Rework the privilege system completely

See privilege_guide.txt for information

7 files changed, 230 insertions, 89 deletions

diff --git a/advtrains/init.lua b/advtrains/init.lua
index 38252ae..2ef2879 100644
--- a/advtrains/init.lua
+++ b/advtrains/init.lua
@@ -151,6 +151,7 @@ dofile(advtrains.modpath.."/trackplacer.lua")
 dofile(advtrains.modpath.."/tracks.lua")
 dofile(advtrains.modpath.."/atc.lua")
 dofile(advtrains.modpath.."/wagons.lua")
+dofile(advtrains.modpath.."/protection.lua")
 
 dofile(advtrains.modpath.."/trackdb_legacy.lua")
 dofile(advtrains.modpath.."/nodedb.lua")
@@ -272,7 +273,7 @@ advtrains.avt_save = function(remove_players_from_wagons)
 			"last_pos", "last_pos_prev", "movedir", "velocity", "tarvelocity",
 			"trainparts", "savedpos_off_track_index_offset", "recently_collided_with_env",
 			"atc_brake_target", "atc_wait_finish", "atc_command", "atc_delay", "door_open",
-			"text_outside", "text_inside", "couple_lck_front", "couple_lck_back"
+			"text_outside", "text_inside", "couple_lck_front", "couple_lck_back", "line"
 		})
 		--then invalidate
 		if train.index then
diff --git a/advtrains/protection.lua b/advtrains/protection.lua
new file mode 100644
index 0000000..73b725f
--- /dev/null
+++ b/advtrains/protection.lua
@@ -0,0 +1,148 @@
+-- advtrains
+-- protection.lua: privileges and rail protection, and some helpers
+
+
+-- Privileges to control TRAIN DRIVING/COUPLING
+minetest.register_privilege("train_operator", {
+	description = "Without this privilege, a player can't do anything about trains, neither place or remove them nor drive or couple them (but he can build tracks if he has track_builder)",
+	give_to_singleplayer= true,
+});
+
+minetest.register_privilege("train_admin", {
+	description = "Player may drive, place or remove any trains from/to anywhere, regardless of owner, whitelist or protection",
+	give_to_singleplayer= true,
+});
+
+-- Privileges to control TRACK BUILDING
+minetest.register_privilege("track_builder", {
+	description = "Player can place and/or dig rails not protected from him. If he also has protection_bypass, he can place/dig any rails",
+	give_to_singleplayer= true,
+});
+
+-- Privileges to control OPERATING TURNOUTS/SIGNALS
+minetest.register_privilege("railway_operator", {
+	description = "Player can operate turnouts and signals not protected from him. If he also has protection_bypass, he can operate any turnouts/signals",
+	give_to_singleplayer= true,
+});
+
+-- there is a configuration option "allow_build_only_owner". If this is active, a player having track_builder can only build rails and operate signals/turnouts in an area explicitly belonging to him
+-- (checked using a dummy player called "*dummy*" (which is not an allowed player name))
+
+--[[
+Protection/privilege concept:
+Tracks:
+	Protected 1 node all around a rail and 4 nodes upward (maybe make this dynamically determined by the rail...)
+	if track_builder privilege:
+		if not protected from* player:
+			if allow_build_only_owner:
+				if unprotected:
+					deny
+			else:
+				allow
+	deny
+Wagons in general:
+	Players can only place/destroy wagons if they have train_operator
+Wagon driving controls:
+	The former seat_access tables are unnecessary, instead there is a whitelist for the driving stands
+	on player trying to access a driver stand:
+	if is owner or is on whitelist:
+		allow
+	else:
+		deny
+Wagon coupling:
+	Derived from the privileges for driving stands. The whitelist is shared (and also settable on non-driverstand wagons)
+	for each of the two bordering wagons:
+		if is owner or is on whitelist:
+			allow
+
+*"protected from" means the player is not allowed to do things, while "protected by" means that the player is (one of) the owner(s) of this area
+
+]]--
+
+local boo = minetest.settings:get_bool("advtrains_allow_build_to_owner")
+
+
+local nocheck
+-- Check if the node we are about to check is in the range of a track that is protected from a player
+--WARN: true means here that the action is forbidden!
+function advtrains.check_track_protection(pos, pname)
+	if nocheck or pname=="" then
+		return false
+	end
+	nocheck=true --prevent recursive calls, never check this again if we're already in
+	local r, vr = 1, 3
+	local nodes = minetest.find_nodes_in_area(
+		{x = pos.x - r, y = pos.y - vr, z = pos.z - r},
+		{x = pos.x + r, y = pos.y, z = pos.z + r},
+		{"group:advtrains_track"})
+	for _,npos in ipairs(nodes) do
+		if not minetest.check_player_privs(pname, {track_builder = true}) then
+			if boo and not minetest.is_protected(npos, pname) and minetest.is_protected(npos, "*dummy*") then
+				nocheck = false
+				return false
+			else
+				minetest.chat_send_player(pname, "You are not allowed to dig or place nodes near tracks (missing track_builder privilege)")
+				minetest.log("action", pname.." tried to dig/place nodes near the track at "..minetest.pos_to_string(npos).." but does not have track_builder")
+				nocheck = false
+				return true
+			end
+		end
+		if not minetest.check_player_privs(pname, {protection_bypass = true}) then
+			if minetest.is_protected(npos, pname) then
+				nocheck = false
