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# Copyright 2007,2011 Google Inc.
#
# 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.
#

# This file is derived from
# http://googleappengine.googlecode.com/svn-history/r136/trunk/python/google/appengine/tools/https_wrapper.py


"""Extensions to allow HTTPS requests with SSL certificate validation."""

import httplib
import re
import socket
import ssl

import boto

class InvalidCertificateException(httplib.HTTPException):
  """Raised when a certificate is provided with an invalid hostname."""

  def __init__(self, host, cert, reason):
    """Constructor.

Args:
host: The hostname the connection was made to.
cert: The SSL certificate (as a dictionary) the host returned.
"""
    httplib.HTTPException.__init__(self)
    self.host = host
    self.cert = cert
    self.reason = reason

  def __str__(self):
    return ('Host %s returned an invalid certificate (%s): %s' %
            (self.host, self.reason, self.cert))

def GetValidHostsForCert(cert):
  """Returns a list of valid host globs for an SSL certificate.

Args:
cert: A dictionary representing an SSL certificate.
Returns:
list: A list of valid host globs.
"""
  if 'subjectAltName' in cert:
    return [x[1] for x in cert['subjectAltName'] if x[0].lower() == 'dns']
  else:
    return [x[0][1] for x in cert['subject']
            if x[0][0].lower() == 'commonname']

def ValidateCertificateHostname(cert, hostname):
  """Validates that a given hostname is valid for an SSL certificate.

Args:
cert: A dictionary representing an SSL certificate.
hostname: The hostname to test.
Returns:
bool: Whether or not the hostname is valid for this certificate.
"""
  hosts = GetValidHostsForCert(cert)
  boto.log.debug(
      "validating server certificate: hostname=%s, certificate hosts=%s",
      hostname, hosts)
  for host in hosts:
    host_re = host.replace('.', '\.').replace('*', '[^.]*')
    if re.search('^%s$' % (host_re,), hostname, re.I):
      return True
  return False


class CertValidatingHTTPSConnection(httplib.HTTPConnection):
  """An HTTPConnection that connects over SSL and validates certificates."""

  default_port = httplib.HTTPS_PORT

  def __init__(self, host, port=default_port, key_file=None, cert_file=None,
               ca_certs=None, strict=None, **kwargs):
    """Constructor.

Args:
host: The hostname. Can be in 'host:port' form.
port: The port. Defaults to 443.
key_file: A file containing the client's private key
cert_file: A file containing the client's certificates
ca_certs: A file contianing a set of concatenated certificate authority
certs for validating the server against.
strict: When true, causes BadStatusLine to be raised if the status line
can't be parsed as a valid HTTP/1.0 or 1.1 status line.
"""
    httplib.HTTPConnection.__init__(self, host, port, strict, **kwargs)
    self.key_file = key_file
    self.cert_file = cert_file
    self.ca_certs = ca_certs

  def connect(self):
    "Connect to a host on a given (SSL) port."
    sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    if hasattr(self, "timeout") and self.timeout is not socket._GLOBAL_DEFAULT_TIMEOUT:
        sock.settimeout(self.timeout)
    sock.connect((self.host, self.port))
    msg = "wrapping ssl socket; "
    if self.ca_certs:
        msg += "CA certificate file=%s" %self.ca_certs
    else:
        msg += "using system provided SSL certs"
    boto.log.debug(msg)
    self.sock = ssl.wrap_socket(sock, keyfile=self.key_file,
                                certfile=self.cert_file,
                                cert_reqs=ssl.CERT_REQUIRED,
                                ca_certs=self.ca_certs)
    cert = self.sock.getpeercert()
    hostname = self.host.split(':', 0)[0]
    if not ValidateCertificateHostname(cert, hostname):
      raise InvalidCertificateException(hostname,
                                        cert,
                                        'remote hostname "%s" does not match '\
                                        'certificate' % hostname)
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