//===== rAthena Documentation ================================
//= Login Server's MD5 Hash Check
//===== By: ==================================================
//= rAthena Dev Team
//===== Current Version: =====================================
//= 20120921
//===== Description: =========================================
//= This file outlines how the built-in MD5 Hash Check is
//= used and steps enable it.
//============================================================

In revision r16771, the login server received an update that allows it to perform
a server-side check of the client to find out it's MD5 hash. This update is an
effort towards ensuring that a user has either:
a.) not been tampered with the client
b.) using the client specific to that particular server

At present, we know that the client can only send the correct MD5 hash to the server
when using particular server types, so a diff is required to ensure that any client
can send the hash. A link to the required diff plugin for WeeDiffGen can be found at:
http://rathena.org/board/topic/70841-r16771-client-md5-hash-check/

Check conf/login_athena.conf for instruction on how to enable it.

In conf/login_athena.conf you will find the following:
// Client MD5 hash check
// Check client hash?
client_hash_check: off

This setting simply accepts on or off.


// Put your client hashes here, a player can login into the server using
// a hash with a group_id equal or lower the account group_id
// Format: group_id, hash
// Examples:
client_hash: 0, 113e195e6c051bb1cfb12a644bb084c5
client_hash: 99, cb1ea78023d337c38e8ba5124e2338ae

Once enabled, you would use those lines to configure this feature (or even as an example).
The group_id can be any of the groups in conf/groups.conf and can be particularly useful
if, for example, you wanted to restrict normal players from dual-clienting and use a lower
number for chat flooding, but wanted to allow dual-clienting and 255 lines before the chat
flood kicks in for your GMs.