1/*	$NetBSD: tftpd.c,v 1.45 2016/07/20 20:18:21 shm Exp $	*/
2
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#include <sys/cdefs.h>
33#ifndef lint
34__COPYRIGHT("@(#) Copyright (c) 1983, 1993\
35 The Regents of the University of California.  All rights reserved.");
36#if 0
37static char sccsid[] = "@(#)tftpd.c	8.1 (Berkeley) 6/4/93";
38#else
39__RCSID("$NetBSD: tftpd.c,v 1.45 2016/07/20 20:18:21 shm Exp $");
40#endif
41#endif /* not lint */
42
43/*
44 * Trivial file transfer protocol server.
45 *
46 * This version includes many modifications by Jim Guyton
47 * <guyton@rand-unix>.
48 */
49
50#include <sys/param.h>
51#include <sys/ioctl.h>
52#include <sys/stat.h>
53#include <sys/socket.h>
54
55#include <netinet/in.h>
56#include <arpa/tftp.h>
57#include <arpa/inet.h>
58
59#include <ctype.h>
60#include <errno.h>
61#include <fcntl.h>
62#include <grp.h>
63#include <netdb.h>
64#include <pwd.h>
65#include <setjmp.h>
66#include <signal.h>
67#include <stdio.h>
68#include <stdlib.h>
69#include <string.h>
70#include <syslog.h>
71#include <time.h>
72#include <unistd.h>
73
74#include "tftpsubs.h"
75
76#define	DEFAULTUSER	"nobody"
77
78#define	TIMEOUT		5
79
80static int	peer;
81static int	rexmtval = TIMEOUT;
82static int	maxtimeout = 5*TIMEOUT;
83
84static char	buf[MAXPKTSIZE];
85static char	ackbuf[PKTSIZE];
86static char	oackbuf[PKTSIZE];
87static struct	sockaddr_storage from;
88static socklen_t	fromlen;
89static int	debug;
90
91static int	tftp_opt_tsize = 0;
92static int	tftp_blksize = SEGSIZE;
93static int	tftp_tsize = 0;
94
95/*
96 * Null-terminated directory prefix list for absolute pathname requests and
97 * search list for relative pathname requests.
98 *
99 * MAXDIRS should be at least as large as the number of arguments that
100 * inetd allows (currently 20).
101 */
102#define MAXDIRS	20
103static struct dirlist {
104	char	*name;
105	int	len;
106} dirs[MAXDIRS+1];
107static int	suppress_naks;
108static int	logging;
109static int	secure;
110static char	pathsep = '\0';
111static char	*securedir;
112static int	unrestricted_writes;    /* uploaded files don't have to exist */
113static int	broadcast_client = 0; /* Some clients ack to the broadcast address */
114
115struct formats;
116
117static const char *errtomsg(int);
118static void	nak(int);
119__dead static void	tftp(struct tftphdr *, int);
120__dead static void	usage(void);
121static char	*verifyhost(struct sockaddr *);
122__dead static void	justquit(int);
123static void	recvfile(struct formats *, int, int);
124static void	sendfile(struct formats *, int, int);
125__dead static void	timer(int);
126static const char *opcode(int);
127static int	validate_access(char **, int);
128
129static struct formats {
130	const char	*f_mode;
131	int		(*f_validate)(char **, int);
132	void		(*f_send)(struct formats *, int, int);
133	void		(*f_recv)(struct formats *, int, int);
134	int		f_convert;
135} formats[] = {
136	{ "netascii",	validate_access,	sendfile,	recvfile, 1 },
137	{ "octet",	validate_access,	sendfile,	recvfile, 0 },
138	{ .f_mode = NULL }
139};
140
141static void
142usage(void)
143{
144
145	syslog(LOG_ERR,
146    "Usage: %s [-bcdln] [-g group] [-p pathsep] [-s directory] [-u user] [directory ...]",
147		    getprogname());
148	exit(1);
149}
150
151int
152main(int argc, char *argv[])
153{
154	struct sockaddr_storage me;
155	struct passwd	*pwent;
156	struct group	*grent;
157	struct tftphdr	*tp;
158	const char	*tgtuser, *tgtgroup;
159	char *ep;
160	int	n, ch, on, fd;
161	int	soopt;
162	socklen_t len;
163	uid_t	curuid, tgtuid;
164	gid_t	curgid, tgtgid;
165	long	nid;
166
167	n = 0;
168	fd = 0;
169	tzset();
170	openlog("tftpd", LOG_PID | LOG_NDELAY, LOG_DAEMON);
171	tgtuser = DEFAULTUSER;
172	tgtgroup = NULL;
173	curuid = getuid();
174	curgid = getgid();
175
176	while ((ch = getopt(argc, argv, "bcdg:lnp:s:u:")) != -1)
177		switch (ch) {
178		case 'b':
179			/*
180			 * Some clients, notably older Cisco boot loaders,
181			 * send their acknowledgements to the broadcast address
182			 * rather than the unicast address of the server.
183			 * Allow those clients to inter-operate with us.
