Background:

I had to do quite a bit of searching in order to get Unifi to work correctly behind an Apache reverse proxy. I found that many people had come up with their own solutions with various odd, to say the least, configuration options in Apache that were mostly unnecessary. It took a little more searching, but eventually I did find how to prevent the WSS error from appearing too.

Before Beginning:

I assume that you have:

• Already configured Apache and Lets Encrypt previously.
• DNS already configured correctly and you can easily add another sub-domain.
• Already installed and configured Unifi Controller on a box, or VM somewhere.

As Unifi runs on a high (+1024) port, I installed the controller directly onto my Apache2 server.

By the end of the process you should have a functional Unifi controller on unfi.domain.com

Configuration:

Before beginning, ensure that you’ve created a new sudomain and pointed it to your public IP. Next, use lets encrypt to expand your certificate file to include the new domain. I usually run this in standalone mode and turn off apache2 while expanding the certificate.

sudo service apache2 stop
sudo letsencrypt certonly -d unifi.domain.com -d www.domain.com -d subdomain.domain.com

Once complete, start apache again.

Create a new site in /et/apache2/sites-available/ called unfi.domain.com-le-ssl.conf
Edit the file to contain the text below. Be sure to edit the references to your SSL certificate files, document root, servername, etc and IP address of your unifi host. Be aware that my unifi controller runs on the same host as my apache server. If needed, you can get the lets encrypt information from one of your other sites configuration files.

<IfModule mod_ssl.c>
<VirtualHost unifi.domain.com:443>
 # The ServerName directive sets the request scheme, hostname and port that
 # the server uses to identify itself. This is used when creating
 # redirection URLs. In the context of virtual hosts, the ServerName
 # specifies what hostname must appear in the request's Host: header to
 # match this virtual host. For the default virtual host (this file) this
 # value is not decisive as it is used as a last resort host regardless.
 # However, you must set it for any further virtual host explicitly.
 #ServerName www.example.com

ServerAdmin webmaster@domain.com
# DocumentRoot /var/www/html

# Available loglevels: trace8, ..., trace1, debug, info, notice, warn,
 # error, crit, alert, emerg.
 # It is also possible to configure the loglevel for particular
 # modules, e.g.
 #LogLevel info ssl:warn

ErrorLog ${APACHE_LOG_DIR}/error.log
 CustomLog ${APACHE_LOG_DIR}/access.log combined

# For most configuration files from conf-available/, which are
 # enabled or disabled at a global level, it is possible to
 # include a line for only one particular virtual host. For example the
 # following line enables the CGI configuration for this host only
 # after it has been globally disabled with "a2disconf".
 #Include conf-available/serve-cgi-bin.conf
SSLCertificateFile /etc/letsencrypt/live/domain.com/fullchain.pem
SSLCertificateKeyFile /etc/letsencrypt/live/domain.com/privkey.pem
Include /etc/letsencrypt/options-ssl-apache.conf
ServerName unifi.domain.com

ProxyRequests Off
ProxyPreserveHost On

# HSTS (mod_headers is required) (15768000 seconds = 6 months)
Header always set Strict-Transport-Security "max-age=15768000"

<Proxy *>
Order deny,allow
Allow from all
</Proxy>

SSLProxyEngine On
SSLProxyVerify none

SSLProxyCheckPeerCN off
SSLProxyCheckPeerName off
SSLProxyCheckPeerExpire off

AllowEncodedSlashes NoDecode
ProxyPass "/wss/" "wss://127.0.0.1:8443/wss/"
ProxyPassReverse "/wss/" "wss://127.0.0.1:8443/wss/"
ProxyPass "/" "https://127.0.0.1:8443/"
ProxyPassReverse "/" "https://127.0.0.1:8443/"

</VirtualHost>

</IfModule>

Then enable the site with:

sudo a2ensite unifi.subdomain.com-le-ssl.conf;sudo service apache2 reload

And that should do it! Any questions or comments, please post below.