XSS Homework Help

Monash University

FIT 2093 Introduction to Cyber Security

Assignment 2: Web Hacking Challenge

In this assignment, your goal is to do security testing of a mini web application to try find vulnerabilities in it using techniques covered in our Web security lecture, and exploit them to break the app’s security. You can access the web application at the following URL:

http://13.54.173.115/brokenapp.php

This web app give access to registered members of a `Broken App’ group to access some information common to the group members (provided using the PHP server script at brokenapp.php) as well as personal private information for each group member (via the script at brokenapp-personal.php on the same domain).

Visit the web application URL above using your web browser. If all is well, the browser should display a page that looks like this:

Tasks. Your task is to perform the following security tests on this web application.

Part A: Personal Private Information Security Test

In this part, your aim is to do security testing of the personal private information part of the web app. For this, you are given member 1’s password, namely:

Ro4mvSemq45xfepvaEr24

• Here, we consider an attack against member 1 by some outsider (non-member) attacker. Try logging in with the given member 1 password, and examining that member’s private information. Based on the application behavior, where on this page could there be a possible point where a reflected XSS vulnerability might exist? Why? Perform a test to see if an XSS vulnerability exists for an attack against member 1, and explain your test, its results, and conclusion on why/why not such a vulnerability exists and can be exploited. (1 mark)
• Test the application against an attacker who is one of the authorized group members, in particular the member with ID number 1. Can that member gain unauthorized access to another member’s personal private data? If so, explain the vulnerability you found and how member 1 can exploit it, show any private member data exposed by the attack, and briefly explain how the vulnerability could be eliminated. In any case, explain the tests you did, the results, and your interpretation of them. (2 marks)

Part B: Shared Group Private Information Security Test

In this part, your aim is to do security testing of the shared group private information part of the web application, from the point of view of an outsider (non-member) attacker trying to reveal the group private information. Although you are not given the shared group password, you are given the php code for the relevant script brokenapp.php (available for download on Moodle).

(3) Look at the details in the brokenapp.php PHP script available on Moodle to see how user input is read in from the user's browser request and how the authentication check is performed. You should read the PHP documentation on the PHP functions used in the script, see http://php.net/manual/en/ and search for the relevant functions. The shared group password, whose cryptographic hash is hard-coded in the script, was generated using the php function call password_hash(pwd, PASSWORD_DEFAULT),where pwd is the password to be hashed

(note that the hash includes also a salt value generated at random). To help your security tests, you are also given a simple PHP script called password_hasher.php (the code is available on Moodle, it can be run by pointing your browser to http://13.54.173.115/password_hasher.php ; alternatively, you could run it by copying it into the web server folder /var/www/html/ of your FIT2093 Ubuntu-64 VM and then pointing your VM Firefox browser to http://localhost/password_hasher.php ). The script takes an input password from a user and displays its hash value (generated using the php function call above) when the user clicks the small button below the text box.

Using the above information/tools, attempt to identify a vulnerability in brokenapp.php. If you found a vulnerability, explain how it can be exploited, provide any secret information revealed, and briefly explain how the brokenapp.php code could be modified to eliminate this vulnerability. In any case, explain what tests you did, the results, and your interpretation of them. (2 marks)

Note: You should assume the attacker will NOT have any network eavesdropping/modification access (the current web application under test is running on an unencrypted http connection, but to protect against network eavesdropping/modification will be implemented over an encrypted https connection in the final production version).