Share Paste O₂

Introduction

Share Paste is a privatebin client for android.

This app allows you to quickly share some text and optionally an attachment, such that the hosting server can't read the contents of the paste you share. In other words, your share is end to end encrypted. Also you can set your paste to expire and auto destruct 💣 after a set duration. Or burn on read 🔥 (Mission Impossible style) if you like, to prevent unintended persons from accessing it later.

What you might use this for?

• You have to share some sensitive info quick and your messenger does not support E2EE (or you can't trust it's security enough).
• You need to share some text on a forums/discord/irc but don't want it to linger online for eternity.
• You want to post something anonymously that should be visible only for limited duration.
• You love burn on read feature just cuz, or wish to surprise someone with a special message. Happy Birthday ;)
• And more. Use your imagination!

Where to get it?

You can also download apk directly from GitHub. Please see releases.

How it works?

In short:

1. A secure key is randomly generated and used to encrypt your paste, on device. #local
2. The encrypted paste is sent to the server, who responds with location of your temporarily saved opaque paste. #remote
3. The paste location and the secret used to derive key are merged into a link that you can share with intended receiver.

When receiver opens the link, the encrypted paste is retrieved, and decrypted locally, with server none the wiser regarding it's contents. If set to Burn On Read, the server also immediately deletes the paste after it has been retrieved once.

Usage / Wiki

Please find features+screenshots in wiki.

Developer section

This app is powered by Kotlin 🏝️ and Rust 🦀.

• Encryption and sending uses Rust code, using the same library that powers pbcli.
• UI is written in Jetpack Compose with Kotlin helping wrap the Rust library.
• Bridging between Rust world and Java/Kotlin world is thanks to UniFFI project by Mozilla.

How to build

Source the code

This project sources the pbcli library dependency as a git submodule. Assuming you have already cloned this repository like so.

git clone https://github.com/nain-F49FF806/sharepaste.oo.git

Next we need to init and retrieve the submodule

git submodule update --init 

(Optionally) Enable app version auto increment on new commit.

ln -s ../../.githooks/pre-commit .git/hooks/

Rust the environment

You will need cargo-ndk installed to build this library for Android.

cargo install [email protected] --locked
rustup target add aarch64-linux-android armv7-linux-androideabi

Android the Studio

After above you should be able to open the android folder in Android Studio, and build in a few steps

• Open sdk manager and install a recent / recommennded NDK
• Open Build Variants tool window, and for app module select flavor you want (default source-ambientRelease is safe bet)
• Build menu > Build Bundle(s) / APK(s) > Build Apk

Voila! If you do have trouble, please open an issue.

Project structure

Location	Notes
rust/pbcli	rust library with uniffi bindings. Implements the privatebin api. Loaded as git submodule
android/rsnative	Module to build rust libraries for android native and to contain their wrapping kotlin code.
android/rsnative/build.gradle	Customizable configuration for above (see cargoNdk section)
android/app	User facing, android app features

Build variants / flavors

This app comes in 3 flavors, with only difference being the icons used / theme customization to help tell the source.

	flavor	purpose
1	ambient (default)	You should use this for local builds or redistribution. You may replace the icon, but not adapt or modify it.
2	fdroid	This flavor is for official f-droid distribution.
3	original	This is for builds from the original source repo. you are not granted rights to use media from this flavor.

Contributing

Contributions are welcome. Both, code and non-code contributions are appreciated.

Any code contributions shall be assumed to come with same license as the repository, unless you explicitly make additional grants.

Some ideas / Current to do:

• Receive text share intents, so we can encrypt the shared text [done]
• Receive arbitrary file share intents, so we can encrypt as attachment [done]
• Keep a record of shared links (configurable), and their expiry date/time

Once Share Paste is aware of attachments, we can start opening (decryption) links locally.

Credits

• The uniffi-starter template by Ian Wagner provides the base for Android <=> Rust bridge setup.
• pbcli developer Mydayyy. Thanks for such enthusiastic, swift and smooth collaboration.
• Mozilla & community for actively working on their UniFFI system and fielding questions.
• Phind-34B provided initial guidance in regard to Compose UI.
• Me, for sticking through the tough bits and bringing this to you! :)