+				minetest.record_protection_violation(pos, pname)
+				return true
+			end
+		end
+	end
+	nocheck=false
+	return false
+end
+
+local old_is_protected = minetest.is_protected
+minetest.is_protected = function(pos, pname)
+	if advtrains.check_track_protection(pos, pname) then
+		return true
+	end
+	return old_is_protected(pos, pname)
+end
+
+--WARN: true means here that the action is allowed!
+function advtrains.check_driving_couple_protection(pname, owner, whitelist)
+	if minetest.check_player_privs(pname, {train_admin = true}) then
+		return true
+	end
+	if not minetest.check_player_privs(pname, {train_operator = true}) then
+		return false
+	end
+	if not owner or owner == pname then
+		return true
+	end
+	if whitelist and string.find(" "..whitelist.." ", " "..pname.." ", nil, true) then
+		return true
+	end
+	return false
+end
+function advtrains.check_turnout_signal_protection(pos, pname)
+	nocheck=true
+	if not minetest.check_player_privs(pname, {railway_operator = true}) then
+		if boo and not minetest.is_protected(pos, pname) and minetest.is_protected(pos, "*dummy*") then
+			nocheck=false
+			return true
+		else
+			minetest.chat_send_player(pname, "You are not allowed to operate turnouts and signals (missing railway_operator privilege)")
+			minetest.log("action", pname.." tried to operate turnout/signal at "..minetest.pos_to_string(pos).." but does not have railway_operator")
+			nocheck=false
+			return false
+		end
+	end
+	if not minetest.check_player_privs(pname, {protection_bypass = true}) then
+		if minetest.is_protected(pos, pname) then
+			minetest.record_protection_violation(pos, pname)
+			nocheck=false
+			return false
+		end
+	end
+	nocheck=false
+	return true
+end
diff --git a/advtrains/settingtypes.txt b/advtrains/settingtypes.txt
index d0c27ec..3b4863d 100644
--- a/advtrains/settingtypes.txt
+++ b/advtrains/settingtypes.txt
@@ -10,3 +10,8 @@ advtrains_enable_debugging (Enable debugging) bool false
 #    Logs are saved in the world directory as advtrains.log
 #    This setting is useful for multiplayer servers
 advtrains_enable_logging (Enable logging) bool false
+#    If this is active, any player can do the following things inside (and only inside) an area that is explicitly protected by him
+#    (checked using a dummy player called "*dummy*" (which is not an allowed player name)):
+#    - build tracks and near tracks without the track_builder privilege
+#    - operate turnouts and signals without the railway_operator privilege
+advtrains_allow_build_to_owner (Allow building/operating to privilegeless area owner) bool false
diff --git a/advtrains/signals.lua b/advtrains/signals.lua
index b01314e..53145f5 100644
--- a/advtrains/signals.lua
+++ b/advtrains/signals.lua
@@ -41,7 +41,7 @@ for r,f in pairs({on={as="off", ls="green", als="red"}, off={as="on", ls="red",
 				end
 			}},
 			on_rightclick=function(pos, node, player)
-				if minetest.check_player_privs(player:get_player_name(), {train_operator=true}) then
+				if advtrains.check_turnout_signal_protection(pos, player:get_player_name()) then
 					advtrains.ndb.swap_node(pos, {name = "advtrains:retrosignal_"..f.as..rotation, param2 = node.param2}, true)
 				end
 			end,
@@ -84,7 +84,7 @@ for r,f in pairs({on={as="off", ls="green", als="red"}, off={as="on", ls="red",
 				end,
 			},
 			on_rightclick=function(pos, node, player)
-				if minetest.check_player_privs(player:get_player_name(), {train_operator=true}) then
+				if advtrains.check_turnout_signal_protection(pos, player:get_player_name()) then
 					advtrains.ndb.swap_node(pos, {name = "advtrains:signal_"..f.as..rotation, param2 = node.param2}, true)
 				end
 			end,
@@ -133,7 +133,7 @@ for r,f in pairs({on={as="off", ls="green", als="red"}, off={as="on", ls="red",
 				end,
 			},
 			on_rightclick=function(pos, node, player)
-				if minetest.check_player_privs(player:get_player_name(), {train_operator=true}) then
+				if advtrains.check_turnout_signal_protection(pos, player:get_player_name()) then
 					advtrains.ndb.swap_node(pos, {name = "advtrains:signal_wall_"..loc.."_"..f.as, param2 = node.param2}, true)
 				end
 			end,
@@ -179,7 +179,7 @@ minetest.register_node("advtrains:across_off", {
 		end,
 	},
 	on_rightclick=function(pos, node, player)
-		if minetest.check_player_privs(player:get_player_name(), {train_operator=true}) then
+		if advtrains.check_turnout_signal_protection(pos, player:get_player_name()) then
 			advtrains.ndb.swap_node(pos, {name = "advtrains:across_on", param2 = node.param2}, true)
 		end
 	end,
@@ -220,7 +220,7 @@ minetest.register_node("advtrains:across_on", {
 		end,
 	},
 	on_rightclick=function(pos, node, player)
-		if minetest.check_player_privs(player:get_player_name(), {train_operator=true}) then
+		if advtrains.check_turnout_signal_protection(pos, player:get_player_name()) then
 			advtrains.ndb.swap_node(pos, {name = "advtrains:across_off", param2 = node.param2}, true)
 		end
 	end,
diff --git a/advtrains/tracks.lua b/advtrains/tracks.lua
index 4b2b17c..f31fef6 100644
--- a/advtrains/tracks.lua
+++ b/advtrains/tracks.lua
@@ -269,6 +269,7 @@ function advtrains.register_tracks(tracktype, def, preset)
 					

