What is the main function of Server-Side Request Forgery (SSRF)?

The main function of Server-Side Request Forgery (SSRF) is to leverage a trusting relationship between web servers. SSRF occurs when an attacker tricks a server into making requests to internal or external resources on behalf of the attacker. This technique exploits the server's ability to access resources that the attacker may not be able to reach directly due to network restrictions or firewalls.

In many configurations, web servers may trust and interact with other internal servers or APIs, leading to a situation where an attacker can craft a request that is executed by the server. This can result in unauthorized access to sensitive data, services, and possibly a full compromise of the server itself, depending on the server's configuration and the resources it accesses. The trusting relationship is essential, as it allows the server to make requests without validating whether those requests are appropriate or safe.

Understanding this is crucial for securing applications and preventing SSRF vulnerabilities, as it highlights the importance of properly configuring internal systems and validating the requests being made by web applications.