Re: WebSockets and masking

Hi,
I am answering multiple emails in one email.

I do not have a scenario where masking causes noticeable performance
issues. I was trying to figure out if it is possible to remove it if a
server wants to remove it.

From the discussion, I hear that requiring TLS on the client side may be
enough?

Dragana

On Sun, May 21, 2023 at 12:54 PM Martin Thomson <mt@lowentropy.net> wrote:

> On Sat, May 20, 2023, at 19:47, Ilari Liusvaara wrote:
> >   TLS will prevent the kind of middleboxes that were the motivation to
> >   adding masking to websockets.
>
> Not necessarily: those middleboxes were so terrible they would probably be
> vulnerable to an attack that mutated the ciphertext so that looked like
> cleartext HTTP.  See also the NAT slipstreaming attacks.  But also maybe
> not: they are probably not so widely deployed any more[*].  It has, after
> all, been some time.
>
> [*] I considered the possibility that they might not look at ports other
> than 80, but you can run TLS on port 80.
>
> It's only time then that might change our attitude toward masking.  We
> might reasonably conclude that middleboxes that are that awful are no
> longer worth protecting.  By extension, however, that means concluding that
> the endpoints, for whom those middleboxes might have caused problems, are
> less reliant on those middleboxes.  Remember that the attack was ultimately
> on endpoints that were being served up malicious content by those
> middleboxes.  But there is a lot less content around that is unsecured now,
> so maybe it's OK.
>
> FWIW, we deliberately shipped QUIC without equivalent protection against
> this particular class of attack.  It's harder to attack QUIC, but not
> impossible.
>
> >   And the kind of attacks discussed will not work through TLS
> >   terminating middlebox, and even if any attack worked, it would seem
> >   to be exploitable already.
>
> Yeah, I think that the requirement for TLS more or less rules out these
> sorts of tricks for protecting endpoints.  Endpoints need to protect
> themselves (and a TLS terminator is an endpoint as far as something like
> masking is concerned.)
>
>