184			 * It's worth noting that this interaction doesn't cause the
185			 * server to change where it sends the responses, meaning
186			 * servers that have this flag enabled are no more
187			 * susceptible to magnifcation DOS attacks than those
188			 * servers that don't use this flag.  This flag merely
189			 * permits the reception of acknowledgement traffic to the
190			 * broadcast address/specific port number that's being used for
191			 * this session as well as the unicast address/specific port
192			 * number for this session.  For example, if the session is
193			 * expecting acks on 192.168.1.40:50201, then this flag
194			 * would also allow acks to be returned to
195			 * 192.168.1.255:50201, assuming that 192.168.1.255 is the
196			 * broadcast address for the subnet containing 192.168.1.40.
197			 */
198			broadcast_client = 1;
199			break;
200		case 'c':
201			unrestricted_writes = 1;
202			break;
203
204		case 'd':
205			debug++;
206			break;
207
208		case 'g':
209			tgtgroup = optarg;
210			break;
211
212		case 'l':
213			logging = 1;
214			break;
215
216		case 'n':
217			suppress_naks = 1;
218			break;
219
220		case 'p':
221			if (optarg[0] == '\0' || optarg[1] != '\0')
222				usage();
223			pathsep = optarg[0];
224			break;
225
226		case 's':
227			secure = 1;
228			securedir = optarg;
229			break;
230
231		case 'u':
232			tgtuser = optarg;
233			break;
234
235		default:
236			usage();
237			break;
238		}
239
240	if (optind < argc) {
241		struct dirlist *dirp;
242
243		/* Get list of directory prefixes. Skip relative pathnames. */
244		for (dirp = dirs; optind < argc && dirp < &dirs[MAXDIRS];
245		     optind++) {
246			if (argv[optind][0] == '/') {
247				dirp->name = argv[optind];
248				dirp->len  = strlen(dirp->name);
249				dirp++;
250			}
251		}
252	}
253
254	if (*tgtuser == '\0' || (tgtgroup != NULL && *tgtgroup == '\0'))
255		usage();
256
257	nid = (strtol(tgtuser, &ep, 10));
258	if (*ep == '\0') {
259		if ((uid_t)nid > UID_MAX) {
260			syslog(LOG_ERR, "uid %ld is too large", nid);
261			exit(1);
262		}
263		pwent = getpwuid((uid_t)nid);
264	} else
265		pwent = getpwnam(tgtuser);
266	if (pwent == NULL) {
267		syslog(LOG_ERR, "unknown user `%s'", tgtuser);
268		exit(1);
269	}
270	tgtuid = pwent->pw_uid;
271	tgtgid = pwent->pw_gid;
272
273	if (tgtgroup != NULL) {
274		nid = (strtol(tgtgroup, &ep, 10));
275		if (*ep == '\0') {
276			if ((uid_t)nid > GID_MAX) {
277				syslog(LOG_ERR, "gid %ld is too large", nid);
278				exit(1);
279			}
280			grent = getgrgid((gid_t)nid);
281		} else
282			grent = getgrnam(tgtgroup);
283		if (grent != NULL)
284			tgtgid = grent->gr_gid;
285		else {
286			syslog(LOG_ERR, "unknown group `%s'", tgtgroup);
287			exit(1);
288		}
289	}
290
291	if (secure) {
292		if (chdir(securedir) < 0) {
293			syslog(LOG_ERR, "chdir %s: %m", securedir);
294			exit(1);
295		}
296		if (chroot(".")) {
297			syslog(LOG_ERR, "chroot: %m");
298			exit(1);
299		}
300	}
301
302	if (logging)
303		syslog(LOG_DEBUG, "running as user `%s' (%d), group `%s' (%d)",
304		    tgtuser, tgtuid, tgtgroup ? tgtgroup : "(unspecified)",
305		    tgtgid);
306	if (curgid != tgtgid) {
307		if (setgid(tgtgid)) {
308			syslog(LOG_ERR, "setgid to %d: %m", (int)tgtgid);
309			exit(1);
310		}
311		if (setgroups(0, NULL)) {
312			syslog(LOG_ERR, "setgroups: %m");
313			exit(1);
314		}
315	}
316
317	if (curuid != tgtuid) {
318		if (setuid(tgtuid)) {
319			syslog(LOG_ERR, "setuid to %d: %m", (int)tgtuid);
320			exit(1);
321		}
322	}
323
324	on = 1;
325	if (ioctl(fd, FIONBIO, &on) < 0) {
326		syslog(LOG_ERR, "ioctl(FIONBIO): %m");
327		exit(1);
328	}
329	fromlen = sizeof (from);
330	n = recvfrom(fd, buf, sizeof (buf), 0,
331	    (struct sockaddr *)&from, &fromlen);
332	if (n < 0) {
333		syslog(LOG_ERR, "recvfrom: %m");
334		exit(1);
335	}
336	/*
337	 * Now that we have read the message out of the UDP
338	 * socket, we fork and exit.  Thus, inetd will go back
339	 * to listening to the tftp port, and the next request
340	 * to come in will start up a new instance of tftpd.
