Server-Side Request Forgery Attacks: What Devs Need to Know

While we often think of attacks as originating from users’ browsers, there are dangerous vulnerabilities that lie on the server side. One such threat is server-side request forgery (SSRF) attacks.

What is Server-Side Request Forgery (SSRF)?

In a Server-Side Request Forgery attack, the attacker tries to manipulate the URL to gain access to something within a network. This manipulation allows the attacker to craft a URL that points to resources or actions they shouldn’t usually have access to. That could be internal systems, databases, REST interfaces, or even cloud metadata.

Manipulating Trust Relationships

A key characteristic of SSRF attacks is the manipulation of trusted relationships. Trust relationships are assumptions made within a network or environment based on location or communication between systems.

These assumptions, often implicit and unquestioned, can create blind spots in our security posture, providing an opening for malicious actors. This lack of sufficient authorization and validation checks prior to allowing actions is regularly where SSRF attacks take root.

Common Trust Relationships

SSRF attacks thrive on the vulnerabilities created by implicit trust relationships. Let’s explore some examples of these relationships that can open doors to malicious actors.

Here are a few examples of trust relationships often exploited in SSRF attacks:

• Local Machine Trust: Applications often have an implicit trust relationship with their local machine. If a request originates from the local machine, it might be treated as trusted without additional validation. An attacker could exploit this to interact with other systems that are running locally.
• Admin Interface Trust: Admin interfaces are typically assumed to be trusted. If an attacker can access the admin interface, it might be assumed they have legitimate admin privileges and can perform sensitive actions without further authorization. Instead of validating before an action is carried out, access is assumed.
• Network Level Trust: Within a local network (LAN), there might be an assumption that all communication between servers within the LAN is trusted and secure. However, an attacker could gain access to this network and exploit this assumption.

Conclusion

Server-side request forgery attacks are a serious threat that every security-conscious developer needs to be aware of. By manipulating trust relationships, attackers can bypass network boundaries and gain access to sensitive data and resources.

Mitigating SSRF vulnerabilities requires a combination of secure coding practices and a proactive approach to security. At Security Journey, we understand the importance of having a strong security culture within an organization. Our training provides developers with the knowledge and skills to navigate security vulnerabilities, including SSRF attacks, ensuring that your organization can innovate confidently while mitigating security risks.