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SubjectRe: Capabilities
Date
Khimenko Victor <khim@sch57.msk.ru> wrote:
>[snip snip]
> (for example now apache start with UID=0 so it has all capabilities and
> then with change of UID it'll drop all capabilities; in trusted system even
> with change of UID capabilities will retain: UID==0 is not special in "trusted
> Linux"). So system-wide option looks unavoidable :-((

Just because I'm a frick'n idiot, why can't we bind capability
mask to UID/GIDs? That would solve a lot of the administration and
``what happens if we mount a FAT filesystem?'' issues, IMHO.

* UID/GID capability masks (/etc/capabilites?) would be loaded
by /sbin/init. A user with the capability (CAP_SETUCAP?)
could modify current mapping via /proc/sys/????/capabilty.
* The capabilities are only acquired on SUID or login. Ie
r-xr-xr-x man man /usr/bin/man - No capabilties
r-sr-xr-x net bin /usr/bin/ping - Capabilties of the ``net'' user
r-xr-sr-x bin audio /usr/bin/play - Capabilties of the ``audio'' group

* Programs can _drop_ capabilties. If kernel support for capabities
is diabled, or their UID/GID is not in the mapping table, the
capability system call is a no-op.

* Allows for distributions that can turn on or off capability
support easily. With no need to rewrite existing daemons/applications.

* No need to change any filesystems. This technique would work
even on old Minix filesystems.

* Easy administration - just do the same ``look for files that
are SUID and owned by this UID'' that we already do.

So what do ya'll think?


--
Jason McMullan, Senior Linux Consultant, Linuxcare, Inc.
412.422.8077 tel, 415.701.0792 fax
jmcmullan@linuxcare.com, http://www.linuxcare.com/
Linuxcare. Support for the revolution.

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