From: utzoo!decvax!cca!gwyn@Brl@sri-unix
Newsgroups: net.unix-wizards
Title: Re:  Chown: right or privilege
Article-I.D.: sri-unix.2824
Posted: Sat Aug 21 06:51:07 1982
Received: Sun Aug 22 02:25:27 1982

From:     Doug Gwyn 
Date:     11 Aug 82 16:11:21-EDT (Wed)
Yes, System III does allow a user to give away his files.
Incidentally, this is trivial to implement on an older UNIX,
so long as you remember to turn off the set-UID/set-GID bits!

The main arguments pro and con that I can think of are:

PRO:

The idea that an owner can do what he wants with his property.

Convenience in giving someone a copy of something (somewhat
mitigated by having to put the copy in a mutually-accessible
directory).

Spooling daemons and the like can sometimes hand files to their
intended owners without having to run set-UID root, so there
are fewer security-critical programs on the system.

CON:

A user can "give" a huge file to another user for the duration
of file accounting (say, overnight), then copy it again and
delete the old version (presumably still in his private directory)
when he needs the file.  This could ruin any file accounting by
ownership*size (System III accounting works this way).

This latter trick could be partially fixed by having chown()
apply an automatic umask of 077 to the file being chown'ed.
This would still let users maliciously put huge files under
somebody else's name, but at least they couldn't get them back
without the victim's assistance.