From 79d8dc08eb98842173ce239b9dd60df0e9e9ae72 Mon Sep 17 00:00:00 2001
From: Alan Coopersmith <alan.coopersmith@oracle.com>
Date: Fri, 8 Mar 2013 22:25:35 -0800
Subject: [PATCH] integer overflow in XGetWindowProperty() [CVE-2013-1981
 10/13]

If the reported number of properties is too large, the calculations
to allocate memory for them may overflow, leaving us returning less
memory to the caller than implied by the value written to *nitems.

Reported-by: Ilja Van Sprundel <ivansprundel@ioactive.com>
Signed-off-by: Alan Coopersmith <alan.coopersmith@oracle.com>
Reviewed-by: Matthieu Herrb <matthieu.herrb@laas.fr>
---
 src/GetProp.c | 25 ++++++++++++++++---------
 1 file changed, 16 insertions(+), 9 deletions(-)

diff --git a/src/GetProp.c b/src/GetProp.c
index 5d6e0b8c..ae14edcf 100644
--- a/src/GetProp.c
+++ b/src/GetProp.c
@@ -28,6 +28,7 @@ in this Software without prior written authorization from The Open Group.
 #include <config.h>
 #endif
 #include "Xlibint.h"
+#include <limits.h>
 
 int
 XGetWindowProperty(
@@ -66,8 +67,17 @@ XGetWindowProperty(
 
     *prop = (unsigned char *) NULL;
     if (reply.propertyType != None) {
-	long nbytes, netbytes;
-	switch (reply.format) {
+	unsigned long nbytes, netbytes;
+	int format = reply.format;
+
+      /*
+       * Protect against both integer overflow and just plain oversized
+       * memory allocation - no server should ever return this many props.
+       */
+	if (reply.nItems >= (INT_MAX >> 4))
+	    format = -1;	/* fall through to default error case */
+
+	switch (format) {
       /*
        * One extra byte is malloced than is needed to contain the property
        * data, but this last byte is null terminated and convenient for
@@ -76,24 +86,21 @@ XGetWindowProperty(
        */
 	  case 8:
 	    nbytes = netbytes = reply.nItems;
-	    if (nbytes + 1 > 0 &&
-		(*prop = (unsigned char *) Xmalloc ((unsigned)nbytes + 1)))
+	    if (nbytes + 1 > 0 && (*prop = Xmalloc (nbytes + 1)))
 		_XReadPad (dpy, (char *) *prop, netbytes);
 	    break;
 
 	  case 16:
 	    nbytes = reply.nItems * sizeof (short);
 	    netbytes = reply.nItems << 1;
-	    if (nbytes + 1 > 0 &&
-		(*prop = (unsigned char *) Xmalloc ((unsigned)nbytes + 1)))
+	    if (nbytes + 1 > 0 && (*prop = Xmalloc (nbytes + 1)))
 		_XRead16Pad (dpy, (short *) *prop, netbytes);
 	    break;
 
 	  case 32:
 	    nbytes = reply.nItems * sizeof (long);
 	    netbytes = reply.nItems << 2;
-	    if (nbytes + 1 > 0 &&
-		(*prop = (unsigned char *) Xmalloc ((unsigned)nbytes + 1)))
+	    if (nbytes + 1 > 0 && (*prop = Xmalloc (nbytes + 1)))
 		_XRead32 (dpy, (long *) *prop, netbytes);
 	    break;
 
@@ -115,7 +122,7 @@ XGetWindowProperty(
 	    break;
 	}
 	if (! *prop) {
-	    _XEatData(dpy, (unsigned long) netbytes);
+	    _XEatDataWords(dpy, reply.length);
 	    UnlockDisplay(dpy);
 	    SyncHandle();
 	    return(BadAlloc);	/* not Success */