TOCTOU Attacks Against Secure Boot And BootGuard
summary
Demonstrates a new TOCTOU technique that changes firmware after Intel BootGuard’s signature check by disabling the cache-as-RAM environment and forcing execute-in-place from SPI flash, then hijacking reads with a cheap FPGA SPI interceptor to serve malicious code and later restore the original bytes so measurements show TPM PCRs unchanged. Shows building the device (cheap dev board + small FPGA), captures SPI traces, and proves code executes early in boot and the system still boots. cache-as-RAM disable
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chapters (20)
- 0:00Introduction
- 1:20HDMI Issues
- 1:44BootGuard
- 3:09Overview
- 4:52Free Software Community
- 13:37What Could Go Wrong
- 14:31Logic Analyzer
- 15:18Data Log
- 16:29SetCore
- 18:09Summary
- 23:09Trammell
- 23:42Improved proof of concept
- 28:43Trammell setup
- 29:53Board management controller
- 30:58Supply chain attack
- 31:25Intel response
- 31:39Firmware patches
- 32:24The Fix
- 33:33Open Source Firmware
- 34:24Questions
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