==========================================================================
 Authentication
--------------------------------------------------------------------------

This file describes how the authentication process works and how the servers use sessions.

Contents:
* Sessions
* Client Session Ownership
* Client Authentication
* Server Authentication
* Timeout Timers


==========================================================================
 Sessions
--------------------------------------------------------------------------

Client Session:
	This session represents an account/character.
	It is identified by account_id, char_id, login_id1, login_id2 and sex.
	Only one server can own the client session.
	Only the owner can request changes to the account/character data.

Char-server Session:
	This session represents a char-server. (in the login-server)
	It is identified by a unique cookie.
	It allows the char-server to reconnect, reclaim the client sessions owned before the disconnect and continue as if nothing happened.
	Note: each char-server that is connected to the login-server must use a different username+password

Map-server Session:
	This session represents a map-server. (in the char-server)
	It is identified by a unique cookie.
	It allows the map-server to reconnect, reclaim the client sessions owned before the disconnect and continue as if nothing happened.
	Note: each map-server that is connected to the char-server must use the same username+password as the char-server


==========================================================================
 Client Session Ownership
--------------------------------------------------------------------------

     (passive)           (active)          (passive)
    login-server ------ char-server ------ map-server

Login-server:
	Receives client session requests from the char-server(s).

Char-server:
	Sends client session requests to the login-server.
	Sends client sessions to the map-server(s).

Map-server:
	Receives client sessions from the char-server.

Changing map-server:
	1) ...(normal play) (client session owned by map-server1)
	2) Player enters a map that is in map-server2.
	3) Map-server1 sends save data to char-server and receives an ack.
	4) Map-server1 sends client session to map-server2 via char-server and receives a reply.
	5.a) [if failed] Player is sent to save point. (client session owned by map-server1)
	5.b) [if ok] (client session owned by map-server2)
	5.b.1) Map-server1 sends change map server to client.
	5.b.2) Client disconnects. (to map-server2)

Character select:
	1) ...(normal play) (client session owned by map-server)
	2) Client requests character select.
	3) Map-server sends final save data to char-server and receives an ack.
	4) Map-server sends client session to char-server and receives an ack. (client session owned by char-server)
	5) Map-server sends character select ok to client.
	6) Client disconnects. (to char-server)


==========================================================================
 Client Authentication
--------------------------------------------------------------------------

Login-server:
	1) Client connects to login-server.
	2.a) [if raw password] Client sends username and password to login-server.
	2.b) [if hash password]:
	2.b.1) Client requests hash key (password salt) from login-server.
	2.b.2) Login-server replies with new hash key to client.
	2.b.3) Client sends username and hashed password to login-server.
	3.a) [if auth failed] Login-server rejects client and client disconnects. (END)
	3.b) [if auth ok]:
	3.b.a) [if client session owned by a char-server] Login-server requests kick from char-server and rejects client and client disconnects. (END)
	3.b.b) [else]:
	3.b.b.1) Login-server (re)creates client session with new login_id1/login_id2. (client session owned by login-server)
	3.b.b.2) Login-server sends account_id, login_id1, login_id2, sex and list of servers to client.
	4) Client disconnects. (server selection is done offline; to char-server)

Char-server:
	1) Client connects to char-server.
	2) Client sends account_id, login_id1, login_id2 and sex to char-server.
	3.a) [if client session exists] (from map-server; character select)
	3.a.1) [if client session matches] Auth ok.
	3.a.b) [else]: Auth failed.
	3.b) [else]: (from login-server; after server selection)
	3.b.1) Char-server sends account_id, login_id1, login_id2 and sex to login-server. (request client session)
	3.b.2.a) [if client session matches and not owned by another char-server] Login-server replies auth ok to char-server. (client session owned by char-server)
	4.b.2.b) [else] Login-server replies auth failed to char-server.
	5.a) [if auth failed] Char-server rejects client and client disconnects. (END)
	5.b) [if auth ok]:
	5.b.a) [if client session owned by a map-server] Char-server requests kick from map-server and rejects client and client disconnects. (END)
	5.b.b) [if client session has a client attached] Char-server kicks other client, rejects client and client disconnects. (END)
	5.b.c) [if client session doesn't exist] Char-server creates a client session. (client session owned by char-server)
	6) Char-server sets an invalid char_id and attaches the client to the client session.
	7) Char-server sends list of characters to client.
	8) ...
	9) Client sends character selection to char-server.
	10) Char-server updates client session. (if another selection is received, the client is kicked and the session is released)
	11) Char-server sends client session to target map-server and receives an ack. (client session owned by map-server)
	12) Char-server sends char_id, mapname and map-server address to client.
	13) Client disconnects. (to map-server)

