blob: 2700b7219a6fc6409b060c49d0cd8f351df3e076 [file] [log] [blame]
Damien Millera5103f42014-02-04 11:20:14 +11001/* $OpenBSD: kexecdhs.c,v 1.10 2014/02/02 03:44:31 djm Exp $ */
Damien Millereb8b60e2010-08-31 22:41:14 +10002/*
3 * Copyright (c) 2001 Markus Friedl. All rights reserved.
4 * Copyright (c) 2010 Damien Miller. All rights reserved.
5 *
6 * Redistribution and use in source and binary forms, with or without
7 * modification, are permitted provided that the following conditions
8 * are met:
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.
14 *
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.
25 */
26
Damien Millerc79ff072010-08-31 22:50:48 +100027#include "includes.h"
28
Damien Millereb8b60e2010-08-31 22:41:14 +100029#include <sys/types.h>
30#include <string.h>
31#include <signal.h>
32
Damien Millereb8b60e2010-08-31 22:41:14 +100033#include "xmalloc.h"
34#include "buffer.h"
35#include "key.h"
36#include "cipher.h"
37#include "kex.h"
38#include "log.h"
39#include "packet.h"
Damien Millereb8b60e2010-08-31 22:41:14 +100040#include "ssh2.h"
Damien Millereb8b60e2010-08-31 22:41:14 +100041
Damien Miller6af914a2010-09-10 11:39:26 +100042#ifdef OPENSSL_HAS_ECC
43
44#include <openssl/ecdh.h>
45
Damien Millereb8b60e2010-08-31 22:41:14 +100046void
47kexecdh_server(Kex *kex)
48{
49 EC_POINT *client_public;
50 EC_KEY *server_key;
51 const EC_GROUP *group;
52 BIGNUM *shared_secret;
53 Key *server_host_private, *server_host_public;
54 u_char *server_host_key_blob = NULL, *signature = NULL;
55 u_char *kbuf, *hash;
56 u_int klen, slen, sbloblen, hashlen;
Damien Millereb8b60e2010-08-31 22:41:14 +100057
Damien Millerea111192013-04-23 19:24:32 +100058 if ((server_key = EC_KEY_new_by_curve_name(kex->ec_nid)) == NULL)
Damien Millereb8b60e2010-08-31 22:41:14 +100059 fatal("%s: EC_KEY_new_by_curve_name failed", __func__);
60 if (EC_KEY_generate_key(server_key) != 1)
61 fatal("%s: EC_KEY_generate_key failed", __func__);
62 group = EC_KEY_get0_group(server_key);
63
64#ifdef DEBUG_KEXECDH
65 fputs("server private key:\n", stderr);
66 key_dump_ec_key(server_key);
67#endif
68
69 if (kex->load_host_public_key == NULL ||
70 kex->load_host_private_key == NULL)
71 fatal("Cannot load hostkey");
72 server_host_public = kex->load_host_public_key(kex->hostkey_type);
73 if (server_host_public == NULL)
74 fatal("Unsupported hostkey type %d", kex->hostkey_type);
75 server_host_private = kex->load_host_private_key(kex->hostkey_type);
Damien Millereb8b60e2010-08-31 22:41:14 +100076
77 debug("expecting SSH2_MSG_KEX_ECDH_INIT");
78 packet_read_expect(SSH2_MSG_KEX_ECDH_INIT);
79 if ((client_public = EC_POINT_new(group)) == NULL)
80 fatal("%s: EC_POINT_new failed", __func__);
81 packet_get_ecpoint(group, client_public);
82 packet_check_eom();
83
84 if (key_ec_validate_public(group, client_public) != 0)
85 fatal("%s: invalid client public key", __func__);
86
87#ifdef DEBUG_KEXECDH
88 fputs("client public key:\n", stderr);
89 key_dump_ec_point(group, client_public);
90#endif
91
92 /* Calculate shared_secret */
93 klen = (EC_GROUP_get_degree(group) + 7) / 8;
94 kbuf = xmalloc(klen);
95 if (ECDH_compute_key(kbuf, klen, client_public,
96 server_key, NULL) != (int)klen)
97 fatal("%s: ECDH_compute_key failed", __func__);
98
99#ifdef DEBUG_KEXDH
100 dump_digest("shared secret", kbuf, klen);
101#endif
102 if ((shared_secret = BN_new()) == NULL)
103 fatal("%s: BN_new failed", __func__);
104 if (BN_bin2bn(kbuf, klen, shared_secret) == NULL)
105 fatal("%s: BN_bin2bn failed", __func__);
Damien Millera5103f42014-02-04 11:20:14 +1100106 explicit_bzero(kbuf, klen);
Darren Tuckera627d422013-06-02 07:31:17 +1000107 free(kbuf);
Damien Millereb8b60e2010-08-31 22:41:14 +1000108
109 /* calc H */
110 key_to_blob(server_host_public, &server_host_key_blob, &sbloblen);
111 kex_ecdh_hash(
Damien Millerb3051d02014-01-10 10:58:53 +1100112 kex->hash_alg,
Damien Millereb8b60e2010-08-31 22:41:14 +1000113 group,
114 kex->client_version_string,
115 kex->server_version_string,
116 buffer_ptr(&kex->peer), buffer_len(&kex->peer),
117 buffer_ptr(&kex->my), buffer_len(&kex->my),
118 server_host_key_blob, sbloblen,
119 client_public,
120 EC_KEY_get0_public_key(server_key),
121 shared_secret,
122 &hash, &hashlen
123 );
124 EC_POINT_clear_free(client_public);
125
126 /* save session id := H */
127 if (kex->session_id == NULL) {
128 kex->session_id_len = hashlen;
129 kex->session_id = xmalloc(kex->session_id_len);
130 memcpy(kex->session_id, hash, kex->session_id_len);
131 }
132
133 /* sign H */
Damien Miller85b45e02013-07-20 13:21:52 +1000134 kex->sign(server_host_private, server_host_public, &signature, &slen,
135 hash, hashlen);
Damien Millereb8b60e2010-08-31 22:41:14 +1000136
137 /* destroy_sensitive_data(); */
138
139 /* send server hostkey, ECDH pubkey 'Q_S' and signed H */
140 packet_start(SSH2_MSG_KEX_ECDH_REPLY);
141 packet_put_string(server_host_key_blob, sbloblen);
142 packet_put_ecpoint(group, EC_KEY_get0_public_key(server_key));
143 packet_put_string(signature, slen);
144 packet_send();
145
Darren Tuckera627d422013-06-02 07:31:17 +1000146 free(signature);
147 free(server_host_key_blob);
Damien Millereb8b60e2010-08-31 22:41:14 +1000148 /* have keys, free server key */
149 EC_KEY_free(server_key);
150
Damien Miller91b580e2014-01-12 19:21:22 +1100151 kex_derive_keys_bn(kex, hash, hashlen, shared_secret);
Damien Millereb8b60e2010-08-31 22:41:14 +1000152 BN_clear_free(shared_secret);
153 kex_finish(kex);
154}
Damien Miller6af914a2010-09-10 11:39:26 +1000155#else /* OPENSSL_HAS_ECC */
156void
157kexecdh_server(Kex *kex)
158{
159 fatal("ECC support is not enabled");
160}
161#endif /* OPENSSL_HAS_ECC */