In the context of API security, Server-Side Request Forgery (SSRF) is a vulnerability that allows attackers to trick a vulnerable server-side application (often an API) into making unauthorized requests to another server.

Here's a breakdown of the key concepts involved:

• Server-Side: This refers to the backend logic of the application, including the code that interacts with APIs.

• Request Forgery: Forgery here means manipulating a request to make it appear legitimate. In SSRF, the attacker manipulates the API request to trick the server into making the unauthorized request.

• Untrusted Input: The vulnerability arises from the server-side application trusting and processing user-supplied input without proper validation. It allows attackers to inject malicious code or manipulate the request parameters.

How SSRF Attacks Work:

Attackers exploit SSRF vulnerabilities by injecting malicious code into user input processed by the API. This code often takes the form of a URL. Here's a simplified example:

1. The API allows users to submit a feedback form, including a "website URL" field.

2. The attacker submits a feedback form with a malicious URL crafted to exploit SSRF. This URL might point to a malicious server controlled by the attacker.

3. The vulnerable API processes the form without adequately validating the URL.

4. The server-side code, tricked by the attacker-crafted URL, sends an unauthorized request to the attacker's server.

Consequences of SSRF Vulnerabilities:

SSRF vulnerabilities can have serious consequences, including:

• Internal Network Access: Attackers can gain access to internal resources on the server's network that shouldn't be exposed externally. It can lead to data breaches or compromise of sensitive systems.

• Denial-of-Service (DoS) Attacks: Attackers can exploit SSRF to overload internal resources or launch DoS attacks against other servers on the network.

• Exfiltrating Sensitive Data: In some cases, attackers might use SSRF to trick the server into making requests that reveal sensitive information, such as internal server configurations or file contents.

Preventing SSRF Vulnerabilities:

Here are some ways to avoid SSRF vulnerabilities:

• Validate User Input: Always validate and sanitize user input before processing it. It helps ensure the server only accepts legitimate URLs and prevents code injection attempts.

• Restrict Allowed URLs: Restrict the types of URLs the server can access through API requests. For example, only allow access to specific internal resources or public websites.

• Monitor Network Activity: Monitor server-side network activity to detect suspicious outgoing requests that might indicate SSRF exploitation.

• Keep Software Updated: Maintain updated server-side software and libraries to address known SSRF vulnerabilities.

By following these practices, developers can significantly reduce the risk of SSRF attacks and ensure their APIs don't make unauthorized requests based on untrusted user input.

ThreatNG, with its focus on EASM and DRP, can be a valuable tool in the fight against Server-Side Request Forgery (SSRF) attacks. Here's how:

Discovery Power:

• API Inventory: ThreatNG's core strength lies in its ability to discover all APIs exposed by your organization. This comprehensive inventory is crucial for SSRF because attackers often target functionality hidden within internal APIs.

• Attack Surface Visibility: By identifying all APIs, ThreatNG expands your organization's attack surface visibility. This allows security teams to prioritize which APIs need stricter validation and access controls to mitigate SSRF risks.

EASM and DRP to the Rescue:

• Continuous Monitoring: EASM's continuous monitoring capabilities can help detect suspicious activity related to SSRF attempts. This might include identifying attempts to access internal resources through APIs or unusual API traffic patterns.

• Digital Risk Protection: DRP can provide valuable threat intelligence. By analyzing external sources, ThreatNG can identify emerging SSRF vulnerabilities and attack techniques, allowing your team to proactively address them before attackers exploit them.

Complementary Approach:

ThreatNG works seamlessly with other security solutions to create a layered defense against SSRF:

• Vulnerability Scanners: ThreatNG's API inventory can be shared with vulnerability scanners to prioritize scans for API endpoints that might be susceptible to SSRF.

• Web Application Firewalls (WAFs): The API data from ThreatNG can be used to configure WAFs to block malicious requests that attempt SSRF exploits.

Handoff Example - Functionality and Access Testing:

1. ThreatNG Discovers Risk: ThreatNG discovers an API used for server maintenance. This API wasn't previously documented and could be a potential SSRF target.

2. Alert and Investigation: ThreatNG raises an alert, prompting the security team to investigate further.

3. Handoff to Pen Testers: Security analysts share the API details and potential SSRF risk with penetration testers.

4. Penetration Testing: Pen testers use this information to conduct focused tests to assess the API's functionality and access controls for vulnerabilities. They can attempt to exploit SSRF by crafting malicious requests through the API.

5. Remediation and Hardening: Based on the pen testing findings, developers implement stricter validation rules and access controls for the API, effectively hardening it against SSRF attacks.

By leveraging ThreatNG's discovery power and working together with other security solutions, organizations can proactively identify and address SSRF risks before they can be exploited. This strengthens the overall security posture and prevents potential data breaches and system disruptions.