-----BEGIN PGP SIGNED MESSAGE----- ______________________________________________________________________________ SuSE Security Announcement Package: screen Announcement-ID: SuSE-SA:2001:030 Date: Wednesday, September 5 2001 18:00 MEST Affected SuSE versions: (6.0, 6.1, 6.2) 6.3, 6.4, 7.0, 7.1, 7.2 Vulnerability Type: local root compromise Severity (1-10): 5 SuSE default package: yes Other affected systems: some systems with the screen program installed setuid root Content of this advisory: 1) security vulnerability resolved: screen problem description, discussion, solution and upgrade information 2) pending vulnerabilities, solutions, workarounds 3) standard appendix (further information) ______________________________________________________________________________ 1) problem description, brief discussion, solution, upgrade information screen is a terminal multiplexer program that allows reattaching to a detached session as well as multi-attached (shared) sessions. The screen package allows a local attacker to obtain root privileges if the /usr/bin/screen command is installed setuid root and if a directory below /tmp/screens/ exists. The screen program needs root permissions from the setuid-root bit for two reasons: multi-attached sessions are only possible with root privileges, and writing terminal allocation information to /var/run/utmp (the who(1) and finger(1) commands). If the screen command is not running with special privileges, all functionality except these two features will continue to work, but the local root compromise will not be possible. In order to provide the features mentioned, the screen package used to be installed setuid-root in SuSE Linux distributions. The update packages that we provide for the supported distributions 6.3, 6.4, 7.0, 7.1 and 7.2 eliminate the error in the source code. In addition to that, the rpm package does not contain the setuid-bit on the screen program any more. If there is any more security-related bug in the screen package or libraries that it is linked against to be found in the future, these errors will not open local security holes any more. Users of the screen package who need the multi-attach feature must enable it again by adding the setuid-bit to the /usr/bin/screen file. Please note that you should reflect the changes to permissions in the files /etc/permissions*. If unsure, use the setting "secure local" for the variable PERMISSION_SECURITY in /etc/rc.config and execute "SuSEconfig" as root. Alternatively, change the settings for the screen program in /etc/permissions* and run "chkstat -set <file>" for each file that you need. Use the command "rpm -qlv screen | grep /usr/bin" to find out which files to add to the permissions file (/usr/bin/screen is a symlink). The authors of screen have released the new version screen-3.9.10 that fixes the multi-attach-error, and some other uncritical bug. Our update packages contain the necessary patches applied to the version as shipped with the original distribution. We thank Christian Hürgemann <Bzrker@t-online.de> for reporting this error on Monday, 3 Sep 2001. Please download the update package for your distribution and verify its integrity by the methods listed in section 3) of this announcement. Then, install the package using the command "rpm -Uhv file.rpm" to apply the update. i386 Intel Platform: SuSE-7.2 ftp://ftp.suse.com/pub/suse/i386/update/7.2/ap1/screen-3.9.8-115.i386.rpm e85453f50170ecdabe97dd2b33b51e4a source rpm: ftp://ftp.suse.com/pub/suse/i386/update/7.2/zq1/screen-3.9.8-115.src.rpm 74ac0119ec42f7c5ad4405a7f1c00f6a SuSE-7.1 ftp://ftp.suse.com/pub/suse/i386/update/7.1/ap1/screen-3.9.8-115.i386.rpm fb0a3ba99db246c1f08e3814557858ae source rpm: ftp://ftp.suse.com/pub/suse/i386/update/7.1/zq1/screen-3.9.8-115.src.rpm 5edb0caa388be9f1ddc2cd4d0a4f3a54 SuSE-7.0 