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KMS enclave key attestation binds a specific deployment context

kms_key_enclave_attestation_no_deployment_binding

Severityinformational
Servicekms
by Prowler
encryptiontrust-boundaries

Sensitive Allow statements on enclave KMS keys are checked for deployment-context binding: PCR3 (parent IAM role, AWS-recommended), PCR4 (parent instance ID), PCR8 (EIF signing cert), or an account-level condition (aws:PrincipalAccount / SourceAccount / OrgID / ResourceAccount / OrgPaths) paired with a RecipientAttestation binding. PCR0/PCR1/PCR2 travel with the EIF and do not bind deployment.

Risk

A key policy bound only to image PCRs (PCR0/PCR1/PCR2) accepts the same EIF running anywhere, including an attacker-controlled account or instance. Deployment-context conditions bind attestation to a specific execution context so a leaked or replicated image cannot silently reuse the key. Materiality depends on application-layer controls.

Run this check with Prowler CLI

prowler aws --checks kms_key_enclave_attestation_no_deployment_binding

Run in Prowler Cloud

Recommendation

Pair every image binding (kms:RecipientAttestation:PCR0, PCR1, PCR2) with PCR3 (parent IAM role), PCR4 (parent instance ID), PCR8 (EIF signing cert), or an account/org condition so the key policy binds to a specific deployment context rather than just an image identity. AWS recommends PCR3 + PCR8 together.

Remediation

CLI

aws kms put-key-policy --key-id <key-id> --policy-name default --policy file://enclave-policy-with-deployment-binding.json

Other
  1. Pair every image binding (kms:RecipientAttestation:PCR0/PCR1/PCR2) with at least one deployment-context binding: kms:RecipientAttestation:PCR3 (parent IAM role, AWS-recommended), PCR4 (parent instance ID), or PCR8 (EIF signing certificate). AWS recommends PCR3 + PCR8 together for portability.
  2. Alternatively add an account/org condition (aws:PrincipalAccount, aws:SourceAccount, aws:PrincipalOrgID, aws:ResourceAccount, aws:PrincipalOrgPaths) so only calls from the audited account or organization can present the attestation.
  3. Ensure operators are restrictive (StringEquals, ArnEquals) and values do not contain wildcards.

Source Code

Resource Type

AwsKmsKey

References

Related To

  • kms_key_enclave_attestation_not_enforced
  • kms_key_enclave_attestation_pcr_mismatch