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Date: Tue, 25 Jun 2019 08:41:08 -0500 (CDT)
From: Bob Friesenhahn <bfriesen@...ple.dallas.tx.us>
To: oss-security@...ts.openwall.com
Subject: Re: Thousands of vulnerabilities, almost no CVEs:
OSS-Fuzz
On Mon, 24 Jun 2019, Alex Gaynor wrote:
> - Not having sooooo many vulnerabilities. While there's some dispute over
> just what % of the bugs that OSS-Fuzz and syzbot turn up are exploitable,
> there's no doubt that they find a _lot_ of them. Even if only 20% of
> OSS-Fuzz reports were truly exploitable vulnerabilities, that'd still be
>> 600 of them. We can't produce this many vulnerabilities and then try to
> clean up afterwards by finding them with fuzzing -- at some point the
> number of vulnerabilities simply overwhelms us. Tactics for reducing
> vulnerabilities in the first instance, like memory safe languages, are an
> important part of making this problem tractable.
>
> Do folks feel like there were important themes that this misses?
I see the assumption that 20% of oss-fuzz reports are exploitable
vulnerabilities. Where does this percentage estimate come from? What
does it mean to be "exploitable"?
>From working on fixing oss-fuzz detected bugs in GraphicsMagick I see
that many/most of the issues are not significant from a security
standpoint, assuming that the software is deployed in a way suitable
for its level of exposure. Common issues include:
* Huge uninitialized memory allocations (which do not really matter
under Linux since Linux does not reserve anything but virtual
memory space).
* Consumption of uninitialized data (e.g. image data) which is not
used to make important decisions. This is usually due to unhandled
cases or error handling which does not quit immediately.
* Tiny heap over-reads which are not past the bounds of the
underlying allocation.
* Heap over-reads or over-writes which cause an immediate core dump.
* Excessively slow code with the slowness emphasized by ASAN and
UBSAN code running vastly slower. The excessively slow code is not
necessarily noticeable in a normal compilation.
* Memory leaks.
* "undefined behavior" which nevertheless has a common behavior that
compilers have followed since the dawn of time.
The most important thing that oss-fuzz contributes is a large
collection of files which cause problems for unfixed software such
that only the unaware or foolish do not update to fixed versions.
Bob
--
Bob Friesenhahn
bfriesen@...ple.dallas.tx.us, http://www.simplesystems.org/users/bfriesen/
GraphicsMagick Maintainer, http://www.GraphicsMagick.org/
Public Key, http://www.simplesystems.org/users/bfriesen/public-key.txt
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