ssh-pkcs11-helper.c revision 262566 
1/* $OpenBSD: ssh-pkcs11-helper.c,v 1.7 2013/12/02 02:56:17 djm 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 "buffer.h"
34#include "log.h"
35#include "misc.h"
36#include "key.h"
37#include "authfd.h"
38#include "ssh-pkcs11.h"
39
40#ifdef ENABLE_PKCS11
41
42/* borrows code from sftp-server and ssh-agent */
43
44struct pkcs11_keyinfo {
45	Key		*key;
46	char		*providername;
47	TAILQ_ENTRY(pkcs11_keyinfo) next;
48};
49
50TAILQ_HEAD(, pkcs11_keyinfo) pkcs11_keylist;
51
52#define MAX_MSG_LENGTH		10240 /*XXX*/
53
54/* helper */
55#define get_int()			buffer_get_int(&iqueue);
56#define get_string(lenp)		buffer_get_string(&iqueue, lenp);
57
58/* input and output queue */
59Buffer iqueue;
60Buffer oqueue;
61
62static void
63add_key(Key *k, char *name)
64{
65	struct pkcs11_keyinfo *ki;
66
67	ki = xcalloc(1, sizeof(*ki));
68	ki->providername = xstrdup(name);
69	ki->key = k;
70	TAILQ_INSERT_TAIL(&pkcs11_keylist, ki, next);
71}
72
73static void
74del_keys_by_name(char *name)
75{
76	struct pkcs11_keyinfo *ki, *nxt;
77
78	for (ki = TAILQ_FIRST(&pkcs11_keylist); ki; ki = nxt) {
79		nxt = TAILQ_NEXT(ki, next);
80		if (!strcmp(ki->providername, name)) {
81			TAILQ_REMOVE(&pkcs11_keylist, ki, next);
82			free(ki->providername);
83			key_free(ki->key);
84			free(ki);
85		}
86	}
87}
88
89/* lookup matching 'private' key */
90static Key *
91lookup_key(Key *k)
92{
93	struct pkcs11_keyinfo *ki;
94
95	TAILQ_FOREACH(ki, &pkcs11_keylist, next) {
96		debug("check %p %s", ki, ki->providername);
97		if (key_equal(k, ki->key))
98			return (ki->key);
99	}
100	return (NULL);
101}
102
103static void
104send_msg(Buffer *m)
105{
106	int mlen = buffer_len(m);
107
108	buffer_put_int(&oqueue, mlen);
109	buffer_append(&oqueue, buffer_ptr(m), mlen);
110	buffer_consume(m, mlen);
111}
112
113static void
114process_add(void)
115{
116	char *name, *pin;
117	Key **keys;
118	int i, nkeys;
119	u_char *blob;
120	u_int blen;
121	Buffer msg;
122
123	buffer_init(&msg);
124	name = get_string(NULL);
125	pin = get_string(NULL);
126	if ((nkeys = pkcs11_add_provider(name, pin, &keys)) > 0) {
127		buffer_put_char(&msg, SSH2_AGENT_IDENTITIES_ANSWER);
128		buffer_put_int(&msg, nkeys);
129		for (i = 0; i < nkeys; i++) {
130			if (key_to_blob(keys[i], &blob, &blen) == 0)
131				continue;
132			buffer_put_string(&msg, blob, blen);
133			buffer_put_cstring(&msg, name);
134			free(blob);
135			add_key(keys[i], name);
136		}
137		free(keys);
138	} else {
139		buffer_put_char(&msg, SSH_AGENT_FAILURE);
140	}
141	free(pin);
142	free(name);
143	send_msg(&msg);
144	buffer_free(&msg);
145}
146
147static void
148process_del(void)
149{
150	char *name, *pin;
151	Buffer msg;
152
153	buffer_init(&msg);
154	name = get_string(NULL);
155	pin = get_string(NULL);
156	del_keys_by_name(name);
157	if (pkcs11_del_provider(name) == 0)
158		 buffer_put_char(&msg, SSH_AGENT_SUCCESS);
159	else
160		 buffer_put_char(&msg, SSH_AGENT_FAILURE);
161	free(pin);
162	free(name);
163	send_msg(&msg);
164	buffer_free(&msg);
165}
166
167static void
168process_sign(void)
169{
170	u_char *blob, *data, *signature = NULL;
171	u_int blen, dlen, slen = 0;
172	int ok = -1, ret;
173	Key *key, *found;
174	Buffer msg;
175
176	blob = get_string(&blen);
177	data = get_string(&dlen);
178	(void)get_int(); /* XXX ignore flags */
179
180	if ((key = key_from_blob(blob, blen)) != NULL) {
181		if ((found = lookup_key(key)) != NULL) {
182			slen = RSA_size(key->rsa);
183			signature = xmalloc(slen);
184			if ((ret = RSA_private_encrypt(dlen, data, signature,
185			    found->rsa, RSA_PKCS1_PADDING)) != -1) {
186				slen = ret;
187				ok = 0;
188			}
189		}
190		key_free(key);
191	}
192	buffer_init(&msg);
193	if (ok == 0) {
194		buffer_put_char(&msg, SSH2_AGENT_SIGN_RESPONSE);
195		buffer_put_string(&msg, signature, slen);
196	} else {
197		buffer_put_char(&msg, SSH_AGENT_FAILURE);
198	}
199	free(data);
200	free(blob);
201	free(signature);
202	send_msg(&msg);
203	buffer_free(&msg);
204}
205
206static void
207process(void)
208{
209	u_int msg_len;
