httpd-proxy.conf

#
# This configuration file enables the default "Welcome" page if there
# is no default index page present for the root URL.  To disable the
# Welcome page, comment out all the lines below.
#
# NOTE: if this file is removed, it will be restored on upgrades.
#
Listen 443
SSLProtocol         all -SSLv3 -TLSv1 -TLSv1.1
SSLCipherSuite      HIGH:!aNULL:!MD5
SSLVerifyClient     none
SSLCertificateFile  /etc/ssl/certs/node-selfsigned.crt
SSLCertificateKeyFile   /etc/ssl/private/node-selfsigned.key
LogLevel            warn

<VirtualHost *:443>

SSLEngine           on
SSLProxyEngine On

RewriteEngine on
RewriteMap lowercase int:tolower

#This sets the variable to env:
RewriteRule ^ - [E=SERVER_NAME:${lowercase:%{SERVER_NAME}}]

#Now interpolate makes variables available for proxypass & proxypassreverse:
ProxyPassInterpolateEnv On
ProxyPass / http://${SERVER_NAME}.s3-website-us-east-1.amazonaws.com/ interpolate
ProxyPassReverse / http://${SERVER_NAME}.s3-website-us-east-1.amazonaws.com/ interpolate

</VirtualHost>