feat: add api key support

google/auth/_default.py

@@ -353,6 +353,17 @@ def _get_external_account_credentials(
     return credentials, credentials.get_project_id(request=request)
 
 
+def _get_api_key_credentials(quota_project_id=None):
+    """Gets API key credentials and project ID."""
+    from google.auth import api_key
+
+    api_key_value = os.environ.get(environment_vars.API_KEY)
+    if api_key_value:
+        return api_key.Credentials(api_key_value), quota_project_id
+    else:
+        return None, None
+
+
 def default(scopes=None, request=None, quota_project_id=None, default_scopes=None):
     """Gets the default credentials for the current environment.
 
@@ -361,7 +372,14 @@ def default(scopes=None, request=None, quota_project_id=None, default_scopes=Non
     This function acquires credentials from the environment in the following
     order:
 
-    1. If the environment variable ``GOOGLE_APPLICATION_CREDENTIALS`` is set
+    1. If both ``GOOGLE_API_KEY`` and ``GOOGLE_APPLICATION_CREDENTIALS``
+       environment variables are set, throw an exception.
+
+       If ``GOOGLE_API_KEY`` is set, an `API Key`_ credentials will be returned.
+       The project ID returned is the one defined by ``GOOGLE_CLOUD_PROJECT`` or
+       ``GCLOUD_PROJECT`` environment variables.
+
+       If the environment variable ``GOOGLE_APPLICATION_CREDENTIALS`` is set
        to the path of a valid service account JSON private key file, then it is
        loaded and returned. The project ID returned is the project ID defined
        in the service account file if available (some older files do not
@@ -409,6 +427,7 @@ def default(scopes=None, request=None, quota_project_id=None, default_scopes=Non
     .. _Metadata Service: https://cloud.google.com/compute/docs\
             /storing-retrieving-metadata
     .. _Cloud Run: https://cloud.google.com/run
+    .. _API Key: https://cloud.google.com/docs/authentication/api-keys
 
     Example::
 
@@ -444,16 +463,25 @@ def default(scopes=None, request=None, quota_project_id=None, default_scopes=Non
             invalid.
     """
     from google.auth.credentials import with_scopes_if_required
+    from google.auth.credentials import CredentialsWithQuotaProject
 
     explicit_project_id = os.environ.get(
         environment_vars.PROJECT, os.environ.get(environment_vars.LEGACY_PROJECT)
     )
 
+    if os.environ.get(environment_vars.API_KEY) and os.environ.get(
+        environment_vars.CREDENTIALS
+    ):
+        raise exceptions.DefaultCredentialsError(
+            "GOOGLE_API_KEY and GOOGLE_APPLICATION_CREDENTIALS are mutually exclusive"
+        )
+
     checkers = (
         # Avoid passing scopes here to prevent passing scopes to user credentials.
         # with_scopes_if_required() below will ensure scopes/default scopes are
         # safely set on the returned credentials since requires_scopes will
         # guard against setting scopes on user credentials.
+        lambda: _get_api_key_credentials(quota_project_id=quota_project_id),
         lambda: _get_explicit_environ_credentials(quota_project_id=quota_project_id),
         lambda: _get_gcloud_sdk_credentials(quota_project_id=quota_project_id),
         _get_gae_credentials,
@@ -477,7 +505,9 @@ def default(scopes=None, request=None, quota_project_id=None, default_scopes=Non
                     request = google.auth.transport.requests.Request()
                 project_id = credentials.get_project_id(request=request)
 
-            if quota_project_id:
+            if quota_project_id and isinstance(
+                credentials, CredentialsWithQuotaProject
+            ):
                 credentials = credentials.with_quota_project(quota_project_id)
 
             effective_project_id = explicit_project_id or project_id

google/auth/_default_async.py

@@ -161,6 +161,17 @@ def _get_gae_credentials():
     return _default._get_gae_credentials()
 
 
+def _get_api_key_credentials(quota_project_id=None):
+    """Gets API key credentials and project ID."""
+    from google.auth import api_key
+
+    api_key_value = os.environ.get(environment_vars.API_KEY)
+    if api_key_value:
+        return api_key.Credentials(api_key_value), quota_project_id
+    else:
+        return None, None
+
+
 def _get_gce_credentials(request=None):
     """Gets credentials and project ID from the GCE Metadata Service."""
     # Ping requires a transport, but we want application default credentials
@@ -182,7 +193,14 @@ def default_async(scopes=None, request=None, quota_project_id=None):
     This function acquires credentials from the environment in the following
     order:
 