341	 *
342	 * We do this so that inetd can run tftpd in "wait" mode.
343	 * The problem with tftpd running in "nowait" mode is that
344	 * inetd may get one or more successful "selects" on the
345	 * tftp port before we do our receive, so more than one
346	 * instance of tftpd may be started up.  Worse, if tftpd
347	 * break before doing the above "recvfrom", inetd would
348	 * spawn endless instances, clogging the system.
349	 */
350	{
351		int pid;
352		int i;
353		socklen_t j;
354
355		for (i = 1; i < 20; i++) {
356		    pid = fork();
357		    if (pid < 0) {
358				sleep(i);
359				/*
360				 * flush out to most recently sent request.
361				 *
362				 * This may drop some request, but those
363				 * will be resent by the clients when
364				 * they timeout.  The positive effect of
365				 * this flush is to (try to) prevent more
366				 * than one tftpd being started up to service
367				 * a single request from a single client.
368				 */
369				j = sizeof from;
370				i = recvfrom(fd, buf, sizeof (buf), 0,
371				    (struct sockaddr *)&from, &j);
372				if (i > 0) {
373					n = i;
374					fromlen = j;
375				}
376		    } else {
377				break;
378		    }
379		}
380		if (pid < 0) {
381			syslog(LOG_ERR, "fork: %m");
382			exit(1);
383		} else if (pid != 0) {
384			exit(0);
385		}
386	}
387
388	/*
389	 * remember what address this was sent to, so we can respond on the
390	 * same interface
391	 */
392	len = sizeof(me);
393	if (getsockname(fd, (struct sockaddr *)&me, &len) == 0) {
394		switch (me.ss_family) {
395		case AF_INET:
396			((struct sockaddr_in *)&me)->sin_port = 0;
397			break;
398		case AF_INET6:
399			((struct sockaddr_in6 *)&me)->sin6_port = 0;
400			break;
401		default:
402			/* unsupported */
403			break;
404		}
405	} else {
406		memset(&me, 0, sizeof(me));
407		me.ss_family = from.ss_family;
408		me.ss_len = from.ss_len;
409	}
410
411	alarm(0);
412	close(fd);
413	close(1);
414	peer = socket(from.ss_family, SOCK_DGRAM, 0);
415	if (peer < 0) {
416		syslog(LOG_ERR, "socket: %m");
417		exit(1);
418	}
419	if (broadcast_client) {
420		soopt = 1;
421		if (setsockopt(peer, SOL_SOCKET, SO_BROADCAST, (void *) &soopt, sizeof(soopt)) < 0) {
422			syslog(LOG_ERR, "set SO_BROADCAST: %m");
423			exit(1);
424		}
425	}
426	if (bind(peer, (struct sockaddr *)&me, me.ss_len) < 0) {
427		syslog(LOG_ERR, "bind: %m");
428		exit(1);
429	}
430	soopt = 65536;	/* larger than we'll ever need */
431	if (setsockopt(peer, SOL_SOCKET, SO_SNDBUF, (void *) &soopt, sizeof(soopt)) < 0) {
432		syslog(LOG_ERR, "set SNDBUF: %m");
433		exit(1);
434	}
435	if (setsockopt(peer, SOL_SOCKET, SO_RCVBUF, (void *) &soopt, sizeof(soopt)) < 0) {
436		syslog(LOG_ERR, "set RCVBUF: %m");
437		exit(1);
438	}
439
440	tp = (struct tftphdr *)buf;
441	tp->th_opcode = ntohs(tp->th_opcode);
442	if (tp->th_opcode == RRQ || tp->th_opcode == WRQ)
443		tftp(tp, n);
444	exit(1);
445}
446
447static int
448blk_handler(struct tftphdr *tp, const char *val, char *ack, size_t asize,
449    size_t *ackl, int *ecode)
450{
451	unsigned long bsize;
452	char *endp;
453	int l;
454
455	/*
456	 * On these failures, we could just ignore the blocksize option.
457	 * Perhaps that should be a command-line option.
