feat: added system tests for the asyncIO auth changes and async id_to…

…ken credentials (#574)

* feat: asyncio http request logic and asynchronous credentials log c

* feat: all asynchronous credentials types implemented and with tests

* included system tests for the asynchronous auth library

* feat: added the private scope for Response class

* feat: added docstring for Auth Session request method

* fix: Changed initialization of client session to within an async context manager

* changed aiohttp_requests abbreviation for the async authorized session class

* fix: changed abbrevation of the aiohttp_requests file

* fix: comments on PR regarding shared data between requests and aiohttp_requests

* fix: fixed noxfile test dependency sharing

* fix: fixed the noxfile dependencies between sync and async unit tests

* fix: cover async dependency

* fix: merge conflict issue with credentials

* fix: merge conflict #2

* fix: changed duplicated constants for sync-->async inheritance relationship

* fix: async docstring

* refactoring

* fix: refactoring

* fix: first round of comments, refactoring and test duplication changes

* fix: removed duplication in _default_async

* compute engine and metadata changes

* fix: removed oauth2 client

* added further system tests and refactored

* modified aiohttp request docstring

* refactoring and fixing comments

* refactored system tests and re-wrote nox file

* metadata typo

* fix: nox file tests added

* fix: directory path in app_engine

google/oauth2/id_token_async.py

@@ -0,0 +1,267 @@
+# 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.
+
+"""Google ID Token helpers.
+
+Provides support for verifying `OpenID Connect ID Tokens`_, especially ones
+generated by Google infrastructure.
+
+To parse and verify an ID Token issued by Google's OAuth 2.0 authorization
+server use :func:`verify_oauth2_token`. To verify an ID Token issued by
+Firebase, use :func:`verify_firebase_token`.
+
+A general purpose ID Token verifier is available as :func:`verify_token`.
+
+Example::
+
+    from google.oauth2 import id_token_async
+    from google.auth.transport import aiohttp_requests
+
+    request = aiohttp_requests.Request()
+
+    id_info = await id_token_async.verify_oauth2_token(
+        token, request, 'my-client-id.example.com')
+
+    if id_info['iss'] != 'https://accounts.google.com':
+        raise ValueError('Wrong issuer.')
+
+    userid = id_info['sub']
+
+By default, this will re-fetch certificates for each verification. Because
+Google's public keys are only changed infrequently (on the order of once per
+day), you may wish to take advantage of caching to reduce latency and the
+potential for network errors. This can be accomplished using an external
+library like `CacheControl`_ to create a cache-aware
+:class:`google.auth.transport.Request`::
+
+    import cachecontrol
+    import google.auth.transport.requests
+    import requests
+
+    session = requests.session()
+    cached_session = cachecontrol.CacheControl(session)
+    request = google.auth.transport.requests.Request(session=cached_session)
+
+.. _OpenID Connect ID Token:
+    http://openid.net/specs/openid-connect-core-1_0.html#IDToken
+.. _CacheControl: https://cachecontrol.readthedocs.io
+"""
+
+import json
+import os
+
+import six
+from six.moves import http_client
+
+from google.auth import environment_vars
+from google.auth import exceptions
+from google.auth import jwt
+from google.auth.transport import requests
+from google.oauth2 import id_token as sync_id_token
+
+
+async def _fetch_certs(request, certs_url):
+    """Fetches certificates.
+
+    Google-style cerificate endpoints return JSON in the format of
+    ``{'key id': 'x509 certificate'}``.
+
+    Args:
+        request (google.auth.transport.Request): The object used to make
+            HTTP requests. This must be an aiohttp request.
+        certs_url (str): The certificate endpoint URL.
+
+    Returns:
+        Mapping[str, str]: A mapping of public key ID to x.509 certificate
+            data.
+    """
+    response = await request(certs_url, method="GET")
+
+    if response.status != http_client.OK:
+        raise exceptions.TransportError(
+            "Could not fetch certificates at {}".format(certs_url)
+        )
+
+    data = await response.data.read()
+
+    return json.loads(json.dumps(data))
+
+
+async def verify_token(
+    id_token, request, audience=None, certs_url=sync_id_token._GOOGLE_OAUTH2_CERTS_URL
+):
+    """Verifies an ID token and returns the decoded token.
+
+    Args:
+        id_token (Union[str, bytes]): The encoded token.
+        request (google.auth.transport.Request): The object used to make
+            HTTP requests. This must be an aiohttp request.
+        audience (str): The audience that this token is intended for. If None
+            then the audience is not verified.
+        certs_url (str): The URL that specifies the certificates to use to
+            verify the token. This URL should return JSON in the format of
+            ``{'key id': 'x509 certificate'}``.
+
+    Returns:
+        Mapping[str, Any]: The decoded token.
+    """
+    certs = await _fetch_certs(request, certs_url)
+
+    return jwt.decode(id_token, certs=certs, audience=audience)
+
+
