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
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
|
/* $OpenBSD: ssh-sk-helper.c,v 1.4 2019/12/13 19:11:14 djm Exp $ */
/*
* Copyright (c) 2019 Google LLC
*
* Permission to use, copy, modify, and distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
/*
* This is a tiny program used to isolate the address space used for
* security key middleware signing operations from ssh-agent. It is similar
* to ssh-pkcs11-helper.c but considerably simpler as the operations for
* security keys are stateless.
*
* Please crank SSH_SK_HELPER_VERSION in sshkey.h for any incompatible
* protocol changes.
*/
#include "includes.h"
#include <limits.h>
#include <stdarg.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <errno.h>
#include "xmalloc.h"
#include "log.h"
#include "sshkey.h"
#include "authfd.h"
#include "misc.h"
#include "sshbuf.h"
#include "msg.h"
#include "uidswap.h"
#include "sshkey.h"
#include "ssherr.h"
#include "ssh-sk.h"
#ifdef ENABLE_SK
extern char *__progname;
static struct sshbuf *
process_sign(struct sshbuf *req)
{
int r = SSH_ERR_INTERNAL_ERROR;
struct sshbuf *resp, *kbuf;
struct sshkey *key;
uint32_t compat;
const u_char *message;
u_char *sig;
size_t msglen, siglen;
char *provider;
if ((r = sshbuf_froms(req, &kbuf)) != 0 ||
(r = sshbuf_get_cstring(req, &provider, NULL)) != 0 ||
(r = sshbuf_get_string_direct(req, &message, &msglen)) != 0 ||
(r = sshbuf_get_cstring(req, NULL, NULL)) != 0 || /* alg */
(r = sshbuf_get_u32(req, &compat)) != 0)
fatal("%s: buffer error: %s", __progname, ssh_err(r));
if (sshbuf_len(req) != 0)
fatal("%s: trailing data in request", __progname);
if ((r = sshkey_private_deserialize(kbuf, &key)) != 0)
fatal("Unable to parse private key: %s", ssh_err(r));
if (!sshkey_is_sk(key))
fatal("Unsupported key type %s", sshkey_ssh_name(key));
debug("%s: ready to sign with key %s, provider %s: "
"msg len %zu, compat 0x%lx", __progname, sshkey_type(key),
provider, msglen, (u_long)compat);
if ((r = sshsk_sign(provider, key, &sig, &siglen,
message, msglen, compat)) != 0)
fatal("Signing failed: %s", ssh_err(r));
if ((resp = sshbuf_new()) == NULL)
fatal("%s: sshbuf_new failed", __progname);
if ((r = sshbuf_put_string(resp, sig, siglen)) != 0)
fatal("%s: buffer error: %s", __progname, ssh_err(r));
sshbuf_free(kbuf);
free(provider);
return resp;
}
static struct sshbuf *
process_enroll(struct sshbuf *req)
{
int r;
u_int type;
char *provider;
char *application;
uint8_t flags;
struct sshbuf *challenge, *attest, *kbuf, *resp;
struct sshkey *key;
if ((resp = sshbuf_new()) == NULL ||
(attest = sshbuf_new()) == NULL ||
(kbuf = sshbuf_new()) == NULL)
fatal("%s: sshbuf_new failed", __progname);
if ((r = sshbuf_get_u32(req, &type)) != 0 ||
(r = sshbuf_get_cstring(req, &provider, NULL)) != 0 ||
(r = sshbuf_get_cstring(req, &application, NULL)) != 0 ||
(r = sshbuf_get_u8(req, &flags)) != 0 ||
(r = sshbuf_froms(req, &challenge)) != 0)
fatal("%s: buffer error: %s", __progname, ssh_err(r));
if (sshbuf_len(req) != 0)
fatal("%s: trailing data in request", __progname);
if (type > INT_MAX)
fatal("%s: bad type %u", __progname, type);
if (sshbuf_len(challenge) == 0) {
sshbuf_free(challenge);
challenge = NULL;
}
if ((r = sshsk_enroll((int)type, provider, application, flags,
challenge, &key, attest)) != 0)
fatal("%s: sshsk_enroll failed: %s", __progname, ssh_err(r));
if ((r = sshkey_private_serialize(key, kbuf)) != 0)
fatal("%s: serialize private key: %s", __progname, ssh_err(r));
if ((r = sshbuf_put_stringb(resp, kbuf)) != 0 ||
(r = sshbuf_put_stringb(resp, attest)) != 0)
fatal("%s: buffer error: %s", __progname, ssh_err(r));
sshkey_free(key);
sshbuf_free(kbuf);
sshbuf_free(attest);
sshbuf_free(challenge);
free(provider);
free(application);
return resp;
}
int
main(int argc, char **argv)
{
SyslogFacility log_facility = SYSLOG_FACILITY_AUTH;
LogLevel log_level = SYSLOG_LEVEL_ERROR;
int in, out, ch, r, log_stderr = 0;
u_int rtype;
uint8_t version;
sanitise_stdfd();
log_init(__progname, log_level, log_facility, log_stderr);
while ((ch = getopt(argc, argv, "v")) != -1) {
switch (ch) {
case 'v':
log_stderr = 1;
if (log_level == SYSLOG_LEVEL_ERROR)
log_level = SYSLOG_LEVEL_DEBUG1;
else if (log_level < SYSLOG_LEVEL_DEBUG3)
log_level++;
break;
default:
fprintf(stderr, "usage: %s [-v]\n", __progname);
exit(1);
}
}
log_init(__progname, log_level, log_facility, log_stderr);
/*
* Rearrange our file descriptors a little; we don't trust the
* providers not to fiddle with stdin/out.
*/
closefrom(STDERR_FILENO + 1);
if ((in = dup(STDIN_FILENO)) == -1 || (out = dup(STDOUT_FILENO)) == -1)
fatal("%s: dup: %s", __progname, strerror(errno));
close(STDIN_FILENO);
close(STDOUT_FILENO);
sanitise_stdfd(); /* resets to /dev/null */
if ((req = sshbuf_new()) == NULL)
fatal("%s: sshbuf_new failed", __progname);
if (ssh_msg_recv(in, req) < 0)
fatal("ssh_msg_recv failed");
close(in);
debug("%s: received message len %zu", __progname, sshbuf_len(req));
if ((r = sshbuf_get_u8(req, &version)) != 0)
fatal("%s: buffer error: %s", __progname, ssh_err(r));
if (version != SSH_SK_HELPER_VERSION) {
fatal("unsupported version: received %d, expected %d",
version, SSH_SK_HELPER_VERSION);
}
if ((r = sshbuf_get_u32(req, &rtype)) != 0)
fatal("%s: buffer error: %s", __progname, ssh_err(r));
switch (rtype) {
case SSH_SK_HELPER_SIGN:
resp = process_sign(req);
break;
case SSH_SK_HELPER_ENROLL:
resp = process_enroll(req);
break;
default:
fatal("%s: unsupported request type %u", __progname, rtype);
}
sshbuf_free(req);
debug("%s: reply len %zu", __progname, sshbuf_len(resp));
if (ssh_msg_send(out, SSH_SK_HELPER_VERSION, resp) == -1)
fatal("ssh_msg_send failed");
sshbuf_free(resp);
close(out);
return (0);
}
#else /* ENABLE_SK */
#include <stdio.h>
int
main(int argc, char **argv)
{
fprintf(stderr, "ssh-sk-helper: disabled at compile time\n");
return -1;
}
#endif /* ENABLE_SK */
|
