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4.1.4 Ensure only modern TLS protocols are used

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Information

Only modern TLS protocols should be enabled in NGINX for all client connections and upstream connections. Removing legacy TLS and SSL protocols (SSL 3.0, TLS 1.0 and 1.1), and enabling emerging and stable TLS protocols (TLS 1.2, and TLS 1.3), ensures users are able to take advantage of strong security capabilities and protects them from insecure legacy protocols.

Rationale:

Why disable SSL 3.0: The POODLE Vulnerability allowed attackers to exploit SSL 3.0 to obtain cleartext information by exploiting weaknesses in CBC in 2014. SSL 3.0 is also no longer FIPS 140-2 compliant.

Why disable TLS 1.0: TLS 1.0 was deprecated from use when PCI DSS Compliance mandated that it not be used for any applications processing credit card numbers in June 2018. TLS 1.0 does not make use of modern protections, and almost all user agents that do not support TLS 1.2 or higher are no longer supported by their vendor.

Why disable TLS 1.1: Because of the increased security associated with higher versions of TLS, TLS 1.0 should be disabled. Modern browsers will begin to flag TLS 1.1 as deprecated in early 2019.

Why enable TLS 1.2: TLS 1.2 takes advantage of several security features including modern cipher suites, perfect forward security, and authenticated encryption.

Why enable TLS 1.3: TLS 1.3 improves security by removing several insecure cipher suites by default and adding several more secure algorithms. All public-key exchange mechanisms support perfect forward secrecy in this version of TLS. Additionally, TLS 1.3 makes drastic performance improvements by removing a full round trip in the TLS handshake.

Impact:

Disabling certain TLS may not allow legacy user agents to connect to your server. Disabling negotiation of specific protocols with your backend server may also limit your ability to connect with legacy servers. You should always consider if you need to support legacy user agents or servers when selecting your TLS protocols.

Solution

Run the following commands to change your ssl_protocols if they are already configured. This remediation advice assumes your nginx configuration file does not include server configuration outside of /etc/nginx/nginx.conf. You may have to also inspect the include files in your nginx.conf to ensure this is properly implemented.

Web Server:

sed -i 's/ssl_protocols[^;]*;/ssl_protocols TLSv1.2 TLSv1.3;/' /etc/nginx/nginx.conf

Proxy:

sed -i 's/proxy_ssl_protocols[^;]*;/proxy_ssl_protocols TLSv1.2 TLSv1.3;/' /etc/nginx/nginx.conf

If your ssl_protocols are not already configured, this can be accomplished manually by opening your web server or proxy server configuration file and manually adding the directives.

Web Server:

server {
 ssl_protocols TLSv1.2 TLSv1.3;
}

Proxy:

location / {
 proxy_pass cisecurity.org;
 proxy_ssl_protocols TLSv1.2 TLSv1.3;
 }

Default Value:

By default, NGINX does not specify the TLS protocol and accepts all TLS versions, except for TLS 1.3, which must be enabled by an administrator to take effect.

Defaults: ssl_protocols TLSv1.0 TLSv1.1 TLSv1.2 proxy_ssl_protocols TLSv1.0 TLSv1.1 TLSv1.2

See Also

https://workbench.cisecurity.org/files/4212

Item Details

References: CSCv7|14.4

Plugin: Unix

Control ID: ed00f5f8d728c85bad5f469054fd995e89b651adad19631260eda37b8ab56568