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

From: Eric Biggers
Date: Tue May 09 2023 - 21:21:51 EST

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

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

- Eric