xref: /freebsd/libexec/tftpd/tftpd.c (revision f173c2b77e0287807852bb7ba982643f33bdf8a0)
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 <unistd.h>
70 
71 #include "tftp-file.h"
72 #include "tftp-io.h"
73 #include "tftp-utils.h"
74 #include "tftp-transfer.h"
75 #include "tftp-options.h"
76 
77 #ifdef	LIBWRAP
78 #include <tcpd.h>
79 #endif
80 
81 static void	tftp_wrq(int peer, char *, ssize_t);
82 static void	tftp_rrq(int peer, char *, ssize_t);
83 
84 /*
85  * Null-terminated directory prefix list for absolute pathname requests and
86  * search list for relative pathname requests.
87  *
88  * MAXDIRS should be at least as large as the number of arguments that
89  * inetd allows (currently 20).
90  */
91 #define MAXDIRS	20
92 static struct dirlist {
93 	const char	*name;
94 	int	len;
95 } dirs[MAXDIRS+1];
96 static int	suppress_naks;
97 static int	logging;
98 static int	ipchroot;
99 static int	create_new = 0;
100 static const char *newfile_format = "%Y%m%d";
101 static int	increase_name = 0;
102 static mode_t	mask = S_IWGRP | S_IWOTH;
103 
104 struct formats;
105 static void	tftp_recvfile(int peer, const char *mode);
106 static void	tftp_xmitfile(int peer, const char *mode);
107 static int	validate_access(int peer, char **, int);
108 static char	peername[NI_MAXHOST];
109 
110 static FILE *file;
111 
112 static struct formats {
113 	const char	*f_mode;
114 	int	f_convert;
115 } formats[] = {
116 	{ "netascii",	1 },
117 	{ "octet",	0 },
118 	{ NULL,		0 }
119 };
120 
121 int
122 main(int argc, char *argv[])
123 {
124 	struct tftphdr *tp;
125 	int		peer;
126 	socklen_t	peerlen, len;
127 	ssize_t		n;
128 	int		ch;
129 	char		*chroot_dir = NULL;
130 	struct passwd	*nobody;
131 	const char	*chuser = "nobody";
132 	char		recvbuffer[MAXPKTSIZE];
133 	int		allow_ro = 1, allow_wo = 1;
134 
135 	tzset();			/* syslog in localtime */
136 	acting_as_client = 0;
137 
138 	tftp_openlog("tftpd", LOG_PID | LOG_NDELAY, LOG_FTP);
139 	while ((ch = getopt(argc, argv, "cCd:F:lnoOp:s:u:U:wW")) != -1) {
140 		switch (ch) {
141 		case 'c':
142 			ipchroot = 1;
143 			break;
144 		case 'C':
145 			ipchroot = 2;
146 			break;
147 		case 'd':
148 			if (atoi(optarg) != 0)
149 				debug += atoi(optarg);
150 			else
151 				debug |= debug_finds(optarg);
152 			break;
153 		case 'F':
154 			newfile_format = optarg;
155 			break;
156 		case 'l':
157 			logging = 1;
158 			break;
159 		case 'n':
160 			suppress_naks = 1;
161 			break;
162 		case 'o':
163 			options_rfc_enabled = 0;
164 			break;
165 		case 'O':
166 			options_extra_enabled = 0;
167 			break;
168 		case 'p':
169 			packetdroppercentage = atoi(optarg);
170 			tftp_log(LOG_INFO,
171 			    "Randomly dropping %d out of 100 packets",
172 			    packetdroppercentage);
173 			break;
174 		case 's':
175 			chroot_dir = optarg;
176 			break;
177 		case 'u':
178 			chuser = optarg;
179 			break;
180 		case 'U':
181 			mask = strtol(optarg, NULL, 0);
182 			break;
183 		case 'w':
184 			create_new = 1;
185 			break;
186 		case 'W':