210	u_int buf_len;
211	u_int consumed;
212	u_int type;
213	u_char *cp;
214
215	buf_len = buffer_len(&iqueue);
216	if (buf_len < 5)
217		return;		/* Incomplete message. */
218	cp = buffer_ptr(&iqueue);
219	msg_len = get_u32(cp);
220	if (msg_len > MAX_MSG_LENGTH) {
221		error("bad message len %d", msg_len);
222		cleanup_exit(11);
223	}
224	if (buf_len < msg_len + 4)
225		return;
226	buffer_consume(&iqueue, 4);
227	buf_len -= 4;
228	type = buffer_get_char(&iqueue);
229	switch (type) {
230	case SSH_AGENTC_ADD_SMARTCARD_KEY:
231		debug("process_add");
232		process_add();
233		break;
234	case SSH_AGENTC_REMOVE_SMARTCARD_KEY:
235		debug("process_del");
236		process_del();
237		break;
238	case SSH2_AGENTC_SIGN_REQUEST:
239		debug("process_sign");
240		process_sign();
241		break;
242	default:
243		error("Unknown message %d", type);
244		break;
245	}
246	/* discard the remaining bytes from the current packet */
247	if (buf_len < buffer_len(&iqueue)) {
248		error("iqueue grew unexpectedly");
249		cleanup_exit(255);
250	}
251	consumed = buf_len - buffer_len(&iqueue);
252	if (msg_len < consumed) {
253		error("msg_len %d < consumed %d", msg_len, consumed);
254		cleanup_exit(255);
255	}
256	if (msg_len > consumed)
257		buffer_consume(&iqueue, msg_len - consumed);
258}
259
260void
261cleanup_exit(int i)
262{
263	/* XXX */
264	_exit(i);
265}
266
267int
268main(int argc, char **argv)
269{
270	fd_set *rset, *wset;
271	int in, out, max, log_stderr = 0;
272	ssize_t len, olen, set_size;
273	SyslogFacility log_facility = SYSLOG_FACILITY_AUTH;
274	LogLevel log_level = SYSLOG_LEVEL_ERROR;
275	char buf[4*4096];
276
277	extern char *__progname;
278
279	TAILQ_INIT(&pkcs11_keylist);
280	pkcs11_init(0);
281
282	seed_rng();
283	__progname = ssh_get_progname(argv[0]);
284
285	log_init(__progname, log_level, log_facility, log_stderr);
286
287	in = STDIN_FILENO;
288	out = STDOUT_FILENO;
289
290	max = 0;
291	if (in > max)
292		max = in;
293	if (out > max)
294		max = out;
295
296	buffer_init(&iqueue);
297	buffer_init(&oqueue);
298
299	set_size = howmany(max + 1, NFDBITS) * sizeof(fd_mask);
300	rset = (fd_set *)xmalloc(set_size);
301	wset = (fd_set *)xmalloc(set_size);
302
303	for (;;) {
304		memset(rset, 0, set_size);
305		memset(wset, 0, set_size);
306
307		/*
308		 * Ensure that we can read a full buffer and handle
309		 * the worst-case length packet it can generate,
310		 * otherwise apply backpressure by stopping reads.
311		 */
312		if (buffer_check_alloc(&iqueue, sizeof(buf)) &&
313		    buffer_check_alloc(&oqueue, MAX_MSG_LENGTH))
314			FD_SET(in, rset);
315
316		olen = buffer_len(&oqueue);
317		if (olen > 0)
318			FD_SET(out, wset);
319
320		if (select(max+1, rset, wset, NULL, NULL) < 0) {
321			if (errno == EINTR)
322				continue;
323			error("select: %s", strerror(errno));
324			cleanup_exit(2);
325		}
326
327		/* copy stdin to iqueue */
328		if (FD_ISSET(in, rset)) {
329			len = read(in, buf, sizeof buf);
330			if (len == 0) {
331				debug("read eof");
332				cleanup_exit(0);
333			} else if (len < 0) {
334				error("read: %s", strerror(errno));
335				cleanup_exit(1);
336			} else {
337				buffer_append(&iqueue, buf, len);
338			}
339		}
340		/* send oqueue to stdout */
341		if (FD_ISSET(out, wset)) {
342			len = write(out, buffer_ptr(&oqueue), olen);
343			if (len < 0) {
344				error("write: %s", strerror(errno));
345				cleanup_exit(1);
346			} else {
347				buffer_consume(&oqueue, len);
348			}
349		}
350
351		/*
352		 * Process requests from client if we can fit the results
353		 * into the output buffer, otherwise stop processing input
354		 * and let the output queue drain.
355		 */
356		if (buffer_check_alloc(&oqueue, MAX_MSG_LENGTH))
357			process();
358	}
359}
360#else /* ENABLE_PKCS11 */
361int
362main(int argc, char **argv)
363{
364	extern char *__progname;
365
366	__progname = ssh_get_progname(argv[0]);
367	log_init(__progname, SYSLOG_LEVEL_ERROR, SYSLOG_FACILITY_AUTH, 0);
368	fatal("PKCS#11 support disabled at compile time");
369}
370#endif /* ENABLE_PKCS11 */
371