ssh-agent.c revision 1.24
1/*	$NetBSD: ssh-agent.c,v 1.24 2018/08/26 07:46:36 christos Exp $	*/
2/* $OpenBSD: ssh-agent.c,v 1.231 2018/05/11 03:38:51 djm Exp $ */
3
4/*
5 * Author: Tatu Ylonen <ylo@cs.hut.fi>
6 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
7 *                    All rights reserved
8 * The authentication agent program.
9 *
10 * As far as I am concerned, the code I have written for this software
11 * can be used freely for any purpose.  Any derived versions of this
12 * software must be clearly marked as such, and if the derived work is
13 * incompatible with the protocol description in the RFC file, it must be
14 * called by a name other than "ssh" or "Secure Shell".
15 *
16 * Copyright (c) 2000, 2001 Markus Friedl.  All rights reserved.
17 *
18 * Redistribution and use in source and binary forms, with or without
19 * modification, are permitted provided that the following conditions
20 * are met:
21 * 1. Redistributions of source code must retain the above copyright
22 *    notice, this list of conditions and the following disclaimer.
23 * 2. Redistributions in binary form must reproduce the above copyright
24 *    notice, this list of conditions and the following disclaimer in the
25 *    documentation and/or other materials provided with the distribution.
26 *
27 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
28 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
29 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
30 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
31 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
32 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
33 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
34 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
35 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
36 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
37 */
38
39#include "includes.h"
40__RCSID("$NetBSD: ssh-agent.c,v 1.24 2018/08/26 07:46:36 christos Exp $");
41
42#include <sys/param.h>	/* MIN MAX */
43#include <sys/types.h>
44#include <sys/time.h>
45#include <sys/queue.h>
46#include <sys/resource.h>
47#include <sys/socket.h>
48#include <sys/stat.h>
49#include <sys/un.h>
50
51#ifdef WITH_OPENSSL
52#include <openssl/evp.h>
53#endif
54
55#include <errno.h>
56#include <fcntl.h>
57#include <paths.h>
58#include <poll.h>
59#include <signal.h>
60#include <stdlib.h>
61#include <stdio.h>
62#include <string.h>
63#include <limits.h>
64#include <time.h>
65#include <unistd.h>
66#include <util.h>
67
68#include "xmalloc.h"
69#include "ssh.h"
70#include "sshbuf.h"
71#include "sshkey.h"
72#include "authfd.h"
73#include "compat.h"
74#include "log.h"
75#include "misc.h"
76#include "getpeereid.h"
77#include "digest.h"
78#include "ssherr.h"
79#include "match.h"
80
81#ifdef ENABLE_PKCS11
82#include "ssh-pkcs11.h"
83#endif
84
85#ifndef DEFAULT_PKCS11_WHITELIST
86# define DEFAULT_PKCS11_WHITELIST "/usr/lib*/*,/usr/pkg/lib*/*"
87#endif
88
89/* Maximum accepted message length */
90#define AGENT_MAX_LEN	(256*1024)
91
92typedef enum {
93	AUTH_UNUSED,
94	AUTH_SOCKET,
95	AUTH_CONNECTION
96} sock_type;
97
98typedef struct {
99	int fd;
100	sock_type type;
101	struct sshbuf *input;
102	struct sshbuf *output;
103	struct sshbuf *request;
104} SocketEntry;
105
106u_int sockets_alloc = 0;
107SocketEntry *sockets = NULL;
108
109typedef struct identity {
110	TAILQ_ENTRY(identity) next;
111	struct sshkey *key;
112	char *comment;
113	char *provider;
114	time_t death;
115	u_int confirm;
116} Identity;
117
118struct idtable {
119	int nentries;
120	TAILQ_HEAD(idqueue, identity) idlist;
121};
122
123/* private key table */
124struct idtable *idtab;
125
126int max_fd = 0;
127
128/* pid of shell == parent of agent */
129pid_t parent_pid = -1;
130time_t parent_alive_interval = 0;
131
132/* pid of process for which cleanup_socket is applicable */
133pid_t cleanup_pid = 0;
134
135/* pathname and directory for AUTH_SOCKET */
136char socket_name[PATH_MAX];
137char socket_dir[PATH_MAX];
138
139/* PKCS#11 path whitelist */
140static char *pkcs11_whitelist;
141
142/* locking */
143#define LOCK_SIZE	32
144#define LOCK_SALT_SIZE	16
145#define LOCK_ROUNDS	1
146int locked = 0;
147u_char lock_pwhash[LOCK_SIZE];
148u_char lock_salt[LOCK_SALT_SIZE];
149
150extern char *__progname;
151
152/* Default lifetime in seconds (0 == forever) */
153static long lifetime = 0;
154
155static int fingerprint_hash = SSH_FP_HASH_DEFAULT;
156
157static void
158close_socket(SocketEntry *e)
159{
160	close(e->fd);
161	e->fd = -1;
162	e->type = AUTH_UNUSED;
163	sshbuf_free(e->input);
164	sshbuf_free(e->output);
165	sshbuf_free(e->request);
166}
167
168static void
169idtab_init(void)
170{
171	idtab = xcalloc(1, sizeof(*idtab));
172	TAILQ_INIT(&idtab->idlist);
173	idtab->nentries = 0;
174}
175
176static void
177free_identity(Identity *id)
178{
179	sshkey_free(id->key);
180	free(id->provider);
181	free(id->comment);
182	free(id);
183}
184
185/* return matching private key for given public key */
186static Identity *
187lookup_identity(struct sshkey *key)
188{
189	Identity *id;
190
191	TAILQ_FOREACH(id, &idtab->idlist, next) {
192		if (sshkey_equal(key, id->key))
193			return (id);
194	}
195	return (NULL);
196}
197
198/* Check confirmation of keysign request */
199static int
200confirm_key(Identity *id)
201{
202	char *p;
203	int ret = -1;
204
205	p = sshkey_fingerprint(id->key, fingerprint_hash, SSH_FP_DEFAULT);
206	if (p != NULL &&
207	    ask_permission("Allow use of key %s?\nKey fingerprint %s.",
208	    id->comment, p))
209		ret = 0;
210	free(p);
211
212	return (ret);
213}
214
215static void
216send_status(SocketEntry *e, int success)
217{
218	int r;
219
220	if ((r = sshbuf_put_u32(e->output, 1)) != 0 ||
221	    (r = sshbuf_put_u8(e->output, success ?