+async def verify_oauth2_token(id_token, request, audience=None):
+    """Verifies an ID Token issued by Google's OAuth 2.0 authorization server.
+
+    Args:
+        id_token (Union[str, bytes]): The encoded token.
+        request (google.auth.transport.Request): The object used to make
+            HTTP requests. This must be an aiohttp request.
+        audience (str): The audience that this token is intended for. This is
+            typically your application's OAuth 2.0 client ID. If None then the
+            audience is not verified.
+
+    Returns:
+        Mapping[str, Any]: The decoded token.
+
+    Raises:
+        exceptions.GoogleAuthError: If the issuer is invalid.
+    """
+    idinfo = await verify_token(
+        id_token,
+        request,
+        audience=audience,
+        certs_url=sync_id_token._GOOGLE_OAUTH2_CERTS_URL,
+    )
+
+    if idinfo["iss"] not in sync_id_token._GOOGLE_ISSUERS:
+        raise exceptions.GoogleAuthError(
+            "Wrong issuer. 'iss' should be one of the following: {}".format(
+                sync_id_token._GOOGLE_ISSUERS
+            )
+        )
+
+    return idinfo
+
+
+async def verify_firebase_token(id_token, request, audience=None):
+    """Verifies an ID Token issued by Firebase Authentication.
+
+    Args:
+        id_token (Union[str, bytes]): The encoded token.
+        request (google.auth.transport.Request): The object used to make
+            HTTP requests. This must be an aiohttp request.
+        audience (str): The audience that this token is intended for. This is
+            typically your Firebase application ID. If None then the audience
+            is not verified.
+
+    Returns:
+        Mapping[str, Any]: The decoded token.
+    """
+    return await verify_token(
+        id_token,
+        request,
+        audience=audience,
+        certs_url=sync_id_token._GOOGLE_APIS_CERTS_URL,
+    )
+
+
+async def fetch_id_token(request, audience):
+    """Fetch the ID Token from the current environment.
+
+    This function acquires ID token from the environment in the following order:
+
+    1. If the application is running in Compute Engine, App Engine or Cloud Run,
+       then the ID token are obtained from the metadata server.
+    2. If the environment variable ``GOOGLE_APPLICATION_CREDENTIALS`` is set
+       to the path of a valid service account JSON file, then ID token is
+       acquired using this service account credentials.
+    3. If metadata server doesn't exist and no valid service account credentials
+       are found, :class:`~google.auth.exceptions.DefaultCredentialsError` will
+       be raised.
+
+    Example::
+
+        import google.oauth2.id_token_async
+        import google.auth.transport.aiohttp_requests
+
+        request = google.auth.transport.aiohttp_requests.Request()
+        target_audience = "https://pubsub.googleapis.com"
+
+        id_token = await google.oauth2.id_token_async.fetch_id_token(request, target_audience)
+
+    Args:
+        request (google.auth.transport.aiohttp_requests.Request): A callable used to make
+            HTTP requests.
+        audience (str): The audience that this ID token is intended for.
+
+    Returns:
+        str: The ID token.
+
+    Raises:
+        ~google.auth.exceptions.DefaultCredentialsError:
+            If metadata server doesn't exist and no valid service account
+            credentials are found.
+    """
+    # 1. First try to fetch ID token from metadata server if it exists. The code
+    # works for GAE and Cloud Run metadata server as well.
+    try:
+        from google.auth import compute_engine
+
+        request_new = requests.Request()
+        credentials = compute_engine.IDTokenCredentials(
+            request_new, audience, use_metadata_identity_endpoint=True
+        )
+        credentials.refresh(request_new)
+
+        return credentials.token
+
+    except (ImportError, exceptions.TransportError, exceptions.RefreshError):
+        pass
+
+    # 2. Try to use service account credentials to get ID token.
+
+    # Try to get credentials from the GOOGLE_APPLICATION_CREDENTIALS environment
+    # variable.
+    credentials_filename = os.environ.get(environment_vars.CREDENTIALS)
+    if not (
+        credentials_filename
+        and os.path.exists(credentials_filename)
+        and os.path.isfile(credentials_filename)
+    ):
+        raise exceptions.DefaultCredentialsError(
+            "Neither metadata server or valid service account credentials are found."
+        )
+
+    try:
+        with open(credentials_filename, "r") as f:
+            info = json.load(f)
+            credentials_content = (
+                (info.get("type") == "service_account") and info or None
+            )
+
+            from google.oauth2 import service_account_async as service_account
+
+            credentials = service_account.IDTokenCredentials.from_service_account_info(
+                credentials_content, target_audience=audience
+            )
+    except ValueError as caught_exc:
+        new_exc = exceptions.DefaultCredentialsError(
+            "Neither metadata server or valid service account credentials are found.",
+            caught_exc,
+        )
+        six.raise_from(new_exc, caught_exc)
+
+    await credentials.refresh(request)
+    return credentials.token