xref: /freebsd/libexec/tftpd/tftpd.c (revision 6b129086dcee14496517fae085b448e3edc69bc7)
1 /*
2  * Copyright (c) 1983, 1993
3  *	The Regents of the University of California.  All rights reserved.
4  *
5  * Redistribution and use in source and binary forms, with or without
6  * modification, are permitted provided that the following conditions
7  * are met:
8  * 1. Redistributions of source code must retain the above copyright
9  *    notice, this list of conditions and the following disclaimer.
10  * 2. Redistributions in binary form must reproduce the above copyright
11  *    notice, this list of conditions and the following disclaimer in the
12  *    documentation and/or other materials provided with the distribution.
13  * 3. Neither the name of the University nor the names of its contributors
14  *    may be used to endorse or promote products derived from this software
15  *    without specific prior written permission.
16  *
17  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
18  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
19  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
20  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
21  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
22  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
23  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
24  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
25  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
26  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
27  * SUCH DAMAGE.
28  */
29 
30 #ifndef lint
31 static const char copyright[] =
32 "@(#) Copyright (c) 1983, 1993\n\
33 	The Regents of the University of California.  All rights reserved.\n";
34 #endif /* not lint */
35 
36 #ifndef lint
37 #if 0
38 static char sccsid[] = "@(#)tftpd.c	8.1 (Berkeley) 6/4/93";
39 #endif
40 #endif /* not lint */
41 #include <sys/cdefs.h>
42 __FBSDID("$FreeBSD$");
43 
44 /*
45  * Trivial file transfer protocol server.
46  *
47  * This version includes many modifications by Jim Guyton
48  * <guyton@rand-unix>.
49  */
50 
51 #include <sys/param.h>
52 #include <sys/ioctl.h>
53 #include <sys/stat.h>
54 #include <sys/socket.h>
55 
56 #include <netinet/in.h>
57 #include <arpa/tftp.h>
58 
59 #include <ctype.h>
60 #include <errno.h>
61 #include <fcntl.h>
62 #include <netdb.h>
63 #include <pwd.h>
64 #include <stdint.h>
65 #include <stdio.h>
66 #include <stdlib.h>
67 #include <string.h>
68 #include <syslog.h>
69 #include <tcpd.h>
70 #include <unistd.h>
71 
72 #include "tftp-file.h"
73 #include "tftp-io.h"
74 #include "tftp-utils.h"
75 #include "tftp-transfer.h"
76 #include "tftp-options.h"
77 
78 static void	tftp_wrq(int peer, char *, ssize_t);
79 static void	tftp_rrq(int peer, char *, ssize_t);
80 
81 /*
82  * Null-terminated directory prefix list for absolute pathname requests and
83  * search list for relative pathname requests.
84  *
85  * MAXDIRS should be at least as large as the number of arguments that
86  * inetd allows (currently 20).
87  */
88 #define MAXDIRS	20
89 static struct dirlist {
90 	const char	*name;
91 	int	len;
92 } dirs[MAXDIRS+1];
93 static int	suppress_naks;
94 static int	logging;
95 static int	ipchroot;
96 static int	create_new = 0;
97 static const char *newfile_format = "%Y%m%d";
98 static int	increase_name = 0;
99 static mode_t	mask = S_IWGRP | S_IWOTH;
100 
101 struct formats;
102 static void	tftp_recvfile(int peer, const char *mode);
103 static void	tftp_xmitfile(int peer, const char *mode);
104 static int	validate_access(int peer, char **, int);
105 static char	peername[NI_MAXHOST];
106 
107 static FILE *file;
108 
109 static struct formats {
110 	const char	*f_mode;
