Apache HTTP Server /etc/apache2/mods-available/ssl.conf

# Pseudo Random Number Generator (PRNG):
# Configure one or more sources to seed the PRNG of the SSL library.
# The seed data should be of good random quality.
# WARNING! On some platforms /dev/random blocks if not enough entropy
# is available. This means you then cannot use the /dev/random device
# because it would lead to very long connection times (as long as
# it requires to make more entropy available). But usually those
# platforms additionally provide a /dev/urandom device which doesn't
# block. So, if available, use this one instead. Read the mod_ssl User
# Manual for more details.
#
SSLRandomSeed startup builtin
SSLRandomSeed startup file:/dev/urandom 512
SSLRandomSeed connect builtin
SSLRandomSeed connect file:/dev/urandom 512

##
##  SSL Global Context
##
##  All SSL configuration in this context applies both to
##  the main server and all SSL-enabled virtual hosts.
##

#
#   Some MIME-types for downloading Certificates and CRLs
#
AddType application/x-x509-ca-cert .crt
AddType application/x-pkcs7-crl .crl

#   Pass Phrase Dialog:
#   Configure the pass phrase gathering process.
#   The filtering dialog program (`builtin' is a internal
#   terminal dialog) has to provide the pass phrase on stdout.
SSLPassPhraseDialog  exec:/usr/share/apache2/ask-for-passphrase

#   Inter-Process Session Cache:
#   Configure the SSL Session Cache: First the mechanism
#   to use and second the expiring timeout (in seconds).
#   (The mechanism dbm has known memory leaks and should not be used).
#SSLSessionCache    dbm:${APACHE_RUN_DIR}/ssl_scache
SSLSessionCache     shmcb:${APACHE_RUN_DIR}/ssl_scache(512000)
SSLSessionCacheTimeout  300

#   Semaphore:
#   Configure the path to the mutual exclusion semaphore the
#   SSL engine uses internally for inter-process synchronization.
#   (Disabled by default, the global Mutex directive consolidates by default
#   this)
#Mutex file:${APACHE_LOCK_DIR}/ssl_mutex ssl-cache


#   SSL Cipher Suite:
#   List the ciphers that the client is permitted to negotiate. See the
#   ciphers(1) man page from the openssl package for list of all available
#   options.
#   Enable only secure ciphers:
SSLCipherSuite HIGH:!aNULL

# SSL server cipher order preference:
# Use server priorities for cipher algorithm choice.
# Clients may prefer lower grade encryption.  You should enable this
# option if you want to enforce stronger encryption, and can afford
# the CPU cost, and did not override SSLCipherSuite in a way that puts
# insecure ciphers first.
# Default: Off
#SSLHonorCipherOrder on

#   The protocols to enable.
#   Available values: all, SSLv3, TLSv1, TLSv1.1, TLSv1.2, TLSv1.3
#   SSL v2  is no longer supported
SSLProtocol all -SSLv2 -SSLv3 -TLSv1 -TLSv1.1

#   Allow insecure renegotiation with clients which do not yet support the
#   secure renegotiation protocol. Default: Off
#SSLInsecureRenegotiation on

#   Whether to forbid non-SNI clients to access name based virtual hosts.
#   Default: Off
#SSLStrictSNIVHostCheck On

# Warning: Session Tickets require regular restarting of the server!
# Make sure you do this (e.g. via logrotate) before changing this setting!
SSLSessionTickets off