 					groups = {

 						attached_node=1,

+						advtrains_track=1,

 						["advtrains_track_"..tracktype]=1,

 						save_in_at_nodedb=1,

 						dig_immediate=2,

@@ -309,7 +310,7 @@ function advtrains.register_tracks(tracktype, def, preset)
 						end

 					end

 					ndef.on_rightclick = function(pos, node, player)

-						if minetest.check_player_privs(player:get_player_name(), {train_operator=true}) then

+						if advtrains.check_turnout_signal_protection(pos, player:get_player_name()) then

 							switchfunc(pos, node)

 							advtrains.log("Switch", player:get_player_name(), pos)

 						end

diff --git a/advtrains/wagons.lua b/advtrains/wagons.lua
index 2dce41b..d9b467c 100644
--- a/advtrains/wagons.lua
+++ b/advtrains/wagons.lua
@@ -1,19 +1,5 @@
 --atan2 counts angles clockwise, minetest does counterclockwise

 

-minetest.register_privilege("train_place", {

-	description = "Player can place trains on tracks not owned by player",

-	give_to_singleplayer= false,

-});

-minetest.register_privilege("train_remove", {

-	description = "Player can remove trains not owned by player",

-	give_to_singleplayer= false,

-});

-minetest.register_privilege("train_operator", {

-	description = "Player may operate trains and switch signals. Given by default. Revoke to prevent players from griefing automated subway systems.",

-	give_to_singleplayer= true,

-	default= true,

-});

-

 local wagon={

 	collisionbox = {-0.5,-0.5,-0.5, 0.5,0.5,0.5},

 	--physical = true,

@@ -161,7 +147,7 @@ function wagon:on_punch(puncher, time_from_last_punch, tool_capabilities, direct
 		if not puncher or not puncher:is_player() then

 			return

 		end

-		if self.owner and puncher:get_player_name()~=self.owner and (not minetest.check_player_privs(puncher, {train_remove = true })) then

+		if self.owner and puncher:get_player_name()~=self.owner and (not minetest.check_player_privs(puncher, {train_admin = true })) then

 		   minetest.chat_send_player(puncher:get_player_name(), attrans("This wagon is owned by @1, you can't destroy it.", self.owner));

 		   return

 		end

@@ -250,8 +236,9 @@ function wagon:on_step(dtime)
 

