flask-cookie-decode 0.4.0

1.1.1 Current available commands

1. flask cookie decode: decodes and verifies the signature of the session cookie

1.2.1 Disclaimer: Keep your SECRET_KEY, secret!

If you expose this key your application becomes vulnerable to session replay attacks. Here is an example where an application exposed the SECRET_KEY during 404 errors. The example also illustrates how session replay works.

By default Flask does not expose the SECRET_KEY anywhere. It is up to you the developer to keep it that way!

1.3.1 Installation

$ pip install flask-cookie-decode

1.3.2 Extracting the cookie using browser tools

1.3.3 Example Flask app

See examples/app.py:

from flask import Flask, jsonify, session, request
from flask_cookie_decode import CookieDecode

app = Flask(__name__)
app.config.update({'SECRET_KEY': 'jlghasdghasdhgahsdg'})
cookie = CookieDecode()
cookie.init_app(app)

@app.route('/')
def index():
    a = request.args.get('a')
    session['a'] = a
    return jsonify(dict(session))

1.3.4 Examples using the CLI:

This extension will ship two CLI interfaces for dealing with decoding cookies. One requires a Flask application instance for the application you are wanting to debug. This method has the added benefit that the signature of the cookie can be verified, as your application instance has the SECRET_KEY used to sign the cookie. This method returns decoded cookie objects which can be seen in the examples below. This method can return a few different types of cookie objects depending on the state of the cookie. Please keep in mind that this extension provides only a thin-wrapper around the logic Flask uses to deal with cookies.

The second CLI interface is a tool for decoding cookies without the app secret. It cannot validate the signatures on the cookies or check the expirations and does not require the application instance like the other CLI. Intended for debugging purposes only.

$ export FLASK_APP=app.py
$ flask cookie decode eyJhIjoiYXNkYXNkamtqYXNkIn0.XCkk1Q.tTPu2Zhvn9KxgkP35ERAgyd8MzA
TrustedCookie(contents={'a': 'asdasdjkjasd'}, expiration='2019-01-30T20:04:37')

$ export FLASK_APP=app.py
$ flask cookie decode eyJhIjoiYXNkYXNkamtqYXNkIn0.XCkk1Q.tTPu2Zhvn9KxgkP35ERAgyd8MzA
UntrustedCookie(contents={'a': 'asdasdjkjasd'}, expiration='2019-01-30T20:04:37')

$ export FLASK_APP=app.py
$ flask cookie decode eyJhIjoiYXNkYXNkamtqYXNkIn0.XCkk1Q.tTPu2Zhvn9KxgkP35ERAgyd8MzA
ExpiredCookie(contents={'a': 'asdasdjkjasd'}, expiration='2019-01-30T20:04:37')

$ fcd decode eyJhIjoiYXNkYXNkamtqYXNkIn0
{
  "a": "asdasdjkjasd"
}

2.4.1 Bugfixes

• In all previous releases the CLI with the --timestamp CLI flag was actually returning the timestamp when the cookie was signed. Not the timestamp when the cookie expires, as it should have been doing.

  In all previous releases there was no error handling for expired cookies. This release now returns a ExpiredCookie when it is detected. (#1)

2.4.2 Improved Documentation

• Updates the documentation to include some more details about the way the Flask session works, and things you should be looking out for from a security perspective. The documentation also reflects the latest in terms of the way the CLI works. (#1)