• Home
  • History
  • Annotate
  • Line#
  • Scopes#
  • Navigate#
  • Raw
  • Download
1 /* $OpenBSD: ssh-agent.c,v 1.204 2015/07/08 20:24:02 markus Exp $ */
2 /*
3  * Author: Tatu Ylonen <ylo@cs.hut.fi>
4  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
5  *                    All rights reserved
6  * The authentication agent program.
7  *
8  * As far as I am concerned, the code I have written for this software
9  * can be used freely for any purpose.  Any derived versions of this
10  * software must be clearly marked as such, and if the derived work is
11  * incompatible with the protocol description in the RFC file, it must be
12  * called by a name other than "ssh" or "Secure Shell".
13  *
14  * Copyright (c) 2000, 2001 Markus Friedl.  All rights reserved.
15  *
16  * Redistribution and use in source and binary forms, with or without
17  * modification, are permitted provided that the following conditions
18  * are met:
19  * 1. Redistributions of source code must retain the above copyright
20  *    notice, this list of conditions and the following disclaimer.
21  * 2. Redistributions in binary form must reproduce the above copyright
22  *    notice, this list of conditions and the following disclaimer in the
23  *    documentation and/or other materials provided with the distribution.
24  *
25  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
26  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
27  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
28  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
29  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
30  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
31  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
32  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
33  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
34  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
35  */
36 
37 #include "includes.h"
38 
39 #include <sys/param.h>	/* MIN MAX */
40 #include <sys/types.h>
41 #include <sys/param.h>
42 #include <sys/resource.h>
43 #include <sys/stat.h>
44 #include <sys/socket.h>
45 #ifdef HAVE_SYS_TIME_H
46 # include <sys/time.h>
47 #endif
48 #ifdef HAVE_SYS_UN_H
49 # include <sys/un.h>
50 #endif
51 #include "openbsd-compat/sys-queue.h"
52 
53 #ifdef WITH_OPENSSL
54 #include <openssl/evp.h>
55 #include "openbsd-compat/openssl-compat.h"
56 #endif
57 
58 #include <errno.h>
59 #include <fcntl.h>
60 #include <limits.h>
61 #ifdef HAVE_PATHS_H
62 # include <paths.h>
63 #endif
64 #include <signal.h>
65 #include <stdarg.h>
66 #include <stdio.h>
67 #include <stdlib.h>
68 #include <time.h>
69 #include <string.h>
70 #include <unistd.h>
71 #ifdef HAVE_UTIL_H
72 # include <util.h>
73 #endif
74 
75 #include "xmalloc.h"
76 #include "ssh.h"
77 #include "rsa.h"
78 #include "sshbuf.h"
79 #include "sshkey.h"
80 #include "authfd.h"
81 #include "compat.h"
82 #include "log.h"
83 #include "misc.h"
84 #include "digest.h"
85 #include "ssherr.h"
86 
87 #ifdef ENABLE_PKCS11
88 #include "ssh-pkcs11.h"
89 #endif
90 
91 #if defined(HAVE_SYS_PRCTL_H)
92 #include <sys/prctl.h>	/* For prctl() and PR_SET_DUMPABLE */
93 #endif
94 
95 typedef enum {
96 	AUTH_UNUSED,
97 	AUTH_SOCKET,
98 	AUTH_CONNECTION
99 } sock_type;
100 
101 typedef struct {
102 	int fd;
103 	sock_type type;
104 	struct sshbuf *input;
105 	struct sshbuf *output;
106 	struct sshbuf *request;
107 } SocketEntry;
108 
109 u_int sockets_alloc = 0;
110 SocketEntry *sockets = NULL;
111 
112 typedef struct identity {
113 	TAILQ_ENTRY(identity) next;
114 	struct sshkey *key;
115 	char *comment;
116 	char *provider;
117 	time_t death;
118 	u_int confirm;
119 } Identity;
120 
121 typedef struct {
122 	int nentries;
123 	TAILQ_HEAD(idqueue, identity) idlist;
124 } Idtab;
125 
126 /* private key table, one per protocol version */
127 Idtab idtable[3];
128 
129 int max_fd = 0;
130 
131 /* pid of shell == parent of agent */
132 pid_t parent_pid = -1;
133 time_t parent_alive_interval = 0;
134 
135 /* pid of process for which cleanup_socket is applicable */
136 pid_t cleanup_pid = 0;
137 
138 /* pathname and directory for AUTH_SOCKET */
139 char socket_name[PATH_MAX];
140 char socket_dir[PATH_MAX];
141 
142 /* locking */
143 #define LOCK_SIZE	32
144 #define LOCK_SALT_SIZE	16
145 #define LOCK_ROUNDS	1
146 int locked = 0;
147 char lock_passwd[LOCK_SIZE];
148 char lock_salt[LOCK_SALT_SIZE];
149 
150 extern char *__progname;
151 
152 /* Default lifetime in seconds (0 == forever) */
153 static long lifetime = 0;
154 
155 static int fingerprint_hash = SSH_FP_HASH_DEFAULT;
156 
157 static void
close_socket(SocketEntry * e)158 close_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 
168 static void
idtab_init(void)169 idtab_init(void)
170 {
171 	int i;
172 
173 	for (i = 0; i <=2; i++) {
174 		TAILQ_INIT(&idtable[i].idlist);
175 		idtable[i].nentries = 0;
176 	}
177 }
178 
179 /* return private key table for requested protocol version */
180 static Idtab *
idtab_lookup(int version)181 idtab_lookup(int version)
182 {
183 	if (version < 1 || version > 2)
184 		fatal("internal error, bad protocol version %d", version);
185 	return &idtable[version];
186 }
187 
188 static void
free_identity(Identity * id)189 free_identity(Identity *id)
190 {
191 	sshkey_free(id->key);
192 	free(id->provider);
193 	free(id->comment);
194 	free(id);
195 }
196 
197 /* return matching private key for given public key */
198 static Identity *
lookup_identity(struct sshkey * key,int version)199 lookup_identity(struct sshkey *key, int version)
200 {
201 	Identity *id;
202 
203 	Idtab *tab = idtab_lookup(version);
204 	TAILQ_FOREACH(id, &tab->idlist, next) {
205 		if (sshkey_equal(key, id->key))
206 			return (id);
207 	}
208 	return (NULL);
209 }
210 
211 /* Check confirmation of keysign request */
212 static int
confirm_key(Identity * id)213 confirm_key(Identity *id)
214 {
215 	char *p;
216 	int ret = -1;
217 
218 	p = sshkey_fingerprint(id->key, fingerprint_hash, SSH_FP_DEFAULT);
219 	if (p != NULL &&
220 	    ask_permission("Allow use of key %s?\nKey fingerprint %s.",
221 	    id->comment, p))
222 		ret = 0;
223 	free(p);
224 
225 	return (ret);
226 }
227 
228 static void
send_status(SocketEntry * e,int success)229 send_status(SocketEntry *e, int success)
230 {
231 	int r;
232 
233 	if ((r = sshbuf_put_u32(e->output, 1)) != 0 ||
234 	    (r = sshbuf_put_u8(e->output, success ?