187 			create_new = 1;
188 			increase_name = 1;
189 			break;
190 		default:
191 			tftp_log(LOG_WARNING,
192 				"ignoring unknown option -%c", ch);
193 		}
194 	}
195 	if (optind < argc) {
196 		struct dirlist *dirp;
197 
198 		/* Get list of directory prefixes. Skip relative pathnames. */
199 		for (dirp = dirs; optind < argc && dirp < &dirs[MAXDIRS];
200 		     optind++) {
201 			if (argv[optind][0] == '/') {
202 				dirp->name = argv[optind];
203 				dirp->len  = strlen(dirp->name);
204 				dirp++;
205 			}
206 		}
207 	}
208 	else if (chroot_dir) {
209 		dirs->name = "/";
210 		dirs->len = 1;
211 	}
212 	if (ipchroot > 0 && chroot_dir == NULL) {
213 		tftp_log(LOG_ERR, "-c requires -s");
214 		exit(1);
215 	}
216 
217 	umask(mask);
218 
219 	{
220 		int on = 1;
221 		if (ioctl(0, FIONBIO, &on) < 0) {
222 			tftp_log(LOG_ERR, "ioctl(FIONBIO): %s", strerror(errno));
223 			exit(1);
224 		}
225 	}
226 
227 	/* Find out who we are talking to and what we are going to do */
228 	peerlen = sizeof(peer_sock);
229 	n = recvfrom(0, recvbuffer, MAXPKTSIZE, 0,
230 	    (struct sockaddr *)&peer_sock, &peerlen);
231 	if (n < 0) {
232 		tftp_log(LOG_ERR, "recvfrom: %s", strerror(errno));
233 		exit(1);
234 	}
235 	getnameinfo((struct sockaddr *)&peer_sock, peer_sock.ss_len,
236 	    peername, sizeof(peername), NULL, 0, NI_NUMERICHOST);
237 
238 	/*
239 	 * Now that we have read the message out of the UDP
240 	 * socket, we fork and exit.  Thus, inetd will go back
241 	 * to listening to the tftp port, and the next request
242 	 * to come in will start up a new instance of tftpd.
243 	 *
244 	 * We do this so that inetd can run tftpd in "wait" mode.
245 	 * The problem with tftpd running in "nowait" mode is that
246 	 * inetd may get one or more successful "selects" on the
247 	 * tftp port before we do our receive, so more than one
248 	 * instance of tftpd may be started up.  Worse, if tftpd
249 	 * break before doing the above "recvfrom", inetd would
250 	 * spawn endless instances, clogging the system.
251 	 */
252 	{
253 		int i, pid;
254 
255 		for (i = 1; i < 20; i++) {
256 		    pid = fork();
257 		    if (pid < 0) {
258 				sleep(i);
259 				/*
260 				 * flush out to most recently sent request.
261 				 *
262 				 * This may drop some request, but those
263 				 * will be resent by the clients when
264 				 * they timeout.  The positive effect of
265 				 * this flush is to (try to) prevent more
266 				 * than one tftpd being started up to service
267 				 * a single request from a single client.
268 				 */
269 				peerlen = sizeof peer_sock;
270 				i = recvfrom(0, recvbuffer, MAXPKTSIZE, 0,
271 				    (struct sockaddr *)&peer_sock, &peerlen);
272 				if (i > 0) {
273 					n = i;
274 				}
275 		    } else {
276 				break;
277 		    }
278 		}
279 		if (pid < 0) {
280 			tftp_log(LOG_ERR, "fork: %s", strerror(errno));
281 			exit(1);
282 		} else if (pid != 0) {
283 			exit(0);
284 		}
285 	}
286 
287 #ifdef	LIBWRAP
288 	/*
289 	 * See if the client is allowed to talk to me.
