On 973879447 seconds since the Beginning of the UNIX epoch
jchacon@genuity.net wrote:
>
>Q: Why doesn't NetBSD implement random PID assignments like other free *IX's
>   offer?
>
>A: The stated reason this is done in other *IX's has often been touted as a
>   security win. i.e. programs with exploits that depend upon pid guessing 
>   are presumed to be harder to exploit when this feature is enabled.
>
>   However under basic analysis this is shown to be false for a variety of
>   reasons:
>
>        1. The pid space is small (2^16 generally), so instead of targeting
>           a specific pid all the attacker has to do is target them all. This
>           is by no means hard on any modern system. Even increasing the pid
>           space to 2^32 won't increase the overall work required beyond 
>           anything a modern system can't perform.
>
>        2. The randomness is truly questionable. In order to generate a pid
>           it must not already conflict with existing pids. On any 
>           reasonably busy system this makes guessing the "random" pid a fairly
>           basic task since it's now pseudo-random and follows a set of known
>           rules. 
>
>        3. The security win isn't really there. The programs that have the
>           exploits in them still have the exploits available if random pids
>           is the only answer provided. 
>
>There's my first shot, someone want to add/correct anything?
>
>James

You really need to disable ps, since using ps you can rather
effectively `guess' the pid of a process that runs for any length
of time before it drops its tmpfiles down.

And, if there are any tmpfile race conditions in a setuid program,
then to make random pids have any effect, you should disable the
return value of fork() -- since that allows the parent to effectively
`guess' the pid of the child.

 == Roland Dowdeswell                      http://www.Imrryr.ORG/~elric/  ==
 == The Unofficial NetBSD Web Pages        http://www.Imrryr.ORG/NetBSD/  ==
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