xref: /freebsd/libexec/tftpd/tftpd.c (revision ec965063070e5753c166cf592c9336444b74720a)
1 /*-
2  * SPDX-License-Identifier: BSD-3-Clause
3  *
4  * Copyright (c) 1983, 1993
5  *	The Regents of the University of California.  All rights reserved.
6  *
7  * Redistribution and use in source and binary forms, with or without
8  * modification, are permitted provided that the following conditions
9  * are met:
10  * 1. Redistributions of source code must retain the above copyright
11  *    notice, this list of conditions and the following disclaimer.
12  * 2. Redistributions in binary form must reproduce the above copyright
13  *    notice, this list of conditions and the following disclaimer in the
14  *    documentation and/or other materials provided with the distribution.
15  * 3. Neither the name of the University nor the names of its contributors
16  *    may be used to endorse or promote products derived from this software
17  *    without specific prior written permission.
18  *
19  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
20  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
21  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
22  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
23  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
24  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
25  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
26  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
27  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
28  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
29  * SUCH DAMAGE.
30  */
31 
32 #ifndef lint
33 static const char copyright[] =
34 "@(#) Copyright (c) 1983, 1993\n\
35 	The Regents of the University of California.  All rights reserved.\n";
36 #endif /* not lint */
37 
38 #ifndef lint
39 #if 0
40 static char sccsid[] = "@(#)tftpd.c	8.1 (Berkeley) 6/4/93";
41 #endif
42 #endif /* not lint */
43 #include <sys/cdefs.h>
44 __FBSDID("$FreeBSD$");
45 
46 /*
47  * Trivial file transfer protocol server.
48  *
49  * This version includes many modifications by Jim Guyton
50  * <guyton@rand-unix>.
51  */
52 
53 #include <sys/param.h>
54 #include <sys/ioctl.h>
55 #include <sys/socket.h>
56 #include <sys/stat.h>
57 #include <sys/time.h>
58 
59 #include <netinet/in.h>
60 #include <arpa/tftp.h>
61 
62 #include <ctype.h>
63 #include <errno.h>
64 #include <fcntl.h>
65 #include <netdb.h>
66 #include <pwd.h>
67 #include <stdint.h>
68 #include <stdio.h>
69 #include <stdlib.h>
70 #include <string.h>
71 #include <syslog.h>
72 #include <time.h>
73 #include <unistd.h>
74 
75 #include "tftp-file.h"
76 #include "tftp-io.h"
77 #include "tftp-utils.h"
78 #include "tftp-transfer.h"
79 #include "tftp-options.h"
80 
81 #ifdef	LIBWRAP
82 #include <tcpd.h>
83 #endif
84 
85 static void	tftp_wrq(int peer, char *, ssize_t);
86 static void	tftp_rrq(int peer, char *, ssize_t);
87 
88 /*
89  * Null-terminated directory prefix list for absolute pathname requests and
90  * search list for relative pathname requests.
91  *
92  * MAXDIRS should be at least as large as the number of arguments that
93  * inetd allows (currently 20).
94  */
95 #define MAXDIRS	20
96 static struct dirlist {
97 	const char	*name;
98 	int	len;
99 } dirs[MAXDIRS+1];
100 static int	suppress_naks;
101 static int	logging;
102 static int	ipchroot;
103 static int	create_new = 0;
104 static const char *newfile_format = "%Y%m%d";
105 static int	increase_name = 0;
106 static mode_t	mask = S_IWGRP | S_IWOTH;
107 
108 struct formats;
109 static void	tftp_recvfile(int peer, const char *mode);
110 static void	tftp_xmitfile(int peer, const char *mode);
111 static int	validate_access(int peer, char **, int);
112 static char	peername[NI_MAXHOST];
113 
