Re: [RFC PATCH 03/12] x86: Add early SHA support for Secure Launch early measurements

[Andy Lutomirski]

On Wed, Mar 25, 2020 at 12:43 PM Ross Philipson
<ross.philipson@xxxxxxxxxx> 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 SHA1 code here has its origins in the code in
> include/crypto/sha1_base.h. That code could not be pulled directly into
> the setup portion of the compressed kernel because of other dependencies
> it pulls in. So this is a modified copy of that code that still leverages
> the core SHA1 algorithm.
>
> Signed-off-by: Daniel P. Smith <dpsmith@xxxxxxxxxxxxxxxxxxxx>
> ---
>  arch/x86/Kconfig                        |  24 +++
>  arch/x86/boot/compressed/Makefile       |   4 +
>  arch/x86/boot/compressed/early_sha1.c   | 104 ++++++++++++
>  arch/x86/boot/compressed/early_sha1.h   |  17 ++
>  arch/x86/boot/compressed/early_sha256.c |   6 +
>  arch/x86/boot/compressed/early_sha512.c |   6 +
>  include/linux/sha512.h                  |  21 +++
>  lib/sha1.c                              |   4 +
>  lib/sha512.c                            | 209 ++++++++++++++++++++++++
>  9 files changed, 395 insertions(+)
>  create mode 100644 arch/x86/boot/compressed/early_sha1.c
>  create mode 100644 arch/x86/boot/compressed/early_sha1.h
>  create mode 100644 arch/x86/boot/compressed/early_sha256.c
>  create mode 100644 arch/x86/boot/compressed/early_sha512.c
>  create mode 100644 include/linux/sha512.h
>  create mode 100644 lib/sha512.c
>
> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> index 7f3406a9948b..f37057d3ce9f 100644
> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -2025,6 +2025,30 @@ config SECURE_LAUNCH
>           of all the modules and configuration information used for
>           boooting the operating system.
>
> +choice
> +       prompt "Select Secure Launch Algorithm for TPM2"
> +       depends on SECURE_LAUNCH
> +
> +config SECURE_LAUNCH_SHA1
> +       bool "Secure Launch TPM2 SHA1"
> +       help
> +         When using Secure Launch and TPM2 is present, use SHA1 hash
> +         algorithm for measurements.
> +

I'm surprised this is supported at all.  Why allow SHA1?