QXmlStreamReader: make fastScanName() indicate parsing status to callers

Origin: upstream, commits
 https://code.qt.io/cgit/qt/qtbase.git/commit/?id=1a423ce4372d18a7
 https://code.qt.io/cgit/qt/qtbase.git/commit/?id=6326bec46a618c72
 https://code.qt.io/cgit/qt/qtbase.git/commit/?id=bdc8dc51380d2ce4
 https://code.qt.io/cgit/qt/qtbase.git/commit/?id=3bc3b8d69a291aa5
 .
 Based on KDE's backport:
 https://invent.kde.org/qt/qt/qtbase/-/merge_requests/263
Last-Update: 2023-07-15

This fixes a crash while parsing an XML file with garbage data, the file
starts with '<' then garbage data:
- The loop in the parse() keeps iterating until it hits "case 262:",
  which calls fastScanName()
- fastScanName() iterates over the text buffer scanning for the
  attribute name (e.g. "xml:lang"), until it finds ':'
- Consider a Value val, fastScanName() is called on it, it would set
  val.prefix to a number > val.len, then it would hit the 4096 condition
  and return (returned 0, now it returns the equivalent of
  std::null_opt), which means that val.len doesn't get modified, making
  it smaller than val.prefix
- The code would try constructing an XmlStringRef with negative length,
  which would hit an assert in one of QStringView's constructors

Add an assert to the XmlStringRef constructor.

Add unittest based on the file from the bug report.

Credit to OSS-Fuzz.

Gbp-Pq: Name CVE-2023-37369.diff

diff --git a/src/corelib/serialization/qxmlstream.cpp b/src/corelib/serialization/qxmlstream.cpp
index 0ac5548178792bbd429f40c0a2edf9807c9942df..15972b8c53cf7fc522e9063f0fd785477ec0352b 100644 (file)
--- a/src/corelib/serialization/qxmlstream.cpp
+++ b/src/corelib/serialization/qxmlstream.cpp
@@ -1302,15 +1302,18 @@ inline int QXmlStreamReaderPrivate::fastScanContentCharList()
     return n;
 }
 
-inline int QXmlStreamReaderPrivate::fastScanName(int *prefix)
+// Fast scan an XML attribute name (e.g. "xml:lang").
+inline QXmlStreamReaderPrivate::FastScanNameResult
+QXmlStreamReaderPrivate::fastScanName(Value *val)
 {
     int n = 0;
     uint c;
     while ((c = getChar()) != StreamEOF) {
         if (n >= 4096) {
             // This is too long to be a sensible name, and
-            // can exhaust memory
-            return 0;
+            // can exhaust memory, or the range of decltype(*prefix)
+            raiseNamePrefixTooLongError();
+            return {};
         }
         switch (c) {
         case '\n':
@@ -1339,23 +1342,23 @@ inline int QXmlStreamReaderPrivate::fastScanName(int *prefix)
         case '+':
         case '*':
             putChar(c);
-            if (prefix && *prefix == n+1) {
-                *prefix = 0;
+            if (val && val->prefix == n + 1) {
+                val->prefix = 0;
                 putChar(':');
                 --n;
             }
-            return n;
+            return FastScanNameResult(n);
         case ':':
-            if (prefix) {
-                if (*prefix == 0) {
-                    *prefix = n+2;
+            if (val) {
+                if (val->prefix == 0) {
+                    val->prefix = n + 2;
                 } else { // only one colon allowed according to the namespace spec.
                     putChar(c);
-                    return n;
+                    return FastScanNameResult(n);
                 }
             } else {
                 putChar(c);
-                return n;
+                return FastScanNameResult(n);
             }
             Q_FALLTHROUGH();
         default:
@@ -1364,12 +1367,12 @@ inline int QXmlStreamReaderPrivate::fastScanName(int *prefix)
         }
     }
 
