Course

In this course, we delve into the exploitation of a length extension attack, focusing on how developers might mistakenly use hash functions in a way that leaves applications vulnerable. The course begins with an introduction to the concept of length extension, explaining that this vulnerability arises when a hash function that is not resistant to length extension is used to sign data. By understanding how the hashing process can be manipulated, attackers can append data to a hashed value and generate a valid signature without knowing the original secret.

The practical portion of the course guides you through performing a length extension attack using the `hash_extender` tool. Detailed explanations and a step-by-step walkthrough of the source code demonstrate how to identify and exploit this vulnerability. The course concludes by emphasizing the importance of using HMAC instead of simple hash functions for signing data, as HMAC is resistant to length extension attacks.