ftp://ftp.suse.com/pub/suse/i386/update/7.0/ap1/screen-3.9.8-115.i386.rpm b7bfa891b49db29093f6ab1830d84838 source rpm: ftp://ftp.suse.com/pub/suse/i386/update/7.0/zq1/screen-3.9.8-115.src.rpm fb1e3bf070adec10296a59f2d1231c8c SuSE-6.4 ftp://ftp.suse.com/pub/suse/i386/update/6.4/ap1/screen-3.9.8-115.i386.rpm a889c9090b0a64eb57a407ee00444491 source rpm: ftp://ftp.suse.com/pub/suse/i386/update/6.4/zq1/screen-3.9.8-115.src.rpm 29b6e24378153a4f9d2445414253759c SuSE-6.3 ftp://ftp.suse.com/pub/suse/i386/update/6.3/ap1/screen-3.9.8-115.i386.rpm 5a47bdc2407890d9a940c710d4806383 source rpm: ftp://ftp.suse.com/pub/suse/i386/update/6.3/zq1/screen-3.9.8-115.src.rpm f3bace3114cfcb9b1b6e798ea8b93b34 Sparc Platform: SuSE-7.1 ftp://ftp.suse.com/pub/suse/sparc/update/7.1/ap1/screen-3.9.8-61.sparc.rpm 3bfe4ac28d54ff2cab6582b2d09f3b75 source rpm: ftp://ftp.suse.com/pub/suse/sparc/update/7.1/zq1/screen-3.9.8-61.src.rpm 17da9f63ec2b0d48b3593dacfe341a7b SuSE-7.0 ftp://ftp.suse.com/pub/suse/sparc/update/7.0/ap1/screen-3.9.8-62.sparc.rpm 13037ae193ebd81b92ce1d94d2409421 source rpm: ftp://ftp.suse.com/pub/suse/sparc/update/7.0/zq1/screen-3.9.8-62.src.rpm c542f1c51a701ad5dd06d9f9f3701cfb AXP Alpha Platform: SuSE-7.1 ftp://ftp.suse.com/pub/suse/axp/update/7.1/ap1/screen-3.9.8-71.alpha.rpm c5239b5ca727a4f7d54589399b62a5c5 source rpm: ftp://ftp.suse.com/pub/suse/axp/update/7.1/zq1/screen-3.9.8-71.src.rpm 4c389bca8641e3c081e992e82bc5065d SuSE-7.0 ftp://ftp.suse.com/pub/suse/axp/update/7.0/ap1/screen-3.9.8-71.alpha.rpm 9f84734233284fc9f7be494c37a4f857 source rpm: ftp://ftp.suse.com/pub/suse/axp/update/7.0/zq1/screen-3.9.8-71.src.rpm 31920bb58b696739100e75ce363ade6d SuSE-6.4 ftp://ftp.suse.com/pub/suse/axp/update/6.4/ap1/screen-3.9.8-71.alpha.rpm a7f64468ecc5be193795ea3a530d3ead source rpm: ftp://ftp.suse.com/pub/suse/axp/update/6.4/zq1/screen-3.9.8-71.src.rpm dae933854ae9a7efd3e80e09641b9963 SuSE-6.3 ftp://ftp.suse.com/pub/suse/axp/update/6.3/ap1/screen-3.9.8-71.alpha.rpm f66d9c18a27cd7915d5134528b47c342 source rpm: ftp://ftp.suse.com/pub/suse/axp/update/6.3/zq1/screen-3.9.8-71.src.rpm 13157d46457be72fd7684ca0cbe6c49b PPC Power PC Platform: SuSE-7.1 ftp://ftp.suse.com/pub/suse/ppc/update/7.1/ap1/screen-3.9.8-52.ppc.rpm 090e4781fb4949697fb08f755a0ae12d source rpm: ftp://ftp.suse.com/pub/suse/ppc/update/7.1/zq1/screen-3.9.8-52.src.rpm ce19f08412c6517798690fa7d99ed690 SuSE-7.0 ftp://ftp.suse.com/pub/suse/ppc/update/7.0/ap1/screen-3.9.8-52.ppc.rpm e37b478c4ce85febc13785b4a48c68c0 source rpm: ftp://ftp.suse.com/pub/suse/ppc/update/7.0/zq1/screen-3.9.8-52.src.rpm 0594837833e05e430c52421745f1abfa SuSE-6.4 ftp://ftp.suse.com/pub/suse/ppc/update/6.4/ap1/screen-3.9.8-52.ppc.rpm 53cb3d0fdf964a4013b6aed326d77c9e source rpm: ftp://ftp.suse.com/pub/suse/ppc/update/6.4/zq1/screen-3.9.8-52.src.rpm 89300f304c709a10975f5906bedd1529 ______________________________________________________________________________ 2) Pending vulnerabilities in SuSE Distributions and Workarounds: - sendmail SuSE Security announcement SuSE-SA:2001:028 (sendmail) offers a sendmail update package for the 7.0-i386 distribution that has a lower version number than the package in the tree for ftp installation on ftp.suse.com. If your update rpm command fails with a complaint that the version installed is newer than the one you wish to be installed, then please use the "--oldpackage" commandline option to rpm: "rpm --oldpackage -Uhv sendmail-*.rpm". We are correcting the problem as soon as possible. The new package will be named sendmail-8.11.0-10.i386.rpm and should appear on the ftp server within the next 11 hours. The *-10 package is technically identical to the *-5 package that is currently available on our ftp server. ______________________________________________________________________________ 3) standard appendix: authenticity verification, additional information - Package authenticity verification: SuSE update packages are available on many mirror ftp servers all over the world. While this service is being considered valuable and important to the free and open source software community, many users wish to be sure about the origin of the package and its content before installing the package. There are two verification methods that can be used independently from each other to prove the authenticity of a downloaded file or rpm package: 1) md5sums as provided in the (cryptographically signed) announcement. 