Apache Reverse Proxy with Basic Authentication

You can follow the instructions here: Authentication, Authorization and Access Control. The main difference for your reverse proxy is that you'll want to put the auth stuff inside a Location block, even though the docs say that they're only allowed in Directory blocks:

<Location />
    AuthType Basic
    ...
</Location>

Outside the Location block you can put your proxy commands, such as:

ProxyPass / 

First, check if your apache2 has the utils package

sudo apt-get install apache2-utils

Then, set the username and password.

sudo htpasswd -c /etc/apache2/.htpasswd <username>

After that, edit your reverse proxy to use the authentication

<VirtualHost *:80>
    ProxyPreserveHost On

    ProxyPass / 
    ProxyPassReverse / 

    Timeout 5400
    ProxyTimeout 5400

    ServerName dev.mydomain.com
    ServerAlias *.dev.mydomain.com

    <Proxy *>
        Order deny,allow
        Allow from all
        Authtype Basic
        Authname "Password Required"
        AuthUserFile /etc/apache2/.htpasswd
        Require valid-user
    </Proxy>
</virtualhost>

At least, update your apache

sudo service apache2 reload

Here's the config I have used to accomplish basic authentication over https against a database. My backend server is running Tomcat and I connect to it using AJP. The funny port number (4443) is because the standard port (443) was already used, and I didn't want to configure several https services on the same port.

<IfModule mod_ssl.c>
NameVirtualHost *:4443
<VirtualHost *:4443>
        ServerAdmin webmaster@localhost
        ServerName ws.myserver.se
        ServerAlias ws.myserveralias.se
        ErrorLog /var/log/apache2/ajpProxy.error.log

        # Possible values include: debug, info, notice, warn, error, crit,
        # alert, emerg.
        LogLevel info

        CustomLog /var/log/apache2/ajpProxy.log combined

        DBDriver mysql
        DBDParams "host=127.0.0.1 port=3306 user=proxyAuthUser pass=yourDbPasswordHere dbname=yourDbName"
        DBDMin  4
        DBDKeep 8
        DBDMax  20
        DBDExptime 300        

        <Proxy *>
              # core authentication and mod_auth_basic configuration
              # for mod_authn_dbd
              AuthType Basic
              AuthName "Backend auth name"
              AuthBasicProvider dbd

             # core authorization configuration
              Require valid-user

              # mod_authn_dbd SQL query to authenticate a user
              AuthDBDUserPWQuery \
                "SELECT password FROM user WHERE emailAddress = %s"

              AddDefaultCharset Off
              Order deny,allow
              Allow from all
        </Proxy>

        ProxyPass / ajp://localhost:8009/
        ProxyPassReverse / ajp://localhost:8009/

        #   SSL Engine Switch:
        #   Enable/Disable SSL for this virtual host.
        SSLEngine on

        #   A self-signed (snakeoil) certificate can be created by installing
        #   the ssl-cert package. See
        #   /usr/share/doc/apache2.2-common/README.Debian.gz for more info.
        #   If both key and certificate are stored in the same file, only the
        #   SSLCertificateFile directive is needed.
        SSLCertificateFile    /etc/apache2/ssl/yourCertificateFile.crt
        SSLCertificateKeyFile /etc/apache2/ssl/yourPrivateKeyFile.key
        <FilesMatch "\.(cgi|shtml|phtml|php)$">
                SSLOptions +StdEnvVars
        </FilesMatch>
        <Directory /usr/lib/cgi-bin>
                SSLOptions +StdEnvVars
        </Directory>

        BrowserMatch "MSIE [2-6]" \
                nokeepalive ssl-unclean-shutdown \
                downgrade-1.0 force-response-1.0
        # MSIE 7 and newer should be able to use keepalive
        BrowserMatch "MSIE [17-9]" ssl-unclean-shutdown
</VirtualHost>
</IfModule>