111 	int	f_convert;
112 } formats[] = {
113 	{ "netascii",	1 },
114 	{ "octet",	0 },
115 	{ NULL,		0 }
116 };
117 
118 int
119 main(int argc, char *argv[])
120 {
121 	struct tftphdr *tp;
122 	int		peer;
123 	socklen_t	peerlen, len;
124 	ssize_t		n;
125 	int		ch;
126 	char		*chroot_dir = NULL;
127 	struct passwd	*nobody;
128 	const char	*chuser = "nobody";
129 	char		recvbuffer[MAXPKTSIZE];
130 	int		allow_ro = 1, allow_wo = 1;
131 
132 	tzset();			/* syslog in localtime */
133 	acting_as_client = 0;
134 
135 	tftp_openlog("tftpd", LOG_PID | LOG_NDELAY, LOG_FTP);
136 	while ((ch = getopt(argc, argv, "cCd:F:lnoOp:s:u:U:wW")) != -1) {
137 		switch (ch) {
138 		case 'c':
139 			ipchroot = 1;
140 			break;
141 		case 'C':
142 			ipchroot = 2;
143 			break;
144 		case 'd':
145 			if (atoi(optarg) != 0)
146 				debug += atoi(optarg);
147 			else
148 				debug |= debug_finds(optarg);
149 			break;
150 		case 'F':
151 			newfile_format = optarg;
152 			break;
153 		case 'l':
154 			logging = 1;
155 			break;
156 		case 'n':
157 			suppress_naks = 1;
158 			break;
159 		case 'o':
160 			options_rfc_enabled = 0;
161 			break;
162 		case 'O':
163 			options_extra_enabled = 0;
164 			break;
165 		case 'p':
166 			packetdroppercentage = atoi(optarg);
167 			tftp_log(LOG_INFO,
168 			    "Randomly dropping %d out of 100 packets",
169 			    packetdroppercentage);
170 			break;
171 		case 's':
172 			chroot_dir = optarg;
173 			break;
174 		case 'u':
175 			chuser = optarg;
176 			break;
177 		case 'U':
178 			mask = strtol(optarg, NULL, 0);
179 			break;
180 		case 'w':
181 			create_new = 1;
182 			break;
183 		case 'W':
184 			create_new = 1;
185 			increase_name = 1;
186 			break;
187 		default:
188 			tftp_log(LOG_WARNING,
189 				"ignoring unknown option -%c", ch);
190 		}
191 	}
192 	if (optind < argc) {
193 		struct dirlist *dirp;
194 
195 		/* Get list of directory prefixes. Skip relative pathnames. */
196 		for (dirp = dirs; optind < argc && dirp < &dirs[MAXDIRS];
197 		     optind++) {
198 			if (argv[optind][0] == '/') {
199 				dirp->name = argv[optind];
200 				dirp->len  = strlen(dirp->name);
201 				dirp++;
202 			}
203 		}
204 	}
205 	else if (chroot_dir) {
206 		dirs->name = "/";
207 		dirs->len = 1;
208 	}
209 	if (ipchroot > 0 && chroot_dir == NULL) {
210 		tftp_log(LOG_ERR, "-c requires -s");
211 		exit(1);
212 	}
213 
214 	umask(mask);
215 
216 	{
217 		int on = 1;
218 		if (ioctl(0, FIONBIO, &on) < 0) {
219 			tftp_log(LOG_ERR, "ioctl(FIONBIO): %s", strerror(errno));
220 			exit(1);
221 		}
222 	}
223 
224 	/* Find out who we are talking to and what we are going to do */
225 	peerlen = sizeof(peer_sock);
226 	n = recvfrom(0, recvbuffer, MAXPKTSIZE, 0,
227 	    (struct sockaddr *)&peer_sock, &peerlen);
228 	if (n < 0) {
229 		tftp_log(LOG_ERR, "recvfrom: %s", strerror(errno));
230 		exit(1);
231 	}
232 	getnameinfo((struct sockaddr *)&peer_sock, peer_sock.ss_len,
233 	    peername, sizeof(peername), NULL, 0, NI_NUMERICHOST);
234 
235 	/*
236 	 * Now that we have read the message out of the UDP
237 	 * socket, we fork and exit.  Thus, inetd will go back
238 	 * to listening to the tftp port, and the next request
239 	 * to come in will start up a new instance of tftpd.
240 	 *
241 	 * We do this so that inetd can run tftpd in "wait" mode.
242 	 * The problem with tftpd running in "nowait" mode is that
243 	 * inetd may get one or more successful "selects" on the
244 	 * tftp port before we do our receive, so more than one
245 	 * instance of tftpd may be started up.  Worse, if tftpd
246 	 * break before doing the above "recvfrom", inetd would
247 	 * spawn endless instances, clogging the system.
