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security advisorymoderate severityinformation disclosure

SUSE: 2005-062 Moderate: Permissions Information Disclosure Issue

SUSE LINUX ships with three pre defined sets of permissions, 'easy', SUSE LINUX ships with three pre defined sets of permissions, 'easy', 'secure' and 'paranoid'. The chkstat program contained in the 'secure' and 'paranoid'. The chkstat program contained in the permissions package is used to set those permissions to the chosen level. Level 'easy' which is the default allows some world writeable di [More...]. -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 ______________________________________________________________________________ SUSE Security Announcement Package: permissions Announcement ID: SUSE-SA:2005:062 Date: Mon, 24 Oct 2005 08:00:00 +0000 Affected Products: SUSE LINUX 10.0 SUSE LINUX 9.3 SUSE LINUX 9.2 SUSE LINUX 9.1 SuSE Linux 9.0 SuSE Linux Desktop 1.0 SuSE Linux Enterprise Server 8 SUSE SLES 9 UnitedLinux 1.0 Vulnerability Type: information disclosure Severity (1-10): 4 SUSE Default Package: yes Cross-References: - Content of This Advisory: 1) Security Vulnerability Resolved: information disclosure via permissions package Problem Description 2) Solution or Work-Around 3) Special Instructions and Notes 4) Package Location and Checksums 5) Pending Vulnerabilities, Solutions, and Work-Arounds: - See SUSE Security Summary Report 6) Authenticity Verification and Additional Information ______________________________________________________________________________ 1) Problem Description and Brief Discussion SUSE LINUX ships with three pre defined sets of permissions, 'easy', 'secure' and 'paranoid'. Thechkstat program contained in the permissions package is used to set those permissions to the chosen level. Level 'easy' which is the default allows some world writeable directories. /usr/src/packages/RPMS and subdirectories is among them. To prevent users from playing tricks in there e.g. linking to /etc/shadow chkstat doesn't touch symlinks or files with an hardlink count != 1. Stefan Nordhausen discovered a way to trick this check. To gain access to e.g. /etc/shadow a malicious user has to place a hardlink to that file at a place that is modified by chkstat. chkstat will not touch the file because it has a hardlink count of two. However, if the administrator modifies the user database the original /etc/shadow gets deleted and replaced by a new one. That means the hardlink count of the file created by the malicious user drops to one. At this point chkstat will modify the file's permissions so anyone can read it. So it's technically impossible for chkstat to modify permissions of files in world writeable directories in a secure way. One such world writeable directoy in level 'easy' is /usr/src/packages/RPMS. Only subdirectories need to be adjusted in this case. Since normal users cannot create hard links to directories the problem can be solved by telling chkstat to not accept regular files. Another problematic directory is /var/games. Only members of group 'games' may write to it but it's likely that games with setgid 'games' are exploitable to allow user to gain group 'games' membership. The updated permissions package now tells chkstat when to only accept directories and no longer touches anything below /var/games to solve the described problems. On SUSE Linux 9.0 xmcd contained world writeable directories that suffered from the same problems. Updated xmcd packages for SUSE Linux 9.0 are therefore provided as well. We like to thank Stefan Nordhausen for pointing out the problems. 2) Solution orWork-Around In permissions level 'secure' no games are setgid 'games' and /usr/src/packages is not world writeable. You are safe if you switched to that level before any potentially malicious users could log in. 3) Special Instructions and Notes None 4) Package Location and Checksums The preferred method for installing security updates is to use the YaST Online Update (YOU) tool. YOU detects which updates are required and automatically performs the necessary steps to verify and install them. Alternatively, download the update packages for your distribution manually and verify their integrity by the methods listed in Section 6 of this announcement. Then install the packages using the command rpm -Fhv to apply the update, replacing with the filename of the downloaded RPM package. x86 Platform: SUSE LINUX 10.0: 5f634cb4cd45ad3283e6055c3794ecff 7e9beef0e8df0ba419ff64ac96ad57e1 SUSE LINUX 9.3: 216afa8469276198015e5fff177580d2 SUSE LINUX 9.2: 3d61d27c7bf81889a321972ac12dcaab SUSE LINUX 9.1: 72d9a0b5b0b750fb656aa54eb7c6ebdd SuSE Linux 9.0: cf8c022048e93fc6d159913ad7824e6a f3e82cf342c45ab46fca16c98587b22d Power PC Platform: SUSE LINUX 10.0: f0077c15af6a95edbd7aa25055668967 7f6552f5450b98821912c8703c580b38 x86-64 Platform: SUSE LINUX 10.0: 214b7d7fc6dfdac3e07eff2ad4abf0e9 