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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/enrol/main.go
+3 -3
View File
@@ -1,13 +1,13 @@
// fleet-enrol — inline empty-NV first-boot TPM enrolment client.
//
// Invoked from the dracut hook (95dot1x-macsec/tpm-enrol.sh) ONLY when the
// secure build boots a host whose TPM NV 0x01800001 is empty. It:
// secure build boots a host whose TPM NV 0x01800100 is empty. It:
// 1. ensures an ECDSA signing key exists at a non-reserved owner handle
// (default 0x81000100 — deliberately NOT the EK slot 0x81010001),
// 2. builds a CSR with it (key never leaves the TPM),
// 3. submits CSR + device context to the enrolment broker, shows the returned
// fingerprint on the Plymouth splash, and polls until an admin approves,
// 4. writes the issued cert (DER) to NV 0x01800001.
// 4. writes the issued cert (DER) to NV 0x01800100.
//
// The hook then reboots into the normal secure path. Everything host-specific
// (key, cert, hostnqn) is created here at runtime — nothing is baked (invariant #1).
@@ -49,7 +49,7 @@ func main() {
var (
url = flag.String("url", "http://boot.fleet.lab/enrol", "enrolment broker base URL")
tpmPath = flag.String("tpm", "/dev/tpmrm0", "TPM device path")
nvHex = flag.String("nvindex", "0x01800001", "TPM NV index for the client cert")
nvHex = flag.String("nvindex", "0x01800100", "TPM NV index for the client cert")
handleHex = flag.String("handle", "0x81000100", "TPM persistent handle for the signing key (non-reserved owner handle; NOT the EK slot 0x81010001)")
cn = flag.String("cn", "fleet-host", "CSR CommonName (generic; identity is the cert serial)")
iface = flag.String("iface", "", "network interface for the device-context MAC")