248 	 */
249 	{
250 		int i, pid;
251 
252 		for (i = 1; i < 20; i++) {
253 		    pid = fork();
254 		    if (pid < 0) {
255 				sleep(i);
256 				/*
257 				 * flush out to most recently sent request.
258 				 *
259 				 * This may drop some request, but those
260 				 * will be resent by the clients when
261 				 * they timeout.  The positive effect of
262 				 * this flush is to (try to) prevent more
263 				 * than one tftpd being started up to service
264 				 * a single request from a single client.
265 				 */
266 				peerlen = sizeof peer_sock;
267 				i = recvfrom(0, recvbuffer, MAXPKTSIZE, 0,
268 				    (struct sockaddr *)&peer_sock, &peerlen);
269 				if (i > 0) {
270 					n = i;
271 				}
272 		    } else {
273 				break;
274 		    }
275 		}
276 		if (pid < 0) {
277 			tftp_log(LOG_ERR, "fork: %s", strerror(errno));
278 			exit(1);
279 		} else if (pid != 0) {
280 			exit(0);
281 		}
282 	}
283 
284 	/*
285 	 * See if the client is allowed to talk to me.
286 	 * (This needs to be done before the chroot())
287 	 */
288 	{
289 		struct request_info req;
290 
291 		request_init(&req, RQ_CLIENT_ADDR, peername, 0);
292 		request_set(&req, RQ_DAEMON, "tftpd", 0);
293 
294 		if (hosts_access(&req) == 0) {
295 			if (debug&DEBUG_ACCESS)
296 				tftp_log(LOG_WARNING,
297 				    "Access denied by 'tftpd' entry "
298 				    "in /etc/hosts.allow");
299 
300 			/*
301 			 * Full access might be disabled, but maybe the
302 			 * client is allowed to do read-only access.
303 			 */
304 			request_set(&req, RQ_DAEMON, "tftpd-ro", 0);
305 			allow_ro = hosts_access(&req);
306 
307 			request_set(&req, RQ_DAEMON, "tftpd-wo", 0);
308 			allow_wo = hosts_access(&req);
309 
310 			if (allow_ro == 0 && allow_wo == 0) {
311 				tftp_log(LOG_WARNING,
312 				    "Unauthorized access from %s", peername);
313 				exit(1);
314 			}
315 
316 			if (debug&DEBUG_ACCESS) {
317 				if (allow_ro)
318 					tftp_log(LOG_WARNING,
319 					    "But allowed readonly access "
320 					    "via 'tftpd-ro' entry");
321 				if (allow_wo)
322 					tftp_log(LOG_WARNING,
323 					    "But allowed writeonly access "
324 					    "via 'tftpd-wo' entry");
325 			}
326 		} else
327 			if (debug&DEBUG_ACCESS)
328 				tftp_log(LOG_WARNING,
329 				    "Full access allowed"
330 				    "in /etc/hosts.allow");
331 	}
332 
333 	/*
334 	 * Since we exit here, we should do that only after the above
335 	 * recvfrom to keep inetd from constantly forking should there
336 	 * be a problem.  See the above comment about system clogging.