458	 */
459	errno = 0;
460	bsize = strtoul(val, &endp, 10);
461	if ((bsize == ULONG_MAX && errno == ERANGE) || *endp) {
462		syslog(LOG_NOTICE, "%s: %s request for %s: "
463			"illegal value %s for blksize option",
464			verifyhost((struct sockaddr *)&from),
465			tp->th_opcode == WRQ ? "write" : "read",
466			tp->th_stuff, val);
467		*ecode = EBADOP;
468		return -1;
469	}
470	if (bsize < 8 || bsize > 65464) {
471		syslog(LOG_NOTICE, "%s: %s request for %s: "
472			"out of range value %s for blksize option",
473			verifyhost((struct sockaddr *)&from),
474			tp->th_opcode == WRQ ? "write" : "read",
475			tp->th_stuff, val);
476		*ecode = EBADOP;
477		return -1;
478	}
479
480	tftp_blksize = bsize;
481	if (asize > *ackl && (l = snprintf(ack + *ackl, asize - *ackl,
482	    "blksize%c%lu%c", 0, bsize, 0)) > 0) {
483		*ackl += l;
484	} else {
485		*ecode = EBADOP;
486		return -1;
487	}
488
489	return 0;
490}
491
492static int
493timeout_handler(struct tftphdr *tp, const char *val, char *ack, size_t asize,
494		size_t *ackl, int *ecode)
495{
496	unsigned long tout;
497	char *endp;
498	int l;
499
500	errno = 0;
501	tout = strtoul(val, &endp, 10);
502	if ((tout == ULONG_MAX && errno == ERANGE) || *endp) {
503		syslog(LOG_NOTICE, "%s: %s request for %s: "
504			"illegal value %s for timeout option",
505			verifyhost((struct sockaddr *)&from),
506			tp->th_opcode == WRQ ? "write" : "read",
507			tp->th_stuff, val);
508		*ecode = EBADOP;
509		return -1;
510	}
511	if (tout < 1 || tout > 255) {
512		syslog(LOG_NOTICE, "%s: %s request for %s: "
513			"out of range value %s for timeout option",
514			verifyhost((struct sockaddr *)&from),
515			tp->th_opcode == WRQ ? "write" : "read",
516			tp->th_stuff, val);
517		return 0;
518	}
519
520	rexmtval = tout;
521	if (asize > *ackl && (l = snprintf(ack + *ackl, asize - *ackl,
522	    "timeout%c%lu%c", 0, tout, 0)) > 0)
523		*ackl += l;
524	else
525		return -1;
526	/*
527	 * Arbitrarily pick a maximum timeout on a request to 3
528	 * retransmissions if the interval timeout is more than
529	 * one minute.  Longest possible timeout is therefore
530	 * 3 * 255 - 1, or 764 seconds.
531	 */
532	if (rexmtval > 60) {
533		maxtimeout = rexmtval * 3;
534	} else {
535		maxtimeout = rexmtval * 5;
536	}
537
538	return 0;
539}
540
541static int
542tsize_handler(struct tftphdr *tp, const char *val, char *ack, size_t asize,
543    size_t *ackl, int *ecode)
544{
545	unsigned long fsize;
546	char *endp;
547
548	/*
549	 * Maximum file even with extended tftp is 65535 blocks of
550	 * length 65464, or 4290183240 octets (4784056 less than 2^32).
551	 * unsigned long is at least 32 bits on all NetBSD archs.
552	 */
553
554	errno = 0;
555	fsize = strtoul(val, &endp, 10);
556	if ((fsize == ULONG_MAX && errno == ERANGE) || *endp) {
557		syslog(LOG_NOTICE, "%s: %s request for %s: "
558			"illegal value %s for tsize option",
559			verifyhost((struct sockaddr *)&from),
560			tp->th_opcode == WRQ ? "write" : "read",
561			tp->th_stuff, val);
562		*ecode = EBADOP;
563		return -1;
564	}
565	if (fsize > (unsigned long) 65535 * 65464) {
566		syslog(LOG_NOTICE, "%s: %s request for %s: "
567			"out of range value %s for tsize option",
568			verifyhost((struct sockaddr *)&from),
569			tp->th_opcode == WRQ ? "write" : "read",
570			tp->th_stuff, val);
571		*ecode = EBADOP;
572		return -1;
573	}
574
575	tftp_opt_tsize = 1;
576	tftp_tsize = fsize;
577	/*
578	 * We will report this later -- either replying with the fsize (WRQ)
579	 * or replying with the actual filesize (RRQ).
580	 */
581
582	return 0;
583}
584
585static const struct tftp_options {
586	const char *o_name;
587	int (*o_handler)(struct tftphdr *, const char *, char *, size_t,
588			 size_t *, int *);
589} options[] = {
590	{ "blksize", blk_handler },
591	{ "timeout", timeout_handler },
592	{ "tsize", tsize_handler },
593	{ .o_name = NULL }
594};
595
596/*
597 * Get options for an extended tftp session.  Stuff the ones we
598 * recognize in oackbuf.
599 */
600static int
601get_options(struct tftphdr *tp, char *cp, int size, char *ackb, size_t asize,
602    size_t *alen, int *ecode)
603{
604	const struct tftp_options *op;
605	char *option, *value, *endp;
606	int r, rv=0;
607
608	endp = cp + size;
609	while (cp < endp) {
610		option = cp;
611		while (*cp && cp < endp) {
612			*cp = tolower((unsigned char)*cp);
613			cp++;
614		}
615		if (*cp) {
616			/* if we have garbage at the end, just ignore it */
617			break;
618		}
619		cp++;	/* skip over NUL */
620		value = cp;
621		while (*cp && cp < endp) {
622			cp++;
623		}
624		if (*cp) {
625			/* if we have garbage at the end, just ignore it */
626			break;
627		}
628		cp++;
629		for (op = options; op->o_name; op++) {
630			if (strcmp(op->o_name, option) == 0)
631				break;
632		}
633		if (op->o_name) {
634			r = op->o_handler(tp, value, ackb, asize, alen, ecode);
635			if (r < 0) {
636				rv = -1;
637				break;
638			}
639			rv++;
640		} /* else ignore unknown options */
641	}
642
643	return rv;
644}
645
646/*
647 * Handle initial connection protocol.