7b15cb94762ae6bc1cd7e441a08c39b4 SUSE LINUX 9.3: 0d11d64965eee2cefeb56edfe258fee4 SUSE LINUX 9.2: 4f2373ed4a93e3974b919e595a9490b7 SUSE LINUX 9.1: 3ca12f4aae9b7a1b484e6a0e4f8f658d SuSE Linux 9.0: 853503b8868c1d2a34d05aaf6824cf83 fd95ac5dd3980af5308abe7062849149 Sources: SUSE LINUX 10.0: 1784328035be5507b20737a2edfce8d8 0fc7ffe7a9688f04c916c50709db08da SUSE LINUX 9.3: 0a856cadf3b65db9434f20203413aba3 SUSE LINUX 9.2: 57c3240513c9861634e79547df4f8cf0 SUSE LINUX 9.1: b47b5e76f759227d325a33dbbcb5ae96 f98fa35639b7d118e6aed1ecb99c4cbb SuSE Linux 9.0: 8fa2759f6d2012aee4571e5830ea26eb 44f64e89f871fd07bd6291d88277b327 48857a183ff120bc39ebb280eaca8764 9e961bdfaf2c935857eb86bd64b74c83 Our maintenance customers are notified individually. The packages are offered for installation from the maintenance web: https://www.suse.com:443/ https://www.suse.com:443/ ______________________________________________________________________________ 5) Pending Vulnerabilities, Solutions, and Work-Arounds: - See SUSE Security Summary Report ______________________________________________________________________________ 6) Authenticity Verification and Additional Information - Announcement authenticity verification: SUSE security announcements are published via mailing lists and on Web sites. The authenticity and integrity of a SUSE security announcement is guaranteed by a cryptographic signature in each announcement. All SUSE security announcements are published with a valid signature. To verify the signature of the announcement, save it as text into a file and run the command gpg --verify replacing with the name of the file where you saved the announcement. The output for a valid signature looks like: gpg: Signature made using RSA key ID 3D25D3D9 gpg: Good signature from "SuSE Security Team " where is replaced by the date the document was signed. If the security team's key is not contained in your key ring, you can import it from the first installation CD. To import the key, use the command gpg --import gpg-pubkey-3d25d3d9-36e12d04.asc - Package authenticity verification: SUSE update packages are available on many mirror FTPservers all over the world. While this service is considered valuable and important to the free and open source software community, the authenticity and the integrity of a package needs to be verified to ensure that it has not been tampered with. 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) Using the internal gpg signatures of the rpm package 2) MD5 checksums as provided in this announcement 1) The internal rpm package signatures provide an easy way to verify the authenticity of an RPM package. Use the command rpm -v --checksig to verify the signature of the package, replacing with the filename of the RPM package downloaded. The package is unmodified if it contains a valid signature from This email address is being protected from spambots. You need JavaScript enabled to view it. with the key ID 9C800ACA. This key is automatically imported into the RPM database (on RPMv4-based distributions) and the gpg key ring of 'root' during installation. You can also find it on the first installation CD and at the end of this announcement. 2) If you need an alternative means of verification, use the md5sum command to verify the authenticity of the packages. Execute the command md5sum 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 SUSE security announcement. Because the announcement containing the checksums is cryptographically signed (by This email address is being protected from spambots. You need JavaScript enabled to view it.), the checksums show proof of the authenticity of the package if the signature of the announcement is valid. Note that the md5 sums published in the SUSE Security Announcements are valid for the respective packages only. Newer versions of these packages cannot be verified. - SUSE runs two security mailing lists to which any interested party may subscribe: This email address is being protected from spambots. You need JavaScript enabled to view it. - General Linux and SUSE security discussion. All SUSE security announcements are sent to this list. To subscribe, send an e-mail to . This email address is being protected from spambots. You need JavaScript enabled to view it. - SUSE's announce-only mailing list. Only SUSE's security announcements are sent to this list. To subscribe, send an e-mail to . For general information or the frequently asked questions (FAQ), send mail to or . ==================================================================== SUSE's security contact is or . The public key is listed below. ==================================================================== . Fedora Linux enhances security framework to address vulnerabilities discovered in several releases. Keep your system safe!. SUSE Permissions Update, Info Disclosure, Security Advisory. . LinuxSecurity.com Team

Oct 24, 2005 SuSE