235 	    SSH_AGENT_SUCCESS : SSH_AGENT_FAILURE)) != 0)
236 		fatal("%s: buffer error: %s", __func__, ssh_err(r));
237 }
238 
239 /* send list of supported public keys to 'client' */
240 static void
process_request_identities(SocketEntry * e,int version)241 process_request_identities(SocketEntry *e, int version)
242 {
243 	Idtab *tab = idtab_lookup(version);
244 	Identity *id;
245 	struct sshbuf *msg;
246 	int r;
247 
248 	if ((msg = sshbuf_new()) == NULL)
249 		fatal("%s: sshbuf_new failed", __func__);
250 	if ((r = sshbuf_put_u8(msg, (version == 1) ?
251 	    SSH_AGENT_RSA_IDENTITIES_ANSWER :
252 	    SSH2_AGENT_IDENTITIES_ANSWER)) != 0 ||
253 	    (r = sshbuf_put_u32(msg, tab->nentries)) != 0)
254 		fatal("%s: buffer error: %s", __func__, ssh_err(r));
255 	TAILQ_FOREACH(id, &tab->idlist, next) {
256 		if (id->key->type == KEY_RSA1) {
257 #ifdef WITH_SSH1
258 			if ((r = sshbuf_put_u32(msg,
259 			    BN_num_bits(id->key->rsa->n))) != 0 ||
260 			    (r = sshbuf_put_bignum1(msg,
261 			    id->key->rsa->e)) != 0 ||
262 			    (r = sshbuf_put_bignum1(msg,
263 			    id->key->rsa->n)) != 0)
264 				fatal("%s: buffer error: %s",
265 				    __func__, ssh_err(r));
266 #endif
267 		} else {
268 			u_char *blob;
269 			size_t blen;
270 
271 			if ((r = sshkey_to_blob(id->key, &blob, &blen)) != 0) {
272 				error("%s: sshkey_to_blob: %s", __func__,
273 				    ssh_err(r));
274 				continue;
275 			}
276 			if ((r = sshbuf_put_string(msg, blob, blen)) != 0)
277 				fatal("%s: buffer error: %s",
278 				    __func__, ssh_err(r));
279 			free(blob);
280 		}
281 		if ((r = sshbuf_put_cstring(msg, id->comment)) != 0)
282 			fatal("%s: buffer error: %s", __func__, ssh_err(r));
283 	}
284 	if ((r = sshbuf_put_stringb(e->output, msg)) != 0)
285 		fatal("%s: buffer error: %s", __func__, ssh_err(r));
286 	sshbuf_free(msg);
287 }
288 
289 #ifdef WITH_SSH1
290 /* ssh1 only */
291 static void
process_authentication_challenge1(SocketEntry * e)292 process_authentication_challenge1(SocketEntry *e)
293 {
294 	u_char buf[32], mdbuf[16], session_id[16];
295 	u_int response_type;
296 	BIGNUM *challenge;
297 	Identity *id;
298 	int r, len;
299 	struct sshbuf *msg;
300 	struct ssh_digest_ctx *md;
301 	struct sshkey *key;
302 
303 	if ((msg = sshbuf_new()) == NULL)
304 		fatal("%s: sshbuf_new failed", __func__);
305 	if ((key = sshkey_new(KEY_RSA1)) == NULL)
306 		fatal("%s: sshkey_new failed", __func__);
307 	if ((challenge = BN_new()) == NULL)
308 		fatal("%s: BN_new failed", __func__);
309 
310 	if ((r = sshbuf_get_u32(e->request, NULL)) != 0 || /* ignored */
311 	    (r = sshbuf_get_bignum1(e->request, key->rsa->e)) != 0 ||
312 	    (r = sshbuf_get_bignum1(e->request, key->rsa->n)) != 0 ||
313 	    (r = sshbuf_get_bignum1(e->request, challenge)))
314 		fatal("%s: buffer error: %s", __func__, ssh_err(r));
315 
316 	/* Only protocol 1.1 is supported */
317 	if (sshbuf_len(e->request) == 0)
318 		goto failure;
319 	if ((r = sshbuf_get(e->request, session_id, sizeof(session_id))) != 0 ||
320 	    (r = sshbuf_get_u32(e->request, &response_type)) != 0)
321 		fatal("%s: buffer error: %s", __func__, ssh_err(r));
322 	if (response_type != 1)
323 		goto failure;
324 
325 	id = lookup_identity(key, 1);
326 	if (id != NULL && (!id->confirm || confirm_key(id) == 0)) {
327 		struct sshkey *private = id->key;
328 		/* Decrypt the challenge using the private key. */
329 		if ((r = rsa_private_decrypt(challenge, challenge,
330 		    private->rsa) != 0)) {
331 			fatal("%s: rsa_public_encrypt: %s", __func__,
332 			    ssh_err(r));
333 			goto failure;	/* XXX ? */
334 		}
335 
336 		/* The response is MD5 of decrypted challenge plus session id */
337 		len = BN_num_bytes(challenge);
338 		if (len <= 0 || len > 32) {
339 			logit("%s: bad challenge length %d", __func__, len);
340 			goto failure;
341 		}
342 		memset(buf, 0, 32);
343 		BN_bn2bin(challenge, buf + 32 - len);
344 		if ((md = ssh_digest_start(SSH_DIGEST_MD5)) == NULL ||
345 		    ssh_digest_update(md, buf, 32) < 0 ||
346 		    ssh_digest_update(md, session_id, 16) < 0 ||
347 		    ssh_digest_final(md, mdbuf, sizeof(mdbuf)) < 0)
348 			fatal("%s: md5 failed", __func__);
349 		ssh_digest_free(md);
350 
351 		/* Send the response. */
352 		if ((r = sshbuf_put_u8(msg, SSH_AGENT_RSA_RESPONSE)) != 0 ||
353 		    (r = sshbuf_put(msg, mdbuf, sizeof(mdbuf))) != 0)
354 			fatal("%s: buffer error: %s", __func__, ssh_err(r));
355 		goto send;
356 	}
357 
358  failure:
359 	/* Unknown identity or protocol error.  Send failure. */
360 	if ((r = sshbuf_put_u8(msg, SSH_AGENT_FAILURE)) != 0)
361 		fatal("%s: buffer error: %s", __func__, ssh_err(r));
362  send:
363 	if ((r = sshbuf_put_stringb(e->output, msg)) != 0)
364 		fatal("%s: buffer error: %s", __func__, ssh_err(r));
365 	sshkey_free(key);
366 	BN_clear_free(challenge);
367 	sshbuf_free(msg);
368 }
369 #endif
370 
371 /* ssh2 only */
372 static void
process_sign_request2(SocketEntry * e)373 process_sign_request2(SocketEntry *e)
374 {
375 	u_char *blob, *data, *signature = NULL;
376 	size_t blen, dlen, slen = 0;
377 	u_int compat = 0, flags;
378 	int r, ok = -1;
379 	struct sshbuf *msg;
380 	struct sshkey *key;
381 	struct identity *id;
382 
383 	if ((msg = sshbuf_new()) == NULL)
