Fix buffer overflow in ModifiablePixelBuffer::fillRect.

It can be triggered by RRE message with subrectangle out of framebuffer
boundaries. It may prevent the same kind of issue caused by evil message
from another encoding too.

1 files changed, 15 insertions, 4 deletions

diff --git a/common/rfb/PixelBuffer.cxx b/common/rfb/PixelBuffer.cxx
index 89addabc..7f3df6cb 100644
--- a/common/rfb/PixelBuffer.cxx
+++ b/common/rfb/PixelBuffer.cxx
@@ -101,15 +101,26 @@ void ModifiablePixelBuffer::fillRect(const Rect& r, const void* pix)
   int stride;
   U8 *buf;
   int w, h, b;
+  Rect drect;
 
-  w = r.width();
-  h = r.height();
+  drect = r;
+  if (!drect.enclosed_by(getRect())) {
+    vlog.error("Destination rect %dx%d at %d,%d exceeds framebuffer %dx%d",
+               drect.width(), drect.height(), drect.tl.x, drect.tl.y, width_, height_);
+    drect = drect.intersect(getRect());
+  }
+
+  if (drect.is_empty())
+    return;
+
+  w = drect.width();
+  h = drect.height();
   b = format.bpp/8;
 
   if (h == 0)
     return;
 
-  buf = getBufferRW(r, &stride);
+  buf = getBufferRW(drect, &stride);
 
   if (b == 1) {
     while (h--) {
@@ -136,7 +147,7 @@ void ModifiablePixelBuffer::fillRect(const Rect& r, const void* pix)
     }
   }
 
-  commitBufferRW(r);
+  commitBufferRW(drect);
 }
 
 void ModifiablePixelBuffer::imageRect(const Rect& r,