Map-server:
	1) Client connects to map-server.
	2) Client sends account_id, char_id, login_id1 and sex to map-server.
	3.a) [if not found or doesn't match] Map-server rejects client and client disconnects. (END)
	3.b) [else] ...(normal play)


==========================================================================
 Server Authentication
--------------------------------------------------------------------------

Char-server connecting:
	1) Char-server connects to login-server.
	2) Char-server sends username and password to login-server.
	3.a) [if auth failed or char-server session exists] Login-server rejects char-server and char-server disconnects. (END)
	3.b) [else]:
	3.b.1) Login-server creates char-server session with a unique random cookie.
	3.b.2) Login-server replies login ok and cookie to char-server.
	3.b.3) ...(normal server operation)

Char-server reconnecting:
	1) Char-server connects to login-server.
	2) Char-server sends cookie to login-server.
	3.a) [if cookie exists and is not connected]:
	3.a.1) Login-server starts timeout timers on all the client sessions that were owned before the disconnect.
	3.a.2) Login-server replies login ok to char-server.
	3.a.3) Char-server reclaims client sessions from the login-server.
	3.a.4) ...(normal server operation)
	3.b) [else]:
	3.b.1) Login-server rejects char-server.
	3.b.2) Char-server kicks all players, discarding changes.
	3.b.3) Char-server disconnects.
	3.b.4) ...(continue in the previous case 'Char-server connecting')

Map-server connecting:
	1) Map-server connects to char-server.
	2) Map-server sends username and password to char-server.
	3.a) [if auth does not match] Char-server rejects map-server and map-server disconnects. (END)
	3.b) [else]:
	3.b.1) Char-server creates map-server session with a unique random cookie.
	3.b.2) Char-server replies login ok and cookie to map-server.
	3.b.3) ...(normal server operation)

Map-server reconnecting:
	1) Map-server connects to char-server.
	2) Map-server sends cookie to char-server.
	3.a) [if cookie exists and is not connected]:
	3.a.1) Char-server starts timeout timers on all the client sessions that were owned before the disconnect.
	3.a.2) Char-server replies login ok to map-server.
	3.a.3) Map-server reclaims client sessions from the char-server.
	3.a.4) ...(normal server operation)
	3.b) [else]:
	3.b.1) Char-server rejects map-server.
	3.b.2) Map-server kicks all players, discarding changes.
	3.b.3) Map-server disconnects.
	3.b.4) ...(continue in the previous case 'Map-server connecting')


==========================================================================
 Timeout Timers
--------------------------------------------------------------------------

Client moving from login-server to char-server:
	Timeout timer on the client session in the login-server.
	If time runs out the client session is released. (char-server can't authenticate client)
	It is canceled when the client session is authenticated.

Client moving from char-server to map-server:
	Timeout timer on the client session in the map-server.
	If time runs out the client session is released. (client can't enter map-server)
	It is canceled when the client session is authenticated.

Char-server reconnecting to the login-server:
	Timeout timer on the char-server session in the login-server.
	If time runs out the char-server session is released. (char-server can't reconnect)
	It is canceled when the char-server reconnects. (and starts the timers of the next case)

Char-server reclaiming client sessions:
	Timeout timer on the client session in the login-server, that was owned by the disconnected char-server.
	If time runs out the client session is released. (char-server can't reclaim session)
	It is canceled when the client session is reclaimed.

Map-server reconnecting to the char-server:
	Timeout timer on the map-server session in the char-server.
	If time runs out the map-server session is released. (map-server can't reconnect)
	It is canceled when the map-server reconnects. (and starts the timers of the next case)

Map-server reclaiming client sessions:
	Timeout timer on the client session in the char-server, that was owned by the disconnected map-server.
	If time runs out the client session is released. (map-server can't reclaim session)
	It is canceled when the client session is reclaimed.