222	    SSH_AGENT_SUCCESS : SSH_AGENT_FAILURE)) != 0)
223		fatal("%s: buffer error: %s", __func__, ssh_err(r));
224}
225
226/* send list of supported public keys to 'client' */
227static void
228process_request_identities(SocketEntry *e)
229{
230	Identity *id;
231	struct sshbuf *msg;
232	int r;
233
234	if ((msg = sshbuf_new()) == NULL)
235		fatal("%s: sshbuf_new failed", __func__);
236	if ((r = sshbuf_put_u8(msg, SSH2_AGENT_IDENTITIES_ANSWER)) != 0 ||
237	    (r = sshbuf_put_u32(msg, idtab->nentries)) != 0)
238		fatal("%s: buffer error: %s", __func__, ssh_err(r));
239	TAILQ_FOREACH(id, &idtab->idlist, next) {
240		if ((r = sshkey_puts_opts(id->key, msg, SSHKEY_SERIALIZE_INFO))
241		     != 0 ||
242		    (r = sshbuf_put_cstring(msg, id->comment)) != 0) {
243			error("%s: put key/comment: %s", __func__,
244			    ssh_err(r));
245			continue;
246		}
247	}
248	if ((r = sshbuf_put_stringb(e->output, msg)) != 0)
249		fatal("%s: buffer error: %s", __func__, ssh_err(r));
250	sshbuf_free(msg);
251}
252
253
254static const char *
255agent_decode_alg(struct sshkey *key, u_int flags)
256{
257	if (key->type == KEY_RSA) {
258		if (flags & SSH_AGENT_RSA_SHA2_256)
259			return "rsa-sha2-256";
260		else if (flags & SSH_AGENT_RSA_SHA2_512)
261			return "rsa-sha2-512";
262	}
263	return NULL;
264}
265
266/* ssh2 only */
267static void
268process_sign_request2(SocketEntry *e)
269{
270	const u_char *data;
271	u_char *signature = NULL;
272	size_t dlen, slen = 0;
273	u_int compat = 0, flags;
274	int r, ok = -1;
275	struct sshbuf *msg;
276	struct sshkey *key = NULL;
277	struct identity *id;
278
279	if ((msg = sshbuf_new()) == NULL)
280		fatal("%s: sshbuf_new failed", __func__);
281	if ((r = sshkey_froms(e->request, &key)) != 0 ||
282	    (r = sshbuf_get_string_direct(e->request, &data, &dlen)) != 0 ||
283	    (r = sshbuf_get_u32(e->request, &flags)) != 0) {
284		error("%s: couldn't parse request: %s", __func__, ssh_err(r));
285		goto send;
286	}
287
288	if ((id = lookup_identity(key)) == NULL) {
289		verbose("%s: %s key not found", __func__, sshkey_type(key));
290		goto send;
291	}
292	if (id->confirm && confirm_key(id) != 0) {
293		verbose("%s: user refused key", __func__);
294		goto send;
295	}
296	if ((r = sshkey_sign(id->key, &signature, &slen,
297	    data, dlen, agent_decode_alg(key, flags), compat)) != 0) {
298		error("%s: sshkey_sign: %s", __func__, ssh_err(r));
299		goto send;
300	}
301	/* Success */
302	ok = 0;
303 send:
304	sshkey_free(key);
305	if (ok == 0) {
306		if ((r = sshbuf_put_u8(msg, SSH2_AGENT_SIGN_RESPONSE)) != 0 ||
307		    (r = sshbuf_put_string(msg, signature, slen)) != 0)
308			fatal("%s: buffer error: %s", __func__, ssh_err(r));
309	} else if ((r = sshbuf_put_u8(msg, SSH_AGENT_FAILURE)) != 0)
310		fatal("%s: buffer error: %s", __func__, ssh_err(r));
311
312	if ((r = sshbuf_put_stringb(e->output, msg)) != 0)
313		fatal("%s: buffer error: %s", __func__, ssh_err(r));
314
315	sshbuf_free(msg);
316	free(signature);
317}
318
319/* shared */
320static void
321process_remove_identity(SocketEntry *e)
322{
323	int r, success = 0;
324	struct sshkey *key = NULL;
325	Identity *id;
326
327	if ((r = sshkey_froms(e->request, &key)) != 0) {
328		error("%s: get key: %s", __func__, ssh_err(r));
329		goto done;
330	}
331	if ((id = lookup_identity(key)) == NULL) {
332		debug("%s: key not found", __func__);
333		goto done;
334	}
335	/* We have this key, free it. */
336	if (idtab->nentries < 1)
337		fatal("%s: internal error: nentries %d",
338		    __func__, idtab->nentries);
339	TAILQ_REMOVE(&idtab->idlist, id, next);
340	free_identity(id);
341	idtab->nentries--;
342	sshkey_free(key);
343	success = 1;
344 done:
345	send_status(e, success);
346}
347
348static void
349process_remove_all_identities(SocketEntry *e)
350{
351	Identity *id;
352
353	/* Loop over all identities and clear the keys. */
354	for (id = TAILQ_FIRST(&idtab->idlist); id;
355	    id = TAILQ_FIRST(&idtab->idlist)) {
356		TAILQ_REMOVE(&idtab->idlist, id, next);
357		free_identity(id);
358	}
359
360	/* Mark that there are no identities. */
361	idtab->nentries = 0;
362
363	/* Send success. */
364	send_status(e, 1);
365}
366
367/* removes expired keys and returns number of seconds until the next expiry */
368static time_t
369reaper(void)
370{
371	time_t deadline = 0, now = monotime();
372	Identity *id, *nxt;
373
374	for (id = TAILQ_FIRST(&idtab->idlist); id; id = nxt) {
375		nxt = TAILQ_NEXT(id, next);
376		if (id->death == 0)
377			continue;
378		if (now >= id->death) {
379			debug("expiring key '%s'", id->comment);
380			TAILQ_REMOVE(&idtab->idlist, id, next);
