Articles / SuSE: xmcd local privilege …

SuSE: xmcd local privilege escalation

Cda, a setuid commandline part of xmcd, a X11/Motif audio CD player by Ti Kan <ti@amb.org>, was found vulnerable by a link attack and some buffer overflows. These bugs could be exploited by an adversary, who has access to the system, to overwrite files or gain higher privileges. As a temporary fix, just remove the setuid bit from cda or let just trusted users execute cda. Don't forget to add these changes to your /etc/permissions.local file. Users of SuSE 7.2 with permissions.secure or permissions.paranoid activated are safe, because setuid is already removed. Updated RPMs of the xmcd package can be found on ftp.suse.com.
-----BEGIN PGP SIGNED MESSAGE-----

______________________________________________________________________________

                        SuSE Security Announcement

        Package:                xmcd
        Announcement-ID:        SuSE-SA:2001:025
        Date:                   Friday, Aug 3rd 2001 18:30 MEST
        Affected SuSE versions: (6.0, 6.1, 6.2,) 6.3, 6.4, 7.0, 7.1, 7.2
        Vulnerability Type:     local privilege escalation
        Severity (1-10):        4
        SuSE default package:   no
        Other affected systems: yes

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

    Cda, a setuid commandline part of xmcd, a X11/Motif audio CD player by
    Ti Kan , was found vulnerable by a link attack and some
    bufferoverflows.
    These bugs could be exploited by an adversary, who has access to the
    system, to overwrite files or gain higher privileges.

    As a temporary fix, just remove the setuid bit from cda:
       /bin/chmod 755 /usr/X11R6/bin/cda
    or let just trusted users execute cda:
       /bin/chown root.trusted /usr/X11R6/bin/cda
       /bin/chmod 4750 /usr/X11R6/bin/cda
    Don't forget to add these changes to your /etc/permissions.local file
    Users of SuSE 7.2 with permissions.secure or permissions.paranoid
    activated are safe, because setuid is already removed.

    Thanks to Paul Starzetz , who reportes the link attack
    and to Ti Kan , the author of xmcd, for his fast response
    and help.

    New RPMs can be found at the following places.

    i386 Intel Platform:

    SuSE-7.2
    ftp://ftp.suse.com/pub/suse/i386/update/7.2/snd2/xmcd-2.6-195.i386.rpm
      2e11b84704ab44c61b04f2e9bfde1371
    source rpm:
    ftp://ftp.suse.com/pub/suse/i386/update/7.2/zq1/xmcd-2.6-195.src.rpm
      2d934ab9662d3aee69041d2118ead682

    SuSE-7.1
    ftp://ftp.suse.com/pub/suse/i386/update/7.1/snd2/xmcd-3.0.2-2.i386.rpm
      dbeb8ddbf8e435d54930d1acef85cfe6
    source rpm:
    ftp://ftp.suse.com/pub/suse/i386/update/7.1/zq1/xmcd-3.0.2-2.src.rpm
      38c24dc21572cfefc3f678bb534457e7

    SuSE-7.0
    ftp://ftp.suse.com/pub/suse/i386/update/7.0/snd2/xmcd-3.0.2-2.i386.rpm
      55ef501823f33033d6e649a6df872cf7
    source rpm:
    ftp://ftp.suse.com/pub/suse/i386/update/7.0/zq1/xmcd-3.0.2-2.src.rpm
      6ba4db1799355aef6fe5202164338b5d

    SuSE-6.4
    ftp://ftp.suse.com/pub/suse/i386/update/6.4/snd2/xmcd-3.0.2-2.i386.rpm
      8f0dd51c4ed7b9dabd554793a98504f3
    source rpm:
    ftp://ftp.suse.com/pub/suse/i386/update/6.4/zq1/xmcd-3.0.2-2.src.rpm
      076151818b5054d40d955bdf060f601b

    SuSE-6.3
    ftp://ftp.suse.com/pub/suse/i386/update/6.3/snd2/xmcd-3.0.2-2.i386.rpm
      a53b36543b555ad435eebede89324227
    source rpm:
    ftp://ftp.suse.com/pub/suse/i386/update/6.3/zq1/xmcd-3.0.2-2.src.rpm
      4274da4334b67a04d10f2ade67305679


    Sparc Platform:

    SuSE-7.1
    ftp://ftp.suse.com/pub/suse/sparc/update/7.1/snd2/xmcd-3.0.2-0.sparc.rpm
      b6fb5c9a71c578866fcefd978c3dd469
    source rpm:
    ftp://ftp.suse.com/pub/suse/sparc/update/7.1/zq1/xmcd-3.0.2-0.src.rpm
      0c6a783486669cc57b35575edabfd6b4

    SuSE-7.0
    ftp://ftp.suse.com/pub/suse/sparc/update/7.0/snd2/xmcd-3.0.2-0.sparc.rpm
      b7ae66325a2875e97d28ec7b0152dc35
    source rpm:
    ftp://ftp.suse.com/pub/suse/sparc/update/7.0/zq1/xmcd-3.0.2-0.src.rpm
      836be977435960908c77d753c47084fb


    AXP Alpha Platform:

    SuSE-7.1
    ftp://ftp.suse.com/pub/suse/axp/update/7.1/snd2/xmcd-3.0.2-2.alpha.rpm
      b2c1652b694655fbd5635b455355fe59
    source rpm:
    ftp://ftp.suse.com/pub/suse/axp/update/7.1/zq1/xmcd-3.0.2-2.src.rpm
      78af000c592f274fa78019da47463c2f

    SuSE-7.0
    ftp://ftp.suse.com/pub/suse/axp/update/7.0/snd2/xmcd-3.0.2-3.alpha.rpm
      67a11e69a66ee0e5c36f8bd4c67d1e49
    source rpm:
    ftp://ftp.suse.com/pub/suse/axp/update/7.0/zq1/xmcd-3.0.2-3.src.rpm
      17fa48bdd3b20c263c09578391a6da2e

