最近碰到一個情境是:

  • 前端:React.js SPA
  • 後端:Django Rest Framework(DRF)
  • 使用 Google 登入,讀取特定使用者的資料

在前後端分離的狀況下,沒辦法透過 Django 內建的 session,管理使用者的登入功能。雖然有很多 DRF 相關的登入套件,但經過幾天的踩雷之後,發現有些存在著一些問題,所以就自己簡單實作了一下 Google Login。

大致的流程

  1. 前端提供按鈕,使用者按了之後,會跳出 Google 自己的登入視窗,登入之後會回傳一組 tokenID
  2. 將這組 token 傳給後端
  3. 後端做驗證此 token 正確性,建立或存取 User,產生一組 API token
  4. 將網站的 API token 回傳給前端
  5. 未來前端需要帶著 API token 才能使用 API。

Prerequirement

Integrating Google sing-in for Websites

Google API console

  1. 先向 Google 申請一個 project 並拿到 Client ID

Google API console

  1. 在 URIs 的地方新增, http://localhost:3000 此為你的前端的 URI。必須要設定這個 whitelist 才能讓網站使用 Google 登入。

Frontend

在這裡先新增一個登入的按鈕,這個按鈕按了之後會跳出 Google 登入頁面,登入成功會回傳一個組資料,其中的 tokenID 是要拿來登入後端的 token。

Integrating Google Sign-In into your web app

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$ npm install react-google-login
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import React from "react";
import GoogleLogin from "react-google-login";

export const SocialLogin = () => {
  const responseGoogle = (response) => {
    console.log(response)
    // send request to backend
  };
  return (
    <>
      <GoogleLogin
        clientId="<CLIENT_ID>.apps.googleusercontent.com"
        buttonText="使用 Google 登入"
        onSuccess={responseGoogle}
        onFailure={responseGoogle}
        cookiePolicy={"single_host_origin"}
      />
    </>
  );
};

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// tokenID jwt decode 後的東西

{
  // These six fields are included in all Google ID Tokens.
  "iss": "https://accounts.google.com",
  "sub": "110169484474386276334",
  "azp": "1008719970978-hb24n2dstb40o45d4feuo2ukqmcc6381.apps.googleusercontent.com",
  "aud": "1008719970978-hb24n2dstb40o45d4feuo2ukqmcc6381.apps.googleusercontent.com",
  "iat": "1433978353",
  "exp": "1433981953",

  // These seven fields are only included when the user has granted the "profile" and
  // "email" OAuth scopes to the application.
  "email": "[email protected]",
  "email_verified": "true",
  "name": "Test User",
  "picture": "https://lh4.googleusercontent.com/-kYgzyAWpZzJ/ABCDEFGHI/AAAJKLMNOP/tIXL9Ir44LE/s99-c/photo.jpg",
  "given_name": "Test",
  "family_name": "User",
  "locale": "en"
}

Backend

Rest Framework 的設定就不再贅述,我是用 JWT Authentication,以下這篇文章清楚的解釋如何設定 JWT。djangorestframework-simplejwt這個套件預設是用 username+password 登入,所以我們只需要修改一點 code 來建立一個接收 tokenID 的 API 給前端。

110% Complete JWT Authentication with Django & React - 2020

Authentication Django Rest Framework

Flow

Authenticate with a backend server

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$ pip install djangorestframework
$ pip install djangorestframework-simplejwt
$ pip install django-cors-headers
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# my_projects/settings.py

INSTALLED_APPS = [
    # ...
    'accounts'
    'rest_framework',
    'corsheaders',
]

SOCIAL_GOOGLE_CLIENT_ID = '<CLIENT_ID>.apps.googleusercontent.com'

# Rest framework settings
REST_FRAMEWORK = {
    'DEFAULT_PERMISSION_CLASSES': [
        'rest_framework.permissions.IsAuthenticated',
    ],
    'DEFAULT_AUTHENTICATION_CLASSES': ('rest_framework_simplejwt.authentication.JWTAuthentication',)
}

# CORS header
CORS_ORIGIN_WHITELIST = [
    "http://localhost:3000",
]

建立 SocialAcoount 的 model 主要是用來建立 Google id -> User 之間的連結。

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# accounts/models.py

from django.db import models
from django.contrib.auth.models import User

class SocialAccount(models.Model):
    provider = models.CharField(max_length=200, default='google') # 若未來新增其他的登入方式,如Facebook,GitHub...
    unique_id = models.CharField(max_length=200)
    user = models.ForeignKey(
        User, related_name='social', on_delete=models.CASCADE)

Serializer 在建立使用者的時候驗證傳入的 tokenID 是否正確。如果使用者不存在,就建立一個使用者。在這個情境中,我的網站只有要讓使用者以 Google 登入,所以 Username 可以自己隨便設,但必須是唯一的,未來用 first_name+last_name 來顯示全名就好。

