SuSE Security Announcement: Slapper worm (SuSE-SA:2002:033)

19 Sep 2002


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______________________________________________________________________________

                        SuSE Security Announcement

        Package:                openssl/Slapper worm
        Announcement-ID:        SuSE-SA:2002:033
        Date:                   Thu Sep 19 2002
        Affected products:      7.0, 7.1, 7.2, 7.3, 8.0
				SuSE Linux Database Server,
				SuSE eMail Server III,
				SuSE eMail Server 3.1,
				SuSE Linux Enterprise Server,
				SuSE Linux Firewall on CD,
				SuSE Linux Enterprise Server 7
				SuSE Linux Office Server
        Vulnerability Type:     buffer overflow
        Severity (1-10):        9
        SuSE default package:   yes
	Cross References:	CVE CAN-2002-0655, CAN-2002-0656,
				CAN-2002-0659, CERT CA 2002-23,
				SuSE-SA:2002:027

    Content of this advisory:
	1) vulnerabilities in openssl libraries; Slapper worm
        2) pending vulnerabilities, solutions, workarounds
        3) standard appendix (further information)

______________________________________________________________________________

1)  problem description, brief discussion, solution, upgrade information

    This advisory is issued in an attempt to clarify any issues
    surrounding the recently discovered Apache/mod_ssl worm.

    On July 30, we released a security advisory concerning vulnerabilities
    in OpenSSL, including a buffer overflow in the SSL code. This
    vulnerability (CVE CAN-2002-0656, also discussed in CERT Advisory
    http://www.cert.org/advisories/CA-2002-23.html) is currently being
    exploited by a worm called Slapper, propagating through Apache's
    mod_ssl module.
    
    It is worth noting that even though the worm infects Apache through
    mod_ssl, this is not a vulnerability in mod_ssl or Apache, but in
    the OpenSSL library used by mod_ssl.

    This also means that Apache may not be the only service vulnerable
    to an attack via the SSL bug. Similar exploits may be possible
    against cyrus-imapd, sendmail with TLS support, or sslwrap-enabled
    services.

    As a workaround, it is also possible to disable SSLv2 in mod_ssl
    (as described in our previous advisory SuSE-SA:2002:027;
    http://www.suse.com/de/security/2002_027_openssl.html), but you
    should be aware that this does not protect other SSL based servers
    that may be running on your machine.


    We have received numerous inquiries from SuSE users on whether the
    update packages provided by SuSE as part of SA:2002:027 fix this bug
    even though they do not contain the latest OpenSSL version recommended
    in various advisories.

    To clarify this, we would like to state that these packages DO FIX
    the bug exploited by the Slapper worm. Following established policy,
    we did this by applying a source code patch instead of upgrading to
    a newer version, because the latter usually causes serious problems
    for many users (in particular, different versions of OpenSSL libraries
    are not always API compatible).


    However, it turns out that a number of packages were statically
    linked against OpenSSL libraries:

    mod_ssl (SuSE Linux 7.0):
    	We have released rebuilt mod_ssl packages linked against the
	most recent OpenSSL libraries.

	If you run mod_ssl on SuSE Linux 7.0, you must upgrade mod_ssl,
	too.

    sendmail-tls (SuSE Linux 7.1, 7.2, 7.3):
	Sendmail-tls, the SSL enabled version of sendmail, was linked
	statically against OpenSSL on SuSE 7.1, 7.2 and 7.3. The security
	impact of this problem is probably the same as with Apache and
	mod_ssl.

	We are releasing rebuilt packages linked against the most
	OpenSSL libraries.

	Sendmail-tls is not part of the default installation profile.

	If you are using sendmail-tls, we strongly recommend you upgrade
	to the latest packages provided on our FTP servers.

    openssh (SuSE Linux 7.1, 7.2 and 7.3):
        Ssh and sshd do not use any SSL functionality, and thus are not
	susceptible to the type of attack carried out by the Slapper worm.

	To date, we are not aware of any way to exploit them. We nevertheless
	recommend to upgrade to the latest versions provided on our FTP site.

    freeswan (SuSE Linux 7.1, 7.2):
    	FreeSWAN includes a utility named fswcert for creating and
	manipulating X.509 certificates, which is also linked statically
	against libcrypto.

	To date, we are not aware of any way to exploit them. We
	nevertheless recommend to upgrade to the latest versions provided
	on our FTP site as soon as they become available (2002 Sep 20).

______________________________________________________________________________

2)  Pending vulnerabilities in SuSE Distributions and Workarounds:
   
    mod_php4:
    	we are preparing an update of mod_php4 addressing various
	vulnerabilities that have been published recently.

______________________________________________________________________________

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 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 <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.
       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-subscribe@suse.com>.

    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
                <suse-security-announce-subscribe@suse.com>.

    For general information or the frequently asked questions (faq)
    send mail to:
        <suse-security-info@suse.com> or
        <suse-security-faq@suse.com> respectively.

    =====================================================================
    SuSE's security contact is <security@suse.com> or <security@suse.de>.
    The <security@suse.de> 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 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 <security@suse.de>
pub  1024D/9C800ACA 2000-10-19 SuSE Package Signing Key <build@suse.de>

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Olaf Kirch

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