114 static FILE *file;
115 
116 static struct formats {
117 	const char	*f_mode;
118 	int	f_convert;
119 } formats[] = {
120 	{ "netascii",	1 },
121 	{ "octet",	0 },
122 	{ NULL,		0 }
123 };
124 
125 int
126 main(int argc, char *argv[])
127 {
128 	struct tftphdr *tp;
129 	int		peer;
130 	socklen_t	peerlen, len;
131 	ssize_t		n;
132 	int		ch;
133 	char		*chroot_dir = NULL;
134 	struct passwd	*nobody;
135 	const char	*chuser = "nobody";
136 	char		recvbuffer[MAXPKTSIZE];
137 	int		allow_ro = 1, allow_wo = 1;
138 
139 	tzset();			/* syslog in localtime */
140 	acting_as_client = 0;
141 
142 	tftp_openlog("tftpd", LOG_PID | LOG_NDELAY, LOG_FTP);
143 	while ((ch = getopt(argc, argv, "cCd:F:lnoOp:s:u:U:wW")) != -1) {
144 		switch (ch) {
145 		case 'c':
146 			ipchroot = 1;
147 			break;
148 		case 'C':
149 			ipchroot = 2;
150 			break;
151 		case 'd':
152 			if (atoi(optarg) != 0)
153 				debug += atoi(optarg);
154 			else
155 				debug |= debug_finds(optarg);
156 			break;
157 		case 'F':
158 			newfile_format = optarg;
159 			break;
160 		case 'l':
161 			logging = 1;
162 			break;
163 		case 'n':
164 			suppress_naks = 1;
165 			break;
166 		case 'o':
167 			options_rfc_enabled = 0;
168 			break;
169 		case 'O':
170 			options_extra_enabled = 0;
171 			break;
172 		case 'p':
173 			packetdroppercentage = atoi(optarg);
174 			tftp_log(LOG_INFO,
175 			    "Randomly dropping %d out of 100 packets",
176 			    packetdroppercentage);
177 			break;
178 		case 's':
179 			chroot_dir = optarg;
180 			break;
181 		case 'u':
182 			chuser = optarg;
183 			break;
184 		case 'U':
185 			mask = strtol(optarg, NULL, 0);
186 			break;
187 		case 'w':
188 			create_new = 1;
189 			break;
190 		case 'W':
191 			create_new = 1;
192 			increase_name = 1;
193 			break;
194 		default:
195 			tftp_log(LOG_WARNING,
196 				"ignoring unknown option -%c", ch);
197 		}
198 	}
199 	if (optind < argc) {
200 		struct dirlist *dirp;
201 
202 		/* Get list of directory prefixes. Skip relative pathnames. */
203 		for (dirp = dirs; optind < argc && dirp < &dirs[MAXDIRS];
204 		     optind++) {
205 			if (argv[optind][0] == '/') {
206 				dirp->name = argv[optind];
207 				dirp->len  = strlen(dirp->name);
208 				dirp++;
209 			}
210 		}
211 	}
212 	else if (chroot_dir) {
213 		dirs->name = "/";
214 		dirs->len = 1;
215 	}
216 	if (ipchroot > 0 && chroot_dir == NULL) {
217 		tftp_log(LOG_ERR, "-c requires -s");
218 		exit(1);
219 	}
220 
221 	umask(mask);
222 
223 	{
224 		int on = 1;
225 		if (ioctl(0, FIONBIO, &on) < 0) {
226 			tftp_log(LOG_ERR, "ioctl(FIONBIO): %s", strerror(errno));
227 			exit(1);
228 		}
229 	}
230 
231 	/* Find out who we are talking to and what we are going to do */
232 	peerlen = sizeof(peer_sock);
233 	n = recvfrom(0, recvbuffer, MAXPKTSIZE, 0,
234 	    (struct sockaddr *)&peer_sock, &peerlen);
235 	if (n < 0) {
236 		tftp_log(LOG_ERR, "recvfrom: %s", strerror(errno));
237 		exit(1);
238 	}
239 	getnameinfo((struct sockaddr *)&peer_sock, peer_sock.ss_len,
240 	    peername, sizeof(peername), NULL, 0, NI_NUMERICHOST);
241 
242 	/*
243 	 * Now that we have read the message out of the UDP
244 	 * socket, we fork and exit.  Thus, inetd will go back
245 	 * to listening to the tftp port, and the next request
246 	 * to come in will start up a new instance of tftpd.
247 	 *
248 	 * We do this so that inetd can run tftpd in "wait" mode.
249 	 * The problem with tftpd running in "nowait" mode is that
250 	 * inetd may get one or more successful "selects" on the
251 	 * tftp port before we do our receive, so more than one
252 	 * instance of tftpd may be started up.  Worse, if tftpd
253 	 * break before doing the above "recvfrom", inetd would
254 	 * spawn endless instances, clogging the system.