290 	 * (This needs to be done before the chroot())
291 	 */
292 	{
293 		struct request_info req;
294 
295 		request_init(&req, RQ_CLIENT_ADDR, peername, 0);
296 		request_set(&req, RQ_DAEMON, "tftpd", 0);
297 
298 		if (hosts_access(&req) == 0) {
299 			if (debug&DEBUG_ACCESS)
300 				tftp_log(LOG_WARNING,
301 				    "Access denied by 'tftpd' entry "
302 				    "in /etc/hosts.allow");
303 
304 			/*
305 			 * Full access might be disabled, but maybe the
306 			 * client is allowed to do read-only access.
307 			 */
308 			request_set(&req, RQ_DAEMON, "tftpd-ro", 0);
309 			allow_ro = hosts_access(&req);
310 
311 			request_set(&req, RQ_DAEMON, "tftpd-wo", 0);
312 			allow_wo = hosts_access(&req);
313 
314 			if (allow_ro == 0 && allow_wo == 0) {
315 				tftp_log(LOG_WARNING,
316 				    "Unauthorized access from %s", peername);
317 				exit(1);
318 			}
319 
320 			if (debug&DEBUG_ACCESS) {
321 				if (allow_ro)
322 					tftp_log(LOG_WARNING,
323 					    "But allowed readonly access "
324 					    "via 'tftpd-ro' entry");
325 				if (allow_wo)
326 					tftp_log(LOG_WARNING,
327 					    "But allowed writeonly access "
328 					    "via 'tftpd-wo' entry");
329 			}
330 		} else
331 			if (debug&DEBUG_ACCESS)
332 				tftp_log(LOG_WARNING,
333 				    "Full access allowed"
334 				    "in /etc/hosts.allow");
335 	}
336 #endif
337 
338 	/*
339 	 * Since we exit here, we should do that only after the above
340 	 * recvfrom to keep inetd from constantly forking should there
341 	 * be a problem.  See the above comment about system clogging.
342 	 */
343 	if (chroot_dir) {
344 		if (ipchroot > 0) {
345 			char *tempchroot;
346 			struct stat sb;
347 			int statret;
348 			struct sockaddr_storage ss;
349 			char hbuf[NI_MAXHOST];
350 
351 			statret = -1;
352 			memcpy(&ss, &peer_sock, peer_sock.ss_len);
353 			unmappedaddr((struct sockaddr_in6 *)&ss);
354 			getnameinfo((struct sockaddr *)&ss, ss.ss_len,
355 				    hbuf, sizeof(hbuf), NULL, 0,
356 				    NI_NUMERICHOST);
357 			asprintf(&tempchroot, "%s/%s", chroot_dir, hbuf);
358 			if (ipchroot == 2)
359 				statret = stat(tempchroot, &sb);
360 			if (ipchroot == 1 ||
361 			    (statret == 0 && (sb.st_mode & S_IFDIR)))
362 				chroot_dir = tempchroot;
363 		}
364 		/* Must get this before chroot because /etc might go away */
365 		if ((nobody = getpwnam(chuser)) == NULL) {
366 			tftp_log(LOG_ERR, "%s: no such user", chuser);
367 			exit(1);
368 		}
369 		if (chroot(chroot_dir)) {
370 			tftp_log(LOG_ERR, "chroot: %s: %s",
371 			    chroot_dir, strerror(errno));
372 			exit(1);
373 		}
374 		chdir("/");
375 		setgroups(1, &nobody->pw_gid);
376 		if (setuid(nobody->pw_uid) != 0) {
377 			tftp_log(LOG_ERR, "setuid failed");
378 			exit(1);
379 		}
380 	}
381 
382 	len = sizeof(me_sock);
383 	if (getsockname(0, (struct sockaddr *)&me_sock, &len) == 0) {
384 		switch (me_sock.ss_family) {
385 		case AF_INET:
386 			((struct sockaddr_in *)&me_sock)->sin_port = 0;
