tftpd.c

This book was written to provide a single reference for network administration in a Linux environmen

/*
 * Copyright (c) 1983 Regents of the University of California.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *	This product includes software developed by the University of
 *	California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#ifndef lint
char copyright[] =
"@(#) Copyright (c) 1983 Regents of the University of California.\n\
 All rights reserved.\n";
#endif /* not lint */

#ifndef lint
static char sccsid[] = "@(#)tftpd.c	5.13 (Berkeley) 2/26/91";
#endif /* not lint */

/*
 * Trivial file transfer protocol server.
 *
 * This version includes many modifications by Jim Guyton <guyton@rand-unix>
 *
 * Further modifications by Markus Gutschke <[e-mail]>
 *  - RFC1782 option parsing
 *  - RFC1783 extended blocksize
 *
 * Further modifications by Gero Kuhlmann <[e-mail]>
 *  - RFC1784 filesize option
 */

#include <sys/types.h>
#include <sys/ioctl.h>
#include <sys/stat.h>
#include <signal.h>
#include <fcntl.h>

#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/tftp.h>
#include <netdb.h>

#include <setjmp.h>
#include <syslog.h>
#include <stdio.h>
#include <errno.h>
#include <ctype.h>
#include <string.h>
#include <stdlib.h>

#define	TIMEOUT		5

#ifndef OACK
#define OACK		6
#endif

#ifndef EOPTNEG
#define EOPTNEG		8
#endif

extern	int errno;
struct	sockaddr_in sockin = { AF_INET };
int	peer;
int	rexmtval = TIMEOUT;
int	maxtimeout = 5*TIMEOUT;

#define	PKTSIZE	(1432 + 4)
int     segsize = SEGSIZE;
char	buf[PKTSIZE];
char	ackbuf[PKTSIZE];
struct	sockaddr_in from;
int	fromlen;
off_t   filesize;

#define MAXARG	4
char	*dirs[MAXARG+1];

main(ac, av)
	char **av;
{
	register struct tftphdr *tp;
	register int n = 0;
	int on = 1;

	ac--; av++;
	while (ac-- > 0 && n < MAXARG)
		dirs[n++] = *av++;
	openlog("tftpd", LOG_PID, LOG_DAEMON);
	if (ioctl(0, FIONBIO, &on) < 0) {
		syslog(LOG_ERR, "ioctl(FIONBIO): %m\n");
		exit(1);
	}
	fromlen = sizeof (from);
	n = recvfrom(0, buf, segsize + 4, 0,
	    (struct sockaddr *)&from, &fromlen);
	if (n < 0) {
		syslog(LOG_ERR, "recvfrom: %m\n");
		exit(1);
	}
	/*
	 * Now that we have read the message out of the UDP
	 * socket, we fork and exit.  Thus, inetd will go back
	 * to listening to the tftp port, and the next request
	 * to come in will start up a new instance of tftpd.
	 *
	 * We do this so that inetd can run tftpd in "wait" mode.
	 * The problem with tftpd running in "nowait" mode is that
	 * inetd may get one or more successful "selects" on the
	 * tftp port before we do our receive, so more than one
	 * instance of tftpd may be started up.  Worse, if tftpd
	 * break before doing the above "recvfrom", inetd would
	 * spawn endless instances, clogging the system.
	 */
	{
		int pid;
		int i, j;

