stage0: fail closed unless Secure Boot enabled and Deployed Mode#7
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Read SecureBoot and DeployedMode from the UEFI global variables at the top of run() (before network bring-up) and refuse to boot -- routed to the existing fail-closed shutdown -- unless both are exactly 1. Reading the variables here, pre-ExitBootServices, is reliable (unlike later from Linux). This folds the platform-state requirement into stage0's own behaviour: because stage0's binary is pinned by its firmware measurement, "authentic stage0 ran" now implies Secure Boot was enabled and the platform was in Deployed Mode -- even on firmware that does not measure DeployedMode into PCR 7. State only: the release signing cert is ephemeral and unknown at build time, so key identity is bound by the attested PCRs, not here. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
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What
stage0 reads
SecureBootandDeployedModefrom the UEFI global variables at the very top ofrun()(before network bring-up) and refuses to boot -- via the existing fail-closed shutdown -- unless both are exactly1. Reading them here, pre-ExitBootServices, is reliable, unlike later from Linux.Why
It makes the platform state part of stage0's measured behaviour: since stage0's binary is pinned by its firmware measurement, "authentic stage0 ran" now implies Secure Boot was enabled and the platform was in Deployed Mode -- even on firmware that doesn't fold
DeployedModeinto PCR 7. State only: the release signing cert is ephemeral and unknown at build time, so key identity stays bound by the attested PCRs, not by anything checked here.Verification
x86_64-unknown-uefiviamake.make smoke-boot-x86_64: 5/5 modes still PASS -- the test boot.disk enrolls PK/KEK/db andvirt-fw-vars --set-true DeployedMode --secure-boot, so the gate passes under the harness (and would fail-closed with a specific error otherwise).🤖 Generated with Claude Code