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net.server_epoll: Call :shutdown() on TLS sockets when supported Comment from Matthew: This fixes a potential issue where the Prosody process gets blocked on sockets waiting for them to close. Unlike non-TLS sockets, closing a TLS socket sends layer 7 data, and this can cause problems for sockets which are in the process of being cleaned up. This depends on LuaSec changes which are not yet upstream. From Martijn's original email: So first my analysis of luasec. in ssl.c the socket is put into blocking mode right before calling SSL_shutdown() inside meth_destroy(). My best guess to why this is is because meth_destroy is linked to the __close and __gc methods, which can't exactly be called multiple times and luasec does want to make sure that a tls session is shutdown as clean as possible. I can't say I disagree with this reasoning and don't want to change this behaviour. My solution to this without changing the current behaviour is to introduce a shutdown() method. I am aware that this overlaps in a conflicting way with tcp's shutdown method, but it stays close to the OpenSSL name. This method calls SSL_shutdown() in the current (non)blocking mode of the underlying socket and returns a boolean whether or not the shutdown is completed (matching SSL_shutdown()'s 0 or 1 return values), and returns the familiar ssl_ioerror() strings on error with a false for completion. This error can then be used to determine if we have wantread/wantwrite to finalize things. Once meth_shutdown() has been called once a shutdown flag will be set, which indicates to meth_destroy() that the SSL_shutdown() has been handled by the application and it shouldn't be needed to set the socket to blocking mode. I've left the SSL_shutdown() call in the LSEC_STATE_CONNECTED to prevent TOCTOU if the application reaches a timeout for the shutdown code, which might allow SSL_shutdown() to clean up anyway at the last possible moment. Another thing I've changed to luasec is the call to socket_setblocking() right before calling close(2) in socket_destroy() in usocket.c. According to the latest POSIX[0]: Note that the requirement for close() on a socket to block for up to the current linger interval is not conditional on the O_NONBLOCK setting. Which I read to mean that removing O_NONBLOCK on the socket before close doesn't impact the behaviour and only causes noise in system call tracers. I didn't touch the windows bits of this, since I don't do windows. For the prosody side of things I've made the TLS shutdown bits resemble interface:onwritable(), and put it under a combined guard of self._tls and self.conn.shutdown. The self._tls bit is there to prevent getting stuck on this condition, and self.conn.shutdown is there to prevent the code being called by instances where the patched luasec isn't deployed. The destroy() method can be called from various places and is read by me as the "we give up" error path. To accommodate for these unexpected entrypoints I've added a single call to self.conn:shutdown() to prevent the socket being put into blocking mode. I have no expectations that there is any other use here. Same as previous, the self.conn.shutdown check is there to make sure it's not called on unpatched luasec deployments and self._tls is there to make sure we don't call shutdown() on tcp sockets. I wouldn't recommend logging of the conn:shutdown() error inside close(), since a lot of clients simply close the connection before SSL_shutdown() is done.

-- Prosody IM
-- Copyright (C) 2012 Florian Zeitz
-- Copyright (C) 2019 Kim Alvefur
--
-- This project is MIT/X11 licensed. Please see the
-- COPYING file in the source package for more information.
--

local encodings = require "prosody.util.encodings";
assert(encodings.confusable, "This module requires that Prosody be built with ICU");
local skeleton = encodings.confusable.skeleton;

local usage = require "prosody.util.prosodyctl".show_usage;
local usermanager = require "prosody.core.usermanager";
local storagemanager = require "prosody.core.storagemanager";

local skeletons
function module.load()
	if module.host ~= "*" then
		skeletons = module:open_store("skeletons");
	end
end

module:hook("user-registered", function(user)
	local skel = skeleton(user.username);
	local ok, err = skeletons:set(skel, { username = user.username });
	if not ok then
		module:log("error", "Unable to store mimicry data (%q => %q): %s", user.username, skel, err);
	end
end);

module:hook_global("user-deleted", function(user)
	if user.host ~= module.host then return end
	local skel = skeleton(user.username);
	local ok, err = skeletons:set(skel, nil);
	if not ok and err then
		module:log("error", "Unable to clear mimicry data (%q): %s", skel, err);
	end
end);

module:hook("user-registering", function(user)
	local existing, err = skeletons:get(skeleton(user.username));
	if existing then
		module:log("debug", "Attempt to register username '%s' which could be confused with '%s'", user.username, existing.username);
		user.allowed = false;
	elseif err then
		module:log("error", "Unable to check if new username '%s' can be confused with any existing user: %s", err);
	end
end);

function module.command(arg)
	if (arg[1] ~= "bootstrap" or not arg[2]) then
		usage("mod_mimicking bootstrap <host>", "Initialize username mimicry database");
		return;
	end

	local host = arg[2];

	local host_session = prosody.hosts[host];
	if not host_session then
		return "No such host";
	end

	storagemanager.initialize_host(host);
	usermanager.initialize_host(host);

	skeletons = storagemanager.open(host, "skeletons");

	local count = 0;
	for user in usermanager.users(host) do
		local skel = skeleton(user);
		local existing, err = skeletons:get(skel);
		if existing and existing.username ~= user then
			module:log("warn", "Existing usernames '%s' and '%s' are confusable", existing.username, user);
		elseif err then
			module:log("error", "Error checking for existing mimicry data (%q = %q): %s", user, skel, err);
		end
		local ok, err = skeletons:set(skel, { username = user });
		if ok then
			count = count + 1;
		elseif err then
			module:log("error", "Unable to store mimicry data (%q => %q): %s", user, skel, err);
		end
	end
	module:log("info", "%d usernames indexed", count);
end