Add a (rudimentary) password manager.

builtin/mainmenu/pwmgr.lua

@@ -0,0 +1,127 @@
+--
+-- Minetest password manager
+--
+-- © Copyright 2019 by luk3yx.
+--
+-- This program is free software; you can redistribute it and/or modify
+-- it under the terms of the GNU Lesser General Public License as published by
+-- the Free Software Foundation; either version 2.1 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 Lesser General Public License for more details.
+--
+-- You should have received a copy of the GNU Lesser 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.
+--
+
+pwmgr = {}
+
+local db = Settings(core.get_modpath() .. DIR_DELIM .. '..' .. DIR_DELIM ..
+	".saved_passwords")
+
+-- Convert to/from the weird .conf-safe format
+local function conf_escape(text)
+	local res = tostring(text):gsub("[^A-Za-z0-9]", function(char)
+		return "_" .. string.byte(char) .. "_"
+	end)
+	return res
+end
+
+local function conf_unescape(text)
+	local res = text:gsub("_[0-9]+_", function(esc)
+		return string.char(tonumber(esc:sub(2, #esc - 1))) or esc
+	end)
+	return res
+end
+
+-- Get a config entry name
+local function get_conf_entry(data)
+	data = data or gamedata
+	return "pwmgr.plaintext"
+		.. "." .. conf_escape(data.address)
+		.. "." .. conf_escape(data.port)
+		.. "." .. conf_escape(data.playername or data.name)
+end
+
+-- Get and set passwords
+function pwmgr.get_password(data)
+	local pw = db:get(get_conf_entry(data))
+	if type(pw) ~= "string" or pw == "" then
+		return
+	else
+		return conf_unescape(pw)
+	end
+end
+
+function pwmgr.set_password(data, new_pw)
+	if not new_pw then
+		if type(data) == "table" then
+			new_pw = data.password
+		else
+			new_pw = data
+		end
+		new_pw = data or gamedata.password
+		data   = false
+	end
+	db:set(get_conf_entry(data), conf_escape(new_pw))
+	db:write()
+end
+
+-- Get the "Should this password be saved?" formspec
+local function get_prejoin_formspec()
+	local msg = "Should this password be saved (in plaintext)?\n"
+		.. "\nAddress: "  .. gamedata.address
+		.. "\nPort: "     .. gamedata.port
+		.. "\nName: "     .. gamedata.playername
+		.. "\nPassword: " .. string.rep("*", #gamedata.password)
+
+	local formspec = "size[10,5,true]" ..
+		"label[0.5,0.5;Password manager]" ..
+		"label[0.5,1;" .. core.formspec_escape(msg) .. "]" ..
+		"button[1,4;2,1;pwd_cancel;< Cancel]" ..
+		"button[4,4;2,1;pwd_no_save;Don't save]" ..
+		"button[7,4;2,1;pwd_save;Save >]"
+
+	return formspec
+end
+
+local function get_prejoin_buttonhandler(this, fields)
+	if fields.pwd_cancel then
+		this:delete()
+		return true
+	end
+
+	if fields.pwd_save then
+		pwmgr.set_password()
+	end
+
+	if fields.pwd_save or fields.pwd_no_save then
+		this:delete()
+		core.start()
+		return true
+	end
+
+	return false
+end
+
+function pwmgr.prejoin(this)
+	if not gamedata.password or gamedata.password == "" then
+		gamedata.password = pwmgr.get_password()
+		if not gamedata.password or gamedata.password == "" then
+			return true
+		end
+	elseif this then
+		local dlg = dialog_create("pwmgr_save_password",
+					get_prejoin_formspec,
+					get_prejoin_buttonhandler,
+					nil)
+		dlg:set_parent(this)
+		this:hide()
+		dlg:show()
+		return true
+	end
+end

builtin/mainmenu/tab_online.lua

@@ -331,6 +331,13 @@ local function main_button_handler(tabview, fields, name, tabdata)
 		core.settings:set("address",     fields.te_address)
 		core.settings:set("remote_port", fields.te_port)
 
+		if core.settings:get_bool("pwmgr.enable") then
+			if not rawget(_G, "pwmgr") then
+				dofile(core.get_mainmenu_path() .. DIR_DELIM .. "pwmgr.lua")
+			end
+			if pwmgr.prejoin(tabview) then return true end
+		end
+
 		core.start()
 		return true
 	end

builtin/settingtypes.txt

@@ -722,6 +722,10 @@ client_mapblock_limit (Mapblock limit) int 5000
 #    Whether to show the client debug info (has the same effect as hitting F5).
 show_debug (Show debug info) bool false
 
+#    Enable the (beta) password manager. Note that this stores passwords in
+#    plaintext, only use it if you know what you are doing!
+pwmgr.enable (Enable INSECURE beta password manager) bool false
+
 [Server / Singleplayer]
 
 #    Name of the server, to be displayed when players join and in the serverlist.