No Google & Facebook sign-in support for Yahoo oAuth form

Hi guys,

I am a web developer using Yahoo's oAuth service to let users sign into my app.

When someone signs up for an account at Yahoo, they get the option to use their Google or Facebook account as identification. but when people log into another application, using their Yahoo account. They do not get the option to use their Google or Facebook account.

Perhaps I have overlooked something, but I believe I don't have a Yahoo password, since I used Google to sign into Yahoo. So when I try to log into my app using my Yahoo account, I can't provide a password, and there is no other way of identifying myself to Yahoo.

For me personally this is not an issue, but I do want my users to be able to sign into my app, using Yahoo.

Am I missing something? Is there anything I can do to provide Google & Facebook sign-in support?