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From c8061284095abebebbcd6fea7167477aef44a00c Mon Sep 17 00:00:00 2001
From: Jonas Karlsson <jonas.karlsson@qt.io>
Date: Thu, 8 Feb 2024 17:01:05 +0100
Subject: [PATCH] Improve KTX file reading memory safety
* Use qAddOverflow/qSubOverflow methods for catching additions and
subtractions with overflow and handle these scenarios when reading the
file.
* Add 'safeView' method that checks that the byte array view constructed
is not out of bounds.
* Return error if number of levels is higher than what is reasonable.
* Return error if number of faces is incorrect.
* Add unit test with invalid KTX file previously causing a segmentation
fault.
This fixes CVE-2024-25580.
Fixes: QTBUG-121918
Pick-to: 6.7 6.6 6.5 6.2 5.15
Change-Id: Ie0824c32a5921de30cf07c1fc1b49a084e6d07b2
Reviewed-by: Eirik Aavitsland <eirik.aavitsland@qt.io>
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
(cherry picked from commit 28ecb523ce8490bff38b251b3df703c72e057519)
---
src/gui/util/qktxhandler.cpp | 138 +++++++++++++++++++++++++++--------
src/gui/util/qktxhandler_p.h | 2 +-
2 files changed, 110 insertions(+), 30 deletions(-)
diff --git a/src/gui/util/qktxhandler.cpp b/src/gui/util/qktxhandler.cpp
index 7eda4c46fb..2853e46c3d 100644
--- a/src/gui/util/qktxhandler.cpp
+++ b/src/gui/util/qktxhandler.cpp
@@ -73,7 +73,7 @@ struct KTXHeader {
quint32 bytesOfKeyValueData;
};
-static const quint32 headerSize = sizeof(KTXHeader);
+static constexpr quint32 qktxh_headerSize = sizeof(KTXHeader);
// Currently unused, declared for future reference
struct KTXKeyValuePairItem {
@@ -103,11 +103,36 @@ struct KTXMipmapLevel {
*/
};
-bool QKtxHandler::canRead(const QByteArray &suffix, const QByteArray &block)
+static bool qAddOverflow(quint32 v1, quint32 v2, quint32 *r) {
+ // unsigned additions are well-defined
+ *r = v1 + v2;
+ return v1 > quint32(v1 + v2);
+}
+
+// Returns the nearest multiple of 4 greater than or equal to 'value'
+static bool nearestMultipleOf4(quint32 value, quint32 *result)
+{
+ constexpr quint32 rounding = 4;
+ *result = 0;
+ if (qAddOverflow(value, rounding - 1, result))
+ return true;
+ *result &= ~(rounding - 1);
+ return false;
+}
+
+// Returns a slice with prechecked bounds
+static QByteArray safeSlice(const QByteArray& array, quint32 start, quint32 length)
{
- Q_UNUSED(suffix)
+ quint32 end = 0;
+ if (qAddOverflow(start, length, &end) || end > quint32(array.length()))
+ return {};
+ return QByteArray(array.data() + start, length);
+}
- return (qstrncmp(block.constData(), ktxIdentifier, KTX_IDENTIFIER_LENGTH) == 0);
+bool QKtxHandler::canRead(const QByteArray &suffix, const QByteArray &block)
+{
+ Q_UNUSED(suffix);
+ return block.startsWith(QByteArray::fromRawData(ktxIdentifier, KTX_IDENTIFIER_LENGTH));
}
QTextureFileData QKtxHandler::read()
@@ -115,42 +140,97 @@ QTextureFileData QKtxHandler::read()
if (!device())
return QTextureFileData();
- QByteArray buf = device()->readAll();
- const quint32 dataSize = quint32(buf.size());
- if (dataSize < headerSize || !canRead(QByteArray(), buf)) {
- qCDebug(lcQtGuiTextureIO, "Invalid KTX file %s", logName().constData());
+ const QByteArray buf = device()->readAll();
+ if (size_t(buf.size()) > std::numeric_limits<quint32>::max()) {
+ qWarning(lcQtGuiTextureIO, "Too big KTX file %s", logName().constData());
+ return QTextureFileData();
+ }
+
+ if (!canRead(QByteArray(), buf)) {
+ qWarning(lcQtGuiTextureIO, "Invalid KTX file %s", logName().constData());
+ return QTextureFileData();
+ }
+
+ if (buf.size() < qsizetype(qktxh_headerSize)) {
+ qWarning(lcQtGuiTextureIO, "Invalid KTX header size in %s", logName().constData());
return QTextureFileData();
}
- const KTXHeader *header = reinterpret_cast<const KTXHeader *>(buf.constData());
- if (!checkHeader(*header)) {
- qCDebug(lcQtGuiTextureIO, "Unsupported KTX file format in %s", logName().constData());
+ KTXHeader header;
+ memcpy(&header, buf.data(), qktxh_headerSize);
+ if (!checkHeader(header)) {
+ qWarning(lcQtGuiTextureIO, "Unsupported KTX file format in %s", logName().constData());
return QTextureFileData();
}
QTextureFileData texData;
texData.setData(buf);
- texData.setSize(QSize(decode(header->pixelWidth), decode(header->pixelHeight)));
- texData.setGLFormat(decode(header->glFormat));
- texData.setGLInternalFormat(decode(header->glInternalFormat));
- texData.setGLBaseInternalFormat(decode(header->glBaseInternalFormat));
-
- texData.setNumLevels(decode(header->numberOfMipmapLevels));
- quint32 offset = headerSize + decode(header->bytesOfKeyValueData);
- const int maxLevels = qMin(texData.numLevels(), 32); // Cap iterations in case of corrupt file.
