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CA-94:08                     CERT Advisory
                            April 14, 1994
                         ftpd Vulnerabilities
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The CERT Coordination Center has received information concerning two
vulnerabilities in some ftpd implementations.  The first is a
vulnerability with the SITE EXEC command feature of the FTP daemon
(ftpd) found in versions of ftpd that support the SITE EXEC feature.
This vulnerability allows local or remote users to gain root access.
The second vulnerability involves a race condition found in the ftpd
implementations listed in Section I. below.  This vulnerability allows
local users to gain root access.

Sites using these implementations are vulnerable even if they do not
support anonymous FTP.

As these vulnerabilities are widely known, we strongly recommend that any
site running a version of ftpd listed below take steps to immediately
upgrade or disable their FTP daemon.  Also potentially at risk are
sites whose ftpd is derived from the DECWRL or wuarchive ftpd code
containing the SITE EXEC feature.

For additional information or assistance, contact the developer or
vendor of your ftpd implementation.

If we receive additional information relating to this advisory, we
will place it, along with any clarifications, in a README file
available by anonymous FTP from info.cert.org (e.g.,
/pub/cert_advisories/CA-94:xx.README).  We encourage you to check our
README files regularly for updates on advisories that relate to your
site.

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I.   Description

     There is a vulnerability in the SITE EXEC command feature of
     ftpd that allows any remote or local user to obtain root access.
     There is also a vulnerability due to a race condition in these
     implementations. 

     Versions known to be vulnerable to these problems are:
          wuarchive ftpd versions 2.0-2.3 (version 2.2 patched the
               SITE EXEC problem, but not the race condition)
          DECWRL ftpd versions prior 5.93
          BSDI ftpd version 1.1 prior to patch 5

     The SITE EXEC vulnerability affects your ftpd only if the SITE
     EXEC command feature has been explicitly activated at your site.
     This functionality is not activated by default.  Sites that have
     not enabled the SITE EXEC feature are not at risk from this
     vulnerability.  However, since the race condition does not have
     an easily applied workaround, CERT recommends that you upgrade to
     one of the versions listed below.

II.  Impact

     Anyone (remote or local) can gain root access on a host running a
     vulnerable FTP daemon.  Support for anonymous FTP is not required
     to exploit this vulnerability.


III. Solution

     Affected sites can solve both of these problems by upgrading to
     the latest version of ftpd. These versions are listed below. Be
     certain to verify the checksum information to confirm that you
     have retrieved a valid copy.

     If you cannot install the new version in a timely manner, you
     should disable FTP service until you have corrected this problem.
     It is not sufficient to disable anonymous FTP.  You must disable
     the FTP daemon.

     For wuarchive ftpd, you can obtain version 2.4 via anonymous
     FTP from wuarchive.wustl.edu, in the "/packages/wuarchive-ftpd"
     directory.  If you are currently running version 2.3, a patch
     file is available.


                        BSD        SVR4         
     File               Checksum   Checksum    MD5 Digital Signature
     -----------------  --------   ---------   --------------------------------
     wu-ftpd-2.4.tar.Z  38213  181  20337 362  cdcb237b71082fa23706429134d8c32e
     patch_2.3-2.4.Z    09291    8  51092  16  5558a04d9da7cdb1113b158aff89be8f

     For DECWRL ftpd, sites can obtain version 5.93 via anonymous FTP
     from gatekeeper.dec.com in the "/pub/misc/vixie" directory.

                        BSD        SVR4         
     File               Checksum   Checksum    MD5 Digital Signature
     -----------------  --------   --------- --------------------------------
     ftpd.tar.gz        38443  60  1710 119  ae624eb607b4ee90e318b857e6573500

     For BSDI systems, patch 005 should be applied to version 1.1 of
     the BSD/386 software.  You can obtain the patch file via
     anonymous FTP from ftp.bsdi.com in the "/bsdi/patches-1.1"
     directory.

                        BSD        SVR4         
     File               Checksum   Checksum    MD5 Digital Signature
     -----------------  --------   ---------   --------------------------------
     BU110-005          35337 272  54935 543   1f454d4d9d3e1397d1eff0432bd383cf

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The CERT Coordination Center wishes to thank Neil Woods and Karl Strickland 
for finding and reporting the wustl FTP daemon bug.  We also wish to thank 
Bryan O'Connor and Chris Myers of Washington University in St. Louis,
Paul Vixie of Vixie Enterprises, and Tony Sanders of BSDI for their 
invaluable assistance in resolving this problem.
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If you believe that your system has been compromised, contact the CERT
Coordination Center or your representative in the Forum of Incident
Response and Security Teams (FIRST).

If you wish to send sensitive incident or vulnerability information to 
CERT via electronic mail, CERT strongly advises that the e-mail be encrypted.
CERT can support a shared DES key, PGP (public key available via
anonymous FTP on info.cert.org), or PEM (contact CERT for details).

Internet E-mail: cert@cert.org
Telephone: 412-268-7090 (24-hour hotline)
           CERT personnel answer 8:30 a.m.-5:00 p.m. EST(GMT-5)/EDT(GMT-4),
           and are on call for emergencies during other hours.

CERT Coordination Center
Software Engineering Institute
Carnegie Mellon University
Pittsburgh, PA 15213-3890

Past advisories, information about FIRST representatives, and other
information related to computer security are available via anonymous
FTP from info.cert.org.

