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How to build a Google sign-in in Flutter without Firebase

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Summary

This article is a step-by-step guide to implementing social authentication with GoogleOAuth2 in a Flutter Application, using Flutter AppAuth. It explains how to register the application with GoogleOAuth2, create the credentials, set up the application and URL schemes, and build the application with a loading screen, authentication screen, main screen, and authentication service. The authentication service checks for an existing refresh token, performs the authentication and refresh processes, and saves and deletes the obtained tokens. This setup can easily be changed to use different social providers.

Q&As

What are the steps to implementing social authentication with GoogleOAuth2 in a Flutter application?
The steps to implementing social authentication with GoogleOAuth2 in a Flutter application are: registering the application with GoogleOAuth2, setting up URL schemes, providing credentials to the application, and building the application.

How can users authenticate with GoogleOAuth2 in a Flutter app without Firebase?
Users can authenticate with GoogleOAuth2 in a Flutter app without Firebase by using Flutter AppAuth and connecting with the backend.

How is the authentication process with an OAuth2 provider handled on the client?
The authentication process with an OAuth2 provider is handled on the client by exchanging the received access token for an authentication token from the backend.

What is the Authorization Code Flow with Proof Key for Code Exchange (PKCE) and why is it recommended?
The Authorization Code Flow with Proof Key for Code Exchange (PKCE) is a flow that is recommended when public clients, like Single-Page and Mobile Applications, request an access token from an OAuth2 provider.

What is the redirect or callback URL format for GoogleOAuth2?
The redirect or callback URL format for GoogleOAuth2 is based on the client ids: com.googleusercontent.apps.:redirect_uri_path. For iOS, the format is com.googleusercontent.apps.:/oauthredirect and for Android, the format is com.googleusercontent.apps.:/oauthredirect.

AI Comments

👍 This article provides an in-depth and comprehensive guide on how to implement Google sign-in authentication in Flutter applications without Firebase.

👎 This article is overly long and requires a lot of technical knowledge to understand and implement the steps.

AI Discussion

Me: It's about building a Google sign-in in Flutter without Firebase. It talks about using Flutter AppAuth and connecting with your backend. It also goes over the different OAuth2 flows and how to register your application with GoogleOAuth2.

Friend: Wow, that's really cool. What are the implications of this article?

Me: Well, it means developers can now provide social authentication with GoogleOAuth2 in their Flutter applications without having to use Firebase. It also shows developers how to handle the backend side, with a Django Application for example. Additionally, the article goes over the different OAuth2 flows and provides instructions for registering an application with GoogleOAuth2. So, this article could help developers gain a better understanding of OAuth2 authentication and provide them with the tools necessary to implement it in their own applications.

Action items

Create a project in the Google Cloud Console and register your application.
Set up URL schemes for iOS and Android.
Implement the authentication service with your own backend.

Technical terms

GoogleOAuth2: Google's authentication service that allows users to sign in to applications using their Google account.
Flutter AppAuth: A Flutter package that wraps around AppAuth, providing authentication and authorization for users.
PKCE: An acronym for Proof Key for Code Exchange, a security extension to the OAuth 2.0 authorization framework.
Bundle ID/Package Name: Unique identifiers chosen by the developer for their application, used to differentiate it from other applications in the Apple App Store or Google Play Store.
SHA-1 Certificate Fingerprint: A unique signing key that differs in development and production.
CFBundleURLSchemes (iOS): A dict tag in the iOS Info.plist file used to configure the URL scheme for iOS.
appAuthRedirectScheme (Android): An entry in the Android app/build.gradle file used to adjust the URL schemes and redirect URLs.
Secure Storage: A Flutter plugin used to store data in secure storage.