Method FromFile

view/sharedcache/core/SharedCache.cpp:46–145

}

CacheEntry CacheEntry::FromFile(const std::string& filePath, const std::string& fileName, CacheEntryType type)
{
	auto file = FileAccessorCache::Global().Open(filePath).lock();

	// TODO: Pull this out into another function so we can do IsValidDSCFile or something.
	// We first want to make sure that the base file is dyld.
	// All entries must start with "dyld".
	DataBuffer sig = file->ReadBuffer(0, 4);
	if (sig.GetLength() != 4)
		throw std::runtime_error("File is empty!");
	const char* magic = static_cast<char*>(sig.GetData());
	if (strncmp(magic, "dyld", 4) != 0)
		throw std::runtime_error("File does not start with `dyld`!");

	// Read the header, this _should_ be compatible with all known DSC formats.
	// Mason: the above is not true! https://github.com/Vector35/binaryninja-api/issues/6073
	// The mappingOffset should point right after the header. We use this to constrain the read size so unsupported fields are zeroed.
	size_t headerSize = file->ReadUInt32(0x10);
	dyld_cache_header header = {};
	// Truncate buffer length (headerSize) if larger than our `dyld_cache_header` for reading.
	file->Read(&header, 0, std::min(headerSize, sizeof(dyld_cache_header)));

	// Read the mappings using the headers `mappingCount` and `mappingOffset`.
	dyld_cache_mapping_info currentMapping = {};
	std::vector<dyld_cache_mapping_info> mappings;
	for (size_t i = 0; i < header.mappingCount; i++)
	{
		file->Read(&currentMapping, header.mappingOffset + (i * sizeof(currentMapping)), sizeof(currentMapping));

		// Cancel adding the entry if we have an invalid mapping.
		if (currentMapping.fileOffset + currentMapping.size > file->Length())
			throw std::runtime_error("Invalid mapping in shared cache entry");

		// TODO: Check initProt to make sure its in the range of expected values.

		mappings.push_back(currentMapping);
	}

	// Handle special entry types.
	if (fileName.find(".dylddata") != std::string::npos)
	{
		// We found a single dyld data cache entry file. Mark it as such!
		type = CacheEntryType::DyldData;
	}
	else if (fileName.find(".symbols") != std::string::npos && mappings.size() == 1)
	{
		// We found a single symbols cache entry file. Mark it as such!
		type = CacheEntryType::Symbols;
		// Adjust the mapping for the symbol file, they seem to be only for the header.
		// If we do not adjust the mapping than we will not be able to read the symbol table through the virtual memory.
		mappings[0].fileOffset = 0;
		mappings[0].size = file->Length();
	}
	else if (mappings.size() == 1 && header.imagesCountOld == 0 && header.imagesCount == 0
		&& header.imagesTextOffset == 0)
	{
		// Stub entry file, should only have a single mapping and no images.
		// NOTE: If we end up identifying something incorrectly as a stub we need to restrict this further.