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
166
167
168
169
170
171
172
173
174
175
176
177
178
|
/* $OpenBSD: kexdhc.c,v 1.27 2019/01/21 10:00:23 djm Exp $ */
/*
* Copyright (c) 2001 Markus Friedl. 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 <sys/types.h>
#include <openssl/dh.h>
#include <stdio.h>
#include <string.h>
#include <signal.h>
#include "sshkey.h"
#include "cipher.h"
#include "digest.h"
#include "dh.h"
#include "kex.h"
#include "log.h"
#include "packet.h"
#include "ssh2.h"
#include "dispatch.h"
#include "compat.h"
#include "ssherr.h"
#include "sshbuf.h"
static int input_kex_dh(int, u_int32_t, struct ssh *);
int
kexdh_client(struct ssh *ssh)
{
struct kex *kex = ssh->kex;
int r;
const BIGNUM *pub_key;
/* generate and send 'e', client DH public key */
if ((r = kex_dh_keygen(kex)) != 0)
goto out;
debug("sending SSH2_MSG_KEXDH_INIT");
DH_get0_key(kex->dh, &pub_key, NULL);
if ((r = sshpkt_start(ssh, SSH2_MSG_KEXDH_INIT)) != 0 ||
(r = sshpkt_put_bignum2(ssh, pub_key)) != 0 ||
(r = sshpkt_send(ssh)) != 0)
goto out;
#ifdef DEBUG_KEXDH
DHparams_print_fp(stderr, kex->dh);
fprintf(stderr, "pub= ");
BN_print_fp(stderr, pub_key);
fprintf(stderr, "\n");
#endif
debug("expecting SSH2_MSG_KEXDH_REPLY");
ssh_dispatch_set(ssh, SSH2_MSG_KEXDH_REPLY, &input_kex_dh);
r = 0;
out:
return r;
}
static int
input_kex_dh(int type, u_int32_t seq, struct ssh *ssh)
{
struct kex *kex = ssh->kex;
BIGNUM *dh_server_pub = NULL, *shared_secret = NULL;
const BIGNUM *pub_key;
struct sshkey *server_host_key = NULL;
u_char *kbuf = NULL, *server_host_key_blob = NULL, *signature = NULL;
u_char hash[SSH_DIGEST_MAX_LENGTH];
size_t klen = 0, slen, sbloblen, hashlen;
int kout, r;
if (kex->verify_host_key == NULL) {
r = SSH_ERR_INVALID_ARGUMENT;
goto out;
}
/* key, cert */
if ((r = sshpkt_get_string(ssh, &server_host_key_blob,
&sbloblen)) != 0 ||
(r = sshkey_from_blob(server_host_key_blob, sbloblen,
&server_host_key)) != 0)
goto out;
if (server_host_key->type != kex->hostkey_type ||
(kex->hostkey_type == KEY_ECDSA &&
server_host_key->ecdsa_nid != kex->hostkey_nid)) {
r = SSH_ERR_KEY_TYPE_MISMATCH;
goto out;
}
if (kex->verify_host_key(server_host_key, ssh) == -1) {
r = SSH_ERR_SIGNATURE_INVALID;
goto out;
}
/* DH parameter f, server public DH key, signed H */
if ((r = sshpkt_get_bignum2(ssh, &dh_server_pub)) != 0 ||
(r = sshpkt_get_string(ssh, &signature, &slen)) != 0 ||
(r = sshpkt_get_end(ssh)) != 0)
goto out;
#ifdef DEBUG_KEXDH
fprintf(stderr, "dh_server_pub= ");
BN_print_fp(stderr, dh_server_pub);
fprintf(stderr, "\n");
debug("bits %d", BN_num_bits(dh_server_pub));
#endif
if (!dh_pub_is_valid(kex->dh, dh_server_pub)) {
sshpkt_disconnect(ssh, "bad server public DH value");
r = SSH_ERR_MESSAGE_INCOMPLETE;
goto out;
}
klen = DH_size(kex->dh);
if ((kbuf = malloc(klen)) == NULL ||
(shared_secret = BN_new()) == NULL) {
r = SSH_ERR_ALLOC_FAIL;
goto out;
}
if ((kout = DH_compute_key(kbuf, dh_server_pub, kex->dh)) < 0 ||
BN_bin2bn(kbuf, kout, shared_secret) == NULL) {
r = SSH_ERR_LIBCRYPTO_ERROR;
goto out;
}
#ifdef DEBUG_KEXDH
dump_digest("shared secret", kbuf, kout);
#endif
/* calc and verify H */
DH_get0_key(kex->dh, &pub_key, NULL);
hashlen = sizeof(hash);
if ((r = kex_dh_hash(
kex->hash_alg,
kex->client_version,
kex->server_version,
sshbuf_ptr(kex->my), sshbuf_len(kex->my),
sshbuf_ptr(kex->peer), sshbuf_len(kex->peer),
server_host_key_blob, sbloblen,
pub_key,
dh_server_pub,
shared_secret,
hash, &hashlen)) != 0)
goto out;
if ((r = sshkey_verify(server_host_key, signature, slen, hash, hashlen,
kex->hostkey_alg, ssh->compat)) != 0)
goto out;
if ((r = kex_derive_keys_bn(ssh, hash, hashlen, shared_secret)) == 0)
r = kex_send_newkeys(ssh);
out:
explicit_bzero(hash, sizeof(hash));
DH_free(kex->dh);
kex->dh = NULL;
BN_clear_free(dh_server_pub);
if (kbuf) {
explicit_bzero(kbuf, klen);
free(kbuf);
}
BN_clear_free(shared_secret);
sshkey_free(server_host_key);
free(server_host_key_blob);
free(signature);
return r;
}
|
