From 95ef06b7683c9ca29fdca07507e2ed3b7bacd7d6 Mon Sep 17 00:00:00 2001
From: Badlop <badlop@process-one.net>
Date: Tue, 18 Sep 2018 11:38:10 +0200
Subject: [PATCH] Copy mod_filter.erl from https://github.com/knobo/mod_filter

---
 mod_filter/src/mod_filter.erl | 107 ++++++++++++++++++++++++++++++++++
 1 file changed, 107 insertions(+)
 create mode 100644 mod_filter/src/mod_filter.erl

diff --git a/mod_filter/src/mod_filter.erl b/mod_filter/src/mod_filter.erl
new file mode 100644
index 0000000..aa431ce
--- /dev/null
+++ b/mod_filter/src/mod_filter.erl
@@ -0,0 +1,107 @@
+%%%----------------------------------------------------------------------
+%%% File    : mod_filter.erl
+%%% Author  : Magnus Henoch <henoch@dtek.chalmers.se>
+%%% Purpose : flexible filtering by server policy
+%%% Created : 21 Sep 2005 by Magnus Henoch <henoch@dtek.chalmers.se>
+%%% Updated : 14 Jan 2016 by John Brodie <john@brodie.me>
+%%%----------------------------------------------------------------------
+
+-module(mod_filter).
+-author('henoch@dtek.chalmers.se').
+%% -vsn('$Revision$ ').
+
+-behaviour(gen_mod).
+
+-export([start/2, stop/1,
+	 filter_packet/1, mod_opt_type/1]).
+
+-include("logger.hrl").
+-include("ejabberd.hrl").
+-include("jlib.hrl").
+
+start(_Host, _Opts) ->
+    ejabberd_hooks:add(filter_packet, global, ?MODULE, filter_packet, 100).
+
+
+stop(_Host) ->
+    ejabberd_hooks:delete(filter_packet, global, ?MODULE, filter_packet, 100).
+
+%% Return drop to drop the packet, or the original input to let it through.
+%% From and To are jid records.
+filter_packet(drop) ->
+    drop;
+filter_packet({From, To, Packet} = Input) ->
+    %% It probably doesn't make any sense to block packets to oneself.
+    R = if From#jid.luser == To#jid.luser,
+	   From#jid.lserver == To#jid.lserver ->
+		Input;
+	   true ->
+		check_stanza(Input)
+	end,
+    ?DEBUG("filtering packet...~nFrom: ~p~nTo: ~p~nPacket: ~p~nResult: ~p",
+	   [From, To, Packet, R]),
+    case R of
+	{drop, _} -> drop;
+	{drop, _, _} -> drop;
+	_ -> R
+    end.
+
+check_stanza({_From, _To, #xmlel{name = StanzaType}} = Input) ->
+    AccessRule = case StanzaType of
+		     <<"presence">> ->
+			 mod_filter_presence;
+		     <<"message">> ->
+			 mod_filter_message;
+		     <<"iq">> ->
+			 mod_filter_iq
+		 end,
+    check_stanza_type(AccessRule, Input).
+
+check_stanza_type(AccessRule, {From, To, _Packet} = Input) ->
+    FromAccess = acl:match_rule(global, AccessRule, From),
+    case FromAccess of
+	allow ->
+	    check_access(Input);
+	deny ->
+	    {drop, AccessRule, sender};
+	ToAccessRule ->
+	    ToAccess = acl:match_rule(global, ToAccessRule, To),
+	    case ToAccess of
+		allow ->
+		    check_access(Input);
+		deny ->
+		    {drop, AccessRule, receiver}
+	    end
+    end.
+
+check_access({From, To, _Packet} = Input) ->
+    %% Beginning of a complicated ACL matching procedure.
+    %% The access option given to the module applies to senders.
+
+    %% XXX: there are no "global" module options, and we don't know
+    %% anymore what "host" we are on.  Thus hardcoding access rule.
+    %%AccessRule = gen_mod:get_module_opt(global, ?MODULE, access, all),
+    AccessRule = mod_filter,
+    FromAccess = acl:match_rule(global, AccessRule, From),
+    %% If the rule results in 'allow' or 'deny', treat that as the
+    %% result.  Else it is a rule to be applied to the receiver.
+    case FromAccess of
+	allow ->
+	    Input;
+	deny ->
+	    {drop, sender};
+	ToAccessRule ->
+	    ToAccess = acl:match_rule(global, ToAccessRule, To),
+	    case ToAccess of
+		allow ->
+		    Input;
+		deny ->
+		    {drop, receiver}
+	    end
+    end.
+
+mod_opt_type(access) ->
+    fun (A) when is_atom(A) -> A end;
+
+mod_opt_type(_) ->
+    [access].