Steward is a critical element of the Confidential Computing infrastructure. The promise of Confidential Computing is fully utilized when the workload runtime (Enarx WebAssembly) deployed into a Trusted Execution Environment (TEE) is assessed and verified for correctness before an actual workload is released into a TEE from the registry (Drawbridge). An external attestation service must perform evidence verification and assessment of the hardware's trustworthiness.
Steward implements such attestation service in a modular, pluggable and scalable way.
Modular: The architecture of the Trusted Execution Environments significantly differs between hardware vendors. As a result, the content and structure of the evidence information are vendor-specific. The Steward employs modular design to process specific types of evidence in different backends.
Pluggable: Steward employs a pluggable and extensible architecture to allow the addition of new evidence information to the evidence payload as well as the support of new hardware architectures.
Scalable: Steward service is stateless. It receives a request with all the information from the client and makes an assessment. As a result, it is very lightweight and can be scaled up and down in response to the request load.
Attesting the hardware and workload runtime is only one part of the Steward's responsibility. The other is the translation of the vendor and use-case-specific attestation evidence into a format that standard services and interfaces on the Internet can trust. Such a standard is PKI, so Steward acts as a Certificate Authority that assesses the attestation evidence and issues a certificate based on this evidence. The certificate is returned to the workload and used by it to participate in the authenticated data exchanges with other services over the encrypted connections.
Steward is released under the Apache-2.0 license.
License: Apache-2.0
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