Trust is of paramount concern for tenants to deploy their security-sensitive
services in the cloud. The integrity of VMs in which these services are
deployed needs to be ensured even in the presence of powerful adversaries with
administrative access to the cloud. Traditional approaches for solving this
challenge leverage trusted computing techniques, e.g., vTPM, or hardware CPU
extensions, e.g., AMD SEV. But, they are vulnerable to powerful adversaries, or
they provide only load time (not runtime) integrity measurements of VMs.
We propose WELES, a protocol allowing tenants to establish and maintain trust
in VM runtime integrity of software and its configuration. WELES is transparent
to the VM configuration and setup. It performs an implicit attestation of VMs
during a secure login and binds the VM integrity state with the secure
connection. Our prototype’s evaluation shows that WELES is practical and incurs
low performance overhead.