text: #!/usr/bin/python
  # Copyright (c) 2017 The Chromium Authors. All rights reserved.
  # Use of this source code is governed by a BSD-style license that can be
  # found in the LICENSE file.
  
  """Generates a variety of chains where the target certificate varies in its key
  type and key usages."""
  
  import sys
  sys.path += ['..']
  
  import common
  
  # Self-signed root certificate (used as trust anchor).
  root = common.create_self_signed_root_certificate('Root')
  
  # Intermediate certificate.
  intermediate = common.create_intermediate_certificate('Intermediate', root)
  
  # Use either an RSA key, or an EC key for the target certificate. Generate the
  # possible keys ahead of time so as not to duplicate the work.
  
  KEYS = {
    'rsa': common.get_or_generate_rsa_key(2048,
                                          common.create_key_path('Target-rsa')),
    'ec': common.get_or_generate_ec_key('secp384r1',
                                        common.create_key_path('Target-ec'))
  };
  
  KEY_USAGES = [ 'decipherOnly',
                 'digitalSignature',
                 'keyAgreement',
                 'keyEncipherment' ]
  
  # The proper key usage depends on the key purpose (serverAuth in this case),
  # and the key type. Generate a variety of combinations.
  for key_type in sorted(KEYS.keys()):
    for key_usage in KEY_USAGES:
      # Target certificate.
      target = common.create_end_entity_certificate('Target', intermediate)
      target.get_extensions().set_property('extendedKeyUsage', 'serverAuth')
      target.get_extensions().set_property('keyUsage',
                                           'critical,%s' % (key_usage))
  
      # Set the key.
      target.set_key(KEYS[key_type])
  
      # Write the chain.
      chain = [target, intermediate, root]
      description = ('Certificate chain where the target certificate uses a %s '
                     'key and has the single key usage %s') % (key_type.upper(),
                                                               key_usage)
      common.write_chain(description, chain, '%s-%s.pem' % (key_type, key_usage))
  