Articles / SuSE: local privilege escal…

SuSE: local privilege escalation in shadow/login

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. 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. Fixed packages are available from ftp.suse.com.
-----BEGIN PGP SIGNED MESSAGE-----

______________________________________________________________________________

                        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:

    SuSE-7.3
    ftp://ftp.suse.com/pub/suse/i386/update/7.3/a1/shadow-20000902-144.i386.rpm
      9380496a4a248aeac73d7136de381348
    source rpm:
    ftp://ftp.suse.com/pub/suse/i386/update/7.3/zq1/shadow-20000902-144.src.rpm
      b595cea811bb92aa895974aee2fd5968

    SuSE-7.2
    ftp://ftp.suse.com/pub/suse/i386/update/7.2/a1/shadow-20000902-145.i386.rpm
      18e33d4b728b49403c2679c560b52f06
    source rpm:
    ftp://ftp.suse.com/pub/suse/i386/update/7.2/zq1/shadow-20000902-145.src.rpm
      0d9fb9cec79cdd4671306658a103fc6b

    SuSE-7.1
    ftp://ftp.suse.com/pub/suse/i386/update/7.1/a1/shadow-20000902-145.i386.rpm
      a5b2177d66048f988249e0acbc9648bf
    source rpm:
    ftp://ftp.suse.com/pub/suse/i386/update/7.1/zq1/shadow-20000902-145.src.rpm
      4525572bf268b73004774a25d7f5de2a

    SuSE-7.0
    ftp://ftp.suse.com/pub/suse/i386/update/7.0/a1/shadow-19990827-170.i386.rpm
      2be3765b08ce9d94abbd4932dbe3f39b
    source rpm:
    ftp://ftp.suse.com/pub/suse/i386/update/7.0/zq1/shadow-19990827-170.src.rpm
      97935450371dde96cb92134ab8596b85

    SuSE-6.4
    ftp://ftp.suse.com/pub/suse/i386/update/6.4/a1/shadow-19990827-145.i386.rpm
      c6d07aa8662e00d501f9fbb9d57f71bb
    source rpm:
    ftp://ftp.suse.com/pub/suse/i386/update/6.4/zq1/shadow-19990827-145.src.rpm
      79d9e99e67fcd23d64508eafe5070b36

    SuSE-6.3
    ftp://ftp.suse.com/pub/suse/i386/update/6.3/a1/shadow-19990827-145.i386.rpm
      82c4466697251685c5f1fa733c0ad4e2
    source rpm:
    ftp://ftp.suse.com/pub/suse/i386/update/6.3/zq1/shadow-19990827-145.src.rpm
      bac32336670e134146af62886e3d477e



    Sparc Platform:

    SuSE-7.1
    ftp://ftp.suse.com/pub/suse/sparc/update/7.1/a1/shadow-20000902-92.sparc.rpm
      3e63326bd5dd2dd3e9d8175b6db918e0
    source rpm:
    ftp://ftp.suse.com/pub/suse/sparc/update/7.1/zq1/shadow-20000902-92.src.rpm
      c95b2761cc4d9b417394a550d43716ca

    SuSE-7.0
    ftp://ftp.suse.com/pub/suse/sparc/update/7.0/a1/shadow-19990827-2.sparc.rpm
      5ce1d42bb0e5a6677666390b9980de5d
    source rpm:
    ftp://ftp.suse.com/pub/suse/sparc/update/7.0/zq1/shadow-19990827-2.src.rpm
      622dc8e8c6d6bf90f09d79b144a20533



    AXP Alpha Platform:

    SuSE-7.1
    ftp://ftp.suse.com/pub/suse/axp/update/7.1/a1/shadow-20000902-88.alpha.rpm
      ed882226bcb5241e105fb0f6466bf476
    source rpm:
    ftp://ftp.suse.com/pub/suse/axp/update/7.1/zq1/shadow-20000902-88.src.rpm
      b70743683ca521d66be357b90baff035

    SuSE-7.0
    ftp://ftp.suse.com/pub/suse/axp/update/7.0/a1/shadow-19990827-74.alpha.rpm
      778ebfcaacc9087e6c781f6a10a68a75
    source rpm:
    ftp://ftp.suse.com/pub/suse/axp/update/7.0/zq1/shadow-19990827-74.src.rpm
      68d957bf5d0cc942e12501056d05f0bd

    SuSE-6.4
    ftp://ftp.suse.com/pub/suse/axp/update/6.4/a1/shadow-19990827-74.alpha.rpm
      e7646c335fa009506535412daf344480
    source rpm:
    ftp://ftp.suse.com/pub/suse/axp/update/6.4/zq1/shadow-19990827-74.src.rpm
      3d748914265b37b15b42687e5ff87945

    SuSE-6.3
    ftp://ftp.suse.com/pub/suse/axp/update/6.3/a1/shadow-19990827-74.alpha.rpm
      c1cb80bb6d7a15a445550c739ced029b
    source rpm:
    ftp://ftp.suse.com/pub/suse/axp/update/6.3/zq1/shadow-19990827-74.src.rpm
      0b05d59fffc9ff8bd1cb922df7a84fac



    PPC Power PC Platform:

    SuSE-7.1
    ftp://ftp.suse.com/pub/suse/ppc/update/7.1/a1/shadow-20000902-61.ppc.rpm
      a1dbc8bb966db28469fabe583d157bed
    source rpm:
    ftp://ftp.suse.com/pub/suse/ppc/update/7.1/zq1/shadow-20000902-61.src.rpm
      2b2f0fbcb842149cb095fff125f54279

    SuSE-7.0
    ftp://ftp.suse.com/pub/suse/ppc/update/7.0/a1/shadow-19990827-182.ppc.rpm
      d55986fc84158f06dcbfea0c7812037f
    source rpm:
    ftp://ftp.suse.com/pub/suse/ppc/update/7.0/zq1/shadow-19990827-182.src.rpm
      dc84f0301b4a4daeae1fb6465f0d16c1

    SuSE-6.4
    ftp://ftp.suse.com/pub/suse/ppc/update/6.4/a1/shadow-19990827-182.ppc.rpm
      3d7e644c70e6d98944ff623b24bbfde0
    source rpm:
    ftp://ftp.suse.com/pub/suse/ppc/update/6.4/zq1/shadow-19990827-182.src.rpm
      646985dc82d9845832db6863fba9442d

______________________________________________________________________________

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
    ftp://ftp.suse.com/pub/people/mantel/next/ contains the preliminary
    update packages for testing (2.2.19 packages will be available shortly).
    Please proceed with the update as described in
    http://www.suse.de/de/support/security/2001_018_kernel_txt.txt
    and report any problems that you may find to feedback@suse.de.

  - 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 ftp.suse.de,
    all other packages can be found on ftp.suse.com 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 
       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 
       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 "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-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
                .

    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 

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