1/*	$NetBSD: ssh-pkcs11-helper.c,v 1.22 2022/02/23 19:07:20 christos Exp $	*/
2/* $OpenBSD: ssh-pkcs11-helper.c,v 1.26 2021/11/18 03:31:44 djm Exp $ */
3/*
4 * Copyright (c) 2010 Markus Friedl.  All rights reserved.
5 *
6 * Permission to use, copy, modify, and distribute this software for any
7 * purpose with or without fee is hereby granted, provided that the above
8 * copyright notice and this permission notice appear in all copies.
9 *
10 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
11 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
12 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
13 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
14 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
15 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
16 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
17 */
18#include "includes.h"
19__RCSID("$NetBSD: ssh-pkcs11-helper.c,v 1.22 2022/02/23 19:07:20 christos Exp $");
20
21#include <sys/types.h>
22#include <sys/queue.h>
23#include <sys/time.h>
24#include <sys/param.h>
25
26#include <stdlib.h>
27#include <errno.h>
28#include <poll.h>
29#include <stdarg.h>
30#include <string.h>
31#include <unistd.h>
32
33#include "xmalloc.h"
34#include "sshbuf.h"
35#include "log.h"
36#include "misc.h"
37#include "sshkey.h"
38#include "authfd.h"
39#include "ssh-pkcs11.h"
40#include "ssherr.h"
41
42#ifdef WITH_OPENSSL
43
44/* borrows code from sftp-server and ssh-agent */
45
46struct pkcs11_keyinfo {
47	struct sshkey	*key;
48	char		*providername, *label;
49	TAILQ_ENTRY(pkcs11_keyinfo) next;
50};
51
52TAILQ_HEAD(, pkcs11_keyinfo) pkcs11_keylist;
53
54#define MAX_MSG_LENGTH		10240 /*XXX*/
55
56/* input and output queue */
57struct sshbuf *iqueue;
58struct sshbuf *oqueue;
59
60static void
61add_key(struct sshkey *k, char *name, char *label)
62{
63	struct pkcs11_keyinfo *ki;
64
65	ki = xcalloc(1, sizeof(*ki));
66	ki->providername = xstrdup(name);
67	ki->key = k;
68	ki->label = xstrdup(label);
69	TAILQ_INSERT_TAIL(&pkcs11_keylist, ki, next);
70}
71
72static void
73del_keys_by_name(char *name)
74{
75	struct pkcs11_keyinfo *ki, *nxt;
76
77	for (ki = TAILQ_FIRST(&pkcs11_keylist); ki; ki = nxt) {
78		nxt = TAILQ_NEXT(ki, next);
79		if (!strcmp(ki->providername, name)) {
80			TAILQ_REMOVE(&pkcs11_keylist, ki, next);
81			free(ki->providername);
82			free(ki->label);
83			sshkey_free(ki->key);
84			free(ki);
85		}
86	}
87}
88
89/* lookup matching 'private' key */
90static struct sshkey *
91lookup_key(struct sshkey *k)
92{
93	struct pkcs11_keyinfo *ki;
94
95	TAILQ_FOREACH(ki, &pkcs11_keylist, next) {
96		debug("check %s %s %s", sshkey_type(ki->key),
97		    ki->providername, ki->label);
98		if (sshkey_equal(k, ki->key))
99			return (ki->key);
100	}
101	return (NULL);
102}
103
104static void
105send_msg(struct sshbuf *m)
106{
107	int r;
108
109	if ((r = sshbuf_put_stringb(oqueue, m)) != 0)
110		fatal_fr(r, "enqueue");
111}
112
113static void
114process_add(void)
115{
116	char *name, *pin;
117	struct sshkey **keys = NULL;
118	int r, i, nkeys;
119	u_char *blob;
120	size_t blen;
121	struct sshbuf *msg;
122	char **labels = NULL;
123
124	if ((msg = sshbuf_new()) == NULL)
125		fatal_f("sshbuf_new failed");
126	if ((r = sshbuf_get_cstring(iqueue, &name, NULL)) != 0 ||
127	    (r = sshbuf_get_cstring(iqueue, &pin, NULL)) != 0)
128		fatal_fr(r, "parse");
129	if ((nkeys = pkcs11_add_provider(name, pin, &keys, &labels)) > 0) {
130		if ((r = sshbuf_put_u8(msg,
131		    SSH2_AGENT_IDENTITIES_ANSWER)) != 0 ||
132		    (r = sshbuf_put_u32(msg, nkeys)) != 0)
133			fatal_fr(r, "compose");
134		for (i = 0; i < nkeys; i++) {
135			if ((r = sshkey_to_blob(keys[i], &blob, &blen)) != 0) {
136				debug_fr(r, "encode key");
137				continue;
138			}
139			if ((r = sshbuf_put_string(msg, blob, blen)) != 0 ||
140			    (r = sshbuf_put_cstring(msg, labels[i])) != 0)
141				fatal_fr(r, "compose key");
142			free(blob);
143			add_key(keys[i], name, labels[i]);
144			free(labels[i]);
145		}
146	} else if ((r = sshbuf_put_u8(msg, SSH_AGENT_FAILURE)) != 0 ||
147	    (r = sshbuf_put_u32(msg, -nkeys)) != 0)
148		fatal_fr(r, "compose");
149	free(labels);
150	free(keys); /* keys themselves are transferred to pkcs11_keylist */
151	free(pin);
152	free(name);
153	send_msg(msg);
154	sshbuf_free(msg);
155}
156
157static void
158process_del(void)
159{
160	char *name, *pin;
161	struct sshbuf *msg;
162	int r;
163
164	if ((msg = sshbuf_new()) == NULL)
165		fatal_f("sshbuf_new failed");
166	if ((r = sshbuf_get_cstring(iqueue, &name, NULL)) != 0 ||
167	    (r = sshbuf_get_cstring(iqueue, &pin, NULL)) != 0)
168		fatal_fr(r, "parse");
169	del_keys_by_name(name);
170	if ((r = sshbuf_put_u8(msg, pkcs11_del_provider(name) == 0 ?
