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From: levy@ttrdc.UUCP (Daniel R. Levy)
Newsgroups: net.sources.bugs
Subject: Re: What happens during an unlink(2)
Message-ID: <861@ttrdc.UUCP>
Date: Wed, 7-May-86 23:59:34 EDT
Article-I.D.: ttrdc.861
Posted: Wed May  7 23:59:34 1986
Date-Received: Sat, 10-May-86 07:04:42 EDT
References: <947@kitty.UUCP> <403@ukecc.UUCP> <979@kitty.UUCP> <422@ukecc.UUCP> <238@chronon.chronon.UUCP> <438@ukecc.UUCP>
Organization: AT&T, Computer Systems Division, Skokie, IL
Lines: 31
Keywords: Disk blocks sometimes get zeroed

In article <438@ukecc.UUCP>, edward@ukecc.UUCP (Edward C. Bennett) writes:
>In article <238@chronon.chronon.UUCP>, eric@chronon.UUCP (Eric Black) writes:
>> >	[discussion of what unlink(2) does]
>> Some unitory systems do, indeed, zero out disk blocks when de-allocated,
>> and similarly clear memory when freed.  Any system you sell to customers
>> with concerns about security will require this.  Check out DOD requirements
>> for secure systems in the "Department of Defense Trusted Computer
>> System Evaluation Criteria", publication CSC-STD-001-83 (my copy is
>> dated March 1985) for this and other interesting features...
>> Spooks aren't the only people who might desire disks & memory to be
>> cleansed when released, by the way.
>	You're absolutely right. I never though about that way.
>Edward C. Bennett

Hmmmm.  Maybe there should be an option to 'rm' to cause it to zero out
files before unlinking them?  (like rm -e [for erase], similar to VMS's
DELETE/ERASE)

I don't see however, why it would matter whether memory is zeroed upon
release, as long as it gets zeroed before reallocation by an ordinary user
(and accesses fail, e.g., with a "bus error," if one is trying to read or
write outside of one's allocated range).  After all, if you're the administrator
and can look at the memory contents you can spy on running processes anyway.
-- 
 -------------------------------    Disclaimer:  The views contained herein are
|       dan levy | yvel nad      |  my own and are not at all those of my em-
|         an engihacker @        |  ployer or the administrator of any computer
| at&t computer systems division |  upon which I may hack.
|        skokie, illinois        |
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