Jan 24, 2023 by Thibault Debatty | 209 views
In this blog post, we will show that a login page from a web application can be easily cracked if the application does not implement specific protections against this kind of attack.
The tools that we use a publicly available, so you can easily reproduce yourself. However, you must always ask for owner's consent before testing a web application!
Dokos is a simple login cracker written in Python. You can install it with:
python3 -m pip install dokos
After installation, dokos will be available in your path, so you can simply test with:
For this demo, the victim will be Brute Force app from Cylab Play, our collection of vulnerable containers.
I deployed the app using Play with Docker. It is a very simple app, with a login form.
Login cracker tools, like Dokos, typically need 6 information to run:
You can easily find lists of known passwords online, for example on https://github.com/danielmiessler/SecLists/tree/master/Passwords/Common-Credentials
For this demo, I will use the top 1000:
To find the login or email, hackers usually use OSINT techniques.
As you can see on the screenshot, the app displays a clear message if the authentication failed: "Bad combination of e-mail and password!"
Finally, the last 3 information can be found by inspecting the source code of the authentication form:
So now we can feed all these information to Dokos (on a single line):
dokos -l email@example.com -P 10-million-password-list-top-1000.txt -f "Bad combination of e-mail and password" --login_field email --password_field password http://ip172-18-0-18-cf7utl63tccg0089sr0g-8000.direct.labs.play-with-docker.com/
Dokos will show you the different passwords that it is testing, and at the end tell you if it found a password that's correct.
In this blog post, we have illustrated that the login form of a web application can be easily cracked if the app is not protected. This leads us to 2 conclusions:
As a web developer, you should always ensure that your app implements appropriate protections.
As a user, you should always use strong passwords (that include numbers and special characters). Moreover, you should never use the same password on different web applications.