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# Copyright 2016 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.
"""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
import six
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__)
# Environment variable GCE_METADATA_HOST is originally named
# GCE_METADATA_ROOT. For compatiblity reasons, here it checks
# the new variable first; if not set, the system falls back
# to the old variable.
_GCE_METADATA_HOST = os.getenv(environment_vars.GCE_METADATA_HOST, None)
if not _GCE_METADATA_HOST:
_GCE_METADATA_HOST = os.getenv(
environment_vars.GCE_METADATA_ROOT, "metadata.google.internal"
)
_METADATA_ROOT = "http://{}/computeMetadata/v1/".format(_GCE_METADATA_HOST)
# 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, retry_count=3):
"""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.
retry_count (int): How many times to attempt connecting to metadata
server using above timeout.
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".
retries = 0
while retries < retry_count:
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 as e:
_LOGGER.warning(
"Compute Engine Metadata server unavailable on "
"attempt %s of %s. Reason: %s",
retries + 1,
retry_count,
e,
)
retries += 1
return False
def get(
request, path, root=_METADATA_ROOT, params=None, recursive=False, retry_count=5
):
"""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/default'``.
root (str): The full path to the metadata server root.
params (Optional[Mapping[str, str]]): A mapping of query parameter
keys to values.
recursive (bool): Whether to do a recursive query of metadata. See
https://cloud.google.com/compute/docs/metadata#aggcontents for more
details.
retry_count (int): How many times to attempt connecting to metadata
server using above timeout.
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 params is None else params
if recursive:
query_params["recursive"] = "true"
url = _helpers.update_query(base_url, query_params)
retries = 0
while retries < retry_count:
try:
response = request(url=url, method="GET", headers=_METADATA_HEADERS)
break
except exceptions.TransportError as e:
_LOGGER.warning(
"Compute Engine Metadata server unavailable on "
"attempt %s of %s. Reason: %s",
retries + 1,
retry_count,
e,
)
retries += 1
else:
raise exceptions.TransportError(
"Failed to retrieve {} from the Google Compute Engine"
"metadata service. Compute Engine Metadata server unavailable".format(url)
)
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 as caught_exc:
new_exc = exceptions.TransportError(
"Received invalid JSON from the Google Compute Engine"
"metadata service: {:.20}".format(content)
)
six.raise_from(new_exc, caught_exc)
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.
"""
path = "instance/service-accounts/{0}/".format(service_account)
# See https://cloud.google.com/compute/docs/metadata#aggcontents
# for more on the use of 'recursive'.
return get(request, path, params={"recursive": "true"})
def get_service_account_token(request, service_account="default", scopes=None):
"""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.
scopes (Optional[Union[str, List[str]]]): Optional string or list of
strings with auth scopes.
Returns:
Union[str, datetime]: The access token and its expiration.
Raises:
google.auth.exceptions.TransportError: if an error occurred while
retrieving metadata.
"""
if scopes:
if not isinstance(scopes, str):
scopes = ",".join(scopes)
params = {"scopes": scopes}
else:
params = None
path = "instance/service-accounts/{0}/token".format(service_account)
token_json = get(request, path, params=params)
token_expiry = _helpers.utcnow() + datetime.timedelta(
seconds=token_json["expires_in"]
)
return token_json["access_token"], token_expiry
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