Check for integer overflow.

Author: kevinbackhouse

src/psdimage.cpp

@@ -284,6 +284,9 @@ void PsdImage::readResourceBlock(uint16_t resourceId, uint32_t resourceSize) {
       nativePreview.height_ = getLong(buf + 8, bigEndian);
       const uint32_t format = getLong(buf + 0, bigEndian);
 
+      Internal::enforce(nativePreview.size_ <= static_cast<size_t>(std::numeric_limits<long>::max()),
+                        Exiv2::ErrorCode::kerCorruptedMetadata);
+
       if (nativePreview.size_ > 0 && nativePreview.position_ > 0) {
         io_->seek(static_cast<long>(nativePreview.size_), BasicIo::cur);
         if (io_->error() || io_->eof())
@@ -524,7 +527,7 @@ void PsdImage::doWriteMetadata(BasicIo& outIo) {
   if (outIo.error())
     throw Error(ErrorCode::kerImageWriteFailed);
 
-    // Update length of resources
+  // Update length of resources
 #ifdef EXIV2_DEBUG_MESSAGES
   std::cerr << "newResLength: " << newResLength << "\n";
 #endif