mhe18/cve_projectCVE-2016-1240 exploit and patch
1.Install Tomcat 7 on the virtual machine
sudo apt-get install tomcat7
2.If the first step is failed,set JDK_DIRS="/usr/lib/jvm/java-8-oracle" and add the statements “export JAVA_HOME=/usr/lib/jvm/java-8-oracle” and “export CATALINA_HOME=/usr/share/tomcat7”. Then reinstall Tomcat 7
3.Set up an initial password for the Tomcat user
sudo passwd tomcat7
4.Assign login shell for the Tomcat user
sudo usrmod -s /bin/bash tomcat7
5.Establish the Tomcat 7 user shell
ssh tomcat7@localhost
1.Create the exploit scripts attack.sh at /tmp through Tomcat7 user shell and then make the exploit codes executable
touch attack.sh
chmod +x attack.sh
2.Run the exploit code
./attack.sh
3.Restart the Tomcat server to check the attack result.
sudo service tomcat7 restart
4.Check the ID of user
id
Then the attack should be successful and the euid should be 0 which is root.
# Run the catalina.sh script as a daemon
set +e
touch "$CATALINA_PID" "$CATALINA_BASE"/logs/catalina.out
chown $TOMCAT7_USER "$CATALINA_PID" "$CATALINA_BASE"/logs/catalina.out
start-stop-daemon --start -b -u "$TOMCAT7_USER" -g "$TOMCAT7_GROUP" \
-c "$TOMCAT7_USER" -d "$CATALINA_TMPDIR" -p "$CATALINA_PID" \
-x /bin/bash -- -c "$AUTHBIND_COMMAND $TOMCAT_SH"
status="$?"
set +a -e
return $status
The code above is key of esclating privilege. As it runs with root privilege, it can do anything we want. Then we need to change the owner of catalina.out to user of tomcat7. After we reboot the Tomcat, we are able to read the file which catalina points to.
Specifically, when the tomcat restart, it will change the owner of the catalina.out to user of Tomcat, and the restart is invoked by the linux init. By taking advantage of Linux init, we can use symlink to change the owener of any file to the user of tomcat. If we symlink catalina.out to any file, we could operate any file in the system with the privilege root which given by the catalina.out. This is typical exploitation of DLL hijack.