netdev - Re: Bug in MACSec - stops passing traffic after approx 5TB

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <CACcUnf_Q+3qOZD7M3RFhHPMqhMmvNELyGoXOZyfmj63tPDbNpQ@mail.gmail.com>
Date:   Wed, 17 Oct 2018 10:46:16 -0400
From:   Josh Coombs <jcoombs@...ff.gwi.net>
To:     sd@...asysnail.net
Cc:     netdev@...r.kernel.org
Subject: Re: Bug in MACSec - stops passing traffic after approx 5TB

I see it reusing SAs, so I'm good.

Joshua Coombs


On Wed, Oct 17, 2018 at 9:45 AM Josh Coombs <jcoombs@...ff.gwi.net> wrote:
>
> I've got wpa_supplicant working with macsec on Fedora, my test bed has
> shuffled 16 billion packets so far without interruption.  I am a bit
> concerned that I've just pushed the resource exhaustion issue down the
> road though, looking at the output of ip macsec show I see four SAs
> for TX and RX, it appears to negotiate a new pair every 3 to 3.5
> billion packets.  It doesn't appear to be ripping down old SAs.  What
> happens when available SA slots run out?
>
> Joshua Coombs
> GWI
>
> office 207-494-2140
> www.gwi.net
>
> On Mon, Oct 15, 2018 at 11:45 AM Josh Coombs <jcoombs@...ff.gwi.net> wrote:
> >
> > And confirmed, starting with a high packet number results in a very
> > short testbed run, 296 packets and then nothing, just as you surmised.
> > Sorry for raising the alarm falsely.  Looks like I need to roll my own
> > build of wpa_supplicant as the ubuntu builds don't include the macsec
> > driver, haven't tested Gentoo's ebuilds yet to see if they do.
> >
> > Josh Coombs
> >
> > On Sun, Oct 14, 2018 at 4:52 PM Josh Coombs <jcoombs@...ff.gwi.net> wrote:
> > >
> > > On Sun, Oct 14, 2018 at 4:24 PM Sabrina Dubroca <sd@...asysnail.net> wrote:
> > > >
> > > > 2018-10-14, 10:59:31 -0400, Josh Coombs wrote:
> > > > > I initially mistook this for a traffic control issue, but after
> > > > > stripping the test beds down to just the MACSec component, I can still
> > > > > replicate the issue.  After approximately 5TB of transfer / 4 billion
> > > > > packets over a MACSec link it stops passing traffic.
> > > >
> > > > I think you're just hitting packet number exhaustion. After 2^32
> > > > packets, the packet number would wrap to 0 and start being reused,
> > > > which breaks the crypto used by macsec. Before this point, you have to
> > > > add a new SA, and tell the macsec device to switch to it.
> > >
> > > I had not considered that, I naively thought as long as I didn't
> > > specify a replay window, it'd roll the PN over on it's own and life
> > > would be good.  I'll test that theory tomorrow, should be easy to
> > > prove out.
> > >
> > > > That's why you should be using wpa_supplicant. It will monitor the
> > > > growth of the packet number, and handle the rekey for you.
> > >
> > > Thank you for the heads up, I'll read up on this as well.
> > >
> > > Josh C