387 			break;
388 		case AF_INET6:
389 			((struct sockaddr_in6 *)&me_sock)->sin6_port = 0;
390 			break;
391 		default:
392 			/* unsupported */
393 			break;
394 		}
395 	} else {
396 		memset(&me_sock, 0, sizeof(me_sock));
397 		me_sock.ss_family = peer_sock.ss_family;
398 		me_sock.ss_len = peer_sock.ss_len;
399 	}
400 	close(0);
401 	close(1);
402 	peer = socket(peer_sock.ss_family, SOCK_DGRAM, 0);
403 	if (peer < 0) {
404 		tftp_log(LOG_ERR, "socket: %s", strerror(errno));
405 		exit(1);
406 	}
407 	if (bind(peer, (struct sockaddr *)&me_sock, me_sock.ss_len) < 0) {
408 		tftp_log(LOG_ERR, "bind: %s", strerror(errno));
409 		exit(1);
410 	}
411 
412 	tp = (struct tftphdr *)recvbuffer;
413 	tp->th_opcode = ntohs(tp->th_opcode);
414 	if (tp->th_opcode == RRQ) {
415 		if (allow_ro)
416 			tftp_rrq(peer, tp->th_stuff, n - 1);
417 		else {
418 			tftp_log(LOG_WARNING,
419 			    "%s read access denied", peername);
420 			exit(1);
421 		}
422 	}
423 	if (tp->th_opcode == WRQ) {
424 		if (allow_wo)
425 			tftp_wrq(peer, tp->th_stuff, n - 1);
426 		else {
427 			tftp_log(LOG_WARNING,
428 			    "%s write access denied", peername);
429 			exit(1);
430 		}
431 	}
432 	exit(1);
433 }
434 
435 static void
436 reduce_path(char *fn)
437 {
438 	char *slash, *ptr;
439 
440 	/* Reduce all "/+./" to "/" (just in case we've got "/./../" later */
441 	while ((slash = strstr(fn, "/./")) != NULL) {
442 		for (ptr = slash; ptr > fn && ptr[-1] == '/'; ptr--)
443 			;
444 		slash += 2;
445 		while (*slash)
446 			*++ptr = *++slash;
447 	}
448 
449 	/* Now reduce all "/something/+../" to "/" */
450 	while ((slash = strstr(fn, "/../")) != NULL) {
451 		if (slash == fn)
452 			break;
453 		for (ptr = slash; ptr > fn && ptr[-1] == '/'; ptr--)
454 			;
455 		for (ptr--; ptr >= fn; ptr--)
456 			if (*ptr == '/')
457 				break;
458 		if (ptr < fn)
459 			break;
460 		slash += 3;
461 		while (*slash)
462 			*++ptr = *++slash;
463 	}
464 }
465 
466 static char *
467 parse_header(int peer, char *recvbuffer, ssize_t size,
468 	char **filename, char **mode)
469 {
470 	char	*cp;
471 	int	i;
472 	struct formats *pf;
473 
474 	*mode = NULL;
475 	cp = recvbuffer;
476 
477 	i = get_field(peer, recvbuffer, size);
478 	if (i >= PATH_MAX) {
479 		tftp_log(LOG_ERR, "Bad option - filename too long");
480 		send_error(peer, EBADOP);
481 		exit(1);
482 	}
483 	*filename = recvbuffer;
484 	tftp_log(LOG_INFO, "Filename: '%s'", *filename);
485 	cp += i;
486 
487 	i = get_field(peer, cp, size);
488 	*mode = cp;
489 	cp += i;
490 
491 	/* Find the file transfer mode */
492 	for (cp = *mode; *cp; cp++)
493 		if (isupper(*cp))
494 			*cp = tolower(*cp);
495 	for (pf = formats; pf->f_mode; pf++)
496 		if (strcmp(pf->f_mode, *mode) == 0)
497 			break;
498 	if (pf->f_mode == NULL) {
499 		tftp_log(LOG_ERR,
500 		    "Bad option - Unknown transfer mode (%s)", *mode);
501 		send_error(peer, EBADOP);
502 		exit(1);
503 	}
504 	tftp_log(LOG_INFO, "Mode: '%s'", *mode);