255 	 */
256 	{
257 		int i, pid;
258 
259 		for (i = 1; i < 20; i++) {
260 		    pid = fork();
261 		    if (pid < 0) {
262 				sleep(i);
263 				/*
264 				 * flush out to most recently sent request.
265 				 *
266 				 * This may drop some request, but those
267 				 * will be resent by the clients when
268 				 * they timeout.  The positive effect of
269 				 * this flush is to (try to) prevent more
270 				 * than one tftpd being started up to service
271 				 * a single request from a single client.
272 				 */
273 				peerlen = sizeof peer_sock;
274 				i = recvfrom(0, recvbuffer, MAXPKTSIZE, 0,
275 				    (struct sockaddr *)&peer_sock, &peerlen);
276 				if (i > 0) {
277 					n = i;
278 				}
279 		    } else {
280 				break;
281 		    }
282 		}
283 		if (pid < 0) {
284 			tftp_log(LOG_ERR, "fork: %s", strerror(errno));
285 			exit(1);
286 		} else if (pid != 0) {
287 			exit(0);
288 		}
289 	}
290 
291 #ifdef	LIBWRAP
292 	/*
293 	 * See if the client is allowed to talk to me.
294 	 * (This needs to be done before the chroot())
295 	 */
296 	{
297 		struct request_info req;
298 
299 		request_init(&req, RQ_CLIENT_ADDR, peername, 0);
300 		request_set(&req, RQ_DAEMON, "tftpd", 0);
301 
302 		if (hosts_access(&req) == 0) {
303 			if (debug & DEBUG_ACCESS)
304 				tftp_log(LOG_WARNING,
305 				    "Access denied by 'tftpd' entry "
306 				    "in /etc/hosts.allow");
307 
308 			/*
309 			 * Full access might be disabled, but maybe the
310 			 * client is allowed to do read-only access.
311 			 */
312 			request_set(&req, RQ_DAEMON, "tftpd-ro", 0);
313 			allow_ro = hosts_access(&req);
314 
315 			request_set(&req, RQ_DAEMON, "tftpd-wo", 0);
316 			allow_wo = hosts_access(&req);
317 
318 			if (allow_ro == 0 && allow_wo == 0) {
319 				tftp_log(LOG_WARNING,
320 				    "Unauthorized access from %s", peername);
321 				exit(1);
322 			}
323 
324 			if (debug & DEBUG_ACCESS) {
325 				if (allow_ro)
326 					tftp_log(LOG_WARNING,
327 					    "But allowed readonly access "
328 					    "via 'tftpd-ro' entry");
329 				if (allow_wo)
330 					tftp_log(LOG_WARNING,
331 					    "But allowed writeonly access "
332 					    "via 'tftpd-wo' entry");
333 			}
334 		} else
335 			if (debug & DEBUG_ACCESS)
336 				tftp_log(LOG_WARNING,
337 				    "Full access allowed"
338 				    "in /etc/hosts.allow");
339 	}
340 #endif
341 
342 	/*
343 	 * Since we exit here, we should do that only after the above
344 	 * recvfrom to keep inetd from constantly forking should there
345 	 * be a problem.  See the above comment about system clogging.
