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NetBSD/libexec/tftpd/tftpd.c

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/* $NetBSD: tftpd.c,v 1.22 2001/01/09 23:29:22 lukem Exp $ */
/*
* Copyright (c) 1983, 1993
* The 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.
*/
#include <sys/cdefs.h>
#ifndef lint
__COPYRIGHT("@(#) Copyright (c) 1983, 1993\n\
The Regents of the University of California. All rights reserved.\n");
#if 0
static char sccsid[] = "@(#)tftpd.c 8.1 (Berkeley) 6/4/93";
#else
__RCSID("$NetBSD: tftpd.c,v 1.22 2001/01/09 23:29:22 lukem Exp $");
#endif
#endif /* not lint */
/*
* Trivial file transfer protocol server.
*
* This version includes many modifications by Jim Guyton
* <guyton@rand-unix>.
*/
#include <sys/param.h>
#include <sys/ioctl.h>
#include <sys/stat.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/tftp.h>
#include <arpa/inet.h>
#include <ctype.h>
#include <errno.h>
#include <fcntl.h>
#include <fcntl.h>
#include <grp.h>
#include <netdb.h>
#include <pwd.h>
#include <setjmp.h>
#include <signal.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <syslog.h>
#include <unistd.h>
#include "tftpsubs.h"
#define DEFAULTUSER "nobody"
#define TIMEOUT 5
extern char *__progname;
int peer;
int rexmtval = TIMEOUT;
int maxtimeout = 5*TIMEOUT;
#define PKTSIZE SEGSIZE+4
char buf[PKTSIZE];
char ackbuf[PKTSIZE];
struct sockaddr_storage from;
int fromlen;
/*
* Null-terminated directory prefix list for absolute pathname requests and
* search list for relative pathname requests.
*
* MAXDIRS should be at least as large as the number of arguments that
* inetd allows (currently 20).
*/
#define MAXDIRS 20
static struct dirlist {
char *name;
int len;
} dirs[MAXDIRS+1];
static int suppress_naks;
static int logging;
static int secure;
static char *securedir;
struct formats;
static const char *errtomsg(int);
static void nak(int);
static void tftp(struct tftphdr *, int);
static void usage(void);
static char *verifyhost(struct sockaddr *);
void justquit(int);
int main(int, char **);
void recvfile(struct formats *);
void sendfile(struct formats *);
void timer(int);
int validate_access(char **, int);
struct formats {
const char *f_mode;
int (*f_validate)(char **, int);
void (*f_send)(struct formats *);
void (*f_recv)(struct formats *);
int f_convert;
} formats[] = {
{ "netascii", validate_access, sendfile, recvfile, 1 },
{ "octet", validate_access, sendfile, recvfile, 0 },
{ 0 }
};
static void
usage(void)
{
syslog(LOG_ERR,
"Usage: %s [-ln] [-u user] [-g group] [-s directory] [directory ...]",
__progname);
exit(1);
}
int
main(int argc, char *argv[])
{
struct sockaddr_storage me;
struct passwd *pwent;
struct group *grent;
struct tftphdr *tp;
char *tgtuser, *tgtgroup, *ep;
int n, ch, on, fd;
int len;
uid_t curuid, tgtuid;
gid_t curgid, tgtgid;
long nid;
n = 0;
fd = 0;
openlog("tftpd", LOG_PID | LOG_NDELAY, LOG_DAEMON);
tgtuser = DEFAULTUSER;
tgtgroup = NULL;
curuid = getuid();
curgid = getgid();
while ((ch = getopt(argc, argv, "g:lns:u:")) != -1)
switch (ch) {
case 'g':
tgtgroup = optarg;
break;
case 'l':
logging = 1;
break;
case 'n':
suppress_naks = 1;
break;
case 's':
secure = 1;
securedir = optarg;
break;
case 'u':
tgtuser = optarg;
break;
default:
usage();
break;
}
if (optind < argc) {
struct dirlist *dirp;
/* Get list of directory prefixes. Skip relative pathnames. */
for (dirp = dirs; optind < argc && dirp < &dirs[MAXDIRS];
optind++) {
if (argv[optind][0] == '/') {
dirp->name = argv[optind];
dirp->len = strlen(dirp->name);
dirp++;
}
}
}
if (*tgtuser == '\0' || (tgtgroup != NULL && *tgtgroup == '\0'))
usage();
nid = (strtol(tgtuser, &ep, 10));
if (*ep == '\0') {
if (nid > UID_MAX) {
syslog(LOG_ERR, "uid %ld is too large", nid);
exit(1);
}
pwent = getpwuid((uid_t)nid);
} else
pwent = getpwnam(tgtuser);
if (pwent == NULL) {
syslog(LOG_ERR, "unknown user `%s'", tgtuser);
exit(1);
}
tgtuid = pwent->pw_uid;
tgtgid = pwent->pw_gid;