-    1. If the environment variable ``GOOGLE_APPLICATION_CREDENTIALS`` is set
+    1. If both ``GOOGLE_API_KEY`` and ``GOOGLE_APPLICATION_CREDENTIALS``
+       environment variables are set, throw an exception.
+
+       If ``GOOGLE_API_KEY`` is set, an `API Key`_ credentials will be returned.
+       The project ID returned is the one defined by ``GOOGLE_CLOUD_PROJECT`` or
+       ``GCLOUD_PROJECT`` environment variables.
+
+       If the environment variable ``GOOGLE_APPLICATION_CREDENTIALS`` is set
        to the path of a valid service account JSON private key file, then it is
        loaded and returned. The project ID returned is the project ID defined
        in the service account file if available (some older files do not
@@ -221,6 +239,7 @@ def default_async(scopes=None, request=None, quota_project_id=None):
     .. _Metadata Service: https://cloud.google.com/compute/docs\
             /storing-retrieving-metadata
     .. _Cloud Run: https://cloud.google.com/run
+    .. _API Key: https://cloud.google.com/docs/authentication/api-keys
 
     Example::
 
@@ -250,12 +269,21 @@ def default_async(scopes=None, request=None, quota_project_id=None):
             invalid.
     """
     from google.auth._credentials_async import with_scopes_if_required
+    from google.auth.credentials import CredentialsWithQuotaProject
 
     explicit_project_id = os.environ.get(
         environment_vars.PROJECT, os.environ.get(environment_vars.LEGACY_PROJECT)
     )
 
+    if os.environ.get(environment_vars.API_KEY) and os.environ.get(
+        environment_vars.CREDENTIALS
+    ):
+        raise exceptions.DefaultCredentialsError(
+            "GOOGLE_API_KEY and GOOGLE_APPLICATION_CREDENTIALS are mutually exclusive"
+        )
+
     checkers = (
+        lambda: _get_api_key_credentials(quota_project_id=quota_project_id),
         lambda: _get_explicit_environ_credentials(quota_project_id=quota_project_id),
         lambda: _get_gcloud_sdk_credentials(quota_project_id=quota_project_id),
         _get_gae_credentials,
@@ -265,9 +293,11 @@ def default_async(scopes=None, request=None, quota_project_id=None):
     for checker in checkers:
         credentials, project_id = checker()
         if credentials is not None:
-            credentials = with_scopes_if_required(
-                credentials, scopes
-            ).with_quota_project(quota_project_id)
+            credentials = with_scopes_if_required(credentials, scopes)
+            if quota_project_id and isinstance(
+                credentials, CredentialsWithQuotaProject
+            ):
+                credentials = credentials.with_quota_project(quota_project_id)
             effective_project_id = explicit_project_id or project_id
             if not effective_project_id:
                 _default._LOGGER.warning(

google/auth/api_key.py

@@ -0,0 +1,85 @@
+# Copyright 2021 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 API key support.
+
+This module provides authentication using the `API key`_.
+
+
+.. _API key:
+    https://cloud.google.com/docs/authentication/api-keys/
+"""
+
+from google.auth import _helpers
+from google.auth import credentials
+
+
+class Credentials(credentials.Credentials):
+    """API key credentials.
+
+    These credentials use API key to provide authorization to applications.
+    """
+
+    def __init__(self, token):
+        """
+        Args:
+            token (str): API key string
+
+        Raises:
+            ValueError: If the provided API key is not a non-empty string.
+        """
+        if not token:
+            raise ValueError("Token must be a non-empty API key string")
+        super(Credentials, self).__init__()
+        self.token = token
+
+    @property
+    @_helpers.copy_docstring(credentials.Credentials)
+    def expired(self):
+        return False
+
+    @property
+    @_helpers.copy_docstring(credentials.Credentials)
+    def valid(self):
+        return True
+
+    @_helpers.copy_docstring(credentials.Credentials)
+    def refresh(self, request):
+        return
+
+    def apply(self, headers, token=None):
+        """Apply the API key token to the x-goog-api-key header.
+
+        Args:
+            headers (Mapping): The HTTP request headers.
+            token (Optional[str]): If specified, overrides the current access
+                token.
+        """
+        headers["x-goog-api-key"] = token or self.token
+
+    def before_request(self, request, method, url, headers):
+        """Performs credential-specific before request logic.
+
+        Refreshes the credentials if necessary, then calls :meth:`apply` to
+        apply the token to the x-goog-api-key header.
+
+        Args:
+            request (google.auth.transport.Request): The object used to make
+                HTTP requests.
+            method (str): The request's HTTP method or the RPC method being
+                invoked.
+            url (str): The request's URI or the RPC service's URI.
+            headers (Mapping): The request's headers.
+        """
+        self.apply(headers)

google/auth/environment_vars.py

@@ -33,6 +33,9 @@
 """Environment variable defining the location of Google application default
 credentials."""
 