648 */
649static void
650tftp(struct tftphdr *tp, int size)
651{
652	struct formats *pf;
653	char	*cp;
654	char	*filename, *mode;
655	int	 first, ecode, etftp = 0, r;
656	size_t alen;
657
658	ecode = 0;	/* XXX gcc */
659	first = 1;
660	mode = NULL;
661
662	filename = cp = tp->th_stuff;
663again:
664	while (cp < buf + size) {
665		if (*cp == '\0')
666			break;
667		cp++;
668	}
669	if (*cp != '\0') {
670		nak(EBADOP);
671		exit(1);
672	}
673	if (first) {
674		mode = ++cp;
675		first = 0;
676		goto again;
677	}
678	for (cp = mode; *cp; cp++)
679		*cp = tolower((unsigned char)*cp);
680	for (pf = formats; pf->f_mode; pf++)
681		if (strcmp(pf->f_mode, mode) == 0)
682			break;
683	if (pf->f_mode == 0) {
684		nak(EBADOP);
685		exit(1);
686	}
687	/*
688	 * cp currently points to the NUL byte following the mode.
689	 *
690	 * If we have some valid options, then let's assume that we're
691	 * now dealing with an extended tftp session.  Note that if we
692	 * don't get any options, then we *must* assume that we do not
693	 * have an extended tftp session.  If we get options, we fill
694	 * in the ack buf to acknowledge them.  If we skip that, then
695	 * the client *must* assume that we are not using an extended
696	 * session.
697	 */
698	size -= (++cp - (char *) tp);
699	if (size > 0 && *cp) {
700		alen = 2; /* Skip over opcode */
701		r = get_options(tp, cp, size, oackbuf, sizeof(oackbuf),
702		    &alen, &ecode);
703		if (r > 0) {
704			etftp = 1;
705		} else if (r < 0) {
706			nak(ecode);
707			exit(1);
708		}
709	}
710	/*
711	 * Globally replace the path separator given in the -p option
712	 * with / to cope with clients expecting a non-unix path separator.
713	 */
714	if (pathsep != '\0') {
715		for (cp = filename; *cp != '\0'; ++cp) {
716			if (*cp == pathsep)
717				*cp = '/';
718		}
719	}
720	ecode = (*pf->f_validate)(&filename, tp->th_opcode);
721	if (logging) {
722		syslog(LOG_INFO, "%s: %s request for %s: %s",
723			verifyhost((struct sockaddr *)&from),
724			tp->th_opcode == WRQ ? "write" : "read",
725			filename, errtomsg(ecode));
726	}
727	if (ecode) {
728		/*
729		 * Avoid storms of naks to a RRQ broadcast for a relative
730		 * bootfile pathname from a diskless Sun.
731		 */
732		if (suppress_naks && *filename != '/' && ecode == ENOTFOUND)
733			exit(0);
734		nak(ecode);
735		exit(1);
736	}
737
738	if (etftp) {
739		struct tftphdr *oack_h;
740
741		if (tftp_opt_tsize) {
742			int l;
743
744			if (sizeof(oackbuf) > alen &&
745			    (l = snprintf(oackbuf + alen,
746			    sizeof(oackbuf) - alen, "tsize%c%u%c", 0,
747			    tftp_tsize, 0)) > 0)
748				alen += l;
749		}
750		oack_h = (struct tftphdr *) oackbuf;
751		oack_h->th_opcode = htons(OACK);
752	}
753
754	if (tp->th_opcode == WRQ)
755		(*pf->f_recv)(pf, etftp, alen);
756	else
757		(*pf->f_send)(pf, etftp, alen);
758	exit(0);
759}
760
761
762FILE *file;
763
764/*
765 * Validate file access.  Since we
766 * have no uid or gid, for now require
767 * file to exist and be publicly
768 * readable/writable.
769 * If we were invoked with arguments
770 * from inetd then the file must also be
771 * in one of the given directory prefixes.
772 */
773int
774validate_access(char **filep, int mode)
775{
776	struct stat	 stbuf;
777	struct dirlist	*dirp;
778	static char	 pathname[MAXPATHLEN];
779	char		*filename;
780	int		 fd;
781	int		 create = 0;
782	int		 trunc = 0;
783
784	filename = *filep;
785
786	/*
787	 * Prevent tricksters from getting around the directory restrictions
788	 */
789	if (strstr(filename, "/../"))
790		return (EACCESS);
791
792	if (*filename == '/') {
793		/*
794		 * Allow the request if it's in one of the approved locations.
795		 * Special case: check the null prefix ("/") by looking
796		 * for length = 1 and relying on the arg. processing that
797		 * it's a /.