384 		fatal("%s: sshbuf_new failed", __func__);
385 	if ((r = sshbuf_get_string(e->request, &blob, &blen)) != 0 ||
386 	    (r = sshbuf_get_string(e->request, &data, &dlen)) != 0 ||
387 	    (r = sshbuf_get_u32(e->request, &flags)) != 0)
388 		fatal("%s: buffer error: %s", __func__, ssh_err(r));
389 	if (flags & SSH_AGENT_OLD_SIGNATURE)
390 		compat = SSH_BUG_SIGBLOB;
391 	if ((r = sshkey_from_blob(blob, blen, &key)) != 0) {
392 		error("%s: cannot parse key blob: %s", __func__, ssh_err(ok));
393 		goto send;
394 	}
395 	if ((id = lookup_identity(key, 2)) == NULL) {
396 		verbose("%s: %s key not found", __func__, sshkey_type(key));
397 		goto send;
398 	}
399 	if (id->confirm && confirm_key(id) != 0) {
400 		verbose("%s: user refused key", __func__);
401 		goto send;
402 	}
403 	if ((r = sshkey_sign(id->key, &signature, &slen,
404 	    data, dlen, compat)) != 0) {
405 		error("%s: sshkey_sign: %s", __func__, ssh_err(ok));
406 		goto send;
407 	}
408 	/* Success */
409 	ok = 0;
410  send:
411 	sshkey_free(key);
412 	if (ok == 0) {
413 		if ((r = sshbuf_put_u8(msg, SSH2_AGENT_SIGN_RESPONSE)) != 0 ||
414 		    (r = sshbuf_put_string(msg, signature, slen)) != 0)
415 			fatal("%s: buffer error: %s", __func__, ssh_err(r));
416 	} else if ((r = sshbuf_put_u8(msg, SSH_AGENT_FAILURE)) != 0)
417 		fatal("%s: buffer error: %s", __func__, ssh_err(r));
418 
419 	if ((r = sshbuf_put_stringb(e->output, msg)) != 0)
420 		fatal("%s: buffer error: %s", __func__, ssh_err(r));
421 
422 	sshbuf_free(msg);
423 	free(data);
424 	free(blob);
425 	free(signature);
426 }
427 
428 /* shared */
429 static void
process_remove_identity(SocketEntry * e,int version)430 process_remove_identity(SocketEntry *e, int version)
431 {
432 	size_t blen;
433 	int r, success = 0;
434 	struct sshkey *key = NULL;
435 	u_char *blob;
436 #ifdef WITH_SSH1
437 	u_int bits;
438 #endif /* WITH_SSH1 */
439 
440 	switch (version) {
441 #ifdef WITH_SSH1
442 	case 1:
443 		if ((key = sshkey_new(KEY_RSA1)) == NULL) {
444 			error("%s: sshkey_new failed", __func__);
445 			return;
446 		}
447 		if ((r = sshbuf_get_u32(e->request, &bits)) != 0 ||
448 		    (r = sshbuf_get_bignum1(e->request, key->rsa->e)) != 0 ||
449 		    (r = sshbuf_get_bignum1(e->request, key->rsa->n)) != 0)
450 			fatal("%s: buffer error: %s", __func__, ssh_err(r));
451 
452 		if (bits != sshkey_size(key))
453 			logit("Warning: identity keysize mismatch: "
454 			    "actual %u, announced %u",
455 			    sshkey_size(key), bits);
456 		break;
457 #endif /* WITH_SSH1 */
458 	case 2:
459 		if ((r = sshbuf_get_string(e->request, &blob, &blen)) != 0)
460 			fatal("%s: buffer error: %s", __func__, ssh_err(r));
461 		if ((r = sshkey_from_blob(blob, blen, &key)) != 0)
462 			error("%s: sshkey_from_blob failed: %s",
463 			    __func__, ssh_err(r));
464 		free(blob);
465 		break;
466 	}
467 	if (key != NULL) {
468 		Identity *id = lookup_identity(key, version);
469 		if (id != NULL) {
470 			/*
471 			 * We have this key.  Free the old key.  Since we
472 			 * don't want to leave empty slots in the middle of
473 			 * the array, we actually free the key there and move
474 			 * all the entries between the empty slot and the end
475 			 * of the array.
476 			 */
477 			Idtab *tab = idtab_lookup(version);
478 			if (tab->nentries < 1)
479 				fatal("process_remove_identity: "
480 				    "internal error: tab->nentries %d",
481 				    tab->nentries);
482 			TAILQ_REMOVE(&tab->idlist, id, next);
483 			free_identity(id);
484 			tab->nentries--;
485 			success = 1;
486 		}
487 		sshkey_free(key);
488 	}
489 	send_status(e, success);
490 }
491 
492 static void
process_remove_all_identities(SocketEntry * e,int version)493 process_remove_all_identities(SocketEntry *e, int version)
494 {
495 	Idtab *tab = idtab_lookup(version);
496 	Identity *id;
497 
498 	/* Loop over all identities and clear the keys. */
499 	for (id = TAILQ_FIRST(&tab->idlist); id;
500 	    id = TAILQ_FIRST(&tab->idlist)) {
501 		TAILQ_REMOVE(&tab->idlist, id, next);
502 		free_identity(id);
503 	}
504 
505 	/* Mark that there are no identities. */
506 	tab->nentries = 0;
507 
508 	/* Send success. */
509 	send_status(e, 1);
510 }
511 
512 /* removes expired keys and returns number of seconds until the next expiry */
513 static time_t
reaper(void)514 reaper(void)
515 {
516 	time_t deadline = 0, now = monotime();
517 	Identity *id, *nxt;
518 	int version;
519 	Idtab *tab;
520 
521 	for (version = 1; version < 3; version++) {
522 		tab = idtab_lookup(version);
523 		for (id = TAILQ_FIRST(&tab->idlist); id; id = nxt) {
524 			nxt = TAILQ_NEXT(id, next);
525 			if (id->death == 0)
526 				continue;
527 			if (now >= id->death) {
528 				debug("expiring key '%s'", id->comment);
529 				TAILQ_REMOVE(&tab->idlist, id, next);
530 				free_identity(id);
531 				tab->nentries--;
532 			} else
533 				deadline = (deadline == 0) ? id->death :
534 				    MIN(deadline, id->death);
535 		}
536 	}
537 	if (deadline == 0 || deadline <= now)
538 		return 0;
539 	else
540 		return (deadline - now);
541 }
542 
543 /*
544  * XXX this and the corresponding serialisation function probably belongs
545  * in key.c
546  */
547 #ifdef WITH_SSH1
548 static int