 		--driver control

 		for seatno, seat in ipairs(self.seats) do

-			local driver=self.seatp[seatno] and minetest.get_player_by_name(self.seatp[seatno])

-			local has_driverstand = self.seatp[seatno] and (minetest.check_player_privs(self.seatp[seatno], {train_operator=true}) or self.owner==self.seatp[seatno])

+			local pname=self.seatp[seatno]

+			local driver=pname and minetest.get_player_by_name(pname)

+			local has_driverstand = pname and advtrains.check_driving_couple_protection(pname, self.owner, self.whitelist)

 			if self.seat_groups then

 				has_driverstand = has_driverstand and (seat.driving_ctrl_access or self.seat_groups[seat.group].driving_ctrl_access)

 			else

@@ -577,13 +564,6 @@ function wagon:on_rightclick(clicker)
 		if not clicker or not clicker:is_player() then

 			return

 		end

-		if clicker:get_player_control().aux1 then

-			--advtrains.dumppath(self:train().path)

-			--minetest.chat_send_all("at index "..(self:train().index or "nil"))

-			--advtrains.invert_train(self.train_id)

-			atprint(dump(self))

-			return

-		end	

 		local pname=clicker:get_player_name()

 		local no=self:get_seatno(pname)

 		if no then

@@ -598,7 +578,7 @@ function wagon:on_rightclick(clicker)
 				if self.has_inventory and self.get_inventory_formspec then

 					poss[#poss+1]={name=attrans("Show Inventory"), key="inv"}

 				end

-				if self.seat_groups[sgr].driving_ctrl_access and minetest.check_player_privs(pname, "train_operator") then

+				if self.seat_groups[sgr].driving_ctrl_access and advtrains.check_driving_couple_protection(pname, self.owner, self.whitelist) then

 					poss[#poss+1]={name=attrans("Bord Computer"), key="bordcom"}

 				end

 				if self.owner==pname then

@@ -779,28 +759,15 @@ function wagon:show_get_on_form(pname)
 	minetest.show_formspec(pname, "advtrains_geton_"..self.unique_id, form)

 end

 function wagon:show_wagon_properties(pname)

-	local numsgr=0

-	if self.seat_groups then

-		numsgr=#self.seat_groups

-	end

-	if not self.seat_access then

-		self.seat_access={}

-	end

 	--[[

-	fields: seat access: empty: everyone

-	checkbox: lock couples

+	fields: 

+	field: driving/couple whitelist

 	button: save

 	]]

-	local form="size[5,"..(numsgr*1.5+4).."]"

-	local at=0

-	if self.seat_groups then

-		for sgr,sgrdef in pairs(self.seat_groups) do

-			local text = attrans("Access to @1",sgrdef.name)

-			form=form.."field[0.5,"..(0.5+at*1.5)..";4,1;sgr_"..sgr..";"..text..";"..(self.seat_access[sgr] or "").."]"

-			at=at+1

-		end

-	end

-	form=form.."button_exit[0.5,"..(at*1.5)..";4,1;save;"..attrans("Save wagon properties").."]"

+	local form="size[5,5]"

+	form = form .. "field[0.5,1;4,1;whitelist;Allow these players to drive your wagon:;"..(self.whitelist or "").."]"

+	--seat groups access lists were here

+	form=form.."button_exit[0.5,3;4,1;save;"..attrans("Save wagon properties").."]"

 	minetest.show_formspec(pname, "advtrains_prop_"..self.unique_id, form)

 end

 

@@ -819,9 +786,9 @@ local function checkcouple(eid)
 	end

 	return le

 end

-local function checklock(pname, own1, own2)

-	return minetest.check_player_privs(pname, "train_remove") or 

-		((not own1 or own1==pname) or (not own2 or own2==pname))

+local function checklock(pname, own1, own2, wl1, wl2)

+	return advtrains.check_driving_couple_protection(pname, own1, wl1)

+		or advtrains.check_driving_couple_protection(pname, own2, wl2)

 end

 function wagon:show_bordcom(pname)

 	if not self:train() then return end

@@ -834,7 +801,7 @@ function wagon:show_bordcom(pname)
 	if train.velocity==0 then

 		form=form.."label[0.5,4.5;Train overview /coupling control:]"

 		linhei=5

-		local pre_own, owns_any = nil, minetest.check_player_privs(pname, "train_remove")

