Articles / SuSE: local privilege escal…

SuSE: local privilege escalation and remote command execution in lprng/html2ps

The lprng package contains the "runlpr" program which allows the lp user to execute the lpr program as root. Local attackers can pass certain commandline arguments to lpr running as root, fooling it to execute arbitrary commands as root. This has been fixed. Additionally, the html2ps printfilter, which is installed as part of the LPRng print system, allowed remote attackers to execute arbitrary commands in the context of the lp user. These two issues combined allow attackers to mount a remote root attack. Fixed packages are available from ftp.suse.com.
-----BEGIN PGP SIGNED MESSAGE-----

______________________________________________________________________________

                        SuSE Security Announcement

        Package:                lprng, html2ps
        Announcement-ID:        SuSE-SA:2002:040
        Date:                   Thu Oct 31 11:00:10 MET 2002
        Affected products:      7.0, 7.1, 7.2, 7.3, 8.0, 8.1
                                SuSE eMail Server III, 3.1
                                SuSE Firewall on CD/Admin host
                                SuSE Firewall on CD 2
                                SuSE Linux Connectivity Server
                                SuSE Linux Enterprise Server 7
                                SuSE Linux Office Server
        Vulnerability Type:     local privilege escalation,
                                remote command execution
        Severity (1-10):        6
        SuSE default package:   yes
        Cross References:       -

    Content of this advisory:
        1) security vulnerability resolved: Local privilege escalation in
            runlpr (from lprng package) and remote command execution
            via html2ps printfilter.
           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

    The lprng package contains the "runlpr" program which allows the lp
    user to execute the lpr program as root. Local attackers can pass
    certain commandline arguments to lpr running as root, fooling it
    to execute arbitrary commands as root. This has been fixed.
    Note that this vulnerability can only be exploited if the attacker
    has previously gained access to the lp account.

    Additionally, the html2ps printfilter, which is installed as part of
    the LPRng print system, allowed remote attackers to execute arbitrary
    commands in the context of the lp user.

    These two issues combined allow attackers to mount a remote root attack.

    As a workaround, we recommend to uninstall the html2ps package, and
    restrict access to your print services to authorized hosts only.

    Access control to lpd is implemented by adding appropriate entries to the
    /etc/lpd.perms file. Please consult the lpd.perms(5) manpage, or add the
    single line

      DEFAULT REJECT

    to your /etc/lpd.perms file to deny access to everyone from the outside.


    Please download the update package for your distribution and verify its
    integrity by the methods listed in section 3) of this announcement.
    Then, install the package using the command "rpm -Fhv file.rpm" to apply
    the update.
    Our maintenance customers are being notified individually. The packages
    are being offered to install from the maintenance web.

    i386 Intel Platform:

    SuSE-8.1
    ftp://ftp.suse.com/pub/suse/i386/update/8.1/rpm/i586/html2ps-1.0b3-458.i586.rpm
      c1990d8139e33176fb02745f3e5b0a05
    source rpm:
    ftp://ftp.suse.com/pub/suse/i386/update/8.1/rpm/src/html2ps-1.0b3-458.src.rpm
      f42f18d885dc2fe5701bc74812fd6ceb

    ftp://ftp.suse.com/pub/suse/i386/update/8.1/rpm/i586/lpdfilter-0.43-63.i586.rpm
      cc79a87fd8fcc9cf92356ab4863babc6
    source rpm:
    ftp://ftp.suse.com/pub/suse/i386/update/8.1/rpm/src/lpdfilter-0.43-63.src.rpm
      0ad433931936c4ba5a644de9104b3db4

    SuSE-8.0
    ftp://ftp.suse.com/pub/suse/i386/update/8.0/gra1/html2ps-1.0b3-456.i386.rpm
      c14c59d1f23575841a95f7d5eaf6f734
    source rpm:
    ftp://ftp.suse.com/pub/suse/i386/update/8.0/zq1/html2ps-1.0b3-456.src.rpm
      7ffd5b01e399ee427a0d3a16d15af4f1

    ftp://ftp.suse.com/pub/suse/i386/update/8.0/ap1/lpdfilter-0.42-155.i386.rpm
      dd04dd60c4c18b5711643f6334b97bfd
    source rpm:
    ftp://ftp.suse.com/pub/suse/i386/update/8.0/zq1/lpdfilter-0.42-155.src.rpm
      4d6b611c572d251f47c0b4cf8ab7a28d

