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Authentication |
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************** |
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.. _Overview: |
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Overview |
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======== |
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For a language agnostic overview of authentication on Google Cloud, see `Authentication Overview`_. |
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.. _Authentication Overview: https://cloud.google.com/docs/authentication |
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* **If you're running in a Google Virtual Machine Environment (Compute Engine, App Engine, Cloud Run, Cloud Functions)**, |
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authentication should "just work". |
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* **If you're developing locally**, |
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the easiest way to authenticate is using the `Google Cloud SDK`_: |
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.. code-block:: bash |
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$ gcloud auth application-default login |
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Note that this command generates credentials for client libraries. To authenticate the CLI itself, use: |
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.. code-block:: bash |
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$ gcloud auth login |
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Previously, ``gcloud auth login`` was used for both use cases. If |
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your ``gcloud`` installation does not support the new command, |
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please update it: |
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.. code-block:: bash |
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$ gcloud components update |
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.. _Google Cloud SDK: http://cloud.google.com/sdk |
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* **If you're running your application elsewhere**, |
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you should download a `service account`_ JSON keyfile |
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and point to it using an environment variable: |
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.. code-block:: bash |
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$ export GOOGLE_APPLICATION_CREDENTIALS="/path/to/keyfile.json" |
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.. _service account: https://cloud.google.com/iam/docs/creating-managing-service-accounts#creating |
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Client-Provided Authentication |
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============================== |
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Every package uses a :class:`Client <google.cloud.client.Client>` |
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as a base for interacting with an API. |
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For example: |
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.. code-block:: python |
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from google.cloud import datastore |
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client = datastore.Client() |
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Passing no arguments at all will "just work" if you've followed the |
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instructions in the :ref:`Overview`. |
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The credentials are inferred from your local environment by using |
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Google `Application Default Credentials`_. |
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.. _Application Default Credentials: https://developers.google.com/identity/protocols/application-default-credentials |
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.. _Precedence: |
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Credential Discovery Precedence |
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------------------------------- |
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When loading the `Application Default Credentials`_, |
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the library will check for credentials in your environment by following the |
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precedence outlined by :func:`google.auth.default`. |
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Explicit Credentials |
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==================== |
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The Application Default Credentials discussed above can be useful |
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if your code needs to run in many different environments or |
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if you just don't want authentication to be a focus in your code. |
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However, you may want to be explicit because |
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* your code will only run in one place |
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* you may have code which needs to be run as a specific service account |
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every time (rather than with the locally inferred credentials) |
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* you may want to use two separate accounts to simultaneously access data |
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from different projects |
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In these situations, you can create an explicit |
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:class:`~google.auth.credentials.Credentials` object suited to your environment. |
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After creation, you can pass it directly to a :class:`Client <google.cloud.client.Client>`: |
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.. code:: python |
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client = Client(credentials=credentials) |
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.. tip:: |
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To create a credentials object, follow the `google-auth-guide`_. |
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.. _google-auth-guide: https://googleapis.dev/python/google-auth/latest/user-guide.html#service-account-private-key-files |
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Google Compute Engine Environment |
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--------------------------------- |
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These credentials are used in Google Virtual Machine Environments. |
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This includes most App Engine runtimes, Compute Engine, Cloud |
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Functions, and Cloud Run. |
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To create |
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:class:`credentials <google.auth.compute_engine.Credentials>`: |
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.. code:: python |
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from google.auth import compute_engine |
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credentials = compute_engine.Credentials() |
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Service Accounts |
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---------------- |
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A `service account`_ is stored in a JSON keyfile. |
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.. code:: python |
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from google.oauth2 import service_account |
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credentials = service_account.Credentials.from_service_account_file( |
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'/path/to/key.json') |
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A JSON string or dictionary: |
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.. code:: python |
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import json |
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from google.oauth2 import service_account |
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json_account_info = json.loads(...) # convert JSON to dictionary |
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credentials = service_account.Credentials.from_service_account_info( |
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json_account_info) |
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.. tip:: |
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Previously the Google Cloud Console would issue a PKCS12/P12 key for your |
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service account. This library does not support that key format. You can |
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generate a new JSON key for the same service account from the console. |
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User Accounts (3-legged OAuth 2.0) with a refresh token |
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------------------------------------------------------- |
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The majority of cases are intended to authenticate machines or |
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workers rather than actual user accounts. However, it's also |
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possible to call Google Cloud APIs with a user account via |
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`OAuth 2.0`_. |
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.. _OAuth 2.0: https://developers.google.com/identity/protocols/OAuth2 |
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.. tip:: |
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A production application should **use a service account**, |
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but you may wish to use your own personal user account when first |
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getting started with the ``google-cloud-*`` library. |
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The simplest way to use credentials from a user account is via |
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Application Default Credentials using ``gcloud auth application-default login`` |
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(as mentioned above) and :func:`google.auth.default`: |
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.. code:: python |
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import google.auth |
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credentials, project = google.auth.default() |
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This will still follow the :ref:`precedence <Precedence>` |
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described above, |
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so be sure none of the other possible environments conflict |
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with your user provided credentials. |
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Troubleshooting |
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=============== |
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Setting up a Service Account |
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---------------------------- |
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If your application is not running on a Google Virtual Machine Environment, |
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you need a Service Account. See `Creating a Service Account`_. |
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.. _Creating a Service Account: https://cloud.google.com/iam/docs/creating-managing-service-accounts#creating |
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Using Google Compute Engine |
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--------------------------- |
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If your code is running on Google Compute Engine, |
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using the inferred Google `Application Default Credentials`_ |
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will be sufficient for retrieving credentials. |
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However, by default your credentials may not grant you |
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access to the services you intend to use. |
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Be sure when you `set up the GCE instance`_, |
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you add the correct scopes for the APIs you want to access: |
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* **All APIs** |
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* ``https://www.googleapis.com/auth/cloud-platform`` |
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* ``https://www.googleapis.com/auth/cloud-platform.read-only`` |
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For scopes for specific APIs see `OAuth 2.0 Scopes for Google APIs`_ |
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.. _set up the GCE instance: https://cloud.google.com/compute/docs/authentication#using |
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.. _OAuth 2.0 Scopes for Google APIS: https://developers.google.com/identity/protocols/oauth2/scopes |
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