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
45struct pkcs11_keyinfo {
46	struct sshkey	*key;
47	char		*providername;
48	TAILQ_ENTRY(pkcs11_keyinfo) next;
49};
50
51TAILQ_HEAD(, pkcs11_keyinfo) pkcs11_keylist;
52
53#define MAX_MSG_LENGTH		10240 /*XXX*/
54
55/* input and output queue */
56struct sshbuf *iqueue;
57struct sshbuf *oqueue;
58
59static void
60add_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
70static void
71del_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 */
87static struct sshkey *
88lookup_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
100static void
101send_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
109static void
110process_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
153static void
154process_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
175static void
176process_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
225static void
226process(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
283void
284cleanup_exit(int i)
285{
286	/* XXX */
287	_exit(i);
288}
289
290int
291main(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 */
393int
394main(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