if (tgtgroup != NULL) {
nid = (strtol(tgtgroup, &ep, 10));
if (*ep == '\0') {
if (nid > GID_MAX) {
syslog(LOG_ERR, "gid %ld is too large", nid);
exit(1);
}
grent = getgrgid((gid_t)nid);
} else
grent = getgrnam(tgtgroup);
if (grent != NULL)
tgtgid = grent->gr_gid;
else {
syslog(LOG_ERR, "unknown group `%s'", tgtgroup);
exit(1);
}
}
if (secure) {
if (chdir(securedir) < 0) {
syslog(LOG_ERR, "chdir %s: %m", securedir);
exit(1);
}
if (chroot(".")) {
syslog(LOG_ERR, "chroot: %m");
exit(1);
}
}
if (logging)
syslog(LOG_DEBUG, "running as user `%s' (%d), group `%s' (%d)",
tgtuser, tgtuid, tgtgroup ? tgtgroup : "(unspecified)",
tgtgid);
if (curgid != tgtgid) {
if (setgid(tgtgid)) {
syslog(LOG_ERR, "setgid to %d: %m", (int)tgtgid);
exit(1);
}
if (setgroups(0, NULL)) {
syslog(LOG_ERR, "setgroups: %m");
exit(1);
}
}
if (curuid != tgtuid) {
if (setuid(tgtuid)) {
syslog(LOG_ERR, "setuid to %d: %m", (int)tgtuid);
exit(1);
}
}
on = 1;
if (ioctl(fd, FIONBIO, &on) < 0) {
syslog(LOG_ERR, "ioctl(FIONBIO): %m");
exit(1);
}
fromlen = sizeof (from);
n = recvfrom(fd, buf, sizeof (buf), 0,
(struct sockaddr *)&from, &fromlen);
if (n < 0) {
syslog(LOG_ERR, "recvfrom: %m");
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(fd, 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");
exit(1);
} else if (pid != 0) {
exit(0);
}
}
/*
* remember what address this was sent to, so we can respond on the
* same interface
*/
len = sizeof(me);
if (getsockname(fd, (struct sockaddr *)&me, &len) == 0) {
switch (me.ss_family) {
case AF_INET:
((struct sockaddr_in *)&me)->sin_port = 0;
break;
case AF_INET6:
((struct sockaddr_in6 *)&me)->sin6_port = 0;
break;
default:
/* unsupported */
break;
}
} else {
memset(&me, 0, sizeof(me));
me.ss_family = from.ss_family;
me.ss_len = from.ss_len;
}
alarm(0);
close(fd);
close(1);
peer = socket(from.ss_family, SOCK_DGRAM, 0);
if (peer < 0) {
syslog(LOG_ERR, "socket: %m");
exit(1);
}
if (bind(peer, (struct sockaddr *)&me, me.ss_len) < 0) {
syslog(LOG_ERR, "bind: %m");
exit(1);
}
if (connect(peer, (struct sockaddr *)&from, from.ss_len) < 0) {
syslog(LOG_ERR, "connect: %m");
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);
}
/*
* Handle initial connection protocol.
*/
static void
tftp(struct tftphdr *tp, int size)
{
struct formats *pf;
char *cp;
char *filename, *mode;
int first, ecode;
first = 1;
mode = NULL;
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 (logging) {
syslog(LOG_INFO, "%s: %s request for %s: %s",
verifyhost((struct sockaddr *)&from),
tp->th_opcode == WRQ ? "write" : "read",
filename, errtomsg(ecode));
}
if (ecode) {
/*
* Avoid storms of naks to a RRQ broadcast for a relative
* bootfile pathname from a diskless Sun.
*/
if (suppress_naks && *filename != '/' && ecode == ENOTFOUND)
exit(0);
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.
*/
int
validate_access(char **filep, int mode)
{
struct stat stbuf;
struct dirlist *dirp;
static char pathname[MAXPATHLEN];
char *filename;
int fd;
filename = *filep;
/*
* Prevent tricksters from getting around the directory restrictions
*/
if (strstr(filename, "/../"))
return (EACCESS);
if (*filename == '/') {
/*
* Allow the request if it's in one of the approved locations.
* Special case: check the null prefix ("/") by looking
* for length = 1 and relying on the arg. processing that
* it's a /.
*/
for (dirp = dirs; dirp->name != NULL; dirp++) {
if (dirp->len == 1 ||
(!strncmp(filename, dirp->name, dirp->len) &&
filename[dirp->len] == '/'))
break;
}
/* If directory list is empty, allow access to any file */
if (dirp->name == NULL && dirp != dirs)
return (EACCESS);
if (stat(filename, &stbuf) < 0)
return (errno == ENOENT ? ENOTFOUND : EACCESS);
if (!S_ISREG(stbuf.st_mode))
return (ENOTFOUND);
if (mode == RRQ) {
if ((stbuf.st_mode & S_IROTH) == 0)
return (EACCESS);
} else {
if ((stbuf.st_mode & S_IWOTH) == 0)
return (EACCESS);
}
} else {
/*
* Relative file name: search the approved locations for it.
