Fully expand entities to ensure deep or widely nested ones fail parsing

With 46a8885ae4, we failed when parsing
entities whose partially expanded size was greater than 1024
characters. That was not enough, so now we fully expand all entities.

Amends 46a8885ae4.

Change-Id: Ie80720d7e04d825eb4eebf528140eb94806c02b1
Reviewed-by: Richard J. Moore <rich@kde.org>
Reviewed-by: Lars Knoll <lars.knoll@digia.com>

src/xml/sax/qxml.cpp

@@ -426,7 +426,9 @@ private:
 
     // The limit to the amount of times the DTD parsing functions can be called
     // for the DTD currently being parsed.
-    int dtdRecursionLimit;
+    static const int dtdRecursionLimit = 2;
+    // The maximum amount of characters an entity value may contain, after expansion.
+    static const int entityCharacterLimit = 1024;
 
     const QString &string();
     void stringClear();
@@ -497,7 +499,7 @@ private:
     void parseFailed(ParseFunction where, int state);
     void pushParseState(ParseFunction function, int state);
 
-    bool isPartiallyExpandedEntityValueTooLarge(QString *errorMessage);
+    bool isExpandedEntityValueTooLarge(QString *errorMessage);
 
     Q_DECLARE_PUBLIC(QXmlSimpleReader)
     QXmlSimpleReader *q_ptr;
@@ -2763,8 +2765,6 @@ QXmlSimpleReaderPrivate::QXmlSimpleReaderPrivate(QXmlSimpleReader *reader)
     useNamespacePrefixes = false;
     reportWhitespaceCharData = true;
     reportEntities = false;
-
-    dtdRecursionLimit = 2;
 }
 
 QXmlSimpleReaderPrivate::~QXmlSimpleReaderPrivate()
@@ -6657,30 +6657,43 @@ bool QXmlSimpleReaderPrivate::parseChoiceSeq()
     return false;
 }
 
-bool QXmlSimpleReaderPrivate::isPartiallyExpandedEntityValueTooLarge(QString *errorMessage)
+bool QXmlSimpleReaderPrivate::isExpandedEntityValueTooLarge(QString *errorMessage)
 {
-    const QString value = string();
+    QMap<QString, int> literalEntitySizes;
-    QMap<QString, int> referencedEntityCounts;
+    // The entity at (QMap<QString,) referenced the entities at (QMap<QString,) (int>) times.
-    foreach (QString entityName, entities.keys()) {
+    QMap<QString, QMap<QString, int> > referencesToOtherEntities;
-        for (int i = 0; i < value.size() && i != -1; ) {
+    QMap<QString, int> expandedSizes;
-            i = value.indexOf(entityName, i);
+
-            if (i != -1) {
+    // For every entity, check how many times all entity names were referenced in its value.
-                // The entityName we're currently trying to find
+    foreach (QString toSearch, entities.keys()) {
-                // was matched in this string; increase our count.
+        // The amount of characters that weren't entity names, but literals, like 'X'.
-                ++referencedEntityCounts[entityName];
+        QString leftOvers = entities.value(toSearch);
-                i += entityName.size();
+        // How many times was entityName referenced by toSearch?
+        foreach (QString entityName, entities.keys()) {
+            for (int i = 0; i < leftOvers.size() && i != -1; ) {
+                i = leftOvers.indexOf(QString::fromLatin1("&%1;").arg(entityName), i);
+                if (i != -1) {
+                    leftOvers.remove(i, entityName.size() + 2);
+                    // The entityName we're currently trying to find was matched in this string; increase our count.
+                    ++referencesToOtherEntities[toSearch][entityName];
+                }
             }
         }
+        literalEntitySizes[toSearch] = leftOvers.size();
     }
 
-    foreach (QString entityName, referencedEntityCounts.keys()) {
+    foreach (QString entity, referencesToOtherEntities.keys()) {
-        const int timesReferenced = referencedEntityCounts[entityName];
+        expandedSizes[entity] = literalEntitySizes[entity];
-        const QString entityValue = entities[entityName];
+        foreach (QString referenceTo, referencesToOtherEntities.value(entity).keys()) {
-        if (entityValue.size() * timesReferenced > 1024) {
+            const int references = referencesToOtherEntities.value(entity).value(referenceTo);
+            // The total size of an entity's value is the expanded size of all of its referenced entities, plus its literal size.
+            expandedSizes[entity] += expandedSizes[referenceTo] * references + literalEntitySizes[referenceTo] * references;
+        }
+
+        if (expandedSizes[entity] > entityCharacterLimit) {
             if (errorMessage) {
-                *errorMessage = QString::fromLatin1("The XML entity \"%1\""
+                *errorMessage = QString::fromLatin1("The XML entity \"%1\" expands too a string that is too large to process (%2 characters > %3).");
-                    "expands too a string that is too large to process when "
+                *errorMessage = (*errorMessage).arg(entity).arg(expandedSizes[entity]).arg(entityCharacterLimit);
-                    "referencing \"%2\" %3 times.").arg(entityName).arg(entityName).arg(timesReferenced);
             }
             return true;
         }
@@ -6783,10 +6796,7 @@ bool QXmlSimpleReaderPrivate::parseEntityDecl()
             case EValue:
                 if ( !entityExist(name())) {
                     QString errorMessage;
-                    if (isPartiallyExpandedEntityValueTooLarge(&errorMessage)) {
+                    if (isExpandedEntityValueTooLarge(&errorMessage)) {
-                        // The entity at entityName is entityValue.size() characters
-                        // long in its unexpanded form, and was mentioned timesReferenced times,
-                        // resulting in a string that would be greater than 1024 characters.
                         reportParseError(errorMessage);
                         return false;
                     }

tests/auto/xml/sax/qxmlsimplereader/tst_qxmlsimplereader.cpp

@@ -809,7 +809,7 @@ void tst_QXmlSimpleReader::dtdRecursionLimit()
         xmlReader.setDeclHandler(&handler);
         xmlReader.setErrorHandler(&handler);
         QVERIFY(!xmlReader.parse(source));
-        QVERIFY(handler.recursionCount == 1);
+        QCOMPARE(handler.recursionCount, 2);
     }
 }