798		 */
799		for (dirp = dirs; dirp->name != NULL; dirp++) {
800			if (dirp->len == 1 ||
801			    (!strncmp(filename, dirp->name, dirp->len) &&
802			     filename[dirp->len] == '/'))
803				    break;
804		}
805		/* If directory list is empty, allow access to any file */
806		if (dirp->name == NULL && dirp != dirs)
807			return (EACCESS);
808		if (stat(filename, &stbuf) < 0)
809			return (errno == ENOENT ? ENOTFOUND : EACCESS);
810		if (!S_ISREG(stbuf.st_mode))
811			return (ENOTFOUND);
812		if (mode == RRQ) {
813			if ((stbuf.st_mode & S_IROTH) == 0)
814				return (EACCESS);
815		} else {
816			if ((stbuf.st_mode & S_IWOTH) == 0)
817				return (EACCESS);
818		}
819	} else {
820		/*
821		 * Relative file name: search the approved locations for it.
822		 */
823
824		if (!strncmp(filename, "../", 3))
825			return (EACCESS);
826
827		/*
828		 * Find the first file that exists in any of the directories,
829		 * check access on it.
830		 */
831		if (dirs[0].name != NULL) {
832			for (dirp = dirs; dirp->name != NULL; dirp++) {
833				snprintf(pathname, sizeof pathname, "%s/%s",
834				    dirp->name, filename);
835				if (stat(pathname, &stbuf) == 0 &&
836				    (stbuf.st_mode & S_IFMT) == S_IFREG) {
837					break;
838				}
839			}
840			if (dirp->name == NULL)
841				return (ENOTFOUND);
842			if (mode == RRQ && !(stbuf.st_mode & S_IROTH))
843				return (EACCESS);
844			if (mode == WRQ && !(stbuf.st_mode & S_IWOTH))
845				return (EACCESS);
846			*filep = filename = pathname;
847		} else {
848			int stat_rc;
849
850			/*
851			 * If there's no directory list, take our cue from the
852			 * absolute file request check above (*filename == '/'),
853			 * and allow access to anything.
854			 */
855			stat_rc = stat(filename, &stbuf);
856			if (mode == RRQ) {
857				/* Read request */
858				if (stat_rc < 0)
859				       return (errno == ENOENT ? ENOTFOUND : EACCESS);
860				if (!S_ISREG(stbuf.st_mode))
861				       return (ENOTFOUND);
862				if ((stbuf.st_mode & S_IROTH) == 0)
863					return (EACCESS);
864			} else {
865				if (stat_rc < 0) {
866				       /* Can't stat */
867				       if (errno == EACCES) {
868					       /* Permission denied */
869					       return EACCESS;
870				       } else {
871					       /* Not there */
872					       if (unrestricted_writes) {
873						       /* need to creat new file! */
874						       create = O_CREAT;
875					       } else {
876						       /* Permission denied */
877						       return EACCESS;
878					       }
879				       }
880				} else {
881				       /* Can stat */
882				       if ((stbuf.st_mode & S_IWOTH) == 0) {
883					       return (EACCESS);
884				       }
885				       trunc = O_TRUNC;
886				}
887			}
888			*filep = filename;
889		}
890	}
891
892	if (tftp_opt_tsize && mode == RRQ)
893		tftp_tsize = (unsigned long) stbuf.st_size;
894
895	fd = open(filename, mode == RRQ ? O_RDONLY : O_WRONLY | trunc | create,
896			0644); /* debatable */
897	if (fd < 0)
898		return (errno + 100);
899	file = fdopen(fd, (mode == RRQ)? "r":"w");
900	if (file == NULL) {
901		close(fd);
902		return (errno + 100);
903	}
904	return (0);
905}
906
907static int	timeout;
908static jmp_buf	timeoutbuf;
909
910static void
911timer(int dummy)
912{
913
914	timeout += rexmtval;
915	if (timeout >= maxtimeout)
916		exit(1);
917	longjmp(timeoutbuf, 1);
918}
919
920static const char *
921opcode(int code)
922{
923	static char obuf[64];
924
925	switch (code) {
926	case RRQ:
927		return "RRQ";
928	case WRQ:
929		return "WRQ";
930	case DATA:
931		return "DATA";
932	case ACK:
933		return "ACK";
934	case ERROR:
935		return "ERROR";
936	case OACK:
937		return "OACK";
938	default:
939		(void)snprintf(obuf, sizeof(obuf), "*code 0x%x*", code);
940		return obuf;
941	}
942}
943
944/*
945 * Send the requested file.
