Expose lua os.clock() api (redis#12971)

Implement redis#12699

This PR exposing Lua os.clock() api for getting the elapsed time of Lua
code execution.

Using:
```lua
local start = os.clock()
...
do something
...
local elpased = os.clock() - start
```

---------

Co-authored-by: Meir Shpilraien (Spielrein) <[email protected]>
Co-authored-by: Madelyn Olson <[email protected]>

deps/lua/src/loslib.c

@@ -234,10 +234,17 @@ static const luaL_Reg syslib[] = {
 
 /* }====================================================== */
 
+#define UNUSED(V) ((void) V)
 
+/* Only a subset is loaded currently, for sandboxing concerns. */
+static const luaL_Reg sandbox_syslib[] = {
+  {"clock",     os_clock},
+  {NULL, NULL}
+};
 
 LUALIB_API int luaopen_os (lua_State *L) {
-  luaL_register(L, LUA_OSLIBNAME, syslib);
+  UNUSED(syslib);
+  luaL_register(L, LUA_OSLIBNAME, sandbox_syslib);
   return 1;
 }
 

src/script_lua.c

@@ -51,6 +51,7 @@ static char *libraries_allow_list[] = {
     "math",
     "table",
     "struct",
+    "os",
     NULL,
 };
 
@@ -1232,14 +1233,14 @@ static void luaLoadLibraries(lua_State *lua) {
     luaLoadLib(lua, LUA_STRLIBNAME, luaopen_string);
     luaLoadLib(lua, LUA_MATHLIBNAME, luaopen_math);
     luaLoadLib(lua, LUA_DBLIBNAME, luaopen_debug);
+    luaLoadLib(lua, LUA_OSLIBNAME, luaopen_os);
     luaLoadLib(lua, "cjson", luaopen_cjson);
     luaLoadLib(lua, "struct", luaopen_struct);
     luaLoadLib(lua, "cmsgpack", luaopen_cmsgpack);
     luaLoadLib(lua, "bit", luaopen_bit);
 
 #if 0 /* Stuff that we don't load currently, for sandboxing concerns. */
     luaLoadLib(lua, LUA_LOADLIBNAME, luaopen_package);
-    luaLoadLib(lua, LUA_OSLIBNAME, luaopen_os);
 #endif
 }
 

tests/unit/scripting.tcl

@@ -620,6 +620,52 @@ start_server {tags {"scripting"}} {
              [run_script {return redis.sha1hex('Pizza & Mandolino')} 0]
     } {da39a3ee5e6b4b0d3255bfef95601890afd80709 74822d82031af7493c20eefa13bd07ec4fada82f}
 
+    test "Measures elapsed time os.clock()" {
+        set escaped [run_script {
+            local start = os.clock()
+            while os.clock() - start < 1 do end
+            return {double = os.clock() - start}
+        } 0]
+        assert_morethan_equal $escaped 1 ;# 1 second
+    }
+
+    test "Prohibit dangerous lua methods in sandbox" {
+        assert_equal "" [run_script {
+            local allowed_methods = {"clock"}
+            -- Find a value from a tuple and return the position.
+            local indexOf = function(tuple, value)
+                for i, v in ipairs(tuple) do
+                    if v == value then return i end
+                end
+                return nil
+            end
+            -- Check for disallowed methods and verify all allowed methods exist.
+            -- If an allowed method is found, it's removed from 'allowed_methods'.
+            -- If 'allowed_methods' is empty at the end, all allowed methods were found.
+            for key, value in pairs(os) do
+                local index = indexOf(allowed_methods, key)
+                if index == nil or type(value) ~= "function" then
+                    return "Disallowed "..type(value)..":"..key
+                end
+                table.remove(allowed_methods, index)
+            end
+            if #allowed_methods ~= 0 then
+                return "Expected method not found: "..table.concat(allowed_methods, ",")
+            end
+            return ""
+        } 0]
+    }
+
+    test "Verify execution of prohibit dangerous Lua methods will fail" {
+        assert_error {ERR *attempt to call field 'execute'*} {run_script {os.execute()} 0}
+        assert_error {ERR *attempt to call field 'exit'*} {run_script {os.exit()} 0}
+        assert_error {ERR *attempt to call field 'getenv'*} {run_script {os.getenv()} 0}
+        assert_error {ERR *attempt to call field 'remove'*} {run_script {os.remove()} 0}
+        assert_error {ERR *attempt to call field 'rename'*} {run_script {os.rename()} 0}
+        assert_error {ERR *attempt to call field 'setlocale'*} {run_script {os.setlocale()} 0}
+        assert_error {ERR *attempt to call field 'tmpname'*} {run_script {os.tmpname()} 0}
+    }
+
     test {Globals protection reading an undeclared global variable} {
         catch {run_script {return a} 0} e
         set e