-----BEGIN PGP SIGNED MESSAGE----- ============================================================================= FreeBSD-SA-01:40 Security Advisory FreeBSD, Inc. Topic: fts(3) routines contain race condition [REVISED] Category: core Module: libc Announced: 2001-06-04 Revised: 2001-08-16 Credits: Nick Cleaton Todd Miller helped to develop the patch. Affects: FreeBSD 4.3-RELEASE, 4.3-STABLE prior to the correction date. Corrected: 2001-06-01 FreeBSD only: NO 0. Revision History 2001-06-04 v1.0 Initial release 2001-08-16 v1.1 Corrected typo in recompilation instructions I. Background The standard C library (libc) contains a set of routines known as fts which allow an application to recursively traverse a filesystem. II. Problem Description The fts routines are vulnerable to a race condition when ascending a file hierarchy, which allows an attacker who has control over part of the hierarchy into which fts is descending to cause the application to ascend beyond the starting point of the file traversal, and enter other parts of the filesystem. If the fts routines are being used by an application to perform operations on the filesystem hierarchy, such as find(1) with a keyword such as -exec or -delete, or rm(1) with the -r flag, these operations can be incorrectly applied to files outside the intended hierarchy, which may result in system damage or compromise. All versions of FreeBSD prior to the correction date including 4.3-RELEASE are vulnerable to this problem. III. Impact Local users may be able to remove or modify files on the local system which are owned or writable by a user running a command that uses the FTS routines in a vulnerable way. If the system administrator has enabled the daily_clean_tmps_enable variable in /etc/periodic.conf, the find -delete command is run once per day, allowing unauthorised removal of files on the system. This option is not enabled by default. IV. Workaround None appopriate for the general vulnerability. The instance exposed by the daily_clean_tmps_enable setting can be prevented by disabling this switch in /etc/periodic.conf, if it has been enabled. V. Solution One of the following: 1) As of FreeBSD 4.3-RELEASE, we have introduced a new ``security fix CVS branch'' which contains security fixes only, which can be tracked using the standard FreeBSD tools (cvsup/CVS/etc). The branch name is ``RELENG_4_3''. Upgrade your vulnerable FreeBSD system to the RELENG_4_3 branch after the correction date. 2) Upgrade your vulnerable FreeBSD system to 4.3-STABLE after the correction dates. 3) To patch your present system: download the relevant patch from the below location, and execute the following commands as root: [FreeBSD 4.3 base system] # fetch ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/patches/SA-01:40/fts.patch # fetch ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/patches/SA-01:40/fts.patch.asc Verify the detached PGP signature using your PGP utility. # cd /usr/src/lib/libc # patch -p < /path/to/patch # make depend && make all install # cd /usr/src/lib/libc_r # make depend && make all install # cd /usr/src/bin/chmod # make depend && make all install # cd /usr/src/bin/cp # make depend && make all install # cd /usr/src/bin/ls # make depend && make all install # cd /usr/src/bin/pax # make depend && make all install # cd /usr/src/bin/rm # make depend && make all install # cd /usr/src/usr.bin/chflags # make depend && make all install # cd /usr/src/usr.bin/du # make depend && make all install # cd /usr/src/usr.bin/find # make depend && make all install # cd /usr/src/libexec/ftpd # make depend && make all install # cd /usr/src/usr.sbin/chown # make depend && make all install # cd /usr/src/usr.sbin/ckdist # make depend && make all install # cd /usr/src/usr.sbin/ctm # make depend && make all install # cd /usr/src/usr.sbin/mtree # make depend && make all install # cd /usr/src/usr.sbin/pkg_install # make depend && make all install This patch has been verified to apply to FreeBSD 4.3-RELEASE and 4.2-RELEASE; it may or may not apply to older, unsupported versions of FreeBSD. 4) An experimental upgrade package is available for adventurous users who wish to provide testing and feedback on the binary upgrade process. This package may be installed on FreeBSD 4.3-RELEASE systems only, and is intended for use on systems for which source patching is not practical or convenient. Since this is the first binary upgrade package produced for the FreeBSD base system, it is not recommended that this be used on production systems without first being tested on a scratch machine; since the package replaces critical system files, a failed upgrade can leave a system in an unusable state. During the installation procedure, backup copies are made of the files which are replaced by the package. These backup copies will be reinstalled if the package is removed, reverting the system to a pre-patch state. # fetch ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/packages/SA-01:40/security-patch-fts-01.40.tgz # fetch ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/packages/SA-01:40/security-patch-fts-01.40.tgz.asc Verify the detached PGP signature using your PGP utility. Bring the system down to single-user mode; this package should not be installed from multi-user mode. If it desired to remove the package at a later date, you should again do so from single-user mode. # shutdown now # pkg_add security-patch-fts-01.40 Follow the directions given after the installation of the package to complete the system upgrade. To bring the system back up to multi-user mode, type the following command: # exit -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.0.6 (FreeBSD) Comment: For info see http://www.gnupg.org iQCVAwUBO3y5tFUuHi5z0oilAQF6PwP/fFXgo2bL/IlDleuWCQsVB/C1By8QPL5J Z0Hi4yl28Z8hEGRTI8qK2UXIliskU+ixlD0j9N6yxJDe17KIY/4w3gGJGsux3J7j TSHXZOfsX0CE61Jssm9kUpOzilwJBOhRvii0BSso7njtVIQpFpWBgIMne+lNluFe S7SZsk6sqgg= =K6yG -----END PGP SIGNATURE-----