SuSE alert: sendmail

Posted by dave on Aug 23, 2001 8:34 AM EDT
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Cade Cairns of Securityfocus discovered a vulnerability in the sendmail program, the widely spread MTA used in Unix- and Unix-like systems. A local user can write arbitrary data to the process memory, resulting in user-controlled code to be executed as user root. Please note that this is a _local_ vulnerability: Local shell access is needed for the attacker to be able to take advantage of this error. The /usr/sbin/sendmail program is installed set-uid root in most installations. This special privilege is needed for the sendmail program to operate properly. The attack pattern involves running sendmail to make use of the setuid-bit. Please note that this is the first sendmail security problem since 1997.



                        SuSE Security Announcement

        Package: sendmail
        Announcement-ID: SuSE-SA:2001:028
        Date: Thursday, Aug 23rd 2001 18:10 MEST
        Affected SuSE versions: 7.0, 7.1, 7.2
        Vulnerability Type: local root compromise
        Severity (1-10): 5
        SuSE default package: yes
        Other affected systems: systems using the sendmail package

    Content of this advisory:
        1) security vulnerability resolved: sendmail
           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

    Cade Cairns of Securityfocus discovered a vulnerability in the sendmail
    program, the widely spread MTA used in Unix- and Unix-like systems.
    A local user can write arbitrary data to the process memory, resulting
    in user-controlled code to be executed as user root.
    Please note that this is a _local_ vulnerability: Local shell access
    is needed for the attacker to be able to take advantage of this error.
    The /usr/sbin/sendmail program is installed set-uid root in most
    installations. This special privilege is needed for the sendmail program
    to operate properly. The attack pattern involves running sendmail to
    make use of the setuid-bit.
    Please note that this is the first sendmail security problem since 1997.

    In this case, the vulnerability can be classified as a commandline
    processing bug while running with extended (root) privilege.
    The error itself is a result of a comparison between a signed and an
    unsigned integer when checking user-supplied data from the sendmail
    command line: A high unsigned value is being considered a negative
    signed value. A subsequent comparison is being evaluated the wrong way.
    These errors are expected to make up a new class of vulnerabilities for
    programs written in C in the near future.

    The supported SuSE Linux distributions 6.3 and 6.4 use a sendmail of
    version 8.9.3. According to Sendmail Inc., this version is not
    affected by this signedness bug.
    The SuSE Linux distributions 7.0, 7.1 and 7.2 use sendmail version
    8.11.x. All 7.x distributions are affected by the problem.

    SuSE provides update packages for the affected distributions. Please
    download the update package for your distribution and use the command
    'rpm -Uhv file.rpm' to apply the update.
    It is recommended to stop the running sendmail process(es) before
    applying the update. Use the command 'rcsendmail stop' to do this,
    and 'rcsendmail start' to restart the service after the update has
    been applied. Since the update packages only fix the security problem
    from this announcement, no reconfiguration should be necessary.

    The sendmail package needs one out of two commands to be executed after
    package installation. Use the commands
    or, alternatively (if you have disabled SuSEconfig in /etc/rc.config),
        chkstat -set /etc/permissions.d/sendmail
    to set the permissions of the sendmail package files correctly. Without
    these permission changes, the /usr/sbin/sendmail program will not operate
    properly. (Side note: All of the commands above have to be run as root!)

    i386 Intel Platform:

    source rpm:

    source rpm:

    source rpm:

    Sparc Platform:

    source rpm:

    source rpm:

    AXP Alpha Platform:

    source rpm:

    PPC Power PC Platform:

    source rpm:

    source rpm:


2) Pending vulnerabilities in SuSE Distributions, Workarounds and misc:

  - ftp server
    Our ftp server has been reorganized. The changes in
    particular are:
    * The discontinued distributions (SuSE Linux before (and including) 6.2)
      have moved to an own tree: /pub/suse/discontinued/<arch>.
      The tree there is built exactly like the tree for the currently
      supported distributions (6.3 and up).
      This change has been made to keep users from automatically applying
      updates against old problems that have been superceded by newer updates
      which are not available for the discontinued distributions.
    * The /pub/suse/<arch>/{KDE,KDE2,GNOME,X} directories have been moved
      to an own tree: /pub/suse/<arch>/supplementary/. The KDE directory
      has become famous in the KDE scene because it contains the latest
      KDE packages compiled for a SuSE distribution.
      This has been done to point out that the packages in this directory
      have been built for the respective distribution, they are tested ok,
      but since these packages have never been part of the distribution
      they are built for, there is no support for them; the packages are
      provided as-is.
    * During the next days, all packages under the /pub/suse/<arch>/update/
      tree will be gpg-signed with the DSA key (see section 3
      of this announcement).
    Currently, most of the formerly existing directories that have been moved
    are now still visible through a symlink, pointing at a directory with
    a README.
    The directory paths to the update packages for the supported distributions
    have _not_ changed.
    We kindly request mirror admins to adopt the changes to their trees.
    If you run a publically accessible mirror of, you are
    invited to send a mail to so that you are being
    notified of such changes in advance.

