6.9 KiB
OAuth2
FastAPI Users provides an optional OAuth2 authentication support. It relies on HTTPX OAuth library, which is a pure-async implementation of OAuth2.
Installation
You should install the library with the optional dependencies for OAuth:
pip install 'fastapi-users[sqlalchemy,oauth]'
pip install 'fastapi-users[beanie,oauth]'
Configuration
Instantiate an OAuth2 client
You first need to get an HTTPX OAuth client instance. Read the documentation for more information.
from httpx_oauth.clients.google import GoogleOAuth2
google_oauth_client = GoogleOAuth2("CLIENT_ID", "CLIENT_SECRET")
Setup the database adapter
SQLAlchemy
You'll need to define the SQLAlchemy model for storing OAuth accounts. We provide a base one for this:
--8<-- "docs/src/db_sqlalchemy_oauth.py"
Notice that we also manually added a relationship on User so that SQLAlchemy can properly retrieve the OAuth accounts of the user.
Besides, when instantiating the database adapter, we need pass this SQLAlchemy model as third argument.
!!! tip "Primary key is defined as UUID"
By default, we use UUID as a primary key ID for your user. If you want to use another type, like an auto-incremented integer, you can use SQLAlchemyBaseOAuthAccountTable as base class and define your own id and user_id column.
```py
class OAuthAccount(SQLAlchemyBaseOAuthAccountTable[int], Base):
id: Mapped[int] = mapped_column(Integer, primary_key=True)
@declared_attr
def user_id(cls) -> Mapped[int]:
return mapped_column(Integer, ForeignKey("user.id", ondelete="cascade"), nullable=False)
```
Notice that `SQLAlchemyBaseOAuthAccountTable` expects a generic type to define the actual type of ID you use.
Beanie
The advantage of MongoDB is that you can easily embed sub-objects in a single document. That's why the configuration for Beanie is quite simple. All we need to do is to define another class to structure an OAuth account object.
--8<-- "docs/src/db_beanie_oauth.py"
It's worth to note that OAuthAccount is not a Beanie document but a Pydantic model that we'll embed inside the User document, through the oauth_accounts array.
Generate routers
Once you have a FastAPIUsers instance, you can make it generate a single OAuth router for a given client and authentication backend.
app.include_router(
fastapi_users.get_oauth_router(google_oauth_client, auth_backend, "SECRET"),
prefix="/auth/google",
tags=["auth"],
)
!!! tip If you have several OAuth clients and/or several authentication backends, you'll need to create a router for each pair you want to support.
Existing account association
If a user with the same e-mail address already exists, an HTTP 400 error will be raised by default.
You can however choose to automatically link this OAuth account to the existing user account by setting the associate_by_email flag:
app.include_router(
fastapi_users.get_oauth_router(
google_oauth_client,
auth_backend,
"SECRET",
associate_by_email=True,
),
prefix="/auth/google",
tags=["auth"],
)
Bear in mind though that it can lead to security breaches if the OAuth provider does not validate e-mail addresses. How?
- Let's say your app support an OAuth provider, Merlinbook, which does not validate e-mail addresses.
- Imagine a user registers to your app with the e-mail address
lancelot@camelot.bt. - Now, a malicious user creates an account on Merlinbook with the same e-mail address. Without e-mail validation, the malicious user can use this account without limitation.
- The malicious user authenticates using Merlinbook OAuth on your app, which automatically associates to the existing
lancelot@camelot.bt. - Now, the malicious user has full access to the user account on your app 😞
Association router for authenticated users
We also provide a router to associate an already authenticated user with an OAuth account. After this association, the user will be able to authenticate with this OAuth provider.
app.include_router(
fastapi_users.get_oauth_associate_router(google_oauth_client, UserRead, "SECRET"),
prefix="/auth/associate/google",
tags=["auth"],
)
Notice that, just like for the Users router, you have to pass the UserRead Pydantic schema.
Set is_verified to True by default
!!! tip "This section is only useful if you set up email verification" You can read more about this feature here.
When a new user registers with an OAuth provider, the is_verified flag is set to False, which requires the user to verify its email address.
You can choose to trust the email address given by the OAuth provider and set the is_verified flag to True after registration. You can do this by setting the is_verified_by_default argument:
app.include_router(
fastapi_users.get_oauth_router(
google_oauth_client,
auth_backend,
"SECRET",
is_verified_by_default=True,
),
prefix="/auth/google",
tags=["auth"],
)
!!! danger "Make sure you can trust the OAuth provider" Make sure the OAuth provider you're using does verify the email address before enabling this flag.
Full example
!!! warning Notice that SECRET should be changed to a strong passphrase. Insecure passwords may give attackers full access to your database.
SQLAlchemy
=== "requirements.txt"
```
--8<-- "examples/sqlalchemy-oauth/requirements.txt"
```
=== "main.py"
```py
--8<-- "examples/sqlalchemy-oauth/main.py"
```
=== "app/app.py"
```py
--8<-- "examples/sqlalchemy-oauth/app/app.py"
```
=== "app/db.py"
```py
--8<-- "examples/sqlalchemy-oauth/app/db.py"
```
=== "app/schemas.py"
```py
--8<-- "examples/sqlalchemy-oauth/app/schemas.py"
```
=== "app/users.py"
```py
--8<-- "examples/sqlalchemy-oauth/app/users.py"
```
Beanie
=== "requirements.txt"
```
--8<-- "examples/beanie-oauth/requirements.txt"
```
=== "main.py"
```py
--8<-- "examples/beanie-oauth/main.py"
```
=== "app/app.py"
```py
--8<-- "examples/beanie-oauth/app/app.py"
```
=== "app/db.py"
```py
--8<-- "examples/beanie-oauth/app/db.py"
```
=== "app/schemas.py"
```py
--8<-- "examples/beanie-oauth/app/schemas.py"
```
=== "app/users.py"
```py
--8<-- "examples/beanie-oauth/app/users.py"
```