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# accounts/serializers.py

from django.contrib.auth.models import User
from rest_framework import serializers
from google.oauth2 import id_token
from google.auth.transport import requests

from api.settings import SOCIAL_GOOGLE_CLIENT_ID
from accounts.models import SocialAccount

class SocialLoginSerializer(serializers.Serializer):
    token = serializers.CharField(required=True)

    def verify_token(self, token):
        """
        驗證 id_token 是否正確

        token: JWT
        """
        try:
            idinfo = id_token.verify_oauth2_token(
                token, requests.Request(), SOCIAL_GOOGLE_CLIENT_ID)
            if idinfo['iss'] not in ['accounts.google.com', 'https://accounts.google.com']:
                raise ValueError('Wrong issuer.')
            if idinfo['aud'] not in [SOCIAL_GOOGLE_CLIENT_ID]:
                raise ValueError('Could not verify audience.')
            # Success
            return idinfo
        except ValueError:
            pass

    def create(self, validated_data):
        idinfo = self.verify_token(validated_data.get('token'))
        if idinfo:
            # User not exists
            if not SocialAccount.objects.filter(unique_id=idinfo['sub']).exists():
                user = User.objects.create_user(
                    username=f"{idinfo['name']} {idinfo['email']}", # Username has to be unique
                    first_name=idinfo['given_name'],
                    last_name=idinfo['family_name'],
                    email=idinfo['email']
                )
                SocialAccount.objects.create(
                    user=user,
                    unique_id=idinfo['sub']
                )
                return user
            else:
                social = SocialAccount.objects.get(unique_id=idinfo['sub'])
                return social.user
        else:
            raise ValueError("Incorrect Credentials")

class UserSerializer(serializers.ModelSerializer):
    class Meta:
        model = User
        fields = ['username', 'email', 'first_name', 'last_name']

get_tokens_for_user() 將產生一個對應該 User 的 JWT 。

  • access_token: 時效短,每次前端 request 時必須加在 Header 中,不然會得到 401 unauthorized Error.
  • refresh_token: 時效長,當 access_token 過期後,拿著這個 token 來交換新的 access_token
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# accounts/views.py

from rest_framework.permissions import AllowAny
from rest_framework.response import Response
from rest_framework_simplejwt.tokens import RefreshToken
from rest_framework_simplejwt.views import TokenObtainPairView

from accounts.serializers import SocialLoginSerializer

def get_tokens_for_user(user):
    refresh = RefreshToken.for_user(user)
    return {
        'refresh': str(refresh),
        'access': str(refresh.access_token),
    }

class GoogleLogin(TokenObtainPairView):
    permission_classes = (AllowAny, ) # AllowAny for login
    serializer_class = SocialLoginSerializer

    def post(self, request):
        serializer = self.get_serializer(data=request.data)
        if serializer.is_valid(raise_exception=True):
            user = serializer.save()
            return Response(get_tokens_for_user(user))
        else:
            raise ValueError('Not serializable')
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# accounts/urls.py

from django.urls import path
from rest_framework_simplejwt import views as jwt_views
from accounts.views import GoogleLogin

urlpatterns = [
    path('token/obtain/', GoogleLogin.as_view()),
    path('token/refresh/', jwt_views.TokenRefreshView.as_view(), name='token_refresh'),
]
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# my_projects/urls.py

from django.urls import path, include

urlpatterns = [
    # ...
    path('accounts/', include('accounts.urls')),
]

前後端串起來

前端的按鈕和後端的 API 都準備好之後,就照著一開始的 flow 把他串起來。

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// ...
import axios from "axios";

export const SocialLogin = () => {
  const responseGoogle = (response) => {
    console.log(response);
    // Send request to backend
    axios
      .post("http://localhost:8000/accounts/token/obtain/", {
        token: id_token,
      })
      .then((res) => {
        console.log(res.data);
        // 拿到的 token 存在 localStorage
        localStorage.setItem("access_token", res.data.access);
        localStorage.setItem("refresh_token", res.data.refresh);
      })
      .catch((err) => {
        console.log(err);
      });
  };
  return (
    <>
      <GoogleLogin
        clientId="<CLIENT_ID>.apps.googleusercontent.com"
        buttonText="使用 Google 登入"
        onSuccess={responseGoogle}
        onFailure={responseGoogle}
        cookiePolicy={"single_host_origin"}
      />
    </>
  );
};

當未來要存取 API 資料時,header 要加上 Authorization:Bearer <access_token>。底下的程式碼是當此次 Request 中的 Access token 過期之後,自動拿 refresh_token 去換新的 access_token。

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import axios from "axios";

const axiosAPI = axios.create({
  baseURL: "http://localhost:8000",
  headers: {
    Authorization: "Bearer " + localStorage.getItem("access_token"), // 帶著 access token
    "Content-Type": "application/json",
    accept: "application/json",
  },
});

axiosAPI.interceptors.response.use(
  (response) => response,
  (error) => {
    const originalRequest = error.config;
    if (error.response.status === 401 && error.response.statusText === "Unauthorized") {
      // access token -> 向 API 拿新的 token
      const refresh_token = localStorage.getItem("refresh_token");
      return axios
        .post("http://localhost:8000/accounts/token/refresh/", { refresh: refresh_token })
        .then((response) => {
          localStorage.setItem("access_token", response.data.access);
          axiosAPI.defaults.headers["Authorization"] = "Bearer " + response.data.access;
          originalRequest.headers["Authorization"] = "Bearer " + response.data.access;
          return axiosAPI(originalRequest);
        })
        .catch((err) => {
          // refresh token 過期 -> 直接當作完全沒有登入
          localStorage.removeItem("refresh_token");
          window.location.href = "/login";
        });
    }
    return Promise.reject(error);
  }
);

export default axiosAPI;
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import axiosAPI from "./axiosApi";

export const fetchData = (dispatch) => {
  const token = localStorage.getItem("access_token");
  axiosAPI.get("/todos/").then((res) => {
    console.log(res.data);
  });
};

Note:

這不是一個 Step-by-step 的教學,我省略了一些基礎,如:virtualenv 設定, migrate, runserver… 等等有基礎知識的人都會理解的步驟。

參考&額外資料