Require forward-secret ciphers on Apache

Why it matters

The server accepts ciphers where one stolen private key can decrypt all recorded past traffic. Forward-secret ciphers (ECDHE) are supported by every current client.

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

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Related

• Reported by the cipher suites check
• Disable the RC4 cipher
• Disable the 3DES cipher
• Offer modern AEAD ciphers
• Retire the old TLS versions that use CBC ciphers