946 */
947static void
948sendfile(struct formats *pf, volatile int etftp, int acklength)
949{
950	volatile unsigned int block;
951	struct tftphdr	*dp;
952	struct tftphdr	*ap;    /* ack packet */
953	volatile int	 size;
954	int n;
955
956	signal(SIGALRM, timer);
957	ap = (struct tftphdr *)ackbuf;
958	if (etftp) {
959		dp = (struct tftphdr *)oackbuf;
960		size = acklength - 4;
961		block = 0;
962	} else {
963		dp = r_init();
964		size = 0;
965		block = 1;
966	}
967
968	do {
969		if (block > 0) {
970			size = readit(file, &dp, tftp_blksize, pf->f_convert);
971			if (size < 0) {
972				nak(errno + 100);
973				goto abort;
974			}
975			dp->th_opcode = htons((u_short)DATA);
976			dp->th_block = htons((u_short)block);
977		}
978		timeout = 0;
979		(void)setjmp(timeoutbuf);
980
981send_data:
982		if (!etftp && debug)
983			syslog(LOG_DEBUG, "Send DATA %u", block);
984		if ((n = sendto(peer, dp, size + 4, 0, (struct sockaddr *)&from, fromlen)) != size + 4) {
985			syslog(LOG_ERR, "tftpd: write: %m");
986			goto abort;
987		}
988		if (block)
989			read_ahead(file, tftp_blksize, pf->f_convert);
990		for ( ; ; ) {
991			alarm(rexmtval);        /* read the ack */
992			n = recvfrom(peer, ackbuf, tftp_blksize, 0,(struct sockaddr
993			*)&from, &fromlen );
994			alarm(0);
995			if (n < 0) {
996				syslog(LOG_ERR, "tftpd: read: %m");
997				goto abort;
998			}
999			ap->th_opcode = ntohs((u_short)ap->th_opcode);
1000			ap->th_block = ntohs((u_short)ap->th_block);
1001			switch (ap->th_opcode) {
1002			case ERROR:
1003				goto abort;
1004
1005			case ACK:
1006				if (etftp && ap->th_block == 0) {
1007					etftp = 0;
1008					acklength = 0;
1009					dp = r_init();
1010					goto done;
1011				}
1012				if (ap->th_block == (u_short)block)
1013					goto done;
1014				if (debug)
1015					syslog(LOG_DEBUG, "Resync ACK %u != %u",
1016					    (unsigned int)ap->th_block, block);
1017				/* Re-synchronize with the other side */
1018				(void) synchnet(peer, tftp_blksize);
1019				if (ap->th_block == (u_short)(block - 1))
1020					goto send_data;
1021				/* FALLTHROUGH */
1022			default:
1023				syslog(LOG_INFO, "Received %s in sendfile\n",
1024				    opcode(dp->th_opcode));
1025			}
1026
1027		}
1028done:
1029		if (debug)
1030			syslog(LOG_DEBUG, "Received ACK for block %u", block);
1031		if (block == UINT16_MAX && size == tftp_blksize)
1032			syslog(LOG_WARNING,
1033			    "Block number wrapped (hint: increase block size)");
1034		block++;
1035	} while (size == tftp_blksize || block == 1);
1036abort:
1037	(void) fclose(file);
1038}
1039
1040static void
1041justquit(int dummy)
1042{
1043
1044	exit(0);
1045}
1046
1047/*
1048 * Receive a file.
1049 */
1050static void
1051recvfile(struct formats *pf, volatile int etftp, volatile int acklength)
1052{
1053	volatile unsigned int block;
1054	struct tftphdr	*dp;
1055	struct tftphdr	*ap;    /* ack buffer */
1056	volatile int size;
1057	int n;
1058
1059	signal(SIGALRM, timer);
1060	dp = w_init();
1061	ap = (struct tftphdr *)oackbuf;
1062	block = 0;
1063	do {
1064		timeout = 0;
1065		if (etftp == 0) {
1066			ap = (struct tftphdr *)ackbuf;
1067			ap->th_opcode = htons((u_short)ACK);
1068			ap->th_block = htons((u_short)block);
1069			acklength = 4;
1070		}
1071		if (debug)
1072			syslog(LOG_DEBUG, "Sending ACK for block %u\n", block);
1073		if (block == UINT16_MAX)
1074			syslog(LOG_WARNING,
1075			    "Block number wrapped (hint: increase block size)");
1076		block++;
1077		(void) setjmp(timeoutbuf);
1078send_ack:
1079		ap = (struct tftphdr *) (etftp ? oackbuf : ackbuf);
1080		if (sendto(peer, ap, acklength, 0, (struct sockaddr *)&from, fromlen) != acklength) {
1081			syslog(LOG_ERR, "tftpd: write: %m");
1082			goto abort;
1083		}
1084		write_behind(file, pf->f_convert);
1085		for ( ; ; ) {
1086			alarm(rexmtval);
1087			n = recvfrom(peer, dp, tftp_blksize + 4, 0, (struct sockaddr
1088			*)&from, &fromlen);
1089			alarm(0);
1090			if (n < 0) {            /* really? */
1091				syslog(LOG_ERR, "tftpd: read: %m");
1092				goto abort;
1093			}
1094			etftp = 0;
1095			dp->th_opcode = ntohs((u_short)dp->th_opcode);
1096			dp->th_block = ntohs((u_short)dp->th_block);
1097			if (debug)
