The HDMI (High Definition Multimedia Interface) standard has gained extensive market penetration. Nearly every piece of modern home theater equipment has HDMI support and most modern mobile devices actually have HDMI-capable outputs, though it may not be obvious. Lurking inside most modern HDMI-compatible devices is something called HDMI-CEC, or Consumer Electronics Control. This is the functionality that allows a media device to, for example, turn on your TV and change the TV’s input. That doesn’t sound interesting, but as we’ll see in this presentation, there are some very surprising things an attacker can do by exploiting CEC software implementations. Then there’s something called HEC or HDMI Ethernet Connection, which allows devices to establish an Ethernet connection of up to 100Mbit/s over their HDMI connections (newer HDMI standards raise the speed to 1Gbit/s).
Don’t think your mobile phone implements CEC? You might be wrong. Most modern Android-based phones and tablets have a Slimport(r) connection that supports HDMI-CEC. Ever heard of MHL (Mobile High-Definition Link)? Think Samsung and HTC (among other) mobile devices, and many JVC, Kenwood, Panasonic, and Sony car stereos – as many as 750 million devices in the world so far. Guess what? MHL supports HDMI-CEC as well. Let’s explore: