RequestHeader set X-AUTH-DECODE "expr=%{HTTP:Authorization}"
RequestHeader edit X-AUTH-DECODE "^Basic (.*)$" $1
RequestHeader set USER "expr=%{unbase64:%{HTTP:X-AUTH-DECODE}}"
RequestHeader set PASSWORD "expr=%{unbase64:%{HTTP:X-AUTH-DECODE}}"
RequestHeader edit USER "(.*):.*$" $1
RequestHeader edit PASSWORD ".*:(.*)$" $1
RewriteRule .* - [E=HTTP_USER:%{HTTP:User}]
RewriteRule .* - [E=HTTP_PASSWORD:%{HTTP:Password}]
RewriteRule .* - [E=HTTP_AUTHORIZATION:%{HTTP:Authorization}]