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From 0adcb34c49bee5b19bd29b16a578c510c23597ea Mon Sep 17 00:00:00 2001
From: Sebastian Pipping <sebastian@pipping.org>
Date: Mon, 27 Dec 2021 20:15:02 +0100
Subject: [PATCH] lib: Detect and prevent troublesome left shifts in function
storeAtts (CVE-2021-45960)
Upstream-Status: Backport:
https://github.com/libexpat/libexpat/pull/534/commits/0adcb34c49bee5b19bd29b16a578c510c23597ea
CVE: CVE-2021-45960
Signed-off-by: Steve Sakoman <steve@sakoman.com>
---
expat/lib/xmlparse.c | 31 +++++++++++++++++++++++++++++--
1 file changed, 29 insertions(+), 2 deletions(-)
diff --git a/expat/lib/xmlparse.c b/expat/lib/xmlparse.c
index d730f41c3..b47c31b05 100644
--- a/lib/xmlparse.c
+++ b/lib/xmlparse.c
@@ -3414,7 +3414,13 @@ storeAtts(XML_Parser parser, const ENCODING *enc, const char *attStr,
if (nPrefixes) {
int j; /* hash table index */
unsigned long version = parser->m_nsAttsVersion;
- int nsAttsSize = (int)1 << parser->m_nsAttsPower;
+
+ /* Detect and prevent invalid shift */
+ if (parser->m_nsAttsPower >= sizeof(unsigned int) * 8 /* bits per byte */) {
+ return XML_ERROR_NO_MEMORY;
+ }
+
+ unsigned int nsAttsSize = 1u << parser->m_nsAttsPower;
unsigned char oldNsAttsPower = parser->m_nsAttsPower;
/* size of hash table must be at least 2 * (# of prefixed attributes) */
if ((nPrefixes << 1)
@@ -3425,7 +3431,28 @@ storeAtts(XML_Parser parser, const ENCODING *enc, const char *attStr,
;
if (parser->m_nsAttsPower < 3)
parser->m_nsAttsPower = 3;
- nsAttsSize = (int)1 << parser->m_nsAttsPower;
+
+ /* Detect and prevent invalid shift */
+ if (parser->m_nsAttsPower >= sizeof(nsAttsSize) * 8 /* bits per byte */) {
+ /* Restore actual size of memory in m_nsAtts */
+ parser->m_nsAttsPower = oldNsAttsPower;
+ return XML_ERROR_NO_MEMORY;
+ }
+
+ nsAttsSize = 1u << parser->m_nsAttsPower;
+
+ /* Detect and prevent integer overflow.
+ * The preprocessor guard addresses the "always false" warning
+ * from -Wtype-limits on platforms where
+ * sizeof(unsigned int) < sizeof(size_t), e.g. on x86_64. */
+#if UINT_MAX >= SIZE_MAX
+ if (nsAttsSize > (size_t)(-1) / sizeof(NS_ATT)) {
+ /* Restore actual size of memory in m_nsAtts */
+ parser->m_nsAttsPower = oldNsAttsPower;
+ return XML_ERROR_NO_MEMORY;
+ }
+#endif
+
temp = (NS_ATT *)REALLOC(parser, parser->m_nsAtts,
nsAttsSize * sizeof(NS_ATT));
if (! temp) {
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