Over the years, the use of televisions, monitors and projectors has made us accustomed to treating them as simple peripherals whose cables only transmit video. VGA cables may have I2C connectors for monitor detection, but in other cases, the security risk is small. On the other hand, the HDMI interface can carry more and more powerful ports, which means that it has jumped from just a signal cable to a connector full of attack vectors of interest to villains. Is it time to install HDMI firewall? [King Kevin] thinks so because he made one.
This is a very simple device because the non signal function of HDMI depends on a set of conductors that are not connected at all. Of course, this will also disconnect the on-board EEPROM in the connected equipment, so there is an EEPROM on the firewall board to replace it, and it must be programmed with the information of the relevant equipment.
HDMI is effective as the premise of the attack surface. We are sure that there will be attacks that can be executed on vulnerable displays, which in turn may do harmful things to anything connected to them. For most readers, the main value here may lie in introducing some contents of the HDMI interface and accessing the I2C interface.
Surprisingly, HDMI has a history of nearly 20 years, so it is not surprising that it has a long history of hacker attacks.