Re: [PATCH 1/9] handshake: Require admin permission for DONE command

On 6/5/26 19:34, Chuck Lever wrote:
> From: Chuck Lever <[email protected]>
> 
> ACCEPT and DONE are the two downcalls of the handshake genl
> family, both intended for use by the trusted handshake agent
> (tlshd). ACCEPT already requires GENL_ADMIN_PERM; DONE has
> no privilege check at all.
> 
> The fd-lookup in handshake_nl_done_doit() only confirms that
> some pending handshake request exists for the supplied sockfd;
> it does not authenticate the sender. An unprivileged process
> that guesses or observes a valid sockfd can therefore submit
> a DONE with HANDSHAKE_A_DONE_STATUS == 0, leaving the kernel
> consumer to proceed as if the handshake succeeded. A non-zero
> status on a forged DONE tears down a legitimate in-flight
> handshake before tlshd can report its real result.
> 
> A subsequent patch teaches the DONE handler to carry session
> tags consumed for access control. That work makes closing the
> existing gap a prerequisite, but the gap itself predates tags.
> 
> Fixes: 3b3009ea8abb ("net/handshake: Create a NETLINK service for handling handshake requests")
> Signed-off-by: Chuck Lever <[email protected]>
> ---
>   Documentation/netlink/specs/handshake.yaml | 1 +
>   net/handshake/genl.c                       | 2 +-
>   2 files changed, 2 insertions(+), 1 deletion(-)
> 
Reviewed-by: Hannes Reinecke <[email protected]>

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                  Kernel Storage Architect
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