use a random number from /dev/urandom (nbase.get_random_uint wrapper)

nse_main.lua

@@ -95,12 +95,7 @@ local open = io.open;
 
 local math = require "math";
 local max = math.max;
-
--- Due to heap randomization (on most Operating Systems), we can use a
--- Lua function address as a good seed for the C srand function. If there
--- is no heap randomization, it's still a decently random integer; that is,
--- it's no better or worse than os.time().
-math.randomseed(tonumber(tostring(function() end):match("function: (0x%x+)")));
+local randomseed = math.randomseed;
 
 local package = require "package";
 
@@ -129,6 +124,11 @@ do -- Append the nselib directory to the Lua search path
   package.path = path.."?.lua;"..package.path;
 end
 
+-- Set the math.randomseed value in nse_main.lua on behalf of scripts.
+-- Since Lua uses the C rand and srand functions, which have a static
+-- seed for the entire program, we don't want scripts doing this themselves.
+math.randomseed(nmap.get_random_uint());
+
 local script_database_type, script_database_path =
     cnse.fetchfile_absolute(cnse.script_dbpath);
 local script_database_update = cnse.scriptupdatedb;