Re: [PATCH] [RFC] Deter exploit bruteforcing

Pavel Machek
2015-01-02T23:08:41Z

On Sat 2015-01-03 00:00:22, Richard Weinberger wrote:
> Am 02.01.2015 um 23:54 schrieb Pavel Machek:
> > On Fri 2015-01-02 23:49:52, Jiri Kosina wrote:
> >> On Fri, 2 Jan 2015, Pavel Machek wrote:
> >>
> >>>> You also want to protect against binaries that are evil on purpose,
> >>>> right?
> >>>
> >>> Umm. No. Not by default. We don't want to break crashme or trinity by
> >>> default.
> >>
> >> I thought trinity is issuing syscalls directly (would make more sense than
> >> going through glibc, wouldn't it?) ... haven't checked the source though.
> >
> > Patch in this thread wanted to insert delays into kernel on SIGSEGV
> > processing. That's bad idea by default.
>
> No. This is not what this patch does.
>
> > But changing glibc to do sleep(30); abort(); instead of abort(); to
> > slow down bruteforcing of canaries makes some kind of sense... and
> > should be ok by default.
>
> As I saidn only focusing one the specific stack canary case is not enough.

Ok, so I am now saying "adding random delays to the kernel, hoping
they slow attacker down" is bad idea. Feel free to add my NAK to the
patch.

If really neccessary, "kill_me_slowly()" syscall would be acceptable,
but it seems just sleep(); abort(); combination is enough.

glibc should cover 99% cases where this matters, please just fix glibc,
others will follow.
Pavel
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