chore: import upstream snapshot with attribution

luaplugin/sandbox.go

@@ -0,0 +1,50 @@
+package luaplugin
+
+import lua "github.com/yuin/gopher-lua"
+
+// Sandbox applies the plugin sandbox to L. It is exported for tools that load
+// plugin files outside the runtime (e.g. pluginmgr metadata extraction) and
+// must apply the same stdlib restrictions before executing untrusted code.
+func Sandbox(L *lua.LState) { sandbox(L) }
+
+// sandbox removes dangerous Lua standard library functions from the VM,
+// leaving only safe operations available to plugins. It also adds
+// compatibility helpers missing from Lua 5.1 (e.g. utf8.char).
+func sandbox(L *lua.LState) {
+	// Remove top-level functions that can load/execute arbitrary code.
+	for _, name := range []string{"dofile", "loadfile", "load", "loadstring", "require", "module"} {
+		L.SetGlobal(name, lua.LNil)
+	}
+	L.SetGlobal("package", lua.LNil)
+	L.SetGlobal("debug", lua.LNil)
+
+	// Remove the io module entirely (replaced by cliamp.fs).
+	L.SetGlobal("io", lua.LNil)
+
+	// Restrict the os module to a safe subset: time, date, clock, getenv.
+	if os := L.GetGlobal("os"); os != lua.LNil {
+		if tbl, ok := os.(*lua.LTable); ok {
+			for _, fn := range []string{"execute", "remove", "rename", "exit", "setlocale", "tmpname"} {
+				tbl.RawSetString(fn, lua.LNil)
+			}
+		}
+	}
+
+	// Provide utf8.char() for Lua 5.1 compatibility (GopherLua is 5.1).
+	// Plugins need this for Braille character rendering in visualizers.
+	utf8Tbl := L.NewTable()
+	L.SetField(utf8Tbl, "char", L.NewFunction(luaUTF8Char))
+	L.SetGlobal("utf8", utf8Tbl)
+}
+
+// luaUTF8Char converts one or more integer codepoints to a UTF-8 string.
+// Equivalent to Lua 5.3's utf8.char().
+func luaUTF8Char(L *lua.LState) int {
+	n := L.GetTop()
+	buf := make([]rune, n)
+	for i := 1; i <= n; i++ {
+		buf[i-1] = rune(L.CheckInt(i))
+	}
+	L.Push(lua.LString(string(buf)))
+	return 1
+}