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
|
/* $OpenBSD: kexc25519s.c,v 1.6 2015/01/19 20:16:15 markus Exp $ */
/*
* Copyright (c) 2001 Markus Friedl. All rights reserved.
* Copyright (c) 2010 Damien Miller. All rights reserved.
* Copyright (c) 2013 Aris Adamantiadis. All rights reserved.
*
* 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 <string.h>
#include <signal.h>
#include "sshkey.h"
#include "cipher.h"
#include "digest.h"
#include "kex.h"
#include "log.h"
#include "packet.h"
#include "ssh2.h"
#include "sshbuf.h"
#include "ssherr.h"
static int input_kex_c25519_init(int, u_int32_t, void *);
int
kexc25519_server(struct ssh *ssh)
{
debug("expecting SSH2_MSG_KEX_ECDH_INIT");
ssh_dispatch_set(ssh, SSH2_MSG_KEX_ECDH_INIT, &input_kex_c25519_init);
return 0;
}
static int
input_kex_c25519_init(int type, u_int32_t seq, void *ctxt)
{
struct ssh *ssh = ctxt;
struct kex *kex = ssh->kex;
struct sshkey *server_host_private, *server_host_public;
struct sshbuf *shared_secret = NULL;
u_char *server_host_key_blob = NULL, *signature = NULL;
u_char server_key[CURVE25519_SIZE];
u_char *client_pubkey = NULL;
u_char server_pubkey[CURVE25519_SIZE];
u_char hash[SSH_DIGEST_MAX_LENGTH];
size_t slen, pklen, sbloblen, hashlen;
int r;
/* generate private key */
kexc25519_keygen(server_key, server_pubkey);
#ifdef DEBUG_KEXECDH
dump_digest("server private key:", server_key, sizeof(server_key));
#endif
if (kex->load_host_public_key == NULL ||
kex->load_host_private_key == NULL) {
r = SSH_ERR_INVALID_ARGUMENT;
goto out;
}
if ((server_host_public = kex->load_host_public_key(kex->hostkey_type,
ssh)) == NULL ||
(server_host_private = kex->load_host_private_key(kex->hostkey_type,
ssh)) == NULL) {
r = SSH_ERR_NO_HOSTKEY_LOADED;
goto out;
}
if ((r = sshpkt_get_string(ssh, &client_pubkey, &pklen)) != 0 ||
(r = sshpkt_get_end(ssh)) != 0)
goto out;
if (pklen != CURVE25519_SIZE) {
r = SSH_ERR_SIGNATURE_INVALID;
goto out;
}
#ifdef DEBUG_KEXECDH
dump_digest("client public key:", client_pubkey, CURVE25519_SIZE);
#endif
if ((shared_secret = sshbuf_new()) == NULL) {
r = SSH_ERR_ALLOC_FAIL;
goto out;
}
if ((r = kexc25519_shared_key(server_key, client_pubkey,
shared_secret)) < 0)
goto out;
/* calc H */
if ((r = sshkey_to_blob(server_host_public, &server_host_key_blob,
&sbloblen)) != 0)
goto out;
hashlen = sizeof(hash);
if ((r = kex_c25519_hash(
kex->hash_alg,
kex->client_version_string,
kex->server_version_string,
sshbuf_ptr(kex->peer), sshbuf_len(kex->peer),
sshbuf_ptr(kex->my), sshbuf_len(kex->my),
server_host_key_blob, sbloblen,
client_pubkey,
server_pubkey,
sshbuf_ptr(shared_secret), sshbuf_len(shared_secret),
hash, &hashlen)) < 0)
goto out;
/* save session id := H */
if (kex->session_id == NULL) {
kex->session_id_len = hashlen;
kex->session_id = malloc(kex->session_id_len);
if (kex->session_id == NULL) {
r = SSH_ERR_ALLOC_FAIL;
goto out;
}
memcpy(kex->session_id, hash, kex->session_id_len);
}
/* sign H */
if ((r = kex->sign(server_host_private, server_host_public,
&signature, &slen, hash, hashlen, ssh->compat)) < 0)
goto out;
/* send server hostkey, ECDH pubkey 'Q_S' and signed H */
if ((r = sshpkt_start(ssh, SSH2_MSG_KEX_ECDH_REPLY)) != 0 ||
(r = sshpkt_put_string(ssh, server_host_key_blob, sbloblen)) != 0 ||
(r = sshpkt_put_string(ssh, server_pubkey, sizeof(server_pubkey))) != 0 ||
(r = sshpkt_put_string(ssh, signature, slen)) != 0 ||
(r = sshpkt_send(ssh)) != 0)
goto out;
if ((r = kex_derive_keys(ssh, hash, hashlen, shared_secret)) == 0)
r = kex_send_newkeys(ssh);
out:
explicit_bzero(hash, sizeof(hash));
explicit_bzero(server_key, sizeof(server_key));
free(server_host_key_blob);
free(signature);
free(client_pubkey);
sshbuf_free(shared_secret);
return r;
}
|
