[PATCH RFC net-next 1/5] tls: add HKDF-Expand-Label for the TLS 1.3 key schedule

[Hannes Reinecke]

On 10/26/26 1:36 AM, Martin Belanger via B4 Relay wrote:
> From: Martin Belanger <martin.belanger at dell.com>
> 
> A TLS 1.3 KeyUpdate derives the next traffic secret, key and IV with
> HKDF-Expand-Label (RFC 9846, section 7.2). Add the helper for the
> kernel to do this itself.
> 
> Only the part of the key schedule after the handshake is needed. The
> input is a traffic secret, which is already a pseudorandom key, so
> HKDF-Extract is not needed. Each output is at most Hash.length bytes,
> so each derivation is a single HMAC with the library SHA-256 or SHA-384
> functions.
> 
> Assisted-by: LLM
> Signed-off-by: Martin Belanger <martin.belanger at dell.com>
> ---
>   net/tls/Kconfig    |  2 ++
>   net/tls/Makefile   |  2 +-
>   net/tls/tls.h      |  2 ++
>   net/tls/tls_hkdf.c | 82 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
>   4 files changed, 87 insertions(+), 1 deletion(-)
> 
And another HKDF implementation. Maybe it's time to split if off (again).
But anyway.

Reviewed-by: Hannes Reinecke <hare at kernel.org>

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                  Kernel Storage Architect
hare at suse.de                                +49 911 74053 688
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