sslproxy.py

# Copyright 2014 Google Inc. All Rights Reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#      http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

"""Extends BaseHTTPRequestHandler with SSL certificate generation."""

import logging
import socket

import certutils


class SslHandshakeHandler:
  """Handles Server Name Indication (SNI) using dummy certs."""

  def setup(self):
    """Sets up connection providing the certificate to the client."""
    # One of: One of SSLv2_METHOD, SSLv3_METHOD, SSLv23_METHOD, or TLSv1_METHOD
    context = certutils.get_ssl_context()
    def handle_servername(connection):
      """A SNI callback that happens during do_handshake()."""
      try:
        host = connection.get_servername()
        if host:
          cert_str = (
              self.server.get_certificate(host))
          new_context = certutils.get_ssl_context()
          cert = certutils.load_cert(cert_str)
          new_context.use_certificate(cert)
          new_context.use_privatekey_file(self.server.ca_cert_path)
          connection.set_context(new_context)
          return new_context
        # else: fail with 'no shared cipher'
      except Exception, e:
        # Do not leak any exceptions or else openssl crashes.
        logging.error('Exception in SNI handler: %s', e)

    context.set_tlsext_servername_callback(handle_servername)
    self.connection = certutils.get_ssl_connection(context, self.connection)
    self.connection.set_accept_state()
    try:
      self.connection.do_handshake()
    except certutils.Error, v:
      host = self.connection.get_servername()
      if not host:
        logging.error('Dropping request without SNI')
        return ''
      raise certutils.Error('SSL handshake error %s: %s' % (host, str(v)))

    # Re-wrap the read/write streams with our new connection.
    self.rfile = socket._fileobject(self.connection, 'rb', self.rbufsize,
                                    close=False)
    self.wfile = socket._fileobject(self.connection, 'wb', self.wbufsize,
                                    close=False)

  def finish(self):
    self.connection.shutdown()
    self.connection.close()


def wrap_handler(handler_class):
  """Wraps a BaseHTTPHandler with SSL MITM certificates."""
  if certutils.openssl_import_error:
    raise certutils.openssl_import_error

  class WrappedHandler(SslHandshakeHandler, handler_class):

    def setup(self):
      handler_class.setup(self)
      SslHandshakeHandler.setup(self)

    def finish(self):
      handler_class.finish(self)
      SslHandshakeHandler.finish(self)
  return WrappedHandler