171	    SSH_AGENT_SUCCESS : SSH_AGENT_FAILURE)) != 0)
172		fatal_fr(r, "compose");
173	free(pin);
174	free(name);
175	send_msg(msg);
176	sshbuf_free(msg);
177}
178
179static void
180process_sign(void)
181{
182	u_char *blob, *data, *signature = NULL;
183	size_t blen, dlen, slen = 0;
184	int r, ok = -1;
185	struct sshkey *key, *found;
186	struct sshbuf *msg;
187
188	/* XXX support SHA2 signature flags */
189	if ((r = sshbuf_get_string(iqueue, &blob, &blen)) != 0 ||
190	    (r = sshbuf_get_string(iqueue, &data, &dlen)) != 0 ||
191	    (r = sshbuf_get_u32(iqueue, NULL)) != 0)
192		fatal_fr(r, "parse");
193
194	if ((r = sshkey_from_blob(blob, blen, &key)) != 0)
195		fatal_fr(r, "decode key");
196	else {
197		if ((found = lookup_key(key)) != NULL) {
198#ifdef WITH_OPENSSL
199			int ret;
200
201			if (key->type == KEY_RSA) {
202				slen = RSA_size(key->rsa);
203				signature = xmalloc(slen);
204				ret = RSA_private_encrypt(dlen, data, signature,
205				    found->rsa, RSA_PKCS1_PADDING);
206				if (ret != -1) {
207					slen = ret;
208					ok = 0;
209				}
210			} else if (key->type == KEY_ECDSA) {
211				u_int xslen = ECDSA_size(key->ecdsa);
212
213				signature = xmalloc(xslen);
214				/* "The parameter type is ignored." */
215				ret = ECDSA_sign(-1, data, dlen, signature,
216				    &xslen, found->ecdsa);
217				if (ret != 0)
218					ok = 0;
219				else
220					error_f("ECDSA_sign returned %d", ret);
221				slen = xslen;
222			} else
223				error_f("don't know how to sign with key "
224				    "type %d", (int)key->type);
225#endif /* WITH_OPENSSL */
226		}
227		sshkey_free(key);
228	}
229	if ((msg = sshbuf_new()) == NULL)
230		fatal_f("sshbuf_new failed");
231	if (ok == 0) {
232		if ((r = sshbuf_put_u8(msg, SSH2_AGENT_SIGN_RESPONSE)) != 0 ||
233		    (r = sshbuf_put_string(msg, signature, slen)) != 0)
234			fatal_fr(r, "compose response");
235	} else {
236		if ((r = sshbuf_put_u8(msg, SSH2_AGENT_FAILURE)) != 0)
237			fatal_fr(r, "compose failure response");
238	}
239	free(data);
240	free(blob);
241	free(signature);
242	send_msg(msg);
243	sshbuf_free(msg);
244}
245
246static void
247process(void)
248{
249	u_int msg_len;
250	u_int buf_len;
251	u_int consumed;
252	u_char type;
253	const u_char *cp;
254	int r;
255
256	buf_len = sshbuf_len(iqueue);
257	if (buf_len < 5)
258		return;		/* Incomplete message. */
259	cp = sshbuf_ptr(iqueue);
260	msg_len = get_u32(cp);
261	if (msg_len > MAX_MSG_LENGTH) {
262		error("bad message len %d", msg_len);
263		cleanup_exit(11);
264	}
265	if (buf_len < msg_len + 4)
266		return;
267	if ((r = sshbuf_consume(iqueue, 4)) != 0 ||
268	    (r = sshbuf_get_u8(iqueue, &type)) != 0)
269		fatal_fr(r, "parse type/len");
270	buf_len -= 4;
271	switch (type) {
272	case SSH_AGENTC_ADD_SMARTCARD_KEY:
273		debug("process_add");
274		process_add();
275		break;
276	case SSH_AGENTC_REMOVE_SMARTCARD_KEY:
277		debug("process_del");
278		process_del();
279		break;
280	case SSH2_AGENTC_SIGN_REQUEST:
281		debug("process_sign");
282		process_sign();
283		break;
284	default:
285		error("Unknown message %d", type);
286		break;
287	}
288	/* discard the remaining bytes from the current packet */
289	if (buf_len < sshbuf_len(iqueue)) {
290		error("iqueue grew unexpectedly");
291		cleanup_exit(255);
292	}
293	consumed = buf_len - sshbuf_len(iqueue);
294	if (msg_len < consumed) {
295		error("msg_len %d < consumed %d", msg_len, consumed);
