righettod/log4shell-payload-grabber

Tool to try to retrieve the java class used as dropper for the RCE in the context of log4shell vulnerability.

Objective

Tool to try to retrieve the java class used as dropper for the RCE.

The tool was tested again the following attacks kit:

• JNDI-Exploit-Kit.
• JNDIExploit.
• Rogue-JNDI.

It is a IntelliJ IDEA project.

Requirements

Java 8 is required for compilation and execution because classes only present in this JDK are used for RMI information retieval.

Need Maven3+ for the building.

Usage

$ java -jar get-payload.jar
[+] Missing LDAP/LDAPS/RMI URL or SER file!
     URL: rmi://127.0.0.1:9997/gchero [--pause]
          ldap://127.0.0.1:9998/gcherG
SER file: 899f0d32098d4f3b8d54ffa21fe9b0b6.ser
1) For RMI, if a second parameter, named '--pause', is specified then
the program wait the user press a key before to end the program allowing taking a heap dump
of the JVM process to capture the loaded remote object.
2) If a SER (serialized java object) file is passed then the program will load it
and wait the user press a key before to end the program allowing taking a heap dump like for RMI.

Full demonstration in this video.

Use the following command to directly extract the download URL of the class when it is available:

$ java -jar get-payload.jar "ldap://127.0.0.1:1389/Basic/TomcatMemshell" | grep "Direct URL" | cut -d" " -f10
http://127.0.0.1:8080/com.feihong.ldap.template.TomcatMemshellTemplate.class

For RMI, a second optional parameter named --pause, can be used to add a "virtual" break point allowing to perform a memory dump of the JVM tool process in order to capture loaded remote object:

Once created, the memory dump can be analyzed with different tools like for example jhat:

Compilation

Use the script named package.sh and the binary jar file will be present in the target folder.

Exploit class decompilation

The following tools can be used to achieve this task:

• GUI: http://java-decompiler.github.io/
• CMD: https://github.com/intoolswetrust/jd-cli

log4shell-payload-grabber's Issues

Serializated object loading for inspection

Add a main class allowing to load a serialized class from a SER file and set of "virtual" break point (like for RMI) to allow to dump the JVM process memory.