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From 08ab2774b870de1c7b5a48693df75e8154addae5 Mon Sep 17 00:00:00 2001
From: Nick Wellnhofer <wellnhofer@aevum.de>
Date: Thu, 12 Jan 2017 15:39:52 +0100
Subject: [PATCH] Check for integer overflow in xsltAddTextString
Limit buffer size in xsltAddTextString to INT_MAX. The issue can be
exploited to trigger an out of bounds write on 64-bit systems.
Originally reported to Chromium:
https://crbug.com/676623
---
libxslt/transform.c | 25 ++++++++++++++++++++++---
libxslt/xsltInternals.h | 4 ++--
2 files changed, 24 insertions(+), 5 deletions(-)
diff --git a/libxslt/transform.c b/libxslt/transform.c
index 519133fc..02bff34a 100644
--- a/libxslt/transform.c
+++ b/libxslt/transform.c
@@ -813,13 +813,32 @@ xsltAddTextString(xsltTransformContextPtr ctxt, xmlNodePtr target,
return(target);
if (ctxt->lasttext == target->content) {
+ int minSize;
- if (ctxt->lasttuse + len >= ctxt->lasttsize) {
+ /* Check for integer overflow accounting for NUL terminator. */
+ if (len >= INT_MAX - ctxt->lasttuse) {
+ xsltTransformError(ctxt, NULL, target,
+ "xsltCopyText: text allocation failed\n");
+ return(NULL);
+ }
+ minSize = ctxt->lasttuse + len + 1;
+
+ if (ctxt->lasttsize < minSize) {
xmlChar *newbuf;
int size;
+ int extra;
+
+ /* Double buffer size but increase by at least 100 bytes. */
+ extra = minSize < 100 ? 100 : minSize;
+
+ /* Check for integer overflow. */
+ if (extra > INT_MAX - ctxt->lasttsize) {
+ size = INT_MAX;
+ }
+ else {
+ size = ctxt->lasttsize + extra;
+ }
- size = ctxt->lasttsize + len + 100;
- size *= 2;
newbuf = (xmlChar *) xmlRealloc(target->content,size);
if (newbuf == NULL) {
xsltTransformError(ctxt, NULL, target,
diff --git a/libxslt/xsltInternals.h b/libxslt/xsltInternals.h
index 060b1783..5ad17719 100644
--- a/libxslt/xsltInternals.h
+++ b/libxslt/xsltInternals.h
@@ -1754,8 +1754,8 @@ struct _xsltTransformContext {
* Speed optimization when coalescing text nodes
*/
const xmlChar *lasttext; /* last text node content */
- unsigned int lasttsize; /* last text node size */
- unsigned int lasttuse; /* last text node use */
+ int lasttsize; /* last text node size */
+ int lasttuse; /* last text node use */
/*
* Per Context Debugging
*/
--
2.11.0
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