What is the ngx_http_ssl_module: A Simple Guide

In this article, I will provide you with a simple guide to understand the ngx_http_ssl_module, a powerful module provided by NGINX that enables SSL/TLS support for secure connections. By configuring this module, you can enhance the security of your NGINX server, ensuring the confidentiality and integrity of data transmitted over the network.

The ngx_http_ssl_module is not enabled by default in NGINX and requires manual configuration using the –with-http_ssl_module parameter. It also relies on the OpenSSL library to function properly. Once enabled, you can optimize your server’s secure connections by following some recommended practices.

Now, let’s explore the various aspects of the ngx_http_ssl_module, including its configuration directives, advanced security features, SSL offloading, and more.

Key Takeaways:

• The ngx_http_ssl_module is a powerful module provided by NGINX for enabling SSL/TLS support in NGINX.
• It needs to be manually configured with the –with-http_ssl_module parameter and requires the OpenSSL library.
• Optimizing secure connections involves setting the number of worker processes, enabling keep-alive connections, and enabling the shared session cache.
• The ngx_http_ssl_module offers various configuration directives to control SSL/TLS settings, such as ssl_certificate, ssl_buffer_size, and ssl_protocols.
• It supports SSL/TLS offloading, backend encryption, client certificates, and additional security features like OCSP stapling and chained certificates.

Example Configuration Directives for ngx_http_ssl_module

The ngx_http_ssl_module provides various configuration directives to control SSL/TLS settings. These directives allow administrators to customize the SSL/TLS behavior of their NGINX server to meet their specific security requirements. Here are some important directives:

1. ssl: This directive enables or disables SSL/TLS support for the server. It can be set to “on” or “off” depending on whether SSL/TLS encryption is desired.
2. ssl_buffer_size: With this directive, administrators can set the size of the buffer used for sending data. It determines the maximum amount of data that can be sent in a single SSL/TLS record. The default value is usually sufficient, but it can be adjusted if necessary.
3. ssl_certificate: This directive specifies the file with the server’s certificate in the PEM format. The certificate is used to verify the server’s identity to clients during the SSL/TLS handshake.
4. ssl_certificate_key: This directive specifies the file with the server’s private key in the PEM format. The private key is used to decrypt incoming SSL/TLS traffic and sign outgoing data.
5. ssl_ciphers: This directive allows administrators to specify the enabled ciphers for SSL/TLS connections. Ciphers determine the encryption algorithms used to secure the communication between the client and server.
6. ssl_trusted_certificate: This directive specifies a file with trusted CA certificates. It is used to verify the authenticity of client certificates during client authentication.
7. ssl_protocols: This directive specifies the enabled SSL/TLS protocols. It allows administrators to specify which versions of SSL/TLS to support, such as SSLv3, TLSv1.0, TLSv1.1, or TLSv1.2.
8. ssl_session_cache: This directive enables the shared session cache for SSL/TLS sessions. The session cache improves performance by caching SSL/TLS session parameters and reusing them for subsequent connections.

By properly configuring these directives, administrators can ensure that their NGINX server’s SSL/TLS settings are optimized for security, performance, and compatibility with client devices.

Example Configuration

Here is an example NGINX configuration that demonstrates the usage of these directives:

    ssl on;
    ssl_buffer_size 8k;
    ssl_certificate /etc/nginx/ssl/server.crt;
    ssl_certificate_key /etc/nginx/ssl/server.key;
    ssl_ciphers "AES256+EECDH:AES256+EDH";
    ssl_trusted_certificate /etc/nginx/ssl/ca.crt;
    ssl_protocols TLSv1.2 TLSv1.3;
    ssl_session_cache shared:SSL:10m;
  

SSL Offloading and Backend Encryption with ngx_http_ssl_module

SSL/TLS offloading is a technique that allows NGINX to handle the SSL/TLS decryption process, relieving backend servers of this resource-intensive task. By offloading SSL/TLS processing to NGINX, organizations can improve performance and utilization of their backend servers. This is particularly beneficial in high traffic environments where the volume of SSL/TLS connections can place a heavy burden on the backend infrastructure.

Additionally, the ngx_http_ssl_module enables SSL/TLS encryption to the origin servers. This means NGINX can encrypt traffic that is sent from the client to the backend servers, ensuring end-to-end encryption of sensitive data. By encrypting the connection between NGINX and the backend servers, organizations can protect sensitive data from potential eavesdropping or interception.

Furthermore, NGINX supports client certificates, a feature provided by the ngx_http_ssl_module. Client certificates can be used for optional or required client authentication, providing an additional layer of security. With client authentication enabled, NGINX verifies the client’s identity using the client certificate, ensuring that only authorized clients can access the protected resources.

SSL/TLS Offloading

SSL/TLS offloading is a technique that involves offloading the SSL/TLS decryption process from backend servers to a dedicated load balancer or reverse proxy, such as NGINX. When a client initiates an SSL/TLS connection, the load balancer or reverse proxy handles the SSL/TLS handshake process and decrypts the encrypted data. Once decrypted, the load balancer or reverse proxy can inspect and route the traffic based on the application layer protocols, such as HTTP, before forwarding it to the backend servers. This offloading process reduces the computational load on the backend servers, allowing them to focus on processing the application layer data without the added overhead of SSL/TLS decryption.

SSL/TLS Encryption to the Origin Servers

The ngx_http_ssl_module enables NGINX to establish secure SSL/TLS connections with the origin servers. This means that NGINX can encrypt traffic from the client to the backend servers, providing end-to-end encryption for sensitive data. By encrypting the connection between NGINX and the backend servers, organizations can protect the confidentiality and integrity of data transmitted over the network, ensuring that only authorized parties can access and modify the data. This is particularly important when transmitting sensitive information, such as credit card details, personal information, or confidential business data.

