From: Al Petrofsky <al@petrofsky.org>
Cc: rms@gnu.org, monnier+gnu/emacs@RUM.cs.yale.edu, Pavel@Janik.cz,
walters@verbum.org, emacs-devel@gnu.org
Subject: Re: many packages write to `temporary-file-directory' insecurely
Date: Tue, 5 Mar 2002 11:57:45 -0800 [thread overview]
Message-ID: <200203051957.LAA01358@radish.petrofsky.org> (raw)
In-Reply-To: <200203051515.g25FFop01808@rum.cs.yale.edu> (monnier+gnu/emacs@RUM.cs.yale.edu)
> From: "Stefan Monnier" <monnier+gnu/emacs@RUM.cs.yale.edu>
>
> > My solution is to first write the scores securely into a temp file and
> > then move it to the desired place. This is safe, because if someone
> > has made the destination filename a symbolic link, then the rename
> > system call removes the link, rather than overwriting the linked-to file.
>
> The idea is alright, but:
>
> > This requires storing the file in a subdirectory of /tmp that is
> > world-writable without restriction, as opposed to /tmp itself, which
> > normally has its sticky bit set, thus forbidding people from deleting
> > others' files or renaming over them.
>
> This creates another problem, which comes from the fact that Emacs does
> not have the notion of file descriptor: an attacker can change the
> temp file into a symlink between the call to make-temp-file and the call
> to write-region.
The temp file is created directly in /tmp, which has sticky bit
protection, thus preventing an attacker from changing the temp file
into a symlink. If /tmp does not have sticky bit protection, then all
uses of make-temp-file are insecure.
> I really think it's better to require that the parent directory
> of the file we're writing to is only writable by ourselves and/or
> by root.
I agree, but it doesn't have to be root. If joe user installs emacs
with --prefix=/home/joe and the install process makes a world-writable
snake-scores file in directory /home/joe/var/emacs/game-scores, which
is unwritable by anyone but joe, then that is sufficient. Anyone who
uses the binaries has to trust joe anyway.
-al
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next prev parent reply other threads:[~2002-03-05 19:57 UTC|newest]
Thread overview: 46+ messages / expand[flat|nested] mbox.gz Atom feed top
2002-03-01 1:15 many packages write to `temporary-file-directory' insecurely Colin Walters
2002-03-02 11:52 ` Pavel Janík
2002-03-02 21:12 ` Colin Walters
2002-03-02 23:13 ` Pavel Janík
2002-03-03 17:18 ` Stefan Monnier
2002-03-03 20:36 ` Al Petrofsky
2002-03-04 0:07 ` Stefan Monnier
2002-03-04 23:41 ` Richard Stallman
2002-03-05 2:26 ` Al Petrofsky
2002-03-05 15:15 ` Stefan Monnier
2002-03-05 19:57 ` Al Petrofsky [this message]
2002-03-05 21:58 ` Richard Stallman
2002-03-04 23:40 ` Richard Stallman
2002-03-05 4:30 ` Colin Walters
2002-03-05 10:20 ` Andreas Schwab
2002-03-05 15:20 ` Stefan Monnier
2002-03-05 19:07 ` Richard Stallman
2002-03-06 4:40 ` Colin Walters
2002-03-06 7:35 ` Colin Walters
2002-03-06 16:59 ` Stefan Monnier
2002-03-07 2:40 ` Colin Walters
2002-03-07 6:00 ` Eli Zaretskii
2002-03-08 9:08 ` Richard Stallman
2002-03-08 9:08 ` Richard Stallman
2002-03-10 10:46 ` Colin Walters
2002-03-11 9:01 ` Richard Stallman
2002-03-17 22:08 ` Colin Walters
2002-03-18 20:06 ` Richard Stallman
2002-03-18 22:36 ` Colin Walters
2002-03-18 23:49 ` Steve Kemp
2002-03-19 0:31 ` Colin Walters
2002-03-19 6:22 ` Pavel Janík
2002-03-20 5:10 ` Richard Stallman
2002-03-27 23:46 ` Colin Walters
2002-03-31 1:24 ` Richard Stallman
2002-04-05 7:30 ` Colin Walters
2002-04-05 23:41 ` Richard Stallman
2002-03-06 16:59 ` Stefan Monnier
2002-03-06 19:05 ` Colin Walters
2002-03-08 9:07 ` Richard Stallman
2002-03-08 18:52 ` Colin Walters
2002-03-09 10:49 ` Richard Stallman
2002-03-03 14:39 ` Richard Stallman
2002-03-04 4:08 ` Richard Stallman
2002-03-04 4:08 ` Richard Stallman
2002-03-04 4:50 ` Colin Walters
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