*/
if (!strncmp(filename, "../", 3))
return (EACCESS);
/*
* Find the first file that exists in any of the directories,
* check access on it.
*/
if (dirs[0].name != NULL) {
for (dirp = dirs; dirp->name != NULL; dirp++) {
snprintf(pathname, sizeof pathname, "%s/%s",
dirp->name, filename);
if (stat(pathname, &stbuf) == 0 &&
(stbuf.st_mode & S_IFMT) == S_IFREG) {
break;
}
}
if (dirp->name == NULL)
return (ENOTFOUND);
if (mode == RRQ && !(stbuf.st_mode & S_IROTH))
return (EACCESS);
if (mode == WRQ && !(stbuf.st_mode & S_IWOTH))
return (EACCESS);
*filep = filename = pathname;
} else {
/*
* If there's no directory list, take our cue from the
* absolute file request check above (*filename == '/'),
* and allow access to anything.
*/
if (stat(filename, &stbuf) < 0)
return (errno == ENOENT ? ENOTFOUND : EACCESS);
if (!S_ISREG(stbuf.st_mode))
return (ENOTFOUND);
if (mode == RRQ) {
if ((stbuf.st_mode & S_IROTH) == 0)
return (EACCESS);
} else {
if ((stbuf.st_mode & S_IWOTH) == 0)
return (EACCESS);
}
*filep = filename;
}
}
fd = open(filename, mode == RRQ ? O_RDONLY : O_WRONLY | O_TRUNC);
if (fd < 0)
return (errno + 100);
file = fdopen(fd, (mode == RRQ)? "r":"w");
if (file == NULL) {
close(fd);
return (errno + 100);
}
return (0);
}
int timeout;
jmp_buf timeoutbuf;
void
timer(int dummy)
{
timeout += rexmtval;
if (timeout >= maxtimeout)
exit(1);
longjmp(timeoutbuf, 1);
}
/*
* Send the requested file.
*/
void
sendfile(struct formats *pf)
{
volatile unsigned int block;
struct tftphdr *dp;
struct tftphdr *ap; /* ack packet */
int size, n;
signal(SIGALRM, timer);
dp = r_init();
ap = (struct tftphdr *)ackbuf;
block = 1;
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");
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");
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(int dummy)
{
exit(0);
}
/*
* Receive a file.
*/
void
recvfile(struct formats *pf)
{
volatile unsigned int block;
struct tftphdr *dp;
struct tftphdr *ap; /* ack buffer */
int n, size;
signal(SIGALRM, timer);
dp = w_init();
ap = (struct tftphdr *)ackbuf;
block = 0;
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");
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");
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;
}
const struct errmsg {
int e_code;
const 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 }
};
static const char *
errtomsg(int error)
{
static char ebuf[20];
const struct errmsg *pe;
if (error == 0)
return ("success");
for (pe = errmsgs; pe->e_code >= 0; pe++)
if (pe->e_code == error)
return (pe->e_msg);
snprintf(ebuf, sizeof(ebuf), "error %d", error);
return (ebuf);
}
/*
* Send a nak packet (error message).
* Error code passed in is one of the
* standard TFTP codes, or a UNIX errno
* offset by 100.
*/
static void
nak(int error)
{
const struct errmsg *pe;
struct tftphdr *tp;
int length;
size_t msglen;
tp = (struct tftphdr *)buf;
tp->th_opcode = htons((u_short)ERROR);
msglen = sizeof(buf) - (&tp->th_msg[0] - buf);
for (pe = errmsgs; pe->e_code >= 0; pe++)
if (pe->e_code == error)
break;
if (pe->e_code < 0) {
tp->th_code = EUNDEF; /* set 'undef' errorcode */
strlcpy(tp->th_msg, strerror(error - 100), msglen);
} else {
tp->th_code = htons((u_short)error);
strlcpy(tp->th_msg, pe->e_msg, msglen);
}
length = strlen(tp->th_msg);
msglen = &tp->th_msg[length + 1] - buf;
if (send(peer, buf, msglen, 0) != msglen)
syslog(LOG_ERR, "nak: %m");
}
static char *
verifyhost(struct sockaddr *fromp)
{
static char hbuf[MAXHOSTNAMELEN];
if (getnameinfo(fromp, fromp->sa_len, hbuf, sizeof(hbuf), NULL, 0, 0))
strlcpy(hbuf, "?", sizeof(hbuf));
return (hbuf);
}
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