381			free_identity(id);
382			idtab->nentries--;
383		} else
384			deadline = (deadline == 0) ? id->death :
385			    MINIMUM(deadline, id->death);
386	}
387	if (deadline == 0 || deadline <= now)
388		return 0;
389	else
390		return (deadline - now);
391}
392
393static void
394process_add_identity(SocketEntry *e)
395{
396	Identity *id;
397	int success = 0, confirm = 0;
398	u_int seconds, maxsign;
399	char *comment = NULL;
400	time_t death = 0;
401	struct sshkey *k = NULL;
402	u_char ctype;
403	int r = SSH_ERR_INTERNAL_ERROR;
404
405	if ((r = sshkey_private_deserialize(e->request, &k)) != 0 ||
406	    k == NULL ||
407	    (r = sshbuf_get_cstring(e->request, &comment, NULL)) != 0) {
408		error("%s: decode private key: %s", __func__, ssh_err(r));
409		goto err;
410	}
411
412	while (sshbuf_len(e->request)) {
413		if ((r = sshbuf_get_u8(e->request, &ctype)) != 0) {
414			error("%s: buffer error: %s", __func__, ssh_err(r));
415			goto err;
416		}
417		switch (ctype) {
418		case SSH_AGENT_CONSTRAIN_LIFETIME:
419			if ((r = sshbuf_get_u32(e->request, &seconds)) != 0) {
420				error("%s: bad lifetime constraint: %s",
421				    __func__, ssh_err(r));
422				goto err;
423			}
424			death = monotime() + seconds;
425			break;
426		case SSH_AGENT_CONSTRAIN_CONFIRM:
427			confirm = 1;
428			break;
429		case SSH_AGENT_CONSTRAIN_MAXSIGN:
430			if ((r = sshbuf_get_u32(e->request, &maxsign)) != 0) {
431				error("%s: bad maxsign constraint: %s",
432				    __func__, ssh_err(r));
433				goto err;
434			}
435			if ((r = sshkey_enable_maxsign(k, maxsign)) != 0) {
436				error("%s: cannot enable maxsign: %s",
437				    __func__, ssh_err(r));
438				goto err;
439			}
440			break;
441		default:
442			error("%s: Unknown constraint %d", __func__, ctype);
443 err:
444			sshbuf_reset(e->request);
445			free(comment);
446			sshkey_free(k);
447			goto send;
448		}
449	}
450
451	success = 1;
452	if (lifetime && !death)
453		death = monotime() + lifetime;
454	if ((id = lookup_identity(k)) == NULL) {
455		id = xcalloc(1, sizeof(Identity));
456		TAILQ_INSERT_TAIL(&idtab->idlist, id, next);
457		/* Increment the number of identities. */
458		idtab->nentries++;
459	} else {
460		/* key state might have been updated */
461		sshkey_free(id->key);
462		free(id->comment);
463	}
464	id->key = k;
465	id->comment = comment;
466	id->death = death;
467	id->confirm = confirm;
468send:
469	send_status(e, success);
470}
471
472/* XXX todo: encrypt sensitive data with passphrase */
473static void
474process_lock_agent(SocketEntry *e, int lock)
475{
476	int r, success = 0, delay;
477	char *passwd;
478	u_char passwdhash[LOCK_SIZE];
479	static u_int fail_count = 0;
480	size_t pwlen;
481
482	/*
483	 * This is deliberately fatal: the user has requested that we lock,
484	 * but we can't parse their request properly. The only safe thing to
485	 * do is abort.
486	 */
487	if ((r = sshbuf_get_cstring(e->request, &passwd, &pwlen)) != 0)
488		fatal("%s: buffer error: %s", __func__, ssh_err(r));
489	if (pwlen == 0) {
490		debug("empty password not supported");
491	} else if (locked && !lock) {
492		if (bcrypt_pbkdf(passwd, pwlen, (uint8_t *)lock_salt, sizeof(lock_salt),
493		    (uint8_t *)passwdhash, sizeof(passwdhash), LOCK_ROUNDS) < 0)
494			fatal("bcrypt_pbkdf");
495		if (timingsafe_bcmp(passwdhash, lock_pwhash, LOCK_SIZE) == 0) {
496			debug("agent unlocked");
497			locked = 0;
498			fail_count = 0;
499			explicit_bzero(lock_pwhash, sizeof(lock_pwhash));
500			success = 1;
501		} else {
502			/* delay in 0.1s increments up to 10s */
503			if (fail_count < 100)
504				fail_count++;
505			delay = 100000 * fail_count;
506			debug("unlock failed, delaying %0.1lf seconds",
507			    (double)delay/1000000);
508			usleep(delay);
509		}
510		explicit_bzero(passwdhash, sizeof(passwdhash));
511	} else if (!locked && lock) {
512		debug("agent locked");
513		locked = 1;
514		arc4random_buf(lock_salt, sizeof(lock_salt));
515		if (bcrypt_pbkdf(passwd, pwlen, lock_salt, sizeof(lock_salt),
516		    lock_pwhash, sizeof(lock_pwhash), LOCK_ROUNDS) < 0)
517			fatal("bcrypt_pbkdf");
518		success = 1;
519	}
520	explicit_bzero(passwd, pwlen);
521	free(passwd);
522	send_status(e, success);
523}
524
525static void
526no_identities(SocketEntry *e)
527{
528	struct sshbuf *msg;
529	int r;
530
531	if ((msg = sshbuf_new()) == NULL)
532		fatal("%s: sshbuf_new failed", __func__);
533	if ((r = sshbuf_put_u8(msg, SSH2_AGENT_IDENTITIES_ANSWER)) != 0 ||
534	    (r = sshbuf_put_u32(msg, 0)) != 0 ||
535	    (r = sshbuf_put_stringb(e->output, msg)) != 0)
536		fatal("%s: buffer error: %s", __func__, ssh_err(r));
