SSL configuration for high security rating

ssl.conf

# HTTP Strict Transport Security: tells browsers to require https:// without first checking
# the http:// version for a redirect. Warning: it is difficult to change your mind.
#
#    max-age: length of requirement in seconds (31536000 = 1 year)
#    includeSubdomains: force SSL for *ALL* subdomains (remove if this is not what you want)
#    preload: indicates you want browsers to ship with HSTS preloaded for your domain.
#
#    Submit your domain for preloading in browsers at: https://hstspreload.appspot.com
add_header Strict-Transport-Security 'max-age=31536000; includeSubDomains; preload';

# If you won't/can't turn on HTTPS for *all* subdomains, use this simpler version:
#add_header Strict-Transport-Security 'max-age=31536000';

# Prefer certain ciphersuites, to enforce Forward Secrecy and avoid known vulnerabilities.
#
# Forces forward secrecy in all browsers and clients that can use TLS,
# but with a small exception (DES-CBC3-SHA) for IE8/XP users.
#
# Reference client: https://www.ssllabs.com/ssltest/analyze.html
ssl_prefer_server_ciphers on;
ssl_ciphers 'kEECDH+ECDSA+AES128 kEECDH+ECDSA+AES256 kEECDH+AES128 kEECDH+AES256 kEDH+AES128 kEDH+AES256 DES-CBC3-SHA +SHA !aNULL !eNULL !LOW !MD5 !EXP !DSS !PSK !SRP !kECDH !CAMELLIA !RC4 !SEED';

# Now let's really get fancy, and pre-generate a 2048 bit random parameter
# for DH elliptic curves. If not created and specified, default is only 1024 bits.
#
# Generated by OpenSSL with the following command:
#   openssl dhparam -outform pem -out dhparam2048.pem 2048
ssl_dhparam /etc/nginx/ssl/dhparam.pem;

# Cut out the old, broken, insecure SSLv2 and SSLv3 entirely.
ssl_protocols TLSv1.2 TLSv1.1 TLSv1;

# optional: turn on session resumption, using a 10 min cache shared across nginx processes
# as recommended by http://nginx.org/en/docs/http/configuring_https_servers.html
ssl_session_cache   shared:SSL:10m;
ssl_session_timeout 10m;
keepalive_timeout   70;

# Buffer size of 1400 bytes fits in one MTU.
# nginx 1.5.9+ ONLY
ssl_buffer_size 1400;

# OCSP stapling - means nginx will poll the CA for signed OCSP responses,
# and send them to clients so clients don't make their own OCSP calls.
# https://en.wikipedia.org/wiki/OCSP_stapling
#
# while the ssl_certificate above may omit the root cert if the CA is trusted,
# ssl_trusted_certificate below must point to a chain of **all** certs
# in the trust path - (your cert, intermediary certs, root cert)
#
# 8.8.8.8 and 8.8.4.4 below are Google's public IPv4 DNS servers.
# nginx will use them to talk to the CA.
ssl_stapling on;
ssl_stapling_verify on;
resolver 8.8.8.8 8.8.4.4 valid=86400;
resolver_timeout 10;