Java Snippet #10
This challenge covers the review of a snippet of code written in Java
The Code Review Snippet challenges provide small snippets of vulnerable code for analysis. In this specific challenge, you are presented with a Java class named Fetcher. The class includes a method called fetch, which aims to fetch content from URLs that start with "https://pentesterlab.com". However, the filtering mechanism implemented on line 12 is easily bypassable. Attackers can use alternative domain names or URL encoding tricks to bypass the filter, allowing unauthorized access to the fetch method.
The fetch method first checks if the URL starts with "https://pentesterlab.com". If it does, it tries to open a connection and read the content from the URL. If the URL doesn't meet this criterion, access is denied. The flaw lies in the simplistic check on line 12, which can be bypassed by using subdomains like "https://pentesterlab.com.example.com" or by using the "@" symbol to trick the filter, making "pentesterlab.com" part of the username in basic authentication.
This lab highlights the importance of robust URL validation and demonstrates how simple string checks can be insufficient for security. Understanding these vulnerabilities is crucial for developing secure code and improving your skills in code review and penetration testing.