Bound the Windows clipboard read by the block size instead of scanning for a NUL

client/vnc/server/input_windows_clipboard_test.go

@@ -0,0 +1,19 @@
+//go:build windows
+
+package server
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+// Clipboard text is set by whichever local process owns the clipboard, and
+// nothing makes it end in a NUL. Decoding must stop at the block's end, not
+// run on looking for a terminator.
+func TestUTF16UpToNUL(t *testing.T) {
+	assert.Equal(t, "hi", utf16UpToNUL([]uint16{'h', 'i', 0, 'x'}), "stops at the first NUL")
+	assert.Equal(t, "hi", utf16UpToNUL([]uint16{'h', 'i'}), "an unterminated block decodes to its end and no further")
+	assert.Equal(t, "", utf16UpToNUL([]uint16{0, 'x'}), "a leading NUL is an empty string")
+	assert.Equal(t, "", utf16UpToNUL(nil))
+}