Firebase: Authenticating from C# .NET Core application

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I am attempting to connect a local .NET Core project to a Firebase project. I am using the Google documentation at https://cloud.google.com/dotnet/docs/reference/Google.Cloud.Firestore/latest:

private async Task<Dictionary<string, object>> GetData()
{
    string projectId = "My-Project";

    FirestoreDb db = FirestoreDb.Create(projectId);
    Dictionary<string, object> documentDictionary = new Dictionary<string, object>();

    ...
}

When it hits the call to create an instance of the project (FirestoreDb.Create(projectId)), I receive this error:

Error: System.InvalidOperationException: The Application Default Credentials are not available. They are available if running in Google Compute Engine. Otherwise, the environment variable GOOGLE_APPLICATION_CREDENTIALS must be defined pointing to a file defining the credentials. See https://developers.google.com/accounts/docs/application-default-credentials for more information.
   at Google.Apis.Auth.OAuth2.DefaultCredentialProvider.CreateDefaultCredentialAsync()

I have exported the service account from Firebase into a JSON file, generating a private key and saving it locally:

Export service account from Firebase

I have added the path of the key file to this JSON file in an environment variable:

Store the JSON file in an environment variable

However, I continue to get the error.

There is one way I have been able to authenticate, and that was using the example code at https://cloud.google.com/docs/authentication/production:

public object AuthExplicit(string projectId, string jsonPath) {
 var credential = GoogleCredential.FromFile(jsonPath);
 var storage = StorageClient.Create(credential);

 var buckets = storage.ListBuckets(projectId);
 foreach (var bucket in buckets)
 {
    Console.WriteLine(bucket.Name);
 }
 return null;
}

However, I don't know how (or if it's possible) to link that authentication code with Firebase in order to retrieve my data.

Is there any guidance you can provide so I can properly authenticate and pull my data?

firebase google-cloud-platform c#
2 Answers

This link provides a reason why this error is being caused.

I – If GOOGLE_APPLICATION_CREDENTIALS is SET and it uses the service account file path using the value associated with the above Environment variable GOOGLE_APPLICATION_CREDENTIALS

II – If GOOGLE_APPLICATION_CREDENTIALS is not SET, then the following preferences are set:

  1. ADC uses a service account file that is running the code.

  2. Otherwise, if a service account also does exist, then ADC uses the default service account that Compute Engine, Google Kubernetes Engine, App Engine, and Cloud Functions provide.

Try to debug the application locally by doing the following:

If you already have a service account created, then it applies to an application instead of an individual user. You need to authenticate a service account while accessing your IAP-secured resources.

Please make sure to set Environment Variable GOOGLE_APPLICATION_CREDENTIALS with the secured key JSON file path. Example

C#:

Environment.SetEnvironmentVariable("GOOGLE_APPLICATION_CREDENTIALS", "secured-service-account.json");
user_175443120

The missing step was calling the FirebaseApp.Create() method, as described in the Firebase authentication documentation.

I modified my application to add that method before the call to FirestoreDb.Create(), and that did it. Here is the modified code:

private async Task<Dictionary<string, object>> GetData() {
    string projectId = "My-Project";

    FirebaseApp.Create(new AppOptions()
    {
        Credential = GoogleCredential.GetApplicationDefault(),
    });

    FirestoreDb db = FirestoreDb.Create(projectId);
    Dictionary<string, object> dd = new Dictionary<string, object>();
    ...
}
user_56058980
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