- for (int i = 0; i < maxLevels; i++) {
- if (offset + sizeof(KTXMipmapLevel) > dataSize) // Corrupt file; avoid oob read
- break;
- const KTXMipmapLevel *level = reinterpret_cast<const KTXMipmapLevel *>(buf.constData() + offset);
- quint32 levelLen = decode(level->imageSize);
- texData.setDataOffset(offset + sizeof(KTXMipmapLevel::imageSize), i);
- texData.setDataLength(levelLen, i);
- offset += sizeof(KTXMipmapLevel::imageSize) + levelLen + (3 - ((levelLen + 3) % 4));
+ texData.setSize(QSize(decode(header.pixelWidth), decode(header.pixelHeight)));
+ texData.setGLFormat(decode(header.glFormat));
+ texData.setGLInternalFormat(decode(header.glInternalFormat));
+ texData.setGLBaseInternalFormat(decode(header.glBaseInternalFormat));
+
+ texData.setNumLevels(decode(header.numberOfMipmapLevels));
+
+ const quint32 bytesOfKeyValueData = decode(header.bytesOfKeyValueData);
+ quint32 headerKeyValueSize;
+ if (qAddOverflow(qktxh_headerSize, bytesOfKeyValueData, &headerKeyValueSize)) {
+ qWarning(lcQtGuiTextureIO, "Overflow in size of key value data in header of KTX file %s",
+ logName().constData());
+ return QTextureFileData();
+ }
+
+ if (headerKeyValueSize >= quint32(buf.size())) {
+ qWarning(lcQtGuiTextureIO, "OOB request in KTX file %s", logName().constData());
+ return QTextureFileData();
+ }
+
+ // Technically, any number of levels is allowed but if the value is bigger than
+ // what is possible in KTX V2 (and what makes sense) we return an error.
+ // maxLevels = log2(max(width, height, depth))
+ const int maxLevels = (sizeof(quint32) * 8)
+ - qCountLeadingZeroBits(std::max(
+ { header.pixelWidth, header.pixelHeight, header.pixelDepth }));
+
+ if (texData.numLevels() > maxLevels) {
+ qWarning(lcQtGuiTextureIO, "Too many levels in KTX file %s", logName().constData());
+ return QTextureFileData();
+ }
+
+ quint32 offset = headerKeyValueSize;
+ for (int level = 0; level < texData.numLevels(); level++) {
+ const auto imageSizeSlice = safeSlice(buf, offset, sizeof(quint32));
+ if (imageSizeSlice.isEmpty()) {
+ qWarning(lcQtGuiTextureIO, "OOB request in KTX file %s", logName().constData());
+ return QTextureFileData();
+ }
+
+ const quint32 imageSize = decode(qFromUnaligned<quint32>(imageSizeSlice.data()));
+ offset += sizeof(quint32); // overflow checked indirectly above
+
+ texData.setDataOffset(offset, level);
+ texData.setDataLength(imageSize, level);
+
+ // Add image data and padding to offset
+ quint32 padded = 0;
+ if (nearestMultipleOf4(imageSize, &padded)) {
+ qWarning(lcQtGuiTextureIO, "Overflow in KTX file %s", logName().constData());
+ return QTextureFileData();
+ }
+
+ quint32 offsetNext;
+ if (qAddOverflow(offset, padded, &offsetNext)) {
+ qWarning(lcQtGuiTextureIO, "OOB request in KTX file %s", logName().constData());
+ return QTextureFileData();
+ }
+
+ offset = offsetNext;
}
if (!texData.isValid()) {
- qCDebug(lcQtGuiTextureIO, "Invalid values in header of KTX file %s", logName().constData());
+ qWarning(lcQtGuiTextureIO, "Invalid values in header of KTX file %s",
+ logName().constData());
return QTextureFileData();
}
@@ -191,7 +271,7 @@ bool QKtxHandler::checkHeader(const KTXHeader &header)
(decode(header.numberOfFaces) == 1));
}
-quint32 QKtxHandler::decode(quint32 val)
+quint32 QKtxHandler::decode(quint32 val) const
{
return inverseEndian ? qbswap<quint32>(val) : val;
}
diff --git a/src/gui/util/qktxhandler_p.h b/src/gui/util/qktxhandler_p.h
index 19f7b0e79a..8da990aaac 100644
--- a/src/gui/util/qktxhandler_p.h
+++ b/src/gui/util/qktxhandler_p.h
@@ -68,7 +68,7 @@ public:
private:
bool checkHeader(const KTXHeader &header);
- quint32 decode(quint32 val);
+ quint32 decode(quint32 val) const;
bool inverseEndian = false;
};
--
2.43.0
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