Client Certificates

Client certificates are a form of digital identification used to authenticate clients connecting to a server. With the ngx_http_ssl_module, NGINX can validate client certificates presented during the SSL/TLS handshake process. This allows organizations to implement optional or mandatory client authentication, depending on their security requirements. By requiring clients to present a valid client certificate, organizations can ensure that only authorized clients can access protected resources. Client certificates are particularly useful in scenarios where strong client authentication is required, such as securing access to sensitive information or enforcing strict access control policies.

Additional Security Features of ngx_http_ssl_module

The ngx_http_ssl_module provides several additional security features that can enhance the security of your NGINX server and protect sensitive data. These features include the ability to support multiple certificates, OCSP stapling, fine-grained control over SSL/TLS ciphers and protocols, and support for chained certificates.

Multiple Certificates

With the ngx_http_ssl_module, you can configure NGINX to support multiple certificates for different domains on a single instance. This means that you can use a single NGINX server to handle secure connections for multiple websites, each with its own unique SSL certificate. This simplifies the management of SSL certificates and makes it easier to scale your server infrastructure.

OCSP Stapling

OCSP stapling is a technique that can improve the performance and security of SSL/TLS connections. It involves the server obtaining the OCSP response from the certificate authority and stapling it to the SSL handshake response. This way, the client can verify the server’s certificate without the need to make an additional request to the certificate authority, reducing latency and improving security.

SSL/TLS Ciphers and Protocols

The ngx_http_ssl_module allows you to specify the ciphers and protocols that are enabled for SSL/TLS connections. This gives you fine-grained control over the security level and compatibility of your server. You can choose from a wide range of ciphers and protocols, including the latest secure ones and disable weak or vulnerable options.

Chained Certificates

In some cases, your SSL certificate may be signed by an intermediate certificate authority. To establish the chain of trust, NGINX supports chained certificates, where the website’s certificate is presented along with the intermediate certificates. This ensures that clients can verify the authenticity of your SSL certificate and establishes a secure connection.

Using Self-Signed Certificates and CACert Keys with ngx_http_ssl_module

When it comes to securing your NGINX server with SSL/TLS, there are various options available. One such option is the use of self-signed certificates, which can be generated for internal use. Self-signed certificates are not issued by a trusted certificate authority, but they can still provide encryption for your connections. They are particularly useful in development or testing environments where there is no need for a publicly trusted certificate. To use self-signed certificates with the ngx_http_ssl_module, you need to generate the certificate and private key files, and then configure NGINX to use them.

Another option for securing your NGINX server is the use of CACert keys. CACert keys are client keys that can be used for client authentication. With client authentication, the server can verify the identity of the client connecting to it. This adds an extra layer of security to your connections. To use CACert keys with the ngx_http_ssl_module, you need to install the client keys on client devices and configure NGINX to validate client keys against internal CA certificates.

Using self-signed certificates and CACert keys with the ngx_http_ssl_module provides flexibility and control over the security of your NGINX server. Whether you need to secure internal connections or implement client authentication, these features can help you achieve your desired level of security.

“Using self-signed certificates and CACert keys with the ngx_http_ssl_module provides flexibility and control over the security of your NGINX server.”

NGINX Configuration for SSL/TLS with ngx_http_ssl_module

Configuring NGINX for SSL/TLS with the ngx_http_ssl_module is a crucial step in securing your server’s connections. By properly setting SSL parameters and configuring client authentication, you can ensure the confidentiality and integrity of data transmitted over the network.

When configuring NGINX for SSL/TLS, you will need to specify the SSL certificate and private key using the ssl_certificate and ssl_certificate_key directives, respectively. These directives should point to the location of the respective files on your server. You can also set the desired SSL protocols and ciphers using the ssl_protocols and ssl_ciphers directives, ensuring that your server supports the most secure and up-to-date options.

If you require client authentication, you can configure NGINX to validate client certificates against a Certificate Authority (CA) using the ssl_client_certificate directive. This directive should specify the location of the CA certificate file on your server. Additionally, you can use the ssl_verify_client directive to set whether client certificates are optional or required for connection.

Example NGINX Configuration:

http {
    server {
        listen 443 ssl;
        server_name example.com;

        ssl_certificate /path/to/certificate.crt;
        ssl_certificate_key /path/to/private.key;

        ssl_protocols TLSv1.3;
        ssl_ciphers 'TLS_AES_256_GCM_SHA384:TLS_CHACHA20_POLY1305_SHA256';

        ssl_client_certificate /path/to/ca.crt;
        ssl_verify_client optional;

        location / {
            # Your server configuration here
        }
    }
}

Conclusion

The ngx_http_ssl_module is a powerful module provided by NGINX that enables SSL/TLS support for secure connections. It offers a wide range of configuration directives and additional security features to ensure the confidentiality and integrity of data transmitted over the network.

By leveraging the ngx_http_ssl_module, administrators can optimize their server’s secure connections and implement advanced security measures such as SSL/TLS offloading, client authentication, and end-to-end encryption.

With the ability to configure various SSL/TLS settings, including protocols, ciphers, and session cache, NGINX provides a flexible solution for securing websites and applications. The ngx_http_ssl_module also supports features like multiple certificates for different domains, OCSP stapling, and chained certificates.

Overall, the ngx_http_ssl_module is an essential component for ensuring secure communication and protecting sensitive data. By implementing the module’s features and best practices, administrators can enhance their server’s security posture and provide a safer browsing experience for their users.

Claudia Rothenhorst

Claudia loves to discover the world and conquer new software products every now and then.