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Azure confidential VMs

This guide takes you from no setup to a full scan of an Azure confidential VM. The scan covers the VM's size and security type, Secure Boot and vTPM, confidential OS-disk encryption, the Secure Key Release policy on the key, and the Microsoft Azure Attestation provider that policy trusts.

Checks: see the Azure confidential VMs check list.

Before you begin

  • Install the CLI with the Azure extra: python -m pip install "./untrust-<version>-py3-none-any.whl[azure]". The scanner then signs in with DefaultAzureCredential. Without the extra, it asks the Azure CLI for a token, so run az login first.
  • To check the guest's attestation, capture a Microsoft Azure Attestation token from inside the VM.

1. Try the demo

untrust scan --platform azure-cvm --demo

[PASS] AZ-SKU-01  Configured as required.
[FAIL] AZ-BOOT-01 Secure Boot is off.
[FAIL] AZ-DISK-01 OS disk confidential encryption is 'VMGuestStateOnly' (guest state only).
[FAIL] AZ-SKR-01  branch 0: does not require azure-compliant-cvm (or debug off).
[FAIL] AZ-MAA-01  untrustdemo.eus2.attest.azure.net uses the 'AAD' trust model: anyone with RBAC write on the provider can replace its attestation policy.
[FAIL] AZ-DBG-01  the SEV-SNP guest is debuggable; Secure Boot is off.

5 of 6 checks failed.
Recorded results: 1 PASS, 5 FAIL, 0 SKIP, 0 ERROR. Skipped checks and errors remain unassessed.

2. Grant read access

The scan only reads. Required permissions › Azure confidential VMs lists every action it uses and includes a custom role definition. Reading a key's release policy is a Key Vault data-plane action, so it goes under DataActions. Assign the role at the resource group that holds the VM, the vault and the attestation provider.

3. Run your first scan

untrust scan --platform azure-cvm \
  --azure-subscription <subscription-id> \
  --azure-resource-group <resource-group> \
  --azure-vm <vm> \
  --azure-key-vault <vault> --azure-key <key> \
  --azure-attestation-provider <maa-provider> \
  --azure-attestation-token maa.jwt \
  --output report.json

If the release policy trusts attestation providers other than Microsoft's shared ones and the one you name, list them with --azure-approved-attestation-authority. See Scan inputs.

4. Read the results

  • FAIL: open the check's page from the check list for what a failure enables and how to fix it.
  • SKIP: the check was not given its input.
  • ERROR: a read was denied or a resource was not found.

SKIP and ERROR are never counted as a pass. See Output and exit codes.

5. Keep it running