Encrypted disk cache with Glide 4.0

[MistaGreen]

Glide Version: 4.0

Issue details / Repro steps / Use case background: Encrypted disk cache

Hi,

I have been trying to add encryption to Glide disk cache. But it's not clear how to do that with Glide 4.0. I've implemented Encoder<InputStream> and ResourceDecoder<File, Bitmap>. I suppose that I should register them in AppGlideModule.

I found out that I can register Encoder like this

register(InputStream::class.java, SecureEncoder())

But what should I do with SecureDecoder to decode images from disk cache?

Please let me know if I'm on the right direction. It would be nice to have an example how to encode/decode images on disk cache.

Thank you.

[sjudd]

There's some documentation on this here: http://bumptech.github.io/glide/doc/configuration.html#registering-components. You can use append or prepend with your decoder. Prepend will let your decoder run first which is more efficient if most of your loads are from cache and less efficient if most loads are from other files. Append should work too, but Glide's default decoders will get to run first and, at least for encrypted files, will fail first, before your decoder gets to run.

[MistaGreen]

@sjudd Thank you for fast response!

I tried to follow the documentation and created following method:

override fun registerComponents(context: Context, glide: Glide, registry: Registry) {
registry.replace(NoteGlideModel::class.java, InputStream::class.java, OkHttpUrlLoader.Factory(okHttpClient))
registry.register(InputStream::class.java, SecureEncoder(securityManager))
registry.prepend(File::class.java, Bitmap::class.java, SecureDecoder(securityManager))
}

But Glide doesn't trigger my Encoder/Decoder. I'm not sure what's wrong. In the same time OkHttpClient has been injected successfully.

[sjudd]

Is the load failing? Or succeeding without calling your decoder?

If the load fails, Glide should print all of the paths it tried, can you include the exception message here? It may just not be trying to decode from the File or it may not be trying to decode to a Bitmap, for example.

[MistaGreen]

@sjudd
There are no exceptions. It looks like Glide just ignores my encoder/decoder. I can see images and default cache works. My Glide call looks like this:

Glide
.with(context)
.load(NoteGlideModel(url, hash))
.apply(RequestOptions()
.skipMemoryCache(true)
.centerCrop()
.placeholder(R.drawable.thumbnail_placeholder))
.into(imageView)

[sjudd]

Thanks. I looked a bit deeper here. Unfortunately the short answer is that this isn't well supported by the current API.

We'd need to:

1. Expose an API like replace() or prepend() for Encoders, right now you can only add new ones, not replace existing ones (

   glide/library/src/main/java/com/bumptech/glide/provider/EncoderRegistry.java

   Line 12 in 35c28c2

   public class EncoderRegistry {

   )
2. Do the same for ResourceEncoders (

   glide/library/src/main/java/com/bumptech/glide/provider/ResourceEncoderRegistry.java

   Line 13 in 35c28c2

   public class ResourceEncoderRegistry {

   ).

You'd also need to add a ResourceEncoder to write your transformed resources to disk. Encoders write data (InputStreams), ResourceEncoders write resources (Bitmaps). The source of your load (local or remote) and your DiskCacheStrategy determines which encoder is used (both, one or the other, or none).

If you're interested in sending a PR for 1 and 2 above I'd be happy to review them.

[MistaGreen]

@sjudd
Thank you! I've created #2349 PR to add required features.

[TonyTangAndroid]

Hi @MistaGreen, is the Encrypted disk cache sample could be accessed now?
I am interested to know the example of SecureEncoder and SecureDecoder.

SecureEncoder(securityManager)
SecureDecoder(securityManager)

[MistaGreen]

Hi @TonyTangAndroid. I haven't finished it yet. I'll try to open source it when it will be ready.

[TonyTangAndroid]

I just had managed to get it working, thank to your hint on this thread. And thank you for letting me know it will be opensourced. Looking forward to it.

[LuYeCong]

Hi @TonyTangAndroid. I am new to Glide. And I also need to Encrypted disk cache. Can you show me a sample? I am confused to implement SecureEncoder and SecureDecoder . Thank you very much!

[TonyTangAndroid]

Hi @LuYeCong, currently I am on vacation and could not guarantee to find a proper time to share the demo with you. Will keep you posted ASAP, which could be expected in 48 hours or so.

[TonyTangAndroid]

@LuYeCong https://github.com/TonyTangAndroid/GlideEncyptionDemo please refer to this sample.

[LuYeCong]

@TonyTangAndroid Thank you very much! But I still have some questions about
registry.append(String.class, InputStream.class, new UsherImageModelLoader.Factory());
What is this used for? Is the UsherImageModelLoader necessary?