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NetBSD/libexec/tftpd/tftpd.c

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/*
* 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>
*/
#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
extern int errno;
struct sockaddr_in s_in = { AF_INET };
int peer;
int rexmtval = TIMEOUT;
int maxtimeout = 5*TIMEOUT;
#define PKTSIZE SEGSIZE+4
char buf[PKTSIZE];
char ackbuf[PKTSIZE];
struct sockaddr_in from;
int fromlen;
#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, sizeof (buf), 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, sizeof (buf), 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 *)&s_in, sizeof (s_in)) < 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 }
};
/*
* Handle initial connection protocol.
*/
tftp(tp, size)
struct tftphdr *tp;
int size;
{
register char *cp;
int first = 1, ecode;
register struct formats *pf;
char *filename, *mode;
filename = cp = tp->th_stuff;
again:
while (cp < buf + size) {
if (*cp == '\0')
break;
cp++;
}
if (*cp != '\0') {
nak(EBADOP);
exit(1);
}
if (first) {
mode = ++cp;
first = 0;
goto again;
}
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) {
nak(EBADOP);
exit(1);
}
ecode = (*pf->f_validate)(filename, tp->th_opcode);
if (ecode) {
nak(ecode);
exit(1);
}
if (tp->th_opcode == WRQ)
(*pf->f_recv)(pf);
else
(*pf->f_send)(pf);
exit(0);
}
FILE *file;
/*
* Validate file access. Since we
* have no uid or gid, for now require
* file to exist and be publicly
* readable/writable.
* If we were invoked with arguments
* from inetd then the file must also be
* in one of the given directory prefixes.
* Note also, full path name must be
* given as we have no login directory.
*/
validate_access(filename, mode)
char *filename;
int mode;
{
struct stat stbuf;
int fd;
char *cp, **dirp;
if (*filename != '/')
return (EACCESS);
/*
* prevent tricksters from getting around the directory restrictions
*/
for (cp = filename + 1; *cp; cp++)
if(*cp == '.' && strncmp(cp-1, "/../", 4) == 0)
return(EACCESS);
for (dirp = dirs; *dirp; dirp++)
if (strncmp(filename, *dirp, strlen(*dirp)) == 0)
break;
if (*dirp==0 && dirp!=dirs)
return (EACCESS);
if (stat(filename, &stbuf) < 0)
return (errno == ENOENT ? ENOTFOUND : EACCESS);
if (mode == RRQ) {
if ((stbuf.st_mode&(S_IREAD >> 6)) == 0)
return (EACCESS);
} else {
if ((stbuf.st_mode&(S_IWRITE >> 6)) == 0)
return (EACCESS);
}
fd = open(filename, mode == RRQ ? 0 : 1);
if (fd < 0)
return (errno + 100);
file = fdopen(fd, (mode == RRQ)? "r":"w");
if (file == NULL) {
return errno+100;
}
return (0);
}
int timeout;
jmp_buf timeoutbuf;
void
timer()
{
timeout += rexmtval;
if (timeout >= maxtimeout)
exit(1);
longjmp(timeoutbuf, 1);
}
/*
* Send the requested file.
*/
sendfile(pf)
struct formats *pf;
{
struct tftphdr *dp, *r_init();
register struct tftphdr *ap; /* ack packet */
register int block = 1, size, n;
signal(SIGALRM, timer);
dp = r_init();
ap = (struct tftphdr *)ackbuf;
do {
size = readit(file, &dp, pf->f_convert);
if (size < 0) {
nak(errno + 100);
goto abort;
}
dp->th_opcode = htons((u_short)DATA);
dp->th_block = htons((u_short)block);
timeout = 0;
(void) setjmp(timeoutbuf);
send_data:
if (send(peer, dp, size + 4, 0) != size + 4) {
syslog(LOG_ERR, "tftpd: write: %m\n");
goto abort;
}
read_ahead(file, pf->f_convert);
for ( ; ; ) {
alarm(rexmtval); /* read the ack */
n = recv(peer, ackbuf, sizeof (ackbuf), 0);
alarm(0);
if (n < 0) {
syslog(LOG_ERR, "tftpd: read: %m\n");
goto abort;
}
ap->th_opcode = ntohs((u_short)ap->th_opcode);
ap->th_block = ntohs((u_short)ap->th_block);
if (ap->th_opcode == ERROR)
goto abort;
if (ap->th_opcode == ACK) {
if (ap->th_block == block) {
break;
}
/* Re-synchronize with the other side */
(void) synchnet(peer);
if (ap->th_block == (block -1)) {
goto send_data;
}
}
}
block++;
} while (size == SEGSIZE);
abort:
(void) fclose(file);
}
void
justquit()
{
exit(0);
}
/*
* Receive a file.