+		local pre_own, pre_wl, owns_any = nil, nil, minetest.check_player_privs(pname, "train_admin")

 		for i, tpid in ipairs(train.trainparts) do

 			local ent = advtrains.wagon_save[tpid]

 			if ent then

@@ -843,7 +810,7 @@ function wagon:show_bordcom(pname)
 				if i~=1 then

 					if not ent.dcpl_lock then

 						form = form .. "image_button["..(i-0.5)..","..(linhei+1)..";1,1;advtrains_discouple.png;dcpl_"..i..";]"

-						if checklock(pname, ent.owner, pre_own) then

+						if checklock(pname, ent.owner, pre_own, ent.whitelist, pre_wl) then

 							form = form .. "image_button["..(i-0.5)..","..(linhei+2)..";1,1;advtrains_cpl_unlock.png;dcpl_lck_"..i..";]"

 						end

 					else

@@ -854,6 +821,7 @@ function wagon:show_bordcom(pname)
 					form = form .. "box["..(i-0.1)..","..(linhei-0.1)..";1,1;green]"

 				end

 				pre_own = ent.owner

+				pre_wl = ent.whitelist

 				owns_any = owns_any or (not ent.owner or ent.owner==pname)

 			end

 		end

@@ -894,7 +862,7 @@ function wagon:show_bordcom(pname)
 end

 function wagon:handle_bordcom_fields(pname, formname, fields)

 	local seatno=self:get_seatno(pname)

-	if not seatno or not self.seat_groups[self.seats[seatno].group].driving_ctrl_access or not minetest.check_player_privs(pname, "train_operator") then

+	if not seatno or not self.seat_groups[self.seats[seatno].group].driving_ctrl_access or not advtrains.check_driving_couple_protection(pname, self.owner, self.whitelist) then

 		return

 	end

 	local train = self:train()

@@ -925,7 +893,7 @@ function wagon:handle_bordcom_fields(pname, formname, fields)
 			local ent = advtrains.wagon_save[tpid]

 			local pent = advtrains.wagon_save[train.trainparts[i-1]]

 			if ent and pent then

-				if checklock(pname, ent.owner, pent.owner) then

+				if checklock(pname, ent.owner, pent.owner, ent.whitelist, pent.whitelist) then

 					for _,wagon in pairs(minetest.luaentities) do

 						if wagon.is_wagon and wagon.initialized and wagon.unique_id==tpid then

 							wagon.dcpl_lock=true

@@ -939,7 +907,7 @@ function wagon:handle_bordcom_fields(pname, formname, fields)
 			local ent = advtrains.wagon_save[tpid]

 			local pent = advtrains.wagon_save[train.trainparts[i-1]]

 			if ent and pent then

-				if checklock(pname, ent.owner, pent.owner) then

+				if checklock(pname, ent.owner, pent.owner, ent.whitelist, pent.whitelist) then

 					for _,wagon in pairs(minetest.luaentities) do

 						if wagon.is_wagon and wagon.initialized and wagon.unique_id==tpid then

 							wagon.dcpl_lock=false

@@ -962,11 +930,11 @@ function wagon:handle_bordcom_fields(pname, formname, fields)
 	end

 	

 	local function chkownsany()

-		local owns_any = minetest.check_player_privs(pname, "train_remove")

+		local owns_any = minetest.check_player_privs(pname, "train_admin")

 		for i, tpid in ipairs(train.trainparts) do

 			local ent = advtrains.wagon_save[tpid]

 			if ent then

-				owns_any = owns_any or (not ent.owner or ent.owner==pname)

+				owns_any = owns_any or advtrains.check_driving_couple_protection(pname, ent.owner, ent.whitelist)

 			end

 		end

 		return owns_any

@@ -1031,14 +999,13 @@ minetest.register_on_player_receive_fields(function(player, formname, fields)
 			for _,wagon in pairs(minetest.luaentities) do

 				if wagon.is_wagon and wagon.initialized and wagon.unique_id==uid then

 					local pname=player:get_player_name()

-					if pname~=wagon.owner then

+					if pname~=wagon.owner and not minetest.check_player_privs(pname, {train_admin = true}) then

 						return true

 					end

 					if fields.save or not fields.quit then

 						for sgr,sgrdef in pairs(wagon.seat_groups) do

-							if fields["sgr_"..sgr] then

-								local fcont = fields["sgr_"..sgr]

