Merge pull request #20 from newsoft/master

Fix integer overflow in MallocFrameBuffer()

libvncclient/rfbproto.c

@@ -1829,7 +1829,8 @@ HandleRFBServerMessage(rfbClient* client)
 	client->updateRect.x = client->updateRect.y = 0;
 	client->updateRect.w = client->width;
 	client->updateRect.h = client->height;
-	client->MallocFrameBuffer(client);
+  if (!client->MallocFrameBuffer(client))
+    return FALSE;
 	SendFramebufferUpdateRequest(client, 0, 0, rect.r.w, rect.r.h, FALSE);
 	rfbClientLog("Got new framebuffer size: %dx%d\n", rect.r.w, rect.r.h);
 	continue;
@@ -2290,7 +2291,9 @@ HandleRFBServerMessage(rfbClient* client)
     client->updateRect.x = client->updateRect.y = 0;
     client->updateRect.w = client->width;
     client->updateRect.h = client->height;
-    client->MallocFrameBuffer(client);
+    if (!client->MallocFrameBuffer(client))
+      return FALSE;
+
     SendFramebufferUpdateRequest(client, 0, 0, client->width, client->height, FALSE);
     rfbClientLog("Got new framebuffer size: %dx%d\n", client->width, client->height);
     break;
@@ -2306,7 +2309,8 @@ HandleRFBServerMessage(rfbClient* client)
     client->updateRect.x = client->updateRect.y = 0;
     client->updateRect.w = client->width;
     client->updateRect.h = client->height;
-    client->MallocFrameBuffer(client);
+    if (!client->MallocFrameBuffer(client))
+      return FALSE;
     SendFramebufferUpdateRequest(client, 0, 0, client->width, client->height, FALSE);
     rfbClientLog("Got new framebuffer size: %dx%d\n", client->width, client->height);
     break;

libvncclient/vncviewer.c

@@ -82,9 +82,27 @@ static char* ReadPassword(rfbClient* client) {
 #endif
 }
 static rfbBool MallocFrameBuffer(rfbClient* client) {
+uint64_t allocSize;
+
   if(client->frameBuffer)
     free(client->frameBuffer);
-  client->frameBuffer=malloc(client->width*client->height*client->format.bitsPerPixel/8);
+
+  /* SECURITY: promote 'width' into uint64_t so that the multiplication does not overflow
+     'width' and 'height' are 16-bit integers per RFB protocol design
+     SIZE_MAX is the maximum value that can fit into size_t
+  */
+  allocSize = (uint64_t)client->width * client->height * client->format.bitsPerPixel/8;
+
+  if (allocSize >= SIZE_MAX) {
+    rfbClientErr("CRITICAL: cannot allocate frameBuffer, requested size is too large\n");
+    return FALSE;
+  }
+
+  client->frameBuffer=malloc( (size_t)allocSize );
+
+  if (client->frameBuffer == NULL)
+    rfbClientErr("CRITICAL: frameBuffer allocation failed, requested size too large or not enough memory?\n");
+
   return client->frameBuffer?TRUE:FALSE;
 }
 
@@ -232,7 +250,8 @@ static rfbBool rfbInitConnection(rfbClient* client)
 
   client->width=client->si.framebufferWidth;
   client->height=client->si.framebufferHeight;
-  client->MallocFrameBuffer(client);
+  if (!client->MallocFrameBuffer(client))
+    return FALSE;
 
   if (!SetFormatAndEncodings(client))
     return FALSE;