*/
recvfile(pf)
struct formats *pf;
{
struct tftphdr *dp, *w_init();
register struct tftphdr *ap; /* ack buffer */
register int block = 0, n, size;
signal(SIGALRM, timer);
dp = w_init();
ap = (struct tftphdr *)ackbuf;
do {
timeout = 0;
ap->th_opcode = htons((u_short)ACK);
ap->th_block = htons((u_short)block);
block++;
(void) setjmp(timeoutbuf);
send_ack:
if (send(peer, ackbuf, 4, 0) != 4) {
syslog(LOG_ERR, "tftpd: write: %m\n");
goto abort;
}
write_behind(file, pf->f_convert);
for ( ; ; ) {
alarm(rexmtval);
n = recv(peer, dp, PKTSIZE, 0);
alarm(0);
if (n < 0) { /* really? */
syslog(LOG_ERR, "tftpd: read: %m\n");
goto abort;
}
dp->th_opcode = ntohs((u_short)dp->th_opcode);
dp->th_block = ntohs((u_short)dp->th_block);
if (dp->th_opcode == ERROR)
goto abort;
if (dp->th_opcode == DATA) {
if (dp->th_block == block) {
break; /* normal */
}
/* Re-synchronize with the other side */
(void) synchnet(peer);
if (dp->th_block == (block-1))
goto send_ack; /* rexmit */
}
}
/* size = write(file, dp->th_data, n - 4); */
size = writeit(file, &dp, n - 4, pf->f_convert);
if (size != (n-4)) { /* ahem */
if (size < 0) nak(errno + 100);
else nak(ENOSPACE);
goto abort;
}
} while (size == SEGSIZE);
write_behind(file, pf->f_convert);
(void) fclose(file); /* close data file */
ap->th_opcode = htons((u_short)ACK); /* send the "final" ack */
ap->th_block = htons((u_short)(block));
(void) send(peer, ackbuf, 4, 0);
signal(SIGALRM, justquit); /* just quit on timeout */
alarm(rexmtval);
n = recv(peer, buf, sizeof (buf), 0); /* normally times out and quits */
alarm(0);
if (n >= 4 && /* if read some data */
dp->th_opcode == DATA && /* and got a data block */
block == dp->th_block) { /* then my last ack was lost */
(void) send(peer, ackbuf, 4, 0); /* resend final ack */
}
abort:
return;
}
struct errmsg {
int e_code;
char *e_msg;
} errmsgs[] = {
{ EUNDEF, "Undefined error code" },
{ ENOTFOUND, "File not found" },
{ EACCESS, "Access violation" },
{ ENOSPACE, "Disk full or allocation exceeded" },
{ EBADOP, "Illegal TFTP operation" },
{ EBADID, "Unknown transfer ID" },
{ EEXISTS, "File already exists" },
{ ENOUSER, "No such user" },
{ -1, 0 }
};
/*
* Send a nak packet (error message).
* Error code passed in is one of the
* standard TFTP codes, or a UNIX errno
* offset by 100.
*/
nak(error)
int error;
{
register struct tftphdr *tp;
int length;
register struct errmsg *pe;
tp = (struct tftphdr *)buf;
tp->th_opcode = htons((u_short)ERROR);
tp->th_code = htons((u_short)error);
for (pe = errmsgs; pe->e_code >= 0; pe++)
if (pe->e_code == error)
break;
if (pe->e_code < 0) {
pe->e_msg = strerror(error - 100);
tp->th_code = EUNDEF; /* set 'undef' errorcode */
}
strcpy(tp->th_msg, pe->e_msg);
length = strlen(pe->e_msg);
tp->th_msg[length] = '\0';
length += 5;
if (send(peer, buf, length, 0) != length)
syslog(LOG_ERR, "nak: %m\n");
}
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