SuSE alert: openssh

Posted by dave on Dec 6, 2001 11:56 AM EDT
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This is a re-release of the SuSE Security Announcement SuSE-SA:2001:044, adding another bugfix for the openssh package as well as more detailed information about the vulnerabilities to prevent misunderstandings.



                        SuSE Security Announcement

        Package: openssh
        Announcement-ID: SuSE-SA:2001:045
        Date: Thursday, Dec 6th 2001 21:30 MET
        Affected SuSE versions: 6.4, 7.0, 7.1, 7.2, 7.3
        Vulnerability Type: local privilege escalation
        Severity (1-10): 5
        SuSE default package: yes
        Other affected systems: systems running openssh

    Content of this advisory:
        1) security vulnerability resolved: openssh
           problem description, discussion, solution and upgrade information
        2) pending vulnerabilities, solutions, workarounds
        3) standard appendix (further information)


1) Re-release of SuSE Security Announcement SuSE-SA:2001:044, brief history,
    Clarification, new problem fixed, upgrade information.

    This is a re-release of the SuSE Security Announcement SuSE-SA:2001:044,
    adding another bugfix for the openssh package as well as more detailed
    information about the vulnerabilities to prevent misunderstandings.

    The currently supported SuSE distributions 6.4 and newer come with two
    implementations of the secure shell protocol: The package names are
    "ssh" and "openssh".

    Brief history:
    In 1998, a vulnerability of the secure shell protocol in version 1 has
    been discovered and named "crc32 compensation attack". The vulnerability
    allows an attacker to insert arbitrary sequences into the ssh-1 protocol
    layer. At that time, an added patch fixed the problem in the ssh
    implementation (visible in the client-side verbose output of the ssh
    command (-v): "Installing crc compensation attack detector.").
    In early 2001, Michal Zalewski discovered that the widely used patch
    was defective and opened another security hole which is being actively
    exploited today. SuSE Security announcement SuSE-SA:2001:004, published
    February 16th 2001, available at *[1], addresses this defective patch,
    among other issues.

    Our last openssh security announcement SuSE-SA:2001:044 (*[3]) may falsely
    lead to assume that the openssh-2.9.9p2 update packages on our ftp
    server fix the vulnerabilities known as crc32 compensation attack.
    This is incorrect since the openssh-2.3.0 packages released with SuSE
    Security announcement SuSE-SA:2000:047 in November 2000, available at
    *[2], already fixed the mentioned (among other) problems. The release
    of the openssh-2.9.9p2 update packages obsoletes the openssh-2.3.0 update
    We explicitly regret the used wording and apologize to the openssh
    development team, in particular Markus Friedl and Theo De Raadt, and
    thank them for their excellent work on the project.

    Scanning utilities that can be found on the internet connect to port 22
    of a server and read the version string. It should be noted that the bare
    knowlege of the secure shell protocol version string does not allow to
    determine whether a running secure shell daemon is actually vulnerable
    to the defective fix for the crc32 compensation attack.
    SuSE security receive dozens of requests about statements if the daemons
    in use are vulnerable or not. Please see reference *[1].

    New problem fixed:
    This re-release of SuSE Security Announcement SuSE-SA:2001:044 (please
    see reference *[3] below) adds another patch to the openssh-2.9.9p2
    packages: A bug allows a local attacker on the server to specify
    environment variables that can influence the login process if the
    "UseLogin" configuration option on the server side is set to "yes".
    If exploited, the local attacker on the secure shell server can execute
    arbitrary commands as root.
    In the default configuration of the package, the UseLogin option is set
    to "no", which means that the administrator of the server must have set
    the option to "yes" manually before the bug can be exploited.

    Users who upgraded their SuSE openssh package before December 6th 2001
    should upgrade their package again. Use the command "rpm -q openssh"
    to see which version/release of the package you have installed, and
    compare this version with the one as listed below.

    Upgrade information:
    You can find out which implementation of the ssh protocol you are using
    with the command "rpm -qf /usr/bin/ssh".
    If you use the ssh-1.2.* package, please read Reference *[1].
    If you use the openssh-* package, please download the rpm package for
    your distribution from the URL list below, verify its integrity using
    the methods as described in section 3) of this security announcement
    and install the package using the command

        rpm -Uhv file.rpm

    where file.rpm is the filename of the package that you have downloaded.


    The sshd secure shell daemon on the server side has to be restarted for
    the new package to become active. If you are logged on on the console,
    the simple command "rcsshd restart" should do this for you.
    If you are logged on via secure shell, you should make sure that you
    do not terminate the connections that are established through the running
    secure shell daemon/its children. In this case, kill the daemon after
    package installation using the command
        kill -TERM `cat /var/run/`
    and then restart the daemon with the command
    as root.

    Then, verify that the login procedure works as before. One of the main
    changes in the new openssh package is that the file
    $HOME/.ssh/authorized_keys2 is only read by the server if the file
    $HOME/.ssh/authorized_keys does not exist and if protocol version 2 is
    being used. The file $HOME/.ssh/authorized_keys2 can be removed after
    its contents have been added to $HOME/.ssh/authorized_keys.
    The two configuration files /etc/ssh/sshd_config (server side) and
    /etc/ssh/ssh_config (client side) contained in the openssh package
    do not get overwritten upon installation or upgrade, if you have changed
    them manually. Instead, the new configuration files are written with a
    .rpmnew suffix. The defaults as provided in the SuSE package make an
    effort to establish both convenience as well as security.

    NOTE: Packages for SuSE Linux distributions 7.0 and older containing
    cryptographic software are located on our German ftp server
    for legal reasons. Packages for all other distributions (7.1 and newer)
    can be found at their regular path at

    i386 Intel Platform:
    source rpm:

    source rpm:

    source rpm:

    source rpm:

    source rpm:

    Sparc Platform:
    source rpm:

    The update packages for the SuSE Linux 7.1 Sparc distributions are not
    available yet. The package can soon be found at

    source rpm:

    AXP Alpha Platform:
    source rpm:

    The update packages for the SuSE Linux AXP/Alpha distributions before
    SuSE-7.1 are not available on our ftp server yet. These packages can be
    found at the usual location in the update paths on

    PPC Power PC Platform:
    source rpm:

    source rpm:

    source rpm:

    source rpm:


2) Pending vulnerabilities in SuSE Distributions and Workarounds:

  - We are currently testing kernel update packages for the recently
    found local security flaw in the ELF binary loader in the Linux
    kernel of all v2.4 versions and expect to be able to announce these
    update rpm packages soon with a re-release of our kernel security


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 <> or <>.
    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


Version: 2.6.3i
Charset: noconv


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