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-----BEGIN PGP SIGNED MESSAGE----- =========================================================================== AUSCERT External Security Bulletin Redistribution ESB-2000.172 -- CERT Advisory CA-2000-13 Two Input Validation Problems In FTPD 14 July 2000 =========================================================================== AusCERT Security Bulletin Summary --------------------------------- Product: ftpd Vendor: Washington University Operating System: Linux Unix Platform: N/A Impact: Root Compromise Access Required: Remote Ref: AA-2000.02 AL-2000.09 ESB-2000.152 -- Red Hat ESB-2000.163 -- FreeBSD ESB-2000.170 -- NetBSD - --------------------------BEGIN INCLUDED TEXT-------------------- - -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 CERT Advisory CA-2000-13 Two Input Validation Problems In FTPD Original release date: July 7, 2000 Last revised: -- Source: CERT/CC A complete revision history is at the end of this file. Systems Affected * Any system running wu-ftpd 2.6.0 or earlier * Any system running ftpd derived from wu-ftpd 2.0 or later * Some systems running ftpd derived from BSD ftpd 5.51 or BSD ftpd 5.60 (the final BSD release) Overview A vulnerability involving an input validation error in the "site exec" command has recently been identified in the Washington University ftpd (wu-ftpd) software package. Sites running affected systems are advised to update their wu-ftpd software as soon as possible. A similar but distinct vulnerability has also been identified that involves a missing format string in several setproctitle() calls. It affects a broader number of ftp daemons. Please see Appendix A of this document for specific information about the status of specific ftpd implementations and solutions. I. Description "Site exec" Vulnerability A vulnerability has been identified in wu-ftpd and other ftp daemons based on the wu-ftpd source code. Wu-ftpd is a common package used to provide file transfer protocol (ftp) services. This vulnerability is being discussed as the wu-ftpd "site exec" or "lreply" vulnerability in various public forums. Incidents involving the exploitation of this vulnerability-which enables remote users to gain root privileges-have been reported to the CERT Coordination Center. The problem is described in AUSCERT Advisory AA-2000.02, "wu-ftpd 'site exec' Vulnerability," which is available from ftp://ftp.auscert.org.au/pub/auscert/advisory/AA-2000.02 The wu-ftpd "site exec" vulnerability is the result of missing character-formatting argument in several function calls that implement the "site exec" command functionality. Normally if "site exec" is enabled, a user logged into an ftp server (including the 'ftp' or 'anonymous' user) may execute a restricted subset of quoted commands on the server itself. However, if a malicious user can pass character format strings consisting of carefully constructed *printf() conversion characters (%f, %p, %n, etc) while executing a "site exec" command, the ftp daemon may be tricked into executing arbitrary code as root. The "site exec" vulnerability appears to have been in the wu-ftpd code since the original wu-ftpd 2.0 came out in 1993. Any vendors who have based their own ftpd distributions on this vulnerable code are also likely to be vulnerable. The vulnerability appears to be exploitable if a local user account can be used for ftp login. Also, if the "site exec" command functionality is enabled, then anonymous ftp login allows sufficient access for an attack. setproctitle() Vulnerability A separate vulnerability involving a missing character-formatting argument in setproctitle(), a call which sets the string used to display process identifier information, is also present in wu-ftpd. Other ftpd implementations have been found to have vulnerable setproctitle() calls as well, including those from proftpd and OpenBSD. The setproctitle() vulnerability appears to have been present in various ftpd implementations since at least BSD ftpd 5.51 (which predates wuarchive-ftpd 1.0). It has also been confirmed to be present in BSD ftpd 5.60 (the final BSD release). Any vendors who have based their own ftpd distributions on this vulnerable code are also likely to be vulnerable. It should be noted that many operating systems do not support setproctitle() calls. However, other software engineering defects involving the same type of missing character-formatting argument may be present. Intruder Activity One possible indication you are being attacked with either of these vulnerabilities may be the appearance of syslog entries similar to the following: Jul 4 17:43:25 victim ftpd: USER ftp Jul 4 17:43:25 victim ftpd: PASS [malicious shellcode] Jul 4 17:43:26 victim ftpd: ANONYMOUS FTP LOGIN FROM attacker.example.com [10.29.23.19], [malicious shellcode] Jul 4 17:43:28 victim-site ftpd: SITE EXEC (lines: 0): %.f%.f%.f%.f%.f%.f%.f%.f%.f%.f%.f%.f%.f%.f%.f%.f%.f%.f%.f%.f% .f%.f%.f%.f%.f%.f%.f%.f%.f%.f%.f%.f%.f%.f%.f%.f%.f%.f%.f%.f%. f%.f%.f%.f%.f%.f%.f%.f%.f%.f%.f%.f%.f%.f%.f%.f%.f%.f%.f%.f%.f %.f%.f%.f%.f%.f%.f%.f%.f%.f%.f%.f%.f%.f%.f%.f%.f%.f%.f%.f%.f% .f%.f%.f%.f%.f%.f%.f%.f%.f%.f%.f%.f%.f%.f%.f%.f%.f%.f%.f%.f%. f%.f%.f%.f%.f%.f%.f%.f%.f%.f%.f%.f%.f%.f%.f%.f%.f%.f%.f%.f%.f %.f%.f%.f%.f%.f%.f%.f%.f%.f%.f%.f%.f%.f%c%c%c%.f|%p Jul 4 17:43:28 victim ftpd: FTP session closed Details and exploits for both the "site exec" and setproctitle() vulnerabilities have been posted in various public forums. Please see http://www.securityfocus.com/vdb/bottom.html?section=discussion&vid=1387 http://www.securityfocus.com/vdb/bottom.html?section=discussion&vid=1438 http://ciac.llnl.gov/ciac/bulletins/k-054.shtml The CERT/CC has received reports of both of these vulnerabilities being successfully exploited on the Internet. Please check our Current Activity page for updates regarding intruder activity involving these vulnerabilities. II. Impact By exploiting any of these input validation problems, local or remote users logged into the ftp daemon may be able execute arbitrary code as root. An anonymous ftp user may also be able to execute arbitrary code as root. III. Solution Upgrade your version of ftpd Please see Appendix A of this advisory for more information about the availability of updated ftpd packages specific for your system. Apply a patch from your vendor If you are running vulnerable ftpd implementations and cannot upgrade, you need to apply the appropriate vendor patches and recompile and/or reinstall the ftpd server software. Appendix A contains information provided by vendors for this advisory. We will update the appendix as we receive more information. If you do not see your vendor's name, the CERT/CC did not hear from that vendor. Please contact your vendor directly. Disable ftp services If neither an upgrade nor a patch can be applied, the CERT/CC recommends disabling all vulnerable wu-ftpd and proftpd servers. While disabling "site exec" command functionality or anonymous ftp access minimizes exposure to the "site exec" vulnerability, neither is a complete solution and may not mitigate against the risks involved with exposure to the setproctitle() vulnerability. Appendix A. Vendor Information BSDI Current versions of BSD/OS do not include any version of wu-ftpd. The BSDI ftpd is not vulnerable to the reported problems; it is not based on the wu-ftpd code. The version of ftpd in modern versions of BSD/OS is not vulnerable to the generic setproctitle() vulnerabilities. Caldera Systems, Inc Please see CSSA-2000-020.0 regarding the wu-ftpd issue and OpenLinux: ftp://ftp.calderasystems.com/pub/OpenLinux/security/CSSA-2000-020.0.txt Copyright © 2000 Caldera Systems, Inc. Conectiva S.A. Please see: http://www.securityfocus.com/templates/archive.pike?list=1&msg=20000623212826.A13925@conectiva.com.br Debian GNU/Linux Please see the following regarding the wu-ftpd "site exec" issue: http://www.debian.org/security/2000/20000623 Copyright © 1997-2000 SPI FreeBSD, Inc. Please see FreeBSD-SA-00:29, Security Advisory for wu-ftpd in the ports collection, for complete information. In part it states: The wu-ftpd 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 3400 third-party applications in a ready-to-install format. The ports collections shipped with FreeBSD 3.5 and 4.0 contains this problem since it was discovered after the release. 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. [With respect to setproctitle()] it turns out that FreeBSD fixed this bug in the system ftpd back in 1996, so it is not present in all versions of FreeBSD since 2.2.0. We also ship optional third-party ftpds in the ports collection: we had patched wu-ftpd and believed it to be fixed (it was the subject of advisory SA-00:29), but in light of the other recent email from CERT. We will re-check to make sure all of the vulnerabilities were patched. Proftpd is also currently vulnerable but [has been patched]. Other third-party ftpds may or may not be vulnerable at this time (we advise users to install ports at their own risk), and we will release security advisories as they are discovered and fixed. Hewlett-Packard Company HP is vulnerable, patches in process, watch for the HP security bulletin to be issued. MandrakeSoft Inc. Please see the MANDRAKE 7.1 update section for wu-ftpd information at: http://www.linux-mandrake.com/en/fupdates.php3 Microsoft Coporation The IIS FTP service is not is not affected by these issues. MIT Kerberos Development Team It seems that the MIT Kerberos ftpd is based on BSD ftpd revision 5.40, and has never contained any serious format string related bugs for some reason. It is possible that by defining an undocumented CPP macro SETPROCTITLE, calls to setproctitle() can be made, however, there is an internally declared setproctitle() function that does not take a format string as its argument, and is hence not vulnerable. ProFTPD Project Upgrade to ProFTPD 1.2.0 Please see the discussion concerning setproctitle() at http://www.proftpd.org/proftpd-l-archive/00-07/msg00059.html http://www.proftpd.org/proftpd-l-archive/00-07/msg00060.html http://bugs.proftpd.net/show_bug.cgi?id=121 http://www.proftpd.net/security.html OpenBSD The setproctitle bug is in OpenBSD. Please see: http://www.openbsd.org/errata.html#ftpd Redhat Please see RHSA-2000-039-02 regarding