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# Copyright 2020 Google LLC
#
# 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.
"""Utilites for mutual TLS."""
from google.auth import exceptions
from google.auth.transport import _mtls_helper
def has_default_client_cert_source():
"""Check if default client SSL credentials exists on the device.
Returns:
bool: indicating if the default client cert source exists.
"""
metadata_path = _mtls_helper._check_dca_metadata_path(
_mtls_helper.CONTEXT_AWARE_METADATA_PATH
)
return metadata_path is not None
def default_client_cert_source():
"""Get a callback which returns the default client SSL credentials.
Returns:
Callable[[], [bytes, bytes]]: A callback which returns the default
client certificate bytes and private key bytes, both in PEM format.
Raises:
google.auth.exceptions.DefaultClientCertSourceError: If the default
client SSL credentials don't exist or are malformed.
"""
if not has_default_client_cert_source():
raise exceptions.MutualTLSChannelError(
"Default client cert source doesn't exist"
)
def callback():
try:
_, cert_bytes, key_bytes = _mtls_helper.get_client_cert_and_key()
except (OSError, RuntimeError, ValueError) as caught_exc:
new_exc = exceptions.MutualTLSChannelError(caught_exc)
raise new_exc from caught_exc
return cert_bytes, key_bytes
return callback
def default_client_encrypted_cert_source(cert_path, key_path):
"""Get a callback which returns the default encrpyted client SSL credentials.
Args:
cert_path (str): The cert file path. The default client certificate will
be written to this file when the returned callback is called.
key_path (str): The key file path. The default encrypted client key will
be written to this file when the returned callback is called.
Returns:
Callable[[], [str, str, bytes]]: A callback which generates the default
client certificate, encrpyted private key and passphrase. It writes
the certificate and private key into the cert_path and key_path, and
returns the cert_path, key_path and passphrase bytes.
Raises:
google.auth.exceptions.DefaultClientCertSourceError: If any problem
occurs when loading or saving the client certificate and key.
"""
if not has_default_client_cert_source():
raise exceptions.MutualTLSChannelError(
"Default client encrypted cert source doesn't exist"
)
def callback():
try:
(
_,
cert_bytes,
key_bytes,
passphrase_bytes,
) = _mtls_helper.get_client_ssl_credentials(generate_encrypted_key=True)
with open(cert_path, "wb") as cert_file:
cert_file.write(cert_bytes)
with open(key_path, "wb") as key_file:
key_file.write(key_bytes)
except (exceptions.ClientCertError, OSError) as caught_exc:
new_exc = exceptions.MutualTLSChannelError(caught_exc)
raise new_exc from caught_exc
return cert_path, key_path, passphrase_bytes
return callback
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