337 	 */
338 	if (chroot_dir) {
339 		if (ipchroot > 0) {
340 			char *tempchroot;
341 			struct stat sb;
342 			int statret;
343 			struct sockaddr_storage ss;
344 			char hbuf[NI_MAXHOST];
345 
346 			statret = -1;
347 			memcpy(&ss, &peer_sock, peer_sock.ss_len);
348 			unmappedaddr((struct sockaddr_in6 *)&ss);
349 			getnameinfo((struct sockaddr *)&ss, ss.ss_len,
350 				    hbuf, sizeof(hbuf), NULL, 0,
351 				    NI_NUMERICHOST);
352 			asprintf(&tempchroot, "%s/%s", chroot_dir, hbuf);
353 			if (ipchroot == 2)
354 				statret = stat(tempchroot, &sb);
355 			if (ipchroot == 1 ||
356 			    (statret == 0 && (sb.st_mode & S_IFDIR)))
357 				chroot_dir = tempchroot;
358 		}
359 		/* Must get this before chroot because /etc might go away */
360 		if ((nobody = getpwnam(chuser)) == NULL) {
361 			tftp_log(LOG_ERR, "%s: no such user", chuser);
362 			exit(1);
363 		}
364 		if (chroot(chroot_dir)) {
365 			tftp_log(LOG_ERR, "chroot: %s: %s",
366 			    chroot_dir, strerror(errno));
367 			exit(1);
368 		}
369 		chdir("/");
370 		setgroups(1, &nobody->pw_gid);
371 		if (setuid(nobody->pw_uid) != 0) {
372 			tftp_log(LOG_ERR, "setuid failed");
373 			exit(1);
374 		}
375 	}
376 
377 	len = sizeof(me_sock);
378 	if (getsockname(0, (struct sockaddr *)&me_sock, &len) == 0) {
379 		switch (me_sock.ss_family) {
380 		case AF_INET:
381 			((struct sockaddr_in *)&me_sock)->sin_port = 0;
382 			break;
383 		case AF_INET6:
384 			((struct sockaddr_in6 *)&me_sock)->sin6_port = 0;
385 			break;
386 		default:
387 			/* unsupported */
388 			break;
389 		}
390 	} else {
391 		memset(&me_sock, 0, sizeof(me_sock));
392 		me_sock.ss_family = peer_sock.ss_family;
393 		me_sock.ss_len = peer_sock.ss_len;
394 	}
395 	close(0);
396 	close(1);
397 	peer = socket(peer_sock.ss_family, SOCK_DGRAM, 0);
398 	if (peer < 0) {
399 		tftp_log(LOG_ERR, "socket: %s", strerror(errno));
400 		exit(1);
401 	}
402 	if (bind(peer, (struct sockaddr *)&me_sock, me_sock.ss_len) < 0) {
403 		tftp_log(LOG_ERR, "bind: %s", strerror(errno));
404 		exit(1);
405 	}
406 
407 	tp = (struct tftphdr *)recvbuffer;
408 	tp->th_opcode = ntohs(tp->th_opcode);
409 	if (tp->th_opcode == RRQ) {
410 		if (allow_ro)
411 			tftp_rrq(peer, tp->th_stuff, n - 1);
412 		else {
413 			tftp_log(LOG_WARNING,
414 			    "%s read access denied", peername);
415 			exit(1);
416 		}
417 	}
418 	if (tp->th_opcode == WRQ) {
419 		if (allow_wo)
420 			tftp_wrq(peer, tp->th_stuff, n - 1);
421 		else {
422 			tftp_log(LOG_WARNING,
423 			    "%s write access denied", peername);
424 			exit(1);
425 		}
426 	}
427 	exit(1);
428 }
429 
430 static void
431 reduce_path(char *fn)
432 {
433 	char *slash, *ptr;
434 
435 	/* Reduce all "/+./" to "/" (just in case we've got "/./../" later */
436 	while ((slash = strstr(fn, "/./")) != NULL) {
437 		for (ptr = slash; ptr > fn && ptr[-1] == '/'; ptr--)
438 			;
439 		slash += 2;
440 		while (*slash)
441 			*++ptr = *++slash;
442 	}
443 
444 	/* Now reduce all "/something/+../" to "/" */
445 	while ((slash = strstr(fn, "/../")) != NULL) {
446 		if (slash == fn)
447 			break;
448 		for (ptr = slash; ptr > fn && ptr[-1] == '/'; ptr--)
449 			;
450 		for (ptr--; ptr >= fn; ptr--)
451 			if (*ptr == '/')
452 				break;
453 		if (ptr < fn)
454 			break;
455 		slash += 3;
456 		while (*slash)
457 			*++ptr = *++slash;
458 	}
459 }
460 
461 static char *
462 parse_header(int peer, char *recvbuffer, ssize_t size,
463 	char **filename, char **mode)
464 {
465 	char	*cp;