346 	 */
347 	if (chroot_dir) {
348 		if (ipchroot > 0) {
349 			char *tempchroot;
350 			struct stat sb;
351 			int statret;
352 			struct sockaddr_storage ss;
353 			char hbuf[NI_MAXHOST];
354 
355 			statret = -1;
356 			memcpy(&ss, &peer_sock, peer_sock.ss_len);
357 			unmappedaddr((struct sockaddr_in6 *)&ss);
358 			getnameinfo((struct sockaddr *)&ss, ss.ss_len,
359 				    hbuf, sizeof(hbuf), NULL, 0,
360 				    NI_NUMERICHOST);
361 			asprintf(&tempchroot, "%s/%s", chroot_dir, hbuf);
362 			if (ipchroot == 2)
363 				statret = stat(tempchroot, &sb);
364 			if (ipchroot == 1 ||
365 			    (statret == 0 && (sb.st_mode & S_IFDIR)))
366 				chroot_dir = tempchroot;
367 		}
368 		/* Must get this before chroot because /etc might go away */
369 		if ((nobody = getpwnam(chuser)) == NULL) {
370 			tftp_log(LOG_ERR, "%s: no such user", chuser);
371 			exit(1);
372 		}
373 		if (chroot(chroot_dir)) {
374 			tftp_log(LOG_ERR, "chroot: %s: %s",
375 			    chroot_dir, strerror(errno));
376 			exit(1);
377 		}
378 		if (chdir("/") != 0) {
379 			tftp_log(LOG_ERR, "chdir: %s", strerror(errno));
380 			exit(1);
381 		}
382 		if (setgroups(1, &nobody->pw_gid) != 0) {
383 			tftp_log(LOG_ERR, "setgroups failed");
384 			exit(1);
385 		}
386 		if (setuid(nobody->pw_uid) != 0) {
387 			tftp_log(LOG_ERR, "setuid failed");
388 			exit(1);
389 		}
390 	}
391 
392 	len = sizeof(me_sock);
393 	if (getsockname(0, (struct sockaddr *)&me_sock, &len) == 0) {
394 		switch (me_sock.ss_family) {
395 		case AF_INET:
396 			((struct sockaddr_in *)&me_sock)->sin_port = 0;
397 			break;
398 		case AF_INET6:
399 			((struct sockaddr_in6 *)&me_sock)->sin6_port = 0;
400 			break;
401 		default:
402 			/* unsupported */
403 			break;
404 		}
405 	} else {
406 		memset(&me_sock, 0, sizeof(me_sock));
407 		me_sock.ss_family = peer_sock.ss_family;
408 		me_sock.ss_len = peer_sock.ss_len;
409 	}
410 	close(0);
411 	close(1);
412 	peer = socket(peer_sock.ss_family, SOCK_DGRAM, 0);
413 	if (peer < 0) {
414 		tftp_log(LOG_ERR, "socket: %s", strerror(errno));
415 		exit(1);
416 	}
417 	if (bind(peer, (struct sockaddr *)&me_sock, me_sock.ss_len) < 0) {
418 		tftp_log(LOG_ERR, "bind: %s", strerror(errno));
419 		exit(1);
420 	}
421 
422 	tp = (struct tftphdr *)recvbuffer;
423 	tp->th_opcode = ntohs(tp->th_opcode);
424 	if (tp->th_opcode == RRQ) {
425 		if (allow_ro)
426 			tftp_rrq(peer, tp->th_stuff, n - 1);
427 		else {
428 			tftp_log(LOG_WARNING,
429 			    "%s read access denied", peername);
430 			exit(1);
431 		}
432 	} else if (tp->th_opcode == WRQ) {
433 		if (allow_wo)
434 			tftp_wrq(peer, tp->th_stuff, n - 1);
435 		else {
436 			tftp_log(LOG_WARNING,
437 			    "%s write access denied", peername);
438 			exit(1);
439 		}
440 	} else
441 		send_error(peer, EBADOP);
442 	exit(1);
443 }
444 
445 static void
446 reduce_path(char *fn)
447 {
448 	char *slash, *ptr;
449 
450 	/* Reduce all "/+./" to "/" (just in case we've got "/./../" later */
451 	while ((slash = strstr(fn, "/./")) != NULL) {
452 		for (ptr = slash; ptr > fn && ptr[-1] == '/'; ptr--)
453 			;
454 		slash += 2;
455 		while (*slash)
456 			*++ptr = *++slash;
457 	}
458 
459 	/* Now reduce all "/something/+../" to "/" */
460 	while ((slash = strstr(fn, "/../")) != NULL) {
461 		if (slash == fn)
462 			break;
463 		for (ptr = slash; ptr > fn && ptr[-1] == '/'; ptr--)
464 			;
465 		for (ptr--; ptr >= fn; ptr--)
466 			if (*ptr == '/')
467 				break;
468 		if (ptr < fn)
469 			break;
470 		slash += 3;
471 		while (*slash)
472 			*++ptr = *++slash;
473 	}
474 }
475 
476 static char *
477 parse_header(int peer, char *recvbuffer, ssize_t size,
