1# Copyright 2014 Google Inc. All Rights Reserved.
2#
3# Licensed under the Apache License, Version 2.0 (the "License");
4# you may not use this file except in compliance with the License.
5# You may obtain a copy of the License at
6#
7#      http://www.apache.org/licenses/LICENSE-2.0
8#
9# Unless required by applicable law or agreed to in writing, software
10# distributed under the License is distributed on an "AS IS" BASIS,
11# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12# See the License for the specific language governing permissions and
13# limitations under the License.
14
15"""Routines to generate root and server certificates.
16
17Certificate Naming Conventions:
18  ca_cert:  crypto.X509 for the certificate authority (w/ both the pub &
19                priv keys)
20  cert:  a crypto.X509 certificate (w/ just the pub key)
21  cert_str:  a certificate string (w/ just the pub cert)
22  key:  a private crypto.PKey  (from ca or pem)
23  ca_cert_str:  a certificae authority string (w/ both the pub & priv certs)
24"""
25
26import logging
27import os
28import platform
29import socket
30import subprocess
31import time
32
33openssl_import_error = None
34
35Error = None
36SSL_METHOD = None
37SysCallError = None
38VERIFY_PEER = None
39ZeroReturnError = None
40FILETYPE_PEM = None
41
42try:
43  from OpenSSL import crypto, SSL
44
45  Error = SSL.Error
46  SSL_METHOD = SSL.SSLv23_METHOD
47  SysCallError = SSL.SysCallError
48  VERIFY_PEER = SSL.VERIFY_PEER
49  ZeroReturnError = SSL.ZeroReturnError
50  FILETYPE_PEM = crypto.FILETYPE_PEM
51except ImportError, e:
52  openssl_import_error = e
53
54
55def get_ssl_context(method=SSL_METHOD):
56  # One of: One of SSLv2_METHOD, SSLv3_METHOD, SSLv23_METHOD, or TLSv1_METHOD
57  if openssl_import_error:
58    raise openssl_import_error  # pylint: disable=raising-bad-type
59  return SSL.Context(method)
60
61
62class WrappedConnection(object):
63
64  def __init__(self, obj):
65    self._wrapped_obj = obj
66
67  def __getattr__(self, attr):
68    if attr in self.__dict__:
69      return getattr(self, attr)
70    return getattr(self._wrapped_obj, attr)
71
72  def recv(self, buflen=1024, flags=0):
73    try:
74      return self._wrapped_obj.recv(buflen, flags)
75    except SSL.SysCallError, e:
76      if e.args[1] == 'Unexpected EOF':
77        return ''
78      raise
79    except SSL.ZeroReturnError:
80      return ''
81
82
83def get_ssl_connection(context, connection):
84  return WrappedConnection(SSL.Connection(context, connection))
85
86
87def load_privatekey(key, filetype=FILETYPE_PEM):
88  """Loads obj private key object from string."""
89  return crypto.load_privatekey(filetype, key)
90
91
92def load_cert(cert_str, filetype=FILETYPE_PEM):
93  """Loads obj cert object from string."""
94  return crypto.load_certificate(filetype, cert_str)
95
96
97def _dump_privatekey(key, filetype=FILETYPE_PEM):
98  """Dumps obj private key object to string."""
99  return crypto.dump_privatekey(filetype, key)
100
101
102def _dump_cert(cert, filetype=FILETYPE_PEM):
103  """Dumps obj cert object to string."""
104  return crypto.dump_certificate(filetype, cert)
105
106
107def generate_dummy_ca_cert(subject='_WebPageReplayCert'):
108  """Generates dummy certificate authority.
109
110  Args:
111    subject: a string representing the desired root cert issuer
112  Returns:
113    A tuple of the public key and the private key strings for the root
114    certificate
115  """
116  if openssl_import_error:
117    raise openssl_import_error  # pylint: disable=raising-bad-type
118
119  key = crypto.PKey()
120  key.generate_key(crypto.TYPE_RSA, 1024)
121
122  ca_cert = crypto.X509()
123  ca_cert.set_serial_number(int(time.time()*10000))
124  ca_cert.set_version(2)
125  ca_cert.get_subject().CN = subject
126  ca_cert.get_subject().O = subject
127  ca_cert.gmtime_adj_notBefore(-60 * 60 * 24 * 365 * 2)
128  ca_cert.gmtime_adj_notAfter(60 * 60 * 24 * 365 * 2)
129  ca_cert.set_issuer(ca_cert.get_subject())
130  ca_cert.set_pubkey(key)
131  ca_cert.add_extensions([
132      crypto.X509Extension('basicConstraints', True, 'CA:TRUE'),
133      crypto.X509Extension('nsCertType', True, 'sslCA'),
134      crypto.X509Extension('extendedKeyUsage', True,
135                           ('serverAuth,clientAuth,emailProtection,'
136                            'timeStamping,msCodeInd,msCodeCom,msCTLSign,'
137                            'msSGC,msEFS,nsSGC')),
138      crypto.X509Extension('keyUsage', False, 'keyCertSign, cRLSign'),
139      crypto.X509Extension('subjectKeyIdentifier', False, 'hash',
140                           subject=ca_cert),
141      ])
142  ca_cert.sign(key, 'sha256')
143  key_str = _dump_privatekey(key)
144  ca_cert_str = _dump_cert(ca_cert)
145  return ca_cert_str, key_str
146
147
148def get_host_cert(host, port=443):
149  """Contacts the host and returns its certificate."""
