blob: f04bce8255c92dc35204a88e051c077273414ff6 [file] [log] [blame]
Damien Miller8e7fb332003-02-24 12:03:03 +11001/*
2 * Copyright (c) 2001 Markus Friedl. All rights reserved.
3 *
4 * Redistribution and use in source and binary forms, with or without
5 * modification, are permitted provided that the following conditions
6 * are met:
7 * 1. Redistributions of source code must retain the above copyright
8 * notice, this list of conditions and the following disclaimer.
9 * 2. Redistributions in binary form must reproduce the above copyright
10 * notice, this list of conditions and the following disclaimer in the
11 * documentation and/or other materials provided with the distribution.
12 *
13 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
14 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
15 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
16 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
17 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
18 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
19 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
20 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
21 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
22 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
23 */
24
25#include "includes.h"
26RCSID("$OpenBSD: kexdhs.c,v 1.1 2003/02/16 17:09:57 markus Exp $");
27
28#include "xmalloc.h"
29#include "key.h"
30#include "kex.h"
31#include "log.h"
32#include "packet.h"
33#include "dh.h"
34#include "ssh2.h"
35#include "monitor_wrap.h"
36
37void
38kexdh_server(Kex *kex)
39{
40 BIGNUM *shared_secret = NULL, *dh_client_pub = NULL;
41 DH *dh;
42 Key *server_host_key;
43 u_char *kbuf, *hash, *signature = NULL, *server_host_key_blob = NULL;
44 u_int sbloblen, klen, kout;
45 u_int slen;
46
47 /* generate server DH public key */
48 dh = dh_new_group1();
49 dh_gen_key(dh, kex->we_need * 8);
50
51 debug("expecting SSH2_MSG_KEXDH_INIT");
52 packet_read_expect(SSH2_MSG_KEXDH_INIT);
53
54 if (kex->load_host_key == NULL)
55 fatal("Cannot load hostkey");
56 server_host_key = kex->load_host_key(kex->hostkey_type);
57 if (server_host_key == NULL)
58 fatal("Unsupported hostkey type %d", kex->hostkey_type);
59
60 /* key, cert */
61 if ((dh_client_pub = BN_new()) == NULL)
62 fatal("dh_client_pub == NULL");
63 packet_get_bignum2(dh_client_pub);
64 packet_check_eom();
65
66#ifdef DEBUG_KEXDH
67 fprintf(stderr, "dh_client_pub= ");
68 BN_print_fp(stderr, dh_client_pub);
69 fprintf(stderr, "\n");
70 debug("bits %d", BN_num_bits(dh_client_pub));
71#endif
72
73#ifdef DEBUG_KEXDH
74 DHparams_print_fp(stderr, dh);
75 fprintf(stderr, "pub= ");
76 BN_print_fp(stderr, dh->pub_key);
77 fprintf(stderr, "\n");
78#endif
79 if (!dh_pub_is_valid(dh, dh_client_pub))
80 packet_disconnect("bad client public DH value");
81
82 klen = DH_size(dh);
83 kbuf = xmalloc(klen);
84 kout = DH_compute_key(kbuf, dh_client_pub, dh);
85#ifdef DEBUG_KEXDH
86 dump_digest("shared secret", kbuf, kout);
87#endif
88 if ((shared_secret = BN_new()) == NULL)
89 fatal("kexdh_server: BN_new failed");
90 BN_bin2bn(kbuf, kout, shared_secret);
91 memset(kbuf, 0, klen);
92 xfree(kbuf);
93
94 key_to_blob(server_host_key, &server_host_key_blob, &sbloblen);
95
96 /* calc H */
97 hash = kex_dh_hash(
98 kex->client_version_string,
99 kex->server_version_string,
100 buffer_ptr(&kex->peer), buffer_len(&kex->peer),
101 buffer_ptr(&kex->my), buffer_len(&kex->my),
102 server_host_key_blob, sbloblen,
103 dh_client_pub,
104 dh->pub_key,
105 shared_secret
106 );
107 BN_clear_free(dh_client_pub);
108
109 /* save session id := H */
110 /* XXX hashlen depends on KEX */
111 if (kex->session_id == NULL) {
112 kex->session_id_len = 20;
113 kex->session_id = xmalloc(kex->session_id_len);
114 memcpy(kex->session_id, hash, kex->session_id_len);
115 }
116
117 /* sign H */
118 /* XXX hashlen depends on KEX */
119 PRIVSEP(key_sign(server_host_key, &signature, &slen, hash, 20));
120
121 /* destroy_sensitive_data(); */
122
123 /* send server hostkey, DH pubkey 'f' and singed H */
124 packet_start(SSH2_MSG_KEXDH_REPLY);
125 packet_put_string(server_host_key_blob, sbloblen);
126 packet_put_bignum2(dh->pub_key); /* f */
127 packet_put_string(signature, slen);
128 packet_send();
129
130 xfree(signature);
131 xfree(server_host_key_blob);
132 /* have keys, free DH */
133 DH_free(dh);
134
135 kex_derive_keys(kex, hash, shared_secret);
136 BN_clear_free(shared_secret);
137 kex_finish(kex);
138}