client/sandbox.lua: Add a safe subset of the standard library to the sandbox environment

client/sandbox.lua

@@ -11,7 +11,37 @@ for _, name in ipairs(buildat_safe_list) do
 	buildat_safe[name] = buildat[name]
 end
 
-local sandbox = {}
+local sandbox = {
+	-- Base sandbox from
+	-- http://stackoverflow.com/questions/1224708/how-can-i-create-a-secure-lua-sandbox/6982080#6982080
+	ipairs = ipairs,
+	next = next,
+	pairs = pairs,
+	pcall = pcall,
+	tonumber = tonumber,
+	tostring = tostring,
+	type = type,
+	unpack = unpack,
+	coroutine = { create = coroutine.create, resume = coroutine.resume,
+		running = coroutine.running, status = coroutine.status,
+		wrap = coroutine.wrap },
+	string = { byte = string.byte, char = string.char, find = string.find,
+		format = string.format, gmatch = string.gmatch, gsub = string.gsub,
+		len = string.len, lower = string.lower, match = string.match,
+		rep = string.rep, reverse = string.reverse, sub = string.sub,
+		upper = string.upper },
+	table = { insert = table.insert, maxn = table.maxn, remove = table.remove,
+		sort = table.sort },
+	math = { abs = math.abs, acos = math.acos, asin = math.asin,
+		atan = math.atan, atan2 = math.atan2, ceil = math.ceil, cos = math.cos,
+		cosh = math.cosh, deg = math.deg, exp = math.exp, floor = math.floor,
+		fmod = math.fmod, frexp = math.frexp, huge = math.huge,
+		ldexp = math.ldexp, log = math.log, log10 = math.log10, max = math.max,
+		min = math.min, modf = math.modf, pi = math.pi, pow = math.pow,
+		rad = math.rad, random = math.random, sin = math.sin, sinh = math.sinh,
+		sqrt = math.sqrt, tan = math.tan, tanh = math.tanh },
+	os = { clock = os.clock, difftime = os.difftime, time = os.time },
+}
 
 sandbox.buildat = buildat