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Date: Thu, 3 Jul 2014 21:07:39 +0100
From: Marek Kroemeke <kroemeke@...il.com>
To: oss-security@...ts.openwall.com
Subject: Re: Varnish - no CVE == bug regression

I doubt that CDNs like Akamai, Fastly(varnish?), Cloudflare(nginx?) etc..
would agree that the fact that a core part of their infrastructure could be
DoSed by one of their users is not a security vulnerability, but I'm happy
to be in minority regarding this view.

To be clear - I think that asserts in varnish are great, they decrease the
severity of the problem from something potentially very dangerous to "just
a DoS", but don't we usually try to track these as well with CVEs ?

regards,
Marek


On Thu, Jul 3, 2014 at 8:41 PM, Kurt Seifried <kseifried@...hat.com> wrote:

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> On 03/07/14 11:12 AM, Stefan B├╝hler wrote:
> > On Thu, 3 Jul 2014 08:15:06 +0000 Sven Kieske
> > <S.Kieske@...twald.de> wrote:
> >
> >> -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1
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> >> I'd agree with this. And I don't get the argument from
> >> poul-henning kamp, what I understand is: "hey, we trust our
> >> backend server" well, but your backend server can make you crash,
> >> so you probably shouldn't trust it in the first place?
> >>
> >> you _never_ can trust input, so you have to validate it, either
> >> way, at least enough to not crash or perform malicious actions.
> >>
> >> Am 03.07.2014 09:48, schrieb Kurt Seifried:
> >>> So as I understand this: Varnish front end for web servers, the
> >>> web servers can trigger varnish to restart. Are the back end
> >>> servers supposed to be able to cause varnish to restart?
> >>>
> >>> I'm guessing not. Scenario: hosting env, or a website with a
> >>> vuln, whatever, you can now cause the varnish front ends to
> >>> restart constantly, effectively causing a permanent denial of
> >>> service.
> >>>
> >>> That sounds CVE worthy. Or am I missing something?
> >
> > you should never trust *untrusted* input. your root shell usually
> > trusts the input it gets...
> >
> > so the valgrind developers decided that they consider the backend
> > webservers trusted, at least regarding the capability to cause a
> > DoS.
> >
> > for the record - so does lighttpd (a backend can trigger OOM as
> > lighty reads (nearly) as fast as possible from a backend, as
> > backends often only handle one request at a time); we usually tell
> > people to use X-sendfile instead of sending ISOs through php.
>
> That also sounds like it needs a CVE then. You should not be able to
> trivially DoS stuff, especially OOM, things should protect themselves
> from OOM'ing especially if they accept user controlled input from the
> network.
>
> > just because you disagree with such decisions doesn't make it CVE
> > worthy (missing or wrong documentation could).
>
> So to be clear your argument is that the http backends serviced by
> Varnish are supposed to be able to shut down Varnish, not by using an
> administrative channel/command but by executing a denial of service
> against Varnish? And that this is intended behaviour and thus not a
> security vulnerability?
>
> > in case you actually want to assign a CVE here, maybe we can get
> > one for the bad openssl default cipherstring too? because for that
> > it is really obvious that it is f*** wrong, but i think that none
> > was assigned because upstream didn't agree with it.
> >
> > regards, Stefan
> >
>
> - --
> Kurt Seifried -- Red Hat -- Product Security -- Cloud
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