478 	char **filename, char **mode)
479 {
480 	char	*cp;
481 	int	i;
482 	struct formats *pf;
483 
484 	*mode = NULL;
485 	cp = recvbuffer;
486 
487 	i = get_field(peer, recvbuffer, size);
488 	if (i >= PATH_MAX) {
489 		tftp_log(LOG_ERR, "Bad option - filename too long");
490 		send_error(peer, EBADOP);
491 		exit(1);
492 	}
493 	*filename = recvbuffer;
494 	tftp_log(LOG_INFO, "Filename: '%s'", *filename);
495 	cp += i;
496 
497 	i = get_field(peer, cp, size);
498 	*mode = cp;
499 	cp += i;
500 
501 	/* Find the file transfer mode */
502 	for (cp = *mode; *cp; cp++)
503 		if (isupper(*cp))
504 			*cp = tolower(*cp);
505 	for (pf = formats; pf->f_mode; pf++)
506 		if (strcmp(pf->f_mode, *mode) == 0)
507 			break;
508 	if (pf->f_mode == NULL) {
509 		tftp_log(LOG_ERR,
510 		    "Bad option - Unknown transfer mode (%s)", *mode);
511 		send_error(peer, EBADOP);
512 		exit(1);
513 	}
514 	tftp_log(LOG_INFO, "Mode: '%s'", *mode);
515 
516 	return (cp + 1);
517 }
518 
519 /*
520  * WRQ - receive a file from the client
521  */
522 void
523 tftp_wrq(int peer, char *recvbuffer, ssize_t size)
524 {
525 	char *cp;
526 	int has_options = 0, ecode;
527 	char *filename, *mode;
528 	char fnbuf[PATH_MAX];
529 
530 	cp = parse_header(peer, recvbuffer, size, &filename, &mode);
531 	size -= (cp - recvbuffer) + 1;
532 
533 	strlcpy(fnbuf, filename, sizeof(fnbuf));
534 	reduce_path(fnbuf);
535 	filename = fnbuf;
536 
537 	if (size > 0) {
538 		if (options_rfc_enabled)
539 			has_options = !parse_options(peer, cp, size);
540 		else
541 			tftp_log(LOG_INFO, "Options found but not enabled");
542 	}
543 
544 	ecode = validate_access(peer, &filename, WRQ);
545 	if (ecode == 0) {
546 		if (has_options)
547 			send_oack(peer);
548 		else
549 			send_ack(peer, 0);
550 	}
551 	if (logging) {
552 		tftp_log(LOG_INFO, "%s: write request for %s: %s", peername,
553 			    filename, errtomsg(ecode));
554 	}
555 
556 	if (ecode) {
557 		send_error(peer, ecode);
558 		exit(1);
559 	}
560 	tftp_recvfile(peer, mode);
561 	exit(0);
562 }
563 
564 /*
565  * RRQ - send a file to the client
566  */
567 void
568 tftp_rrq(int peer, char *recvbuffer, ssize_t size)
569 {
570 	char *cp;
571 	int has_options = 0, ecode;
572 	char *filename, *mode;
573 	char	fnbuf[PATH_MAX];
574 
575 	cp = parse_header(peer, recvbuffer, size, &filename, &mode);
576 	size -= (cp - recvbuffer) + 1;
577 
578 	strlcpy(fnbuf, filename, sizeof(fnbuf));
579 	reduce_path(fnbuf);
580 	filename = fnbuf;
581 
582 	if (size > 0) {
583 		if (options_rfc_enabled)
584 			has_options = !parse_options(peer, cp, size);
585 		else
586 			tftp_log(LOG_INFO, "Options found but not enabled");
587 	}
588 
589 	ecode = validate_access(peer, &filename, RRQ);
590 	if (ecode == 0) {
591 		if (has_options) {
592 			int n;
593 			char lrecvbuffer[MAXPKTSIZE];
594 			struct tftphdr *rp = (struct tftphdr *)lrecvbuffer;
595 
596 			send_oack(peer);
597 			n = receive_packet(peer, lrecvbuffer, MAXPKTSIZE,
598 				NULL, timeoutpacket);
599 			if (n < 0) {
600 				if (debug & DEBUG_SIMPLE)
601 					tftp_log(LOG_DEBUG, "Aborting: %s",
602 					    rp_strerror(n));
603 				return;
604 			}
605 			if (rp->th_opcode != ACK) {
606 				if (debug & DEBUG_SIMPLE)
607 					tftp_log(LOG_DEBUG,
608 					    "Expected ACK, got %s on OACK",
609 					    packettype(rp->th_opcode));
610 				return;
611 			}
612 		}
613 	}
614 
615 	if (logging)
616 		tftp_log(LOG_INFO, "%s: read request for %s: %s", peername,
617 			    filename, errtomsg(ecode));
618 
619 	if (ecode) {
620 		/*
621 		 * Avoid storms of naks to a RRQ broadcast for a relative
622 		 * bootfile pathname from a diskless Sun.
