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Relax google detection so it can run on SWTPM without patching libtpms #3

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Merged
HarryR merged 1 commit into from
Feb 7, 2026
Merged

Relax google detection so it can run on SWTPM without patching libtpms #3

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26 changes: 8 additions & 18 deletions crates/vaportpm-attest/src/a9n.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -20,10 +20,6 @@ const GCP_AK_TEMPLATE_NV_INDEX_RSA: u32 = 0x01c10001;
const GCP_AK_CERT_NV_INDEX_ECC: u32 = 0x01c10002;
/// GCP AK template NV index (ECC)
const GCP_AK_TEMPLATE_NV_INDEX_ECC: u32 = 0x01c10003;
/// GCP TPM manufacturer ID: "GOOG"
const GCP_MANUFACTURER_GOOG: u32 = 0x474F4F47;
/// TPM property: manufacturer
const TPM_PT_MANUFACTURER: u32 = 0x00000105;

/// Result type for attestation helper functions
/// Contains: (ak_pubkeys, attestation_data, gcp_attestation, ak_handle)
Expand Down Expand Up @@ -92,22 +88,16 @@ pub struct NitroAttestationData {
pub document: String,
}

/// Detect if running on GCP Shielded VM
/// Detect if running on a GCP-compatible TPM
///
/// Detection based on:
/// 1. TPM manufacturer ID is "GOOG"
/// 2. GCP AK template NV index exists
/// Uses duck typing: if the expected GCP NV indices exist, treat it as GCP.
/// This allows test TPMs (e.g. swtpm in QEMU) to be provisioned with the
/// same NV indices and use the GCP attestation path without needing a
/// "GOOG" manufacturer ID.
fn is_gcp_tpm(tpm: &mut Tpm) -> bool {
// Check manufacturer
if let Ok(manufacturer) = tpm.get_property(TPM_PT_MANUFACTURER) {
if manufacturer == GCP_MANUFACTURER_GOOG {
// Verify AK template exists
if tpm.nv_readpublic(GCP_AK_TEMPLATE_NV_INDEX_RSA).is_ok() {
return true;
}
}
}
false
tpm.nv_readpublic(GCP_AK_TEMPLATE_NV_INDEX_RSA).is_ok()
&& tpm.nv_readpublic(GCP_AK_TEMPLATE_NV_INDEX_ECC).is_ok()
&& tpm.nv_readpublic(GCP_AK_CERT_NV_INDEX_ECC).is_ok()
}

/// Generate a complete TPM attestation document
Expand Down