300 lines
10 KiB
Python
300 lines
10 KiB
Python
# Copyright 2020 Google LLC
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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"""Utilites for mutual TLS."""
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import enum
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import logging
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from os import getenv
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import ssl
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from typing import Optional
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from google.auth import environment_vars
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from google.auth import exceptions
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from google.auth.transport import _mtls_helper
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_LOGGER = logging.getLogger(__name__)
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class UseMtlsEndpointMode(enum.Enum):
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ALWAYS = "always"
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NEVER = "never"
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AUTO = "auto"
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def has_default_client_cert_source(include_context_aware=True):
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"""Check if default client SSL credentials exists on the device.
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Args:
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include_context_aware (bool): include_context_aware indicates if context_aware
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path location will be checked or should it be skipped.
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Returns:
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bool: indicating if the default client cert source exists.
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"""
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cert_path = _mtls_helper._get_cert_config_path(
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include_context_aware=include_context_aware
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)
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if cert_path is not None:
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return True
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if (
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include_context_aware
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and _mtls_helper._check_config_path(_mtls_helper.CONTEXT_AWARE_METADATA_PATH)
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is not None
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):
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return True
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return False
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def default_client_cert_source():
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"""Get a callback which returns the default client SSL credentials.
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Returns:
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Callable[[], [bytes, bytes]]: A callback which returns the default
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client certificate bytes and private key bytes, both in PEM format.
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Raises:
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google.auth.exceptions.MutualTLSChannelError: If the default
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client SSL credentials don't exist or are malformed.
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"""
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if not has_default_client_cert_source(include_context_aware=True):
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raise exceptions.MutualTLSChannelError(
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"Default client cert source doesn't exist"
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)
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def callback():
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try:
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_, cert_bytes, key_bytes = _mtls_helper.get_client_cert_and_key()
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except (OSError, RuntimeError, ValueError) as caught_exc:
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new_exc = exceptions.MutualTLSChannelError(caught_exc)
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raise new_exc from caught_exc
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return cert_bytes, key_bytes
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return callback
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def default_client_encrypted_cert_source(cert_path, key_path):
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"""Get a callback which returns the default encrpyted client SSL credentials.
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Args:
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cert_path (str): The cert file path. The default client certificate will
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be written to this file when the returned callback is called.
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key_path (str): The key file path. The default encrypted client key will
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be written to this file when the returned callback is called.
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Returns:
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Callable[[], [str, str, bytes]]: A callback which generates the default
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client certificate, encrpyted private key and passphrase. It writes
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the certificate and private key into the cert_path and key_path, and
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returns the cert_path, key_path and passphrase bytes.
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Raises:
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google.auth.exceptions.MutualTLSChannelError: If any problem
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occurs when loading or saving the client certificate and key.
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"""
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if not has_default_client_cert_source(include_context_aware=True):
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raise exceptions.MutualTLSChannelError(
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"Default client encrypted cert source doesn't exist"
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)
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def callback():
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try:
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(
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_,
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cert_bytes,
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key_bytes,
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passphrase_bytes,
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) = _mtls_helper.get_client_ssl_credentials(generate_encrypted_key=True)
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with open(cert_path, "wb") as cert_file:
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cert_file.write(cert_bytes)
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with open(key_path, "wb") as key_file:
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key_file.write(key_bytes)
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except (exceptions.ClientCertError, OSError) as caught_exc:
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new_exc = exceptions.MutualTLSChannelError(caught_exc)
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raise new_exc from caught_exc
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return cert_path, key_path, passphrase_bytes
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return callback
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def should_use_client_cert():
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"""Returns boolean for whether the client certificate should be used for mTLS.
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This is a wrapper around _mtls_helper.check_use_client_cert().
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If GOOGLE_API_USE_CLIENT_CERTIFICATE is set to true or false, a corresponding
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bool value will be returned
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If GOOGLE_API_USE_CLIENT_CERTIFICATE is unset, the value will be inferred by
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reading a file pointed at by GOOGLE_API_CERTIFICATE_CONFIG or
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CLOUDSDK_CONTEXT_AWARE_CERTIFICATE_CONFIG_FILE_PATH, or the default path
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like ~/.config/gcloud/certificate_config.json, and verifying it
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contains a "workload" section. If so, the function will return True,
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otherwise False.
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Returns:
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bool: indicating whether the client certificate should be used for mTLS.
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"""
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return _mtls_helper.check_use_client_cert()
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def _load_client_cert_into_context(
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ctx: ssl.SSLContext,
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cert_bytes: bytes,
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key_bytes: bytes,
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passphrase: Optional[bytes] = None,
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) -> None:
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"""Load a client certificate and key into an SSL context.
