Re: About ACL for IPC Object

From: zhou peng
Date: Fri Jan 22 2010 - 04:15:21 EST

Thank you all for so many solutions.

I want to control some IPC object (shm, msg queue, semphore) can be
accessed by which named user or named group just like file objects ACL

I studied the solution you all referred, The SELinux is powerful but
may be somewhat complicated. And I am confused with Christoph
Hellwig‘s solution using tmpfs.

2010/1/21 Christoph Hellwig <hch@xxxxxxxxxxxxx>:
> On Wed, Jan 20, 2010 at 07:02:27PM -0800, Casey Schaufler wrote:
>> zhou peng wrote:
>> > Hi all,
>> >
>> > There are ACL in file system, but why there are no ACL implementation
>> > in IPC object, eg. shm, message queue, FIFO?
>> >
>> Most people haven't noticed that IPC objects are even there, much less
>> that they have mode bits and not ACLs. Even when we were doing security
>> evaluations on Unix boxes in the 1990's they were considered insufficiently
>> interesting to justify the additional work to do ACLs.
>> If you really want ACLs on IPC objects it would make a dandy little
>> project for a summer. I would be happy to review patches.

Thanks. It's interesting to add ACL over IPC objects. I want to have a try.

> Or use the posix IPC mechanisms.  The Posix shared memory has ACL by
> using tmpfs as the backing store, and we could add similar support to
> Posix messages queues as they are also backed by a normal filesystem.

Christoph Hellwig, This way may be convinent. Could you give some
detailed message. :)
I only find /proc/ipc/shm file which contain the info of shm objs,and
tmpfs on /dev/shm which is empty.

> Adding this support to the old SYSV IPC mechanisms would be much harder
> as they do not fit into the file backed model we use everywhere else at
> all.

Just like file objects, the mode bits are implment over IPC objects
without file backed, so I think adding ACL support to IPC objects may
be somewhat reasonable :)


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