Key Broker Service

The Confidential Containers Key Broker Service (KBS) is a remote server which facilitates remote attestation. It is the reference implementation of Relying Party and Verifier in RATS role terminology.

This project relies on the Attestation-Service (AS) to verify TEE evidence.

The following TEE platforms are currently supported:

• AMD SEV-SNP
• Azure SNP vTPM
• Intel SGX
• Intel TDX

KBS has two deployment modes, which are consistent with RATS

• Background Check Mode: KBS integrates AS to verify TEE evidence, then distribute resource data.
• Passport Mode: One KBS integrates AS to verify TEE evidence and distribute tokens, the other KBS verifies the token then distributes resource data.

Background Check Mode

The name of Background Check is from RATS architecture.

In this mode, the Client in TEE conveys Evidence to KBS, which treats it as opaque and simply forwards it to an integrated Attestation Service. AS compares the Evidence against its appraisal policy, and returns an Attestation Token (including parsed evidence claims) to KBS. The KBS then compares the Attestation Token against its own appraisal policy and return the requested resource data to client.

Here, the KBS is corresponding to the Relying Party of RATS and the AS is corresponding to the Verifier of RATS.

Build and install KBS with native integrated AS in background check mode:

make background-check-kbs
make install-kbs

The optional compile parameters that can be added are as follows:

make background-check-kbs [HTTPS_CRYPTO=?] [POLICY_ENGINE=?] [AS_TYPES=?] [COCO_AS_INTEGRATION_TYPE=?]

where:

• HTTPS_CRYPTO: Can be rustls or openssl. Specify the library KBS uses to support HTTPS. Default value is rustls
• POLICY_ENGINE: Can be opa. Specify the resource policy engine type of KBS. If not set this parameter, KBS will not integrate resource policy engine.
• AS_TYPES: can be coco-as or amber-as. Specify the Attestation Service type KBS relies on.
• COCO_AS_INTEGRATION_TYPE: can be grpc or builtin. This parameter only takes effect when AS_TYPES=coco-as. Specify the integration mode of CoCo Attestation Service.

Passport Mode

The name of Passport is from RATS architecture.

In this mode, the Client in TEE conveys Evidence to one KBS which is responsible for issuing token, this KBS relies on an integrated AS to verify the Evidence against its appraisal policy. This KBS then gives back the Attestation Token which the Client treats as opaque data. The Client can then present the Attestation Token (including parsed evidence claims) to the other KBS, which is responsible for distributing resources. This KBS then compares the Token’s payload against its appraisal policy and returns the requested resource data to client.

Here, the KBS for issueing token is corresponding to the Verifier of RATS and the KBS for distributing resources is corresponding to the Rely Party of RATS.

Build and install KBS for issueing token:

make passport-issuer-kbs [HTTPS_CRYPTO=?] [AS_TYPES=?] [COCO_AS_INTEGRATION_TYPE=?]
make install-issuer-kbs

The explanation for compiling optional parameters is the same as above.

Build and install KBS for distributing resources:

make passport-resource-kbs [HTTPS_CRYPTO=?] [POLICY_ENGINE=?]
make install-resource-kbs

The explanation for compiling optional parameters is the same as above.

Documents

Quick Start

We provide a quick start guide to deploy KBS locally and conduct configuration and testing on Ubuntu 22.04.

Attestation Protocol

The KBS implements and supports a simple, vendor and hardware-agnostic implementation protocol to perform attestation.

API

KBS implements an HTTP-based, OpenAPI 3.1 compliant API. This API is formally described in its OpenAPI formatted specification.

Resource Repository

The resource repository where KBS store resource data.

Config

A custom, JSON-formatted configuration file can be provided to configure KBS.

Cluster

We provide a docker compose script for quickly deploying the KBS in Background check with gRPC AS, the Reference Value Provider and the Key Provider as local cluster services. Please refer to the Cluster Guide for a quick start.

Tools

KBS Client

We provide a KBS client rust SDK and binary cmdline tool.

Dockerfile

Build the KBS container (background check mode with native AS) image:

DOCKER_BUILDKIT=1 docker build -t kbs:coco-as . -f docker/Dockerfile