537	sshbuf_free(msg);
538}
539
540#ifdef ENABLE_PKCS11
541static void
542process_add_smartcard_key(SocketEntry *e)
543{
544	char *provider = NULL, *pin = NULL, canonical_provider[PATH_MAX];
545	int r, i, count = 0, success = 0, confirm = 0;
546	u_int seconds;
547	time_t death = 0;
548	u_char type;
549	struct sshkey **keys = NULL, *k;
550	Identity *id;
551
552	if ((r = sshbuf_get_cstring(e->request, &provider, NULL)) != 0 ||
553	    (r = sshbuf_get_cstring(e->request, &pin, NULL)) != 0) {
554		error("%s: buffer error: %s", __func__, ssh_err(r));
555		goto send;
556	}
557
558	while (sshbuf_len(e->request)) {
559		if ((r = sshbuf_get_u8(e->request, &type)) != 0) {
560			error("%s: buffer error: %s", __func__, ssh_err(r));
561			goto send;
562		}
563		switch (type) {
564		case SSH_AGENT_CONSTRAIN_LIFETIME:
565			if ((r = sshbuf_get_u32(e->request, &seconds)) != 0) {
566				error("%s: buffer error: %s",
567				    __func__, ssh_err(r));
568				goto send;
569			}
570			death = monotime() + seconds;
571			break;
572		case SSH_AGENT_CONSTRAIN_CONFIRM:
573			confirm = 1;
574			break;
575		default:
576			error("%s: Unknown constraint type %d", __func__, type);
577			goto send;
578		}
579	}
580	if (realpath(provider, canonical_provider) == NULL) {
581		verbose("failed PKCS#11 add of \"%.100s\": realpath: %s",
582		    provider, strerror(errno));
583		goto send;
584	}
585	if (match_pattern_list(canonical_provider, pkcs11_whitelist, 0) != 1) {
586		verbose("refusing PKCS#11 add of \"%.100s\": "
587		    "provider not whitelisted", canonical_provider);
588		goto send;
589	}
590	debug("%s: add %.100s", __func__, canonical_provider);
591	if (lifetime && !death)
592		death = monotime() + lifetime;
593
594	count = pkcs11_add_provider(canonical_provider, pin, &keys);
595	for (i = 0; i < count; i++) {
596		k = keys[i];
597		if (lookup_identity(k) == NULL) {
598			id = xcalloc(1, sizeof(Identity));
599			id->key = k;
600			id->provider = xstrdup(canonical_provider);
601			id->comment = xstrdup(canonical_provider); /* XXX */
602			id->death = death;
603			id->confirm = confirm;
604			TAILQ_INSERT_TAIL(&idtab->idlist, id, next);
605			idtab->nentries++;
606			success = 1;
607		} else {
608			sshkey_free(k);
609		}
610		keys[i] = NULL;
611	}
612send:
613	free(pin);
614	free(provider);
615	free(keys);
616	send_status(e, success);
617}
618
619static void
620process_remove_smartcard_key(SocketEntry *e)
621{
622	char *provider = NULL, *pin = NULL, canonical_provider[PATH_MAX];
623	int r, success = 0;
624	Identity *id, *nxt;
625
626	if ((r = sshbuf_get_cstring(e->request, &provider, NULL)) != 0 ||
627	    (r = sshbuf_get_cstring(e->request, &pin, NULL)) != 0) {
628		error("%s: buffer error: %s", __func__, ssh_err(r));
629		goto send;
630	}
631	free(pin);
632
633	if (realpath(provider, canonical_provider) == NULL) {
634		verbose("failed PKCS#11 add of \"%.100s\": realpath: %s",
635		    provider, strerror(errno));
636		goto send;
637	}
638
639	debug("%s: remove %.100s", __func__, canonical_provider);
640	for (id = TAILQ_FIRST(&idtab->idlist); id; id = nxt) {
641		nxt = TAILQ_NEXT(id, next);
642		/* Skip file--based keys */
643		if (id->provider == NULL)
644			continue;
645		if (!strcmp(canonical_provider, id->provider)) {
646			TAILQ_REMOVE(&idtab->idlist, id, next);
647			free_identity(id);
648			idtab->nentries--;
649		}
650	}
651	if (pkcs11_del_provider(canonical_provider) == 0)
652		success = 1;
653	else
654		error("%s: pkcs11_del_provider failed", __func__);
655send:
656	free(provider);
657	send_status(e, success);
658}
659#endif /* ENABLE_PKCS11 */
660
661/* dispatch incoming messages */
662
663static int
664process_message(u_int socknum)
665{
666	u_int msg_len;
667	u_char type;
668	const u_char *cp;
669	int r;
670	SocketEntry *e;
671
672	if (socknum >= sockets_alloc) {
673		fatal("%s: socket number %u >= allocated %u",
674		    __func__, socknum, sockets_alloc);
675	}
676	e = &sockets[socknum];
677
678	if (sshbuf_len(e->input) < 5)
679		return 0;		/* Incomplete message header. */
680	cp = sshbuf_ptr(e->input);
681	msg_len = PEEK_U32(cp);
682	if (msg_len > AGENT_MAX_LEN) {
683		debug("%s: socket %u (fd=%d) message too long %u > %u",
684		    __func__, socknum, e->fd, msg_len, AGENT_MAX_LEN);
685		return -1;
686	}
687	if (sshbuf_len(e->input) < msg_len + 4)
688		return 0;		/* Incomplete message body. */
689
690	/* move the current input to e->request */
691	sshbuf_reset(e->request);
692	if ((r = sshbuf_get_stringb(e->input, e->request)) != 0 ||
693	    (r = sshbuf_get_u8(e->request, &type)) != 0) {
694		if (r == SSH_ERR_MESSAGE_INCOMPLETE ||
