freebsd-dev/libexec/tftpd/tftp-file.c
Alan Somers 76e8e459e4 tftpd: Fix data corruption bug with netascii
Transferring files in netascii format requires, among other things,
translating all CR characters to a CR,NUL pair. tftpd does this correctly
except when the CR occurs as the last octet of a packet. In that case, it
erroneously drops the NUL which should be part of the following packet. The
bug was caused by using 0 as a sentinel value in a variable that could
legitimately hold 0. Fix it by switching the sentinel value to -1.

PR:		178055
Reported by:	Richard <rsitze@gmail.com>
Reviewed by:	cem
MFC after:	2 weeks
Differential Revision:	https://reviews.freebsd.org/D16853
2018-08-22 23:31:27 +00:00

289 lines
5.7 KiB
C

/*-
* SPDX-License-Identifier: BSD-2-Clause-FreeBSD
*
* Copyright (C) 2008 Edwin Groothuis. 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.
*
* THIS SOFTWARE IS PROVIDED BY AUTHOR 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 AUTHOR 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>
__FBSDID("$FreeBSD$");
#include <sys/types.h>
#include <sys/ioctl.h>
#include <sys/socket.h>
#include <sys/stat.h>
#include <netinet/in.h>
#include <arpa/tftp.h>
#include <assert.h>
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <syslog.h>
#include <unistd.h>
#include "tftp-file.h"
#include "tftp-utils.h"
static FILE *file;
static int convert;
static char convbuffer[66000];
static int gotcr = 0;
static size_t
convert_from_net(char *buffer, size_t count)
{
size_t i, n;
/*
* Convert all CR/LF to LF and all CR,NUL to CR
*/
n = 0;
for (i = 0; i < count; i++) {
if (gotcr == 0) {
convbuffer[n++] = buffer[i];
gotcr = (buffer[i] == '\r');
continue;
}
/* CR, NULL -> CR */
if (buffer[i] == '\0') {
gotcr = 0;
continue;
}
/* CR, LF -> LF */
if (buffer[i] == '\n') {
if (n == 0) {
if (ftell(file) != 0) {
int r = fseek(file, -1, SEEK_END);
assert(r == 0);
convbuffer[n++] = '\n';
} else {
/* This shouldn't happen */
tftp_log(LOG_ERR,
"Received LF as first character");
abort();
}
} else
convbuffer[n-1] = '\n';
gotcr = 0;
continue;
}
/* Everything else just accept as is */
convbuffer[n++] = buffer[i];
gotcr = (buffer[i] == '\r');
continue;
}
return fwrite(convbuffer, 1, n, file);
}
static size_t
convert_to_net(char *buffer, size_t count, int init)
{
size_t i;
static size_t n = 0, in = 0;
static int newline = -1;
if (init) {
newline = -1;
n = 0;
in = 0;
return 0 ;
}
/*
* Convert all LF to CR,LF and all CR to CR,NUL
*/
i = 0;
if (newline != -1) {
buffer[i++] = newline;
newline = -1;
}
while (i < count) {
if (n == in) {
/* When done we're done */
if (feof(file)) break;
/* Otherwise read another bunch */
in = fread(convbuffer, 1, count, file);
if (in == 0) break;
n = 0;
}
/* CR -> CR,NULL */
if (convbuffer[n] == '\r') {
buffer[i++] = '\r';
buffer[i++] = '\0';
n++;
continue;
}
/* LF -> CR,LF */
if (convbuffer[n] == '\n') {
buffer[i++] = '\r';
buffer[i++] = '\n';
n++;
continue;
}
buffer[i++] = convbuffer[n++];
}
if (i > count) {
/*
* Whoops... that isn't allowed (but it will happen
* when there is a CR or LF at the end of the buffer)
*/
newline = buffer[i-1];
}
if (i < count) {
/* We are done! */
return i;
} else
return count;
}
int
write_init(int fd, FILE *f, const char *mode)
{
if (f == NULL) {
file = fdopen(fd, "w");
if (file == NULL) {
int en = errno;
tftp_log(LOG_ERR, "fdopen() failed: %s",
strerror(errno));
return en;
}
} else
file = f;
convert = !strcmp(mode, "netascii");
return 0;
}
size_t
write_file(char *buffer, int count)
{
if (convert == 0)
return fwrite(buffer, 1, count, file);
return convert_from_net(buffer, count);
}
int
write_close(void)
{
if (fclose(file) != 0) {
tftp_log(LOG_ERR, "fclose() failed: %s", strerror(errno));
return 1;
}
return 0;
}
int
read_init(int fd, FILE *f, const char *mode)
{
convert_to_net(NULL, 0, 1);
if (f == NULL) {
file = fdopen(fd, "r");
if (file == NULL) {
int en = errno;
tftp_log(LOG_ERR, "fdopen() failed: %s",
strerror(errno));
return en;
}
} else
file = f;
convert = !strcmp(mode, "netascii");
return 0;
}
size_t
read_file(char *buffer, int count)
{
if (convert == 0)
return fread(buffer, 1, count, file);
return convert_to_net(buffer, count, 0);
}
int
read_close(void)
{
if (fclose(file) != 0) {
tftp_log(LOG_ERR, "fclose() failed: %s", strerror(errno));
return 1;
}
return 0;
}
/* When an error has occurred, it is possible that the two sides
* are out of synch. Ie: that what I think is the other side's
* response to packet N is really their response to packet N-1.
*
* So, to try to prevent that, we flush all the input queued up
* for us on the network connection on our host.
*
* We return the number of packets we flushed (mostly for reporting
* when trace is active).
*/
int
synchnet(int peer) /* socket to flush */
{
int i, j = 0;
char rbuf[MAXPKTSIZE];
struct sockaddr_storage from;
socklen_t fromlen;
while (1) {
(void) ioctl(peer, FIONREAD, &i);
if (i) {
j++;
fromlen = sizeof from;
(void) recvfrom(peer, rbuf, sizeof (rbuf), 0,
(struct sockaddr *)&from, &fromlen);
} else {
return(j);
}
}
}