296		cleanup_exit(255);
297	}
298	if (msg_len > consumed) {
299		if ((r = sshbuf_consume(iqueue, msg_len - consumed)) != 0)
300			fatal_fr(r, "consume");
301	}
302}
303
304void
305cleanup_exit(int i)
306{
307	/* XXX */
308	_exit(i);
309}
310
311
312int
313main(int argc, char **argv)
314{
315	int r, ch, in, out, log_stderr = 0;
316	ssize_t len;
317	SyslogFacility log_facility = SYSLOG_FACILITY_AUTH;
318	LogLevel log_level = SYSLOG_LEVEL_ERROR;
319	char buf[4*4096];
320	extern char *__progname;
321	struct pollfd pfd[2];
322
323	TAILQ_INIT(&pkcs11_keylist);
324
325	log_init(__progname, log_level, log_facility, log_stderr);
326
327	while ((ch = getopt(argc, argv, "v")) != -1) {
328		switch (ch) {
329		case 'v':
330			log_stderr = 1;
331			if (log_level == SYSLOG_LEVEL_ERROR)
332				log_level = SYSLOG_LEVEL_DEBUG1;
333			else if (log_level < SYSLOG_LEVEL_DEBUG3)
334				log_level++;
335			break;
336		default:
337			fprintf(stderr, "usage: %s [-v]\n", __progname);
338			exit(1);
339		}
340	}
341
342	log_init(__progname, log_level, log_facility, log_stderr);
343
344	pkcs11_init(0);
345	in = STDIN_FILENO;
346	out = STDOUT_FILENO;
347
348	if ((iqueue = sshbuf_new()) == NULL)
349		fatal_f("sshbuf_new failed");
350	if ((oqueue = sshbuf_new()) == NULL)
351		fatal_f("sshbuf_new failed");
352
353	while (1) {
354		memset(pfd, 0, sizeof(pfd));
355		pfd[0].fd = in;
356		pfd[1].fd = out;
357
358		/*
359		 * Ensure that we can read a full buffer and handle
360		 * the worst-case length packet it can generate,
361		 * otherwise apply backpressure by stopping reads.
362		 */
363		if ((r = sshbuf_check_reserve(iqueue, sizeof(buf))) == 0 &&
364		    (r = sshbuf_check_reserve(oqueue, MAX_MSG_LENGTH)) == 0)
365			pfd[0].events = POLLIN;
366		else if (r != SSH_ERR_NO_BUFFER_SPACE)
367			fatal_fr(r, "reserve");
368
369		if (sshbuf_len(oqueue) > 0)
370			pfd[1].events = POLLOUT;
371
372		if ((r = poll(pfd, 2, -1 /* INFTIM */)) <= 0) {
373			if (r == 0 || errno == EINTR)
374				continue;
375			fatal("poll: %s", strerror(errno));
376		}
377
378		/* copy stdin to iqueue */
379		if ((pfd[0].revents & (POLLIN|POLLHUP|POLLERR)) != 0) {
380			len = read(in, buf, sizeof buf);
381			if (len == 0) {
382				debug("read eof");
383				cleanup_exit(0);
384			} else if (len < 0) {
385				error("read: %s", strerror(errno));
386				cleanup_exit(1);
387			} else if ((r = sshbuf_put(iqueue, buf, len)) != 0)
388				fatal_fr(r, "sshbuf_put");
389		}
390		/* send oqueue to stdout */
391		if ((pfd[1].revents & (POLLOUT|POLLHUP)) != 0) {
392			len = write(out, sshbuf_ptr(oqueue),
393			    sshbuf_len(oqueue));
394			if (len < 0) {
395				error("write: %s", strerror(errno));
396				cleanup_exit(1);
397			} else if ((r = sshbuf_consume(oqueue, len)) != 0)
398				fatal_fr(r, "consume");
399		}
400
401		/*
402		 * Process requests from client if we can fit the results
403		 * into the output buffer, otherwise stop processing input
404		 * and let the output queue drain.
405		 */
406		if ((r = sshbuf_check_reserve(oqueue, MAX_MSG_LENGTH)) == 0)
407			process();
408		else if (r != SSH_ERR_NO_BUFFER_SPACE)
409			fatal_fr(r, "reserve");
410	}
411}
412
413#else /* WITH_OPENSSL */
414void
415cleanup_exit(int i)
416{
417	_exit(i);
418}
419
420int
421main(int argc, char **argv)
422{
423	fprintf(stderr, "PKCS#11 code is not enabled\n");
424	return 1;
425}
426#endif /* WITH_OPENSSL */
427