SuSE: nkitb/nkitserv/telnetd vulnerabiilties

    Date03 Sep 2001
    CategorySuSE
    2835
    Posted ByLinuxSecurity Advisories
    The telnet server which is shipped with SuSE distributions contains a remotely exploitable buffer-overflow within its telnet option negotiation code.
    
    ______________________________________________________________________________
    
                            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 
           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 This email address is being protected from spambots. You need JavaScript enabled to view it.
    	),
           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 
           to verify the signature of the package, where  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 "This email address is being protected from spambots. You need JavaScript enabled to view it." 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:
    
        This email address is being protected from spambots. You need JavaScript enabled to view it.
            -   general/linux/SuSE security discussion.
                All SuSE security announcements are sent to this list.
                To subscribe, send an email to
                    <This email address is being protected from spambots. You need JavaScript enabled to view it.>.
    
        This email address is being protected from spambots. You need JavaScript enabled to view it.
            -   SuSE's announce-only mailing list.
                Only SuSE's security annoucements are sent to this list.
                To subscribe, send an email to
                    <This email address is being protected from spambots. You need JavaScript enabled to view it.>.
    
        For general information or the frequently asked questions (faq)
        send mail to:
            <This email address is being protected from spambots. You need JavaScript enabled to view it.> or
            <This email address is being protected from spambots. You need JavaScript enabled to view it.> respectively.
    
        ===================================================
        SuSE's security contact is <This email address is being protected from spambots. You need JavaScript enabled to view it.>.
        The <This email address is being protected from spambots. You need JavaScript enabled to view it.> 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.
    
    Type Bits/KeyID    Date       User ID
    pub  2048R/3D25D3D9 1999-03-06 SuSE Security Team <This email address is being protected from spambots. You need JavaScript enabled to view it.>
    pub  1024D/9C800ACA 2000-10-19 SuSE Package Signing Key <This email address is being protected from spambots. You need JavaScript enabled to view it.>
    
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