This library serves as a quoting data provider plugin for the Intel SGX Data Center Attestation Primitives (DCAP). Specifically, the Intel DCAP library will search out and load provider plugins, such as the Azure DCAP Client. This provider plugin is then used to fetch certain data files, such as platform certificates, TCB structures, and revocation lists.
The Azure DCAP Client fetches artifacts from an Azure-internal caching service. The purpose of this cache is to ensure that all Azure hosts always have the correct data available and local within the Azure cloud.
The data serviced by the Azure cache are all Intel-originating, and are rooted to Intel CAs. The cache serves simply to ensure that there are no external dependencies on Intel for workloads running on Azure infrastructure.
See src/Linux/README.MD.
The library builds the full URL of the artifacts served by the Azure-internal caching service from the parameters passed to the sgx_ql_get_revocation_info_t and sgx_get_qe_identity_info_t API calls.
For the certificate chain associated with an Intel SGX quote, each CRL Distribution Point is wrapped into an Azure-specific URL before being fetched by the Azure-DCAP-Client library. For example, the well-known Intel SGX Root CA CRL endpoint (https://certificates.trustedservices.intel.com/IntelSGXRootCA.crl) is served by the Azure-internal caching service at: https://global.acccache.azure.net/sgx/certificates/pckcrl?uri=https://certificates.trustedservices.intel.com/IntelSGXRootCA.crl&api-version=API_VERSION (where API_VERSION specifies the current API version).
The Azure-DCAP-Client library uses the following environment variables if set:
AZDCAP_CACHE - Represents the base directory where the library cache directory .az-dcap-client is created. The default value is $HOME in Linux and LocalLow in Windows.AZDCAP_BASE_CERT_URL and AZDCAP_CLIENT_ID - Used in conjunction to explicitly overwrite the default values for the PCK caching service. These should be used only for development purposes and they must not be used in any production environment.AZDCAP_COLLATERAL_VERSION - Used to specify the collateral version requested from the PCK caching service. Must be either'v1' or 'v2' if specified and defaults to 'v1' if unspecified.AZDCAP_DEBUG_LOG_LEVEL - Used to enable logging to stdout for debug purposes. Supported values are INFO, WARNING, and ERROR; any other values will fail silently. If a logging callback is set by the caller such as open enclave this setting will be ignored as the logging callback will have precedence. Log levels follow standard behavior: INFO logs everything, WARNING logs warnings and errors, and ERROR logs only errors. Default setting has logging off. These capatalized values are represented internally as strings.AZDCAP_PRIMARY_BASE_CERT_URL and AZDCAP_SECONDARY_BASE_CERT_URL - Used in conjunction to explicitly overwrite the default values of endpoints to fetch certificates. These should be used only for development purposes and they must not be used in any production environment.AZDCAP_BYPASS_BASE_URL- Used in conjunction to explicitly fetch certificates from PCK caching service instead of the host agent. This should be used only for development purposes and must not be used in any production environment.This project welcomes contributions and suggestions. Most contributions require you to agree to a Contributor License Agreement (CLA) declaring that you have the right to, and actually do, grant us the rights to use your contribution. For details, visit https://cla.microsoft.com.
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