1From 0adcb34c49bee5b19bd29b16a578c510c23597ea Mon Sep 17 00:00:00 2001 2From: Sebastian Pipping <sebastian@pipping.org> 3Date: Mon, 27 Dec 2021 20:15:02 +0100 4Subject: [PATCH] lib: Detect and prevent troublesome left shifts in function 5 storeAtts (CVE-2021-45960) 6 7--- 8 lib/xmlparse.c | 31 +++++++++++++++++++++++++++++-- 9 1 file changed, 29 insertions(+), 2 deletions(-) 10 11diff --git a/lib/xmlparse.c b/lib/xmlparse.c 12index d730f41..b47c31b 100644 13--- a/lib/xmlparse.c 14+++ b/lib/xmlparse.c 15@@ -3414,7 +3414,13 @@ storeAtts(XML_Parser parser, const ENCODING *enc, const char *attStr, 16 if (nPrefixes) { 17 int j; /* hash table index */ 18 unsigned long version = parser->m_nsAttsVersion; 19- int nsAttsSize = (int)1 << parser->m_nsAttsPower; 20+ 21+ /* Detect and prevent invalid shift */ 22+ if (parser->m_nsAttsPower >= sizeof(unsigned int) * 8 /* bits per byte */) { 23+ return XML_ERROR_NO_MEMORY; 24+ } 25+ 26+ unsigned int nsAttsSize = 1u << parser->m_nsAttsPower; 27 unsigned char oldNsAttsPower = parser->m_nsAttsPower; 28 /* size of hash table must be at least 2 * (# of prefixed attributes) */ 29 if ((nPrefixes << 1) 30@@ -3425,7 +3431,28 @@ storeAtts(XML_Parser parser, const ENCODING *enc, const char *attStr, 31 ; 32 if (parser->m_nsAttsPower < 3) 33 parser->m_nsAttsPower = 3; 34- nsAttsSize = (int)1 << parser->m_nsAttsPower; 35+ 36+ /* Detect and prevent invalid shift */ 37+ if (parser->m_nsAttsPower >= sizeof(nsAttsSize) * 8 /* bits per byte */) { 38+ /* Restore actual size of memory in m_nsAtts */ 39+ parser->m_nsAttsPower = oldNsAttsPower; 40+ return XML_ERROR_NO_MEMORY; 41+ } 42+ 43+ nsAttsSize = 1u << parser->m_nsAttsPower; 44+ 45+ /* Detect and prevent integer overflow. 46+ * The preprocessor guard addresses the "always false" warning 47+ * from -Wtype-limits on platforms where 48+ * sizeof(unsigned int) < sizeof(size_t), e.g. on x86_64. */ 49+#if UINT_MAX >= SIZE_MAX 50+ if (nsAttsSize > (size_t)(-1) / sizeof(NS_ATT)) { 51+ /* Restore actual size of memory in m_nsAtts */ 52+ parser->m_nsAttsPower = oldNsAttsPower; 53+ return XML_ERROR_NO_MEMORY; 54+ } 55+#endif 56+ 57 temp = (NS_ATT *)REALLOC(parser, parser->m_nsAtts, 58 nsAttsSize * sizeof(NS_ATT)); 59 if (! temp) { 60-- 611.8.3.1 62 63