-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 =============================================================================== >> CERT-NL, 01-Mar-2000 << >> All CERT-NL information has been moved to http://cert.surfnet.nl. Links << >> to CERT-NL information contained in this advisory are therefore outdated. << >> << >> CERT-NL also has stopped the CERT-CC-Mirror service. Due to this the << >> links to the CERT-CC mirror are obsolete. Visit the CERT-CC site for the << >> complete CERT-CC advisory texts: http://www.cert.org << =============================================================================== =============================================================================== Security Advisory CERT-NL =============================================================================== Author/Source : Teun Nijssen Index : S-97-06 Distribution : World Page : 1 Classification: External Version: 1 Subject : ftpd race condition Date : 29-Jan-97 =============================================================================== By courtesy of AUSCERT we received information on a vulnerability in various implementations of the ftp daemon CERT-NL recommends to check relevance of this advisory against ftp service software. ============================================================================== AA-97.03 AUSCERT Advisory ftpd Signal Handling Vulnerability 29 January 1997 Last Revised: -- --------------------------------------------------------------------------- AUSCERT has received information that there is a vulnerability in some versions of ftpd distributed and installed under various Unix platforms. This vulnerability may allow regular and anonymous ftp users to read or write to arbitrary files with root privileges. The vulnerabilities in ftpd affect various third party and vendor versions of ftpd. AUSCERT recommends that sites take the steps outlined in section 3 as soon as possible. This advisory will be updated as more information becomes available. --------------------------------------------------------------------------- 1. Description AUSCERT has received information concerning a vulnerability in some vendor and third party versions of the Internet File Transfer Protocol server, ftpd(8). This vulnerability is caused by a signal handling routine increasing process privileges to root, while still continuing to catch other signals. This introduces a race condition which may allow regular, as well as anonymous ftp, users to access files with root privileges. Depending on the configuration of the ftpd server, this may allow intruders to read or write to arbitrary files on the server. This attack requires an intruder to be able to make a network connection to a vulnerable ftpd server. Sites should be aware that the ftp services are often installed by default. Sites can check whether they are allowing ftp services by checking, for example, /etc/inetd.conf: # grep -i '^ftp' /etc/inetd.conf Note that on some systems the inetd configuration file may have a different name or be in a different location. Please consult your documentation if the configuration file is not found in /etc/inetd.conf. If your site is offering ftp services, you may be able to determine the version of ftpd by checking the notice when first connecting. The vulnerability status of specific vendor and third party ftpd servers can be found in Section 3. Information involving this vulnerability has been made publicly available. 2. Impact Regular and anonymous users may be able to access arbitrary files with root privileges. Depending on the configuration, this may allow anonymous, as well as regular, users to read or write to arbitrary files on the server with root privileges. 3. Workarounds/Solution AUSCERT recommends that sites prevent the possible exploitation of this vulnerability by immediately applying vendor patches if they are available. Specific vendor information regarding this vulnerability is given in Section 3.1. If the ftpd supplied by your vendor is vulnerable and no patches are available, sites may wish to install a third party ftpd which does not contain the vulnerability described in this advisory (Section 3.2). 3.1 Vendor patches The following vendors have provided information concerning the vulnerability status of their ftpd distribution. Detailed information has been appended in Appendix A. If your vendor is not listed below, you should contact your vendor directly. Berkeley Software Design, Inc. Digital Equipment Corporation The FreeBSD Project Hewlett-Packard Corporation IBM Corporation The NetBSD Project The OpenBSD Project Red Hat Software Washington University ftpd (Academ beta version) Wietse Venema's logdaemon ftpd 3.2 Third party ftpd distributions AUSCERT has received information that the following third party ftpd distributions do not contain the signal handling vulnerability described in this advisory: wu-ftpd 2.4.2-beta-12 logdaemon 5.6 ftpd Sites should ensure they are using the current version of this software. Information on these distributions is contained in Appendix A. Sites should note that these third party ftpd distributions may offer some different functionality to vendor versions of ftpd. AUSCERT advises sites to read the documentation provided with the above third party ftpd distributions before installing. ........................................................................... Appendix A Berkeley Software