How to use OAuth2 for third-party login authorization in FastAPI

How to use OAuth2 for third-party login authorization in FastAPI

Introduction:
In web applications, user login is a common function. However, in order to provide a better user experience and convenient registration/login methods, many applications choose to integrate third-party login authorization. OAuth2 is a common third-party login authorization protocol that allows users to use their existing third-party accounts to log in to applications without creating new accounts. In this article, we will introduce how to use OAuth2 in the FastAPI framework for third-party login authorization.

Step 1: Install dependent libraries

Before we start, we need to install some necessary dependent libraries. Use the following command to install them:

pip install fastapi[all]
pip install oauthlib[all]
pip install python-jose[cryptography]

Step 2: Create an OAuth2 authorization server

First, we need to create an OAuth2 authorization server. This can be achieved using the OAuth2PasswordBearer class provided by the fastapi.security library.

from fastapi import FastAPI, Depends
from fastapi.security import OAuth2PasswordBearer
from pydantic import BaseModel

app = FastAPI()

oauth2_scheme = OAuth2PasswordBearer(tokenUrl="token")

@app.get("/items/")
def read_items(token: str = Depends(oauth2_scheme)):
    return {"token": token}

In the above code, we create a FastAPI application and use the OAuth2PasswordBearer class on the /items/ route for authentication. The OAuth2PasswordBearer class requires a tokenUrl parameter that specifies the endpoint used to obtain the access token.

Step 3: Register a third-party login service provider

Before using third-party login authorization, we need to first register the application with the OAuth2 service provider used and obtain the corresponding customer Client ID and client secret. These credentials will be used in subsequent authentication processes.

Step 4: Implement the third-party login authorization process

Next, we need to write code to implement the third-party login authorization process. The following is a simple example:

from fastapi import FastAPI
from fastapi.security import OAuth2AuthorizationCodeBearer

app = FastAPI()
oauth2_scheme = OAuth2AuthorizationCodeBearer("/login/callback")

@app.get("/login")
def login():
    authorize_url = "https://oauth2.provider.com/authorize?response_type=code&client_id=CLIENT_ID&redirect_uri=http://yourapp.com/login/callback"
    return {"authorize_url": authorize_url}

@app.get("/login/callback")
def login_callback(code: str):
    # exchange code for access token
    token = "access_token"
    return {"token": token}

In the above code, we first define a /login route, which will provide a URL to the front-end user for third-party login authorization. After the user accesses this URL, he or she will be redirected to the OAuth2 provider's authorization page. On the authorization page, users will be asked to choose whether to authorize the app to access their account and receive an authorization code.

After the user is authorized, he will be redirected to the /login/callback route and the authorization code will be passed as a parameter to the route. Next, we need to use the authorization code to obtain the access token. In a real application, this process requires interaction with the OAuth2 service provider's API.

Finally, we can return the access token to the front-end user and use it for authentication on subsequent requests.

Summary:
This article introduces how to use OAuth2 in the FastAPI framework for third-party login authorization. By using the OAuth2PasswordBearer and OAuth2AuthorizationCodeBearer classes provided by the fastapi.security library, we can easily implement the authorization server and third-party login authorization flow. At the same time, we also need to register an OAuth2 service provider and obtain the corresponding client ID and client key. I hope this article can help you successfully implement the third-party login authorization function.

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