Replace custom blob gRPC API with ByteStream

client/third_party/google/auth/compute_engine/_metadata.py

+# Copyright 2016 Google Inc.
+#
+# 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.
+
+"""Provides helper methods for talking to the Compute Engine metadata server.
+
+See https://cloud.google.com/compute/docs/metadata for more details.
+"""
+
+import datetime
+import json
+import logging
+import os
+
+from six.moves import http_client
+from six.moves.urllib import parse as urlparse
+
+from google.auth import _helpers
+from google.auth import environment_vars
+from google.auth import exceptions
+
+_LOGGER = logging.getLogger(__name__)
+
+_METADATA_ROOT = 'http://{}/computeMetadata/v1/'.format(
+    os.getenv(environment_vars.GCE_METADATA_ROOT, 'metadata.google.internal'))
+
+# This is used to ping the metadata server, it avoids the cost of a DNS
+# lookup.
+_METADATA_IP_ROOT = 'http://{}'.format(
+    os.getenv(environment_vars.GCE_METADATA_IP, '169.254.169.254'))
+_METADATA_FLAVOR_HEADER = 'metadata-flavor'
+_METADATA_FLAVOR_VALUE = 'Google'
+_METADATA_HEADERS = {_METADATA_FLAVOR_HEADER: _METADATA_FLAVOR_VALUE}
+
+# Timeout in seconds to wait for the GCE metadata server when detecting the
+# GCE environment.
+try:
+    _METADATA_DEFAULT_TIMEOUT = int(os.getenv('GCE_METADATA_TIMEOUT', 3))
+except ValueError:  # pragma: NO COVER
+    _METADATA_DEFAULT_TIMEOUT = 3
+
+
+def ping(request, timeout=_METADATA_DEFAULT_TIMEOUT):
+    """Checks to see if the metadata server is available.
+
+    Args:
+        request (google.auth.transport.Request): A callable used to make
+            HTTP requests.
+        timeout (int): How long to wait for the metadata server to respond.
+
+    Returns:
+        bool: True if the metadata server is reachable, False otherwise.
+    """
+    # NOTE: The explicit ``timeout`` is a workaround. The underlying
+    #       issue is that resolving an unknown host on some networks will take
+    #       20-30 seconds; making this timeout short fixes the issue, but
+    #       could lead to false negatives in the event that we are on GCE, but
+    #       the metadata resolution was particularly slow. The latter case is
+    #       "unlikely".
+    try:
+        response = request(
+            url=_METADATA_IP_ROOT, method='GET', headers=_METADATA_HEADERS,
+            timeout=timeout)
+
+        metadata_flavor = response.headers.get(_METADATA_FLAVOR_HEADER)
+        return (response.status == http_client.OK and
+                metadata_flavor == _METADATA_FLAVOR_VALUE)
+
+    except exceptions.TransportError:
+        _LOGGER.info('Compute Engine Metadata server unavailable.')
+        return False
+
+
+def get(request, path, root=_METADATA_ROOT, recursive=False):
+    """Fetch a resource from the metadata server.
+
+    Args:
+        request (google.auth.transport.Request): A callable used to make
+            HTTP requests.
+        path (str): The resource to retrieve. For example,
+            ``'instance/service-accounts/defualt'``.
+        root (str): The full path to the metadata server root.
+        recursive (bool): Whether to do a recursive query of metadata. See
+            https://cloud.google.com/compute/docs/metadata#aggcontents for more
+            details.
+
+    Returns:
+        Union[Mapping, str]: If the metadata server returns JSON, a mapping of
+            the decoded JSON is return. Otherwise, the response content is
+            returned as a string.
+
+    Raises:
+        google.auth.exceptions.TransportError: if an error occurred while
+            retrieving metadata.
+    """
+    base_url = urlparse.urljoin(root, path)
+    query_params = {}
+
+    if recursive:
+        query_params['recursive'] = 'true'
+
+    url = _helpers.update_query(base_url, query_params)
+
+    response = request(url=url, method='GET', headers=_METADATA_HEADERS)
+
+    if response.status == http_client.OK:
+        content = _helpers.from_bytes(response.data)
+        if response.headers['content-type'] == 'application/json':
+            try:
+                return json.loads(content)
+            except ValueError:
+                raise exceptions.TransportError(
+                    'Received invalid JSON from the Google Compute Engine'
+                    'metadata service: {:.20}'.format(content))
+        else:
+            return content
+    else:
+        raise exceptions.TransportError(
+            'Failed to retrieve {} from the Google Compute Engine'
+            'metadata service. Status: {} Response:\n{}'.format(
+                url, response.status, response.data), response)
+
+
+def get_project_id(request):
+    """Get the Google Cloud Project ID from the metadata server.
+
+    Args:
+        request (google.auth.transport.Request): A callable used to make
+            HTTP requests.
+
+    Returns:
+        str: The project ID
+
+    Raises:
+        google.auth.exceptions.TransportError: if an error occurred while
+            retrieving metadata.
+    """
+    return get(request, 'project/project-id')
+
+
+def get_service_account_info(request, service_account='default'):
+    """Get information about a service account from the metadata server.
+
+    Args:
+        request (google.auth.transport.Request): A callable used to make
+            HTTP requests.
+        service_account (str): The string 'default' or a service account email
+            address. The determines which service account for which to acquire
+            information.
+
+    Returns:
+        Mapping: The service account's information, for example::
+
+            {
+                'email': '...',
+                'scopes': ['scope', ...],
+                'aliases': ['default', '...']
+            }
+
+    Raises:
+        google.auth.exceptions.TransportError: if an error occurred while
+            retrieving metadata.
+    """
+    return get(
+        request,
+        'instance/service-accounts/{0}/'.format(service_account),
+        recursive=True)
+
+
+def get_service_account_token(request, service_account='default'):
+    """Get the OAuth 2.0 access token for a service account.
+
+    Args:
+        request (google.auth.transport.Request): A callable used to make
+            HTTP requests.
+        service_account (str): The string 'default' or a service account email
+            address. The determines which service account for which to acquire
+            an access token.
+
+    Returns:
+        Union[str, datetime]: The access token and its expiration.
+
+    Raises:
+        google.auth.exceptions.TransportError: if an error occurred while
+            retrieving metadata.
+    """
+    token_json = get(
+        request,
+        'instance/service-accounts/{0}/token'.format(service_account))
+    token_expiry = _helpers.utcnow() + datetime.timedelta(
+        seconds=token_json['expires_in'])
+    return token_json['access_token'], token_expiry