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How can I configure mTLS to authenticate API clients securely?

Asked on Sep 15, 2025

Answer

To configure mTLS (mutual TLS) for authenticating API clients securely, you need to set up both the server and client to verify each other's certificates. This ensures that both parties are who they claim to be.
<!-- BEGIN COPY / PASTE -->
    # Example Nginx configuration for mTLS
    server {
      listen 443 ssl;
      ssl_certificate /etc/ssl/certs/server-cert.pem;
      ssl_certificate_key /etc/ssl/private/server-key.pem;
      ssl_client_certificate /etc/ssl/certs/ca-cert.pem;
      ssl_verify_client on;
      ssl_verify_depth 2;
    }
    <!-- END COPY / PASTE -->
Additional Comment:
  • Ensure the CA certificate used for client verification is trusted and up-to-date.
  • Set ssl_verify_depth to an appropriate level to limit the chain of trust.
  • Regularly rotate and revoke certificates to maintain security.

✅ Answered with Security best practices.


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