695		    r == SSH_ERR_STRING_TOO_LARGE) {
696			debug("%s: buffer error: %s", __func__, ssh_err(r));
697			return -1;
698		}
699		fatal("%s: buffer error: %s", __func__, ssh_err(r));
700	}
701
702	debug("%s: socket %u (fd=%d) type %d", __func__, socknum, e->fd, type);
703
704	/* check whether agent is locked */
705	if (locked && type != SSH_AGENTC_UNLOCK) {
706		sshbuf_reset(e->request);
707		switch (type) {
708		case SSH2_AGENTC_REQUEST_IDENTITIES:
709			/* send empty lists */
710			no_identities(e);
711			break;
712		default:
713			/* send a fail message for all other request types */
714			send_status(e, 0);
715		}
716		return 0;
717	}
718
719	switch (type) {
720	case SSH_AGENTC_LOCK:
721	case SSH_AGENTC_UNLOCK:
722		process_lock_agent(e, type == SSH_AGENTC_LOCK);
723		break;
724	case SSH_AGENTC_REMOVE_ALL_RSA_IDENTITIES:
725		process_remove_all_identities(e); /* safe for !WITH_SSH1 */
726		break;
727	/* ssh2 */
728	case SSH2_AGENTC_SIGN_REQUEST:
729		process_sign_request2(e);
730		break;
731	case SSH2_AGENTC_REQUEST_IDENTITIES:
732		process_request_identities(e);
733		break;
734	case SSH2_AGENTC_ADD_IDENTITY:
735	case SSH2_AGENTC_ADD_ID_CONSTRAINED:
736		process_add_identity(e);
737		break;
738	case SSH2_AGENTC_REMOVE_IDENTITY:
739		process_remove_identity(e);
740		break;
741	case SSH2_AGENTC_REMOVE_ALL_IDENTITIES:
742		process_remove_all_identities(e);
743		break;
744#ifdef ENABLE_PKCS11
745	case SSH_AGENTC_ADD_SMARTCARD_KEY:
746	case SSH_AGENTC_ADD_SMARTCARD_KEY_CONSTRAINED:
747		process_add_smartcard_key(e);
748		break;
749	case SSH_AGENTC_REMOVE_SMARTCARD_KEY:
750		process_remove_smartcard_key(e);
751		break;
752#endif /* ENABLE_PKCS11 */
753	default:
754		/* Unknown message.  Respond with failure. */
755		error("Unknown message %d", type);
756		sshbuf_reset(e->request);
757		send_status(e, 0);
758		break;
759	}
760	return 0;
761}
762
763static void
764new_socket(sock_type type, int fd)
765{
766	u_int i, old_alloc, new_alloc;
767
768	set_nonblock(fd);
769
770	if (fd > max_fd)
771		max_fd = fd;
772
773	for (i = 0; i < sockets_alloc; i++)
774		if (sockets[i].type == AUTH_UNUSED) {
775			sockets[i].fd = fd;
776			if ((sockets[i].input = sshbuf_new()) == NULL)
777				fatal("%s: sshbuf_new failed", __func__);
778			if ((sockets[i].output = sshbuf_new()) == NULL)
779				fatal("%s: sshbuf_new failed", __func__);
780			if ((sockets[i].request = sshbuf_new()) == NULL)
781				fatal("%s: sshbuf_new failed", __func__);
782			sockets[i].type = type;
783			return;
784		}
785	old_alloc = sockets_alloc;
786	new_alloc = sockets_alloc + 10;
787	sockets = xreallocarray(sockets, new_alloc, sizeof(sockets[0]));
788	for (i = old_alloc; i < new_alloc; i++)
789		sockets[i].type = AUTH_UNUSED;
790	sockets_alloc = new_alloc;
791	sockets[old_alloc].fd = fd;
792	if ((sockets[old_alloc].input = sshbuf_new()) == NULL)
793		fatal("%s: sshbuf_new failed", __func__);
794	if ((sockets[old_alloc].output = sshbuf_new()) == NULL)
795		fatal("%s: sshbuf_new failed", __func__);
796	if ((sockets[old_alloc].request = sshbuf_new()) == NULL)
797		fatal("%s: sshbuf_new failed", __func__);
798	sockets[old_alloc].type = type;
799}
800
801static int
802handle_socket_read(u_int socknum)
803{
804	struct sockaddr_un sunaddr;
805	socklen_t slen;
806	uid_t euid;
807	gid_t egid;
808	int fd;
809
810	slen = sizeof(sunaddr);
811	fd = accept(sockets[socknum].fd, (struct sockaddr *)&sunaddr, &slen);
812	if (fd < 0) {
813		error("accept from AUTH_SOCKET: %s", strerror(errno));
814		return -1;
815	}
816	if (getpeereid(fd, &euid, &egid) < 0) {
817		error("getpeereid %d failed: %s", fd, strerror(errno));
818		close(fd);
819		return -1;
820	}
821	if ((euid != 0) && (getuid() != euid)) {
822		error("uid mismatch: peer euid %u != uid %u",
823		    (u_int) euid, (u_int) getuid());
824		close(fd);
825		return -1;
826	}
827	new_socket(AUTH_CONNECTION, fd);
828	return 0;
829}
830
831static int
832handle_conn_read(u_int socknum)
833{
834	char buf[1024];
835	ssize_t len;
836	int r;
837
838	if ((len = read(sockets[socknum].fd, buf, sizeof(buf))) <= 0) {
839		if (len == -1) {
840			if (errno == EAGAIN || errno == EINTR)
841				return 0;
842			error("%s: read error on socket %u (fd %d): %s",
843			    __func__, socknum, sockets[socknum].fd,
844			    strerror(errno));
845		}
846		return -1;
847	}
848	if ((r = sshbuf_put(sockets[socknum].input, buf, len)) != 0)
849		fatal("%s: buffer error: %s", __func__, ssh_err(r));
850	explicit_bzero(buf, sizeof(buf));
851	process_message(socknum);
852	return 0;
853}
854
855static int
856handle_conn_write(u_int socknum)
857{
