Course

In this lab, we explore a Golang snippet with three functions: `buildSignatureforPayment`, `buildUrl`, and `verifyPayment`. These functions work together to create and verify a payment signature using HMAC with SHA-256. The code concatenates the user and amount to produce a signature, which is then used to construct a URL for payment processing.

However, the code has a significant flaw: it concatenates the user and amount directly without a separator. This can lead to collisions where different user and amount combinations produce the same HMAC signature. For example, a user "test" with an amount of 20 and a user "test2" with an amount of 0 both produce the same signature, causing a security vulnerability. This issue highlights the importance of using separators when concatenating values for signature generation to avoid such collisions.