Error 400: redirect_uri_mismatch trying to access Google Drive

[MrYossu]

Hello,

I'm using the Google Drive C# API, and have a web site (Blazor, .NET5 in case it makes any difference) that has been working fine. I was using the client's Google credentials for this, had downloaded a JSON file (following instructions here) and all was well. When I first ran the web site in Visual Studio, I got the Google auth screen, in which I entered his email and password, and it worked. This created a JSON file in my web site which then allowed me to run the site next time without having to auth again.

In the credentials JSON file, I added the redirect URI, using the URI that VS uses when I debug the site. This gave me JSON file like this...

{
  "web": {
    "client_id": "xxxxxxxxxxxxxxxx",
    "project_id": "xxxxxxxxxxxxxxx",
    "auth_uri": "https://accounts.google.com/o/oauth2/auth",
    "token_uri": "https://oauth2.googleapis.com/token",
    "auth_provider_x509_cert_url": "https://www.googleapis.com/oauth2/v1/certs",
    "client_secret": "xxxxxxxxxxxxxxxxxxxxx",
    "redirect_uris": [
      "https://localhost:44378/authorize/",
      "https://localhost:44378/authorize"
    ]
  }
}

The code I use to create the Google service is quite closely copied from their .NET Quickstart (step 2)...

UserCredential credential;
using (FileStream stream = new(credJson, FileMode.Open, FileAccess.Read)) {
  credential = GoogleWebAuthorizationBroker
    .AuthorizeAsync(GoogleClientSecrets.FromStream(stream).Secrets, 
      new[] { DriveService.Scope.Drive }, 
      "user", 
      CancellationToken.None, 
      new FileDataStore(tokenPath, true))
    .Result;
}
DriveService service = new(new BaseClientService.Initializer {
  HttpClientInitializer = credential,
  ApplicationName = ""
});

That all worked fine. Now the client has set up another Google account specially for this site, and wants me to use that instead. No problem, I went to the Google developer console for the new account and did the same as before, ie configured the OAuth screen, created a new OAuth credential, downloaded the JSON file, added the redirect URIs as shown above, and replaced the existing JSON file with the new one.

When I try to debug, I get the error shown in the title.

Having spent hours researching this error, I have checked and double-checked the following...

• The URI that VS uses never changes. Specifically, the port is always 44378
• The base URI in the Google console and in my JSON file is the exact URI in the browser address bar when I'm debugging, I just added /authorize with and without the trailing slash
• The URI that the Google window shows is of the form http://127.0.0.1:59777/authorize/, although the port number changes every time. It is not picking up the port that VS uses. Adding the one Google shows is a waste of time, as next time I try, it shows a different port
• I have tried using 127.0.0.1 instead of localhost
• I have tried removing the port altogether from the redirect URI
• I have tried setting the redirect URIs in both the Google console (and waiting for them to update in case this was needed) and in the JSON file
• When I created the credentials, I set is as a web project, not a desktop one

None of this helped, I always get the same error.

The weird thing is that if I now revert my credentials JSON file back to what it was before (with the client's own Google account), I get the same error.

Anyone any ideas? As far as I can see, I've tried everything suggested, but still get this error.

Thanks

[gturconi]

Hello! Did you solve this problem? I have the same issue right now and I don't know what I can do