-    if (prefix)
-        *prefix = 0;
+    if (val)
+        val->prefix = 0;
     int pos = textBuffer.size() - n;
     putString(textBuffer, pos);
     textBuffer.resize(pos);
-    return 0;
+    return FastScanNameResult(0);
 }
 
 enum NameChar { NameBeginning, NameNotBeginning, NotName };
@@ -1878,6 +1881,14 @@ void QXmlStreamReaderPrivate::raiseWellFormedError(const QString &message)
     raiseError(QXmlStreamReader::NotWellFormedError, message);
 }
 
+void QXmlStreamReaderPrivate::raiseNamePrefixTooLongError()
+{
+    // TODO: add a ImplementationLimitsExceededError and use it instead
+    raiseError(QXmlStreamReader::NotWellFormedError,
+               QXmlStream::tr("Length of XML attribute name exceeds implementation limits (4KiB "
+                              "characters)."));
+}
+
 void QXmlStreamReaderPrivate::parseError()
 {
 

diff --git a/src/corelib/serialization/qxmlstream.g b/src/corelib/serialization/qxmlstream.g
index 4321fed68a479f012a2961077402a144c6ac2057..8c6a1a58870658cff48263fb46330885fd0ed3db 100644 (file)
--- a/src/corelib/serialization/qxmlstream.g
+++ b/src/corelib/serialization/qxmlstream.g
@@ -516,7 +516,16 @@ public:
     int fastScanLiteralContent();
     int fastScanSpace();
     int fastScanContentCharList();
-    int fastScanName(int *prefix = nullptr);
+
+    struct FastScanNameResult {
+        FastScanNameResult() : ok(false) {}
+        explicit FastScanNameResult(int len) : addToLen(len), ok(true) { }
+        operator bool() { return ok; }
+        int operator*() { Q_ASSERT(ok); return addToLen; }
+        int addToLen;
+        bool ok;
+    };
+    FastScanNameResult fastScanName(Value *val = nullptr);
     inline int fastScanNMTOKEN();
 
 
@@ -525,6 +534,7 @@ public:
 
     void raiseError(QXmlStreamReader::Error error, const QString& message = QString());
     void raiseWellFormedError(const QString &message);
+    void raiseNamePrefixTooLongError();
 
     QXmlStreamEntityResolver *entityResolver;
 
@@ -1811,7 +1821,12 @@ space_opt ::= space;
 qname ::= LETTER;
 /.
         case $rule_number: {
-            sym(1).len += fastScanName(&sym(1).prefix);
+            Value &val = sym(1);
+            if (auto res = fastScanName(&val))
+                val.len += *res;
+            else
+                return false;
+
             if (atEnd) {
                 resume($rule_number);
                 return false;
@@ -1822,7 +1837,11 @@ qname ::= LETTER;
 name ::= LETTER;
 /.
         case $rule_number:
-            sym(1).len += fastScanName();
+            if (auto res = fastScanName())
+                sym(1).len += *res;
+            else
+                return false;
+
             if (atEnd) {
                 resume($rule_number);
                 return false;

diff --git a/src/corelib/serialization/qxmlstream_p.h b/src/corelib/serialization/qxmlstream_p.h
index e5bde7b98e6ded3e43699c3b1fc61c426f749c38..b01484cac3c67d79627e200218f6a3ea5df67c5e 100644 (file)
--- a/src/corelib/serialization/qxmlstream_p.h
+++ b/src/corelib/serialization/qxmlstream_p.h
@@ -1005,7 +1005,16 @@ public:
     int fastScanLiteralContent();
     int fastScanSpace();
     int fastScanContentCharList();
-    int fastScanName(int *prefix = nullptr);
+
+    struct FastScanNameResult {
+        FastScanNameResult() : ok(false) {}
+        explicit FastScanNameResult(int len) : addToLen(len), ok(true) { }
+        operator bool() { return ok; }
+        int operator*() { Q_ASSERT(ok); return addToLen; }
+        int addToLen;
+        bool ok;
+    };
+    FastScanNameResult fastScanName(Value *val = nullptr);
     inline int fastScanNMTOKEN();
 
 
@@ -1014,6 +1023,7 @@ public:
 
     void raiseError(QXmlStreamReader::Error error, const QString& message = QString());
     void raiseWellFormedError(const QString &message);
+    void raiseNamePrefixTooLongError();
 