2) using the internal gpg signatures of the rpm package. 1) execute the command md5sum <name-of-the-file.rpm> after you downloaded the file from a SuSE ftp server or its mirrors. Then, compare the resulting md5sum with the one that is listed in the announcement. Since the announcement containing the checksums is cryptographically signed (usually using the key security@suse.de), the checksums show proof of the authenticity of the package. We disrecommend to subscribe to security lists which cause the email message containing the announcement to be modified so that the signature does not match after transport through the mailing list software. Downsides: You must be able to verify the authenticity of the announcement in the first place. If RPM packages are being rebuilt and a new version of a package is published on the ftp server, all md5 sums for the files are useless. 2) rpm package signatures provide an easy way to verify the authenticity of an rpm package. Use the command rpm -v --checksig <file.rpm> to verify the signature of the package, where <file.rpm> is the filename of the rpm package that you have downloaded. Of course, package authenticity verification can only target an uninstalled rpm package file. Prerequisites: a) gpg is installed b) The package is signed using a certain key. The public part of this key must be installed by the gpg program in the directory ~/.gnupg/ under the user's home directory who performs the signature verification (usually root). You can import the key that is used by SuSE in rpm packages for SuSE Linux by saving this announcement to a file ("announcement.txt") and running the command (do "su -" to be root): gpg --batch; gpg < announcement.txt | gpg --import SuSE Linux distributions version 7.1 and thereafter install the key "build@suse.de" upon installation or upgrade, provided that the package gpg is installed. The file containing the public key is placed at the toplevel directory of the first CD (pubring.gpg) and at ftp://ftp.suse.com/pub/suse/pubring.gpg-build.suse.de . - SuSE runs two security mailing lists to which any interested party may subscribe: suse-security@suse.com - general/linux/SuSE security discussion. All SuSE security announcements are sent to this list. To subscribe, send an email to <suse-security-subscribe@suse.com>. suse-security-announce@suse.com - SuSE's announce-only mailing list. Only SuSE's security annoucements are sent to this list. To subscribe, send an email to <suse-security-announce-subscribe@suse.com>. For general information or the frequently asked questions (faq) send mail to: <suse-security-info@suse.com> or <suse-security-faq@suse.com> respectively. =================================================== SuSE's security contact is <security@suse.com>. The <security@suse.com> public key is listed below. =================================================== ______________________________________________________________________________ The information in this advisory may be distributed or reproduced, provided that the advisory is not modified in any way. In particular, it is desired that the cleartext signature shows proof of the authenticity of the text. SuSE GmbH makes no warranties of any kind whatsoever with respect to the information contained in this security advisory. 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