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-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 =========================================================================== AUSCERT External Security Bulletin Redistribution ESB-2005.0506 -- IBM SECURITY ADVISORY Denial of service vulnerability in ftpd 8 July 2005 =========================================================================== AusCERT Security Bulletin Summary --------------------------------- Product: ftpd Publisher: IBM Operating System: AIX 5.3 AIX 5.2 AIX 5.1 Impact: Denial of Service Access: Remote/Unauthenticated - --------------------------BEGIN INCLUDED TEXT-------------------- - -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 IBM SECURITY ADVISORY First Issued: Wed Jul 6 08:38:14 CDT 2005 ========================================================================= VULNERABILITY SUMMARY VULNERABILITY: A denial of service vulnerability in ftpd PLATFORMS: AIX 5.1, 5.2 and 5.3. SOLUTION: Apply the workaround, interim fix or APARs as described below. THREAT: A remote user may cause performance degradation or a denial of service. CERT VU Number: VU#118125 CVE Number: N/A ========================================================================= DETAILED INFORMATION I. Description =============== The ftpd daemon provides the server function for the FTP protocol which allows files to be transfered between two hosts. A vulnerability has been found in ftpd which allows a remote user to cause a denial of service by using all available ephemeral ports. This in turn will cause ftpd to allocate an amount of memory for sockets which is disproportionate to what it typically uses. Of these two issues, using all available ephemeral ports and using more memory for sockets, the former poses a greater threat because those ports will not be available to be used for other purposes. This issue can be exploited by any user which can authenticate with ftpd. If the system is configured to use anonymous ftp, the anonymous ftp user can also exploit this vulnerability. ftpd ships as part of the bos.net.tcp.client fileset. To determine if this fileset is installed, execute the following command: # lslpp -L bos.net.tcp.client If the fileset is installed it will be listed along with its version information, state, type and a description. II. Impact ========== A remote user may cause a denial of service or performance degradation. III. Solutions =============== A. Official Fix IBM provides the following fixes: APAR number for AIX 5.1.0: IY73498 (available approx. 09/07/05) APAR number for AIX 5.2.0: IY72942 (available approx. 09/05/05) APAR number for AIX 5.3.0: IY73497 (available approx. 09/05/05) NOTE: Affected customers are urged to upgrade to 5.1.0, 5.2.0 or 5.3.0 at the latest maintenance level. B. Interim Fix Interim fixes are available for AIX 5.1.0, 5.2.0 and 5.3.0. The ifixes can be downloaded via ftp from: ftp://aix.software.ibm.com/aix/efixes/security/ftpd_ifix.tar.Z ftpd_ifix.tar.Z is a compressed tarball containing this advisory, three ifix packages and cleartext PGP signatures for each package. Verify you have retrieved the ifixes intact: - - - -------------------------------------------- The checksums below were generated using the "sum" and "md5sum" commands and are as follows: Filename sum md5 ====================================================================== IY73498_08.050701.epkg.Z 47978 94 0c92b7aae0c12b5779240d2a4dceeb26 IY72942_04.050701.epkg.Z 46458 104 c2cbf1618dad82ff621d5a28e2b1ff67 IY72942_05.050701.epkg.Z 37293 104 8482fcac5b46a191954ed163f9ed811f IY72942_06.050701.epkg.Z 36063 104 6c9951a0fa5de3bc87179949c550669c IY73497_01.050701.epkg.Z 51428 110 75f9ed3994ff69502ce552f2023f0249 IY73497_02.050701.epkg.Z 39327 110 e1872c5e87244e3b723ae58549adba9f 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 ifixes have not been fully regression tested; thus, IBM does not warrant the fully correct functioning of the ifix. Customers install the ifix and operate the modified version of AIX at their own risk. Interim Fix Installation Instructions: - - - -------------------------------------- These packages use the new Interim Fix Management Solution to install and manage ifixes. More information can be found at: http://techsupport.services.ibm.com/server/aix.efixmgmt To preview an epkg ifix installation execute the following command: # emgr -e ipkg_name -p # where ipkg_name is the name of the # ifix package being previewed. To install an epkg ifix package, execute the following command: # emgr -e ipkg_name -X # where ipkg_name is the name of the # ifix package being installed. The "X" flag will expand any filesystems if required. Before the ifix is installed, ftpd should be stopped and once the ifix is installed, it should be started again. By default the following command can be used to stop ftpd: # stopsrc -t ftp # note that this will terminate # current ftp connections. The following command can be used to start ftpd: # startsrc -t ftp C. Workaround There are several steps which can be taken to mitigate the risk posed by this vulnerability: 1. Turn ftpd off if it is not needed. 2. Do not allow anonymous FTP. A user with a valid username and password will still be able to exploit these issues but anonymous FTP users will not be able to. 3. Set the system wid network option "sockthresh" such that it will not consume a substantial amount of system memory. The appropriate value depends on the system in question. 4. Use the system wide network options "tcp_ephemeral_low" and "tcp_ephemeral_high" to specify a range of ephemeral ports. This will limit the range of ephemeral ports for the entire system. While this will not prevent a ftpd from using all available ephemeral ports, it will limit the amount of system resources that ephemeral ports can consume. IV. Obtaining Fixes =================== AIX Version 5 APARs can be downloaded from: http://www-1.ibm.com/servers/eserver/support/pseries/aixfixes.html Security related Interim 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. - -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.1 (GNU/Linux) iD8DBQFCy+g/xwSSvpORwfIRAgi1AJ9Rgv4AnmVMhc9a/8hJJwByZke3BwCdG3O3 Vpig/7q6e2ivwPAMfwADUxA= =RjMX - -----END PGP SIGNATURE----- - --------------------------END INCLUDED TEXT-------------------- You have received this e-mail bulletin as a result of your organisation's registration with AusCERT. The mailing list you are subscribed to is maintained within your organisation, so if you do not wish to continue receiving these bulletins you should contact your local IT manager. If you do not know who that is, please send an email to auscert@auscert.org.au and we will forward your request to the appropriate person. NOTE: Third Party Rights This security bulletin is provided as a service to AusCERT's members. As AusCERT did not write the document quoted above, AusCERT has had no control over its content. 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Previous advisories and external security bulletins can be retrieved from: http://www.auscert.org.au/render.html?cid=1980 If you believe that your computer system has been compromised or attacked in any way, we encourage you to let us know by completing the secure National IT Incident Reporting Form at: http://www.auscert.org.au/render.html?it=3192 =========================================================================== Australian Computer Emergency Response Team The University of Queensland Brisbane Qld 4072 Internet Email: auscert@auscert.org.au Facsimile: (07) 3365 7031 Telephone: (07) 3365 4417 (International: +61 7 3365 4417) AusCERT personnel answer during Queensland business hours which are GMT+10:00 (AEST). On call after hours for member emergencies only. =========================================================================== -----BEGIN PGP SIGNATURE----- Comment: http://www.auscert.org.au/render.html?it=1967 iQCVAwUBQs4WESh9+71yA2DNAQKKiQP/WzGnGkEGfsUViGiUvorwpzTXCMrdFMiR 7eeGb/AJ58wGvTOduqR9APTXrNUgKxdfC5Hr0Xwe+/V04v92LT9c9Gw25qfsoF51 ddyS2hTD1yTE2Sc80TWump0HnvO3kzooKwnP3DfjGVPxVS03BuAXE1Meg9cNgWa2 ooGUr3QyFDI= =Qky6 -----END PGP SIGNATURE-----