FreeBSD Security Advisories
2000-Sep-20 14:21 UTC
FreeBSD Ports Security Advisory: FreeBSD-SA-00:46.screen [UPDATED]
-----BEGIN PGP SIGNED MESSAGE----- ============================================================================FreeBSD-SA-00:46 Security Advisory FreeBSD, Inc. Topic: screen port contains local root compromise Category: ports Module: screen Announced: 2000-09-13 Updated: 2000-09-20 Affects: Ports collection prior to the correction date. Corrected: 2000-09-01 Credits: Jouko Pynnönen <jouko@SOLUTIONS.FI> Vendor status: Updated version released FreeBSD only: NO I. Background screen is a popular application that multiplexes a physical terminal between several processes. II. Problem Description The screen port, versions 3.9.5 and before, contains a vulnerability which allows local users to gain root privileges. This is accomplished by inserting string-formatting operators into configuration parameters, which may allow arbitrary code to be executed. The screen port is not installed by default, nor is it "part of FreeBSD" as such: it is part of the FreeBSD ports collection, which contains over 3800 third-party applications in a ready-to-install format. The ports collections shipped with FreeBSD 3.5.1 and 4.1 contain this problem since it was discovered after the releases. FreeBSD makes no claim about the security of these third-party applications, although an effort is underway to provide a security audit of the most security-critical ports. III. Impact Local users can obtain root privileges. If you have not chosen to install the screen port/package, then your system is not vulnerable to this problem. IV. Workaround Remove the setuid bit on the program: execute the following command as root: chmod 555 /usr/local/bin/screen-3.9.5 Note that this should be considered a temporary measure and may affect the behaviour of the screen program. V. Solution One of the following: 1) Upgrade your entire ports collection and rebuild the screen port. NOTE: Be sure to delete the old package using pkg_delete before installing the new one! If you do not remove the old package you may still have a vulnerable setuid binary on your system. To check for old screen packages which are still installed, execute the following command: ls -d /var/db/pkg/screen-* For each returned entry, run pkg_delete on the directory name (e.g. pkg_delete screen-3.9.5). You will get warnings if more than one package is installed, but ignore them and proceed to rebuild the latest version of the screen port. 2) Deinstall the old package and install a new package dated after the correction date, obtained from: ftp://ftp.FreeBSD.org/pub/FreeBSD/ports/i386/packages-3-stable/misc/screen-3.9.8.tgz ftp://ftp.FreeBSD.org/pub/FreeBSD/ports/i386/packages-4-stable/misc/screen-3.9.8.tgz ftp://ftp.FreeBSD.org/pub/FreeBSD/ports/alpha/packages-4-stable/misc/screen-3.9.8.tgz ftp://ftp.FreeBSD.org/pub/FreeBSD/ports/i386/packages-5-current/misc/screen-3.9.8.tgz ftp://ftp.FreeBSD.org/pub/FreeBSD/ports/alpha/packages-5-current/misc/screen-3.9.8.tgz NOTE: It may be several days before updated packages are available. 3) download a new port skeleton for the screen port from: http://www.freebsd.org/ports/ and use it to rebuild the port. 4) Use the portcheckout utility to automate option (3) above. The portcheckout port is available in /usr/ports/devel/portcheckout or the package can be obtained from: ftp://ftp.FreeBSD.org/pub/FreeBSD/ports/i386/packages-3-stable/devel/portcheckout-2.0.tgz ftp://ftp.FreeBSD.org/pub/FreeBSD/ports/i386/packages-4-stable/devel/portcheckout-2.0.tgz ftp://ftp.FreeBSD.org/pub/FreeBSD/ports/alpha/packages-4-stable/devel/portcheckout-2.0.tgz ftp://ftp.FreeBSD.org/pub/FreeBSD/ports/i386/packages-5-current/devel/portcheckout-2.0.tgz ftp://ftp.FreeBSD.org/pub/FreeBSD/ports/alpha/packages-5-current/devel/portcheckout-2.0.tgz VI. Revision History v1.0 2000-09-13 Initial release v1.1 2000-09-20 Add warning statement about properly deleting the old package before rebuilding the port -----BEGIN PGP SIGNATURE----- Version: 2.6.2 iQCVAwUBOckp91UuHi5z0oilAQECagQAjaQoHD2VSikfT0Lj4V3T1V4gFOYO/10z iTV+lZUhzE5EWGCdvitxjjJyjYAt+oTDzAZoOUn7uVX33rUl11860o0wIu9NCZrh EIQVAXHK9pzhfUNE0iLpCEtmCvNsOMoIxg3RmZ0QqaP4+iw+UvyOMxFqS/BXKWyN 7V3hKDfWN18=UMEK -----END PGP SIGNATURE----- This is the moderated mailing list freebsd-announce. The list contains announcements of new FreeBSD capabilities, important events and project milestones. See also the FreeBSD Web pages at http://www.freebsd.org To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-announce" in the body of the message