8125150 2002-03-11 00:21 +0100 /98 rader/ Wojciech Purczynski <cliph@isec.pl>
Sänt av: joel@lysator.liu.se
Importerad: 2002-03-11 20:40 av Brevbäraren
Extern mottagare: bugtraq@securityfocus.com
Extern kopiemottagare: security@isec.pl
Externa svar till: security@isec.pl
Mottagare: Bugtraq (import) <21346>
Ärende: GNU fileutils - recursive directory removal race condition
------------------------------------------------------------
From: Wojciech Purczynski <cliph@isec.pl>
To: bugtraq@securityfocus.com
Cc: security@isec.pl
Message-ID: <Pine.LNX.4.44.0203110015420.5212-100000@isec.pl>
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Name: fileutils
Version: 4.1 stable and 4.1.6 development version
Homepage: http://www.gnu.org/software/fileutils/fileutils.html
Author: Wojciech Purczynski <cliph@isec.pl>
Date: March 10, 2002
Issue:
======
Race condition in various utilities from fileutils GNU package may
cause root user to delete the whole filesystem.
Description:
============
The GNU File Utilities are the basic file-manipulation utilities of
the GNU operating system.
Details:
========
An insecure chdir("..") syscall is done after removing content of a
subdirectory in order to get back to the upper directory during
recursive removal of directory tree.
Example of 'rm -fr /tmp/a' removing '/tmp/a/b/c' directory tree:
(strace output simplified for better readability)
chdir("/tmp/a") = 0
chdir("b") = 0
chdir("c") = 0
chdir("..") = 0
rmdir("c") = 0
chdir("..") = 0
rmdir("b") = 0
fchdir(3) = 0
rmdir("/tmp/a") = 0
After current directory is changed to /tmp/a/b/c a race condition
occurs. If we then move /tmp/a/b/c directory to the /tmp/c two
subsequent chdir("..") syscalls will move to the root directory / and
rm will start removing files from the whole file systems if it has
enough privileges (i.e. if called by root user).
Timeframe of this race condition depends on how complicated directory
structure is.
The same issue affects also mv utility when source and destination
directory lie on different filesystems and they are removed after
creating copy on destination.
Impact:
=======
Unprivileged users may launch daemon program that will detect the
removal operation of user's directories and exploit race condition
leading to Denial of Service.
Fix:
====
On March 7, 2002 we have contacted with developers of GNU fileutils
package. On March 9, 2002 a patch fixing this vulnerability has been
released for the latest 4.1.6 development version:
http://mail.gnu.org/pipermail/bug-fileutils/2002-March/002440.html
- --
Wojciech Purczynski
iSEC Security Research
http://isec.pl/
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(8125150) /Wojciech Purczynski <cliph@isec.pl>/(Ombruten)