crypto/tls: test that Clone copies session ticket key fields

Updates #25256

Change-Id: If16c42581f1cf3500fd7fd01c915e487f8025e55
Reviewed-on: https://go-review.googlesource.com/c/go/+/235922
Run-TryBot: Katie Hockman <katie@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Filippo Valsorda <filippo@golang.org>

tls_test.go

@@ -785,11 +785,6 @@ func TestCloneNonFuncFields(t *testing.T) {
 	typ := v.Type()
 	for i := 0; i < typ.NumField(); i++ {
 		f := v.Field(i)
-		if !f.CanSet() {
-			// unexported field; not cloned.
-			continue
-		}
-
 		// testing/quick can't handle functions or interfaces and so
 		// isn't used here.
 		switch fn := typ.Field(i).Name; fn {
@@ -830,17 +825,17 @@ func TestCloneNonFuncFields(t *testing.T) {
 			f.Set(reflect.ValueOf([]CurveID{CurveP256}))
 		case "Renegotiation":
 			f.Set(reflect.ValueOf(RenegotiateOnceAsClient))
+		case "mutex", "autoSessionTicketKeys", "sessionTicketKeys":
+			continue // these are unexported fields that are handled separately
 		default:
 			t.Errorf("all fields must be accounted for, but saw unknown field %q", fn)
 		}
 	}
+	// Set the unexported fields related to session ticket keys, which are copied with Clone().
+	c1.autoSessionTicketKeys = []ticketKey{c1.ticketKeyFromBytes(c1.SessionTicketKey)}
+	c1.sessionTicketKeys = []ticketKey{c1.ticketKeyFromBytes(c1.SessionTicketKey)}
 
 	c2 := c1.Clone()
-	// DeepEqual also compares unexported fields, thus c2 needs to have run
-	// serverInit in order to be DeepEqual to c1. Cloning it and discarding
-	// the result is sufficient.
-	c2.Clone()
-
 	if !reflect.DeepEqual(&c1, c2) {
 		t.Errorf("clone failed to copy a field")
 	}