    SuSE-6.4
    ftp://ftp.suse.com/pub/suse/axp/update/6.4/snd2/xmcd-3.0.2-4.alpha.rpm
      c0ee2188da89b7756e143495b2947a41
    source rpm:
    ftp://ftp.suse.com/pub/suse/axp/update/6.4/zq1/xmcd-3.0.2-4.src.rpm
      39acbbe4d54c671f925b342091f4b994

    SuSE-6.3
    ftp://ftp.suse.com/pub/suse/axp/update/6.3/snd2/xmcd-3.0.2-4.alpha.rpm
      5480828717020d146da0d9413ab8fab8
    source rpm:
    ftp://ftp.suse.com/pub/suse/axp/update/6.3/zq1/xmcd-3.0.2-4.src.rpm
      5a5d4af61d0b4ce629ad19a06d8dcd2b


    PPC PowerPC Platform:

    SuSE-7.1
    ftp://ftp.suse.com/pub/suse/ppc/update/7.1/snd2/xmcd-3.0.2-3.ppc.rpm
      3292bb4e6410aa1d5268fca8540024af
    source rpm:
    ftp://ftp.suse.com/pub/suse/ppc/update/7.1/zq1/xmcd-3.0.2-3.src.rpm
      f6ddf546fa6562ac02d7b56fde58ea11

    SuSE-7.0
    ftp://ftp.suse.com/pub/suse/ppc/update/7.0/snd2/xmcd-3.0.2-3.ppc.rpm
      4bd49ef46dbf59a9155af6322a4a34c3
    source rpm:
    ftp://ftp.suse.com/pub/suse/ppc/update/7.0/zq1/xmcd-3.0.2-3.src.rpm
      67762f89ddeec6eb4a99a5919ad35927

    SuSE-6.4
    ftp://ftp.suse.com/pub/suse/ppc/update/6.4/snd2/xmcd-3.0.2-3.ppc.rpm
      295884a4eb13da364b6a8f0b3ae2f69d
    source rpm:
    ftp://ftp.suse.com/pub/suse/ppc/update/6.4/zq1/xmcd-3.0.2-3.src.rpm
      185fd215007d17348e11982bbc2c2ad1


______________________________________________________________________________

2)  Pending vulnerabilities in SuSE Distributions and Workarounds:

  - openssl
    Currently we check are checking the dependencies of openssl to other
    dynamic or static linked applications on SuSE Linux. An announcement
    will be released soon.

  - dqs
    dex@raza-mexicana.org has found an exploitable buffer overflow bug in
    the dsh program from the dqs package on SuSE Linux distributions.
    To workaround the problem, do "chmod -s /usr/bin/dsh" and change the
    files /etc/permissions* to reflect the change. If you do not need the
    dqs package, then deinstall it (rpm -e dqs).
    Packages for most of the supported SuSE Linux distributions are
    available at the usual location ftp://ftp.suse.com/pub/suse//
    for download and installation/update. Do not forget to change the files
    /etc/permissions* to remove the suid-bit from the dsh program. Please
    note that we will not issue a dedicated security announcement for this
    specific bug.


  - pcp
    Paul Starzetz discovered a security weakness in the setuid root program
    /usr/share/pcp/bin/pmpost. The common library in pcp trusts the
    environment that has been supplied by the user, regardless of privileged
    execution or not. By consequence, a user can specify the configuration
    file and therefore write to files owned by root. The problem is not based
    on insecurely following symlinks as stated by Paul Starzetz.
    The pcp package is not installed by default in SuSE Linux distributions.
    We have provided update packages for the SuSE Linux distributions version
    7.1 and 7.2 that remove the setuid bit from the pmpost binary. Versions
    before SuSE-7.1 were not affected because the setuid bit was not set.
    We thank Keith Owens and Mark Goodwin from Silicon Graphics for responding
    quickly and for publishing a new version of the pcp package which will
    be included in future releases of the SuSE Linux distribution. For more
    information see the /usr/share/doc/packages/pcp directory of your SuSE
    Linux installation after installing the update package, or go to
    obtained from http://oss.sgi.com/projects/pcp/download .
    Please note that there will not be a dedicated security announcement
    for this specific bug.


  - fetchmail (fetchml)
    New fetchmail packages are available on the ftp server. The packages
    cure a buffer overflow that can be exploited by sending a victim a
    specially designed email, waiting for the victim's fetchmail program
    to pick up the email. We are preparing a security announcement for this
    problem.


  - openssh
    update packages for the openssh package after (and including) SuSE-6.4
    are available on our ftp servers ftp.suse.de (for < 7.1) or
    ftp.suse.com (for >= 7.1). We are currently checking for a non-security
    related irregularity in sshd's behaviour under faulty setup conditions.


  - exim
    SuSE Linux distributions do not contain the exim Mail Transport Agent
    (See http://www.exim.org/ for details) and are therefore not susceptible
    to the recently found security-related bugs.


  - webmin
    SuSE Linux distributions do not contain the webmin administration
    web frontend (See http://www.webmin.org/ for details) and are therefore
    not vulnerable to the recently found security-related problems in the
    software.


______________________________________________________________________________

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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Bye,
     Thomas
-- 
  Thomas Biege, SuSE GmbH, Schanzaeckerstr. 10, 90443 Nuernberg
  E@mail: thomas@suse.de      Function: Security Support & Auditing
  "lynx -source http://www.suse.de/~thomas/contact/thomas.asc | pgp -fka"
  Key fingerprint = 51 AD B9 C7 34 FC F2 54  01 4A 1C D4 66 64 09 84
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