agent_decode_rsa1(struct sshbuf * m,struct sshkey ** kp)549 agent_decode_rsa1(struct sshbuf *m, struct sshkey **kp)
550 {
551 	struct sshkey *k = NULL;
552 	int r = SSH_ERR_INTERNAL_ERROR;
553 
554 	*kp = NULL;
555 	if ((k = sshkey_new_private(KEY_RSA1)) == NULL)
556 		return SSH_ERR_ALLOC_FAIL;
557 
558 	if ((r = sshbuf_get_u32(m, NULL)) != 0 ||		/* ignored */
559 	    (r = sshbuf_get_bignum1(m, k->rsa->n)) != 0 ||
560 	    (r = sshbuf_get_bignum1(m, k->rsa->e)) != 0 ||
561 	    (r = sshbuf_get_bignum1(m, k->rsa->d)) != 0 ||
562 	    (r = sshbuf_get_bignum1(m, k->rsa->iqmp)) != 0 ||
563 	    /* SSH1 and SSL have p and q swapped */
564 	    (r = sshbuf_get_bignum1(m, k->rsa->q)) != 0 ||	/* p */
565 	    (r = sshbuf_get_bignum1(m, k->rsa->p)) != 0) 	/* q */
566 		goto out;
567 
568 	/* Generate additional parameters */
569 	if ((r = rsa_generate_additional_parameters(k->rsa)) != 0)
570 		goto out;
571 	/* enable blinding */
572 	if (RSA_blinding_on(k->rsa, NULL) != 1) {
573 		r = SSH_ERR_LIBCRYPTO_ERROR;
574 		goto out;
575 	}
576 
577 	r = 0; /* success */
578  out:
579 	if (r == 0)
580 		*kp = k;
581 	else
582 		sshkey_free(k);
583 	return r;
584 }
585 #endif /* WITH_SSH1 */
586 
587 static void
process_add_identity(SocketEntry * e,int version)588 process_add_identity(SocketEntry *e, int version)
589 {
590 	Idtab *tab = idtab_lookup(version);
591 	Identity *id;
592 	int success = 0, confirm = 0;
593 	u_int seconds;
594 	char *comment = NULL;
595 	time_t death = 0;
596 	struct sshkey *k = NULL;
597 	u_char ctype;
598 	int r = SSH_ERR_INTERNAL_ERROR;
599 
600 	switch (version) {
601 #ifdef WITH_SSH1
602 	case 1:
603 		r = agent_decode_rsa1(e->request, &k);
604 		break;
605 #endif /* WITH_SSH1 */
606 	case 2:
607 		r = sshkey_private_deserialize(e->request, &k);
608 		break;
609 	}
610 	if (r != 0 || k == NULL ||
611 	    (r = sshbuf_get_cstring(e->request, &comment, NULL)) != 0) {
612 		error("%s: decode private key: %s", __func__, ssh_err(r));
613 		goto err;
614 	}
615 
616 	while (sshbuf_len(e->request)) {
617 		if ((r = sshbuf_get_u8(e->request, &ctype)) != 0) {
618 			error("%s: buffer error: %s", __func__, ssh_err(r));
619 			goto err;
620 		}
621 		switch (ctype) {
622 		case SSH_AGENT_CONSTRAIN_LIFETIME:
623 			if ((r = sshbuf_get_u32(e->request, &seconds)) != 0) {
624 				error("%s: bad lifetime constraint: %s",
625 				    __func__, ssh_err(r));
626 				goto err;
627 			}
628 			death = monotime() + seconds;
629 			break;
630 		case SSH_AGENT_CONSTRAIN_CONFIRM:
631 			confirm = 1;
632 			break;
633 		default:
634 			error("%s: Unknown constraint %d", __func__, ctype);
635  err:
636 			sshbuf_reset(e->request);
637 			free(comment);
638 			sshkey_free(k);
639 			goto send;
640 		}
641 	}
642 
643 	success = 1;
644 	if (lifetime && !death)
645 		death = monotime() + lifetime;
646 	if ((id = lookup_identity(k, version)) == NULL) {
647 		id = xcalloc(1, sizeof(Identity));
648 		id->key = k;
649 		TAILQ_INSERT_TAIL(&tab->idlist, id, next);
650 		/* Increment the number of identities. */
651 		tab->nentries++;
652 	} else {
653 		sshkey_free(k);
654 		free(id->comment);
655 	}
656 	id->comment = comment;
657 	id->death = death;
658 	id->confirm = confirm;
659 send:
660 	send_status(e, success);
661 }
662 
663 /* XXX todo: encrypt sensitive data with passphrase */
664 static void
process_lock_agent(SocketEntry * e,int lock)665 process_lock_agent(SocketEntry *e, int lock)
666 {
667 	int r, success = 0, delay;
668 	char *passwd, passwdhash[LOCK_SIZE];
669 	static u_int fail_count = 0;
670 	size_t pwlen;
671 
672 	if ((r = sshbuf_get_cstring(e->request, &passwd, &pwlen)) != 0)
673 		fatal("%s: buffer error: %s", __func__, ssh_err(r));
674 	if (pwlen == 0) {
675 		debug("empty password not supported");
676 	} else if (locked && !lock) {
677 		if (bcrypt_pbkdf(passwd, pwlen, lock_salt, sizeof(lock_salt),
678 		    passwdhash, sizeof(passwdhash), LOCK_ROUNDS) < 0)
679 			fatal("bcrypt_pbkdf");
680 		if (timingsafe_bcmp(passwdhash, lock_passwd, LOCK_SIZE) == 0) {
681 			debug("agent unlocked");
682 			locked = 0;
683 			fail_count = 0;
684 			explicit_bzero(lock_passwd, sizeof(lock_passwd));
685 			success = 1;
686 		} else {
687 			/* delay in 0.1s increments up to 10s */
688 			if (fail_count < 100)
689 				fail_count++;
690 			delay = 100000 * fail_count;
691 			debug("unlock failed, delaying %0.1lf seconds",
692 			    (double)delay/1000000);
693 			usleep(delay);
694 		}
695 		explicit_bzero(passwdhash, sizeof(passwdhash));
696 	} else if (!locked && lock) {
697 		debug("agent locked");
698 		locked = 1;
699 		arc4random_buf(lock_salt, sizeof(lock_salt));
700 		if (bcrypt_pbkdf(passwd, pwlen, lock_salt, sizeof(lock_salt),
701 		    lock_passwd, sizeof(lock_passwd), LOCK_ROUNDS) < 0)
702 			fatal("bcrypt_pbkdf");
703 		success = 1;
704 	}
705 	explicit_bzero(passwd, pwlen);
706 	free(passwd);
707 	send_status(e, success);
708 }
709 
710 static void
no_identities(SocketEntry * e,u_int type)711 no_identities(SocketEntry *e, u_int type)
712 {
713 	struct sshbuf *msg;
714 	int r;
715 
716 	if ((msg = sshbuf_new()) == NULL)
717 		fatal("%s: sshbuf_new failed", __func__);
718 	if ((r = sshbuf_put_u8(msg,
719 	    (type == SSH_AGENTC_REQUEST_RSA_IDENTITIES) ?
