Convert base64 string to file without saving it to memory? - Flutter

Question

I have a base64 string and I want to open the correspondent file generated from this string, but without saving it to the phone's storage.

Initially, I have created a file from this base64 string and saved it to temporary storage, then open it, using open_file plugin from Flutter. But after I upload the .apk to AppSweep, it returns the following issue: Insecure file location is retrieved via getExternalMediaDirs. I have observed that the issue comes from the open_file library. Is there any other solution?

  Uint8List buffer = base64Decode(fileContent);

  final directory = await getTemporaryDirectory();

  int lastDotIndex = fileName.lastIndexOf('.');
  String formattedFileName = fileName.substring(0, lastDotIndex);
  String extension = fileName.substring(lastDotIndex + 1);

  File file = File(
      "${directory!.path}/${formattedFileName}.$extension");

  await file.writeAsBytes(buffer);
  await OpenFile.open(file.path);

Answer 1

The Issue Insecure file location is retrieved via getExternalMediaDirs only appears if your app calls android.content.Context.getExternalMediaDirs().

This is because those locations are not particularly secure see Android Docu:

These directories still exist and are scanned, but developers are encouraged to migrate to inserting content into a MediaStore collection directly, as any app can contribute new media to MediaStore with no permissions required, starting in Build.VERSION_CODES.Q.

The only file-related API you are using is getTemporaryDirectory, but that does not seem to store in the media dir, so I don't think this call is the reason for this finding.

Typically, AppSweep shows you the exact location and a code snippet of what it finds, does that help you to investigate the problem more?

Btw, if you want direct help in AppSweep, feel free to use the chat on the bottom right, then you can talk to one of the AppSweep team (e.g. me) directly.