+API_KEY = "GOOGLE_API_KEY"
+"""Environment variable defining the API key value."""
+
 # The environment variable name which can replace ~/.config if set.
 CLOUD_SDK_CONFIG_DIR = "CLOUDSDK_CONFIG"
 """Environment variable defines the location of Google Cloud SDK's config

tests/test__default.py

@@ -19,6 +19,7 @@
 import pytest  # type: ignore
 
 from google.auth import _default
+from google.auth import api_key
 from google.auth import app_engine
 from google.auth import aws
 from google.auth import compute_engine
@@ -994,3 +995,40 @@ def test_default_no_warning_with_quota_project_id_for_user_creds(get_adc_path):
     get_adc_path.return_value = AUTHORIZED_USER_CLOUD_SDK_FILE
 
     credentials, project_id = _default.default(quota_project_id="project-foo")
+
+
+def test__get_api_key_credentials_no_env_var():
+    cred, project_id = _default._get_api_key_credentials(quota_project_id="project-foo")
+    assert cred is None
+    assert project_id is None
+
+
+def test__get_api_key_credentials_from_env_var():
+    with mock.patch.dict(os.environ, {environment_vars.API_KEY: "api-key"}):
+        cred, project_id = _default._get_api_key_credentials(
+            quota_project_id="project-foo"
+        )
+        assert isinstance(cred, api_key.Credentials)
+        assert cred.token == "api-key"
+        assert project_id == "project-foo"
+
+
+def test_exception_with_api_key_and_adc_env_var():
+    with mock.patch.dict(os.environ, {environment_vars.API_KEY: "api-key"}):
+        with mock.patch.dict(
+            os.environ, {environment_vars.CREDENTIALS: "/path/to/json"}
+        ):
+            with pytest.raises(exceptions.DefaultCredentialsError) as excinfo:
+                _default.default()
+
+            assert excinfo.match(
+                r"GOOGLE_API_KEY and GOOGLE_APPLICATION_CREDENTIALS are mutually exclusive"
+            )
+
+
+def test_default_api_key_from_env_var():
+    with mock.patch.dict(os.environ, {environment_vars.API_KEY: "api-key"}):
+        cred, project_id = _default.default()
+        assert isinstance(cred, api_key.Credentials)
+        assert cred.token == "api-key"
+        assert project_id is None

tests/test_api_key.py

@@ -0,0 +1,45 @@
+# Copyright 2021 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.
+
+import pytest
+
+from google.auth import api_key
+
+
+def test_credentials_constructor():
+    with pytest.raises(ValueError) as excinfo:
+        api_key.Credentials("")
+
+    assert excinfo.match(r"Token must be a non-empty API key string")
+
+
+def test_expired_and_valid():
+    credentials = api_key.Credentials("api-key")
+
+    assert credentials.valid
+    assert credentials.token == "api-key"
+    assert not credentials.expired
+
+    credentials.refresh(None)
+    assert credentials.valid
+    assert credentials.token == "api-key"
+    assert not credentials.expired
+
+
+def test_before_request():
+    credentials = api_key.Credentials("api-key")
+    headers = {}
+
+    credentials.before_request(None, "http://example.com", "GET", headers)
+    assert headers["x-goog-api-key"] == "api-key"

tests_async/test__default_async.py

@@ -20,6 +20,7 @@
 
 from google.auth import _credentials_async as credentials
 from google.auth import _default_async as _default
+from google.auth import api_key
 from google.auth import app_engine
 from google.auth import compute_engine
 from google.auth import environment_vars
@@ -561,3 +562,40 @@ def test_default_no_warning_with_quota_project_id_for_user_creds(get_adc_path):
     get_adc_path.return_value = test_default.AUTHORIZED_USER_CLOUD_SDK_FILE
 
     credentials, project_id = _default.default_async(quota_project_id="project-foo")
+
+
+def test__get_api_key_credentials_no_env_var():
+    cred, project_id = _default._get_api_key_credentials(quota_project_id="project-foo")
+    assert cred is None
+    assert project_id is None
+
+
+def test__get_api_key_credentials_from_env_var():
+    with mock.patch.dict(os.environ, {environment_vars.API_KEY: "api-key"}):
+        cred, project_id = _default._get_api_key_credentials(
+            quota_project_id="project-foo"
+        )
+        assert isinstance(cred, api_key.Credentials)
+        assert cred.token == "api-key"
+        assert project_id == "project-foo"
+
+
+def test_exception_with_api_key_and_adc_env_var():
+    with mock.patch.dict(os.environ, {environment_vars.API_KEY: "api-key"}):
+        with mock.patch.dict(
+            os.environ, {environment_vars.CREDENTIALS: "/path/to/json"}
+        ):
+            with pytest.raises(exceptions.DefaultCredentialsError) as excinfo:
+                _default.default_async()
+
+            assert excinfo.match(
+                r"GOOGLE_API_KEY and GOOGLE_APPLICATION_CREDENTIALS are mutually exclusive"
+            )
+
+
+def test_default_api_key_from_env_var():
+    with mock.patch.dict(os.environ, {environment_vars.API_KEY: "api-key"}):
+        cred, project_id = _default.default_async()
+        assert isinstance(cred, api_key.Credentials)
+        assert cred.token == "api-key"
+        assert project_id is None