720 	    SSH_AGENT_RSA_IDENTITIES_ANSWER :
721 	    SSH2_AGENT_IDENTITIES_ANSWER)) != 0 ||
722 	    (r = sshbuf_put_u32(msg, 0)) != 0 ||
723 	    (r = sshbuf_put_stringb(e->output, msg)) != 0)
724 		fatal("%s: buffer error: %s", __func__, ssh_err(r));
725 	sshbuf_free(msg);
726 }
727 
728 #ifdef ENABLE_PKCS11
729 static void
process_add_smartcard_key(SocketEntry * e)730 process_add_smartcard_key(SocketEntry *e)
731 {
732 	char *provider = NULL, *pin;
733 	int r, i, version, count = 0, success = 0, confirm = 0;
734 	u_int seconds;
735 	time_t death = 0;
736 	u_char type;
737 	struct sshkey **keys = NULL, *k;
738 	Identity *id;
739 	Idtab *tab;
740 
741 	if ((r = sshbuf_get_cstring(e->request, &provider, NULL)) != 0 ||
742 	    (r = sshbuf_get_cstring(e->request, &pin, NULL)) != 0)
743 		fatal("%s: buffer error: %s", __func__, ssh_err(r));
744 
745 	while (sshbuf_len(e->request)) {
746 		if ((r = sshbuf_get_u8(e->request, &type)) != 0)
747 			fatal("%s: buffer error: %s", __func__, ssh_err(r));
748 		switch (type) {
749 		case SSH_AGENT_CONSTRAIN_LIFETIME:
750 			if ((r = sshbuf_get_u32(e->request, &seconds)) != 0)
751 				fatal("%s: buffer error: %s",
752 				    __func__, ssh_err(r));
753 			death = monotime() + seconds;
754 			break;
755 		case SSH_AGENT_CONSTRAIN_CONFIRM:
756 			confirm = 1;
757 			break;
758 		default:
759 			error("process_add_smartcard_key: "
760 			    "Unknown constraint type %d", type);
761 			goto send;
762 		}
763 	}
764 	if (lifetime && !death)
765 		death = monotime() + lifetime;
766 
767 	count = pkcs11_add_provider(provider, pin, &keys);
768 	for (i = 0; i < count; i++) {
769 		k = keys[i];
770 		version = k->type == KEY_RSA1 ? 1 : 2;
771 		tab = idtab_lookup(version);
772 		if (lookup_identity(k, version) == NULL) {
773 			id = xcalloc(1, sizeof(Identity));
774 			id->key = k;
775 			id->provider = xstrdup(provider);
776 			id->comment = xstrdup(provider); /* XXX */
777 			id->death = death;
778 			id->confirm = confirm;
779 			TAILQ_INSERT_TAIL(&tab->idlist, id, next);
780 			tab->nentries++;
781 			success = 1;
782 		} else {
783 			sshkey_free(k);
784 		}
785 		keys[i] = NULL;
786 	}
787 send:
788 	free(pin);
789 	free(provider);
790 	free(keys);
791 	send_status(e, success);
792 }
793 
794 static void
process_remove_smartcard_key(SocketEntry * e)795 process_remove_smartcard_key(SocketEntry *e)
796 {
797 	char *provider = NULL, *pin = NULL;
798 	int r, version, success = 0;
799 	Identity *id, *nxt;
800 	Idtab *tab;
801 
802 	if ((r = sshbuf_get_cstring(e->request, &provider, NULL)) != 0 ||
803 	    (r = sshbuf_get_cstring(e->request, &pin, NULL)) != 0)
804 		fatal("%s: buffer error: %s", __func__, ssh_err(r));
805 	free(pin);
806 
807 	for (version = 1; version < 3; version++) {
808 		tab = idtab_lookup(version);
809 		for (id = TAILQ_FIRST(&tab->idlist); id; id = nxt) {
810 			nxt = TAILQ_NEXT(id, next);
811 			/* Skip file--based keys */
812 			if (id->provider == NULL)
813 				continue;
814 			if (!strcmp(provider, id->provider)) {
815 				TAILQ_REMOVE(&tab->idlist, id, next);
816 				free_identity(id);
817 				tab->nentries--;
818 			}
819 		}
820 	}
821 	if (pkcs11_del_provider(provider) == 0)
822 		success = 1;
823 	else
824 		error("process_remove_smartcard_key:"
825 		    " pkcs11_del_provider failed");
826 	free(provider);
827 	send_status(e, success);
828 }
829 #endif /* ENABLE_PKCS11 */
830 
831 /* dispatch incoming messages */
832 
833 static void
process_message(SocketEntry * e)834 process_message(SocketEntry *e)
835 {
836 	u_int msg_len;
837 	u_char type;
838 	const u_char *cp;
839 	int r;
840 
841 	if (sshbuf_len(e->input) < 5)
842 		return;		/* Incomplete message. */
843 	cp = sshbuf_ptr(e->input);
844 	msg_len = PEEK_U32(cp);
845 	if (msg_len > 256 * 1024) {
846 		close_socket(e);
847 		return;
848 	}
849 	if (sshbuf_len(e->input) < msg_len + 4)
850 		return;
851 
852 	/* move the current input to e->request */
853 	sshbuf_reset(e->request);
854 	if ((r = sshbuf_get_stringb(e->input, e->request)) != 0 ||
855 	    (r = sshbuf_get_u8(e->request, &type)) != 0)
856 		fatal("%s: buffer error: %s", __func__, ssh_err(r));
857 
858 	/* check wheter agent is locked */
859 	if (locked && type != SSH_AGENTC_UNLOCK) {
860 		sshbuf_reset(e->request);
861 		switch (type) {
862 		case SSH_AGENTC_REQUEST_RSA_IDENTITIES:
863 		case SSH2_AGENTC_REQUEST_IDENTITIES:
864 			/* send empty lists */
865 			no_identities(e, type);
866 			break;
867 		default:
868 			/* send a fail message for all other request types */
869 			send_status(e, 0);
870 		}
871 		return;
872 	}
873 
874 	debug("type %d", type);
875 	switch (type) {
876 	case SSH_AGENTC_LOCK:
877 	case SSH_AGENTC_UNLOCK:
878 		process_lock_agent(e, type == SSH_AGENTC_LOCK);
879 		break;
880 #ifdef WITH_SSH1
881 	/* ssh1 */
882 	case SSH_AGENTC_RSA_CHALLENGE:
883 		process_authentication_challenge1(e);
884 		break;
885 	case SSH_AGENTC_REQUEST_RSA_IDENTITIES:
886 		process_request_identities(e, 1);
887 		break;
888 	case SSH_AGENTC_ADD_RSA_IDENTITY:
889 	case SSH_AGENTC_ADD_RSA_ID_CONSTRAINED:
890 		process_add_identity(e, 1);
891 		break;
892 	case SSH_AGENTC_REMOVE_RSA_IDENTITY:
893 		process_remove_identity(e, 1);
894 		break;
895 #endif
896 	case SSH_AGENTC_REMOVE_ALL_RSA_IDENTITIES:
897 		process_remove_all_identities(e, 1); /* safe for !WITH_SSH1 */
898 		break;
899 	/* ssh2 */
900 	case SSH2_AGENTC_SIGN_REQUEST:
901 		process_sign_request2(e);
902 		break;
903 	case SSH2_AGENTC_REQUEST_IDENTITIES:
904 		process_request_identities(e, 2);
905 		break;
906 	case SSH2_AGENTC_ADD_IDENTITY:
907 	case SSH2_AGENTC_ADD_ID_CONSTRAINED:
908 		process_add_identity(e, 2);
909 		break;
910 	case SSH2_AGENTC_REMOVE_IDENTITY:
