Achilles Heel in Secure Boot: Breaking RSA Authentication and Bitstream Recovery from...
summary
A bug in the open-source FSBL for Zynq-7000 lets the boot code authenticate PHT2 but boot from an unverified PHT1 (a double-fetch PHT bug), enabling RSA-2048 authentication bypass with physical SD access. The team builds an SD-card switcher and uses a Starbleed-style readback to recover an AES-256 encrypted bitstream 32 bits at a time (each word needs a power cycle), demonstrates a working exploit, finds the flaw present since 2013, and reports CVE-2022-23822; vendor issues a patch.
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chapters (7)
- 0:00Introduction to Zynq-7000
- 3:02Secure boot process analysis
- 7:31Identifying the TOCTOU flaw
- 10:28Vulnerability disclosure
- 11:49Adapting the Starbleed attack
- 16:18Validation and demonstration
- 20:11Conclusion and summary
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