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SubjectRe: Capabilities done right [diff against 2.3.1]
Theodore Y. Ts'o writes:
> Date: Tue, 18 May 1999 11:04:55 +0200
> From: Pavel Machek <>
> That's hard part, because this way dynamic linker + anything run
> before main() runs with elevated priviledges. That's problem, at least
> for me.
> I just came up with a random thought ---- and I'd need to do more
> investigating about the ELF format to make sure this is actually doable,
> but I believe we can control the order in which constructurs get run,
> yes?
> So why not simply put the code which drops the privileges in a
> constructor which is engineered to be run first? If the way that
> constructor is setup uses a stylized code can be easily found by a
> setcap or checkcap program (i.e., give the constructor a standard name,
> and store the capability restriction in a standard variable referenced
> by the constructor), then you can get the ability to query/set the
> capabilities, but it's done in such a way which doesn't require any
> special kernel hacks to enable the feature.
> This is actually a really cool thing, since it means that people could
> start using it with the current stable kernel, without needing any
> kernel patches or needing to wait for Linux 2.4 to ship.

Yes, that has its attractions. A couple of months ago I suggested
doing it in the dynamic linker for dynamically linked binaries and in
an ELF code section for statically linked binaries.


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