Intel Management Engine is a microcontroller integrated into the Platform Controller Hub (PCH) microchip with a set of built-in peripherals. PCH manages almost all communication between the processor and peripherals; therefore, Intel ME has access to almost all data on the computer. Researchers found a flaw that allows executing unsigned code inside PCH on any motherboard for Skylake processors and later versions.
Intel ME has Manufacturing Mode designed to be used exclusively by motherboard manufacturers. This mode provides additional opportunities, and an attacker can gain an advantage over them. The risk imposed by this mode and its impact on Intel МЕ performance was discussed by many researchers, but numerous manufacturers still do not disable this mode.
When operating in Manufacturing Mode, Intel ME allows performing a specific command, after which ME region becomes writable via the SPI controller built into the motherboard. Having a possibility to run code on the attacked system and send commands to Intel ME, the attacker can rewrite Intel ME firmware to another version, including the version vulnerable to CVE-2017-5705, CVE-2017-5706, and CVE-2017-5707, and execute arbitrary code on Intel ME even if the system is patched.
This mode is enabled in MacBook (CVE-2018-4251, https://support.apple.com/en-us/HT208849), as well. Although firmware itself is additionally protected from SPI Flash region rewriting attacks (if access to any region is open, firmware does not allow OS download), researchers found an undocumented command that restarts Intel ME without the main system restart, which allows bypassing this protection. Not only Apple computers can be attacked this way.
In our talk we will disclose how attacker can exploit it for rewriting ME region.