1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
|
/* $OpenBSD: kexecdhc.c,v 1.7 2014/02/02 03:44:31 djm Exp $ */
/*
* Copyright (c) 2001 Markus Friedl. All rights reserved.
* Copyright (c) 2010 Damien Miller. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#include "includes.h"
#include <sys/types.h>
#include <stdio.h>
#include <string.h>
#include <signal.h>
#include "xmalloc.h"
#include "buffer.h"
#include "key.h"
#include "cipher.h"
#include "kex.h"
#include "log.h"
#include "packet.h"
#include "dh.h"
#include "ssh2.h"
#ifdef OPENSSL_HAS_ECC
#include <openssl/ecdh.h>
void
kexecdh_client(Kex *kex)
{
EC_KEY *client_key;
EC_POINT *server_public;
const EC_GROUP *group;
BIGNUM *shared_secret;
Key *server_host_key;
u_char *server_host_key_blob = NULL, *signature = NULL;
u_char *kbuf, *hash;
u_int klen, slen, sbloblen, hashlen;
if ((client_key = EC_KEY_new_by_curve_name(kex->ec_nid)) == NULL)
fatal("%s: EC_KEY_new_by_curve_name failed", __func__);
if (EC_KEY_generate_key(client_key) != 1)
fatal("%s: EC_KEY_generate_key failed", __func__);
group = EC_KEY_get0_group(client_key);
packet_start(SSH2_MSG_KEX_ECDH_INIT);
packet_put_ecpoint(group, EC_KEY_get0_public_key(client_key));
packet_send();
debug("sending SSH2_MSG_KEX_ECDH_INIT");
#ifdef DEBUG_KEXECDH
fputs("client private key:\n", stderr);
key_dump_ec_key(client_key);
#endif
debug("expecting SSH2_MSG_KEX_ECDH_REPLY");
packet_read_expect(SSH2_MSG_KEX_ECDH_REPLY);
/* hostkey */
server_host_key_blob = packet_get_string(&sbloblen);
server_host_key = key_from_blob(server_host_key_blob, sbloblen);
if (server_host_key == NULL)
fatal("cannot decode server_host_key_blob");
if (server_host_key->type != kex->hostkey_type)
fatal("type mismatch for decoded server_host_key_blob");
if (kex->verify_host_key == NULL)
fatal("cannot verify server_host_key");
if (kex->verify_host_key(server_host_key) == -1)
fatal("server_host_key verification failed");
/* Q_S, server public key */
if ((server_public = EC_POINT_new(group)) == NULL)
fatal("%s: EC_POINT_new failed", __func__);
packet_get_ecpoint(group, server_public);
if (key_ec_validate_public(group, server_public) != 0)
fatal("%s: invalid server public key", __func__);
#ifdef DEBUG_KEXECDH
fputs("server public key:\n", stderr);
key_dump_ec_point(group, server_public);
#endif
/* signed H */
signature = packet_get_string(&slen);
packet_check_eom();
klen = (EC_GROUP_get_degree(group) + 7) / 8;
kbuf = xmalloc(klen);
if (ECDH_compute_key(kbuf, klen, server_public,
client_key, NULL) != (int)klen)
fatal("%s: ECDH_compute_key failed", __func__);
#ifdef DEBUG_KEXECDH
dump_digest("shared secret", kbuf, klen);
#endif
if ((shared_secret = BN_new()) == NULL)
fatal("%s: BN_new failed", __func__);
if (BN_bin2bn(kbuf, klen, shared_secret) == NULL)
fatal("%s: BN_bin2bn failed", __func__);
explicit_bzero(kbuf, klen);
free(kbuf);
/* calc and verify H */
kex_ecdh_hash(
kex->hash_alg,
group,
kex->client_version_string,
kex->server_version_string,
buffer_ptr(&kex->my), buffer_len(&kex->my),
buffer_ptr(&kex->peer), buffer_len(&kex->peer),
server_host_key_blob, sbloblen,
EC_KEY_get0_public_key(client_key),
server_public,
shared_secret,
&hash, &hashlen
);
free(server_host_key_blob);
EC_POINT_clear_free(server_public);
EC_KEY_free(client_key);
if (key_verify(server_host_key, signature, slen, hash, hashlen) != 1)
fatal("key_verify failed for server_host_key");
key_free(server_host_key);
free(signature);
/* save session id */
if (kex->session_id == NULL) {
kex->session_id_len = hashlen;
kex->session_id = xmalloc(kex->session_id_len);
memcpy(kex->session_id, hash, kex->session_id_len);
}
kex_derive_keys_bn(kex, hash, hashlen, shared_secret);
BN_clear_free(shared_secret);
kex_finish(kex);
}
#else /* OPENSSL_HAS_ECC */
void
kexecdh_client(Kex *kex)
{
fatal("ECC support is not enabled");
}
#endif /* OPENSSL_HAS_ECC */
|