911 		process_remove_identity(e, 2);
912 		break;
913 	case SSH2_AGENTC_REMOVE_ALL_IDENTITIES:
914 		process_remove_all_identities(e, 2);
915 		break;
916 #ifdef ENABLE_PKCS11
917 	case SSH_AGENTC_ADD_SMARTCARD_KEY:
918 	case SSH_AGENTC_ADD_SMARTCARD_KEY_CONSTRAINED:
919 		process_add_smartcard_key(e);
920 		break;
921 	case SSH_AGENTC_REMOVE_SMARTCARD_KEY:
922 		process_remove_smartcard_key(e);
923 		break;
924 #endif /* ENABLE_PKCS11 */
925 	default:
926 		/* Unknown message.  Respond with failure. */
927 		error("Unknown message %d", type);
928 		sshbuf_reset(e->request);
929 		send_status(e, 0);
930 		break;
931 	}
932 }
933 
934 static void
new_socket(sock_type type,int fd)935 new_socket(sock_type type, int fd)
936 {
937 	u_int i, old_alloc, new_alloc;
938 
939 	set_nonblock(fd);
940 
941 	if (fd > max_fd)
942 		max_fd = fd;
943 
944 	for (i = 0; i < sockets_alloc; i++)
945 		if (sockets[i].type == AUTH_UNUSED) {
946 			sockets[i].fd = fd;
947 			if ((sockets[i].input = sshbuf_new()) == NULL)
948 				fatal("%s: sshbuf_new failed", __func__);
949 			if ((sockets[i].output = sshbuf_new()) == NULL)
950 				fatal("%s: sshbuf_new failed", __func__);
951 			if ((sockets[i].request = sshbuf_new()) == NULL)
952 				fatal("%s: sshbuf_new failed", __func__);
953 			sockets[i].type = type;
954 			return;
955 		}
956 	old_alloc = sockets_alloc;
957 	new_alloc = sockets_alloc + 10;
958 	sockets = xreallocarray(sockets, new_alloc, sizeof(sockets[0]));
959 	for (i = old_alloc; i < new_alloc; i++)
960 		sockets[i].type = AUTH_UNUSED;
961 	sockets_alloc = new_alloc;
962 	sockets[old_alloc].fd = fd;
963 	if ((sockets[old_alloc].input = sshbuf_new()) == NULL)
964 		fatal("%s: sshbuf_new failed", __func__);
965 	if ((sockets[old_alloc].output = sshbuf_new()) == NULL)
966 		fatal("%s: sshbuf_new failed", __func__);
967 	if ((sockets[old_alloc].request = sshbuf_new()) == NULL)
968 		fatal("%s: sshbuf_new failed", __func__);
969 	sockets[old_alloc].type = type;
970 }
971 
972 static int
prepare_select(fd_set ** fdrp,fd_set ** fdwp,int * fdl,u_int * nallocp,struct timeval ** tvpp)973 prepare_select(fd_set **fdrp, fd_set **fdwp, int *fdl, u_int *nallocp,
974     struct timeval **tvpp)
975 {
976 	u_int i, sz;
977 	int n = 0;
978 	static struct timeval tv;
979 	time_t deadline;
980 
981 	for (i = 0; i < sockets_alloc; i++) {
982 		switch (sockets[i].type) {
983 		case AUTH_SOCKET:
984 		case AUTH_CONNECTION:
985 			n = MAX(n, sockets[i].fd);
986 			break;
987 		case AUTH_UNUSED:
988 			break;
989 		default:
990 			fatal("Unknown socket type %d", sockets[i].type);
991 			break;
992 		}
993 	}
994 
995 	sz = howmany(n+1, NFDBITS) * sizeof(fd_mask);
996 	if (*fdrp == NULL || sz > *nallocp) {
997 		free(*fdrp);
998 		free(*fdwp);
999 		*fdrp = xmalloc(sz);
1000 		*fdwp = xmalloc(sz);
1001 		*nallocp = sz;
1002 	}
1003 	if (n < *fdl)
1004 		debug("XXX shrink: %d < %d", n, *fdl);
1005 	*fdl = n;
1006 	memset(*fdrp, 0, sz);
1007 	memset(*fdwp, 0, sz);
1008 
1009 	for (i = 0; i < sockets_alloc; i++) {
1010 		switch (sockets[i].type) {
1011 		case AUTH_SOCKET:
1012 		case AUTH_CONNECTION:
1013 			FD_SET(sockets[i].fd, *fdrp);
1014 			if (sshbuf_len(sockets[i].output) > 0)
1015 				FD_SET(sockets[i].fd, *fdwp);
1016 			break;
1017 		default:
1018 			break;
1019 		}
1020 	}
1021 	deadline = reaper();
1022 	if (parent_alive_interval != 0)
1023 		deadline = (deadline == 0) ? parent_alive_interval :
1024 		    MIN(deadline, parent_alive_interval);
1025 	if (deadline == 0) {
1026 		*tvpp = NULL;
1027 	} else {
1028 		tv.tv_sec = deadline;
1029 		tv.tv_usec = 0;
1030 		*tvpp = &tv;
1031 	}
1032 	return (1);
1033 }
1034 
1035 static void
after_select(fd_set * readset,fd_set * writeset)1036 after_select(fd_set *readset, fd_set *writeset)
1037 {
1038 	struct sockaddr_un sunaddr;
1039 	socklen_t slen;
1040 	char buf[1024];
1041 	int len, sock, r;
1042 	u_int i, orig_alloc;
1043 	uid_t euid;
1044 	gid_t egid;
1045 
1046 	for (i = 0, orig_alloc = sockets_alloc; i < orig_alloc; i++)
1047 		switch (sockets[i].type) {
1048 		case AUTH_UNUSED:
1049 			break;
1050 		case AUTH_SOCKET:
1051 			if (FD_ISSET(sockets[i].fd, readset)) {
1052 				slen = sizeof(sunaddr);
1053 				sock = accept(sockets[i].fd,
1054 				    (struct sockaddr *)&sunaddr, &slen);
1055 				if (sock < 0) {
1056 					error("accept from AUTH_SOCKET: %s",
1057 					    strerror(errno));
1058 					break;
1059 				}
1060 				if (getpeereid(sock, &euid, &egid) < 0) {
1061 					error("getpeereid %d failed: %s",
1062 					    sock, strerror(errno));
1063 					close(sock);
1064 					break;
1065 				}
1066 				if ((euid != 0) && (getuid() != euid)) {
1067 					error("uid mismatch: "
1068 					    "peer euid %u != uid %u",
1069 					    (u_int) euid, (u_int) getuid());
1070 					close(sock);
1071 					break;
1072 				}
1073 				new_socket(AUTH_CONNECTION, sock);
1074 			}
1075 			break;
1076 		case AUTH_CONNECTION:
1077 			if (sshbuf_len(sockets[i].output) > 0 &&
1078 			    FD_ISSET(sockets[i].fd, writeset)) {
1079 				len = write(sockets[i].fd,
1080 				    sshbuf_ptr(sockets[i].output),
1081 				    sshbuf_len(sockets[i].output));
1082 				if (len == -1 && (errno == EAGAIN ||
1083 				    errno == EWOULDBLOCK ||
1084 				    errno == EINTR))
1085 					continue;
1086 				if (len <= 0) {
1087 					close_socket(&sockets[i]);
1088 					break;
1089 				}
1090 				if ((r = sshbuf_consume(sockets[i].output,
1091 				    len)) != 0)
1092 					fatal("%s: buffer error: %s",
1093 					    __func__, ssh_err(r));
1094 			}
1095 			if (FD_ISSET(sockets[i].fd, readset)) {
1096 				len = read(sockets[i].fd, buf, sizeof(buf));
1097 				if (len == -1 && (errno == EAGAIN ||