623 		 */
624 		if (suppress_naks && *filename != '/' && ecode == ENOTFOUND)
625 			exit(0);
626 		send_error(peer, ecode);
627 		exit(1);
628 	}
629 	tftp_xmitfile(peer, mode);
630 }
631 
632 /*
633  * Find the next value for YYYYMMDD.nn when the file to be written should
634  * be unique. Due to the limitations of nn, we will fail if nn reaches 100.
635  * Besides, that is four updates per hour on a file, which is kind of
636  * execessive anyway.
637  */
638 static int
639 find_next_name(char *filename, int *fd)
640 {
641 	int i;
642 	time_t tval;
643 	size_t len;
644 	struct tm lt;
645 	char yyyymmdd[MAXPATHLEN];
646 	char newname[MAXPATHLEN];
647 
648 	/* Create the YYYYMMDD part of the filename */
649 	time(&tval);
650 	lt = *localtime(&tval);
651 	len = strftime(yyyymmdd, sizeof(yyyymmdd), newfile_format, &lt);
652 	if (len == 0) {
653 		syslog(LOG_WARNING,
654 			"Filename suffix too long (%d characters maximum)",
655 			MAXPATHLEN);
656 		return (EACCESS);
657 	}
658 
659 	/* Make sure the new filename is not too long */
660 	if (strlen(filename) > MAXPATHLEN - len - 5) {
661 		syslog(LOG_WARNING,
662 			"Filename too long (%zd characters, %zd maximum)",
663 			strlen(filename), MAXPATHLEN - len - 5);
664 		return (EACCESS);
665 	}
666 
667 	/* Find the first file which doesn't exist */
668 	for (i = 0; i < 100; i++) {
669 		sprintf(newname, "%s.%s.%02d", filename, yyyymmdd, i);
670 		*fd = open(newname,
671 		    O_WRONLY | O_CREAT | O_EXCL,
672 		    S_IRUSR | S_IWUSR | S_IRGRP |
673 		    S_IWGRP | S_IROTH | S_IWOTH);
674 		if (*fd > 0)
675 			return 0;
676 	}
677 
678 	return (EEXIST);
679 }
680 
681 /*
682  * Validate file access.  Since we
683  * have no uid or gid, for now require
684  * file to exist and be publicly
685  * readable/writable.
686  * If we were invoked with arguments
687  * from inetd then the file must also be
688  * in one of the given directory prefixes.
689  * Note also, full path name must be
690  * given as we have no login directory.
691  */
692 int
693 validate_access(int peer, char **filep, int mode)
694 {
695 	struct stat stbuf;
696 	int	fd;
697 	int	error;
698 	struct dirlist *dirp;
699 	static char pathname[MAXPATHLEN];
700 	char *filename = *filep;
701 
702 	/*
703 	 * Prevent tricksters from getting around the directory restrictions
704 	 */
705 	if (strstr(filename, "/../"))
706 		return (EACCESS);
707 
708 	if (*filename == '/') {
709 		/*
710 		 * Allow the request if it's in one of the approved locations.
711 		 * Special case: check the null prefix ("/") by looking
712 		 * for length = 1 and relying on the arg. processing that
713 		 * it's a /.
714 		 */
715 		for (dirp = dirs; dirp->name != NULL; dirp++) {
716 			if (dirp->len == 1 ||
717 			    (!strncmp(filename, dirp->name, dirp->len) &&
718 			     filename[dirp->len] == '/'))
719 				    break;
720 		}
721 		/* If directory list is empty, allow access to any file */
722 		if (dirp->name == NULL && dirp != dirs)
723 			return (EACCESS);
724 		if (stat(filename, &stbuf) < 0)
725 			return (errno == ENOENT ? ENOTFOUND : EACCESS);
726 		if ((stbuf.st_mode & S_IFMT) != S_IFREG)
727 			return (ENOTFOUND);
728 		if (mode == RRQ) {
729 			if ((stbuf.st_mode & S_IROTH) == 0)
730 				return (EACCESS);
731 		} else {
732 			if ((stbuf.st_mode & S_IWOTH) == 0)
733 				return (EACCESS);
734 		}
735 	} else {
736 		int err;
737 
738 		/*
739 		 * Relative file name: search the approved locations for it.