150  host_certs = []
151  def verify_cb(conn, cert, errnum, depth, ok):
152    host_certs.append(cert)
153    # Return True to indicates that the certificate was ok.
154    return True
155
156  context = SSL.Context(SSL.SSLv23_METHOD)
157  context.set_verify(SSL.VERIFY_PEER, verify_cb)  # Demand a certificate
158  s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
159  connection = SSL.Connection(context, s)
160  try:
161    connection.connect((host, port))
162    connection.send('')
163  except SSL.SysCallError:
164    pass
165  except socket.gaierror:
166    logging.debug('Host name is not valid')
167  finally:
168    connection.shutdown()
169    connection.close()
170  if not host_certs:
171    logging.warning('Unable to get host certificate from %s:%s', host, port)
172    return ''
173  return _dump_cert(host_certs[-1])
174
175
176def write_dummy_ca_cert(ca_cert_str, key_str, cert_path):
177  """Writes four certificate files.
178
179  For example, if cert_path is "mycert.pem":
180      mycert.pem - CA plus private key
181      mycert-cert.pem - CA in PEM format
182      mycert-cert.cer - CA for Android
183      mycert-cert.p12 - CA in PKCS12 format for Windows devices
184  Args:
185    cert_path: path string such as "mycert.pem"
186    ca_cert_str: certificate string
187    key_str: private key string
188  """
189  dirname = os.path.dirname(cert_path)
190  if dirname and not os.path.exists(dirname):
191    os.makedirs(dirname)
192
193  root_path = os.path.splitext(cert_path)[0]
194  ca_cert_path = root_path + '-cert.pem'
195  android_cer_path = root_path + '-cert.cer'
196  windows_p12_path = root_path + '-cert.p12'
197
198  # Dump the CA plus private key
199  with open(cert_path, 'w') as f:
200    f.write(key_str)
201    f.write(ca_cert_str)
202
203  # Dump the certificate in PEM format
204  with open(ca_cert_path, 'w') as f:
205    f.write(ca_cert_str)
206
207  # Create a .cer file with the same contents for Android
208  with open(android_cer_path, 'w') as f:
209    f.write(ca_cert_str)
210
211  ca_cert = load_cert(ca_cert_str)
212  key = load_privatekey(key_str)
213  # Dump the certificate in PKCS12 format for Windows devices
214  with open(windows_p12_path, 'w') as f:
215    p12 = crypto.PKCS12()
216    p12.set_certificate(ca_cert)
217    p12.set_privatekey(key)
218    f.write(p12.export())
219
220
221def generate_cert(root_ca_cert_str, server_cert_str, server_host):
222  """Generates a cert_str with the sni field in server_cert_str signed by the
223  root_ca_cert_str.
224
225  Args:
226    root_ca_cert_str: PEM formatted string representing the root cert
227    server_cert_str: PEM formatted string representing cert
228    server_host: host name to use if there is no server_cert_str
229  Returns:
230    a PEM formatted certificate string
231  """
232  EXTENSION_WHITELIST = set(['subjectAltName'])
233
234  if openssl_import_error:
235    raise openssl_import_error  # pylint: disable=raising-bad-type
236
237  common_name = server_host
238  reused_extensions = []
239  if server_cert_str:
240    original_cert = load_cert(server_cert_str)
241    common_name = original_cert.get_subject().commonName
242    for i in xrange(original_cert.get_extension_count()):
243      original_cert_extension = original_cert.get_extension(i)
244      if original_cert_extension.get_short_name() in EXTENSION_WHITELIST:
245        reused_extensions.append(original_cert_extension)
246
247  ca_cert = load_cert(root_ca_cert_str)
248  ca_key = load_privatekey(root_ca_cert_str)
249
250  cert = crypto.X509()
251  cert.get_subject().CN = common_name
252  cert.gmtime_adj_notBefore(-60 * 60)
253  cert.gmtime_adj_notAfter(60 * 60 * 24 * 30)
254  cert.set_issuer(ca_cert.get_subject())
255  cert.set_serial_number(int(time.time()*10000))
256  cert.set_pubkey(ca_key)
257  cert.add_extensions(reused_extensions)
258  cert.sign(ca_key, 'sha256')
259
260  return _dump_cert(cert)
261
262
263def install_cert_in_nssdb(home_directory_path, certificate_path):
264  """Installs a certificate into the ~/.pki/nssdb database.
265
266  Args:
267    home_directory_path: Path of the home directory where to install
268    certificate_path: Path of a CA in PEM format
269  """
270  assert os.path.isdir(home_directory_path)
271  assert platform.system() == 'Linux', \
272      'SSL certification authority has only been tested for linux.'
273  if (os.path.abspath(home_directory_path) ==
274          os.path.abspath(os.environ['HOME'])):
275    raise Exception('Modifying $HOME/.pki/nssdb compromises your machine.')
276
277  cert_database_path = os.path.join(home_directory_path, '.pki', 'nssdb')
278  def certutil(args):
279    cmd = ['certutil', '--empty-password', '-d', 'sql:' + cert_database_path]
280    cmd.extend(args)
281    logging.info(subprocess.list2cmdline(cmd))
282    subprocess.check_call(cmd)
283
284  if not os.path.isdir(cert_database_path):
285    os.makedirs(cert_database_path)
286    certutil(['-N'])
287
288  certutil(['-A', '-t', 'PC,,', '-n', certificate_path, '-i', certificate_path])
289