About SW_HARDENING_NEEDED

[hyunsoo]

IAS returns "SW_HARDENING_NEEDED" if the mitigations against known attacks are not represented in the received quote. So, the question is that how IAS checks the fact that mitigations are correctly handled. I couldn't understand that IAS checks them even though the IAS is a remote party. 

Thank you

[JesusG_Intel]

Hello Hyunsoo,

From Unable to Determine the Criteria that the Remote Attestation Service (IAS) Examines to Attest the Validity of an Intel® Software Guard Extensions (Intel® SGX) Platform:

"Remote Attestation Service (IAS) examines only the quote sent by the service provider, or relying third party, to attest the enclave and the client platform.

Refer to the Data Structures chapter of the Intel® Software Guard Extensions (Intel® SGX) Attestation API Spec for details of the Attestation Evidence Payload."

Specifically, IAS uses the fields we discussed in your other post: MSRSIGNER, MRENCLAVE, the various SVNs, and the PSE Manifest.

The IAS attestation report contains a Platform Info Blob (PIB) that you can decode. The PIB is described in the Intel® Software Guard Extensions (Intel® SGX) Attestation API Spec.

For security purposes, Intel does not publish exactly how it uses all of that data to determine the security posture of the platform. Intel just tells you the data from the quote that it uses.

Whether the relying party should trust a quote with TCB issues is a policy decision. Security patches and recommended BIOS configurations harden the system against known vulnerabilities, and only the service provider can determine how much of a risk such a system presents. These decisions typically take the workload into account, as not all workloads are sensitive to specific vulnerabilities.

Sincerely,

Jesus G.

Intel Customer Support

[hyunsoo]

Hi G, Thanks for the reply.

Okay, I understand that the process detail may be confidential, but I just want to know high-level idea. For example, where that measure is performed and how they measure them are enough in this question. I guess that microcode has related something.  Is there a material associated with this question? I didn't find it.

[JesusG_Intel · Accepted solution]

Hello Hyunsoo,

All of that data together comprise what you have probably seen as the Trusted Computing Base (TCB). The Intel Attestation Service maintains a database of acceptable TCBs for all Intel processors that support SGX. During attestation, the data in the provided quote is compared to the known-good TCBs maintained by Intel and you get the comparison results.

Sincerely,

Jesus G.

Intel Customer Support

[JesusG_Intel]

Hyunsoo,

You may enjoy reading the SGX Explained paper: https://eprint.iacr.org/2016/086.pdf.

[JesusG_Intel]

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