466 	int	i;
467 	struct formats *pf;
468 
469 	*mode = NULL;
470 	cp = recvbuffer;
471 
472 	i = get_field(peer, recvbuffer, size);
473 	if (i >= PATH_MAX) {
474 		tftp_log(LOG_ERR, "Bad option - filename too long");
475 		send_error(peer, EBADOP);
476 		exit(1);
477 	}
478 	*filename = recvbuffer;
479 	tftp_log(LOG_INFO, "Filename: '%s'", *filename);
480 	cp += i;
481 
482 	i = get_field(peer, cp, size);
483 	*mode = cp;
484 	cp += i;
485 
486 	/* Find the file transfer mode */
487 	for (cp = *mode; *cp; cp++)
488 		if (isupper(*cp))
489 			*cp = tolower(*cp);
490 	for (pf = formats; pf->f_mode; pf++)
491 		if (strcmp(pf->f_mode, *mode) == 0)
492 			break;
493 	if (pf->f_mode == NULL) {
494 		tftp_log(LOG_ERR,
495 		    "Bad option - Unknown transfer mode (%s)", *mode);
496 		send_error(peer, EBADOP);
497 		exit(1);
498 	}
499 	tftp_log(LOG_INFO, "Mode: '%s'", *mode);
500 
501 	return (cp + 1);
502 }
503 
504 /*
505  * WRQ - receive a file from the client
506  */
507 void
508 tftp_wrq(int peer, char *recvbuffer, ssize_t size)
509 {
510 	char *cp;
511 	int has_options = 0, ecode;
512 	char *filename, *mode;
513 	char fnbuf[PATH_MAX];
514 
515 	cp = parse_header(peer, recvbuffer, size, &filename, &mode);
516 	size -= (cp - recvbuffer) + 1;
517 
518 	strcpy(fnbuf, filename);
519 	reduce_path(fnbuf);
520 	filename = fnbuf;
521 
522 	if (size > 0) {
523 		if (options_rfc_enabled)
524 			has_options = !parse_options(peer, cp, size);
525 		else
526 			tftp_log(LOG_INFO, "Options found but not enabled");
527 	}
528 
529 	ecode = validate_access(peer, &filename, WRQ);
530 	if (ecode == 0) {
531 		if (has_options)
532 			send_oack(peer);
533 		else
534 			send_ack(peer, 0);
535 	}
536 	if (logging) {
537 		tftp_log(LOG_INFO, "%s: write request for %s: %s", peername,
538 			    filename, errtomsg(ecode));
539 	}
540 
541 	tftp_recvfile(peer, mode);
542 	exit(0);
543 }
544 
545 /*
546  * RRQ - send a file to the client
547  */
548 void
549 tftp_rrq(int peer, char *recvbuffer, ssize_t size)
550 {
551 	char *cp;
552 	int has_options = 0, ecode;
553 	char *filename, *mode;
554 	char	fnbuf[PATH_MAX];
555 
556 	cp = parse_header(peer, recvbuffer, size, &filename, &mode);
557 	size -= (cp - recvbuffer) + 1;
558 
559 	strcpy(fnbuf, filename);
560 	reduce_path(fnbuf);
561 	filename = fnbuf;
562 
563 	if (size > 0) {
564 		if (options_rfc_enabled)
565 			has_options = !parse_options(peer, cp, size);
566 		else
567 			tftp_log(LOG_INFO, "Options found but not enabled");
568 	}
569 
570 	ecode = validate_access(peer, &filename, RRQ);
571 	if (ecode == 0) {
572 		if (has_options) {
573 			int n;
574 			char lrecvbuffer[MAXPKTSIZE];
575 			struct tftphdr *rp = (struct tftphdr *)lrecvbuffer;
576 
577 			send_oack(peer);
578 			n = receive_packet(peer, lrecvbuffer, MAXPKTSIZE,
579 				NULL, timeoutpacket);
580 			if (n < 0) {
581 				if (debug&DEBUG_SIMPLE)
582 					tftp_log(LOG_DEBUG, "Aborting: %s",
583 					    rp_strerror(n));
584 				return;
585 			}
586 			if (rp->th_opcode != ACK) {
587 				if (debug&DEBUG_SIMPLE)
588 					tftp_log(LOG_DEBUG,
589 					    "Expected ACK, got %s on OACK",
590 					    packettype(rp->th_opcode));
591 				return;
592 			}
593 		}
594 	}
595 
596 	if (logging)
597 		tftp_log(LOG_INFO, "%s: read request for %s: %s", peername,
598 			    filename, errtomsg(ecode));
599 
600 	if (ecode) {
601 		/*
602 		 * Avoid storms of naks to a RRQ broadcast for a relative
603 		 * bootfile pathname from a diskless Sun.
