CBC padding oracle demo application. Requires Python3, requests, pycrypto and flask.

The easiest way to run this application, is to setup a virtual environment and then install the required packages. I.e., something like

$ virtualenv -p python3 venv
$ source venv/bin/activate
$ pip install requests
$ pip install flask
$ pip install pycrypto

The server is then run as a standard flask application:

$ FLASK_APP=server.py flask run

By default the server runs at 127.0.0.1:5000.

On startup, the server picks a random key, and creates a random message of the form:

flag{<32 random hexencoded bytes}

Whenever the server receives a request at

127.0.0.1:5000/decrypt/<c>

where <c> is a hex encoded ciphertext, it decrypts c and responds with ok if the padding was correct and bad padding otherwise.