blob: fe6dc53f85912ccf291340358f75454db5302600 [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: kexdhc.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
36void
37kexdh_client(Kex *kex)
38{
39 BIGNUM *dh_server_pub = NULL, *shared_secret = NULL;
40 DH *dh;
41 Key *server_host_key;
42 u_char *server_host_key_blob = NULL, *signature = NULL;
43 u_char *kbuf, *hash;
44 u_int klen, kout, slen, sbloblen;
45
46 /* generate and send 'e', client DH public key */
47 dh = dh_new_group1();
48 dh_gen_key(dh, kex->we_need * 8);
49 packet_start(SSH2_MSG_KEXDH_INIT);
50 packet_put_bignum2(dh->pub_key);
51 packet_send();
52
53 debug("sending SSH2_MSG_KEXDH_INIT");
54#ifdef DEBUG_KEXDH
55 DHparams_print_fp(stderr, dh);
56 fprintf(stderr, "pub= ");
57 BN_print_fp(stderr, dh->pub_key);
58 fprintf(stderr, "\n");
59#endif
60
61 debug("expecting SSH2_MSG_KEXDH_REPLY");
62 packet_read_expect(SSH2_MSG_KEXDH_REPLY);
63
64 /* key, cert */
65 server_host_key_blob = packet_get_string(&sbloblen);
66 server_host_key = key_from_blob(server_host_key_blob, sbloblen);
67 if (server_host_key == NULL)
68 fatal("cannot decode server_host_key_blob");
69 if (server_host_key->type != kex->hostkey_type)
70 fatal("type mismatch for decoded server_host_key_blob");
71 if (kex->verify_host_key == NULL)
72 fatal("cannot verify server_host_key");
73 if (kex->verify_host_key(server_host_key) == -1)
74 fatal("server_host_key verification failed");
75
76 /* DH paramter f, server public DH key */
77 if ((dh_server_pub = BN_new()) == NULL)
78 fatal("dh_server_pub == NULL");
79 packet_get_bignum2(dh_server_pub);
80
81#ifdef DEBUG_KEXDH
82 fprintf(stderr, "dh_server_pub= ");
83 BN_print_fp(stderr, dh_server_pub);
84 fprintf(stderr, "\n");
85 debug("bits %d", BN_num_bits(dh_server_pub));
86#endif
87
88 /* signed H */
89 signature = packet_get_string(&slen);
90 packet_check_eom();
91
92 if (!dh_pub_is_valid(dh, dh_server_pub))
93 packet_disconnect("bad server public DH value");
94
95 klen = DH_size(dh);
96 kbuf = xmalloc(klen);
97 kout = DH_compute_key(kbuf, dh_server_pub, dh);
98#ifdef DEBUG_KEXDH
99 dump_digest("shared secret", kbuf, kout);
100#endif
101 if ((shared_secret = BN_new()) == NULL)
102 fatal("kexdh_client: BN_new failed");
103 BN_bin2bn(kbuf, kout, shared_secret);
104 memset(kbuf, 0, klen);
105 xfree(kbuf);
106
107 /* calc and verify H */
108 hash = kex_dh_hash(
109 kex->client_version_string,
110 kex->server_version_string,
111 buffer_ptr(&kex->my), buffer_len(&kex->my),
112 buffer_ptr(&kex->peer), buffer_len(&kex->peer),
113 server_host_key_blob, sbloblen,
114 dh->pub_key,
115 dh_server_pub,
116 shared_secret
117 );
118 xfree(server_host_key_blob);
119 BN_clear_free(dh_server_pub);
120 DH_free(dh);
121
122 if (key_verify(server_host_key, signature, slen, hash, 20) != 1)
123 fatal("key_verify failed for server_host_key");
124 key_free(server_host_key);
125 xfree(signature);
126
127 /* save session id */
128 if (kex->session_id == NULL) {
129 kex->session_id_len = 20;
130 kex->session_id = xmalloc(kex->session_id_len);
131 memcpy(kex->session_id, hash, kex->session_id_len);
132 }
133
134 kex_derive_keys(kex, hash, shared_secret);
135 BN_clear_free(shared_secret);
136 kex_finish(kex);
137}