1098 				    errno == EWOULDBLOCK ||
1099 				    errno == EINTR))
1100 					continue;
1101 				if (len <= 0) {
1102 					close_socket(&sockets[i]);
1103 					break;
1104 				}
1105 				if ((r = sshbuf_put(sockets[i].input,
1106 				    buf, len)) != 0)
1107 					fatal("%s: buffer error: %s",
1108 					    __func__, ssh_err(r));
1109 				explicit_bzero(buf, sizeof(buf));
1110 				process_message(&sockets[i]);
1111 			}
1112 			break;
1113 		default:
1114 			fatal("Unknown type %d", sockets[i].type);
1115 		}
1116 }
1117 
1118 static void
cleanup_socket(void)1119 cleanup_socket(void)
1120 {
1121 	if (cleanup_pid != 0 && getpid() != cleanup_pid)
1122 		return;
1123 	debug("%s: cleanup", __func__);
1124 	if (socket_name[0])
1125 		unlink(socket_name);
1126 	if (socket_dir[0])
1127 		rmdir(socket_dir);
1128 }
1129 
1130 void
cleanup_exit(int i)1131 cleanup_exit(int i)
1132 {
1133 	cleanup_socket();
1134 	_exit(i);
1135 }
1136 
1137 /*ARGSUSED*/
1138 static void
cleanup_handler(int sig)1139 cleanup_handler(int sig)
1140 {
1141 	cleanup_socket();
1142 #ifdef ENABLE_PKCS11
1143 	pkcs11_terminate();
1144 #endif
1145 	_exit(2);
1146 }
1147 
1148 static void
check_parent_exists(void)1149 check_parent_exists(void)
1150 {
1151 	/*
1152 	 * If our parent has exited then getppid() will return (pid_t)1,
1153 	 * so testing for that should be safe.
1154 	 */
1155 	if (parent_pid != -1 && getppid() != parent_pid) {
1156 		/* printf("Parent has died - Authentication agent exiting.\n"); */
1157 		cleanup_socket();
1158 		_exit(2);
1159 	}
1160 }
1161 
1162 static void
usage(void)1163 usage(void)
1164 {
1165 	fprintf(stderr,
1166 	    "usage: ssh-agent [-c | -s] [-Dd] [-a bind_address] [-E fingerprint_hash]\n"
1167 	    "                 [-t life] [command [arg ...]]\n"
1168 	    "       ssh-agent [-c | -s] -k\n");
1169 	exit(1);
1170 }
1171 
1172 int
main(int ac,char ** av)1173 main(int ac, char **av)
1174 {
1175 	int c_flag = 0, d_flag = 0, D_flag = 0, k_flag = 0, s_flag = 0;
1176 	int sock, fd, ch, result, saved_errno;
1177 	u_int nalloc;
1178 	char *shell, *format, *pidstr, *agentsocket = NULL;
1179 	fd_set *readsetp = NULL, *writesetp = NULL;
1180 #ifdef HAVE_SETRLIMIT
1181 	struct rlimit rlim;
1182 #endif
1183 	extern int optind;
1184 	extern char *optarg;
1185 	pid_t pid;
1186 	char pidstrbuf[1 + 3 * sizeof pid];
1187 	struct timeval *tvp = NULL;
1188 	size_t len;
1189 	mode_t prev_mask;
1190 
1191 	/* Ensure that fds 0, 1 and 2 are open or directed to /dev/null */
1192 	sanitise_stdfd();
1193 
1194 	/* drop */
1195 	setegid(getgid());
1196 	setgid(getgid());
1197 
1198 #if defined(HAVE_PRCTL) && defined(PR_SET_DUMPABLE)
1199 	/* Disable ptrace on Linux without sgid bit */
1200 	prctl(PR_SET_DUMPABLE, 0);
1201 #endif
1202 
1203 #ifdef WITH_OPENSSL
1204 	OpenSSL_add_all_algorithms();
1205 #endif
1206 
1207 	__progname = ssh_get_progname(av[0]);
1208 	seed_rng();
1209 
1210 	while ((ch = getopt(ac, av, "cDdksE:a:t:")) != -1) {
1211 		switch (ch) {
1212 		case 'E':
1213 			fingerprint_hash = ssh_digest_alg_by_name(optarg);
1214 			if (fingerprint_hash == -1)
1215 				fatal("Invalid hash algorithm \"%s\"", optarg);
1216 			break;
1217 		case 'c':
1218 			if (s_flag)
1219 				usage();
1220 			c_flag++;
1221 			break;
1222 		case 'k':
1223 			k_flag++;
1224 			break;
1225 		case 's':
1226 			if (c_flag)
1227 				usage();
1228 			s_flag++;
1229 			break;
1230 		case 'd':
1231 			if (d_flag || D_flag)
1232 				usage();
1233 			d_flag++;
1234 			break;
1235 		case 'D':
1236 			if (d_flag || D_flag)
1237 				usage();
1238 			D_flag++;
1239 			break;
1240 		case 'a':
1241 			agentsocket = optarg;
1242 			break;
1243 		case 't':
1244 			if ((lifetime = convtime(optarg)) == -1) {
1245 				fprintf(stderr, "Invalid lifetime\n");
1246 				usage();
1247 			}
1248 			break;
1249 		default:
1250 			usage();
1251 		}
1252 	}
1253 	ac -= optind;
1254 	av += optind;
1255 
1256 	if (ac > 0 && (c_flag || k_flag || s_flag || d_flag || D_flag))
1257 		usage();
1258 
1259 	if (ac == 0 && !c_flag && !s_flag) {
1260 		shell = getenv("SHELL");
1261 		if (shell != NULL && (len = strlen(shell)) > 2 &&
1262 		    strncmp(shell + len - 3, "csh", 3) == 0)
1263 			c_flag = 1;
1264 	}
1265 	if (k_flag) {
1266 		const char *errstr = NULL;
1267 
1268 		pidstr = getenv(SSH_AGENTPID_ENV_NAME);
1269 		if (pidstr == NULL) {
1270 			fprintf(stderr, "%s not set, cannot kill agent\n",
1271 			    SSH_AGENTPID_ENV_NAME);
1272 			exit(1);
1273 		}
1274 		pid = (int)strtonum(pidstr, 2, INT_MAX, &errstr);
1275 		if (errstr) {
1276 			fprintf(stderr,
1277 			    "%s=\"%s\", which is not a good PID: %s\n",
1278 			    SSH_AGENTPID_ENV_NAME, pidstr, errstr);
1279 			exit(1);
1280 		}
1281 		if (kill(pid, SIGTERM) == -1) {
1282 			perror("kill");
1283 			exit(1);
1284 		}
1285 		format = c_flag ? "unsetenv %s;\n" : "unset %s;\n";
1286 		printf(format, SSH_AUTHSOCKET_ENV_NAME);
1287 		printf(format, SSH_AGENTPID_ENV_NAME);
1288 		printf("echo Agent pid %ld killed;\n", (long)pid);
1289 		exit(0);
1290 	}
1291 	parent_pid = getpid();
1292 
1293 	if (agentsocket == NULL) {
1294 		/* Create private directory for agent socket */
1295 		mktemp_proto(socket_dir, sizeof(socket_dir));
1296 		if (mkdtemp(socket_dir) == NULL) {
1297 			perror("mkdtemp: private socket dir");
1298 			exit(1);
1299 		}
1300 		snprintf(socket_name, sizeof socket_name, "%s/agent.%ld", socket_dir,
1301 		    (long)parent_pid);
1302 	} else {
1303 		/* Try to use specified agent socket */
1304 		socket_dir[0] = '\0';
1305 		strlcpy(socket_name, agentsocket, sizeof socket_name);
1306 	}
1307 
1308 	/*
1309 	 * Create socket early so it will exist before command gets run from
1310 	 * the parent.