1098				syslog(LOG_DEBUG, "Received %s for block %u",
1099				    opcode(dp->th_opcode),
1100				    (unsigned int)dp->th_block);
1101
1102			switch (dp->th_opcode) {
1103			case ERROR:
1104				goto abort;
1105			case DATA:
1106				if (dp->th_block == block)
1107					goto done;   /* normal */
1108				if (debug)
1109					syslog(LOG_DEBUG, "Resync %u != %u",
1110					    (unsigned int)dp->th_block, block);
1111				/* Re-synchronize with the other side */
1112				(void) synchnet(peer, tftp_blksize);
1113				if (dp->th_block == (block-1))
1114					goto send_ack;          /* rexmit */
1115				break;
1116			default:
1117				syslog(LOG_INFO, "Received %s in recvfile\n",
1118				    opcode(dp->th_opcode));
1119				break;
1120			}
1121		}
1122done:
1123		if (debug)
1124			syslog(LOG_DEBUG, "Got block %u", block);
1125		/*  size = write(file, dp->th_data, n - 4); */
1126		size = writeit(file, &dp, n - 4, pf->f_convert);
1127		if (size != (n-4)) {                    /* ahem */
1128			if (size < 0) nak(errno + 100);
1129			else nak(ENOSPACE);
1130			goto abort;
1131		}
1132	} while (size == tftp_blksize);
1133	write_behind(file, pf->f_convert);
1134	(void) fclose(file);            /* close data file */
1135
1136	ap->th_opcode = htons((u_short)ACK);    /* send the "final" ack */
1137	ap->th_block = htons((u_short)(block));
1138	if (debug)
1139		syslog(LOG_DEBUG, "Send final ACK %u", block);
1140	(void) sendto(peer, ackbuf, 4, 0, (struct sockaddr *)&from, fromlen);
1141
1142	signal(SIGALRM, justquit);      /* just quit on timeout */
1143	alarm(rexmtval);
1144	n = recvfrom(peer, buf, sizeof (buf), 0, (struct sockaddr *)&from, &fromlen); /* normally times out and quits */
1145	alarm(0);
1146	if (n >= 4 &&                   /* if read some data */
1147	    dp->th_opcode == DATA &&    /* and got a data block */
1148	    block == dp->th_block) {	/* then my last ack was lost */
1149		(void) sendto(peer, ackbuf, 4, 0, (struct sockaddr *)&from, fromlen);     /* resend final ack */
1150	}
1151abort:
1152	return;
1153}
1154
1155const struct errmsg {
1156	int		 e_code;
1157	const char	*e_msg;
1158} errmsgs[] = {
1159	{ EUNDEF,	"Undefined error code" },
1160	{ ENOTFOUND,	"File not found" },
1161	{ EACCESS,	"Access violation" },
1162	{ ENOSPACE,	"Disk full or allocation exceeded" },
1163	{ EBADOP,	"Illegal TFTP operation" },
1164	{ EBADID,	"Unknown transfer ID" },
1165	{ EEXISTS,	"File already exists" },
1166	{ ENOUSER,	"No such user" },
1167	{ EOPTNEG,	"Option negotiation failed" },
1168	{ -1,		0 }
1169};
1170
1171static const char *
1172errtomsg(int error)
1173{
1174	static char ebuf[20];
1175	const struct errmsg *pe;
1176
1177	if (error == 0)
1178		return ("success");
1179	for (pe = errmsgs; pe->e_code >= 0; pe++)
1180		if (pe->e_code == error)
1181			return (pe->e_msg);
1182	snprintf(ebuf, sizeof(ebuf), "error %d", error);
1183	return (ebuf);
1184}
1185
1186/*
1187 * Send a nak packet (error message).
1188 * Error code passed in is one of the
1189 * standard TFTP codes, or a UNIX errno
1190 * offset by 100.
1191 */
1192static void
1193nak(int error)
1194{
1195	const struct errmsg *pe;
1196	struct tftphdr *tp;
1197	int	length;
1198	size_t	msglen;
1199
1200	tp = (struct tftphdr *)buf;
1201	tp->th_opcode = htons((u_short)ERROR);
1202	msglen = sizeof(buf) - (&tp->th_msg[0] - buf);
1203	for (pe = errmsgs; pe->e_code >= 0; pe++)
1204		if (pe->e_code == error)
1205			break;
1206	if (pe->e_code < 0) {
1207		tp->th_code = EUNDEF;   /* set 'undef' errorcode */
1208		strlcpy(tp->th_msg, strerror(error - 100), msglen);
1209	} else {
1210		tp->th_code = htons((u_short)error);
1211		strlcpy(tp->th_msg, pe->e_msg, msglen);
1212	}
1213	if (debug)
1214		syslog(LOG_DEBUG, "Send NACK %s", tp->th_msg);
1215	length = strlen(tp->th_msg);
1216	msglen = &tp->th_msg[length + 1] - buf;
1217	if (sendto(peer, buf, msglen, 0, (struct sockaddr *)&from, fromlen) != (ssize_t)msglen)
1218		syslog(LOG_ERR, "nak: %m");
1219}
1220
1221static char *
1222verifyhost(struct sockaddr *fromp)
1223{
1224	static char hbuf[MAXHOSTNAMELEN];
1225
1226	if (getnameinfo(fromp, fromp->sa_len, hbuf, sizeof(hbuf), NULL, 0, 0))
1227		strlcpy(hbuf, "?", sizeof(hbuf));
1228	return (hbuf);
1229}
1230