Messages in this thread |  | | Date | Fri, 13 Dec 2013 14:06:48 +0100 | From | Ingo Molnar <> | Subject | Re: [PATCH 1/9] Known exploit detection |
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* Ryan Mallon <rmallon@gmail.com> wrote:
> On 13/12/13 08:13, Kees Cook wrote: > > On Thu, Dec 12, 2013 at 11:06 AM, Theodore Ts'o <tytso@mit.edu> wrote: > >> On Thu, Dec 12, 2013 at 05:52:24PM +0100, vegard.nossum@oracle.com wrote: > >>> From: Vegard Nossum <vegard.nossum@oracle.com> > >>> > >>> The idea is simple -- since different kernel versions are vulnerable to > >>> different root exploits, hackers most likely try multiple exploits before > >>> they actually succeed. > > > > I like this idea. It serves a few purposes, not the least of which is > > very clearly marking in code where we've had problems, regardless of > > the fact that it reports badness to the system owner. And I think > > getting any additional notifications about bad behavior is a nice idea > > too. > > Though, if an attacker is running through a series of exploits, and > one eventually succeeds then the first thing to do would be to clean > traces of the _exploit() notifications from the syslog. [...]
There are several solutions to that:
1)
Critical sites use remote logging over a fast LAN, so a successful exploit would have to zap the remote logging daemon pretty quickly before the log message goes out over the network.
2)
Some sites also log to append-only media [such as a printer] or other append-only storage interfaces - which cannot be manipulated from the attacked system alone after a successful break-in.
3)
In future the exploit() code could trigger actual active defensive measures, such as immediately freezing all tasks of that UID and blocking further fork()s/exec()s of that UID.
Depending on how critical the security of the system is, such active measures might still be a preferable outcome even if there's a chance of false positives. (Such active measures that freeze the UID will also help with forensics, if the attack is indeed real.)
> [...] Since running through a series of exploits is pretty quick, > this can probably all be done before the sysadmin ever notices.
It's not necessarily the sysadmin the attacker is racing against, but against append-only logging and other defensive measures - which too are programs.
> The _exploit() notifications could also be used to spam the syslogs. > Although they are individually ratelimited, if there are enough > _exploit() markers in the kernel then an annoying person can cycle > through them all to generate large amounts of useless syslog.
AFAICS they are globally rate-limited, just like many other attacker-triggerable printk()s the kernel may generate.
Thanks,
Ingo
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