flutter google_sign_in get id token without firebase

Question

I looked at a lot of post related to this topic but none were able to solve my problem so here it is: I use google_sign_in to be able to authenticate with a gmail account all without going through firebase. Everything is going well and I retrieve the user information well but the concern is that the value of my idToken is null whatever my manipulation. However, I did register my app via the google console and here is my code:

final GoogleSignInAccount user = await googleSignIn.signIn();
  GoogleSignInAuthentication googleSignInAuthentication = await user.authentication;
  print('======== Google auth ===========');
  print(googleSignInAuthentication.accessToken);
  print(googleSignInAuthentication.idToken);
  print('===================');

And here is what it returns to me:

I get the access token well but the token id is null and I would like to know:

• Is it possible to retrieve the idToken without going through firebase when you have a custom API?
• If not, in which part is the method entered to be able to retrieve this token?

Solution

Yes You can.

I had this working long time back with PHP that would take care of the google-auth token validation.

This is with respect to google_sign_in: ^4.4.2

The Github Sample Project

1. Create a GCP project at https://console.cloud.google.com/projectcreate

2. Next go to https://developers.google.com/identity/sign-in/web/sign-in and select Configure Project, client as Android. Enter Package name and SHA1

Generating SHA1 signing certificates.

1. Execute in terminal (assign a password and some other parameters)

   keytool -genkey -v -keystore ~/key.jks -keyalg RSA -keysize 2048 -validity 10000 -alias androiddebugkey

2. From the above step you will have a key.jks file for you.

3. In android/app/build.gradle under android add these settings:

   signingConfigs {
       debug {
           storeFile file('key.jks') 
           storePassword 'epynic'
           keyAlias 'androiddebugkey'
           keyPassword 'epynic'
       }
   }
   buildTypes {
       debug {
           signingConfig signingConfigs.debug
       }
   }
   

   storeFile file('/home/epynic/key.jks') - path to your key file generated in step 2

   storePassword 'epynic' & keyPassword 'epynic' the password used to generate the key in step 2.

4. In termial execute keytool -keystore key.jks -list -v and in the output you’ll have the SHA-1 fingerprint.

5. Find your package name at AndroidManifest.xml file, under the package= attribute.

Comments

[Sano]

Sorry for the response time, I have already performed these steps but unfortunately it still results in a null idtoken.

[dustinnoyes]

Still getting null for idtoken as well.