freebsd-skq/libexec/tftpd/tftpd.c
eadler a603c87b02 Check the return error of set[e][ug]id. While this can never fail in the
current version of FreeBSD, this isn't guarenteed by the API.
Custom security modules, or future implementations of the setuid and
setgid may fail.

Submitted by:	Erik Cederstrand
Approved by:	cperciva
MFC after:	3 days
2012-10-22 03:07:05 +00:00

841 lines
20 KiB
C

/*
* 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.
*/
#ifndef lint
static const char copyright[] =
"@(#) Copyright (c) 1983, 1993\n\
The Regents of the University of California. All rights reserved.\n";
#endif /* not lint */
#ifndef lint
#if 0
static char sccsid[] = "@(#)tftpd.c 8.1 (Berkeley) 6/4/93";
#endif
#endif /* not lint */
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
/*
* 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 <ctype.h>
#include <errno.h>
#include <fcntl.h>
#include <netdb.h>
#include <pwd.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <syslog.h>
#include <tcpd.h>
#include <unistd.h>
#include "tftp-file.h"
#include "tftp-io.h"
#include "tftp-utils.h"
#include "tftp-transfer.h"
#include "tftp-options.h"
static void tftp_wrq(int peer, char *, ssize_t);
static void tftp_rrq(int peer, char *, ssize_t);
/*
* 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 {
const char *name;
int len;
} dirs[MAXDIRS+1];
static int suppress_naks;
static int logging;
static int ipchroot;
static int create_new = 0;
static const char *newfile_format = "%Y%m%d";
static int increase_name = 0;
static mode_t mask = S_IWGRP | S_IWOTH;
struct formats;
static void tftp_recvfile(int peer, const char *mode);
static void tftp_xmitfile(int peer, const char *mode);
static int validate_access(int peer, char **, int);
static char peername[NI_MAXHOST];
static FILE *file;
static struct formats {
const char *f_mode;
int f_convert;
} formats[] = {
{ "netascii", 1 },
{ "octet", 0 },
{ NULL, 0 }
};
int
main(int argc, char *argv[])
{
struct tftphdr *tp;
int peer;
socklen_t peerlen, len;
ssize_t n;
int ch;
char *chroot_dir = NULL;
struct passwd *nobody;
const char *chuser = "nobody";
char recvbuffer[MAXPKTSIZE];
int allow_ro = 1, allow_wo = 1;
tzset(); /* syslog in localtime */
acting_as_client = 0;
tftp_openlog("tftpd", LOG_PID | LOG_NDELAY, LOG_FTP);
while ((ch = getopt(argc, argv, "cCd:F:lnoOp:s:u:U:wW")) != -1) {
switch (ch) {
case 'c':
ipchroot = 1;
break;
case 'C':
ipchroot = 2;
break;
case 'd':
if (atoi(optarg) != 0)
debug += atoi(optarg);
else
debug |= debug_finds(optarg);
break;
case 'F':
newfile_format = optarg;
break;
case 'l':
logging = 1;
break;
case 'n':
suppress_naks = 1;
break;
case 'o':
options_rfc_enabled = 0;
break;
case 'O':
options_extra_enabled = 0;
break;
case 'p':
packetdroppercentage = atoi(optarg);
tftp_log(LOG_INFO,
"Randomly dropping %d out of 100 packets",
packetdroppercentage);
break;
case 's':
chroot_dir = optarg;
break;
case 'u':
chuser = optarg;
break;
case 'U':
mask = strtol(optarg, NULL, 0);
break;
case 'w':
create_new = 1;
break;
case 'W':
create_new = 1;
increase_name = 1;
break;
default:
tftp_log(LOG_WARNING,
"ignoring unknown option -%c", ch);
}
}
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++;
}
}
}
else if (chroot_dir) {
dirs->name = "/";
dirs->len = 1;
}
if (ipchroot > 0 && chroot_dir == NULL) {
tftp_log(LOG_ERR, "-c requires -s");
exit(1);
}
umask(mask);
{
int on = 1;
if (ioctl(0, FIONBIO, &on) < 0) {
tftp_log(LOG_ERR, "ioctl(FIONBIO): %s", strerror(errno));
exit(1);
}
}
/* Find out who we are talking to and what we are going to do */
peerlen = sizeof(peer_sock);
n = recvfrom(0, recvbuffer, MAXPKTSIZE, 0,
(struct sockaddr *)&peer_sock, &peerlen);
if (n < 0) {
tftp_log(LOG_ERR, "recvfrom: %s", strerror(errno));
exit(1);
}
getnameinfo((struct sockaddr *)&peer_sock, peer_sock.ss_len,
peername, sizeof(peername), NULL, 0, NI_NUMERICHOST);
/*
* 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 i, pid;
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.
