Windows: Set ACL on debug listener

Signed-off-by: John Howard <jhoward@microsoft.com>

daemon/debugtrap_windows.go

@@ -4,7 +4,9 @@ import (
 	"fmt"
 	"os"
 	"syscall"
+	"unsafe"
 
+	winio "github.com/Microsoft/go-winio"
 	"github.com/Sirupsen/logrus"
 	"github.com/docker/docker/pkg/signal"
 	"github.com/docker/docker/pkg/system"
@@ -13,18 +15,27 @@ import (
 func setupDumpStackTrap(root string) {
 	// Windows does not support signals like *nix systems. So instead of
 	// trapping on SIGUSR1 to dump stacks, we wait on a Win32 event to be
-	// signaled.
+	// signaled. ACL'd to builtin administrators and local system
+	ev := "Global\\docker-daemon-" + fmt.Sprint(os.Getpid())
+	sd, err := winio.SddlToSecurityDescriptor("D:P(A;;GA;;;BA)(A;;GA;;;SY)")
+	if err != nil {
+		logrus.Errorf("failed to get security descriptor for debug stackdump event %s: %s", ev, err.Error())
+		return
+	}
+	var sa syscall.SecurityAttributes
+	sa.Length = uint32(unsafe.Sizeof(sa))
+	sa.InheritHandle = 1
+	sa.SecurityDescriptor = uintptr(unsafe.Pointer(&sd[0]))
+	h, err := system.CreateEvent(&sa, false, false, ev)
+	if h == 0 || err != nil {
+		logrus.Errorf("failed to create debug stackdump event %s: %s", ev, err.Error())
+		return
+	}
 	go func() {
-		sa := syscall.SecurityAttributes{
-			Length: 0,
-		}
-		ev := "Global\\docker-daemon-" + fmt.Sprint(os.Getpid())
-		if h, _ := system.CreateEvent(&sa, false, false, ev); h != 0 {
-			logrus.Debugf("Stackdump - waiting signal at %s", ev)
-			for {
-				syscall.WaitForSingleObject(h, syscall.INFINITE)
-				signal.DumpStacks(root)
-			}
+		logrus.Debugf("Stackdump - waiting signal at %s", ev)
+		for {
+			syscall.WaitForSingleObject(h, syscall.INFINITE)
+			signal.DumpStacks(root)
 		}
 	}()
 }