505 
506 	return (cp + 1);
507 }
508 
509 /*
510  * WRQ - receive a file from the client
511  */
512 void
513 tftp_wrq(int peer, char *recvbuffer, ssize_t size)
514 {
515 	char *cp;
516 	int has_options = 0, ecode;
517 	char *filename, *mode;
518 	char fnbuf[PATH_MAX];
519 
520 	cp = parse_header(peer, recvbuffer, size, &filename, &mode);
521 	size -= (cp - recvbuffer) + 1;
522 
523 	strcpy(fnbuf, filename);
524 	reduce_path(fnbuf);
525 	filename = fnbuf;
526 
527 	if (size > 0) {
528 		if (options_rfc_enabled)
529 			has_options = !parse_options(peer, cp, size);
530 		else
531 			tftp_log(LOG_INFO, "Options found but not enabled");
532 	}
533 
534 	ecode = validate_access(peer, &filename, WRQ);
535 	if (ecode == 0) {
536 		if (has_options)
537 			send_oack(peer);
538 		else
539 			send_ack(peer, 0);
540 	}
541 	if (logging) {
542 		tftp_log(LOG_INFO, "%s: write request for %s: %s", peername,
543 			    filename, errtomsg(ecode));
544 	}
545 
546 	tftp_recvfile(peer, mode);
547 	exit(0);
548 }
549 
550 /*
551  * RRQ - send a file to the client
552  */
553 void
554 tftp_rrq(int peer, char *recvbuffer, ssize_t size)
555 {
556 	char *cp;
557 	int has_options = 0, ecode;
558 	char *filename, *mode;
559 	char	fnbuf[PATH_MAX];
560 
561 	cp = parse_header(peer, recvbuffer, size, &filename, &mode);
562 	size -= (cp - recvbuffer) + 1;
563 
564 	strcpy(fnbuf, filename);
565 	reduce_path(fnbuf);
566 	filename = fnbuf;
567 
568 	if (size > 0) {
569 		if (options_rfc_enabled)
570 			has_options = !parse_options(peer, cp, size);
571 		else
572 			tftp_log(LOG_INFO, "Options found but not enabled");
573 	}
574 
575 	ecode = validate_access(peer, &filename, RRQ);
576 	if (ecode == 0) {
577 		if (has_options) {
578 			int n;
579 			char lrecvbuffer[MAXPKTSIZE];
580 			struct tftphdr *rp = (struct tftphdr *)lrecvbuffer;
581 
582 			send_oack(peer);
583 			n = receive_packet(peer, lrecvbuffer, MAXPKTSIZE,
584 				NULL, timeoutpacket);
585 			if (n < 0) {
586 				if (debug&DEBUG_SIMPLE)
587 					tftp_log(LOG_DEBUG, "Aborting: %s",
588 					    rp_strerror(n));
589 				return;
590 			}
591 			if (rp->th_opcode != ACK) {
592 				if (debug&DEBUG_SIMPLE)
593 					tftp_log(LOG_DEBUG,
594 					    "Expected ACK, got %s on OACK",
595 					    packettype(rp->th_opcode));
596 				return;
597 			}
598 		}
599 	}
600 
601 	if (logging)
602 		tftp_log(LOG_INFO, "%s: read request for %s: %s", peername,
603 			    filename, errtomsg(ecode));
604 
605 	if (ecode) {
606 		/*
607 		 * Avoid storms of naks to a RRQ broadcast for a relative
608 		 * bootfile pathname from a diskless Sun.
609 		 */
610 		if (suppress_naks && *filename != '/' && ecode == ENOTFOUND)
611 			exit(0);
612 		send_error(peer, ecode);
613 		exit(1);
614 	}
615 	tftp_xmitfile(peer, mode);
616 }
617 
618 /*
619  * Find the next value for YYYYMMDD.nn when the file to be written should
620  * be unique. Due to the limitations of nn, we will fail if nn reaches 100.
