Path: utzoo!mnetor!uunet!seismo!sundc!pitstop!sun!amdcad!ames!ucbcad!ucbvax!VENUS.YCC.YALE.EDU!LEICHTER
From: LEICHTER@VENUS.YCC.YALE.EDU ("Jerry Leichter ", LEICHTER-JERRY@CS.YALE.EDU)
Newsgroups: comp.os.vms
Subject: re: BACKUP under VMS 4.6 needs PHY_IO !?!?!
Message-ID: <8801082320.AA20704@ucbvax.Berkeley.EDU>
Date: 7 Jan 88 16:53:00 GMT
Sender: daemon@ucbvax.BERKELEY.EDU
Organization: The ARPA Internet
Lines: 51


	... [U]sing BACKUP for saving files on tape (for example) by an
	non-privileged user, the user gets this obscure error message :

	%BACKUP-F-LABELERR, error in tape label processing on MU:[]FOOFOO.BCK;
	-SYSTEM-F-BADPARAM, bad parameter value.

	We then asked the TSC center.  This is a well known bug under VMS 4.6
	they said.... BACKUP currently needs the privilege PHY_IO !

I don't remember the details of this exactly, but I think the problem is
really in one of the magtape drivers, not in BACKUP as such.

	...We decided to [install BACKUP with PHYS_IO, but it fails with the
	message]:
	 %DCL-W-ACTIMAGE, error activating image ENCRYPSHR
	 -CLI-E-IMGNAME, image file DUA0:[SYS0.][SYSLIB]ENCRYPSHR.EXE;3
	 -SYSTEM-F-PRIVINSTALL, shareable images must be installed to
	 	run privileged image

	Image  SYS$LIBRARY:ENCRYPSHR.EXE  must also be installed with that
	privilege!

	...

No; it need merely be INSTALL'ed.  No privileges are required, and in fact
installing a shareable image WITH privileges is meaningless - the privileges
will never be used for anything.  INSTALL'ing SYS$LIBRARY:ENCRYPSHR.EXE is
quite safe.

Since the problem only comes up with backups directly to tape, installing
BACKUP with PHYS_IO may be overkill.  Giving a user PHYS_IO is dangerous,
since with that privilege it is possible to do I/O's to the "raw disk" and
scribble over any file you like.  Giving BACKUP PHYS_IO is PROBABLY safe,
since BACKUP isn't about to do random physical I/O's to the disk, no matter
what you ask it to do.  Possibly, it will be able to override some tape
protections; it would take a real close look to be sure.

I suspect there's really no perfect solution to the problems this bug causes;
you'll have to evaluate your situation yourself.  A lot depends on how often
non-privileged users need to do backups to tapes.  At many installations, this
is rather rare - operators do regular backups, either from SYSTEM (or, prefer-
ably) from special, controlled accounts that can be given PHYS_IO with only a
very small added security exposure.  Most users make limited use of tapes,
and when they use them they don't write backups, but use some sort of appli-
cation that deals with the tape directly.  Other installations may have users
who write backup tapes all the time - to do distributions, for example.  These
obviously will need a different approach - perhaps each such user can be given
a second, captive account, which has PHYS_IO but is set up so that it can only
be used to run BACKUP.
							-- Jerry