go-witness Improper Verification of AWS EC2 Identity Documents

Summary

go-witness and witness are Go modules for generating attestations. In go-witness versions 0.8.6 and earlier and witness versions 0.9.2 and earlier the AWS attestor improperly verifies AWS EC2 instance identity documents. Verification can incorrectly succeed when a signature is not present or is empty, and when RSA signature verification fails. The attestor also embeds a single legacy global AWS public certificate and does not account for newer region specific certificates issued in 2024, making detection of forged documents difficult without additional trusted region data. An attacker able to supply or intercept instance identity document data (such as through Instance Metadata Service impersonation) can cause a forged identity document to be accepted, leading to incorrect trust decisions based on the attestation. This is fixed in go-witness 0.9.1 and witness 0.10.1. As a workaround, manually verify the included identity document, signature, and public key with standard tools (for example openssl) following AWS’s verification guidance, or disable use of the AWS attestor until upgraded.