lua/sandbox: print non-printable characters in hex, text elide

daemon/lua/sandbox.lua

@@ -151,18 +151,31 @@ function table_print (tt, indent, done)
 	done = done or {}
 	indent = indent or 0
 	result = ""
+	-- Convert to printable string (escape unprintable)
+	local function printable(value)
+		value = tostring(value)
+		local bytes = {}
+		for i = 1, #value do
+			local c = string.byte(value, i)
+			if c >= 0x20 and c < 0x7f then table.insert(bytes, string.char(c))
+			else                           table.insert(bytes, '\\'..tostring(c))
+			end
+			if i > 50 then table.insert(bytes, '...') break end
+		end
+		return table.concat(bytes)
+	end
 	if type(tt) == "table" then
 		for key, value in pairs (tt) do
 			result = result .. string.rep (" ", indent)
 			if type (value) == "table" and not done [value] then
 				done [value] = true
-				result = result .. string.format("[%s] => {\n", tostring (key))
+				result = result .. string.format("[%s] => {\n", printable (key))
 				result = result .. table_print (value, indent + 4, done)
 				result = result .. string.rep (" ", indent)
 				result = result .. "}\n"
 			else
 				result = result .. string.format("[%s] => %s\n",
-				         tostring (key), tostring(value))
+				         tostring (key), printable(value))
 			end
 		end
 	else