Access Firebase Custom Token claims from the Web SDK

Question

If I have a custom token with certain claims and I sign in to Firebase using it, is there any way to access those claims from inside app, using the Web SDK?

For example, if my custom token is like this

{
 :iss => $service_account_email,
 :sub => $service_account_email,
 :aud => "https://identitytoolkit.googleapis.com/google.identity.identitytoolkit.v1.IdentityToolkit",
 :iat => now_seconds,
 :exp => now_seconds+(60*60), # Maximum expiration time is one hour
 :uid => uid,
 :claims => {:premium_account => is_premium_account}
}

I would like to know if there is something like (from inside the app):

firebase.auth.token.claims.premium_account

I'm not finding anything like this in the docs.

http://stackoverflow.com/questions/39917020/where-to-find-auth-token-data-inside-firebase-objects — bojeil, Apr 11 '17 at 04:02
Thanks @bojeil. So It looks like it's not accesible from the sdk... — Bruno, Apr 11 '17 at 14:00

score 5 · Answer 1 · edited Aug 06 '18 at 13:21

5

It looks like you want getIdTokenResult:

await firebase.auth().currentUser.getIdTokenResult()

edited Aug 06 '18 at 13:21

Paul Roub

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answered Aug 06 '18 at 13:17

Brian M. Hunt

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score 1 · Answer 2 · answered Apr 28 '17 at 06:18

claims is embedded in the token.

Here is an example code to extract the claims from the token using jwt-decode on a web client:

import jwt_decode from './jwt-decode';

firebase.auth().currentUser.getToken().then((token) => {
    console.log(token);
    console.log(jwt_decode(token));
});

score 0 · Answer 3 · answered Jan 05 '18 at 22:11

Here is the documentation on it: https://firebase.google.com/docs/auth/admin/custom-claims

I think the gist of it, is once you have custom claims appended to a user via backend code (admin sdk OR firebase functions), you can base64 decode the currentUser token. The documentation references a mozilla article on javascript base64 decoding: https://developer.mozilla.org/en-US/docs/Web/API/WindowBase64/Base64_encoding_and_decoding

You can JSON.parse the decoded token and your custom claims will show up there. The documentation is pretty good about it.

Access Firebase Custom Token claims from the Web SDK

3 Answers3