a catalog of bugs, or "Why to disable assembly optimization"

[Travis Biehn]

So good. So very good.

http://pdos.csail.mit.edu/papers/stack:sosp13.pdf

Or - a different reason to compile everything yourself. SlowOS plz.

-Travis


On Tue, Jul 22, 2014 at 6:58 PM, coderman <coderman at gmail.com> wrote:

> ---------- Forwarded message ----------
> From: Zooko Wilcox-OHearn <zooko at leastauthority.com>
> Date: Tue, Jul 22, 2014 at 12:23 PM
> Subject: a catalog of bugs, or "Why to disable assembly optimization"
>
>
> Folks:
>
> We had already agreed to disable assembly optimizations in pycryptopp,
> because there seem to have been a lot of bugs in the optimized
> assembly code in the past, and because the added speed really makes no
> difference to our uses, as far as I know.
>
> However, in order to explain and justify to other people (e.g. Debian
> packagers) why we are doing this, and why they should consider doing
> the same thing themselves, I just read through the entire history of
> issues in pycryptopp and classified whether they were runtime errors
> (and therefore potential security bugs) or build-time errors
> (therefore probably not), and whether they would have been avoided if
> we had been disabling assembly optimizations all along. Here are the
> results. They clearly show that we should disable the optimized
> assembly! About half of all the security-threatening bugs we've had
> would never have been an issue if we'd avoided assembly from the
> beginning.
>
> By the way, in my opinion the author of Crypto++, Wei Dai, is an
> *exceptionally* skilled, careful, and experienced coder, and I would
> assume that if Crypto++ has had this many security-threatening bugs in
> its optimized assembly code, then other crypto libraries that also use
> optimized assembly code also have at least as many.
>
> Here's the ticket to track this issue:
>
> https://tahoe-lafs.org/trac/pycryptopp/ticket/85
>
> bugs that cause run-time failures
> =================================
>
> (These bugs are potential security issues.)
>
> * would have been avoided by DISABLE_ASM:
>   - https://tahoe-lafs.org/trac/pycryptopp/ticket/24
>   - https://tahoe-lafs.org/trac/pycryptopp/ticket/31
>   - https://tahoe-lafs.org/trac/pycryptopp/ticket/45 (three
> *different* bugs in the assembly implementation)
>   - https://tahoe-lafs.org/trac/pycryptopp/ticket/67
>   - https://tahoe-lafs.org/trac/pycryptopp/ticket/84
>   - https://tahoe-lafs.org/trac/pycryptopp/ticket/86
>
> * unclear if it would have been avoided if we'd used DISABLE_ASM:
>   - https://tahoe-lafs.org/trac/pycryptopp/ticket/65
>
> * would not have been avoided by DISABLE_ASM:
>   - https://tahoe-lafs.org/trac/pycryptopp/ticket/17
>   - https://tahoe-lafs.org/trac/pycryptopp/ticket/44
>   - https://tahoe-lafs.org/trac/pycryptopp/ticket/83
>
> * would not have been avoided by DISABLE_ASM (but would have been
> avoided by using cffi instead of CPython API)
>   - https://tahoe-lafs.org/trac/pycryptopp/ticket/19
>   - https://tahoe-lafs.org/trac/pycryptopp/ticket/70
>   - https://tahoe-lafs.org/trac/pycryptopp/ticket/80
>
> * would have been avoided if we *didn't* use DISABLE_ASM! (A bug only
> in the non-ASM version!)
>   - https://tahoe-lafs.org/trac/pycryptopp/ticket/66
>
>
> bugs that cause deterministic build or compilation failures
> ===========================================================
>
> (These bugs are *typically* not potential security issues but they can
> be, and in any case they are engineering/deployment issues.)
>
> * would have been avoided by DISABLE_ASM:
>   - https://tahoe-lafs.org/trac/pycryptopp/ticket/37
>   - https://tahoe-lafs.org/trac/pycryptopp/ticket/96
>
> * would not have been avoided by DISABLE_ASM:
>   - https://tahoe-lafs.org/trac/pycryptopp/ticket/22
>   - https://tahoe-lafs.org/trac/pycryptopp/ticket/23
>   - https://tahoe-lafs.org/trac/pycryptopp/ticket/32
>   - https://tahoe-lafs.org/trac/pycryptopp/ticket/39
>   - https://tahoe-lafs.org/trac/pycryptopp/ticket/62
>   - https://tahoe-lafs.org/trac/pycryptopp/ticket/77
>   - https://tahoe-lafs.org/trac/pycryptopp/ticket/78
>
>
> --
> Regards,
>
> Zooko Wilcox-O'Hearn
>
> Founder, CEO, and Customer Support Rep
> https://LeastAuthority.com
> Freedom matters.
>



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