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Args:
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ctx (ssl.SSLContext): The SSL context to load the certificate and key into.
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cert_bytes (bytes): The client certificate bytes in PEM format.
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key_bytes (bytes): The client private key bytes in PEM format.
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passphrase (Optional[bytes]): The passphrase for the client private key.
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Raises:
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google.auth.exceptions.MutualTLSChannelError: If the SSL context is invalid,
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or if loading the certificate and key fails.
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"""
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if not isinstance(ctx, ssl.SSLContext):
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raise exceptions.MutualTLSChannelError(
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"Failed to load client certificate and key for mTLS. The provided context "
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"object is invalid or does not support loading certificate chains."
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)
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try:
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with _mtls_helper.secure_cert_key_paths(
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cert_bytes, key_bytes, passphrase=passphrase
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) as (
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cert_path,
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key_path,
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passphrase_val,
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):
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if cert_path is None or key_path is None:
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raise exceptions.MutualTLSChannelError(
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"Failed to generate temporary file paths for the client certificate and key."
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)
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ctx.load_cert_chain(
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certfile=cert_path, keyfile=key_path, password=passphrase_val
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)
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except (
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ssl.SSLError,
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OSError,
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ValueError,
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RuntimeError,
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TypeError,
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) as caught_exc:
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new_exc = exceptions.MutualTLSChannelError(caught_exc)
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raise new_exc from caught_exc
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def load_default_client_cert(ctx: ssl.SSLContext) -> bool:
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"""Load the default client certificate and key into an SSL context if configured.
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If client certificates are enabled and a default client certificate source is
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found, the certificate and key are loaded into the SSL context.
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Args:
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ctx (ssl.SSLContext): The SSL context to load the default client certificate
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and key into.
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Returns:
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bool: True if client certificates are enabled and the default client
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certificate was successfully loaded. False if client certificates
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are disabled or if no default certificate source is configured.
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Raises:
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google.auth.exceptions.MutualTLSChannelError: If the default client certificate
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or key is malformed.
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"""
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if not should_use_client_cert() or not has_default_client_cert_source():
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return False
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try:
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(
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has_cert,
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cert_bytes,
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key_bytes,
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passphrase,
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) = _mtls_helper.get_client_ssl_credentials()
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except (
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exceptions.ClientCertError,
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OSError,
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RuntimeError,
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ValueError,
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) as caught_exc:
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new_exc = exceptions.MutualTLSChannelError(caught_exc)
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raise new_exc from caught_exc
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else:
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if not has_cert:
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return False
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_load_client_cert_into_context(ctx, cert_bytes, key_bytes, passphrase)
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return True
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def get_default_ssl_context() -> Optional[ssl.SSLContext]:
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"""Get a default SSL context loaded with the default client certificate.
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Returns:
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ssl.SSLContext: An SSL context loaded with the default client
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certificate, or None if client certificates are not configured
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or available.
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Raises:
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google.auth.exceptions.MutualTLSChannelError: If the default client certificate
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or key is malformed.
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"""
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if not should_use_client_cert() or not has_default_client_cert_source():
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return None
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ctx = ssl.create_default_context(ssl.Purpose.SERVER_AUTH)
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return ctx if load_default_client_cert(ctx) else None
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def should_use_mtls_endpoint(
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client_cert_available: Optional[bool] = None,
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) -> bool:
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"""Determine whether to use an mTLS endpoint.
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This relies on the GOOGLE_API_USE_MTLS_ENDPOINT environment variable. If set to
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"always", returns True. If set to "never", returns False. If set to "auto"
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or unset, returns whether a client certificate is available.
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Args:
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client_cert_available (Optional[bool]): indicating if a client certificate
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is available. If None, this is determined by checking if client
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certificates are enabled using :func:`should_use_client_cert`.
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Returns:
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bool: indicating if an mTLS endpoint should be used.
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"""
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if client_cert_available is None:
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client_cert_available = should_use_client_cert()
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use_mtls_endpoint = getenv(environment_vars.GOOGLE_API_USE_MTLS_ENDPOINT)
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use_mtls_endpoint = (use_mtls_endpoint or "auto").strip().lower()
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try:
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mode = UseMtlsEndpointMode(use_mtls_endpoint)
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except ValueError:
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raise exceptions.MutualTLSChannelError(
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f"Unsupported {environment_vars.GOOGLE_API_USE_MTLS_ENDPOINT} value "
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f"'{use_mtls_endpoint}'. Accepted values: never, auto, always."
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)
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if mode == UseMtlsEndpointMode.ALWAYS:
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return True
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if mode == UseMtlsEndpointMode.NEVER:
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return False
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if mode == UseMtlsEndpointMode.AUTO:
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return client_cert_available
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