From: Stefan Monnier <monnier@iro.umontreal.ca>
To: rms@gnu.org
Cc: emacs-pretest-bug@gnu.org, christopher.ian.moore@gmail.com,
svenjoac@gmx.de
Subject: Re: creating backups in temporary directories
Date: Sun, 09 Sep 2007 15:44:56 -0400 [thread overview]
Message-ID: <jwvy7ffeid0.fsf-monnier+emacs@gnu.org> (raw)
In-Reply-To: <E1IU6HI-0002B7-Rs@fencepost.gnu.org> (Richard Stallman's message of "Sat\, 08 Sep 2007 15\:47\:36 -0400")
> IIUC this depends on backup-by-copying. If backup-by-copying is nil,
> then the problem is indeed not present, but you get another one
> insted: right after Emacs moves /tmp/foo to /tmp/foo~ another user can
> add a symlink /tmp/foo that points to an interesting place and then
> when Emacs subsequently writes the new /tmp/foo it gets written to the
> location chosen by the attacker.
> I think we can't do anything to get rid of that problem.
I'd tend to agree.
> Writing thru symlinks is an important feature;
Very much so.
> if other people can create the symlink, it follows inevitably that they
> could do this.
In a directory with mode 777, that's true: everything is dangerous.
But in a directory with mode 1777 when you open a file that *you* own,
nobody else can remove it or rename it, so normally nobody can replace it
with a symlink. Emacs creates the problem when it moves /tmp/foo to
/tmp/foo~ at which point /tmp/foo is free for an attacker to take.
Stefan
next prev parent reply other threads:[~2007-09-09 19:44 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-09-07 10:42 creating backups in temporary directories Chris Moore
2007-09-07 15:36 ` David Kastrup
2007-09-07 17:57 ` Stefan Monnier
2007-09-07 19:43 ` Davis Herring
2007-09-07 19:49 ` Sven Joachim
2007-09-07 19:52 ` David Kastrup
2007-09-08 19:47 ` Richard Stallman
2007-09-07 20:47 ` Stefan Monnier
2007-09-08 19:47 ` Richard Stallman
2007-09-09 19:44 ` Stefan Monnier [this message]
2007-09-09 20:01 ` David Kastrup
2007-09-09 20:27 ` Andreas Schwab
2007-09-10 1:11 ` David Kastrup
2007-09-10 19:18 ` Davis Herring
2007-09-10 19:55 ` David Kastrup
[not found] ` <37852.128.165.123.18.1189451917.squirrel@webmail.lanl.gov>
2007-09-10 19:23 ` Davis Herring
2007-09-11 20:32 ` Richard Stallman
2007-09-11 21:17 ` Davis Herring
2007-09-10 1:12 ` Richard Stallman
2007-09-10 2:59 ` Stefan Monnier
2007-09-08 14:38 ` Chris Moore
2007-09-08 19:48 ` Richard Stallman
2007-09-09 19:41 ` Stefan Monnier
2007-09-09 19:45 ` David Kastrup
2007-09-10 1:12 ` Richard Stallman
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