[PATCH net-next v4 4/5] tls: send a KeyUpdate at the record limit and on request

[Hannes Reinecke]

On 11/2/26 5:58 PM, Martin Belanger via B4 Relay wrote:
> From: Martin Belanger <martin.belanger at dell.com>
> 
> RFC 9846 section 5.5 requires a key update before the key reaches its
> usage limit, 2^24.5 full-size records for AES-GCM. The limit counts
> records, and only the record layer knows where records start and end.
> Section 4.7.3 also requires a reply to a KeyUpdate with
> update_requested, sent before the next Application Data record. Both
> need a KeyUpdate at an exact position in the record stream.
> 
> For a socket with a registered TX secret, send a KeyUpdate before the
> next Application Data record when the key has protected 2^24 records, as
> GnuTLS does, or when the peer asked for one. ChaCha20-Poly1305 has no
> record limit. The KeyUpdate is sent as a handshake record, which closes
> the open data record first. Pending encryptions are then completed, and
> only then is the next key installed.
> 
> Add TLS_TX_KEY_UPDATE to send a KeyUpdate now, optionally asking the
> peer to update too. It can only bring a KeyUpdate forward: the record
> limit is enforced either way. Following section 4.7.3, a new request
> to the peer waits for the answer to the previous one, and no more than
> 2^48-1 epochs are used.
> 
> Signed-off-by: Martin Belanger <martin.belanger at dell.com>
> ---
>   Documentation/networking/tls.rst |  17 +++++
>   include/net/tls.h                |   5 +-
>   include/uapi/linux/tls.h         |   1 +
>   net/tls/tls.h                    |   1 +
>   net/tls/tls_keyupdate.c          |   5 ++
>   net/tls/tls_main.c               |  38 +++++++++-
>   net/tls/tls_sw.c                 | 160 +++++++++++++++++++++++++++++++++++++++
>   7 files changed, 225 insertions(+), 2 deletions(-)
> 
Reviewed-by: Hannes Reinecke <hare at kernel.org>

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                  Kernel Storage Architect
hare at suse.de                                +49 911 74053 688
SUSE Software Solutions GmbH, Frankenstr. 146, 90461 Nürnberg
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