858	ssize_t len;
859	int r;
860
861	if (sshbuf_len(sockets[socknum].output) == 0)
862		return 0; /* shouldn't happen */
863	if ((len = write(sockets[socknum].fd,
864	    sshbuf_ptr(sockets[socknum].output),
865	    sshbuf_len(sockets[socknum].output))) <= 0) {
866		if (len == -1) {
867			if (errno == EAGAIN || errno == EINTR)
868				return 0;
869			error("%s: read error on socket %u (fd %d): %s",
870			    __func__, socknum, sockets[socknum].fd,
871			    strerror(errno));
872		}
873		return -1;
874	}
875	if ((r = sshbuf_consume(sockets[socknum].output, len)) != 0)
876		fatal("%s: buffer error: %s", __func__, ssh_err(r));
877	return 0;
878}
879
880static void
881after_poll(struct pollfd *pfd, size_t npfd, u_int maxfds)
882{
883	size_t i;
884	u_int socknum, activefds = npfd;
885
886	for (i = 0; i < npfd; i++) {
887		if (pfd[i].revents == 0)
888			continue;
889		/* Find sockets entry */
890		for (socknum = 0; socknum < sockets_alloc; socknum++) {
891			if (sockets[socknum].type != AUTH_SOCKET &&
892			    sockets[socknum].type != AUTH_CONNECTION)
893				continue;
894			if (pfd[i].fd == sockets[socknum].fd)
895				break;
896		}
897		if (socknum >= sockets_alloc) {
898			error("%s: no socket for fd %d", __func__, pfd[i].fd);
899			continue;
900		}
901		/* Process events */
902		switch (sockets[socknum].type) {
903		case AUTH_SOCKET:
904			if ((pfd[i].revents & (POLLIN|POLLERR)) == 0)
905				break;
906			if (npfd > maxfds) {
907				debug3("out of fds (active %u >= limit %u); "
908				    "skipping accept", activefds, maxfds);
909				break;
910			}
911			if (handle_socket_read(socknum) == 0)
912				activefds++;
913			break;
914		case AUTH_CONNECTION:
915			if ((pfd[i].revents & (POLLIN|POLLERR)) != 0 &&
916			    handle_conn_read(socknum) != 0) {
917				goto close_sock;
918			}
919			if ((pfd[i].revents & (POLLOUT|POLLHUP)) != 0 &&
920			    handle_conn_write(socknum) != 0) {
921 close_sock:
922				if (activefds == 0)
923					fatal("activefds == 0 at close_sock");
924				close_socket(&sockets[socknum]);
925				activefds--;
926				break;
927			}
928			break;
929		default:
930			break;
931		}
932	}
933}
934
935static int
936prepare_poll(struct pollfd **pfdp, size_t *npfdp, int *timeoutp, u_int maxfds)
937{
938	struct pollfd *pfd = *pfdp;
939	size_t i, j, npfd = 0;
940	time_t deadline;
941
942	/* Count active sockets */
943	for (i = 0; i < sockets_alloc; i++) {
944		switch (sockets[i].type) {
945		case AUTH_SOCKET:
946		case AUTH_CONNECTION:
947			npfd++;
948			break;
949		case AUTH_UNUSED:
950			break;
951		default:
952			fatal("Unknown socket type %d", sockets[i].type);
953			break;
954		}
955	}
956	if (npfd != *npfdp &&
957	    (pfd = recallocarray(pfd, *npfdp, npfd, sizeof(*pfd))) == NULL)
958		fatal("%s: recallocarray failed", __func__);
959	*pfdp = pfd;
960	*npfdp = npfd;
961
962	for (i = j = 0; i < sockets_alloc; i++) {
963		switch (sockets[i].type) {
964		case AUTH_SOCKET:
965			if (npfd > maxfds) {
966				debug3("out of fds (active %zu >= limit %u); "
967				    "skipping arming listener", npfd, maxfds);
968				break;
969			}
970			pfd[j].fd = sockets[i].fd;
971			pfd[j].revents = 0;
972			pfd[j].events = POLLIN;
973			j++;
974			break;
975		case AUTH_CONNECTION:
976			pfd[j].fd = sockets[i].fd;
977			pfd[j].revents = 0;
978			/* XXX backoff when input buffer full */
979			pfd[j].events = POLLIN;
980			if (sshbuf_len(sockets[i].output) > 0)
981				pfd[j].events |= POLLOUT;
982			j++;
983			break;
984		default:
985			break;
986		}
987	}
988	deadline = reaper();
989	if (parent_alive_interval != 0)
990		deadline = (deadline == 0) ? parent_alive_interval :
991		    MINIMUM(deadline, parent_alive_interval);
992	if (deadline == 0) {
993		*timeoutp = -1; /* INFTIM */
994	} else {
995		if (deadline > INT_MAX / 1000)
996			*timeoutp = INT_MAX / 1000;
997		else
998			*timeoutp = deadline * 1000;
999	}
1000	return (1);
1001}
1002
1003static void
1004cleanup_socket(void)
1005{
1006	if (cleanup_pid != 0 && getpid() != cleanup_pid)
1007		return;
1008	debug("%s: cleanup", __func__);
1009	if (socket_name[0])
1010		unlink(socket_name);
1011	if (socket_dir[0])
1012		rmdir(socket_dir);
1013}
1014
1015void
1016cleanup_exit(int i)
1017{
1018	cleanup_socket();
1019	_exit(i);
1020}
1021
1022/*ARGSUSED*/
1023__dead static void
1024cleanup_handler(int sig)
1025{
1026	cleanup_socket();
1027#ifdef ENABLE_PKCS11
1028	pkcs11_terminate();
1029#endif
1030	_exit(2);
1031}
1032
1033static void
1034check_parent_exists(void)
1035{
1036	/*
1037	 * If our parent has exited then getppid() will return (pid_t)1,
1038	 * so testing for that should be safe.