Design, Inc. (BSDI) ===================================== BSD/OS 2.1 is vulnerable to the ftpd problem described in this advisory. Patches have been issued and may be retrieved via the email server or from: ftp://ftp.bsdi.com/bsdi/patches/patches-2.1/U210-033 Digital Equipment Corporation ============================= At the time of writing this document, patches(binary kits) are in progress and final testing is expected to begin soon. Digital will provide notice of the completion/availability of the kits through AES services (DIA, DSNlink FLASH) and be available from your normal Digital Support channel. The FreeBSD Project =================== The FreeBSD Project has informed AUSCERT that the vulnerability described in this advisory has been fixed in FreeBSD-current (from January 27, 1997), and will be fixed in the upcoming FreeBSD 2.2 release. All previous versions of FreeBSD are vulnerable. Hewlett-Packard Corporation =========================== Hewlett-Packard has informed AUSCERT that the ftpd distributed with HP-UX 9.x and 10.x are vulnerable to this problem. Patches are currently in process. IBM Corporation =============== The version of ftpd shipped with AIX is vulnerable to the conditions described in the advisory. The following APARs will be available shortly: AIX 3.2: APAR IX65536 AIX 4.1: APAR IX65537 AIX 4.2: APAR IX65538 To Order -------- APARs may be ordered using Electronic Fix Distribution (via FixDist) or from the IBM Support Center. For more information on FixDist, reference URL: http://service.software.ibm.com/aixsupport/ or send e-mail to aixserv@austin.ibm.com with a subject of "FixDist". IBM and AIX are registered trademarks of International Business Machines Corporation. The NetBSD Project =================== NetBSD (all versions) have the ftpd vulnerability described in this advisory. It has since been fixed in NetBSD-current. NetBSD have also made patches available and they can be retrieved from: ftp://ftp.netbsd.org/pub/NetBSD/misc/security/19970123-ftpd The OpenBSD Project =================== OpenBSD 2.0 did have the vulnerability described in this advisory, but has since been fixed in OpenBSD 2.0-current (from January 5, 1997). Red Hat Software ================ The signal handling code in wu-ftpd has some security problems which allows users to read all files on your system. A new version of wu-ftpd is now available for Red Hat 4.0 which Red Hat suggests installing on all of your systems. This new version uses the same fix posted to redhat-list@redhat.com by Savochkin Andrey Vladimirovich. Users of Red Hat Linux versions earlier then 4.0 should upgrade to 4.0 and then apply all available security packages. Users whose computers have direct internet connections may apply this update by using one of the following commands: Intel: rpm -Uvh ftp://ftp.redhat.com/updates/4.0/i386/wu-ftpd-2.4.2b11-9.i386.rpm Alpha: rpm -Uvh ftp://ftp.redhat.com/updates/4.0/axp/wu-ftpd-2.4.2b11-9.axp.rpm SPARC: rpm -Uvhftp://ftp.redhat.com/updates/4.0/sparc/wu-ftpd-2.4.2b11-9.sparc.rpm All of these packages have been signed with Red Hat's PGP key. wu-ftpd Academ beta version =========================== The current version of wu-ftpd (Academ beta version), wu-ftpd 2.4.2-beta-12, does not contain the vulnerability described in this advisory. Sites using earlier versions should upgrade to the current version immediately. At the time of writing, the current version can be retrieved from: ftp://ftp.academ.com/pub/wu-ftpd/private/ logdaemon Distribution ====================== The current version of Wietse Venema's logdaemon (5.6) package contains an ftpd utility which addresses the vulnerability described in this advisory. Sites using earlier versions of this package should upgrade immediately. The current version of the logdaemon package can be retrieved from: ftp://ftp.win.tue.nl/pub/security/ ftp://ftp.auscert.org.au/pub/mirrors/ftp.win.tue.nl/logdaemon/ ftp://ftp.cert.dfn.de/pub/tools/net/logdaemon/ The MD5 checksum for Version 5.6 of the logdaemon package is: MD5 (logdaemon-5.6.tar.gz) = 5068f4214024ae56d180548b96e9f368 --------------------------------------------------------------------------- AUSCERT thanks David Greenman, Wietse Venema (visiting IBM T.J. Watson Research) and Stan Barber (Academ Consulting Services) for their contributions in finding solutions to this vulnerability. Thanks also to Dr Leigh Hume (Macquarie University), CERT/CC, and DFNCERT for their assistance in this matter. AUSCERT also thanks those vendors that provided feedback and patch information contained in this advisory. - --------------------------------------------------------------------------- ============================================================================== CERT-NL is the Computer Emergency Response Team for SURFnet customers. SURFnet is the Dutch network for educational, research and related institutes. CERT-NL is a member of the Forum of Incident Response and Security Teams (FIRST). All CERT-NL material is available under: http://cert.surfnet.nl/ In case of computer or network security problems please contact your local CERT/security-team or CERT-NL (if your institute is NOT a SURFnet customer please address the appropriate (local) CERT/security-team). CERT-NL is one/two hour(s) ahead of UTC (GMT) in winter/summer, i.e. UTC+0100 in winter and UTC+0200 in summer (DST). 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