1 /* $OpenBSD: ssh-pkcs11-helper.c,v 1.14 2018/01/08 15:18:46 markus Exp $ */
2 /*
3 * Copyright (c) 2010 Markus Friedl. All rights reserved.
4 *
5 * Permission to use, copy, modify, and distribute this software for any
6 * purpose with or without fee is hereby granted, provided that the above
7 * copyright notice and this permission notice appear in all copies.
8 *
9 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
10 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
11 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
12 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
13 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
14 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
15 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
16 */
17
18 #include "includes.h"
19
20 #include <sys/types.h>
21 #ifdef HAVE_SYS_TIME_H
22 # include <sys/time.h>
23 #endif
24
25 #include "openbsd-compat/sys-queue.h"
26
27 #include <stdarg.h>
28 #include <string.h>
29 #include <unistd.h>
30 #include <errno.h>
31
32 #include "xmalloc.h"
33 #include "sshbuf.h"
34 #include "log.h"
35 #include "misc.h"
36 #include "sshkey.h"
37 #include "authfd.h"
38 #include "ssh-pkcs11.h"
39 #include "ssherr.h"
40
41 #ifdef ENABLE_PKCS11
42
43 /* borrows code from sftp-server and ssh-agent */
44
45 struct pkcs11_keyinfo {
46 struct sshkey *key;
47 char *providername;
48 TAILQ_ENTRY(pkcs11_keyinfo) next;
49 };
50
51 TAILQ_HEAD(, pkcs11_keyinfo) pkcs11_keylist;
52
53 #define MAX_MSG_LENGTH 10240 /*XXX*/
54
55 /* input and output queue */
56 struct sshbuf *iqueue;
57 struct sshbuf *oqueue;
58
59 static void
add_key(struct sshkey * k,char * name)60 add_key(struct sshkey *k, char *name)
61 {
62 struct pkcs11_keyinfo *ki;
63
64 ki = xcalloc(1, sizeof(*ki));
65 ki->providername = xstrdup(name);
66 ki->key = k;
67 TAILQ_INSERT_TAIL(&pkcs11_keylist, ki, next);
68 }
69
70 static void
del_keys_by_name(char * name)71 del_keys_by_name(char *name)
72 {
73 struct pkcs11_keyinfo *ki, *nxt;
74
75 for (ki = TAILQ_FIRST(&pkcs11_keylist); ki; ki = nxt) {
76 nxt = TAILQ_NEXT(ki, next);
77 if (!strcmp(ki->providername, name)) {
78 TAILQ_REMOVE(&pkcs11_keylist, ki, next);
79 free(ki->providername);
80 sshkey_free(ki->key);
81 free(ki);
82 }
83 }
84 }
85
86 /* lookup matching 'private' key */
87 static struct sshkey *
lookup_key(struct sshkey * k)88 lookup_key(struct sshkey *k)
89 {
90 struct pkcs11_keyinfo *ki;
91
92 TAILQ_FOREACH(ki, &pkcs11_keylist, next) {
93 debug("check %p %s", ki, ki->providername);
94 if (sshkey_equal(k, ki->key))
95 return (ki->key);
96 }
97 return (NULL);
98 }
99
100 static void
send_msg(struct sshbuf * m)101 send_msg(struct sshbuf *m)
102 {
103 int r;
104
105 if ((r = sshbuf_put_stringb(oqueue, m)) != 0)
106 fatal("%s: buffer error: %s", __func__, ssh_err(r));
107 }
108
109 static void
process_add(void)110 process_add(void)
111 {
112 char *name, *pin;
113 struct sshkey **keys;
114 int r, i, nkeys;
115 u_char *blob;
116 size_t blen;
117 struct sshbuf *msg;
118
119 if ((msg = sshbuf_new()) == NULL)
120 fatal("%s: sshbuf_new failed", __func__);
121 if ((r = sshbuf_get_cstring(iqueue, &name, NULL)) != 0 ||
122 (r = sshbuf_get_cstring(iqueue, &pin, NULL)) != 0)
123 fatal("%s: buffer error: %s", __func__, ssh_err(r));
124 if ((nkeys = pkcs11_add_provider(name, pin, &keys)) > 0) {
125 if ((r = sshbuf_put_u8(msg,
126 SSH2_AGENT_IDENTITIES_ANSWER)) != 0 ||
127 (r = sshbuf_put_u32(msg, nkeys)) != 0)
128 fatal("%s: buffer error: %s", __func__, ssh_err(r));
129 for (i = 0; i < nkeys; i++) {
130 if ((r = sshkey_to_blob(keys[i], &blob, &blen)) != 0) {
131 debug("%s: sshkey_to_blob: %s",
132 __func__, ssh_err(r));
133 continue;
134 }
135 if ((r = sshbuf_put_string(msg, blob, blen)) != 0 ||
136 (r = sshbuf_put_cstring(msg, name)) != 0)
137 fatal("%s: buffer error: %s",
138 __func__, ssh_err(r));
139 free(blob);
140 add_key(keys[i], name);
141 }
142 free(keys);
143 } else {
144 if ((r = sshbuf_put_u8(msg, SSH_AGENT_FAILURE)) != 0)
145 fatal("%s: buffer error: %s", __func__, ssh_err(r));
146 }
147 free(pin);
148 free(name);
149 send_msg(msg);
150 sshbuf_free(msg);
151 }
152
153 static void
process_del(void)154 process_del(void)
155 {
156 char *name, *pin;
157 struct sshbuf *msg;
158 int r;
159
160 if ((msg = sshbuf_new()) == NULL)
161 fatal("%s: sshbuf_new failed", __func__);
162 if ((r = sshbuf_get_cstring(iqueue, &name, NULL)) != 0 ||
163 (r = sshbuf_get_cstring(iqueue, &pin, NULL)) != 0)
164 fatal("%s: buffer error: %s", __func__, ssh_err(r));
165 del_keys_by_name(name);
166 if ((r = sshbuf_put_u8(msg, pkcs11_del_provider(name) == 0 ?
