Pluggable Transport Specification

7. Pluggable Transport Specification

Cloak is designed as a Tor pluggable transport (PT), conforming to the PT specification outlined by the Tor developers. This approach allows seamless integration into the Tor network without requiring modifications to the existing Tor protocols. The interaction between Tor and Cloak follows the PT API.

Cloak’s lifecycle as a PT:

  1. Instance Configuration: Each Tor instance loads a configuration file (torrc) containing the path to the Cloak executable, command line arguments, and the Tor mode of operation (e.g., bridge or client).

  2. Cloak Subprocess: Upon launch, Tor starts Cloak as a subprocess, passing essential configuration variables to it through command line arguments. These variables expose Tor configurations, including the bridge remote address.

  3. Communication with Tor: Cloak reports its status back to Tor by writing success or error messages to the stdout in a standardized format. Tor captures and reads these messages, establishing communication with Cloak.

  4. Controlled Shutdown: Tor performs a controlled shutdown of Cloak to ensure proper memory management. It accomplishes this by closing the stdin of Cloak. In response, Cloak initiates a clean shutdown of all its components.

WebRTC Video Call Session: Apart from the initial configuration, Cloak is responsible for establishing a remote WebRTC video call session connection with the Cloak bridge. This connection enables the secure transmission of covert Tor data. The local Tor client fully manages Cloak, automatically configuring all options and preferences without any user interaction.