Re: [PATCH v6 06/14] x86: Add early SHA support for Secure Launch early measurements

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On 5/9/23 21:21, Eric Biggers wrote:
On Thu, May 04, 2023 at 02:50:15PM +0000, Ross Philipson wrote:
From: "Daniel P. Smith" <dpsmith@xxxxxxxxxxxxxxxxxxxx>

The SHA algorithms are necessary to measure configuration information into
the TPM as early as possible before using the values. This implementation
uses the established approach of #including the SHA libraries directly in
the code since the compressed kernel is not uncompressed at this point.

The SHA code here has its origins in the code from the main kernel:

commit c4d5b9ffa31f ("crypto: sha1 - implement base layer for SHA-1")

That code could not be pulled directly into the setup portion of the
compressed kernel because of other dependencies it pulls in. The result
is this is a modified copy of that code that still leverages the core
SHA algorithms.

Signed-off-by: Daniel P. Smith <dpsmith@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Ross Philipson <ross.philipson@xxxxxxxxxx>

SHA-1 is insecure.  Why are you still using SHA-1?  Don't TPMs support SHA-2
now?

I think others have commented as to why SHA-1 is provided.

And if you absolutely MUST use SHA-1 despite it being insecure, please at least
don't obfuscate it by calling it simply "SHA".

Apologies that it appears that way to you. Typically when referring to the family or a subset of the SHA algorithms, SHA-0, SHA-1, SHA-2, and SHA-3, it is generally accepted to refer to them as the "SHA algorithms". And this is contrasted to the SM algorithms which the TCG spec provides for which we have no intentions to support ourselves, though others are welcome to contribute.

Again, apologies for misunderstanding and thank you for taking the time to review the series.

v/r,
dps




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