.NET SDK Invalid request while calling ProcessCodeFlowAsync

[Ghislain Sommervogel]

Hi Team,

I'm trying to setup a permanent connection (= a refreshToken process) to my app using OauthPKCE.

For this, I'm using the sample code provided here: https://github.com/dropbox/dropbox-sdk-dotnet/blob/main/dropbox-sdk-dotnet/Examples/OAuthPKCE/Progra...

I ran into a difficulty at this line:

      var tokenResult = await OAuthFlow.ProcessCodeFlowAsync(redirectUri, ApiKey, RedirectUri.ToString(), state);

My redirectURI seems to be correct (something like http://127.0.0.1:52475/authorize?code=gAY-xxxxxxxxxxxxxxxxxx), but the subsequent call to ProcessCodeFlowAsync results in an exception (Dropbox.Api.OAuth2Exception: 'invalid_request'). Error description says "client secret is missing". I guess it has something to do with the "App secret" setting, but I couldn't find where to provide this information in ProcessCodeFlowAsync, nor in the above instructions.

Any idea? Thanks a lot for your help.

Ghislain

[Greg-DB · Accepted solution]

If you're using the PKCE flow, the client secret shouldn't be required, so based on this error it looks like you're not actually in a PKCE flow.

Have you modified the OAuthPKCE sample code? I just tried it as is (just plugging in an app key) and it is working for me.

Can you confirm you set up the OAuthFlow object as a PKCEOAuthFlow as shown here and that the redirectUri you are passing in to ProcessCodeFlowAsync comes from the same flow started with the same object? (This error would occur if the authorization code you are exchanging wasn't actually retrieved using PKCE.)

[Ghislain Sommervogel]

Hello Greg,

Thanks for leading me to the solution. I didn't use the sample code "as is" because I had to adapt a preexisting code. The mistake was to call the GetAuthorizeUri function of DropboxOAuth2Helper instead of PKCEOAuthFlow.

Best regards,

Ghislain