ssh-pkcs11-helper.c revision 255767 
1/* $OpenBSD: ssh-pkcs11-helper.c,v 1.6 2013/05/17 00:13:14 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			key_to_blob(keys[i], &blob, &blen);
131			buffer_put_string(&msg, blob, blen);
132			buffer_put_cstring(&msg, name);
133			free(blob);
134			add_key(keys[i], name);
135		}
136		free(keys);
137	} else {
138		buffer_put_char(&msg, SSH_AGENT_FAILURE);
139	}
140	free(pin);
141	free(name);
142	send_msg(&msg);
143	buffer_free(&msg);
144}
145
146static void
147process_del(void)
148{
149	char *name, *pin;
150	Buffer msg;
151
152	buffer_init(&msg);
153	name = get_string(NULL);
154	pin = get_string(NULL);
155	del_keys_by_name(name);
156	if (pkcs11_del_provider(name) == 0)
157		 buffer_put_char(&msg, SSH_AGENT_SUCCESS);
158	else
159		 buffer_put_char(&msg, SSH_AGENT_FAILURE);
160	free(pin);
161	free(name);
162	send_msg(&msg);
163	buffer_free(&msg);
164}
165
166static void
167process_sign(void)
168{
169	u_char *blob, *data, *signature = NULL;
170	u_int blen, dlen, slen = 0;
171	int ok = -1, ret;
172	Key *key, *found;
173	Buffer msg;
174
175	blob = get_string(&blen);
176	data = get_string(&dlen);
177	(void)get_int(); /* XXX ignore flags */
178
179	if ((key = key_from_blob(blob, blen)) != NULL) {
180		if ((found = lookup_key(key)) != NULL) {
181			slen = RSA_size(key->rsa);
182			signature = xmalloc(slen);
183			if ((ret = RSA_private_encrypt(dlen, data, signature,
184			    found->rsa, RSA_PKCS1_PADDING)) != -1) {
185				slen = ret;
186				ok = 0;
187			}
188		}
189		key_free(key);
190	}
191	buffer_init(&msg);
192	if (ok == 0) {
193		buffer_put_char(&msg, SSH2_AGENT_SIGN_RESPONSE);
194		buffer_put_string(&msg, signature, slen);
195	} else {
196		buffer_put_char(&msg, SSH_AGENT_FAILURE);
197	}
198	free(data);
199	free(blob);
200	free(signature);
201	send_msg(&msg);
202	buffer_free(&msg);
203}
204
205static void
206process(void)
207{
208	u_int msg_len;
209	u_int buf_len;
210	u_int consumed;
211	u_int type;
212	u_char *cp;
213
214	buf_len = buffer_len(&iqueue);
215	if (buf_len < 5)
216		return;		/* Incomplete message. */
217	cp = buffer_ptr(&iqueue);
218	msg_len = get_u32(cp);
219	if (msg_len > MAX_MSG_LENGTH) {
220		error("bad message len %d", msg_len);
221		cleanup_exit(11);
222	}
223	if (buf_len < msg_len + 4)
224		return;
225	buffer_consume(&iqueue, 4);
226	buf_len -= 4;
227	type = buffer_get_char(&iqueue);
228	switch (type) {
229	case SSH_AGENTC_ADD_SMARTCARD_KEY:
230		debug("process_add");
231		process_add();
232		break;
233	case SSH_AGENTC_REMOVE_SMARTCARD_KEY:
234		debug("process_del");
235		process_del();
236		break;
237	case SSH2_AGENTC_SIGN_REQUEST:
238		debug("process_sign");
239		process_sign();
240		break;
241	default:
242		error("Unknown message %d", type);
243		break;
244	}
245	/* discard the remaining bytes from the current packet */
246	if (buf_len < buffer_len(&iqueue)) {
247		error("iqueue grew unexpectedly");
248		cleanup_exit(255);
249	}
250	consumed = buf_len - buffer_len(&iqueue);
251	if (msg_len < consumed) {
252		error("msg_len %d < consumed %d", msg_len, consumed);
253		cleanup_exit(255);
254	}
255	if (msg_len > consumed)
256		buffer_consume(&iqueue, msg_len - consumed);
257}
258
259void
260cleanup_exit(int i)
261{
262	/* XXX */
263	_exit(i);
264}
265
266int
267main(int argc, char **argv)
268{
269	fd_set *rset, *wset;
270	int in, out, max, log_stderr = 0;
271	ssize_t len, olen, set_size;
272	SyslogFacility log_facility = SYSLOG_FACILITY_AUTH;
273	LogLevel log_level = SYSLOG_LEVEL_ERROR;
274	char buf[4*4096];
275
276	extern char *__progname;
277
278	TAILQ_INIT(&pkcs11_keylist);
279	pkcs11_init(0);
280
281	seed_rng();
282	__progname = ssh_get_progname(argv[0]);
283
284	log_init(__progname, log_level, log_facility, log_stderr);
285
286	in = STDIN_FILENO;
287	out = STDOUT_FILENO;
288
289	max = 0;
290	if (in > max)
291		max = in;
292	if (out > max)
293		max = out;
294
295	buffer_init(&iqueue);
296	buffer_init(&oqueue);
297
298	set_size = howmany(max + 1, NFDBITS) * sizeof(fd_mask);
299	rset = (fd_set *)xmalloc(set_size);
300	wset = (fd_set *)xmalloc(set_size);
301
302	for (;;) {
303		memset(rset, 0, set_size);
304		memset(wset, 0, set_size);
305
306		/*
307		 * Ensure that we can read a full buffer and handle
308		 * the worst-case length packet it can generate,
309		 * otherwise apply backpressure by stopping reads.
310		 */
311		if (buffer_check_alloc(&iqueue, sizeof(buf)) &&
312		    buffer_check_alloc(&oqueue, MAX_MSG_LENGTH))
313			FD_SET(in, rset);
314
315		olen = buffer_len(&oqueue);
316		if (olen > 0)
317			FD_SET(out, wset);
318
319		if (select(max+1, rset, wset, NULL, NULL) < 0) {
320			if (errno == EINTR)
321				continue;
322			error("select: %s", strerror(errno));
323			cleanup_exit(2);
324		}
325
326		/* copy stdin to iqueue */
327		if (FD_ISSET(in, rset)) {
328			len = read(in, buf, sizeof buf);
329			if (len == 0) {
330				debug("read eof");
331				cleanup_exit(0);
332			} else if (len < 0) {
333				error("read: %s", strerror(errno));
334				cleanup_exit(1);
335			} else {
336				buffer_append(&iqueue, buf, len);
337			}
338		}
339		/* send oqueue to stdout */
340		if (FD_ISSET(out, wset)) {
341			len = write(out, buffer_ptr(&oqueue), olen);
342			if (len < 0) {
343				error("write: %s", strerror(errno));
344				cleanup_exit(1);
345			} else {
346				buffer_consume(&oqueue, len);
347			}
348		}
349
350		/*
351		 * Process requests from client if we can fit the results
352		 * into the output buffer, otherwise stop processing input
353		 * and let the output queue drain.
354		 */
355		if (buffer_check_alloc(&oqueue, MAX_MSG_LENGTH))
356			process();
357	}
358}
359#else /* ENABLE_PKCS11 */
360int
361main(int argc, char **argv)
362{
363	extern char *__progname;
364
365	__progname = ssh_get_progname(argv[0]);
366	log_init(__progname, SYSLOG_LEVEL_ERROR, SYSLOG_FACILITY_AUTH, 0);
367	fatal("PKCS#11 support disabled at compile time");
368}
369#endif /* ENABLE_PKCS11 */
370