    SuSE-7.3
    ftp://ftp.suse.com/pub/suse/i386/update/7.3/gra1/html2ps-1.0b3-457.i386.rpm
      28a1aee8dfedfff3eb348fc4ea4a8876
    source rpm:
    ftp://ftp.suse.com/pub/suse/i386/update/7.3/zq1/html2ps-1.0b3-457.src.rpm
      2765c61e39616199cbf5066d719280b3

    SuSE-7.2
    ftp://ftp.suse.com/pub/suse/i386/update/7.2/gra1/html2ps-1.0b1-432.i386.rpm
      1ab553d151c65505184353ae6e514db6
    source rpm:
    ftp://ftp.suse.com/pub/suse/i386/update/7.2/zq1/html2ps-1.0b1-432.src.rpm
      b71dba7782caeb01954b418e3ffdd6c2

    SuSE-7.1
    ftp://ftp.suse.com/pub/suse/i386/update/7.1/gra1/html2ps-1.0b1-431.i386.rpm
      1d9adfc7cc1e141f340b844f040bfe85
    source rpm:
    ftp://ftp.suse.com/pub/suse/i386/update/7.1/zq1/html2ps-1.0b1-431.src.rpm
      b1b29ff154fc13cb806dec49fc00ff81

    SuSE-7.0
    ftp://ftp.suse.com/pub/suse/i386/update/7.0/gra1/html2ps-1.0b1-428.i386.rpm
      7e0bd236c647cd70ba9b0274f7b5cf53
    source rpm:
    ftp://ftp.suse.com/pub/suse/i386/update/7.0/zq1/html2ps-1.0b1-428.src.rpm
      b60e012d057e428e6ade468d46afd4e5


    Sparc Platform:

    SuSE-7.3
    ftp://ftp.suse.com/pub/suse/sparc/update/7.3/gra1/html2ps-1.0b3-88.sparc.rpm
      b6c1c7399a041477ce0c321a9eda383b
    source rpm:
    ftp://ftp.suse.com/pub/suse/sparc/update/7.3/zq1/html2ps-1.0b3-88.src.rpm
      8102e2145e43fb6486cee5ccfc106c67


    AXP Alpha Platform:

    SuSE-7.0
    ftp://ftp.suse.com/pub/suse/axp/update/7.0/gra1/html2ps-1.0b1-328.alpha.rpm
      83967dc5d7dcf672c6dd902c125a3e81
    source rpm:
    ftp://ftp.suse.com/pub/suse/axp/update/7.0/zq1/html2ps-1.0b1-328.src.rpm
      e3851c0f69017811168213a707431467


    PPC Power PC Platform:

    SuSE-7.1
    ftp://ftp.suse.com/pub/suse/ppc/update/7.1/gra1/html2ps-1.0b1-303.ppc.rpm
      b9cb5de37503927812f767a0781bfc6a
    source rpm:
    ftp://ftp.suse.com/pub/suse/ppc/update/7.1/zq1/html2ps-1.0b1-303.src.rpm
      be58c62e270d5cbc2aa3395beae91009

    SuSE-7.0
    ftp://ftp.suse.com/pub/suse/ppc/update/7.0/gra1/html2ps-1.0b1-302.ppc.rpm
      a98f5628ae1068b3d7f20b83ace9bb77
    source rpm:
    ftp://ftp.suse.com/pub/suse/ppc/update/7.0/zq1/html2ps-1.0b1-302.src.rpm
      5a425dbc64f2e0f2a368ecb566c624eb


______________________________________________________________________________

2)  Pending vulnerabilities in SuSE Distributions and Workarounds:

    There is no additional information this time.

______________________________________________________________________________

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 un-installed 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 top-level 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 announcements 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 clear-text signature shows proof of the
    authenticity of the text.
    SuSE Linux AG 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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-- 
~
~ perl self.pl
~ $_='print"\$_=\47$_\47;eval"';eval
~ krahmer@suse.de - SuSE Security Team
~
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