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Date: Sat, 15 Jun 2019 15:22:22 -0400
From: Alex Gaynor <alex.gaynor@...il.com>
To: oss-security@...ts.openwall.com
Subject: Re: Thousands of vulnerabilities, almost no CVEs: OSS-Fuzz

You are completely right that this is not a novel phenomenon, though I
think the scale at which OSS-Fuzz has found vulnerabilities has genuinely
exacerbated this problem.

While it's true, some of the bugs found will not be exploitable, I think we
should not be overly dismissive.
https://scarybeastsecurity.blogspot.com/2016/11/0day-exploit-advancing-exploitation.html
is
an example of such a script-less exploit.
https://scarybeastsecurity.blogspot.com/2017/05/bleed-continues-18-byte-file-14k-bounty.html
is
an example of exploiting use of uninitialized value (one of the most common
bug classes in OSS-Fuzz, probably because so few people test with MSAN).

I think you're quite right that the central challenge here is the mismatch
between how Linux distributions operate and what their claims/people's
expectations are.

Alex

PS: I'd be remiss if I didn't at least mention that basically all the bug
classes we're discussing are induced by C/C++'s memory unsafety and better
programming language prevent them outright.

On Sat, Jun 15, 2019 at 3:01 PM Hanno Böck <hanno@...eck.de> wrote:

> Hi Alex,
>
> I think what you're describing has been going on for a while, even
> before oss-fuzz.
> A combination of compiler sanitizers and better fuzzing techniques has
> scaled up bug finding and fixing to a level we haven't had before.
>
> For distributions that promise to backport all security fixes that
> creates a situation where it's almost impossible to keep that promise,
> they just don't have the manpower to scale up at the same speed as
> people find bugs.
> Maybe the main takeaway here is to just recognize that, and maybe
> distros should be more honest here and be clear what they can and can't
> do. And if you run a parser in a high risk environment you may not want
> to rely on the outdated version shipping in some LTS distribution.
>
>
> But I also think it's good to keep some perspective of the bugs we're
> talking about.
> Many of the bugs oss-fuzz finds are of bug classes where it's quite
> unlikely that they directly lead to a security issue (e.g. out of
> bounds memory reads - which asan controversially calls "overflows").
> Even for the scarier looking vulns like write buffer overflows and use
> after free the situation is that these are usually not straightforward
> to exploit. All modern distributions have a combination of stack
> canaries, ASLR and nonexecutable memory. It's my understanding that
> while it's often possible to bypass those, doing so in non-scripting
> scenarios (e.g. in an image parser) is really hard and often impossible.
>
> I guess therefore it's still an overall win. While there's a number of
> bugs unfixed with public information, in the long term we'll get more
> robust code and the number of bugs present should be in steep decline.
>
>
> --
> Hanno Böck
> https://hboeck.de/
>
> mail/jabber: hanno@...eck.de
> GPG: FE73757FA60E4E21B937579FA5880072BBB51E42
>


-- 
All that is necessary for evil to succeed is for good people to do nothing.

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