-----BEGIN PGP SIGNED MESSAGE----- ______________________________________________________________________________ SuSE Security Announcement Package: nkitb/nkitserv/telnetd Announcement-ID: SuSE-SA:2001:029 Date: Mon Sep 3 12:55:58 MEST 2001 Affected SuSE versions: [6.1, 6.2,] 6.3, 6.4, 7.0, 7.1, 7.2 Vulnerability Type: remote code execution Severity (1-10): 8 SuSE default package: yes Other affected systems: All UN*X Systems shipping BSD derived telnetd Content of this advisory: 1) security vulnerability resolved: Buffer overflow in in.telnetd problem description, discussion, solution and upgrade information 2) pending vulnerabilities, solutions, workarounds 3) standard appendix (further information) ______________________________________________________________________________ 1) problem description, brief discussion, solution, upgrade information The telnet server which is shipped with SuSE distributions contains a remotely exploitable buffer-overflow within its telnet option negotiation code. This bug is wide-spread on UN*X systems and affects almost all implementations of telnet daemons available. SuSE 7.2 distribution ships the telnet-server package which contains the vulnerable telnet daemon. This package has been fixed. The SuSE Linux distributions 6.3 and 6.4 contain versions and implementations of the telnet-daemon that are vulnerable, but the complexity of the code requires a full source code audit of the software. In order not to further delay the release of the packages for the SuSE Linux 7.x distributions, we recommend to disable the telnet daemon on the 6.x distributions. This can be done by commenting out the line in /etc/inetd.conf that starts with "telnet", and then reloading the inetd configuration using the command "killall -1 inetd". Another option is to not start the inetd in the first place if you do not need any of the services provided by the inetd daemon. Disabling inetd permanently involves killing the running inetd process ("killall -TERM inetd") and setting the variable START_INETD in /etc/rc.config to "no" (as opposed to "yes"). Disabling the telnet service is the preliminary solution/workaround against the problems with the telnetd daemon. We hope to be able to provide a better solution. The SuSE Linux distributions 7.0, 7.1 and 7.2 have similar implementations of in.telnetd, and for all of these distributions there are update packages available. Please note that the package that contains the /usr/sbin/in.telnetd program (the server program) has changed over the different releases of the SuSE Linux distribution. In the 7.0 and 7.1 distributions the package is called "nkitserv". The 7.2 distribution lists the telnet server in the package "telnet-server". Please download the packages and verify them as described in section 3. After successfull authentication you can update your packages with the command `rpm -Uhv file.rpm'. Further action should not be necessary to activate the update since the in.telnetd daemon is started from a new by inetd upon every accepted connection from the network. Regardless of the availiability of fixed packages of the telnet-daemon, SuSE Security strongly recommend to disable the telnet service if you do not use it. In addition to that, only cryptographically protected protocols such as secure shell (ssh, package openssh) can be an efficient countermeasure against sniffing and spoofing type attacks. Due to significantly more comfort (such as X11-forwarding, multiple authentication methods, ...), the transition to ssh should be worth the effort in any case. i386 Intel Platform: SuSE-7.2 ftp://ftp.suse.com/pub/suse/i386/update/7.2/n1/telnet-server-1.0-69.i386.rpm 0adc05af9762bd4c63eee464ca3131d1 source rpm: ftp://ftp.suse.com/pub/suse/i386/update/7.2/zq1/telnet-1.0-69.src.rpm fe313553d1a6f022c7eb2f87ccd6772f SuSE-7.1 ftp://ftp.suse.com/pub/suse/i386/update/7.1/n1/nkitserv-2001.8.14-0.i386.rpm e0636eec04ccf2129b0e2ea0ee40c231 source rpm: ftp://ftp.suse.com/pub/suse/i386/update/7.1/zq1/nkitb-2001.8.14-0.src.rpm 57760fcd8e064e89591203f7ba9adefc SuSE-7.0 ftp://ftp.suse.com/pub/suse/i386/update/7.0/n1/nkitserv-2001.8.16-0.i386.rpm e8a859d5a648a572fc08628247c1e2d6 source rpm: ftp://ftp.suse.com/pub/suse/i386/update/7.0/zq1/nkitb-2001.8.16-0.src.rpm 33d4abc52926ac957f21b8c8aae7adce Sparc Platform: SuSE-7.1 ftp://ftp.suse.com/pub/suse/sparc/update/7.1/n1/nkitserv-2001.8.14-0.sparc.rpm 3ef64d1cae35be51c9eff9bebcf4cf79 source rpm: ftp://ftp.suse.com/pub/suse/sparc/update/7.1/zq1/nkitb-2001.8.14-0.src.rpm 4cb76a16bd2f53c37a7cee728ea21c81 SuSE-7.0 ftp://ftp.suse.com/pub/suse/sparc/update/7.0/n1/nkitserv-2001.8.16-0.sparc.rpm f4901a4a271657d0379aff114d30b912 source rpm: ftp://ftp.suse.com/pub/suse/sparc/update/7.0/zq1/nkitb-2001.8.16-0.src.rpm ad909d8e3d2d0a617a5a9f6e3d7cd74d AXP Alpha Platform: SuSE-7.1 ftp://ftp.suse.com/pub/suse/axp/update/7.1/n1/nkitserv-2001.8.14-0.alpha.rpm efad3412a8d333947bcf74695c023ea8 source rpm: ftp://ftp.suse.com/pub/suse/axp/update/7.1/zq1/nkitb-2001.8.14-0.src.rpm 94d0dba0396e41b4afbd3ef61c4fd8aa SuSE-7.0 ftp://ftp.suse.com/pub/suse/axp/update/7.0/n1/nkitserv-2001.8.16-0.alpha.rpm 