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SubjectRe: Capabilities
In <38AF2945.E714F508@bestbits.at> Andreas Gruenbacher (a.gruenbacher@bestbits.at) wrote:
> On Sat, 19 Feb 2000 14:51:51 -0500
> Theodore Y. Ts'o wrote:
>>
>> [...] So the first question is whether we want to try to
>> conform to the last POSIX draft, and (as much as possible) be compatible
>> with the other Trusted Unixes out there.

> That's very important. Yes.

>> [...]
>> Now, with all of that being said, if you don't want the full
>> POSIX model, it's probably easier to simply leave things the way they
>> are right now, and not try to put anything in the filesystem. Just
>> simply allow programs to be setuid root, and then let them drop
>> whatever capabilities they don't need as soon as they start running in
>> main() --- hopefully before any stack overrun vulnerabilities have a
>> chance to execute. :-)

> The kernel should boot up in non-trusted mode (with root and SUID root binaries
> recieving full capabilities, as it's implemented now).

> A simple syscall could then switch the kernel to trusted mode. Afterwards, root
> is treated as all other others.

> Switching to trusted mode then can easily be done in init scripts, ...

> Of course, there shouldn't be a way to switch back to non-trusted mode...

IMNSHO trusted mode or untrusted mode should be filesystem flag: in trusted
mode LOTS of programs should be configured differently. Perhaps mount option
will be enough. It's NOT system-wide issue, rather filesystem-wide (kernel
works in trusted mode even now (modulo things like mtrr not yet converted to
capabilities), just exec part work in non-trusted mode...





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