From 21ca8829a7366d72995adfeb21296d959fbb3777 Mon Sep 17 00:00:00 2001
From: Nick Wellnhofer <wellnhofer@aevum.de>
Date: Sat, 25 Jul 2020 17:57:29 +0200
Subject: [PATCH] Don't try to handle namespaces when building HTML documents

Don't try to resolve namespace in xmlSAX2StartElement when parsing
HTML documents. This useless operation could slow down the parser
considerably.

Found by OSS-Fuzz.
---
 SAX2.c | 76 +++++++++++++++++++++++++++++-----------------------------
 1 file changed, 38 insertions(+), 38 deletions(-)

diff --git a/SAX2.c b/SAX2.c
index 9df01840..4450a3f6 100644
--- a/SAX2.c
+++ b/SAX2.c
@@ -1663,23 +1663,23 @@ xmlSAX2StartElement(void *ctx, const xmlChar *fullname, const xmlChar **atts)
 	}
     }
 
-    /*
-     * Insert all the defaulted attributes from the DTD especially namespaces
-     */
-    if ((!ctxt->html) &&
-	((ctxt->myDoc->intSubset != NULL) ||
-	 (ctxt->myDoc->extSubset != NULL))) {
-	xmlCheckDefaultedAttributes(ctxt, name, prefix, atts);
-    }
+    if (!ctxt->html) {
+        /*
+         * Insert all the defaulted attributes from the DTD especially
+         * namespaces
+         */
+        if ((ctxt->myDoc->intSubset != NULL) ||
+            (ctxt->myDoc->extSubset != NULL)) {
+            xmlCheckDefaultedAttributes(ctxt, name, prefix, atts);
+        }
 
-    /*
-     * process all the attributes whose name start with "xmlns"
-     */
-    if (atts != NULL) {
-        i = 0;
-	att = atts[i++];
-	value = atts[i++];
-	if (!ctxt->html) {
+        /*
+         * process all the attributes whose name start with "xmlns"
+         */
+        if (atts != NULL) {
+            i = 0;
+            att = atts[i++];
+            value = atts[i++];
 	    while ((att != NULL) && (value != NULL)) {
 		if ((att[0] == 'x') && (att[1] == 'm') && (att[2] == 'l') &&
 		    (att[3] == 'n') && (att[4] == 's'))
@@ -1688,30 +1688,30 @@ xmlSAX2StartElement(void *ctx, const xmlChar *fullname, const xmlChar **atts)
 		att = atts[i++];
 		value = atts[i++];
 	    }
-	}
-    }
+        }
 
-    /*
-     * Search the namespace, note that since the attributes have been
-     * processed, the local namespaces are available.
-     */
-    ns = xmlSearchNs(ctxt->myDoc, ret, prefix);
-    if ((ns == NULL) && (parent != NULL))
-	ns = xmlSearchNs(ctxt->myDoc, parent, prefix);
-    if ((prefix != NULL) && (ns == NULL)) {
-	ns = xmlNewNs(ret, NULL, prefix);
-	xmlNsWarnMsg(ctxt, XML_NS_ERR_UNDEFINED_NAMESPACE,
-		     "Namespace prefix %s is not defined\n",
-		     prefix, NULL);
-    }
+        /*
+         * Search the namespace, note that since the attributes have been
+         * processed, the local namespaces are available.
+         */
+        ns = xmlSearchNs(ctxt->myDoc, ret, prefix);
+        if ((ns == NULL) && (parent != NULL))
+            ns = xmlSearchNs(ctxt->myDoc, parent, prefix);
+        if ((prefix != NULL) && (ns == NULL)) {
+            ns = xmlNewNs(ret, NULL, prefix);
+            xmlNsWarnMsg(ctxt, XML_NS_ERR_UNDEFINED_NAMESPACE,
+                         "Namespace prefix %s is not defined\n",
+                         prefix, NULL);
+        }
 
-    /*
-     * set the namespace node, making sure that if the default namespace
-     * is unbound on a parent we simply keep it NULL
-     */
-    if ((ns != NULL) && (ns->href != NULL) &&
-	((ns->href[0] != 0) || (ns->prefix != NULL)))
-	xmlSetNs(ret, ns);
+        /*
+         * set the namespace node, making sure that if the default namespace
+         * is unbound on a parent we simply keep it NULL
+         */
+        if ((ns != NULL) && (ns->href != NULL) &&
+            ((ns->href[0] != 0) || (ns->prefix != NULL)))
+            xmlSetNs(ret, ns);
+    }
 
     /*
      * process all the other attributes