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Fix buffer overflow in XBM parser 

Avoid parsing over the buffer limit, or interpreting non-hex
as hex.

This still leaves parsing of lines longer than 300 chars
unreliable

Change-Id: I1c57a7e530c4380f6f9040b2ec729ccd7dc7a5fb
Pick-to: 5.15 5.12
Reviewed-by: Robert Loehning <robert.loehning@qt.io>
Reviewed-by: Eirik Aavitsland <eirik.aavitsland@qt.io>
bb10
Allan Sandfeld Jensen 2020-07-23 11:48:48 +02:00
parent 61a50b2b9b
commit c562c1fc19
2 changed files with 41 additions and 1 deletions
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4
src/gui/image/qxbmhandler.cpp
View File

@ -161,7 +161,9 @@ static bool read_xbm_body(QIODevice *device, int w, int h, QImage *outImage)
w = (w+7)/8; // byte width
while (y < h) { // for all encoded bytes...
if (p) { // p = "0x.."
if (p && p < (buf + readBytes - 3)) { // p = "0x.."
if (!isxdigit(p[2]) || !isxdigit(p[3]))
return false;
*b++ = hex2byte(p+2);
p += 2;
if (++x == w && ++y < h) {

38
tests/auto/gui/image/qimagereader/tst_qimagereader.cpp
View File

@ -175,6 +175,8 @@ private slots:
void xpmBufferOverflow();
void xbmBufferHandling();
private:
QString prefix;
QTemporaryDir m_temporaryDir;
@ -2055,5 +2057,41 @@ void tst_QImageReader::xpmBufferOverflow()
QImageReader(":/images/oss-fuzz-23988.xpm").read();
}
void tst_QImageReader::xbmBufferHandling()
{
uint8_t original_buffer[256];
for (int i = 0; i < 256; ++i)
original_buffer[i] = i;
QImage image(original_buffer, 256, 8, QImage::Format_MonoLSB);
image.setColorTable({0xff000000, 0xffffffff});
QByteArray buffer;
{
QBuffer buf(&buffer);
QImageWriter writer(&buf, "xbm");
writer.write(image);
}
QCOMPARE(QImage::fromData(buffer, "xbm"), image);
auto i = buffer.indexOf(',');
buffer.insert(i + 1, " ");
QCOMPARE(QImage::fromData(buffer, "xbm"), image);
buffer.insert(i + 1, " ");
QCOMPARE(QImage::fromData(buffer, "xbm"), image);
buffer.insert(i + 1, " ");
#if 0 // Lines longer than 300 chars not supported currently
QCOMPARE(QImage::fromData(buffer, "xbm"), image);
#endif
i = buffer.lastIndexOf("\n ");
buffer.truncate(i + 1);
buffer.append(QByteArray(297, ' '));
buffer.append("0x");
// Only check we get no buffer overflow
QImage::fromData(buffer, "xbm");
}
QTEST_MAIN(tst_QImageReader)
#include "tst_qimagereader.moc"