*/
peerlen = sizeof peer_sock;
i = recvfrom(0, recvbuffer, MAXPKTSIZE, 0,
(struct sockaddr *)&peer_sock, &peerlen);
if (i > 0) {
n = i;
}
} else {
break;
}
}
if (pid < 0) {
tftp_log(LOG_ERR, "fork: %s", strerror(errno));
exit(1);
} else if (pid != 0) {
exit(0);
}
}
/*
* See if the client is allowed to talk to me.
* (This needs to be done before the chroot())
*/
{
struct request_info req;
request_init(&req, RQ_CLIENT_ADDR, peername, 0);
request_set(&req, RQ_DAEMON, "tftpd", 0);
if (hosts_access(&req) == 0) {
if (debug&DEBUG_ACCESS)
tftp_log(LOG_WARNING,
"Access denied by 'tftpd' entry "
"in /etc/hosts.allow");
/*
* Full access might be disabled, but maybe the
* client is allowed to do read-only access.
*/
request_set(&req, RQ_DAEMON, "tftpd-ro", 0);
allow_ro = hosts_access(&req);
request_set(&req, RQ_DAEMON, "tftpd-wo", 0);
allow_wo = hosts_access(&req);
if (allow_ro == 0 && allow_wo == 0) {
tftp_log(LOG_WARNING,
"Unauthorized access from %s", peername);
exit(1);
}
if (debug&DEBUG_ACCESS) {
if (allow_ro)
tftp_log(LOG_WARNING,
"But allowed readonly access "
"via 'tftpd-ro' entry");
if (allow_wo)
tftp_log(LOG_WARNING,
"But allowed writeonly access "
"via 'tftpd-wo' entry");
}
} else
if (debug&DEBUG_ACCESS)
tftp_log(LOG_WARNING,
"Full access allowed"
"in /etc/hosts.allow");
}
/*
* Since we exit here, we should do that only after the above
* recvfrom to keep inetd from constantly forking should there
* be a problem. See the above comment about system clogging.
*/
if (chroot_dir) {
if (ipchroot > 0) {
char *tempchroot;
struct stat sb;
int statret;
struct sockaddr_storage ss;
char hbuf[NI_MAXHOST];
statret = -1;
memcpy(&ss, &peer_sock, peer_sock.ss_len);
unmappedaddr((struct sockaddr_in6 *)&ss);
getnameinfo((struct sockaddr *)&ss, ss.ss_len,
hbuf, sizeof(hbuf), NULL, 0,
NI_NUMERICHOST);
asprintf(&tempchroot, "%s/%s", chroot_dir, hbuf);
if (ipchroot == 2)
statret = stat(tempchroot, &sb);
if (ipchroot == 1 ||
(statret == 0 && (sb.st_mode & S_IFDIR)))
chroot_dir = tempchroot;
}
/* Must get this before chroot because /etc might go away */
if ((nobody = getpwnam(chuser)) == NULL) {
tftp_log(LOG_ERR, "%s: no such user", chuser);
exit(1);
}
if (chroot(chroot_dir)) {
tftp_log(LOG_ERR, "chroot: %s: %s",
chroot_dir, strerror(errno));
exit(1);
}
chdir("/");
setgroups(1, &nobody->pw_gid);
if (setuid(nobody->pw_uid) != 0) {
tftp_log(LOG_ERR, "setuid failed");
exit(1);
}
}
len = sizeof(me_sock);
if (getsockname(0, (struct sockaddr *)&me_sock, &len) == 0) {
switch (me_sock.ss_family) {
case AF_INET:
((struct sockaddr_in *)&me_sock)->sin_port = 0;
break;
case AF_INET6:
((struct sockaddr_in6 *)&me_sock)->sin6_port = 0;
break;
default:
/* unsupported */
break;
}
} else {
memset(&me_sock, 0, sizeof(me_sock));
me_sock.ss_family = peer_sock.ss_family;
me_sock.ss_len = peer_sock.ss_len;
}
close(0);
close(1);
peer = socket(peer_sock.ss_family, SOCK_DGRAM, 0);
if (peer < 0) {
tftp_log(LOG_ERR, "socket: %s", strerror(errno));
exit(1);
}
if (bind(peer, (struct sockaddr *)&me_sock, me_sock.ss_len) < 0) {
tftp_log(LOG_ERR, "bind: %s", strerror(errno));
exit(1);
}
tp = (struct tftphdr *)recvbuffer;
tp->th_opcode = ntohs(tp->th_opcode);
if (tp->th_opcode == RRQ) {
if (allow_ro)
tftp_rrq(peer, tp->th_stuff, n - 1);
else {
tftp_log(LOG_WARNING,
"%s read access denied", peername);
exit(1);
}
}
if (tp->th_opcode == WRQ) {
if (allow_wo)
tftp_wrq(peer, tp->th_stuff, n - 1);
else {
tftp_log(LOG_WARNING,
