Firebase Auth for GTM Session Fetcher with Google APIs Client Library for Objective-C for REST

[Madeline Folkerts]

Hi, I am using Google APIs Client Library for Objective-C for REST, which uses GTM Session Fetcher for authentication.

I wanted to switch from Google Sign In to a Firebase Authentication method (Phone Number Auth or Email/password Auth) for access to a private Google API.

Is it possible to implement GTMFetcherAuthorizationProtocol using a Firebase ID Token as the access token? The API I am using can be authorized by a Firebase ID Token, but I'm getting this error:

Request had invalid authentication credentials. Expected OAuth 2 access token, login cookie or other valid authentication credential. See https://developers.google.com/identity/sign-in/web/devconsole-project.

Thanks in advance!

[Thomas Van Lenten]

You'll likely need to ask on a Firebase support site, I'm not sure exactly what they provide, one would hope they already have something that implements the protocol.

TVL

[Madeline Folkerts]

Ok thanks, I actually got it working. The error ended up being specific to the API I'm using. If anyone is curious, a combination of the code here and here should work using the user's Firebase ID Token as the access token.