mTLS cloud flare integration with kong

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integrate kong with cloudflare with mtls

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Integrating Kong with Cloudflare via mTLS

The user is asking about how to integrate Kong with Cloudflare using mTLS, which stands for mutual TLS. Kong is an API gateway, and the goal is to set up mTLS for secure communication with Cloudflare. This likely involves configuring Cloudflare as a reverse proxy for Kong. I’ll need to include steps for setting up mTLS on both ends, including cert management. The answer will detail how to configure mTLS in Cloudflare and how to handle it on the Kong side for a secure connection.

Configuring Kong and Cloudflare with mTLS

To integrate Kong with Cloudflare using mTLS, we need a few key steps. Cloudflare supports mTLS via its Zero Trust/Access solutions, and Kong can use mTLS for upstream services. Here’s a simplified approach:

  1. Generate certificates (either Cloudflare’s Origin or client certificate).
  2. On Kong’s end, configure the mTLS plugin or settings to verify the client certificate.
  3. On Cloudflare, configure mTLS to forward certificates or use “Authenticated Origin Pulls” to validate requests with a client certificate from Cloudflare to Kong.

Below is an overview of how you can integrate Kong with Cloudflare using mutual TLS (mTLS) to secure the connection between Cloudflare (as your edge proxy) and Kong (as your API gateway):

1. Overview of the Integration

  • Cloudflare Authenticated Origin Pulls:
    Cloudflare can be configured to present a client certificate when it connects to your origin server. This proves to your origin that the connection is coming through Cloudflare.
  • Kong as the Origin:
    Kong (which runs on Nginx) can be configured to require and verify client certificates on incoming TLS connections. In this scenario, Kong will be set to trust only the client certificate (or its issuing CA) that Cloudflare uses.

The integration ensures that only requests that have passed through Cloudflare—and that present the proper client certificate—are accepted by Kong.

2. Prerequisites

  • A Cloudflare account with your domain configured.
  • Cloudflare’s Authenticated Origin Pulls enabled (this is available in your Cloudflare dashboard).
  • A publicly trusted server certificate installed on Kong for its TLS listener.
  • Administrative access to your Kong instance so you can modify TLS settings (via configuration file or custom Nginx snippets).

3. Enable Cloudflare Authenticated Origin Pulls

  1. Activate Authenticated Origin Pulls in Cloudflare:
    In the Cloudflare dashboard, go to SSL/TLS → Edge Certificates and ensure that Authenticated Origin Pulls is turned on.
  2. Download the Cloudflare Origin Pull CA Certificate:
    Cloudflare publishes a CA certificate that it uses to sign its client certificates for origin pulls. You can download it from Cloudflare’s documentation (typically named something like origin-pull-ca.pem).

4. Configure Kong to Require mTLS from Cloudflare

Since Kong uses Nginx as its underlying proxy, you can require client certificate verification by adjusting its TLS configuration. There are two common approaches:

A. Using a Custom Nginx Configuration Snippet in Kong

  1. Locate or Create a Custom Nginx Snippet File:
    Depending on your Kong version, you can add custom configuration to Kong’s Nginx configuration (for example, using the nginx_http_ssl_verify_client directive).
  2. Configure Client Certificate Verification:
    In your custom snippet (which might be included via Kong’s configuration file or a custom plugin), add directives similar to the following:# This snippet is applied to the HTTPS server block in Kong’s Nginx config ssl_verify_client on; ssl_client_certificate /path/to/cloudflare-origin-pull-ca.pem;
  3. Reload Kong:
    After updating the configuration, reload or restart Kong so that the new settings take effect.

B. Configuring Kong (Enterprise) with Built-In mTLS Features

If you are using Kong Enterprise or a version that supports mTLS configuration natively for incoming connections, you can use its configuration options (or plugins) to require client certificates. Check the Kong documentation for any native mTLS support where you can specify a trusted CA.

5. Test the Setup

  1. Verify the TLS Handshake:
    Use tools like OpenSSL’s s_client to simulate a connection to Kong and check that it requires a client certificate: openssl s_client -connect your-kong-host:443 -CAfile /path/to/cloudflare-origin-pull-ca.pem Without a proper client certificate, the handshake should fail.
  2. Send a Request Through Cloudflare:
    Ensure that when Cloudflare forwards requests to Kong, it presents its client certificate and that Kong accepts the connection.
  3. Monitor Kong Logs:
    Review Kong (or Nginx) logs to ensure that client certificate verification is working as expected.

6. Additional Considerations

  • Certificate Management:
    Maintain and update your Cloudflare Origin Pull CA certificate on Kong when required (though Cloudflare’s published CA rarely changes).
  • Fallback and Testing:
    During testing, you might want to temporarily set ssl_verify_client optional; so you can observe behavior without blocking all connections, then switch to on for production.
  • Security and Performance:
    Ensure that all certificate files are stored securely on your Kong server and that proper file permissions are set.
  • Documentation and Updates:
    Always refer to the latest Cloudflare documentation on Authenticated Origin Pulls and Kong documentation for any version-specific instructions.

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