934525486e72a5cc98736f4cb1217f93 source rpm: ftp://ftp.suse.com/pub/suse/axp/update/7.0/zq1/nkitb-2001.8.16-0.src.rpm a6623ff6d9439dea40f24ff35acefe99 Power PC Platform: SuSE-7.1 ftp://ftp.suse.com/pub/suse/ppc/update/7.1/n1/nkitserv-2001.8.14-0.ppc.rpm 4da51d1a38095e81ee389094b0f21160 source rpm: ftp://ftp.suse.com/pub/suse/ppc/update/7.1/zq1/nkitb-2001.8.14-0.src.rpm 499b282f614835fe7a7b1a9ab039c56d SuSE-7.0 ftp://ftp.suse.com/pub/suse/ppc/update/7.0/n1/nkitserv-2001.8.16-0.ppc.rpm 262f3fc3653042976c8cc36a2cd7e44d source rpm: ftp://ftp.suse.com/pub/suse/ppc/update/7.0/zq1/nkitb-2001.8.16-0.src.rpm 7cba8393bb8a71cf4d39fb480a71b42e ______________________________________________________________________________ 2) Pending vulnerabilities in SuSE Distributions and Workarounds: - w3m The w3m browser contains a buffer-overflow which allows remote-attackers to execute arbitrary code or to crash the w3m web-client when viewing special crafted sites. Please update to the newest w3m packages available on the ftp-server. - dip The dip program is executable as setuid root program for users in the "dialout" group, a privilege that has been issued by the administrator for a trusted user group. This bug will be corrected in future releases of the SuSE Linux distribution. ______________________________________________________________________________ 3) standard appendix: authenticity verification, additional information - Package authenticity verification: SuSE update packages are available on many mirror ftp servers all over the world. While this service is being considered valuable and important to the free and open source software community, many users wish to be sure about the origin of the package and its content before installing the package. 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) md5sums as provided in the (cryptographically signed) announcement. 2) using the internal gpg signatures of the rpm package. 1) execute the command md5sum <name-of-the-file.rpm> 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 announcement. Since the announcement containing the checksums is cryptographically signed (usually using the key security@suse.de), the checksums show proof of the authenticity of the package. We disrecommend to subscribe to security lists which cause the email message containing the announcement to be modified so that the signature does not match after transport through the mailing list software. Downsides: You must be able to verify the authenticity of the announcement in the first place. If RPM packages are being rebuilt and a new version of a package is published on the ftp server, all md5 sums for the files are useless. 2) rpm package signatures provide an easy way to verify the authenticity of an rpm package. Use the command rpm -v --checksig <file.rpm> to verify the signature of the package, where <file.rpm> is the filename of the rpm package that you have downloaded. Of course, package authenticity verification can only target an uninstalled rpm package file. Prerequisites: a) gpg is installed b) The package is signed using a certain key. The public part of this key must be installed by the gpg program in the directory ~/.gnupg/ under the user's home directory who performs the signature verification (usually root). You can import the key that is used by SuSE in rpm packages for SuSE Linux by saving this announcement to a file ("announcement.txt") and running the command (do "su -" to be root): gpg --batch; gpg < announcement.txt | gpg --import SuSE Linux distributions version 7.1 and thereafter install the key "build@suse.de" upon installation or upgrade, provided that the package gpg is installed. The file containing the public key is placed at the toplevel directory of the first CD (pubring.gpg) and at ftp://ftp.suse.com/pub/suse/pubring.gpg-build.suse.de . - SuSE runs two security mailing lists to which any interested party may subscribe: suse-security@suse.com - general/linux/SuSE security discussion. All SuSE security announcements are sent to this list. To subscribe, send an email to <suse-security-subscribe@suse.com>. suse-security-announce@suse.com - SuSE's announce-only mailing list. Only SuSE's security annoucements are sent to this list. To subscribe, send an email to <suse-security-announce-subscribe@suse.com>. For general information or the frequently asked questions (faq) send mail to: <suse-security-info@suse.com> or <suse-security-faq@suse.com> respectively. =================================================== SuSE's security contact is <security@suse.com>. The <security@suse.com> public key is listed below. =================================================== ______________________________________________________________________________ The information in this advisory may be distributed or reproduced, provided that the advisory is not modified in any way. In particular, it is desired that the cleartext signature shows proof of the authenticity of the text. SuSE GmbH makes no warranties of any kind whatsoever with respect to the information contained in this security advisory. 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