the wu-ftpd issue: http://www.redhat.com/support/errata/RHSA-2000-039-02.html Copyright © 2000 Red Hat, Inc. All rights reserved. Slackware Linux Project Please see the patches made available regarding the wu-ftpd issue, at: ftp://ftp.slackware.com/pub/slackware/slackware-7.1/patches/wu-ftpd-patch.README Sun Microsystems [...] Our engineering team and they do not feel that Solaris is vulnerable. SuSE Ltd. Please see SuSE Security Announcement #53 regarding the wu-ftpd issue, at: http://www.suse.de/de/support/security/suse_security_announce_53.txt WU-FTPD Development Group The WU-FTPD Development Group's primary distribution site is mirrored world-wide. A list of mirrors is available from: http://www.wu-ftpd.org/mirrors.txt If possible, please use a mirror to obtain patches or the latest version. Upgrade your version of wu-ftpd The latest release of wu-ftpd, version 2.6.1, has been released to address these and several other security issues: ftp://ftp.wu-ftpd.org/pub/wu-ftpd/wu-ftpd-2.6.1.tar.gz ftp://ftp.wu-ftpd.org/pub/wu-ftpd/wu-ftpd-2.6.1.tar.gz.asc ftp://ftp.wu-ftpd.org/pub/wu-ftpd/wu-ftpd-2.6.1.tar.Z ftp://ftp.wu-ftpd.org/pub/wu-ftpd/wu-ftpd-2.6.1.tar.Z.asc Apply a patch The wu-ftpd developers have published the following patch for wu-ftpd 2.6.0: ftp://ftp.wu-ftpd.org/pub/wu-ftpd/patches/apply_to_2.6.0/lreply-buffer-overflow.patch _________________________________________________________________ The CERT Coordination Center thanks Gregory Lundberg and Theo de Raadt for their help in developing this advisory. _________________________________________________________________ Author: Jeffrey S. Havrilla ______________________________________________________________________ This document is available from: http://www.cert.org/advisories/CA-2000-13.html ______________________________________________________________________ CERT/CC Contact Information Email: firstname.lastname@example.org Phone: +1 412-268-7090 (24-hour hotline) Fax: +1 412-268-6989 Postal address: CERT Coordination Center Software Engineering Institute Carnegie Mellon University Pittsburgh PA 15213-3890 U.S.A. CERT personnel answer the hotline 08:00-20:00 EST(GMT-5) / EDT(GMT-4) Monday through Friday; they are on call for emergencies during other hours, on U.S. holidays, and on weekends. Using encryption We strongly urge you to encrypt sensitive information sent by email. Our public PGP key is available from http://www.cert.org/CERT_PGP.key If you prefer to use DES, please call the CERT hotline for more information. Getting security information CERT publications and other security information are available from our web site http://www.cert.org/ To be added to our mailing list for advisories and bulletins, send email to email@example.com and include SUBSCRIBE your-email-address in the subject of your message. * "CERT" and "CERT Coordination Center" are registered in the U.S. Patent and Trademark Office. ______________________________________________________________________ NO WARRANTY Any material furnished by Carnegie Mellon University and the Software Engineering Institute is furnished on an "as is" basis. Carnegie Mellon University makes no warranties of any kind, either expressed or implied as to any matter including, but not limited to, warranty of fitness for a particular purpose or merchantability, exclusivity or results obtained from use of the material. Carnegie Mellon University does not make any warranty of any kind with respect to freedom from patent, trademark, or copyright infringement. _________________________________________________________________ Conditions for use, disclaimers, and sponsorship information Copyright 2000 Carnegie Mellon University Revision History July 7, 2000: Initial release - -----BEGIN PGP SIGNATURE----- Version: PGP for Personal Privacy 5.0 Charset: noconv iQA/AwUBOWYdxVr9kb5qlZHQEQJRpgCfZA2ep1eMkg5B4aqBZbZOtKeXWDoAnRSe ct12Oprnm91UvyxUJv9gdW1v =Cs9w - -----END PGP SIGNATURE----- - --------------------------END INCLUDED TEXT-------------------- 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. The decision to use any or all of this information is the responsibility of each user or organisation, and should be done so in accordance with site policies and procedures. NOTE: This is only the original release of the security bulletin. It may not be updated when updates to the original are made. If downloading at a later date, it is recommended that the bulletin is retrieved directly from the original authors to ensure that the information is still current. Contact information for the authors of the original document is included in the Security Bulletin above. If you have any questions or need further information, please contact them directly. Previous advisories and external security bulletins can be retrieved from: http://www.auscert.org.au/Information/advisories.html If you believe that your system has been compromised, contact AusCERT or your representative in FIRST (Forum of Incident Response and Security Teams). Internet Email: firstname.lastname@example.org 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). 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