604 		 */
605 		if (suppress_naks && *filename != '/' && ecode == ENOTFOUND)
606 			exit(0);
607 		send_error(peer, ecode);
608 		exit(1);
609 	}
610 	tftp_xmitfile(peer, mode);
611 }
612 
613 /*
614  * Find the next value for YYYYMMDD.nn when the file to be written should
615  * be unique. Due to the limitations of nn, we will fail if nn reaches 100.
616  * Besides, that is four updates per hour on a file, which is kind of
617  * execessive anyway.
618  */
619 static int
620 find_next_name(char *filename, int *fd)
621 {
622 	int i;
623 	time_t tval;
624 	size_t len;
625 	struct tm lt;
626 	char yyyymmdd[MAXPATHLEN];
627 	char newname[MAXPATHLEN];
628 
629 	/* Create the YYYYMMDD part of the filename */
630 	time(&tval);
631 	lt = *localtime(&tval);
632 	len = strftime(yyyymmdd, sizeof(yyyymmdd), newfile_format, &lt);
633 	if (len == 0) {
634 		syslog(LOG_WARNING,
635 			"Filename suffix too long (%d characters maximum)",
636 			MAXPATHLEN);
637 		return (EACCESS);
638 	}
639 
640 	/* Make sure the new filename is not too long */
641 	if (strlen(filename) > MAXPATHLEN - len - 5) {
642 		syslog(LOG_WARNING,
643 			"Filename too long (%zd characters, %zd maximum)",
644 			strlen(filename), MAXPATHLEN - len - 5);
645 		return (EACCESS);
646 	}
647 
648 	/* Find the first file which doesn't exist */
649 	for (i = 0; i < 100; i++) {
650 		sprintf(newname, "%s.%s.%02d", filename, yyyymmdd, i);
651 		*fd = open(newname,
652 		    O_WRONLY | O_CREAT | O_EXCL,
653 		    S_IRUSR | S_IWUSR | S_IRGRP |
654 		    S_IWGRP | S_IROTH | S_IWOTH);
655 		if (*fd > 0)
656 			return 0;
657 	}
658 
659 	return (EEXIST);
660 }
661 
662 /*
663  * Validate file access.  Since we
664  * have no uid or gid, for now require
665  * file to exist and be publicly
666  * readable/writable.
667  * If we were invoked with arguments
668  * from inetd then the file must also be
669  * in one of the given directory prefixes.
670  * Note also, full path name must be
671  * given as we have no login directory.
672  */
673 int
674 validate_access(int peer, char **filep, int mode)
675 {
676 	struct stat stbuf;
677 	int	fd;
678 	int	error;
679 	struct dirlist *dirp;
680 	static char pathname[MAXPATHLEN];
681 	char *filename = *filep;
682 
683 	/*
684 	 * Prevent tricksters from getting around the directory restrictions
685 	 */
686 	if (strstr(filename, "/../"))
687 		return (EACCESS);
688 
689 	if (*filename == '/') {
690 		/*
691 		 * Allow the request if it's in one of the approved locations.
692 		 * Special case: check the null prefix ("/") by looking
693 		 * for length = 1 and relying on the arg. processing that
694 		 * it's a /.
695 		 */
696 		for (dirp = dirs; dirp->name != NULL; dirp++) {
697 			if (dirp->len == 1 ||
698 			    (!strncmp(filename, dirp->name, dirp->len) &&
699 			     filename[dirp->len] == '/'))
700 				    break;
701 		}
702 		/* If directory list is empty, allow access to any file */
703 		if (dirp->name == NULL && dirp != dirs)
704 			return (EACCESS);
705 		if (stat(filename, &stbuf) < 0)
706 			return (errno == ENOENT ? ENOTFOUND : EACCESS);
707 		if ((stbuf.st_mode & S_IFMT) != S_IFREG)
708 			return (ENOTFOUND);
709 		if (mode == RRQ) {
710 			if ((stbuf.st_mode & S_IROTH) == 0)
711 				return (EACCESS);
712 		} else {
713 			if ((stbuf.st_mode & S_IWOTH) == 0)
714 				return (EACCESS);
715 		}
716 	} else {
717 		int err;
718 
719 		/*
720 		 * Relative file name: search the approved locations for it.
