Bugtraq mailing list archives
Re: /proc filesystem allows bypassing directory permissions on Linux
From: Pavel Machek <pavel () ucw cz>
Date: Sat, 24 Oct 2009 21:02:50 +0200
On Sat 2009-10-24 10:47:38, psz () maths usyd edu au wrote:
Dear Pavel,... can you see a way to write to that file when /proc is unmounted?While there is legitimate access to do so (after file is created and before pavel issues 'chmod 700 /tmp/my_priv'), guest to use commands: ln /tmp/my_priv/unwritable_file /tmp/hardlink-to-object and then use that instead of /proc/self/fd/3, should work same as original "attack" (and am curious whether 'link counts' shown by 'ls -l /tmp/my_priv/unwritable_file' are 1 or 2 in each case).
You are welcome to try it. link count is 2 for "ln" case and 1 for "/proc" case -- and that's exactly the problem. "pavel" has no chance to know that backdoor exists. Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
Current thread:
- Re: /proc filesystem allows bypassing directory permissions on Linux, (continued)
- Re: /proc filesystem allows bypassing directory permissions on Linux Jim Paris (Oct 30)
- Re: /proc filesystem allows bypassing directory permissions on Linux Marco Verschuur (Oct 30)
- Re: /proc filesystem allows bypassing directory permissions on Linux Pavel Machek (Oct 30)
- Re: /proc filesystem allows bypassing directory permissions on Linux Marco Verschuur (Oct 30)
- Message not available
- Re: /proc filesystem allows bypassing directory permissions on Linux Pavel Machek (Oct 30)
- Re: /proc filesystem allows bypassing directory permissions on Linux psz (Oct 30)
- Re: /proc filesystem allows bypassing directory permissions on Linux Jim Paris (Oct 30)
- Re: /proc filesystem allows bypassing directory permissions on Linux Marco Verschuur (Oct 30)
- Re: /proc filesystem allows bypassing directory permissions on Linux Joel Maslak (Oct 26)
- Re: /proc filesystem allows bypassing directory permissions on Linux psz (Oct 26)
- Re: /proc filesystem allows bypassing directory permissions on Linux Pavel Machek (Oct 26)
- Re: /proc filesystem allows bypassing directory permissions on Linux psz (Oct 26)
- Re: /proc filesystem allows bypassing directory permissions on Linux Dan Yefimov (Oct 26)
- Re: /proc filesystem allows bypassing directory permissions on Linux Pavel Machek (Oct 26)
- Re: /proc filesystem allows bypassing directory permissions on Linux psz (Oct 26)
- Re: /proc filesystem allows bypassing directory permissions on Linux Dan Yefimov (Oct 26)
- Re: /proc filesystem allows bypassing directory permissions on Linux Pavel Machek (Oct 26)
- Re: /proc filesystem allows bypassing directory permissions on Linux Dan Yefimov (Oct 26)
- Re: /proc filesystem allows bypassing directory permissions on Linux Pavel Machek (Oct 26)
- Re: /proc filesystem allows bypassing directory permissions on Linux Dan Yefimov (Oct 26)
- Re: /proc filesystem allows bypassing directory permissions on Linux Pavel Machek (Oct 26)