👉 Overview
👀 What ?
Server Side Request Forgery (SSRF) is a web security vulnerability that allows an attacker to induce the server-side application to make HTTP requests to an arbitrary domain of the attacker's choosing. In a typical SSRF scenario, the attacker might cause the server to make a connection back to itself, or to other web-based services within the organization’s infrastructure, or to external third-party systems.
🧐 Why ?
SSRF attacks are a growing threat and can lead to serious damage, such as data leaks, shutdown or takeover of server functions, or other malicious activities. They can be hard to detect and protect against, and are often used in conjunction with other types of attacks. Understanding SSRF vulnerabilities and how they can be exploited is a key part of securing server-side applications.
⛏️ How ?
There are several methods that can be used to exploit SSRF vulnerabilities. These include: 1. Manipulating the application's functionality to trigger an HTTP request to a URL supplied by the attacker; 2. Exploiting the application's trust in the server it is running on; 3. Manipulating the application's logic to execute unintended functions; and 4. Using the application as a proxy to attack other systems. To protect against SSRF attacks, it is important to validate and sanitize all user inputs, restrict the HTTP methods that can be used, and implement strong access controls.
⏳ When ?
SSRF vulnerabilities have been known and exploited since the early 2000s. However, they have become more prevalent with the shift towards web-based applications and services, and the increasing complexity of server-side systems.
⚙️ Technical Explanations
In an SSRF attack, the attacker manipulates a vulnerable server-side application to make a request to a specific URL. This can be either an internal resource that the application has access to, or an external resource that the attacker wants to target. The application then sends this request, along with any included data, to the specified URL. If the response from this request contains sensitive information, or if the request triggers a specific action on the target system, the attacker can achieve their objectives. This can include actions such as retrieving sensitive data, causing a denial of service, or even executing arbitrary code on the target system. The potential impact of an SSRF attack is therefore quite significant, and defending against these attacks is a critical aspect of server-side security.