Did you ever find a way to block the ClientUseLocalDeviceAuthorizationfrom sending like you said in this message from Family sharing (de)authorize devices/accounts#267.
Okay, so I did some research on how family sharing works, and I think Valve's implementation is faulty. When you authorize a computer, you get back a "device token", which I believe is linked to a sentry file. When someone logs onto Steam on a computer with a library sharing authorization, it sends ClientUseLocalDeviceAuthorization with all of the tokens assigned to this machine, which apparently unlocks the appropriate shared libraries. Sending this with a token not assigned to the sentry file currently in use does not unlock the library.
However, if you don't send ClientUseLocalDeviceAuthorization at all, the license list sent to you includes all the games owned by people who shared their libraries with you, even if you aren't on an authorized machine. You can launch whatever shared games you want, and IPlayerService/IsPlayingSharedGame doesn't show you as using a borrowed license. Also, if the license owner launches a game, you don't get booted.
That said, if you call ClientUseLocalDeviceAuthorization, then the shared licenses get taken away and you're booted from any shared games you're playing. I wonder if there's a way by which the Steam client can be blocked from sending ClientUseLocalDeviceAuthorization, thus unlocking all shared games as if you owned them. Simply deleting the auth token from config.vdf doesn't seem to accomplish it, as the message still gets sent, but with no tokens. I bet a program could be developed to hook into the Steam client and block the message from being sent.” The main function i want to access is this “launch whatever shared games you want, and IPlayerService/IsPlayingSharedGame doesn't show you as using a borrowed license. Also, if the license owner launches a game, you don't get booted.” -Thanks
