asp.net mvc - Firebase 3: creating a custom authentication token using .net and c#

Question

I'm trying to implement Firebase 3 Authentication mechanism using Custom Tokens (as described at https:// firebase.google.com/docs/auth/server/create-custom-tokens).

My server is ASP.NET MVC Application.

So according to the instructions (https://firebase.google.com/docs/server/setup) I've created a service account for my Firebase application and generated a key in '.p12' format.

After that according to instructions here (https://firebase.google.com/docs/auth/server/create-custom-tokens#create_custom_tokens_using_a_third-party_jwt_library) I tried to generate a custom token and sign it using the key received on the previous step. For token generation I used SystemIdentityModel.Tokens.Jwt library from Microsoft, so the code looks like the following:

var now = DateTime.UtcNow;
var tokenHandler = new JwtSecurityTokenHandler();
var key = new X509AsymmetricSecurityKey(new X509Certificate2(p12path, p12pwd));
var signinCredentials = new SigningCredentials(key, "http://www.w3.org/2001/04/xmldsig-more#rsa-sha256", "http://www.w3.org/2001/04/xmlenc#rsa-sha256");
Int32 nowInUnixTimestamp = (Int32)(now.Subtract(new DateTime(1970, 1, 1))).TotalSeconds;

var token = tokenHandler.CreateToken(
            issuer: serviceAccountEmail,
            audience: "https://identitytoolkit.googleapis.com/google.identity.identitytoolkit.v1.IdentityToolkit",                
            signingCredentials: signinCredentials,
            subject: new ClaimsIdentity(new Claim[]
                    {
                    new Claim("sub", serviceAccountEmail),
                    new Claim("iat", nowInUnixTimestamp.ToString()),
                    new Claim("exp", (nowInUnixTimestamp + (60*60)).ToString()),
                    new Claim("uid", uid)
                    })
            );

var tokenString = tokenHandler.WriteToken(token);

Then tried to sign in user in React Native application using Firebase Javascript SDK, with the following code:

//omitting initialization code
firebase.auth().signInWithCustomToken(firebaseJWT).catch(function(error) {
            console.log('Error authenticating Firebase user. Code: ' + error.code + ' Message: ' + error.message);            
        });

But got an error from Firebase saying:

Error authenticating Firebase user. Code: auth/invalid-custom-token Message: The custom token format is incorrect. Please check the documentation.

Experimenting with adding different claims for token expiration control didn't help either.

Also I tried to generate tokens with "dvsekhvalnov/jose-jwt" library but can't get it working with "RS256" algorithm.

So the question:

Any suggestion on what am I doing wrong?

Answer 1

Waitting for answers