Allow plugins to implement authentication backends

Design decisions:

* Config option specifies which of the registered backends is used
* Name conflicts (including with builtins) make the backend registration
  fail
* Builtin backends are not moved to plugins to avoid breaking existing
  setups confusion in general
* Builtin backends are exposed to plugins (and have been for some time);
  Important information and internal methods are hidden to prevent
  interference from malicious plugins

See doc/auth_backends.md and the related interface and function
documentation for details.

Closes #127.

1 files changed, 2 insertions, 12 deletions

diff --git a/moderation.go b/moderation.go
index d10661d..00d97b1 100644
--- a/moderation.go
+++ b/moderation.go
@@ -27,16 +27,6 @@ func (cc *ClientConn) Kick(reason string) {
 // network address from connecting again.
 func (cc *ClientConn) Ban() error {
 	cc.Kick("Banned by proxy.")
-	return authIface.Ban(cc.RemoteAddr().(*net.UDPAddr).IP.String(), cc.name)
-}
-
-// Unban removes a player from the ban list. It accepts both
-// network addresses and player names.
-func Unban(id string) error {
-	return authIface.Unban(id)
-}
-
-// Banned reports whether a network address is banned.
-func Banned(addr *net.UDPAddr) bool {
-	return authIface.Banned(addr)
+	ip := cc.RemoteAddr().(*net.UDPAddr).IP.String()
+	return DefaultAuth().Ban(ip, cc.name)
 }