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Message-ID: <56C5C9A3.6090800@balintreczey.hu>
Date: Thu, 18 Feb 2016 14:39:47 +0100
From: Balint Reczey <balint@...intreczey.hu>
To: oss-security@...ts.openwall.com
Subject: Re: Address Sanitizer local root
Hi,
On 02/18/2016 11:08 AM, Hanno Böck wrote:
> Hi,
>
> Thanks a lot for your analysis.
I would like to thank you for your analysis, too.
>
> On Wed, 17 Feb 2016 23:19:21 +0100
> Szabolcs Nagy <nsz@...t70.net> wrote:
>
>> https://blog.hboeck.de/archives/879-Safer-use-of-C-code-running-Gentoo-with-Address-Sanitizer.html
>> (the later was presented at FOSDEM 2016:
>> https://fosdem.org/2016/schedule/event/csafecode/ )
>>
>> While these are interesting projects, ASan should not be
>> used for hardening in production systems in its current form,
>> so at least the language ("hardening", "protection", "safe")
>> should be fixed.
>
> Given that this is my work (I did the asanized Gentoo and the FOSDEM
> talk) I think I should answer.
I'm the other guy, working on the special Debian port:
http://balintreczey.hu/blog/progress-report-on-hardened1-linux-amd64-a-potential-debian-port-with-pie-asan-ubsan-and-more/
>
> I hope I have made it clear that whether using asan for production
> purposes makes any sense was an open question to me. I have placed
> warnings that this is experimental and I didn't recommend any production
> use right now.
>
> I was aware about the performance and memory costs of asan, and I was
> aware that there are risks involved, but it appeared to me that
> balancing issues out it would still be a security win and might
> therefore be an option for some highly security sensitive environments.
> Your mail makes it clear to me that I was in error and at least in its
> current form asan is probably not suitable for secure use at all.
> I will add a note to my blogpost and the Gentoo wiki with a link to
> your mail to make this clear.
I was in a situation similar to Hanno's and I added notes about the
potential risks and limitations linking to this thread.
>
>
> Appart from that I wonder whether this should have any consequences for
> asan and which ones. Would it be desirable to:
> a) Try to fix security issues like the one you presented with suid
> binaries? (not sure what the best fix would be, maybe detect suid
> binaries and drop privileges back to user [not sure if that's even
> possible]).
> b) Leave issues unfixed and declare that asan is just not good for
> production use. In this case I agree that the asan documentation should
> probably include some more obvious warnings / explanations of the
> risks involved.
> c) Some other variant, like splitting asan into two different variants.
> One could imagine having a new cflag that would enable asan, but
> disable some of the ASAN_OPTIONS things like logging (however thinking
> about this I don't like it - if I imagine running asan on some kind of
> server I would want to be able to log issues).
>
ASAN and UBSAN were excellent for finding and fixing bugs in the
Debian toolchain and now I'm thinking about splitting the effort
into a QA focused version with ASAN and full UBSAN to find as many
bugs as possible and a hardening-focused one with trap-only UBSAN,
PIE, and other security-related features which are safe to use on
production systems but speed-wise are still tolerable.
The hardening-focused one should be able to run on
Grsecurity-enabled kernel.
I would also be interested in experimenting with a hardening-focused
version based on musl if it integrates ASAN features to libc.
Creating such new ports became much easier thanks to the fixes to
Debian's tools.
The hardened1-linux-amd64 port is not officially accepted to Debian
and the exact features it would provide can be changed. Ideally
it would ship a libc with an ABI enforcing safety measures (making
it ABI-incompatible with standard libc) and compiler defaults to
help writing secure programs. At the moment don't see such a libc
variant but musl + ASAN parts could be a good candidate or
SoftBoundCETS was also suggested to be used. I would like choose
a technology which runs on all CPU architectures, but if it can
be sped up by for example intel's MPX then it is a plus.
Comments are welcome!
Cheers,
Balint
[1] https://lists.debian.org/debian-devel/2014/04/msg00400.html
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