Messages in this thread | | | Date | Thu, 2 Dec 1999 11:04:42 -0700 (MST) | From | "Peter J. Braam" <> | Subject | Re: Can't hardlink in different dirs. (BUG#826) |
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> On Wed, 1 Dec 1999, Peter J. Braam wrote: > > > 2. Hard links across directories are not permitted. Jan explained that > > security is an issue here. > > > > I think there is wrong thinking in the way Unix does things normally and > > the security argument goes away when the following reasoning is followed. > > > > Unix pretends a hard link is merely a modification of a directory. Of > > course it does add a name to new directory but it also subtly alters the > > attributes of the file in question, since it raises the file's link count. > > Effectively open does the same wrt keeping file alive. So?
I have said nothing about open - just about link.
> > > A perfectly acceptable fix for the (many) problems with link are to permit > > links only if: > > > > - the process can write to the target directory > > - process can modify the attributes of the file it wants to link >
Again, let's talk about link, not about open.
> Umhm. Wonderful. So open(2) is permitted only if we can modify the > attributes of file? I don't think so. And that provides the same thing - > you can use /proc/<pid>/fd/<fd> as a link. > > > This would work fine in Coda and also solves the problem that arise from > > people keeping hardlinks to insecure suid programs, since they normally > > cannot change their attributes. > > Or people with insecure suid programs can call truncate() before unlink(). > Problem solved. > > > Would Aegis be happy with that? Would Linux in general? > > Aegis - maybe. Linux in general? IMNSHO it seriously breaks normal UNIX > semantics.
OK, how serious? Does it outweigh the benefits.
If it remains CODA deficiency - fine, but if you want to make > this behaviour standard on normal filesystems... No, thanks. And I > suspect that you'll hear the same from *BSD folks. >
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