Path: utzoo!mnetor!uunet!lll-winken!lll-tis!ames!umd5!brl-adm!adm!rbj@icst-cmr.arpa
From: rbj@icst-cmr.arpa (Root Boy Jim)
Newsgroups: comp.unix.wizards
Subject: Writing to A NON-Existing File in \"C\"
Message-ID: <13108@brl-adm.ARPA>
Date: 25 Apr 88 23:26:26 GMT
Sender: news@brl-adm.ARPA
Lines: 24


   [access is ...]
   ... for setuid programs to determine whether the real user can access
   a file.  (It's the wrong way to do even that, because of the resulting
   window, but that's another can of worms.)

OK, now to address that window issue. As I understand it, the basic
objection to access is a window of vulnerability between deciding if
access to a file is okay, and actually doing something to that file,
(for the purposes of this discussion, let's say open) someone could
possibly substitute another file. I propose enclosing the whole mess
between two stat's, and testing whether the vital statistics match.
Then, you can assume it's the same file you asks about via access.

					   der Mouse

			   uucp: mouse@mcgill-vision.uucp
			   arpa: mouse@larry.mcrcim.mcgill.edu

	(Root Boy) Jim Cottrell	<rbj@icst-cmr.arpa>
	National Bureau of Standards
	Flamer's Hotline: (301) 975-5688
	The opinions expressed are solely my own
	and do not reflect NBS policy or agreement
	Now, let's SEND OUT for QUICHE!!