SuSE alert: shadow/login

Posted by dave on Oct 23, 2001 8:27 AM EDT
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Multiple Linux vendors have issued security announcements about failures of the /bin/login program to properly initialize the privileges of an authenticated user if the PAM module pam_limits is enabled. The bug has been categorized as a sequence bug, and is located in the code of the login program itself: A call to getpwnam(3) returns a pointer to a struct passwd, and the data is being used. Then, a call to PAM routines cause getpwnam(3) to be called again, but beyond the programmer's control or knowledge. The pointer as returned by the first getpwnam(3) remains the same, but the data may be different. By consequence, the data is in an undefined state. The error appears with the pam_limits PAM module only because other PAM modules do not call getpwnam(3).



                        SuSE Security Announcement

        Package: shadow/login
        Announcement-ID: SuSE-SA:2001:034
        Date: Tuesday, Oct 23rd 2001 18:00 MEST
        Affected SuSE versions: 6.3, 6.4, 7.0, 7.1, 7.2, 7.3
        Vulnerability Type: local privilege escalation
        Severity (1-10): 2
        SuSE default package: yes
        Other affected systems: most linux systems, common problem on
                                linux-like systems.

    Content of this advisory:
        1) security vulnerability resolved: shadow/login
           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

    Multiple Linux vendors have issued security announcements about failures
    of the /bin/login program to properly initialize the privileges of an
    authenticated user if the PAM module pam_limits is enabled.
    The bug has been categorized as a sequence bug, and is located in the
    code of the login program itself: A call to getpwnam(3) returns a pointer
    to a struct passwd, and the data is being used. Then, a call to PAM
    routines cause getpwnam(3) to be called again, but beyond the programmer's
    control or knowledge. The pointer as returned by the first getpwnam(3)
    remains the same, but the data may be different. By consequence, the
    data is in an undefined state. The error appears with the pam_limits
    PAM module only because other PAM modules do not call getpwnam(3).

    SuSE developers did not succeed in reproducing the error on SuSE Linux
    installations since SuSE distributions do not come with the standard
    login implementation from the util-linux collection. Instead, a version
    maintained by Thorsten Kukuk <> is used. This login
    implementation may cause wrong group IDs to be set in very rare cases.
    The harm of this bug is therefore considerably small on SuSE Linux.

    However, we provide fixed rpm packages that remedy the problem. Since
    the bug is not limited to the login program but to all programs that
    authenticate users, more security announcements in this field are to
    be expected. The Linux vendors cooperate to share the workload that
    results from the audit of these programs.

    To install the updates, please download the update package for your
    distribution and use the command 'rpm -Uhv file.rpm' to apply the update.
    Please run "SuSEconfig" after performing the package update to make sure
    that the permissions of your files are configured as the security
    settings of your installation define. Alternatively, if you have disabled
    SuSEconfig, check for the permissions of the files /usr/bin/chage,
    /usr/bin/chfn, /usr/bin/chsh, /usr/bin/expiry, /usr/bin/gpasswd and
    /usr/bin/passwd to suit your needs. Setting these executeables to 4755
    owned by root enables their functionality, removing the setuid bit
    (chmod -s) disables it.

    i386 Intel Platform:

    source rpm:

    source rpm:

    source rpm:

    source rpm:

    source rpm:

    source rpm:

    Sparc Platform:

    source rpm:

    source rpm:

    AXP Alpha Platform:

    source rpm:

    source rpm:

    source rpm:

    source rpm:

    PPC Power PC Platform:

    source rpm:

    source rpm:

    source rpm:


2) Pending vulnerabilities in SuSE Distributions and Workarounds:

  - Linux kernel
    Security bugs have been found in both the 2.2 and 2.4 kernel series
    of all currently supported SuSE Linux distributions (6.3-7.3), including
    the freshly appeared SuSE-7.3. These bugs allow a local attacker to gain
    root privileges, but there is no remote attack as of now.
    As a temporary workaround, it is possible for experienced users of
    linux-like systems to disable all setuid bits from all files in the
    installed system using a find command with a -exec option.

    We are currently in the process of testing the update kernels of both
    2.2 (2.2.19) and 2.4 (2.4.13) series to make sure that these update
    kernels will have the same level of stability and robustness as expected
    from SuSE linux systems. The official kernel rpm packages will be
    announced in a SuSE Security announcement during the second half of
    this week. In the meanwhile, the directory contains the preliminary
    update packages for testing (2.2.19 packages will be available shortly).
    Please proceed with the update as described in
    and report any problems that you may find to

  - openssh
    After stabilizing the openssh package, updates for the distributions
    6.4-7.2 are currently being prepared. The update packages fix a security
    problem related to the recently discovered problems with source ip
    based access restrictions in a user's ~/.ssh/authorized_keys2 file.
    The packages will appear shortly on our ftp servers. Please note that
    packages for the distributions 6.3 and up including 7.0 containing
    cryptographic software are located on the German ftp server,
    all other packages can be found on at the usual location.

  - htdig (ht://Dig)
    htdig, a powerful indexing and information gathering tool for a webserver,
    has been found vulnerable to a weakness where commandline options can
    be passed on to the cgi program as a result of weak runtime environment
    checking. The security announcement by Thomas Biege is waiting for the
    update packages to reach the ftp-server (currently transferring).

  Please continue to watch the suse-security-announce mailing list for
  new security announcements.


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


Version: 2.6.3i
Charset: noconv


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