Advanced SSRF Prevention

Introduction

Server-Side Request Forgery (SSRF) is a vulnerability that allows an attacker to send unauthorized requests from a server to internal or external resources. This lesson provides advanced techniques for preventing SSRF, a critical issue recognized in the OWASP Top 10 list.

Key Concepts

Prevention Techniques

1. **Input Validation**: Always validate URLs against a whitelist of allowed domains.
2. **Use of DNS Filtering**: Implement DNS filtering to block requests to untrusted domains.
3. **Network Segmentation**: Isolate sensitive services and restrict access to them.
4. **Secure Configuration**: Disable unnecessary services and enforce strict configurations.

function isValidUrl(url) {
    const allowedDomains = ['example.com', 'api.example.com'];
    const parsedUrl = new URL(url);
    return allowedDomains.includes(parsedUrl.hostname);
}

Best Practices

• Regularly review and update your application’s security policies.
• Implement logging and monitoring for outgoing requests.
• Conduct regular security testing, including penetration tests targeting SSRF.
• Educate developers on secure coding practices related to external requests.

FAQ