167 SSH_AGENT_SUCCESS : SSH_AGENT_FAILURE)) != 0)
168 fatal("%s: buffer error: %s", __func__, ssh_err(r));
169 free(pin);
170 free(name);
171 send_msg(msg);
172 sshbuf_free(msg);
173 }
174
175 static void
process_sign(void)176 process_sign(void)
177 {
178 u_char *blob, *data, *signature = NULL;
179 size_t blen, dlen, slen = 0;
180 int r, ok = -1;
181 struct sshkey *key, *found;
182 struct sshbuf *msg;
183
184 /* XXX support SHA2 signature flags */
185 if ((r = sshbuf_get_string(iqueue, &blob, &blen)) != 0 ||
186 (r = sshbuf_get_string(iqueue, &data, &dlen)) != 0 ||
187 (r = sshbuf_get_u32(iqueue, NULL)) != 0)
188 fatal("%s: buffer error: %s", __func__, ssh_err(r));
189
190 if ((r = sshkey_from_blob(blob, blen, &key)) != 0)
191 error("%s: sshkey_from_blob: %s", __func__, ssh_err(r));
192 else {
193 if ((found = lookup_key(key)) != NULL) {
194 #ifdef WITH_OPENSSL
195 int ret;
196
197 slen = RSA_size(key->rsa);
198 signature = xmalloc(slen);
199 if ((ret = RSA_private_encrypt(dlen, data, signature,
200 found->rsa, RSA_PKCS1_PADDING)) != -1) {
201 slen = ret;
202 ok = 0;
203 }
204 #endif /* WITH_OPENSSL */
205 }
206 sshkey_free(key);
207 }
208 if ((msg = sshbuf_new()) == NULL)
209 fatal("%s: sshbuf_new failed", __func__);
210 if (ok == 0) {
211 if ((r = sshbuf_put_u8(msg, SSH2_AGENT_SIGN_RESPONSE)) != 0 ||
212 (r = sshbuf_put_string(msg, signature, slen)) != 0)
213 fatal("%s: buffer error: %s", __func__, ssh_err(r));
214 } else {
215 if ((r = sshbuf_put_u8(msg, SSH2_AGENT_FAILURE)) != 0)
216 fatal("%s: buffer error: %s", __func__, ssh_err(r));
217 }
218 free(data);
219 free(blob);
220 free(signature);
221 send_msg(msg);
222 sshbuf_free(msg);
223 }
224
225 static void
process(void)226 process(void)
227 {
228 u_int msg_len;
229 u_int buf_len;
230 u_int consumed;
231 u_char type;
232 const u_char *cp;
233 int r;
234
235 buf_len = sshbuf_len(iqueue);
236 if (buf_len < 5)
237 return; /* Incomplete message. */
238 cp = sshbuf_ptr(iqueue);
239 msg_len = get_u32(cp);
240 if (msg_len > MAX_MSG_LENGTH) {
241 error("bad message len %d", msg_len);
242 cleanup_exit(11);
243 }
244 if (buf_len < msg_len + 4)
245 return;
246 if ((r = sshbuf_consume(iqueue, 4)) != 0 ||
247 (r = sshbuf_get_u8(iqueue, &type)) != 0)
248 fatal("%s: buffer error: %s", __func__, ssh_err(r));
249 buf_len -= 4;
250 switch (type) {
251 case SSH_AGENTC_ADD_SMARTCARD_KEY:
252 debug("process_add");
253 process_add();
254 break;
255 case SSH_AGENTC_REMOVE_SMARTCARD_KEY:
256 debug("process_del");
257 process_del();
258 break;
259 case SSH2_AGENTC_SIGN_REQUEST:
260 debug("process_sign");
261 process_sign();
262 break;
263 default:
264 error("Unknown message %d", type);
265 break;
266 }
267 /* discard the remaining bytes from the current packet */
268 if (buf_len < sshbuf_len(iqueue)) {
269 error("iqueue grew unexpectedly");
270 cleanup_exit(255);
271 }
272 consumed = buf_len - sshbuf_len(iqueue);
273 if (msg_len < consumed) {
274 error("msg_len %d < consumed %d", msg_len, consumed);
275 cleanup_exit(255);
276 }
277 if (msg_len > consumed) {
278 if ((r = sshbuf_consume(iqueue, msg_len - consumed)) != 0)
279 fatal("%s: buffer error: %s", __func__, ssh_err(r));
280 }
281 }
282
283 void
cleanup_exit(int i)284 cleanup_exit(int i)
