%%%----------------------------------------------------------------------
%%% File    : ejabberd_auth_anonymous.erl
%%% Author  : Mickael Remond <mickael.remond@process-one.net>
%%% Purpose : Anonymous feature support in ejabberd
%%% Created : 17 Feb 2006 by Mickael Remond <mremond@process-one.net>
%%%
%%%
%%% ejabberd, Copyright (C) 2002-2010   ProcessOne
%%%
%%% This program is free software; you can redistribute it and/or
%%% modify it under the terms of the GNU General Public License as
%%% published by the Free Software Foundation; either version 2 of the
%%% License, or (at your option) any later version.
%%%
%%% This program is distributed in the hope that it will be useful,
%%% but WITHOUT ANY WARRANTY; without even the implied warranty of
%%% MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
%%% General Public License for more details.
%%%
%%% You should have received a copy of the GNU General Public License
%%% along with this program; if not, write to the Free Software
%%% Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
%%% 02111-1307 USA
%%%
%%%----------------------------------------------------------------------

-module(ejabberd_auth_anonymous).
-author('mickael.remond@process-one.net').

-export([start/1,
	 allow_anonymous/1,
	 is_sasl_anonymous_enabled/1,
	 is_login_anonymous_enabled/1,
	 anonymous_user_exist/2,
	 allow_multiple_connections/1,
	 register_connection/3,
	 unregister_connection/3
	]).


%% Function used by ejabberd_auth:
-export([login/2,
	 set_password/3,
	 check_password/3,
	 check_password/5,
	 try_register/3,
	 dirty_get_registered_users/0,
	 get_vh_registered_users/1,
	 get_password/2,
	 get_password/3,
	 is_user_exists/2,
	 remove_user/2,
	 remove_user/3,
	 plain_password_required/0]).

-include("ejabberd.hrl").
-include("jlib.hrl").
-record(anonymous, {us, sid}).

%% Create the anonymous table if at least one virtual host has anonymous features enabled
%% Register to login / logout events
start(Host) ->
    %% TODO: Check cluster mode
    update_tables(),
    mnesia:create_table(anonymous, [{ram_copies, [node()]},
				    {type, bag}, {local_content, true},
				    {attributes, record_info(fields, anonymous)}]),
    mnesia:add_table_copy(anonymous, node(), ram_copies),
    %% The hooks are needed to add / remove users from the anonymous tables
    ejabberd_hooks:add(sm_register_connection_hook, Host,
		       ?MODULE, register_connection, 100),
    ejabberd_hooks:add(sm_remove_connection_hook, Host,
		       ?MODULE, unregister_connection, 100),
    ok.

%% Return true if anonymous is allowed for host or false otherwise
allow_anonymous(Host) ->
    lists:member(?MODULE, ejabberd_auth:auth_modules(Host)).

%% Return true if anonymous mode is enabled and if anonymous protocol is SASL
%% anonymous protocol can be: sasl_anon|login_anon|both
is_sasl_anonymous_enabled(Host) ->
    case allow_anonymous(Host) of
	false -> false;
	true ->
	    case anonymous_protocol(Host) of
		sasl_anon -> true;
		both      -> true;
		_Other    -> false
	    end
    end.

%% Return true if anonymous login is enabled on the server
%% anonymous login can be use using standard authentication method (i.e. with
%% clients that do not support anonymous login)
is_login_anonymous_enabled(Host) ->
    case allow_anonymous(Host) of
	false -> false;
	true  ->
	    case anonymous_protocol(Host) of
		login_anon -> true;
		both       -> true;
		_Other     -> false
	    end
    end.

%% Return the anonymous protocol to use: sasl_anon|login_anon|both
%% defaults to login_anon
anonymous_protocol(Host) ->
    case ejabberd_config:get_local_option({anonymous_protocol, Host}) of
	sasl_anon  -> sasl_anon;
	login_anon -> login_anon;
	both       -> both;
	_Other     -> sasl_anon
    end.

%% Return true if multiple connections have been allowed in the config file
%% defaults to false
allow_multiple_connections(Host) ->
    ejabberd_config:get_local_option(
      {allow_multiple_connections, Host}) =:= true.

