Как заставить Apache2 в режиме прокси передавать username в kerberos?

<VirtualHost *:80>
RewriteEngine on
RewriteCond %{HTTP:Authorization} ^(.*)
RewriteRule .* - [e=HTTP_AUTHORIZATION:%1]



        ServerAdmin webmaster@localhost
        DocumentRoot /var/www/html
        ErrorLog ${APACHE_LOG_DIR}/error.log
        CustomLog ${APACHE_LOG_DIR}/access.log combined

ProxyPreserveHost On
ProxyRequests On
ProxyVia On

<Proxy *>
AuthType Kerberos
KrbAuthRealms DOMAIN.RU
KrbServiceName HTTP
Krb5Keytab /etc/apache2/sqserver.keytab
KrbMethodNegotiate on
KrbMethodK5Passwd on
require valid-user
SetEnv proxy-chain-auth 

</Proxy>

ProxyPass / http://192.168.56.124:80/
ProxyPassReverse / http://192.168.56.124:80/