From ede41d1e186ed2aba88a06e84cac839b770af3a1 Mon Sep 17 00:00:00 2001

From: Sebastian Pipping <sebastian@pipping.org>

Date: Wed, 26 Jan 2022 02:36:43 +0100

Subject: [PATCH 1/2] lib: Prevent integer overflow in doProlog

 (CVE-2022-23990)

The change from "int nameLen" to "size_t nameLen"

addresses the overflow on "nameLen++" in code

"for (; name[nameLen++];)" right above the second

change in the patch.

---

 expat/lib/xmlparse.c | 10 ++++++++--

 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/lib/xmlparse.c b/lib/xmlparse.c

index 5ce31402..d1d17005 100644

--- a/lib/xmlparse.c

+++ b/lib/xmlparse.c

@@ -5372,7 +5372,7 @@ doProlog(XML_Parser parser, const ENCODING *enc, const char *s, const char *end,

       if (dtd->in_eldecl) {

         ELEMENT_TYPE *el;

         const XML_Char *name;

-        int nameLen;

+        size_t nameLen;

         const char *nxt

             = (quant == XML_CQUANT_NONE ? next : next - enc->minBytesPerChar);

         int myindex = nextScaffoldPart(parser);

@@ -5388,7 +5388,13 @@ doProlog(XML_Parser parser, const ENCODING *enc, const char *s, const char *end,

         nameLen = 0;

         for (; name[nameLen++];)

           ;

-        dtd->contentStringLen += nameLen;

+

+        /* Detect and prevent integer overflow */

+        if (nameLen > UINT_MAX - dtd->contentStringLen) {

+          return XML_ERROR_NO_MEMORY;

+        }

+

+        dtd->contentStringLen += (unsigned)nameLen;

         if (parser->m_elementDeclHandler)

           handleDefault = XML_FALSE;

       }