Concuss

What is it?

Concuss is a tool for banging against a url with a bunch of different headers to look for potential vulnerabilities.

It works by sending a custom or a random string to a webserver for a specific url in a variety of headers to see if it's able to get that string to appear on the page. If so, you'll get a HIT and you can evaluate that header to see if it's useful for some kind of XSS, cache poisoning, or some other form of injection from malformed headers.

Often times web app and framework developers assume that headers from the client are not malicious or manipulated and will just write them out to the page in one form or another. This project is a specialized tool to find instances of this so that they can be fixed before they are abused.

What it is NOT.

Concuss is not a tool for automating vulnerabilities, nor should it be used to certify that a page is safe from vulnerabilities. It should not be used on applications or website that you do not personally have permission to scan.

Sending malformed headers to a site can potentially cause errors, crashing, and other damage that I am not responsible for as a result of any usage of this tool. You agree to use this tool at your own risk.

Installation

Install the gem and add to the application's Gemfile by executing:

$ bundle add concuss

If bundler is not being used to manage dependencies, install the gem by executing:

$ gem install concuss

Usage

Primarily, you'll want to use it as a CLI like so:

concuss http://localhost:4567
concuss http://localhost:4567 -h non_standard

See concuss --help for more usage details.

While concuss is designed to be used as a command line tool, you can also include it in your own custom application like so:

require 'concuss'

concuss = Concuss.new(url: 'http://localhost:4567', file: 'header_file.txt', header_set: :standard, test_string: "OOGABOOGA")
report = concuss.attack!

From there, you'll get a Concuss::Report object that contains the raw data as well as filters for hits, misses, headers, and the url in the event you've done a bunch of these.

Demo

There is a sample app with a vulnerability to test with in the vuln_app directory. It takes the contents of X-CSRF-Token and spits them out blindly.

Here's some steps to get going with that:

docker-compose build
docker-compose run console bash

# You should see the vuln_app container boot up and
# then you'll land in bash on the console container

bin/concuss http://vuln_app:4567 -h non_standard

Development

Primarily, you'll want to use Docker to do debugging and development. To get into the console, just run docker-compose run console bash and from there you can run bin/concuss against the sample vulnerable app, or you can run rspec to run the specs.

If you prefer to develop without docker, after checking out the repo, run bundle install to install dependencies. Then, run rspec to run the tests.

When developing using docker or on your bare machine you can also run script/console for an interactive prompt that will allow you to experiment. This will give you access to the underlying classes and let you experiment outside the confines of the CLI.

If you add features or fix bugs, please write specs and open up a PR.

Note: Concuss was designed to easily install on most systems with ruby 3+. As such, its only dependencies are in the ruby standard library.

Contributing

Bug reports and pull requests are welcome on GitHub at https://github.com/patricktulskie/concuss

License

The gem is available as open source under the terms of the MIT License.