oss-security - CVE-2014-0476 chkrootkit vulnerability

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Message-ID: <538EDDF1.4080302@debian.org>
Date: Wed, 04 Jun 2014 10:50:57 +0200
From: Giuseppe Iuculano <iuculano@...ian.org>
To: oss-security@...ts.openwall.com
Subject: CVE-2014-0476 chkrootkit vulnerability

Hi,

Thomas Stangner reported the following chkrootkit vulnerability.

We assigned CVE-2014-0476

Cheers,
Giuseppe

-------- Original Message --------
Subject: Serious chkrootkit vulnerability
Date: Sun, 25 May 2014 00:53:00 +0200
From: Thomas Stangner <thomas.stangner@...zner.de>
Organization: Hetzner Online AG
To: team@...urity.debian.org

Hi,

we just found a serious vulnerability in the chkrootkit package, which
may allow local attackers to gain root access to a box in certain
configurations (/tmp not mounted noexec).

The vulnerability is located in the function slapper() in the
shellscript chkrootkit:

#
# SLAPPER.{A,B,C,D} and the multi-platform variant
#
slapper (){
   SLAPPER_FILES="${ROOTDIR}tmp/.bugtraq ${ROOTDIR}tmp/.bugtraq.c"
   SLAPPER_FILES="$SLAPPER_FILES ${ROOTDIR}tmp/.unlock ${ROOTDIR}tmp/httpd \
   ${ROOTDIR}tmp/update ${ROOTDIR}tmp/.cinik ${ROOTDIR}tmp/.b"a
   SLAPPER_PORT="0.0:2002 |0.0:4156 |0.0:1978 |0.0:1812 |0.0:2015 "
   OPT=-an
   STATUS=0
   file_port=

   if ${netstat} "${OPT}"|${egrep} "^tcp"|${egrep} "${SLAPPER_PORT}">
/dev/null 2>&1
      then
      STATUS=1
      [ "$SYSTEM" = "Linux" ] && file_port=`netstat -p ${OPT} | \
         $egrep ^tcp|$egrep "${SLAPPER_PORT}" | ${awk} '{ print  $7 }' |
tr -d :`
   fi
   for i in ${SLAPPER_FILES}; do
      if [ -f ${i} ]; then
         file_port=$file_port $i
         STATUS=1
      fi
   done
   if [ ${STATUS} -eq 1 ] ;then
      echo "Warning: Possible Slapper Worm installed ($file_port)"
   else
      if [ "${QUIET}" != "t" ]; then echo "not infected"; fi
         return ${NOT_INFECTED}
   fi
}

The line 'file_port=$file_port $i' will execute all files specified in
$SLAPPER_FILES as the user chkrootkit is running (usually root), if
$file_port is empty, because of missing quotation marks around the
variable assignment.

Steps to reproduce:

- Put an executable file named 'update' with non-root owner in /tmp (not
mounted noexec, obviously)
- Run chkrootkit (as uid 0)

Result: The file /tmp/update will be executed as root, thus effectively
rooting your box, if malicious content is placed inside the file.

If an attacker knows you are periodically running chkrootkit (like in
cron.daily) and has write access to /tmp (not mounted noexec), he may
easily take advantage of this.

Suggested fix: Put quotation marks around the assignment.

file_port="$file_port $i"

I will also try to contact upstream, although the latest version of
chkrootkit dates back to 2009 - will have to see, if I reach a dev there.

Keep up the good work,

Cheers,
Thomas

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