[Users] username prefixes

I'm looking for opinions from people who may have already done something like this: Suppose I've got some entries in the location table that I want the whole world to get to, and some locations that I want only authorized users to get to. Some of these locations have $resources$ attached, but even so they aren't hard-coded in my config, they register just like JoeUser on a SIP phone. I'm thinking of handling this with a prefix on the username, like auth.foobar vs foobar, like this: if (!uri=~"^sip:auth\.") { log(1,"---not auth destination\n"); if (lookup("location")) { append_hf("P-hint: non-auth usrloc\r\n"); route(1); } } # rest of stuff requires authorization if (!proxy_authorize("", "subscriber")) { proxy_challenge("", "0"); return; } consume_credentials(); <snip rest of INVITE handling> Is this naive, stupid, already handled in XYZ, or reasonable? Thanks, -mark