Authenticating a service account for Firebase Realtime Database in Go - go

Question

I'm trying to use the new Firebase Realtime Database for a simple logging application. All interraction with the database will be from my server, so I only need one account that can read/write anything.
As far as I can tell (the documentation is awful - there's plenty of it but it contradicts itself and half of it is for the 'old' Firebase, and often it is in some random language that you aren't using), I need to create a service account and then create a JWT token using OAuth. Fortunately Go has some nice built in libraries for this. Here is my code:
const firebasePostUrl = "https://my-product-logging.firebaseio.com/tests.json"
// Obtained from the Google Cloud API Console
var firebaseServiceAccount map[string]string = map[string]string{
"type": "service_account",
"project_id": "my-product-logging",
"private_key_id": "1c35ac0c501617b8f1610113c492a5d3321f4318",
"private_key": "-----BEGIN PRIVATE KEY-----\nMIIEvQIBADANBgkqhkiG9w0BAQEFAASCBKcwggSjAgEAAoblahblahhwWlteuRDrsxmRq+8\ncDGMKcXyDHl3nWdIrWqJcDw=\n-----END PRIVATE KEY-----\n",
"client_email": "log-user#my-product-logging.iam.gserviceaccount.com",
"client_id": "101403085113430683797",
"auth_uri": "https://accounts.google.com/o/oauth2/auth",
"token_uri": "https://accounts.google.com/o/oauth2/token",
"auth_provider_x509_cert_url": "https://www.googleapis.com/oauth2/v1/certs",
"client_x509_cert_url": "https://www.googleapis.com/robot/v1/metadata/x509/log-user%40my-product-logging.iam.gserviceaccount.com",
}
func firebaseClient() *http.Client {
jwtConfig := jwt.Config{
// Email is the OAuth client identifier used when communicating with
// the configured OAuth provider.
Email: firebaseServiceAccount["client_email"],
// PrivateKey contains the contents of an RSA private key or the
// contents of a PEM file that contains a private key. The provided
// private key is used to sign JWT payloads.
// PEM containers with a passphrase are not supported.
// Use the following command to convert a PKCS 12 file into a PEM.
//
// $ openssl pkcs12 -in key.p12 -out key.pem -nodes
//
PrivateKey: []byte(firebaseServiceAccount["private_key"]),
// PrivateKeyID contains an optional hint indicating which key is being
// used.
PrivateKeyID: firebaseServiceAccount["private_key_id"],
// Subject is the optional user to impersonate.
Subject: "",
// Scopes optionally specifies a list of requested permission scopes.
Scopes: []string{
"https://www.googleapis.com/auth/devstorage.readonly",
},
// TokenURL is the endpoint required to complete the 2-legged JWT flow.
TokenURL: firebaseServiceAccount["token_uri"],
// Expires optionally specifies how long the token is valid for.
Expires: 0,
}
ctx := context.Background()
return jwtConfig.Client(ctx)
}
func firebaseFunc() {
authedClient := firebaseClient()
msg := map[string]string{
"hello": "there",
"every": "one",
}
data, err := json.Marshal(msg)
if err != nil {
log.Fatal("JSON Marshall Error: ", err)
continue
}
resp, err := authedClient.Post(firebasePostUrl, "application/json", bytes.NewReader(data))
if err != nil {
log.Fatal("Firebase Error: ", err)
continue
}
log.Print("Firebase Response Code: ", resp.StatusCode)
}
The problem is, I always get this error:
{
"error" : "invalid_scope",
"error_description" : "https://www.googleapis.com/auth/devstorage.readonly is not a valid audience string."
}
I assume it is a type that the error is invalid_scope, and the description says it is an invalid audience (I assume the JWT aud parameter).
What do I use as my scope to allow me to read/write the Firebase Database (using the default "auth != null" rules)?
Edit: I found the answer here finally:
https://www.googleapis.com/auth/firebase
However now it gives me a 403 response when actually doing the post.
{
"error" : "Permission denied."
}

Answer 1

Ugh, I found the undocumented answer here. Currently you also need this scope:
https://www.googleapis.com/auth/userinfo.email