"%s write access denied", peername);
exit(1);
}
}
exit(1);
}
static void
reduce_path(char *fn)
{
char *slash, *ptr;
/* Reduce all "/+./" to "/" (just in case we've got "/./../" later */
while ((slash = strstr(fn, "/./")) != NULL) {
for (ptr = slash; ptr > fn && ptr[-1] == '/'; ptr--)
;
slash += 2;
while (*slash)
*++ptr = *++slash;
}
/* Now reduce all "/something/+../" to "/" */
while ((slash = strstr(fn, "/../")) != NULL) {
if (slash == fn)
break;
for (ptr = slash; ptr > fn && ptr[-1] == '/'; ptr--)
;
for (ptr--; ptr >= fn; ptr--)
if (*ptr == '/')
break;
if (ptr < fn)
break;
slash += 3;
while (*slash)
*++ptr = *++slash;
}
}
static char *
parse_header(int peer, char *recvbuffer, ssize_t size,
char **filename, char **mode)
{
char *cp;
int i;
struct formats *pf;
*mode = NULL;
cp = recvbuffer;
i = get_field(peer, recvbuffer, size);
if (i >= PATH_MAX) {
tftp_log(LOG_ERR, "Bad option - filename too long");
send_error(peer, EBADOP);
exit(1);
}
*filename = recvbuffer;
tftp_log(LOG_INFO, "Filename: '%s'", *filename);
cp += i;
i = get_field(peer, cp, size);
*mode = cp;
cp += i;
/* Find the file transfer mode */
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 == NULL) {
tftp_log(LOG_ERR,
"Bad option - Unknown transfer mode (%s)", *mode);
send_error(peer, EBADOP);
exit(1);
}
tftp_log(LOG_INFO, "Mode: '%s'", *mode);
return (cp + 1);
}
/*
* WRQ - receive a file from the client
*/
void
tftp_wrq(int peer, char *recvbuffer, ssize_t size)
{
char *cp;
int has_options = 0, ecode;
char *filename, *mode;
char fnbuf[PATH_MAX];
cp = parse_header(peer, recvbuffer, size, &filename, &mode);
size -= (cp - recvbuffer) + 1;
strcpy(fnbuf, filename);
reduce_path(fnbuf);
filename = fnbuf;
if (size > 0) {
if (options_rfc_enabled)
has_options = !parse_options(peer, cp, size);
else
tftp_log(LOG_INFO, "Options found but not enabled");
}
ecode = validate_access(peer, &filename, WRQ);
if (ecode == 0) {
if (has_options)
send_oack(peer);
else
send_ack(peer, 0);
}
if (logging) {
tftp_log(LOG_INFO, "%s: write request for %s: %s", peername,
filename, errtomsg(ecode));
}
tftp_recvfile(peer, mode);
exit(0);
}
/*
* RRQ - send a file to the client
*/
void
tftp_rrq(int peer, char *recvbuffer, ssize_t size)
{
char *cp;
int has_options = 0, ecode;
char *filename, *mode;
char fnbuf[PATH_MAX];
cp = parse_header(peer, recvbuffer, size, &filename, &mode);
size -= (cp - recvbuffer) + 1;
strcpy(fnbuf, filename);
reduce_path(fnbuf);
filename = fnbuf;
if (size > 0) {
if (options_rfc_enabled)
has_options = !parse_options(peer, cp, size);
else
tftp_log(LOG_INFO, "Options found but not enabled");
}
ecode = validate_access(peer, &filename, RRQ);
if (ecode == 0) {
if (has_options) {
int n;
char lrecvbuffer[MAXPKTSIZE];
struct tftphdr *rp = (struct tftphdr *)lrecvbuffer;
send_oack(peer);
n = receive_packet(peer, lrecvbuffer, MAXPKTSIZE,
NULL, timeoutpacket);
if (n < 0) {
if (debug&DEBUG_SIMPLE)
tftp_log(LOG_DEBUG, "Aborting: %s",
rp_strerror(n));
return;
}
if (rp->th_opcode != ACK) {
if (debug&DEBUG_SIMPLE)
tftp_log(LOG_DEBUG,
"Expected ACK, got %s on OACK",
packettype(rp->th_opcode));
return;
}
}
}
if (logging)
tftp_log(LOG_INFO, "%s: read request for %s: %s", peername,
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);
send_error(peer, ecode);
exit(1);
}
tftp_xmitfile(peer, mode);
}
/*
* Find the next value for YYYYMMDD.nn when the file to be written should
* be unique. Due to the limitations of nn, we will fail if nn reaches 100.