285 {
286 /* XXX */
287 _exit(i);
288 }
289
290 int
main(int argc,char ** argv)291 main(int argc, char **argv)
292 {
293 fd_set *rset, *wset;
294 int r, in, out, max, log_stderr = 0;
295 ssize_t len, olen, set_size;
296 SyslogFacility log_facility = SYSLOG_FACILITY_AUTH;
297 LogLevel log_level = SYSLOG_LEVEL_ERROR;
298 char buf[4*4096];
299
300 extern char *__progname;
301
302 ssh_malloc_init(); /* must be called before any mallocs */
303 TAILQ_INIT(&pkcs11_keylist);
304 pkcs11_init(0);
305
306 seed_rng();
307 __progname = ssh_get_progname(argv[0]);
308
309 log_init(__progname, log_level, log_facility, log_stderr);
310
311 in = STDIN_FILENO;
312 out = STDOUT_FILENO;
313
314 max = 0;
315 if (in > max)
316 max = in;
317 if (out > max)
318 max = out;
319
320 if ((iqueue = sshbuf_new()) == NULL)
321 fatal("%s: sshbuf_new failed", __func__);
322 if ((oqueue = sshbuf_new()) == NULL)
323 fatal("%s: sshbuf_new failed", __func__);
324
325 set_size = howmany(max + 1, NFDBITS) * sizeof(fd_mask);
326 rset = xmalloc(set_size);
327 wset = xmalloc(set_size);
328
329 for (;;) {
330 memset(rset, 0, set_size);
331 memset(wset, 0, set_size);
332
333 /*
334 * Ensure that we can read a full buffer and handle
335 * the worst-case length packet it can generate,
336 * otherwise apply backpressure by stopping reads.
337 */
338 if ((r = sshbuf_check_reserve(iqueue, sizeof(buf))) == 0 &&
339 (r = sshbuf_check_reserve(oqueue, MAX_MSG_LENGTH)) == 0)
340 FD_SET(in, rset);
341 else if (r != SSH_ERR_NO_BUFFER_SPACE)
342 fatal("%s: buffer error: %s", __func__, ssh_err(r));
343
344 olen = sshbuf_len(oqueue);
345 if (olen > 0)
346 FD_SET(out, wset);
347
348 if (select(max+1, rset, wset, NULL, NULL) < 0) {
349 if (errno == EINTR)
350 continue;
351 error("select: %s", strerror(errno));
352 cleanup_exit(2);
353 }
354
355 /* copy stdin to iqueue */
356 if (FD_ISSET(in, rset)) {
357 len = read(in, buf, sizeof buf);
358 if (len == 0) {
359 debug("read eof");
360 cleanup_exit(0);
361 } else if (len < 0) {
362 error("read: %s", strerror(errno));
363 cleanup_exit(1);
364 } else if ((r = sshbuf_put(iqueue, buf, len)) != 0) {
365 fatal("%s: buffer error: %s",
366 __func__, ssh_err(r));
367 }
368 }
369 /* send oqueue to stdout */
370 if (FD_ISSET(out, wset)) {
371 len = write(out, sshbuf_ptr(oqueue), olen);
372 if (len < 0) {
373 error("write: %s", strerror(errno));
374 cleanup_exit(1);
375 } else if ((r = sshbuf_consume(oqueue, len)) != 0) {
376 fatal("%s: buffer error: %s",
377 __func__, ssh_err(r));
378 }
379 }
380
381 /*
382 * Process requests from client if we can fit the results
383 * into the output buffer, otherwise stop processing input
384 * and let the output queue drain.
385 */
386 if ((r = sshbuf_check_reserve(oqueue, MAX_MSG_LENGTH)) == 0)
387 process();
388 else if (r != SSH_ERR_NO_BUFFER_SPACE)
389 fatal("%s: buffer error: %s", __func__, ssh_err(r));
390 }
391 }
392 #else /* ENABLE_PKCS11 */
393 int
main(int argc,char ** argv)394 main(int argc, char **argv)
395 {
396 extern char *__progname;
397
398 __progname = ssh_get_progname(argv[0]);
399 log_init(__progname, SYSLOG_LEVEL_ERROR, SYSLOG_FACILITY_AUTH, 0);
400 fatal("PKCS#11 support disabled at compile time");
401 }
402 #endif /* ENABLE_PKCS11 */
403