-								wagon.seat_access[sgr] = fcont~="" and fcont or nil

+							if fields.whitelist then

+								wagon.whitelist = fields.whitelist

 							end

 						end

 					end

@@ -1073,7 +1040,7 @@ function wagon:seating_from_key_helper(pname, fields, no)
 	if fields.prop and self.owner==pname then

 		self:show_wagon_properties(pname)

 	end

-	if fields.bordcom and self.seat_groups[sgr].driving_ctrl_access and minetest.check_player_privs(pname, "train_operator") then

+	if fields.bordcom and self.seat_groups[sgr].driving_ctrl_access and advtrains.check_driving_couple_protection(pname, self.owner, self.whitelist) then

 		self:show_bordcom(pname)

 	end

 	if fields.dcwarn then

@@ -1084,25 +1051,13 @@ function wagon:seating_from_key_helper(pname, fields, no)
 	end

 end

 function wagon:check_seat_group_access(pname, sgr)

-	if self.seat_groups[sgr].driving_ctrl_access and not (minetest.check_player_privs(pname, "train_operator") or self.owner==pname) then

-		return false, "Missing train_operator privilege."

+	if self.seat_groups[sgr].driving_ctrl_access and not (advtrains.check_driving_couple_protection(pname, self.owner, self.whitelist)) then

+		return false, "Not allowed to access a driver stand!"

 	end

 	if self.seat_groups[sgr].driving_ctrl_access then

 		advtrains.log("Drive", pname, self.object:getpos(), self:train().text_outside)

 	end

-	if not self.seat_access then

-		return true

-	end

-	local sae=self.seat_access[sgr]

-	if not sae or sae=="" then

-		return true

-	end

-	for name in string.gmatch(sae, "%S+") do

-		if name==pname then

-			return true

-		end

-	end

-	return false, "Blacklisted by owner."

+	return true

 end

 function wagon:reattach_all()

 	if not self.seatp then self.seatp={} end

@@ -1158,9 +1113,12 @@ function advtrains.register_wagon(sysname_p, prototype, desc, inv_img)
 					atprint("no track here, not placing.")

 					return itemstack

 				end

-				if not minetest.check_player_privs(placer, {train_place = true }) and minetest.is_protected(pointed_thing.under, placer:get_player_name()) then

-					minetest.record_protection_violation(pointed_thing.under, placer:get_player_name())

-					return

+				if not minetest.check_player_privs(placer, {train_operator = true }) then

+					minetest.chat_send_player(placer:get_player_name(), "You don't have the train_operator privilege.")

+					return itemstack

+				end

+				if not minetest.check_player_privs(placer, {train_admin = true }) and minetest.is_protected(pointed_thing.under, placer:get_player_name()) then

+					return itemstack

 				end

 				local tconns=advtrains.get_track_connections(node.name, node.param2)

 				local yaw = placer:get_look_horizontal() + (math.pi/2)

@@ -1191,9 +1149,4 @@ function advtrains.register_wagon(sysname_p, prototype, desc, inv_img)
 	})

 end

 

---[[

-	wagons can define update_animation(self, velocity) if they have a speed-dependent animation

-	this function will be called when the velocity vector changes or every 2 seconds.

-]]

-

 

diff --git a/privilege_guide.txt b/privilege_guide.txt
new file mode 100644
index 0000000..7c4952f
--- /dev/null
+++ b/privilege_guide.txt
@@ -0,0 +1,33 @@
+
+### Advtrains Privilege Guide
+All privileges are automatically granted to singleplayer, but for
+multiplayer servers this might be interesting.
+There are 3 groups of privileges introduced by advtrains:
+
+## Trains
+For a player to build his own trains and driving them, the player needs
+the 'train_operator' privilege. This privilege no longer allows him to
+control any train, only the ones that he owns or that he is whitelisted on.
+The owner of a wagon can write a whitelist which players are allowed to
+operate his wagon using the wagon properties dialog.
+Players having the 'train_admin' privilege can always drive, build and
+destroy any train.
+
+## Tracks*
+The area 1 node around and 4 nodes up from each track node is protected.
+Players that don't have the 'track_builder' privilege can not build or
+dig (or modify) anything inside this area.
+If any player tries to modify anything that is in the area of a track
+node and this track node is protected from him, he also can not do this.
+(that said, while checking protection, the area around a track is
+treated as the track node itself)
+
+## Turnouts and Signals*
+Players without the 'railway_operator' privilege can not operate signals
+and turnouts.
+
+* If the configuration option 'advtrains_allow_build_to_owner' is set,
+an exception applies to players missing the required privileges when
+they are in a protected area that they have access to. Whether the
+area is protected from others is checked by checking for protection
+against a dummy player called '*dummy*'