1# Copyright 2020 Google LLC
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"""Utilites for mutual TLS."""
16
17from google.auth import exceptions
18from google.auth.transport import _mtls_helper
19
20
21def has_default_client_cert_source():
22 """Check if default client SSL credentials exists on the device.
23
24 Returns:
25 bool: indicating if the default client cert source exists.
26 """
27 if (
28 _mtls_helper._check_config_path(_mtls_helper.CONTEXT_AWARE_METADATA_PATH)
29 is not None
30 ):
31 return True
32 if (
33 _mtls_helper._check_config_path(
34 _mtls_helper.CERTIFICATE_CONFIGURATION_DEFAULT_PATH
35 )
36 is not None
37 ):
38 return True
39 return False
40
41
42def default_client_cert_source():
43 """Get a callback which returns the default client SSL credentials.
44
45 Returns:
46 Callable[[], [bytes, bytes]]: A callback which returns the default
47 client certificate bytes and private key bytes, both in PEM format.
48
49 Raises:
50 google.auth.exceptions.DefaultClientCertSourceError: If the default
51 client SSL credentials don't exist or are malformed.
52 """
53 if not has_default_client_cert_source():
54 raise exceptions.MutualTLSChannelError(
55 "Default client cert source doesn't exist"
56 )
57
58 def callback():
59 try:
60 _, cert_bytes, key_bytes = _mtls_helper.get_client_cert_and_key()
61 except (OSError, RuntimeError, ValueError) as caught_exc:
62 new_exc = exceptions.MutualTLSChannelError(caught_exc)
63 raise new_exc from caught_exc
64
65 return cert_bytes, key_bytes
66
67 return callback
68
69
70def default_client_encrypted_cert_source(cert_path, key_path):
71 """Get a callback which returns the default encrpyted client SSL credentials.
72
73 Args:
74 cert_path (str): The cert file path. The default client certificate will
75 be written to this file when the returned callback is called.
76 key_path (str): The key file path. The default encrypted client key will
77 be written to this file when the returned callback is called.
78
79 Returns:
80 Callable[[], [str, str, bytes]]: A callback which generates the default
81 client certificate, encrpyted private key and passphrase. It writes
82 the certificate and private key into the cert_path and key_path, and
83 returns the cert_path, key_path and passphrase bytes.
84
85 Raises:
86 google.auth.exceptions.DefaultClientCertSourceError: If any problem
87 occurs when loading or saving the client certificate and key.
88 """
89 if not has_default_client_cert_source():
90 raise exceptions.MutualTLSChannelError(
91 "Default client encrypted cert source doesn't exist"
92 )
93
94 def callback():
95 try:
96 (
97 _,
98 cert_bytes,
99 key_bytes,
100 passphrase_bytes,
101 ) = _mtls_helper.get_client_ssl_credentials(generate_encrypted_key=True)
102 with open(cert_path, "wb") as cert_file:
103 cert_file.write(cert_bytes)
104 with open(key_path, "wb") as key_file:
105 key_file.write(key_bytes)
106 except (exceptions.ClientCertError, OSError) as caught_exc:
107 new_exc = exceptions.MutualTLSChannelError(caught_exc)
108 raise new_exc from caught_exc
109
110 return cert_path, key_path, passphrase_bytes
111
112 return callback