1/* $OpenBSD: ssh-pkcs11-helper.c,v 1.12 2016/02/15 09:47:49 dtucker 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;
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#ifdef WITH_OPENSSL
183			int ret;
184
185			slen = RSA_size(key->rsa);
186			signature = xmalloc(slen);
187			if ((ret = RSA_private_encrypt(dlen, data, signature,
188			    found->rsa, RSA_PKCS1_PADDING)) != -1) {
189				slen = ret;
190				ok = 0;
191			}
192#endif /* WITH_OPENSSL */
193		}
194		key_free(key);
195	}
196	buffer_init(&msg);
197	if (ok == 0) {
198		buffer_put_char(&msg, SSH2_AGENT_SIGN_RESPONSE);
199		buffer_put_string(&msg, signature, slen);
200	} else {
201		buffer_put_char(&msg, SSH_AGENT_FAILURE);
202	}
203	free(data);
204	free(blob);
205	free(signature);
206	send_msg(&msg);
207	buffer_free(&msg);
208}
209
210static void
211process(void)
212{
213	u_int msg_len;
214	u_int buf_len;
215	u_int consumed;
216	u_int type;
217	u_char *cp;
218
219	buf_len = buffer_len(&iqueue);
220	if (buf_len < 5)
221		return;		/* Incomplete message. */
222	cp = buffer_ptr(&iqueue);
223	msg_len = get_u32(cp);
224	if (msg_len > MAX_MSG_LENGTH) {
225		error("bad message len %d", msg_len);
226		cleanup_exit(11);
227	}
228	if (buf_len < msg_len + 4)
229		return;
230	buffer_consume(&iqueue, 4);
231	buf_len -= 4;
232	type = buffer_get_char(&iqueue);
233	switch (type) {
234	case SSH_AGENTC_ADD_SMARTCARD_KEY:
235		debug("process_add");
236		process_add();
237		break;
238	case SSH_AGENTC_REMOVE_SMARTCARD_KEY:
239		debug("process_del");
240		process_del();
241		break;
242	case SSH2_AGENTC_SIGN_REQUEST:
243		debug("process_sign");
244		process_sign();
245		break;
246	default:
247		error("Unknown message %d", type);
248		break;
249	}
250	/* discard the remaining bytes from the current packet */
251	if (buf_len < buffer_len(&iqueue)) {
252		error("iqueue grew unexpectedly");
253		cleanup_exit(255);
254	}
255	consumed = buf_len - buffer_len(&iqueue);
256	if (msg_len < consumed) {
257		error("msg_len %d < consumed %d", msg_len, consumed);
258		cleanup_exit(255);
259	}
260	if (msg_len > consumed)
261		buffer_consume(&iqueue, msg_len - consumed);
262}
263
264void
265cleanup_exit(int i)
266{
267	/* XXX */
268	_exit(i);
269}
270
271int
272main(int argc, char **argv)
273{
274	fd_set *rset, *wset;
275	int in, out, max, log_stderr = 0;
276	ssize_t len, olen, set_size;
277	SyslogFacility log_facility = SYSLOG_FACILITY_AUTH;
278	LogLevel log_level = SYSLOG_LEVEL_ERROR;
279	char buf[4*4096];
280
281	extern char *__progname;
282
283	ssh_malloc_init();	/* must be called before any mallocs */
284	TAILQ_INIT(&pkcs11_keylist);
285	pkcs11_init(0);
286
287	seed_rng();
288	__progname = ssh_get_progname(argv[0]);
289
290	log_init(__progname, log_level, log_facility, log_stderr);
291
292	in = STDIN_FILENO;
293	out = STDOUT_FILENO;
294
295	max = 0;
296	if (in > max)
297		max = in;
298	if (out > max)
299		max = out;
300
301	buffer_init(&iqueue);
302	buffer_init(&oqueue);
303
304	set_size = howmany(max + 1, NFDBITS) * sizeof(fd_mask);
305	rset = xmalloc(set_size);
306	wset = xmalloc(set_size);
307
308	for (;;) {
309		memset(rset, 0, set_size);
310		memset(wset, 0, set_size);
311
312		/*
313		 * Ensure that we can read a full buffer and handle
314		 * the worst-case length packet it can generate,
315		 * otherwise apply backpressure by stopping reads.
316		 */
317		if (buffer_check_alloc(&iqueue, sizeof(buf)) &&
318		    buffer_check_alloc(&oqueue, MAX_MSG_LENGTH))
319			FD_SET(in, rset);
320
321		olen = buffer_len(&oqueue);
322		if (olen > 0)
323			FD_SET(out, wset);
324
325		if (select(max+1, rset, wset, NULL, NULL) < 0) {
326			if (errno == EINTR)
327				continue;
328			error("select: %s", strerror(errno));
329			cleanup_exit(2);
330		}
331
332		/* copy stdin to iqueue */
333		if (FD_ISSET(in, rset)) {
334			len = read(in, buf, sizeof buf);
335			if (len == 0) {
336				debug("read eof");
337				cleanup_exit(0);
338			} else if (len < 0) {
339				error("read: %s", strerror(errno));
340				cleanup_exit(1);
341			} else {
342				buffer_append(&iqueue, buf, len);
343			}
344		}
345		/* send oqueue to stdout */
346		if (FD_ISSET(out, wset)) {
347			len = write(out, buffer_ptr(&oqueue), olen);
348			if (len < 0) {
349				error("write: %s", strerror(errno));
350				cleanup_exit(1);
351			} else {
352				buffer_consume(&oqueue, len);
353			}
354		}
355
356		/*
357		 * Process requests from client if we can fit the results
358		 * into the output buffer, otherwise stop processing input
359		 * and let the output queue drain.
360		 */
361		if (buffer_check_alloc(&oqueue, MAX_MSG_LENGTH))
362			process();
363	}
364}
365#else /* ENABLE_PKCS11 */
366int
367main(int argc, char **argv)
368{
369	extern char *__progname;
370
371	__progname = ssh_get_progname(argv[0]);
372	log_init(__progname, SYSLOG_LEVEL_ERROR, SYSLOG_FACILITY_AUTH, 0);
373	fatal("PKCS#11 support disabled at compile time");
374}
375#endif /* ENABLE_PKCS11 */
376