From ed73ac2aa776875f218cb0fd09f68be79a8f5191 Mon Sep 17 00:00:00 2001
From: Pierre Ossman <ossman@cendio.se>
Date: Wed, 2 Oct 2019 16:06:08 +0200
Subject: [PATCH] Handle pixel formats with odd shift values

Our fast paths assume that each channel fits in to a separate byte.
That means the shift needs to be a multiple of 8. Start actually
checking this so that a client cannot trip us up and possibly cause
incorrect code exection.

Issue found by Pavel Cheremushkin from Kaspersky Lab.
---
 common/rfb/PixelFormat.cxx | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/common/rfb/PixelFormat.cxx b/common/rfb/PixelFormat.cxx
index 52e267a..185d437 100644
--- a/common/rfb/PixelFormat.cxx
+++ b/common/rfb/PixelFormat.cxx
@@ -205,6 +205,12 @@ bool PixelFormat::is888(void) const
     return false;
   if (blueMax != 255)
     return false;
+  if ((redShift & 0x7) != 0)
+    return false;
+  if ((greenShift & 0x7) != 0)
+    return false;
+  if ((blueShift & 0x7) != 0)
+    return false;
 
   return true;
 }