1039	 */
1040	if (parent_pid != -1 && getppid() != parent_pid) {
1041		/* printf("Parent has died - Authentication agent exiting.\n"); */
1042		cleanup_socket();
1043		_exit(2);
1044	}
1045}
1046
1047__dead static void
1048usage(void)
1049{
1050	fprintf(stderr,
1051	    "usage: ssh-agent [-c | -s] [-Dd] [-a bind_address] [-E fingerprint_hash]\n"
1052	    "                 [-P pkcs11_whitelist] [-t life] [command [arg ...]]\n"
1053	    "       ssh-agent [-c | -s] -k\n");
1054	exit(1);
1055}
1056
1057static void
1058csh_setenv(const char *name, const char *value)
1059{
1060	printf("setenv %s %s;\n", name, value);
1061}
1062
1063static void
1064csh_unsetenv(const char *name)
1065{
1066	printf("unsetenv %s;\n", name);
1067}
1068
1069static void
1070sh_setenv(const char *name, const char *value)
1071{
1072	printf("%s=%s; export %s;\n", name, value, name);
1073}
1074
1075static void
1076sh_unsetenv(const char *name)
1077{
1078	printf("unset %s;\n", name);
1079}
1080int
1081main(int ac, char **av)
1082{
1083	int c_flag = 0, d_flag = 0, D_flag = 0, k_flag = 0, s_flag = 0;
1084	int sock, fd, ch, result, saved_errno;
1085	char *shell, *pidstr, *agentsocket = NULL;
1086	struct rlimit rlim;
1087	void (*f_setenv)(const char *, const char *);
1088	void (*f_unsetenv)(const char *);
1089	extern int optind;
1090	extern char *optarg;
1091	pid_t pid;
1092	char pidstrbuf[1 + 3 * sizeof pid];
1093	size_t len;
1094	mode_t prev_mask;
1095	int timeout = -1; /* INFTIM */
1096	struct pollfd *pfd = NULL;
1097	size_t npfd = 0;
1098	u_int maxfds;
1099
1100	ssh_malloc_init();	/* must be called before any mallocs */
1101	/* Ensure that fds 0, 1 and 2 are open or directed to /dev/null */
1102	sanitise_stdfd();
1103
1104	/* drop */
1105	setegid(getgid());
1106	setgid(getgid());
1107
1108	if (getrlimit(RLIMIT_NOFILE, &rlim) == -1)
1109		fatal("%s: getrlimit: %s", __progname, strerror(errno));
1110
1111#ifdef WITH_OPENSSL
1112	OpenSSL_add_all_algorithms();
1113#endif
1114
1115	while ((ch = getopt(ac, av, "cDdksE:a:P:t:")) != -1) {
1116		switch (ch) {
1117		case 'E':
1118			fingerprint_hash = ssh_digest_alg_by_name(optarg);
1119			if (fingerprint_hash == -1)
1120				fatal("Invalid hash algorithm \"%s\"", optarg);
1121			break;
1122		case 'c':
1123			if (s_flag)
1124				usage();
1125			c_flag++;
1126			break;
1127		case 'k':
1128			k_flag++;
1129			break;
1130		case 'P':
1131			if (pkcs11_whitelist != NULL)
1132				fatal("-P option already specified");
1133			pkcs11_whitelist = xstrdup(optarg);
1134			break;
1135		case 's':
1136			if (c_flag)
1137				usage();
1138			s_flag++;
1139			break;
1140		case 'd':
1141			if (d_flag || D_flag)
1142				usage();
1143			d_flag++;
1144			break;
1145		case 'D':
1146			if (d_flag || D_flag)
1147				usage();
1148			D_flag++;
1149			break;
1150		case 'a':
1151			agentsocket = optarg;
1152			break;
1153		case 't':
1154			if ((lifetime = convtime(optarg)) == -1) {
1155				fprintf(stderr, "Invalid lifetime\n");
1156				usage();
1157			}
1158			break;
1159		default:
1160			usage();
1161		}
1162	}
1163	ac -= optind;
1164	av += optind;
1165
1166	if (ac > 0 && (c_flag || k_flag || s_flag || d_flag || D_flag))
1167		usage();
1168
1169	if (pkcs11_whitelist == NULL)
1170		pkcs11_whitelist = xstrdup(DEFAULT_PKCS11_WHITELIST);
1171
1172	if (ac == 0 && !c_flag && !s_flag) {
1173		shell = getenv("SHELL");
1174		if (shell != NULL && (len = strlen(shell)) > 2 &&
1175		    strncmp(shell + len - 3, "csh", 3) == 0)
1176			c_flag = 1;
1177	}
1178	if (c_flag) {
1179		f_setenv = csh_setenv;
1180		f_unsetenv = csh_unsetenv;
1181	} else {
1182		f_setenv = sh_setenv;
1183		f_unsetenv = sh_unsetenv;
1184	}
1185	if (k_flag) {
1186		const char *errstr = NULL;
1187
1188		pidstr = getenv(SSH_AGENTPID_ENV_NAME);
1189		if (pidstr == NULL) {
1190			fprintf(stderr, "%s not set, cannot kill agent\n",
1191			    SSH_AGENTPID_ENV_NAME);
1192			exit(1);
1193		}
1194		pid = (int)strtonum(pidstr, 2, INT_MAX, &errstr);
1195		if (errstr) {
1196			fprintf(stderr,
1197			    "%s=\"%s\", which is not a good PID: %s\n",
1198			    SSH_AGENTPID_ENV_NAME, pidstr, errstr);
1199			exit(1);
1200		}
1201		if (kill(pid, SIGTERM) == -1) {
1202			perror("kill");
1203			exit(1);
1204		}
1205		(*f_unsetenv)(SSH_AUTHSOCKET_ENV_NAME);
1206		(*f_unsetenv)(SSH_AGENTPID_ENV_NAME);
1207		printf("echo Agent pid %ld killed;\n", (long)pid);
1208		exit(0);
1209	}
1210
1211	/*
1212	 * Minimum file descriptors:
1213	 * stdio (3) + listener (1) + syslog (1 maybe) + connection (1) +
1214	 * a few spare for libc / stack protectors / sanitisers, etc.
1215	 */
1216#define SSH_AGENT_MIN_FDS (3+1+1+1+4)
1217	if (rlim.rlim_cur < SSH_AGENT_MIN_FDS)
1218		fatal("%s: file descriptior rlimit %lld too low (minimum %u)",
1219		    __progname, (long long)rlim.rlim_cur, SSH_AGENT_MIN_FDS);
1220	maxfds = rlim.rlim_cur - SSH_AGENT_MIN_FDS;
1221
1222	parent_pid = getpid();
1223
1224	if (agentsocket == NULL) {
1225		/* Create private directory for agent socket */
1226		mktemp_proto(socket_dir, sizeof(socket_dir));
1227		if (mkdtemp(socket_dir) == NULL) {
1228			perror("mkdtemp: private socket dir");
1229			exit(1);
1230		}
1231		snprintf(socket_name, sizeof socket_name, "%s/agent.%ld", socket_dir,
1232		    (long)parent_pid);
1233	} else {
1234		/* Try to use specified agent socket */
1235		socket_dir[0] = '\0';
1236		strlcpy(socket_name, agentsocket, sizeof socket_name);
1237	}
1238
1239	/*
1240	 * Create socket early so it will exist before command gets run from
1241	 * the parent.
