Preventing SSRF

Prevention Techniques

1. Implement Whitelisting:

   • Create a whitelist of allowed remote origins from which the web application can fetch data.

   • Ensure that any user-supplied URLs are checked against this whitelist to prevent requests to arbitrary origins.

2. Restrict URL Schemes and Protocols:

   • Limit the URL schemes (e.g., HTTP, HTTPS) and protocols that the application can use.

   • Hardcode allowed protocols or validate them against a predefined whitelist to prevent the use of arbitrary protocols.

3. Sanitize User Input:

   • Implement input sanitization to clean and validate any user-supplied data.

   • This helps prevent unexpected behavior that could lead to SSRF vulnerabilities.

4. Configure Firewall Rules:

   • Set up appropriate firewall rules to block outgoing requests to unauthorized or unexpected remote systems.

   • Ensure that the firewall is configured to drop any outgoing requests that could exploit SSRF vulnerabilities.

5. Utilize Network Segmentation:

   • Implement network segmentation to isolate critical internal systems from the web application.

   • This limits the potential impact of SSRF vulnerabilities by preventing attackers from accessing sensitive internal resources.

For more detailed information on SSRF mitigation measures, refer to the OWASP SSRF Prevention Cheat Sheet.