1311 	 */
1312 	prev_mask = umask(0177);
1313 	sock = unix_listener(socket_name, SSH_LISTEN_BACKLOG, 0);
1314 	if (sock < 0) {
1315 		/* XXX - unix_listener() calls error() not perror() */
1316 		*socket_name = '\0'; /* Don't unlink any existing file */
1317 		cleanup_exit(1);
1318 	}
1319 	umask(prev_mask);
1320 
1321 	/*
1322 	 * Fork, and have the parent execute the command, if any, or present
1323 	 * the socket data.  The child continues as the authentication agent.
1324 	 */
1325 	if (D_flag || d_flag) {
1326 		log_init(__progname,
1327 		    d_flag ? SYSLOG_LEVEL_DEBUG3 : SYSLOG_LEVEL_INFO,
1328 		    SYSLOG_FACILITY_AUTH, 1);
1329 		format = c_flag ? "setenv %s %s;\n" : "%s=%s; export %s;\n";
1330 		printf(format, SSH_AUTHSOCKET_ENV_NAME, socket_name,
1331 		    SSH_AUTHSOCKET_ENV_NAME);
1332 		printf("echo Agent pid %ld;\n", (long)parent_pid);
1333 		goto skip;
1334 	}
1335 	pid = fork();
1336 	if (pid == -1) {
1337 		perror("fork");
1338 		cleanup_exit(1);
1339 	}
1340 	if (pid != 0) {		/* Parent - execute the given command. */
1341 		close(sock);
1342 		snprintf(pidstrbuf, sizeof pidstrbuf, "%ld", (long)pid);
1343 		if (ac == 0) {
1344 			format = c_flag ? "setenv %s %s;\n" : "%s=%s; export %s;\n";
1345 			printf(format, SSH_AUTHSOCKET_ENV_NAME, socket_name,
1346 			    SSH_AUTHSOCKET_ENV_NAME);
1347 			printf(format, SSH_AGENTPID_ENV_NAME, pidstrbuf,
1348 			    SSH_AGENTPID_ENV_NAME);
1349 			printf("echo Agent pid %ld;\n", (long)pid);
1350 			exit(0);
1351 		}
1352 		if (setenv(SSH_AUTHSOCKET_ENV_NAME, socket_name, 1) == -1 ||
1353 		    setenv(SSH_AGENTPID_ENV_NAME, pidstrbuf, 1) == -1) {
1354 			perror("setenv");
1355 			exit(1);
1356 		}
1357 		execvp(av[0], av);
1358 		perror(av[0]);
1359 		exit(1);
1360 	}
1361 	/* child */
1362 	log_init(__progname, SYSLOG_LEVEL_INFO, SYSLOG_FACILITY_AUTH, 0);
1363 
1364 	if (setsid() == -1) {
1365 		error("setsid: %s", strerror(errno));
1366 		cleanup_exit(1);
1367 	}
1368 
1369 	(void)chdir("/");
1370 	if ((fd = open(_PATH_DEVNULL, O_RDWR, 0)) != -1) {
1371 		/* XXX might close listen socket */
1372 		(void)dup2(fd, STDIN_FILENO);
1373 		(void)dup2(fd, STDOUT_FILENO);
1374 		(void)dup2(fd, STDERR_FILENO);
1375 		if (fd > 2)
1376 			close(fd);
1377 	}
1378 
1379 #ifdef HAVE_SETRLIMIT
1380 	/* deny core dumps, since memory contains unencrypted private keys */
1381 	rlim.rlim_cur = rlim.rlim_max = 0;
1382 	if (setrlimit(RLIMIT_CORE, &rlim) < 0) {
1383 		error("setrlimit RLIMIT_CORE: %s", strerror(errno));
1384 		cleanup_exit(1);
1385 	}
1386 #endif
1387 
1388 skip:
1389 
1390 	cleanup_pid = getpid();
1391 
1392 #ifdef ENABLE_PKCS11
1393 	pkcs11_init(0);
1394 #endif
1395 	new_socket(AUTH_SOCKET, sock);
1396 	if (ac > 0)
1397 		parent_alive_interval = 10;
1398 	idtab_init();
1399 	signal(SIGPIPE, SIG_IGN);
1400 	signal(SIGINT, (d_flag | D_flag) ? cleanup_handler : SIG_IGN);
1401 	signal(SIGHUP, cleanup_handler);
1402 	signal(SIGTERM, cleanup_handler);
1403 	nalloc = 0;
1404 
1405 	while (1) {
1406 		prepare_select(&readsetp, &writesetp, &max_fd, &nalloc, &tvp);
1407 		result = select(max_fd + 1, readsetp, writesetp, NULL, tvp);
1408 		saved_errno = errno;
1409 		if (parent_alive_interval != 0)
1410 			check_parent_exists();
1411 		(void) reaper();	/* remove expired keys */
1412 		if (result < 0) {
1413 			if (saved_errno == EINTR)
1414 				continue;
1415 			fatal("select: %s", strerror(saved_errno));
1416 		} else if (result > 0)
1417 			after_select(readsetp, writesetp);
1418 	}
1419 	/* NOTREACHED */
1420 }
1421