94*0Sstevel@tonic-gate
95*0Sstevel@tonic-gate /* signed H */
96*0Sstevel@tonic-gate signature = packet_get_string(&slen);
97*0Sstevel@tonic-gate packet_check_eom();
98*0Sstevel@tonic-gate
99*0Sstevel@tonic-gate if (!dh_pub_is_valid(dh, dh_server_pub))
100*0Sstevel@tonic-gate packet_disconnect("bad server public DH value");
101*0Sstevel@tonic-gate
102*0Sstevel@tonic-gate klen = DH_size(dh);
103*0Sstevel@tonic-gate kbuf = xmalloc(klen);
104*0Sstevel@tonic-gate kout = DH_compute_key(kbuf, dh_server_pub, dh);
105*0Sstevel@tonic-gate #ifdef DEBUG_KEXDH
106*0Sstevel@tonic-gate dump_digest("shared secret", kbuf, kout);
107*0Sstevel@tonic-gate #endif
108*0Sstevel@tonic-gate if ((shared_secret = BN_new()) == NULL)
109*0Sstevel@tonic-gate fatal("kexdh_client: BN_new failed");
110*0Sstevel@tonic-gate BN_bin2bn(kbuf, kout, shared_secret);
111*0Sstevel@tonic-gate memset(kbuf, 0, klen);
112*0Sstevel@tonic-gate xfree(kbuf);
113*0Sstevel@tonic-gate
114*0Sstevel@tonic-gate /* calc and verify H */
115*0Sstevel@tonic-gate hash = kex_dh_hash(
116*0Sstevel@tonic-gate kex->client_version_string,
117*0Sstevel@tonic-gate kex->server_version_string,
118*0Sstevel@tonic-gate buffer_ptr(&kex->my), buffer_len(&kex->my),
119*0Sstevel@tonic-gate buffer_ptr(&kex->peer), buffer_len(&kex->peer),
120*0Sstevel@tonic-gate server_host_key_blob, sbloblen,
121*0Sstevel@tonic-gate dh->pub_key,
122*0Sstevel@tonic-gate dh_server_pub,
123*0Sstevel@tonic-gate shared_secret
124*0Sstevel@tonic-gate );
125*0Sstevel@tonic-gate xfree(server_host_key_blob);
126*0Sstevel@tonic-gate BN_clear_free(dh_server_pub);
127*0Sstevel@tonic-gate DH_free(dh);
128*0Sstevel@tonic-gate
129*0Sstevel@tonic-gate if (key_verify(server_host_key, signature, slen, hash, 20) != 1)
130*0Sstevel@tonic-gate fatal("key_verify failed for server_host_key");
131*0Sstevel@tonic-gate key_free(server_host_key);
132*0Sstevel@tonic-gate xfree(signature);
133*0Sstevel@tonic-gate
134*0Sstevel@tonic-gate /* save session id */
135*0Sstevel@tonic-gate if (kex->session_id == NULL) {
136*0Sstevel@tonic-gate kex->session_id_len = 20;
137*0Sstevel@tonic-gate kex->session_id = xmalloc(kex->session_id_len);
138*0Sstevel@tonic-gate memcpy(kex->session_id, hash, kex->session_id_len);
139*0Sstevel@tonic-gate }
140*0Sstevel@tonic-gate
141*0Sstevel@tonic-gate kex_derive_keys(kex, hash, shared_secret);
142*0Sstevel@tonic-gate BN_clear_free(shared_secret);
143*0Sstevel@tonic-gate kex_finish(kex);
144*0Sstevel@tonic-gate }
145