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Article View: mod.computers.masscomp
Article #71

protection of memory

#71
From: William
Date: Fri, 21 Nov 1986 13:10
50 lines
2384 bytes
> We're having a problem with ps.  
> Under the -f option nothing is printed under the UID column.  Does
> anyone have an idea on why this may be?
> [ My best guess is that ps may not be chmod correctly... it does work 
> correctly on my systems... here is the output of an ls on some files of
> interest.
> 
> MUS% ls -la /bin/ps /dev/*mem
> -rwsr-sr-x   1 root     sys        47593 Aug 18 16:09 /bin/ps
> crw-rw-rw-   1 root     sys        3,  1 Aug 19 09:11 /dev/kmem
> crw-rw-rw-   1 root     sys        3,  0 Aug 19 09:11 /dev/mem
> 
> If your system does not look like this, my guess is that that is your 
> problem.
> 
> Stan, moderator]
> 
Stan,
I would be very concerned about the modes you suggest using for
/dev/mem and /dev/kmem. Imagine a non-superuser typing:

	cat /etc/passwd > /dev/mem

I would suggest something more like:

-rwsr-sr-x   1 root     sys        47593 Aug 18 16:09 /bin/ps
cr--r-----   1 root     sys        3,  1 Aug 19 09:11 /dev/kmem
cr--r-----   1 root     sys        3,  0 Aug 19 09:11 /dev/mem

A clever user could easily break into the system by writing into 
/dev/mem and changing their uid in the user structure. A more clever
user could possibly read a password from a clist. If you pay attention
to a few other files (/dev/swap) ps can be made :

-rwxr-sr-x   1 root     sys        47593 Aug 18 16:09 /bin/ps

This is how we run our Masscomp systems.

		Bill King @ abic.abnet.com
		Industrial Computer Division
		747 Alpha Drive, Highland Heights, OH   44143
		@{decvax,cwruecmp,pyramid}.UUCP:wrk@abic.ABNET.COM

[You are correct, of course. We run a relatively relaxed environment
here, so the memory protections are less of a problem for us. I would
still be concerned that kmem cannot be read by everyone since many
people like to pull out load averages and such.

Thanks for your comments.
Stan == moderator]
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Path: arc1-ca.pugleaf.net!utzoo!watmath!clyde!cbatt!cbosgd!soma!William King <rice!sun!abic!wrk>

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Path: arc1-ca.pugleaf.net!utzoo!watmath!clyde!cbatt!cbosgd!soma!William King <rice!sun!abic!wrk>
From: William@soma.UUCP
Newsgroups: mod.computers.masscomp
Subject: protection of memory
Message-ID: <2552@soma.bcm.tmc.edu>
Date: Fri, 21-Nov-86 08:10:20 EST
Article-I.D.: soma.2552
Posted: Fri Nov 21 08:10:20 1986
Date-Received: Sun, 23-Nov-86 03:15:50 EST
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