Allow only one User-Agent, block the rest in nginx?

Question

new to this site so i'll keep it brief:

I have currently:

    if ($http_user_agent ~* (A-certain-self-made-User-Agent-here)) {
            return 200;
    }

Which works very well. (Tested by switching 200 to 403).

My question is: Is there a way in: /etc/nginx/sites-enabled/default to make it allow only ONE User-Agent and deny the rest?

I know this seems stupid, but it's something i'd like to have done, (if possible). Like maybe this?:

    if (http_user_agent ~*(user-agent)) {
           return 200;
    else
           return 403;
    }

Answer 1

Try this:

if ($http_user_agent !~* (A-certain-self-made-User-Agent-here)) {
        return 403;
}

This should be a 'not match' on your certain user agent. Reference info here: HttpRewriteModule

Answer 2

if ($http_user_agent !~* "A-certain-self-made-User-Agent-here") {
    return 403;
}

is working on my site.