273 lines
8.4 KiB
Python
273 lines
8.4 KiB
Python
# -*- coding: utf-8 -*-
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# Copyright 2020 Google Inc. All Rights Reserved.
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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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"""Manages device context mTLS certificates."""
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from __future__ import absolute_import
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from __future__ import print_function
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from __future__ import division
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from __future__ import unicode_literals
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import atexit
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import json
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import os
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from boto import config
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import gslib
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from gslib import exception
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from gslib.utils import boto_util
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from gslib.utils import execution_util
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# Maintain a single context configuration.
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_singleton_config = None
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# Metadata JSON that stores information about the default certificate provider.
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_DEFAULT_METADATA_PATH = os.path.expanduser(
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os.path.join('~', '.secureConnect', 'context_aware_metadata.json'))
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_CERT_PROVIDER_COMMAND = "cert_provider_command"
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_CERT_PROVIDER_COMMAND_PASSPHRASE_OPTION = "--with_passphrase"
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class CertProvisionError(Exception):
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"""Represents errors when provisioning a client certificate."""
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pass
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class ContextConfigSingletonAlreadyExistsError(Exception):
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"""Error for when create_context_config is called multiple times."""
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pass
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def _is_pem_section_marker(line):
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"""Returns (begin:bool, end:bool, name:str)."""
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if line.startswith('-----BEGIN ') and line.endswith('-----'):
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return True, False, line[11:-5]
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elif line.startswith('-----END ') and line.endswith('-----'):
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return False, True, line[9:-5]
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else:
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return False, False, ''
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def _split_pem_into_sections(contents, logger):
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"""Returns dict with {name: section} by parsing contents in PEM format.
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A simple parser for PEM file. Please see RFC 7468 for the format of PEM
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file. Not using regex to improve performance catching nested matches.
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Note: This parser requires the post-encapsulation label of a section to
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match its pre-encapsulation label. It ignores a section without a
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matching label.
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Args:
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contents (str): Contents of a PEM file.
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logger (logging.logger): gsutil logger.
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Returns:
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A dict of the PEM file sections.
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"""
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result = {}
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pem_lines = []
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pem_section_name = None
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for line in contents.splitlines():
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line = line.strip()
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if not line:
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continue
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begin, end, name = _is_pem_section_marker(line)
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if begin:
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if pem_section_name:
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logger.warning('Section %s missing end line and will be ignored.' %
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pem_section_name)
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if name in result.keys():
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logger.warning('Section %s already exists, and the older section will '
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'be ignored.' % name)
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pem_section_name = name
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pem_lines = []
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elif end:
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if not pem_section_name:
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logger.warning(
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'Section %s missing a beginning line and will be ignored.' % name)
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elif pem_section_name != name:
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logger.warning('Section %s missing a matching end line. Found: %s' %
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(pem_section_name, name))
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pem_section_name = None
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if pem_section_name:
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pem_lines.append(line)
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if end:
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result[name] = '\n'.join(pem_lines) + '\n'
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pem_section_name = None
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if pem_section_name:
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logger.warning('Section %s missing an end line.' % pem_section_name)
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return result
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def _check_path():
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"""Checks for content aware metadata.
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If content aware metadata exists, return its absolute path;
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otherwise, returns None.
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Returns:
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str: Absolute path if exists. Otherwise, None.
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"""
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metadata_path = os.path.expanduser(_DEFAULT_METADATA_PATH)
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if not os.path.exists(metadata_path):
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return None
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return metadata_path
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def _read_metadata_file(metadata_path):
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"""Loads context aware metadata from the given path.
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Returns:
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dict: The metadata JSON.
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Raises:
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CertProvisionError: If failed to parse metadata as JSON.
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"""
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try:
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with open(metadata_path) as f:
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return json.load(f)
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except ValueError as e:
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raise CertProvisionError(e)
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def _default_command():
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"""Loads default cert provider command.
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Returns:
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str: The default command.
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Raises:
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CertProvisionError: If command cannot be found.
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"""
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metadata_path = _check_path()
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if not metadata_path:
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raise CertProvisionError("Client certificate provider file not found.")
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metadata_json = _read_metadata_file(metadata_path)
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if _CERT_PROVIDER_COMMAND not in metadata_json:
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raise CertProvisionError("Client certificate provider command not found.")
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command = metadata_json[_CERT_PROVIDER_COMMAND]
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if (_CERT_PROVIDER_COMMAND_PASSPHRASE_OPTION not in command):
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command.append(_CERT_PROVIDER_COMMAND_PASSPHRASE_OPTION)
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return command
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class _ContextConfig(object):
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"""Represents the configurations associated with context aware access.
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Only one instance of Config can be created for the program.
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"""
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def __init__(self, logger):
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"""Initializes config.
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Args:
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logger (logging.logger): gsutil logger.
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"""
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self.logger = logger
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self.use_client_certificate = config.getbool('Credentials',
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'use_client_certificate')
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self.client_cert_path = None
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if not self.use_client_certificate:
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# Don't spend time generating values gsutil won't need.
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return
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# Generates certificate and deletes it afterwards.
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atexit.register(self._unprovision_client_cert)
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self.client_cert_path = os.path.join(boto_util.GetGsutilStateDir(),
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'caa_cert.pem')
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try:
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# Certs provisioned using endpoint verification are stored as a
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# single file holding both the public certificate and the private key.
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self._provision_client_cert(self.client_cert_path)
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except CertProvisionError as e:
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self.logger.error('Failed to provision client certificate: %s' % e)
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def _provision_client_cert(self, cert_path):
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"""Executes certificate provider to obtain client certificate and keys."""
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cert_command_string = config.get('Credentials', 'cert_provider_command',
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None)
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if cert_command_string:
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cert_command = cert_command_string.split(' ')
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else:
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# Load the default certificate provider if sit is not provided by user.
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cert_command = _default_command()
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try:
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command_stdout_string, _ = execution_util.ExecuteExternalCommand(
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cert_command)
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sections = _split_pem_into_sections(command_stdout_string, self.logger)
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with open(cert_path, 'w+') as f:
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f.write(sections['CERTIFICATE'])
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if 'ENCRYPTED PRIVATE KEY' in sections:
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f.write(sections['ENCRYPTED PRIVATE KEY'])
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self.client_cert_password = sections['PASSPHRASE'].splitlines()[1]
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else:
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f.write(sections['PRIVATE KEY'])
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self.client_cert_password = None
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except (exception.ExternalBinaryError, OSError) as e:
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raise CertProvisionError(e)
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except KeyError as e:
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raise CertProvisionError(
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'Invalid output format from certificate provider, no %s' % e)
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def _unprovision_client_cert(self):
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"""Cleans up any files or resources provisioned during config init."""
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if self.client_cert_path is not None:
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try:
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os.remove(self.client_cert_path)
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self.logger.debug('Unprovisioned client cert: %s' %
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self.client_cert_path)
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except OSError as e:
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self.logger.error('Failed to remove client certificate: %s' % e)
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def create_context_config(logger):
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"""Should be run once at gsutil startup. Creates global singleton.
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Args:
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logger (logging.logger): For logging during config functions.
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Returns:
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New ContextConfig singleton.
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Raises:
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Exception if singleton already exists.
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"""
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global _singleton_config
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if not _singleton_config:
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_singleton_config = _ContextConfig(logger)
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return _singleton_config
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raise ContextConfigSingletonAlreadyExistsError
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def get_context_config():
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"""Retrieves ContextConfig global singleton.
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Returns:
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ContextConfig or None if global singleton doesn't exist.
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"""
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return _singleton_config
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