621  * Besides, that is four updates per hour on a file, which is kind of
622  * execessive anyway.
623  */
624 static int
625 find_next_name(char *filename, int *fd)
626 {
627 	int i;
628 	time_t tval;
629 	size_t len;
630 	struct tm lt;
631 	char yyyymmdd[MAXPATHLEN];
632 	char newname[MAXPATHLEN];
633 
634 	/* Create the YYYYMMDD part of the filename */
635 	time(&tval);
636 	lt = *localtime(&tval);
637 	len = strftime(yyyymmdd, sizeof(yyyymmdd), newfile_format, &lt);
638 	if (len == 0) {
639 		syslog(LOG_WARNING,
640 			"Filename suffix too long (%d characters maximum)",
641 			MAXPATHLEN);
642 		return (EACCESS);
643 	}
644 
645 	/* Make sure the new filename is not too long */
646 	if (strlen(filename) > MAXPATHLEN - len - 5) {
647 		syslog(LOG_WARNING,
648 			"Filename too long (%zd characters, %zd maximum)",
649 			strlen(filename), MAXPATHLEN - len - 5);
650 		return (EACCESS);
651 	}
652 
653 	/* Find the first file which doesn't exist */
654 	for (i = 0; i < 100; i++) {
655 		sprintf(newname, "%s.%s.%02d", filename, yyyymmdd, i);
656 		*fd = open(newname,
657 		    O_WRONLY | O_CREAT | O_EXCL,
658 		    S_IRUSR | S_IWUSR | S_IRGRP |
659 		    S_IWGRP | S_IROTH | S_IWOTH);
660 		if (*fd > 0)
661 			return 0;
662 	}
663 
664 	return (EEXIST);
665 }
666 
667 /*
668  * Validate file access.  Since we
669  * have no uid or gid, for now require
670  * file to exist and be publicly
671  * readable/writable.
672  * If we were invoked with arguments
673  * from inetd then the file must also be
674  * in one of the given directory prefixes.
675  * Note also, full path name must be
676  * given as we have no login directory.
677  */
678 int
679 validate_access(int peer, char **filep, int mode)
680 {
681 	struct stat stbuf;
682 	int	fd;
683 	int	error;
684 	struct dirlist *dirp;
685 	static char pathname[MAXPATHLEN];
686 	char *filename = *filep;
687 
688 	/*
689 	 * Prevent tricksters from getting around the directory restrictions
690 	 */
691 	if (strstr(filename, "/../"))
692 		return (EACCESS);
693 
694 	if (*filename == '/') {
695 		/*
696 		 * Allow the request if it's in one of the approved locations.
697 		 * Special case: check the null prefix ("/") by looking
698 		 * for length = 1 and relying on the arg. processing that
699 		 * it's a /.
700 		 */
701 		for (dirp = dirs; dirp->name != NULL; dirp++) {
702 			if (dirp->len == 1 ||
703 			    (!strncmp(filename, dirp->name, dirp->len) &&
704 			     filename[dirp->len] == '/'))
705 				    break;
706 		}
707 		/* If directory list is empty, allow access to any file */
708 		if (dirp->name == NULL && dirp != dirs)
709 			return (EACCESS);
710 		if (stat(filename, &stbuf) < 0)
711 			return (errno == ENOENT ? ENOTFOUND : EACCESS);
712 		if ((stbuf.st_mode & S_IFMT) != S_IFREG)
713 			return (ENOTFOUND);
714 		if (mode == RRQ) {
715 			if ((stbuf.st_mode & S_IROTH) == 0)
716 				return (EACCESS);
717 		} else {
718 			if ((stbuf.st_mode & S_IWOTH) == 0)
719 				return (EACCESS);
720 		}
721 	} else {
722 		int err;
723 
724 		/*
725 		 * Relative file name: search the approved locations for it.
726 		 * Don't allow write requests that avoid directory
727 		 * restrictions.
