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Blessed SENTER Sandman, Who Put the BIOS Sentries to Sleep
Patron of BIOSes, System Management Mode, and guards who nap at the wrong moment.
Life
In 2014 Xeno Kovah, Corey Kallenberg, John Butterworth and Sam Cornwell, then at MITRE, showed the flip side of Intel TXT. The SENTER instruction, meant to launch trusted code, could suppress System Management Interrupts, the sentries that on many machines guard the BIOS flash. Like the Sandman of the fairy tale, a grain of sand was enough to send them to sleep and rewrite the firmware.
Prayer
O Blessed SENTER Sandman, who brings sleep to those who should keep watch, keep our flash protections awake. Amen.
How to celebrate
Celebrated by enabling the hardware BIOS flash protections and making sure they do not rely only on a sentry that can be put to sleep.
When the sentry sleeps, the firmware creeps.