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

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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>
This commit is contained in:
Mitch Curtis 2013-11-11 14:27:40 +01:00 committed by The Qt Project
parent 105da329a3
commit f1053d94f5
2 changed files with 37 additions and 27 deletions
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62
src/xml/sax/qxml.cpp
View File

@ -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> referencedEntityCounts;
foreach (QString entityName, entities.keys()) {
for (int i = 0; i < value.size() && i != -1; ) {
i = value.indexOf(entityName, i);
if (i != -1) {
// The entityName we're currently trying to find
// was matched in this string; increase our count.
++referencedEntityCounts[entityName];
i += entityName.size();
QMap<QString, int> literalEntitySizes;
// The entity at (QMap<QString,) referenced the entities at (QMap<QString,) (int>) times.
QMap<QString, QMap<QString, int> > referencesToOtherEntities;
QMap<QString, int> expandedSizes;
// For every entity, check how many times all entity names were referenced in its value.
foreach (QString toSearch, entities.keys()) {
// The amount of characters that weren't entity names, but literals, like 'X'.
QString leftOvers = entities.value(toSearch);
// 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()) {
const int timesReferenced = referencedEntityCounts[entityName];
const QString entityValue = entities[entityName];
if (entityValue.size() * timesReferenced > 1024) {
foreach (QString entity, referencesToOtherEntities.keys()) {
expandedSizes[entity] = literalEntitySizes[entity];
foreach (QString referenceTo, referencesToOtherEntities.value(entity).keys()) {
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\""
"expands too a string that is too large to process when "
"referencing \"%2\" %3 times.").arg(entityName).arg(entityName).arg(timesReferenced);
*errorMessage = QString::fromLatin1("The XML entity \"%1\" expands too a string that is too large to process (%2 characters > %3).");
*errorMessage = (*errorMessage).arg(entity).arg(expandedSizes[entity]).arg(entityCharacterLimit);
}
return true;
}
@ -6783,10 +6796,7 @@ bool QXmlSimpleReaderPrivate::parseEntityDecl()
case EValue:
if ( !entityExist(name())) {
QString errorMessage;
if (isPartiallyExpandedEntityValueTooLarge(&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.
if (isExpandedEntityValueTooLarge(&errorMessage)) {
reportParseError(errorMessage);
return false;
}

2
tests/auto/xml/sax/qxmlsimplereader/tst_qxmlsimplereader.cpp
View File

@ -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);
}
}