1242	 */
1243	prev_mask = umask(0177);
1244	sock = unix_listener(socket_name, SSH_LISTEN_BACKLOG, 0);
1245	if (sock < 0) {
1246		/* XXX - unix_listener() calls error() not perror() */
1247		*socket_name = '\0'; /* Don't unlink any existing file */
1248		cleanup_exit(1);
1249	}
1250	umask(prev_mask);
1251
1252	/*
1253	 * Fork, and have the parent execute the command, if any, or present
1254	 * the socket data.  The child continues as the authentication agent.
1255	 */
1256	if (D_flag || d_flag) {
1257		log_init(__progname,
1258		    d_flag ? SYSLOG_LEVEL_DEBUG3 : SYSLOG_LEVEL_INFO,
1259		    SYSLOG_FACILITY_AUTH, 1);
1260		if (c_flag)
1261			printf("setenv %s %s;\n",
1262			    SSH_AUTHSOCKET_ENV_NAME, socket_name);
1263		else
1264			printf("%s=%s; export %s;\n",
1265			    SSH_AUTHSOCKET_ENV_NAME, socket_name,
1266			    SSH_AUTHSOCKET_ENV_NAME);
1267		printf("echo Agent pid %ld;\n", (long)parent_pid);
1268		fflush(stdout);
1269		goto skip;
1270	}
1271	pid = fork();
1272	if (pid == -1) {
1273		perror("fork");
1274		cleanup_exit(1);
1275	}
1276	if (pid != 0) {		/* Parent - execute the given command. */
1277		close(sock);
1278		snprintf(pidstrbuf, sizeof pidstrbuf, "%ld", (long)pid);
1279		if (ac == 0) {
1280			(*f_setenv)(SSH_AUTHSOCKET_ENV_NAME, socket_name);
1281			(*f_setenv)(SSH_AGENTPID_ENV_NAME, pidstrbuf);
1282			printf("echo Agent pid %ld;\n", (long)pid);
1283			exit(0);
1284		}
1285		if (setenv(SSH_AUTHSOCKET_ENV_NAME, socket_name, 1) == -1 ||
1286		    setenv(SSH_AGENTPID_ENV_NAME, pidstrbuf, 1) == -1) {
1287			perror("setenv");
1288			exit(1);
1289		}
1290		execvp(av[0], av);
1291		perror(av[0]);
1292		exit(1);
1293	}
1294	/* child */
1295	log_init(__progname, SYSLOG_LEVEL_INFO, SYSLOG_FACILITY_AUTH, 0);
1296
1297	if (setsid() == -1) {
1298		error("setsid: %s", strerror(errno));
1299		cleanup_exit(1);
1300	}
1301
1302	(void)chdir("/");
1303
1304	if (sock != STDERR_FILENO + 1) {
1305		if (dup2(sock, STDERR_FILENO + 1) == -1) {
1306			error("dup2: %s", strerror(errno));
1307			cleanup_exit(1);
1308		}
1309		close(sock);
1310		sock = STDERR_FILENO + 1;
1311	}
1312#if defined(F_CLOSEM)
1313	if (fcntl(sock + 1, F_CLOSEM, 0) == -1) {
1314		error("fcntl F_CLOSEM: %s", strerror(errno));
1315		cleanup_exit(1);
1316	}
1317#else
1318	{
1319		int nfiles;
1320#if defined(_SC_OPEN_MAX)
1321		nfiles = sysconf(_SC_OPEN_MAX);
1322#elif defined(RLIMIT_NOFILE)
1323		if (getrlimit(RLIMIT_CORE, &rlim) < 0) {
1324			error("getrlimit RLIMIT_NOFILE: %s", strerror(errno));
1325			cleanup_exit(1);
1326		}
1327		nfiles = rlim.rlim_cur;
1328#elif defined(OPEN_MAX)
1329		nfiles = OPEN_MAX;
1330#elif defined(NOFILE)
1331		nfiles = NOFILE;
1332#else
1333		nfiles = 1024;
1334#endif
1335		for (fd = sock + 1; fd < nfiles; fd++)
1336			close(fd);
1337	}
1338#endif
1339	if ((fd = open(_PATH_DEVNULL, O_RDWR, 0)) != -1) {
1340		if (dup2(fd, STDIN_FILENO) == -1 ||
1341		    dup2(fd, STDOUT_FILENO) == -1 ||
1342		    dup2(fd, STDERR_FILENO) == -1) {
1343			error("dup2: %s", strerror(errno));
1344			cleanup_exit(1);
1345		}
1346		if (fd > STDERR_FILENO)
1347			close(fd);
1348	}
1349
1350	/* deny core dumps, since memory contains unencrypted private keys */
1351	rlim.rlim_cur = rlim.rlim_max = 0;
1352	if (setrlimit(RLIMIT_CORE, &rlim) < 0) {
1353		error("setrlimit RLIMIT_CORE: %s", strerror(errno));
1354		cleanup_exit(1);
1355	}
1356
1357skip:
1358
1359	cleanup_pid = getpid();
1360
1361#ifdef ENABLE_PKCS11
1362	pkcs11_init(0);
1363#endif
1364	new_socket(AUTH_SOCKET, sock);
1365	if (ac > 0)
1366		parent_alive_interval = 10;
1367	idtab_init();
1368	signal(SIGPIPE, SIG_IGN);
1369	signal(SIGINT, (d_flag | D_flag) ? cleanup_handler : SIG_IGN);
1370	signal(SIGHUP, cleanup_handler);
1371	signal(SIGTERM, cleanup_handler);
1372
1373#ifdef __OpenBSD__
1374	if (pledge("stdio rpath cpath unix id proc exec", NULL) == -1)
1375		fatal("%s: pledge: %s", __progname, strerror(errno));
1376#endif
1377
1378	while (1) {
1379		prepare_poll(&pfd, &npfd, &timeout, maxfds);
1380		result = poll(pfd, npfd, timeout);
1381		saved_errno = errno;
1382		if (parent_alive_interval != 0)
1383			check_parent_exists();
1384		(void) reaper();	/* remove expired keys */
1385		if (result < 0) {
1386			if (saved_errno == EINTR)
1387				continue;
1388			fatal("poll: %s", strerror(saved_errno));
1389		} else if (result > 0)
1390			after_poll(pfd, npfd, maxfds);
1391	}
1392	/* NOTREACHED */
1393}
1394