server-configs-nginx/h5bp/tls/policy_strict.conf

# ----------------------------------------------------------------------
# | SSL policy - Strict                                                |
# ----------------------------------------------------------------------

# For services that don't need backward compatibility, the parameters below
# provide the highest level of security and performance.
#
# (!) This policy enforces a strong TLS configuration, which may raise
#     errors with old clients.
#     If a more compatible profile is required, use the "balanced" policy.
#
# (!) TLSv1.3 and its 0-RTT feature require NGINX >=1.15.4 and OpenSSL >=1.1.1
#     to be installed.
#
# (!) Don't enable `ssl_early_data` blindly! Requests sent within early data are
#     subject to replay attacks.
#
# (1) The NIST curves (prime256v1, secp384r1, secp521r1) are known to be weak
#     and potentially vulnerable.
#
#     Add them back to the parameter `ssl_ecdh_curve` below to support
#     Microsoft Edge and Safari.
#
#     https://safecurves.cr.yp.to/
#
# (2) Enables TLS 1.3 0-RTT, allows for faster resumption of TLS sessions.
#
# (!) Requests sent within early data are subject to replay attacks.
#     To protect against such attacks at the application layer, the
#     `$ssl_early_data` variable should be used:
#
#         proxy_set_header Early-Data $ssl_early_data;
#
#     The application should return response code 425 "Too Early" for anything
#     that could contain user supplied data.
#
#     https://developer.mozilla.org/en-US/docs/Web/HTTP/Status/425
#
# https://github.com/certbot/certbot/issues/6367
# https://github.com/mozilla/server-side-tls/issues/217
# https://nginx.org/en/docs/http/ngx_http_ssl_module.html

ssl_protocols TLSv1.2 TLSv1.3;
ssl_ciphers EECDH+CHACHA20:EECDH+AES;

# (1)
ssl_ecdh_curve X25519;

# (2)
#ssl_early_data on;