  - in.telnetd
    A buffer overflow vulnerability has been found in the in.telnetd telned
    daemon, a service that is enabled by default in all SuSE Linux
    distributions. The vulnerability may allow a remote attacker to gain root
    access to your system. Many unix- and unix-like operating systems are
    affected by this or a similar problem.
    There are update packages for the SuSE Linux distributions 7.1 and 7.2
    on our ftp server. The packages for the 7.1 distribution are called
    "nkitserv", for the 7.2 distributions, the name is telnet-server.
    For completeness, we also provide the other packages that are made from
    the same source rpm. Since these packages do not fix a security problem,
    there is no reason to list them here.
    We are working on a suitable solution for the 7.0 and 6.x distributions,
    while it has turned out that a fix for these distributions is non-trivial
    because a different code base has been used for these packages.
    telnet is an unencrypted protocol that offers many attack possibilities.
    If at all possible, please deactivate your telnetd by commenting it out
    in /etc/inetd.conf (killall -HUP inetd afterwards to make inetd reload
    its configuration file!). We recommend to use one of the two ssh
    implementations on our distributions as a substitute of the telnet
    protocol. Clients are available on the internet for most platforms and
    operating systems.
    An announcement will be released soon that addresses the problem in

  - Yesterday (Wednesday, 20010822) Bob Vickers (Dept of Computer Science,
    University of London) reported a locally exploitable security hole in
    the script /etc/init.d/boot. The critical function of the script is
    supposed to remove files from the defined temporary directories of the
    system as specified in /etc/rc.config (TMP_DIRS_TO_CLEAR in
    /etc/rc.config) if $CLEAR_TMP_DIRS_AT_BOOTUP (also from /etc/rc.config)
    is set to "yes". Unfortunately, the script does not take into account
    that directories can contain newlines and other non-standard characters.
    By consequence, the script can be tricked to removing files elsewhere.
    This bug is present in the SuSE Linux 7.2 version only, available for the
    Intel i386 platform. The feature responsible for this bug is disabled
    by default in a SuSE Linux 7.2 installation and must be manually
    activated for the bug to impose any risk.
    We have fixed the problem in an update package that is available at
    Please download and install the update package using the command
        rpm -Uhv aaa_base-2001.8.23-0.i386.rpm
    Disregard the messages on standard output if you have the gpg package
    installed: The postinstall script adds the DSA key
    to root's gpg public keyring if this hasn't been done already. This
    key is also listed below.
    A source rpm is also available at the usual location.
    We will not issue a dedicated security announcement for this problem.
    We thank Bob Vickers for reporting the problem to

  - openssl
    A weakness was found in the PRNG (Pseudo Random Number Generator) of
    the openssl package. As far as we could determine, the bug has no
    effect on the packages that are compiled against a library from the
    openssl package. We will however provide update packages that fix
    the found problems. Since openssl packages are not (backwards-)
    compatible to any other newer version, we have to fix the package for
    each distribution seperately. This takes some time. A special announce-
    ment will be issued as soon as all packages are available.

  - more announcements are in our queue. Please keep watching activity on
    the mailinglist (more information below).


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,
       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.
        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 "" 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 .

  - SuSE runs two security mailing lists to which any interested party may
        - general/linux/SuSE security discussion.
            All SuSE security announcements are sent to this list.
            To subscribe, send an email to
        - SuSE's announce-only mailing list.
            Only SuSE's security annoucements are sent to this list.
            To subscribe, send an email to

    For general information or the frequently asked questions (faq)
    send mail to:
        <> or
        <> respectively.

    SuSE's security contact is <>.
    The <> 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 <>
pub 1024D/9C800ACA 2000-10-19 SuSE Package Signing Key <>

Version: GnuPG v1.0.6 (GNU/Linux)
Comment: For info see


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