* Besides, that is four updates per hour on a file, which is kind of
* execessive anyway.
*/
static int
find_next_name(char *filename, int *fd)
{
int i;
time_t tval;
size_t len;
struct tm lt;
char yyyymmdd[MAXPATHLEN];
char newname[MAXPATHLEN];
/* Create the YYYYMMDD part of the filename */
time(&tval);
lt = *localtime(&tval);
len = strftime(yyyymmdd, sizeof(yyyymmdd), newfile_format, &lt);
if (len == 0) {
syslog(LOG_WARNING,
"Filename suffix too long (%d characters maximum)",
MAXPATHLEN);
return (EACCESS);
}
/* Make sure the new filename is not too long */
if (strlen(filename) > MAXPATHLEN - len - 5) {
syslog(LOG_WARNING,
"Filename too long (%zd characters, %zd maximum)",
strlen(filename), MAXPATHLEN - len - 5);
return (EACCESS);
}
/* Find the first file which doesn't exist */
for (i = 0; i < 100; i++) {
sprintf(newname, "%s.%s.%02d", filename, yyyymmdd, i);
*fd = open(newname,
O_WRONLY | O_CREAT | O_EXCL,
S_IRUSR | S_IWUSR | S_IRGRP |
S_IWGRP | S_IROTH | S_IWOTH);
if (*fd > 0)
return 0;
}
return (EEXIST);
}
/*
* 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.
*/
int
validate_access(int peer, char **filep, int mode)
{
struct stat stbuf;
int fd;
int error;
struct dirlist *dirp;
static char pathname[MAXPATHLEN];
char *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 ((stbuf.st_mode & S_IFMT) != S_IFREG)
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 {
int err;
/*
* Relative file name: search the approved locations for it.
* Don't allow write requests that avoid directory
* restrictions.
*/
if (!strncmp(filename, "../", 3))
return (EACCESS);
/*
* If the file exists in one of the directories and isn't
* readable, continue looking. However, change the error code
* to give an indication that the file exists.
*/
err = ENOTFOUND;
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) {
if ((stbuf.st_mode & S_IROTH) != 0) {
break;
}
err = EACCESS;
}
}
if (dirp->name != NULL)
*filep = filename = pathname;
else if (mode == RRQ)
return (err);
}
/*
* This option is handled here because it (might) require(s) the
* size of the file.
*/
option_tsize(peer, NULL, mode, &stbuf);
if (mode == RRQ)
fd = open(filename, O_RDONLY);
else {
if (create_new) {
if (increase_name) {
error = find_next_name(filename, &fd);
if (error > 0)
return (error + 100);
} else
fd = open(filename,
O_WRONLY | O_TRUNC | O_CREAT,
S_IRUSR | S_IWUSR | S_IRGRP |
S_IWGRP | S_IROTH | S_IWOTH );
} else
fd = open(filename, 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);
}
static void
tftp_xmitfile(int peer, const char *mode)
{
uint16_t block;
time_t now;
struct tftp_stats ts;
now = time(NULL);
if (debug&DEBUG_SIMPLE)
tftp_log(LOG_DEBUG, "Transmitting file");
read_init(0, file, mode);
block = 1;
tftp_send(peer, &block, &ts);
read_close();
if (debug&DEBUG_SIMPLE)
tftp_log(LOG_INFO, "Sent %d bytes in %d seconds",
ts.amount, time(NULL) - now);
}
static void
tftp_recvfile(int peer, const char *mode)
{
uint16_t block;
struct timeval now1, now2;
struct tftp_stats ts;
gettimeofday(&now1, NULL);
if (debug&DEBUG_SIMPLE)
tftp_log(LOG_DEBUG, "Receiving file");
write_init(0, file, mode);
block = 0;
tftp_receive(peer, &block, &ts, NULL, 0);
write_close();
gettimeofday(&now2, NULL);
if (debug&DEBUG_SIMPLE) {
double f;
if (now1.tv_usec > now2.tv_usec) {
now2.tv_usec += 1000000;
now2.tv_sec--;
}
f = now2.tv_sec - now1.tv_sec +
(now2.tv_usec - now1.tv_usec) / 100000.0;
tftp_log(LOG_INFO,
"Download of %d bytes in %d blocks completed after %0.1f seconds\n",
ts.amount, block, f);
}
return;
}