Server Side Request Forgery 02

In this lab, we delve into a Server Side Request Forgery (SSRF) vulnerability, where the developer attempted to secure the application by blocking access to 127.0.0.1. A detailed code review reveals that the application checks if the URL parameter starts with http/https and ensures the host is not 127.0.0.1. However, this simplistic approach does not account for all possible ways to access localhost. By using alternative aliases for localhost, such as 127.0.0.2, an attacker can bypass the restriction.

The lab demonstrates the importance of comprehensive security checks and highlights common pitfalls in SSRF protections. The code review walks through the logic of handling the URL parameter, noting the misuse of variables and the insufficient checks against localhost. This scenario underscores the necessity for developers to understand the multiple ways attackers can bypass security measures and the need for more robust validation mechanisms.