Messages in this thread | | | Date | Thu, 03 Feb 2005 14:10:43 +1100 | From | Peter Williams <> | Subject | Re: [patch, 2.6.11-rc2] sched: RLIMIT_RT_CPU_RATIO feature |
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Jack O'Quin wrote: > Peter Williams <pwil3058@bigpond.net.au> writes: > > >>>>If you have the source code for the programs then they could be >>>>modified to drop the root euid after they've changed policy. Or >>>>even do the > > >>Paul Davis wrote: >> >>>This is insufficient, since they need to be able to drop RT >>>scheduling and then reacquire it again later. > > >>I believe that there are mechanisms that allow this. The setuid man >>page states that a process with non root real uid but setuid as root >>can use the seteuid call to use the _POSIX_SAVED_IDS mechanism to >>drop and regain root privileges as required. > > > Which every system cracker knows. Any attack on such a program is > going to re-acquire root privileges and take over the system. > > Temporarily dropping privileges gains no security whatsoever. It is > nothing more than a coding convenience.
Yes, to help avoid accidentally misusing the privileges.
> The program remains *inside* > the system security perimeter.
Which is why you have to be careful in writing setuid programs.
Peter -- Peter Williams pwil3058@bigpond.net.au
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