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Date: Thu, 28 Sep 2023 17:49:08 +0200
From: Emilio Pozuelo Monfort <pochu27@...il.com>
To: oss-security@...ts.openwall.com
Subject: Re: CVE-2023-4863: libwebp: Heap buffer overflow in
WebP Codec
On 28/09/2023 14:36, Jeffrey Walton wrote:
> On Tue, Sep 26, 2023 at 11:37 AM Solar Designer <solar@...nwall.com> wrote:
>>
>> It was great to hear from Vincent that the newer libwebp changes are
>> just "Clean-ups, no security issues there." Yet I think it would also
>> be great if someone in here double-checks that.
>>
>> Regarding the assert failure detected by oss-fuzz, "A release build
>> would not be negatively affected." libwebp does specify -DNDEBUG by
>> default in:
>>
>> $ fgrep -rl DNDEBUG .
>> ./Makefile.vc
>> ./xcframeworkbuild.sh
>> ./iosbuild.sh
>> ./configure.ac
>> ./makefile.unix
>>
>> and there's also cmake support, but apparently cmake sets -DNDEBUG for
>> release builds by default. So at least this statement does appear to be
>> true for libwebp itself as built via the above means.
>>
>> However, there's also Gradle support, and the gradle* files do not
>> mention NDEBUG.
>>
>> Also, I wonder if there are other projects building code from libwebp
>> via different build environments.
>>
>> So there might be (a small minority of) uses of libwebp where the assert
>> exists in a release build of some project.
>
> Crypto++ caught a CVE because use of -DNDEBUG was not documented. The
> library's build system used -DNDEBUG (like libwebp), but folks who
> ported to other build systems did not use it. In my mind's eye, others
> who did not use the -DNDEBUG flag should have caught a CVE, not
> Crypto++. Also see CVE-2016-7420 and
> <http://seclists.org/oss-sec/2016/q3/520>.
>
> Crypto++ eventually took away the footgun by supplying its own
> CRYPTOPP_ASSERT that required a user to supply a switch to engage
> asserts. Asserts were no longer enabled by default when someone
> omitted -DNDEBUG. Also see
> <https://github.com/weidai11/cryptopp/blob/master/trap.h>.
>
> I've never seen a CVE for documentation before or since.
Here's a recent one:
https://www.cve.org/CVERecord?id=CVE-2023-0466
https://git.openssl.org/gitweb/?p=openssl.git;a=commitdiff;h=51e8a84ce742db0f6c70510d0159dad8f7825908
Cheers,
Emilio
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