Overview
libsignal-client contains platform-agnostic APIs useful for Signal client apps, exposed as a Java,
Swift, or TypeScript library. The underlying implementations are written in Rust:
- libsignal-protocol: Implements the Signal protocol, including the Double Ratchet algorithm. A
replacement for libsignal-protocol-java and libsignal-metadata-java. - signal-crypto: Cryptographic primitives such as AES-GCM-SIV. We use RustCrypto's where we can
but sometimes have differing needs. - device-transfer: Support logic for Signal's device-to-device transfer feature.
- poksho: Utilities for implementing zero-knowledge proofs; stands for "proof-of-knowledge, stateful-hash-object". See zkgroup.
This repository is used by the Signal client apps (Android, iOS, and Desktop). Use
outside of Signal is unsupported. In particular, the products of this repository are the Java,
Swift, and TypeScript libraries that wrap the underlying Rust implementations. Those underlying
implementations are subject to change without notice, as are the JNI, C, and Node add-on "bridge"
layers.
Building
To build anything in this repository you must have Rust installed.
The build currently uses a specific version of the Rust nightly compiler, which
will be downloaded automatically by cargo. To build and test the basic protocol
libraries:
$ cargo build
...
$ cargo test
...
Java/Android
To build for Android you must install several additional packages including a JDK,
the Android NDK/SDK, and add the Android targets to the Rust compiler, using
rustup target add armv7-linux-androideabi aarch64-linux-android i686-linux-android x86_64-linux-android
as well as the Cargo NDK tool using
cargo install --version=1.0.0 cargo-ndk
To build the Java/Android jar and aar, and run the tests:
$ cd java
$ ./gradlew test
Alternately, a build system using Docker is available:
$ cd java
$ make java_test
Local Java testing is also supported with gradlew test if none of the ANDROID_* environment
variables are set.
When exposing new APIs to Java, you will need to run rust/bridge/jni/bin/gen_java_decl.py in
addition to rebuilding.
Swift
To learn about the Swift build process see swift/README.md
Node
You'll need Node installed to build. If you have nvm, you can run nvm use to select an
appropriate version automatically.
We use yarn as our package manager. The Rust library will automatically be built when you run yarn install.
$ nvm use
$ yarn install
$ yarn tsc
$ yarn test
When testing changes locally, you can use yarn build to do an incremental rebuild of the Rust library.
When exposing new APIs to Node, you will need to run rust/bridge/node/bin/gen_ts_decl.py in
addition to rebuilding.
Contributions
Signal does accept external contributions to this project. However unless the change is
simple and easily understood, for example fixing a bug or portability issue, adding a new
test, or improving performance, first open an issue to discuss your intended change as not
all changes can be accepted.
Contributions that will not be used directly by one of Signal's official client apps may still be
considered, but only if they do not pose an undue maintenance burden or conflict with the goals of
the project.
Signing a CLA (Contributor License Agreement) is required for all contributions.
Legal things
Cryptography Notice
This distribution includes cryptographic software. The country in which you currently reside may have restrictions on
the import, possession, use, and/or re-export to another country, of encryption software. BEFORE using any encryption
software, please check your country's laws, regulations and policies concerning the import, possession, or use, and
re-export of encryption software, to see if this is permitted. See http://www.wassenaar.org/ for more information.
The U.S. Government Department of Commerce, Bureau of Industry and Security (BIS), has classified this software as
Export Commodity Control Number (ECCN) 5D002.C.1, which includes information security software using or performing
cryptographic functions with asymmetric algorithms. The form and manner of this distribution makes it eligible for
export under the License Exception ENC Technology Software Unrestricted (TSU) exception (see the BIS Export
Administration Regulations, Section 740.13) for both object code and source code.
License
Copyright 2020-2021 Signal Messenger, LLC
Licensed under the AGPLv3: https://www.gnu.org/licenses/agpl-3.0.html