===================================================================== CERT-Renater Note d'Information No. 2005/VULN239 _____________________________________________________________________ DATE : 06/04/2005 HARDWARE PLATFORM(S) : IBM. OPERATING SYSTEM(S) : AIX 5.3. ====================================================================== IBM SECURITY ADVISORY First Issued: Thu Mar 24 16:29:18 CST 2005 =========================================================================== VULNERABILITY SUMMARY VULNERABILITY: A remote user may gain root access to a system configured as a NIS client. PLATFORMS: AIX 5.3. SOLUTION: Apply the workaround, efix or APAR as described below. THREAT: A remote user may gain root access to a system configured as a NIS client. CERT VU Number: N/A CVE Number: N/A =========================================================================== DETAILED INFORMATION I. Description =============== A vulnerability was discovered that can be exploited by a remote user to gain root privileges. Note that it is also possible for a local attacker to exploit this vulnerability. This vulnerability only affects AIX 5.3 when configured as a NIS client. Versions of AIX prior to AIX 5.3 are not affected by this issue. Please note that this vulnerability is a different issue than the NIS vulnerability announced on January 31st, 2005. All fixes described in this advisory will also address the NIS vulnerability announced on January 31st, 2005. II. Impact ========== A remote attacker may gain root access to a system configured as a NIS client. III. Solutions =============== A. Official Fix IBM provides the following fixes: APAR number for AIX 5.3.0: IY68825 (available approx. 04/15/05) NOTE: Affected customers are urged to upgrade to 5.3.0 at the latest maintenance level. B. Emergency Fix Efixes are available for AIX 5.3.0. The efixes can be downloaded via ftp from: ftp://aix.software.ibm.com/aix/efixes/security/nis_2_efix.tar.Z nis_2_efix.tar.Z is a compressed tarball containing this advisory, two efix packages for 5.3.0 and a cleartext PGP signature for each efix package. The efix package named IY68825_00.050323.epkg.Z is for AIX 5.3.0 with no maintenance level applied. This efix has the filesets bos.rte.libc.5.3.0.5 and bos.rte.security.5.3.0.5 as prerequisites and will not install unless these prerequisites are installed on the system. The efix package named IY68825_01.050323.epkg.Z is for AIX 5.3.0 with maintenance level one applied. This efix has the filesets bos.rte.libc.5.3.0.11 and bos.rte.security.5.3.0.10 as prerequisites and will not install unless these prerequisites are installed on the system. Verify you have retrieved the efixes intact: - - --------------------------------------------- The checksums below were generated using the "sum" and "md5sum" commands and are as follows: Filename sum md5 ====================================================================== IY68825_00.050323.epkg.Z 64933 3562 81786373cc19db9c62f51c995179e732 IY68825_01.050323.epkg.Z 54661 3627 3a9ba60ddd561b10a4f88a12b513692c These sums should match exactly. The PGP signatures in the compressed tarball and on this advisory can also be used to verify the integrity of the various files they correspond to. If the sums or signatures cannot be confirmed, double check the command results and the download site address. If those are OK, contact IBM AIX Security at security-alert@austin.ibm.com and describe the discrepancy. IMPORTANT: If possible, it is recommended that a mksysb backup of the system is created. Verify it is both bootable, and readable before proceeding. These efixes have not been fully regression tested; thus, IBM does not warrant the fully correct functioning of the efix. Customers install the efix and operate the modified version of AIX at their own risk. Efix Installation Instructions: - - -------------------------------- The efix package for AIX 5.3.0 with no maintenance level is named IY68825_00.050323.epkg.Z and the efix package for AIX 5.3.0 with maintenance level one installed is named IY68825_01.050323.epkg.Z. These packages use the new Emergency Fix Management Solution to install and manage efixes. More information can be found at: http://techsupport.services.ibm.com/server/aix.efixmgmt To preview an epkg efix installation execute the following command: # emgr -e epkg_name -p # where epkg_name is the name of the # efix package being previewed. To install an epkg efix package, execute the following command: # emgr -e epkg_name -X # where epkg_name is the name of the # efix package being installed. It is strongly recommended that this efix be mount installed before doing a regular install. A mount install will mount the patched binaries over existing system binaries. If any issues arise, the efix can be unmounted or the system can be rebooted to revert of the original system files. The mount an epkg efix package, execute the following command: # emgr -e epkg_name -mX # where epkg_name is the name of the # efix package being installed. The "X" flag will expand any filesystems if required. C. Workaround This workaround is only valid if AIX is configured to use NIS. The /etc/passwd system file contains entries for NIS users. These entries begin with the "+" character. /etc/passwd may also contain a global escape sequence ("+::0:0:::"). To remove this vulnerability, ensure that no entry in /etc/passwd that begins with the "+" character specifies a gecos, home directory or shell. These are the fifth, sixth and seventh fields respectively. Additionally, to protect against the previous NIS vulnerability, the global escape sequence should be changed to "+:". Note that these change can only be done by the root user. IV. Obtaining Fixes =================== AIX Version 5 APARs can be downloaded from: http://www-1.ibm.com/servers/eserver/support/pseries/aixfixes.html Security related Emergency Fixes can be downloaded from: ftp://aix.software.ibm.com/aix/efixes/security V. Contact Information ======================== If you would like to receive AIX Security Advisories via email, please visit: https://techsupport.services.ibm.com/server/pseries.subscriptionSvcs Comments regarding the content of this announcement can be directed to: security-alert@austin.ibm.com To request the PGP public key that can be used to communicate securely with the AIX Security Team send email to security-alert@austin.ibm.com with a subject of "get key". The key can also be downloaded from a PGP Public Key Server. The key id is 0x9391C1F2. Please contact your local IBM AIX support center for any assistance. eServer is a trademark of International Business Machines Corporation. IBM, AIX and pSeries are registered trademarks of International Business Machines Corporation. All other trademarks are property of their respective holders. ====================================================================== ========================================================= Les serveurs de référence du CERT-Renater http://www.urec.fr/securite http://www.cru.fr/securite http://www.renater.fr ========================================================= + CERT-RENATER | tel : 01-53-94-20-44 + + 151 bd de l'Hopital | fax : 01-53-94-20-41 + + 75013 Paris | email: certsvp@renater.fr + =========================================================