Initial import of the prosody otr module

Signed-off-by: David Goulet <dgoulet@ev0ke.net>

mod_otr.lua

@@ -0,0 +1,79 @@
+--
+-- Copyright (C) 2014 - David Goulet <dgoulet@ev0ke.net>
+--
+-- This program is free software; you can redistribute it and/or modify
+-- it under the terms of the GNU General Public License, version 2 only,
+-- as published by the Free Software Foundation.
+--
+-- 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.,
+-- 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+--
+
+local st = require "util.stanza";
+
+-- Module option.
+-- 
+-- This tells the module policy which for now there is two choices.
+--		mandatory: OTR will be enforced
+--		optional:  Warn user to suggest OTR. (default)
+local policy = module:get_option_string("otr_policy", "optional");
+
+local mandatory;
+local mandatory_msg = "For security reasons, OTR encryption is required for conversations on this server";
+local optional;
+local optional_msg = "For security reasons, OTR encryption is STRONGLY recommended for conversations on this server";
+
+local messaged = {};
+
+--
+-- Check body message for the presence of the OTR tag.
+local function check_message_otr(event)
+    local body = event.stanza:get_child_text("body");
+	local session = event.origin;
+	local is_otr;
+
+	-- Is this body is an OTR message?
+	if body and body:sub(1,4) ~= "?OTR" then
+		is_otr = 0;
+	else
+		is_otr = 1;
+	end
+
+	-- Force OTR if policy is mandatory.
+	if mandatory and is_otr == 0 then
+		event.origin.send(st.message{ type = "chat", from = module.host, to = event.stanza.attr.from }:tag("body"):text(mandatory_msg));
+		return true;
+	end
+
+	-- Warn if NO otr is detected and if we've NOT warned before the user.
+	if optional and messaged[session.full_jid] == nil and is_otr == 0 then
+        event.origin.send(st.message{ type = "chat", from = module.host, to = event.stanza.attr.from }:tag("body"):text(optional_msg));
+		messaged[session.full_jid] = 1
+    end
+end
+
+-- Module load entry point.
+function module.load()
+	-- Validate policy option.
+	if policy == "mandatory" then
+		mandatory = 1;
+	elseif policy == "optional" then
+		optional = 1;
+	else
+		-- Invalid policy, stop loading module.
+		module:log("error", "Unknown policy %s", policy);
+		return;
+	end
+
+	module:log("info", "OTR policy set to %s", policy);
+end
+
+module:hook("message/bare", check_message_otr, 300);
+module:hook("message/full", check_message_otr, 300);
+module:hook("message/host", check_message_otr, 300);