%% Check if user exist in the anonymus database
anonymous_user_exist(User, Server) ->
    LUser = jlib:nodeprep(User),
    LServer = jlib:nameprep(Server),
    US = {LUser, LServer},
    case catch mnesia:dirty_read({anonymous, US}) of
	[] ->
	    false;
	[_H|_T] ->
	    true
    end.

%% Remove connection from Mnesia tables
remove_connection(SID, LUser, LServer) ->
    US = {LUser, LServer},
    F = fun() ->
		mnesia:delete_object({anonymous, US, SID})
        end,
    mnesia:async_dirty(F).

%% Register connection
register_connection(SID, #jid{luser = LUser, lserver = LServer}, Info) ->
    AuthModule = xml:get_attr_s(auth_module, Info),
    case AuthModule == ?MODULE of
	true ->
	    US = {LUser, LServer},
	    mnesia:async_dirty(
	      fun() -> mnesia:write(#anonymous{us = US, sid=SID})
	      end);
	false ->
	    ok
    end.

%% Remove an anonymous user from the anonymous users table
unregister_connection(SID, #jid{luser = LUser, lserver = LServer}, _) ->
    purge_hook(anonymous_user_exist(LUser, LServer),
	       LUser, LServer),
    remove_connection(SID, LUser, LServer).

%% Launch the hook to purge user data only for anonymous users
purge_hook(false, _LUser, _LServer) ->
    ok;
purge_hook(true, LUser, LServer) ->
    ejabberd_hooks:run(anonymous_purge_hook, LServer, [LUser, LServer]).

%% ---------------------------------
%% Specific anonymous auth functions
%% ---------------------------------

%% When anonymous login is enabled, check the password for permenant users
%% before allowing access
check_password(User, Server, Password) ->
    check_password(User, Server, Password, undefined, undefined).
check_password(User, Server, _Password, _Digest, _DigestGen) ->
    %% We refuse login for registered accounts (They cannot logged but
    %% they however are "reserved")
    case ejabberd_auth:is_user_exists_in_other_modules(?MODULE,
						       User, Server) of
	%% If user exists in other module, reject anonnymous authentication
	true  -> false;
	%% If we are not sure whether the user exists in other module, reject anon auth
	maybe  -> false;
	false -> login(User, Server)
    end.

login(User, Server) ->
    case is_login_anonymous_enabled(Server) of
	false -> false;
	true  ->
	    case anonymous_user_exist(User, Server) of
		%% Reject the login if an anonymous user with the same login
		%% is already logged and if multiple login has not been enable
		%% in the config file.
		true  -> allow_multiple_connections(Server);
		%% Accept login and add user to the anonymous table
		false -> true
	    end
    end.

%% When anonymous login is enabled, check that the user is permanent before
%% changing its password
set_password(User, Server, _Password) ->
    case anonymous_user_exist(User, Server) of
	true ->
	    ok;
	false ->
	    {error, not_allowed}
    end.

%% When anonymous login is enabled, check if permanent users are allowed on
%% the server:
try_register(_User, _Server, _Password) ->
    {error, not_allowed}.

dirty_get_registered_users() ->
    [].

get_vh_registered_users(_Server) ->
    [].


%% Return password of permanent user or false for anonymous users
get_password(User, Server) ->
    get_password(User, Server, "").

get_password(User, Server, DefaultValue) ->
    case anonymous_user_exist(User, Server) or login(User, Server) of
	%% We return the default value if the user is anonymous
	true ->
	    DefaultValue;
	%% We return the permanent user password otherwise
	false ->
	    false
    end.

%% Returns true if the user exists in the DB or if an anonymous user is logged
%% under the given name
is_user_exists(User, Server) ->
    anonymous_user_exist(User, Server).

remove_user(_User, _Server) ->
    {error, not_allowed}.

remove_user(_User, _Server, _Password) ->
    not_allowed.

plain_password_required() ->
    false.

update_tables() ->
    case catch mnesia:table_info(anonymous, local_content) of
	false ->
	    mnesia:delete_table(anonymous);
	_ ->
	    ok
    end.