Google Cloud Platform – Using Let’s Encrypt TLS with Google Load Balancer

I have written a pair of how-tos for running Let's Encrypt SSL certs on CentOS: initial setup & cronning it.

And my per-domain (I use the file naming convention of z-<[sub-]domain-tld>.conf) Apache config files look like this:

<VirtualHost *:80>
ServerName domain.tld
Redirect permanent / https://domain.tld/
</VirtualHost>

<VirtualHost *:443>
    SSLCertificateFile /etc/letsencrypt/live/domain.tld/cert.pem
    SSLCertificateKeyFile /etc/letsencrypt/live/domain.tld/privkey.pem
    SSLCertificateChainFile /etc/letsencrypt/live/domain.tld/fullchain.pem
    DocumentRoot /var/www/domain
    ServerName domain.tld
    ErrorLog logs/domain-error_log
    CustomLog logs/domain-access_log \
          "%t %h %{SSL_PROTOCOL}x %{SSL_CIPHER}x \"%r\" %b"
    ServerAdmin user@domain.tld

    SSLEngine on

<Files ~ "\.(cgi|shtml|phtml|php3?)$">
    SSLOptions +StdEnvVars
</Files>
<Directory "/var/www/cgi-bin">
    SSLOptions +StdEnvVars
</Directory>

SetEnvIf User-Agent ".*MSIE.*" \
         nokeepalive ssl-unclean-shutdown \
         downgrade-1.0 force-response-1.0

    <Directory "/var/www/domain">
         Options All +Indexes +FollowSymLinks
         AllowOverride All
         Order allow,deny
         Allow from all
    </Directory>

</VirtualHost>

And my ssl.conf looks like this:

#SSL options for all sites
Listen 443
SSLPassPhraseDialog  builtin
SSLSessionCache         shmcb:/var/cache/mod_ssl/scache(512000)
SSLSessionCacheTimeout  300
Mutex sysvsem default
SSLRandomSeed startup file:/dev/urandom  1024
SSLRandomSeed connect builtin
SSLCryptoDevice builtin
SSLCompression          off
SSLHonorCipherOrder     on
SSLProtocol all -SSLv2 -SSLv3 -TLSv1 -TLSv1.1
SSLCipherSuite ECDHE-ECDSA-AES256-GCM-SHA384:ECDHE-RSA-AES256-GCM-SHA384:ECDHE-ECDSA-CHACHA20-POLY1305:ECDHE-RSA-CHACHA20-POLY1305:ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES128-GCM-SHA256:ECDHE-ECDSA-AES256-SHA384:ECDHE-RSA-AES256-SHA384:ECDHE-ECDSA-AES128-SHA256:ECDHE-RSA-AES128-SHA256

Using Let's Encrypt to get SSL certs (and get your site up to an "A" rating from SSL Labs) is pretty straight-forward - once you get past some of the arcana of the Apache configs and LE command-line arguments.

You can use self-signed certificates on the VMs. In fact, the self-signed certs I'm using with NGINX on my VMs all expired about 8 months ago. I don't believe the load balancer does any validation on the cert itself--it is just a necessary part of the SSL handshake.

You could attempt to generate something in the instance startup for its own IP, and a cron job to renew it. As above, I don't think it's necessary.

Google does not automate the replacement of the cert, but you can script it. The gcloud command-line utility has commands for creating and updating most resources including certificates and load balancers.