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
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
|
/*
* Dropbear - a SSH2 server
*
* Copyright (c) 2002,2003 Matt Johnston
* Copyright (c) 2004 by Mihnea Stoenescu
* All rights reserved.
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
* SOFTWARE. */
#include "includes.h"
#include "dbutil.h"
#include "algo.h"
#include "buffer.h"
#include "session.h"
#include "kex.h"
#include "ssh.h"
#include "packet.h"
#include "bignum.h"
#include "random.h"
#include "runopts.h"
#include "ecc.h"
#include "gensignkey.h"
static void send_msg_kexdh_reply(mp_int *dh_e, buffer *ecdh_qs);
/* Handle a diffie-hellman key exchange initialisation. This involves
* calculating a session key reply value, and corresponding hash. These
* are carried out by send_msg_kexdh_reply(). recv_msg_kexdh_init() calls
* that function, then brings the new keys into use */
void recv_msg_kexdh_init() {
DEF_MP_INT(dh_e);
buffer *ecdh_qs = NULL;
TRACE(("enter recv_msg_kexdh_init"))
if (!ses.kexstate.recvkexinit) {
dropbear_exit("Premature kexdh_init message received");
}
if (IS_NORMAL_DH(ses.newkeys->algo_kex)) {
m_mp_init(&dh_e);
if (buf_getmpint(ses.payload, &dh_e) != DROPBEAR_SUCCESS) {
dropbear_exit("Failed to get kex value");
}
} else {
#ifdef DROPBEAR_ECDH
ecdh_qs = buf_getstringbuf(ses.payload);
#endif
}
send_msg_kexdh_reply(&dh_e, ecdh_qs);
mp_clear(&dh_e);
if (ecdh_qs) {
buf_free(ecdh_qs);
}
send_msg_newkeys();
ses.requirenext[0] = SSH_MSG_NEWKEYS;
ses.requirenext[1] = 0;
TRACE(("leave recv_msg_kexdh_init"))
}
static void svr_ensure_hostkey() {
const char* fn = NULL;
char *fn_temp = NULL;
enum signkey_type type = ses.newkeys->algo_hostkey;
void **hostkey = signkey_key_ptr(svr_opts.hostkey, type);
int ret = DROPBEAR_FAILURE;
if (hostkey && *hostkey) {
return;
}
switch (type)
{
#ifdef DROPBEAR_RSA
case DROPBEAR_SIGNKEY_RSA:
fn = RSA_PRIV_FILENAME;
break;
#endif
#ifdef DROPBEAR_DSS
case DROPBEAR_SIGNKEY_DSS:
fn = DSS_PRIV_FILENAME;
break;
#endif
#ifdef DROPBEAR_ECDSA
case DROPBEAR_SIGNKEY_ECDSA_NISTP256:
case DROPBEAR_SIGNKEY_ECDSA_NISTP384:
case DROPBEAR_SIGNKEY_ECDSA_NISTP521:
fn = ECDSA_PRIV_FILENAME;
break;
#endif
default:
(void)0;
}
if (readhostkey(fn, svr_opts.hostkey, &type) == DROPBEAR_SUCCESS) {
return;
}
fn_temp = m_malloc(strlen(fn) + 20);
snprintf(fn_temp, strlen(fn)+20, "%s.tmp%d", fn, getpid());
if (signkey_generate(type, 0, fn_temp) == DROPBEAR_FAILURE) {
goto out;
}
if (link(fn_temp, fn) < 0) {
if (errno != EEXIST) {
dropbear_log(LOG_ERR, "Failed moving key file to %s", fn);
/* XXX fallback to non-atomic copy for some filesystems? */
goto out;
}
}
ret = readhostkey(fn, svr_opts.hostkey, &type);
out:
if (fn_temp) {
unlink(fn_temp);
m_free(fn_temp);
}
if (ret == DROPBEAR_FAILURE)
{
dropbear_exit("Couldn't read or generate hostkey");
}
// directory for keys.
// Create lockfile first, or wait if it exists. PID!
// Generate key
// write it, load to memory
// atomic rename, done.
}
/* Generate our side of the diffie-hellman key exchange value (dh_f), and
* calculate the session key using the diffie-hellman algorithm. Following
* that, the session hash is calculated, and signed with RSA or DSS. The
* result is sent to the client.
*
* See the transport RFC4253 section 8 for details
* or RFC5656 section 4 for elliptic curve variant. */
static void send_msg_kexdh_reply(mp_int *dh_e, buffer *ecdh_qs) {
TRACE(("enter send_msg_kexdh_reply"))
/* we can start creating the kexdh_reply packet */
CHECKCLEARTOWRITE();
svr_ensure_hostkey();
buf_putbyte(ses.writepayload, SSH_MSG_KEXDH_REPLY);
buf_put_pub_key(ses.writepayload, svr_opts.hostkey,
ses.newkeys->algo_hostkey);
if (IS_NORMAL_DH(ses.newkeys->algo_kex)) {
// Normal diffie-hellman
struct kex_dh_param * dh_param = gen_kexdh_param();
kexdh_comb_key(dh_param, dh_e, svr_opts.hostkey);
/* put f */
buf_putmpint(ses.writepayload, &dh_param->pub);
free_kexdh_param(dh_param);
} else {
#ifdef DROPBEAR_ECDH
struct kex_ecdh_param *ecdh_param = gen_kexecdh_param();
kexecdh_comb_key(ecdh_param, ecdh_qs, svr_opts.hostkey);
buf_put_ecc_raw_pubkey_string(ses.writepayload, &ecdh_param->key);
free_kexecdh_param(ecdh_param);
#endif
}
/* calc the signature */
buf_put_sign(ses.writepayload, svr_opts.hostkey,
ses.newkeys->algo_hostkey, ses.hash);
/* the SSH_MSG_KEXDH_REPLY is done */
encrypt_packet();
TRACE(("leave send_msg_kexdh_reply"))
}
|
