Subject: Re: [RFC net-next 1/3] net/tls_sw: support randomized zero padding

From: Sabrina Dubroca <[email-masked]>
Date: Tue, 17 Mar 2026 10:19:27 +0100

2026-03-16, 18:03:55 -0700, Jakub Kicinski wrote:
> On Tue, 17 Mar 2026 00:53:07 +0000 Wilfred Mallawa wrote:
> > > Or maybe you could refer to existing implementations of this feature
> > > in user space libs? The padding feature seems slightly nebulous, 
> > > I wasn't aware of anyone actually using it. Maybe I should ask...
> > > are you actually planning to use it, or are you checking a box?  
> > 
> > For upcoming WD hardware, we were planning on informing users to use
> > this feature if an extra layer of security can benefit their particular
> > configuration. But to answer your question, I think this falls more
> > into the "checking a box"...
> > 
> > I'm happy to drop this series if there's not much added value from
> > having this as an available option for users.
> 
> I'm not much of a security person, and maybe Sabrina will disagree
> but I feel like it's going to be hard for us to design this feature
> in a sensible way if we don't know at least one potential attack :S

No, same here, that's why I tried to CC some userspace developers on
the cover (as well as for awareness of what's going on in the kernel
and the API being discussed -- adding them here again).

My understanding is that attacks of this type are mainly "observers
will figure out what type of traffic I'm doing based on message
length", and I feel all those "traffic pattern masking" features are
only interesting for very paranoid users. The RFC links to some
research, and maybe the kind of statistics/machine learning that those
attacks require has improved since, which could make such attacks more
realistic? No idea.

-- 
Sabrina