721 		 * Don't allow write requests that avoid directory
722 		 * restrictions.
723 		 */
724 
725 		if (!strncmp(filename, "../", 3))
726 			return (EACCESS);
727 
728 		/*
729 		 * If the file exists in one of the directories and isn't
730 		 * readable, continue looking. However, change the error code
731 		 * to give an indication that the file exists.
732 		 */
733 		err = ENOTFOUND;
734 		for (dirp = dirs; dirp->name != NULL; dirp++) {
735 			snprintf(pathname, sizeof(pathname), "%s/%s",
736 				dirp->name, filename);
737 			if (stat(pathname, &stbuf) == 0 &&
738 			    (stbuf.st_mode & S_IFMT) == S_IFREG) {
739 				if ((stbuf.st_mode & S_IROTH) != 0) {
740 					break;
741 				}
742 				err = EACCESS;
743 			}
744 		}
745 		if (dirp->name != NULL)
746 			*filep = filename = pathname;
747 		else if (mode == RRQ)
748 			return (err);
749 	}
750 
751 	/*
752 	 * This option is handled here because it (might) require(s) the
753 	 * size of the file.
754 	 */
755 	option_tsize(peer, NULL, mode, &stbuf);
756 
757 	if (mode == RRQ)
758 		fd = open(filename, O_RDONLY);
759 	else {
760 		if (create_new) {
761 			if (increase_name) {
762 				error = find_next_name(filename, &fd);
763 				if (error > 0)
764 					return (error + 100);
765 			} else
766 				fd = open(filename,
767 				    O_WRONLY | O_TRUNC | O_CREAT,
768 				    S_IRUSR | S_IWUSR | S_IRGRP |
769 				    S_IWGRP | S_IROTH | S_IWOTH );
770 		} else
771 			fd = open(filename, O_WRONLY | O_TRUNC);
772 	}
773 	if (fd < 0)
774 		return (errno + 100);
775 	file = fdopen(fd, (mode == RRQ)? "r":"w");
776 	if (file == NULL) {
777 		close(fd);
778 		return (errno + 100);
779 	}
780 	return (0);
781 }
782 
783 static void
784 tftp_xmitfile(int peer, const char *mode)
785 {
786 	uint16_t block;
787 	time_t now;
788 	struct tftp_stats ts;
789 
790 	now = time(NULL);
791 	if (debug&DEBUG_SIMPLE)
792 		tftp_log(LOG_DEBUG, "Transmitting file");
793 
794 	read_init(0, file, mode);
795 	block = 1;
796 	tftp_send(peer, &block, &ts);
797 	read_close();
798 	if (debug&DEBUG_SIMPLE)
799 		tftp_log(LOG_INFO, "Sent %jd bytes in %jd seconds",
800 		    (intmax_t)ts.amount, (intmax_t)time(NULL) - now);
801 }
802 
803 static void
804 tftp_recvfile(int peer, const char *mode)
805 {
806 	uint16_t block;
807 	struct timeval now1, now2;
808 	struct tftp_stats ts;
809 
810 	gettimeofday(&now1, NULL);
811 	if (debug&DEBUG_SIMPLE)
812 		tftp_log(LOG_DEBUG, "Receiving file");
813 
814 	write_init(0, file, mode);
815 
816 	block = 0;
817 	tftp_receive(peer, &block, &ts, NULL, 0);
818 
819 	write_close();
820 	gettimeofday(&now2, NULL);
821 
822 	if (debug&DEBUG_SIMPLE) {
823 		double f;
824 		if (now1.tv_usec > now2.tv_usec) {
825 			now2.tv_usec += 1000000;
826 			now2.tv_sec--;
827 		}
828 
829 		f = now2.tv_sec - now1.tv_sec +
830 		    (now2.tv_usec - now1.tv_usec) / 100000.0;
831 		tftp_log(LOG_INFO,
832 		    "Download of %jd bytes in %d blocks completed after %0.1f seconds\n",
833 		    (intmax_t)ts.amount, block, f);
834 	}
835 
836 	return;
837 }
838