You could try something like this.

geo $need_auth {
default 1;
192.168.1.0/24 0;
}

server {
...
location / {
if ($need_auth) {
<auth>
}
}
}
> Hi all,
>
> I have a service which should be protected using Basic Authentication,
> but this authentication should be enabled only for people who connect
> to my service from "the outside of my LAN". Other people (inside LAN)
> should not have any authentication.
>
> Is this possible? How to do that? I couldn't figure out how to use
> combination of allow/deny with basic authentication for certain
> location (maybe this is wrong way...).
>
> Cheers,
> Kamil
>
>