Offer modern AEAD ciphers on Apache

Why it matters

The server offers only older CBC ciphers for TLS 1.2 and no TLS 1.3, so no client gets the modern authenticated ciphers (AES-GCM or ChaCha20). CBC suites have a history of attacks and are slower.

Staged change. Do this in stages and check each one before the next, so a mistake does not break your site or your mail.

The fix

1. Find every existing setting with grep -Rn -E 'SSLProtocol|SSLCipherSuite' /etc/apache2 /etc/httpd /etc/letsencrypt. A VirtualHost or included line overrides the global one, so replace each SSLCipherSuite value (on RHEL-family systems the global line is in /etc/httpd/conf.d/ssl.conf), run apachectl configtest and reload.
2. Keep the previous lines commented out beside the new ones, so you can roll back by restoring them and reloading if a client you need breaks.

SSLProtocol             all -SSLv3 -TLSv1 -TLSv1.1
SSLCipherSuite          ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES128-GCM-SHA256:ECDHE-ECDSA-AES256-GCM-SHA384:ECDHE-RSA-AES256-GCM-SHA384:ECDHE-ECDSA-CHACHA20-POLY1305:ECDHE-RSA-CHACHA20-POLY1305
SSLHonorCipherOrder     off

Read the documentation ↗(opens in a new tab)

Related

• Reported by the cipher suites check
• Disable the RC4 cipher
• Disable the 3DES cipher
• Require forward-secret ciphers
• Retire the old TLS versions that use CBC ciphers