     QXmlStreamEntityResolver *entityResolver;
 
@@ -1939,7 +1949,12 @@ bool QXmlStreamReaderPrivate::parse()
         break;
 
         case 262: {
-            sym(1).len += fastScanName(&sym(1).prefix);
+            Value &val = sym(1);
+            if (auto res = fastScanName(&val))
+                val.len += *res;
+            else
+                return false;
+
             if (atEnd) {
                 resume(262);
                 return false;
@@ -1947,7 +1962,11 @@ bool QXmlStreamReaderPrivate::parse()
         } break;
 
         case 263:
-            sym(1).len += fastScanName();
+            if (auto res = fastScanName())
+                sym(1).len += *res;
+            else
+                return false;
+
             if (atEnd) {
                 resume(263);
                 return false;

diff --git a/tests/auto/corelib/serialization/qxmlstream/tst_qxmlstream.cpp b/tests/auto/corelib/serialization/qxmlstream/tst_qxmlstream.cpp
index a2349a58462bb8a6373c724871bde5a722e309db..9150abe65bff84806de709d5f4af96de0f9c704a 100644 (file)
--- a/tests/auto/corelib/serialization/qxmlstream/tst_qxmlstream.cpp
+++ b/tests/auto/corelib/serialization/qxmlstream/tst_qxmlstream.cpp
@@ -42,6 +42,7 @@
 
 #include "qc14n.h"
 
+Q_DECLARE_METATYPE(QXmlStreamReader::Error)
 Q_DECLARE_METATYPE(QXmlStreamReader::ReadElementTextBehaviour)
 
 static const char *const catalogFile = "XML-Test-Suite/xmlconf/finalCatalog.xml";
@@ -587,6 +588,8 @@ private slots:
     void readBack() const;
     void roundTrip() const;
     void roundTrip_data() const;
+    void test_fastScanName_data() const;
+    void test_fastScanName() const;
 
     void entityExpansionLimit() const;
 
@@ -1843,5 +1846,42 @@ void tst_QXmlStream::roundTrip() const
     QCOMPARE(out, in);
 }
 
+void tst_QXmlStream::test_fastScanName_data() const
+{
+    QTest::addColumn<QByteArray>("data");
+    QTest::addColumn<QXmlStreamReader::Error>("errorType");
+
+    // 4096 is the limit in QXmlStreamReaderPrivate::fastScanName()
+
+    QByteArray arr = "<a:" + QByteArray("b").repeated(4096 - 1);
+    QTest::newRow("data1") << arr << QXmlStreamReader::PrematureEndOfDocumentError;
+
+    arr = "<a:" + QByteArray("b").repeated(4096);
+    QTest::newRow("data2") << arr << QXmlStreamReader::NotWellFormedError;
+
+    arr = "<" + QByteArray("a").repeated(4000) + ":" + QByteArray("b").repeated(96);
+    QTest::newRow("data3") << arr << QXmlStreamReader::PrematureEndOfDocumentError;
+
+    arr = "<" + QByteArray("a").repeated(4000) + ":" + QByteArray("b").repeated(96 + 1);
+    QTest::newRow("data4") << arr << QXmlStreamReader::NotWellFormedError;
+
+    arr = "<" + QByteArray("a").repeated(4000 + 1) + ":" + QByteArray("b").repeated(96);
+    QTest::newRow("data5") << arr << QXmlStreamReader::NotWellFormedError;
+}
+
+void tst_QXmlStream::test_fastScanName() const
+{
+    QFETCH(QByteArray, data);
+    QFETCH(QXmlStreamReader::Error, errorType);
+
+    QXmlStreamReader reader(data);
+    QXmlStreamReader::TokenType tokenType;
+    while (!reader.atEnd())
+        tokenType = reader.readNext();
+
+    QCOMPARE(tokenType, QXmlStreamReader::Invalid);
+    QCOMPARE(reader.error(), errorType);
+}
+
 #include "tst_qxmlstream.moc"
 // vim: et:ts=4:sw=4:sts=4