		for (i = 1; i < 20; i++) {
		    pid = fork();
		    if (pid < 0) {
				sleep(i);
				/*
				 * flush out to most recently sent request.
				 *
				 * This may drop some request, but those
				 * will be resent by the clients when
				 * they timeout.  The positive effect of
				 * this flush is to (try to) prevent more
				 * than one tftpd being started up to service
				 * a single request from a single client.
				 */
				j = sizeof from;
				i = recvfrom(0, buf, segsize + 4, 0,
				    (struct sockaddr *)&from, &j);
				if (i > 0) {
					n = i;
					fromlen = j;
				}
		    } else {
				break;
		    }
		}
		if (pid < 0) {
			syslog(LOG_ERR, "fork: %m\n");
			exit(1);
		} else if (pid != 0) {
			exit(0);
		}
	}
	from.sin_family = AF_INET;
	alarm(0);
	close(0);
	close(1);
	peer = socket(AF_INET, SOCK_DGRAM, 0);
	if (peer < 0) {
		syslog(LOG_ERR, "socket: %m\n");
		exit(1);
	}
	if (bind(peer, (struct sockaddr *)&sockin, sizeof (sockin)) < 0) {
		syslog(LOG_ERR, "bind: %m\n");
		exit(1);
	}
	if (connect(peer, (struct sockaddr *)&from, sizeof(from)) < 0) {
		syslog(LOG_ERR, "connect: %m\n");
		exit(1);
	}
	tp = (struct tftphdr *)buf;
	tp->th_opcode = ntohs(tp->th_opcode);
	if (tp->th_opcode == RRQ || tp->th_opcode == WRQ)
		tftp(tp, n);
	exit(1);
}

int	validate_access();
int	sendfile(), recvfile();

struct formats {
	char	*f_mode;
	int	(*f_validate)();
	int	(*f_send)();
	int	(*f_recv)();
	int	f_convert;
} formats[] = {
	{ "netascii",	validate_access,	sendfile,	recvfile, 1 },
	{ "octet",	validate_access,	sendfile,	recvfile, 0 },
#ifdef notdef
	{ "mail",	validate_user,		sendmail,	recvmail, 1 },
#endif
	{ 0 }
};

int	set_blksize();
int	set_filesize();

struct options {
	char	*o_opt;
	int	(*o_fnc)();
} options[] = {
	{ "blksize",	set_blksize },
	{ "tsize",	set_filesize },
	{ NULL,		NULL }
};


/*
 * Set a non-standard block size (c.f. RFC1783)
 */
set_blksize(val, ret)
	char *val;
	char **ret;
{
	static char b_ret[5];
	int sz = atoi(val);

	if (sz < 8)
		return(0);
	else if (sz > PKTSIZE - 4)
		sz = PKTSIZE - 4;

	segsize = sz;
	sprintf(*ret = b_ret, "%d", sz);
	return(1);
}


/*
 * Return a file size (c.f. RFC1784)
 */
set_filesize(val, ret)
	char *val;
	char **ret;
{
	static char b_ret[10];
	off_t sz = atol(val);

	if (sz == 0)
		sz = filesize;
	sprintf(*ret = b_ret, "%lu", sz);
	return(1);
}


/*
 * Parse RFC1782 style options
 */
do_opt(opt, val, ap)
	char *opt;
	char *val;
	char **ap;
{
	struct options *po;
	char *ret;

	for (po = options; po->o_opt; po++)
		if (strcasecmp(po->o_opt, opt) == 0) {
			if (po->o_fnc(val, &ret)) {
				if (*ap + strlen(opt) + strlen(ret) + 2 >=
				    ackbuf + sizeof(ackbuf)) {
					nak(ENOSPACE);
					exit(1);
				}
				*ap = strrchr(strcpy(strrchr(strcpy(*ap, opt),
						'\000') + 1, ret), '\000') + 1;
			} else {
				nak(EOPTNEG);
				exit(1);
			}
			break;
		}
	return;
}


/*
 * Handle initial connection protocol.
 */
tftp(tp, size)
	struct tftphdr *tp;
	int size;
{
	register char *cp;
	int argn = 0, ecode;
	register struct formats *pf = NULL;
	char *filename, *mode;
	char *val, *opt;
	char *ap = ackbuf + 2;
	int  isopts;

	((struct tftphdr *)ackbuf)->th_opcode = ntohs(OACK);
	filename = cp = tp->th_stuff;
again:
	while (cp < buf + size) {
		if (*cp == '\0')
			break;
		cp++;
	}
	if (*cp != '\0') {
		nak(EBADOP);
		exit(1);
	}
	if (!argn++) {
		mode = ++cp;
		goto again;
	} else if (argn == 2) {
		for (cp = mode; *cp; cp++)
			if (isupper(*cp))
				*cp = tolower(*cp);
		for (pf = formats; pf->f_mode; pf++)
			if (strcmp(pf->f_mode, mode) == 0)
				break;
		if (pf->f_mode == 0) {