728 		 */
729 
730 		if (!strncmp(filename, "../", 3))
731 			return (EACCESS);
732 
733 		/*
734 		 * If the file exists in one of the directories and isn't
735 		 * readable, continue looking. However, change the error code
736 		 * to give an indication that the file exists.
737 		 */
738 		err = ENOTFOUND;
739 		for (dirp = dirs; dirp->name != NULL; dirp++) {
740 			snprintf(pathname, sizeof(pathname), "%s/%s",
741 				dirp->name, filename);
742 			if (stat(pathname, &stbuf) == 0 &&
743 			    (stbuf.st_mode & S_IFMT) == S_IFREG) {
744 				if ((stbuf.st_mode & S_IROTH) != 0) {
745 					break;
746 				}
747 				err = EACCESS;
748 			}
749 		}
750 		if (dirp->name != NULL)
751 			*filep = filename = pathname;
752 		else if (mode == RRQ)
753 			return (err);
754 	}
755 
756 	/*
757 	 * This option is handled here because it (might) require(s) the
758 	 * size of the file.
759 	 */
760 	option_tsize(peer, NULL, mode, &stbuf);
761 
762 	if (mode == RRQ)
763 		fd = open(filename, O_RDONLY);
764 	else {
765 		if (create_new) {
766 			if (increase_name) {
767 				error = find_next_name(filename, &fd);
768 				if (error > 0)
769 					return (error + 100);
770 			} else
771 				fd = open(filename,
772 				    O_WRONLY | O_TRUNC | O_CREAT,
773 				    S_IRUSR | S_IWUSR | S_IRGRP |
774 				    S_IWGRP | S_IROTH | S_IWOTH );
775 		} else
776 			fd = open(filename, O_WRONLY | O_TRUNC);
777 	}
778 	if (fd < 0)
779 		return (errno + 100);
780 	file = fdopen(fd, (mode == RRQ)? "r":"w");
781 	if (file == NULL) {
782 		close(fd);
783 		return (errno + 100);
784 	}
785 	return (0);
786 }
787 
788 static void
789 tftp_xmitfile(int peer, const char *mode)
790 {
791 	uint16_t block;
792 	time_t now;
793 	struct tftp_stats ts;
794 
795 	now = time(NULL);
796 	if (debug&DEBUG_SIMPLE)
797 		tftp_log(LOG_DEBUG, "Transmitting file");
798 
799 	read_init(0, file, mode);
800 	block = 1;
801 	tftp_send(peer, &block, &ts);
802 	read_close();
803 	if (debug&DEBUG_SIMPLE)
804 		tftp_log(LOG_INFO, "Sent %jd bytes in %jd seconds",
805 		    (intmax_t)ts.amount, (intmax_t)time(NULL) - now);
806 }
807 
808 static void
809 tftp_recvfile(int peer, const char *mode)
810 {
811 	uint16_t block;
812 	struct timeval now1, now2;
813 	struct tftp_stats ts;
814 
815 	gettimeofday(&now1, NULL);
816 	if (debug&DEBUG_SIMPLE)
817 		tftp_log(LOG_DEBUG, "Receiving file");
818 
819 	write_init(0, file, mode);
820 
821 	block = 0;
822 	tftp_receive(peer, &block, &ts, NULL, 0);
823 
824 	write_close();
825 	gettimeofday(&now2, NULL);
826 
827 	if (debug&DEBUG_SIMPLE) {
828 		double f;
829 		if (now1.tv_usec > now2.tv_usec) {
830 			now2.tv_usec += 1000000;
831 			now2.tv_sec--;
832 		}
833 
834 		f = now2.tv_sec - now1.tv_sec +
835 		    (now2.tv_usec - now1.tv_usec) / 100000.0;
836 		tftp_log(LOG_INFO,
837 		    "Download of %jd bytes in %d blocks completed after %0.1f seconds\n",
838 		    (intmax_t)ts.amount, block, f);
839 	}
840 
841 	return;
842 }
843