740 		 * Don't allow write requests that avoid directory
741 		 * restrictions.
742 		 */
743 
744 		if (!strncmp(filename, "../", 3))
745 			return (EACCESS);
746 
747 		/*
748 		 * If the file exists in one of the directories and isn't
749 		 * readable, continue looking. However, change the error code
750 		 * to give an indication that the file exists.
751 		 */
752 		err = ENOTFOUND;
753 		for (dirp = dirs; dirp->name != NULL; dirp++) {
754 			snprintf(pathname, sizeof(pathname), "%s/%s",
755 				dirp->name, filename);
756 			if (stat(pathname, &stbuf) == 0 &&
757 			    (stbuf.st_mode & S_IFMT) == S_IFREG) {
758 				if (mode == RRQ) {
759 					if ((stbuf.st_mode & S_IROTH) != 0)
760 						break;
761 				} else {
762 					if ((stbuf.st_mode & S_IWOTH) != 0)
763 						break;
764 				}
765 				err = EACCESS;
766 			}
767 		}
768 		if (dirp->name != NULL)
769 			*filep = filename = pathname;
770 		else if (mode == RRQ)
771 			return (err);
772 		else if (err != ENOTFOUND || !create_new)
773 			return (err);
774 	}
775 
776 	/*
777 	 * This option is handled here because it (might) require(s) the
778 	 * size of the file.
779 	 */
780 	option_tsize(peer, NULL, mode, &stbuf);
781 
782 	if (mode == RRQ)
783 		fd = open(filename, O_RDONLY);
784 	else {
785 		if (create_new) {
786 			if (increase_name) {
787 				error = find_next_name(filename, &fd);
788 				if (error > 0)
789 					return (error + 100);
790 			} else
791 				fd = open(filename,
792 				    O_WRONLY | O_TRUNC | O_CREAT,
793 				    S_IRUSR | S_IWUSR | S_IRGRP |
794 				    S_IWGRP | S_IROTH | S_IWOTH );
795 		} else
796 			fd = open(filename, O_WRONLY | O_TRUNC);
797 	}
798 	if (fd < 0)
799 		return (errno + 100);
800 	file = fdopen(fd, (mode == RRQ)? "r":"w");
801 	if (file == NULL) {
802 		close(fd);
803 		return (errno + 100);
804 	}
805 	return (0);
806 }
807 
808 static void
809 tftp_xmitfile(int peer, const char *mode)
810 {
811 	uint16_t block;
812 	time_t now;
813 	struct tftp_stats ts;
814 
815 	memset(&ts, 0, sizeof(ts));
816 	now = time(NULL);
817 	if (debug & DEBUG_SIMPLE)
818 		tftp_log(LOG_DEBUG, "Transmitting file");
819 
820 	read_init(0, file, mode);
821 	block = 1;
822 	tftp_send(peer, &block, &ts);
823 	read_close();
824 	if (debug & DEBUG_SIMPLE)
825 		tftp_log(LOG_INFO, "Sent %jd bytes in %jd seconds",
826 		    (intmax_t)ts.amount, (intmax_t)time(NULL) - now);
827 }
828 
829 static void
830 tftp_recvfile(int peer, const char *mode)
831 {
832 	uint16_t block;
833 	struct timeval now1, now2;
834 	struct tftp_stats ts;
835 
836 	gettimeofday(&now1, NULL);
837 	if (debug & DEBUG_SIMPLE)
838 		tftp_log(LOG_DEBUG, "Receiving file");
839 
840 	write_init(0, file, mode);
841 
842 	block = 0;
843 	tftp_receive(peer, &block, &ts, NULL, 0);
844 
845 	gettimeofday(&now2, NULL);
846 
847 	if (debug & DEBUG_SIMPLE) {
848 		double f;
849 		if (now1.tv_usec > now2.tv_usec) {
850 			now2.tv_usec += 1000000;
851 			now2.tv_sec--;
852 		}
853 
854 		f = now2.tv_sec - now1.tv_sec +
855 		    (now2.tv_usec - now1.tv_usec) / 100000.0;
856 		tftp_log(LOG_INFO,
857 		    "Download of %jd bytes in %d blocks completed after %0.1f seconds\n",
858 		    (intmax_t)ts.amount, block, f);
859 	}
860 
861 	return;
862 }
863