How to configure TLS ciphers in Nginx

Tightening the allowed TLS cipher set in Nginx reduces the chance of clients negotiating weak encryption and makes security posture consistent across virtual hosts. A curated cipher list also helps meet compliance requirements by removing legacy algorithms and key exchange modes from the negotiation path.

During the TLS handshake, the client and server agree on a protocol version (for example, TLSv1.2 or TLSv1.3) and a cipher suite that both sides support. Nginx passes cipher configuration to its underlying OpenSSL (or LibreSSL) library via directives like ssl_protocols, ssl_ciphers, and ssl_prefer_server_ciphers inside the http or server context.

Cipher tuning can break connectivity when legacy clients require older protocols or non-AEAD ciphers, and certificate type influences which cipher families can actually be used (RSA vs ECDSA). ssl_ciphers primarily affects TLSv1.2 and older, while TLSv1.3 uses ciphersuites handled differently by the crypto library. Keep console or out-of-band access available for recovery, and validate configuration with nginx -t before reloading.

1. Locate existing ssl_protocols and ssl_ciphers directives in the active Nginx configuration.

   $ sudo nginx -T 2>/dev/null | grep -nE '^\s*(ssl_protocols|ssl_ciphers|ssl_prefer_server_ciphers|ssl_conf_command)\b|listen\s+443'
   64:    listen 443 ssl http2;
   71:    ssl_protocols TLSv1.2 TLSv1.3;
   72:    ssl_ciphers ECDHE-RSA-AES128-GCM-SHA256:ECDHE-RSA-AES256-GCM-SHA384;
   ##### snipped #####

2. Select a cipher policy baseline that matches client requirements.

   https://ssl-config.mozilla.org/

   Disabling TLSv1.0 and TLSv1.1 blocks legacy clients, including some older Java and embedded stacks.

3. Create a global TLS policy file at /etc/nginx/conf.d/tls-ciphers.conf.

   $ sudo tee /etc/nginx/conf.d/tls-ciphers.conf >/dev/null <<'EOF'
   ssl_protocols TLSv1.2 TLSv1.3;
   
   ssl_prefer_server_ciphers on;
   
   ssl_ciphers 'ECDHE-ECDSA-CHACHA20-POLY1305:ECDHE-RSA-CHACHA20-POLY1305:ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES128-GCM-SHA256:ECDHE-ECDSA-AES256-GCM-SHA384:ECDHE-RSA-AES256-GCM-SHA384';
   
   ssl_ecdh_curve X25519:secp256r1:secp384r1;
   EOF

   ssl_ciphers is an OpenSSL cipher string and mainly applies to TLSv1.2 and older, while TLSv1.3 ciphersuites are typically controlled by the crypto library defaults (or optional ssl_conf_command Ciphersuites support on newer builds).

   An overly strict cipher list can lock out required clients and cause immediate handshake failures on /443.

4. Confirm the TLS policy file is parsed by Nginx in the http context.

   $ sudo nginx -T 2>/dev/null | grep -n 'configuration file /etc/nginx/conf.d/tls-ciphers.conf'
   189:# configuration file /etc/nginx/conf.d/tls-ciphers.conf:

   When the file is missing from nginx -T output, verify /etc/nginx/nginx.conf includes /etc/nginx/conf.d/*.conf inside the http block.

5. Identify per-server overrides that conflict with the global cipher policy.

   $ sudo nginx -T 2>/dev/null | grep -n '^\s*ssl_ciphers\b'
   72:    ssl_ciphers 'ECDHE-ECDSA-CHACHA20-POLY1305:ECDHE-RSA-CHACHA20-POLY1305:ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES128-GCM-SHA256:ECDHE-ECDSA-AES256-GCM-SHA384:ECDHE-RSA-AES256-GCM-SHA384';
   310:   ssl_ciphers 'HIGH:!aNULL:!MD5';
   ##### snipped #####

   server context directives override http context directives, so remove or align the older overrides to avoid unexpected negotiation.

6. Validate the Nginx configuration before applying changes.

   $ sudo nginx -t
   nginx: the configuration file /etc/nginx/nginx.conf syntax is ok
   nginx: configuration file /etc/nginx/nginx.conf test is successful

7. Reload nginx to apply the updated cipher policy.

   $ sudo systemctl reload nginx

8. Confirm the nginx service remains active (running) after reload.

   $ sudo systemctl status nginx --no-pager
   ● nginx.service - A high performance web server and a reverse proxy server
        Loaded: loaded (/lib/systemd/system/nginx.service; enabled; vendor preset: enabled)
        Active: active (running) since Sun 2025-12-14 10:02:11 UTC; 8s ago
   ##### snipped #####

9. Verify a TLSv1.2 handshake negotiates an allowed cipher.

   $ openssl s_client -connect your.domain.tld:443 -servername your.domain.tld -tls1_2 -cipher 'ECDHE-RSA-AES128-GCM-SHA256' </dev/null
   CONNECTED(00000003)
   ##### snipped #####
   Protocol  : TLSv1.2
   Cipher    : ECDHE-RSA-AES128-GCM-SHA256
   Verify return code: 0 (ok)

   When the certificate is ECDSA-only, switch the test cipher to an ECDHE-ECDSA-* variant.

10. Verify a TLSv1.3 handshake succeeds when enabled.

    $ openssl s_client -connect your.domain.tld:443 -servername your.domain.tld -tls1_3 -ciphersuites 'TLS_AES_128_GCM_SHA256' </dev/null
    CONNECTED(00000003)
    ##### snipped #####
    Protocol  : TLSv1.3
    Cipher    : TLS_AES_128_GCM_SHA256
    Verify return code: 0 (ok)

11. Verify deprecated protocol versions fail the handshake when disabled.

    $ openssl s_client -connect your.domain.tld:443 -servername your.domain.tld -tls1_1 </dev/null
    CONNECTED(00000003)
    ##### snipped #####
    no peer certificate available
    ##### snipped #####