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tpm-enrol: move NV cert index off OEM-occupied 0x01800001 → 0x01800100

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The Dell 820 kept "finding a cert" and bypassing enrolment despite repeated BIOS
TPM clears. tpm2_nvreadpublic revealed 0x01800001 on that hardware is a FIRMWARE
platform index (platformcreate|policydelete|writelocked, 70 bytes — not our
cert; siblings at 0x01800003/4 + 0x01810000). platformcreate survives TPM2_Clear
and policydelete needs the platform's secret policy, so it's permanent and
unusable by us — the blind check false-positived on it, and enrolment could
never write there anyway. Same class of bug as the EK-handle collision.

Move the NV cert index default 0x01800001 -> 0x01800100 (free on the 820, owner
range, overridable via rd.dot1x.nvindex): cmdline (extract-artifacts.sh),
fleet-enrol -nvindex, the dracut hooks, bench scripts, CLAUDE.md invariant #1,
and design/SSP docs. The signing-key handle (0x81000100) is unchanged.

Harden WriteNVCert: refuse a platformcreate index with a clear "pick a free
owner index via rd.dot1x.nvindex" error instead of a confusing undefine
failure. Regression simtest/TestWriteNVCertRefusesPlatformIndex; NV roundtrip +
ReadNVCert tests moved to 0x01800100. All go tests + packer validate pass.
This commit is contained in:
Audiobuzz
2026-07-03 02:51:38 +00:00
parent 33de300af8
commit 6fe623c727
16 changed files with 97 additions and 36 deletions
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files/dracut/95dot1x-macsec/tpm-enrol.sh
+2 -2
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@@ -2,7 +2,7 @@
# tpm-enrol.sh — initqueue/settled hook, runs BEFORE dot1x-macsec-up.sh.
#
# INLINE empty-NV enrolment GATE (docs/tpm-enrolment-design.md). On a secure
# build whose TPM NV 0x01800001 is empty, it brings up a pre-auth network on the
# build whose TPM NV 0x01800100 is empty, it brings up a pre-auth network on the
# physical NIC and hands off to the out-of-VM `fleet-enrol` binary (Go + go-tpm),
# which generates the key/CSR, talks to the broker, shows the Plymouth
# fingerprint, and writes the issued cert to NV. On success this hook REBOOTS.
@@ -37,7 +37,7 @@ TESTMODE=0
[ "$(getarg rd.dot1x=)" = "0" ] && TESTMODE=1
# --- knobs (override on the kernel cmdline) ---------------------------------
NVINDEX=$(getarg rd.dot1x.nvindex=); [ -n "$NVINDEX" ] || NVINDEX=0x01800001
NVINDEX=$(getarg rd.dot1x.nvindex=); [ -n "$NVINDEX" ] || NVINDEX=0x01800100
# Persistent handle for the signing key: a NON-reserved owner handle. NOT the EK
# slot 0x81010001 (which most firmware/swtpm provisioning already occupies) nor
# the SRK 0x81000001 — see EnsureKey / CLAUDE.md invariant #1.