libsignal contains platform-agnostic APIs used by the official Signal clients and servers, 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. We use RustCrypto's where we can but sometimes have differing needs.
- device-transfer: Support logic for Signal's device-to-device transfer feature.
- attest: Functionality for remote attestation of SGX enclaves and server-side HSMs.
- zkgroup: Functionality for zero-knowledge groups and related features available in Signal.
- zkcredential: An abstraction for the sort of zero-knowledge credentials used by zkgroup, based on the paper "The Signal Private Group System" by Chase, Perrin, and Zaverucha.
- poksho: Utilities for implementing zero-knowledge proofs (such as those used by zkgroup); stands for "proof-of-knowledge, stateful-hash-object".
- account-keys: Functionality for consistently using PINs as passwords in Signal's Secure Value Recovery system, as well as other account-wide key operations.
- usernames: Functionality for username generation, hashing, and proofs.
- media: Utilities for manipulating media.
This repository is used by the Signal client apps (Android, iOS, and Desktop) as well as server-side. 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. All APIs and implementations are subject to change without notice, as are the JNI, C, and Node add-on "bridge" layers. However, backwards-incompatible changes to the Java, Swift, TypeScript, and non-bridge Rust APIs will be reflected in the version number on a best-effort basis, including increases to the minimum supported tools versions.
To build anything in this repository you must have Rust installed, as well as Clang, libclang, CMake, Make, protoc, and git.
On a Debian-like system, you can get these extra dependencies through apt:
$ apt-get install clang libclang-dev cmake make protobuf-compiler gitOn macOS, we have a best-effort maintained script to set up the Rust toolchain you can run by:
$ bin/mac_setup.shThe 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
...The basic tools above should get you set up for most libsignal Rust development.
Eventually, you may find that you need some additional Rust tools like cbindgen to modify the bridges to the
client libraries or taplo for code formatting.
You should always install any Rust tools you need that may affect the build from cargo rather than from your system
package manager (e.g. apt or brew). Package managers sometimes contain outdated versions of these tools that can break
the build with incompatibility issues (especially cbindgen).
To install the main Rust extra dependencies matching the versions we use, you can run the following commands:
$ cargo +stable install cbindgen cargo-fuzz
$ cargo +stable install --version "$(cat ../acknowledgments/cargo-about-version)" --locked cargo-about
$ cargo +stable install --version "$(cat ../.taplo-cli-version)" --locked taplo-cliTo 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
To build the Java/Android jar and aar, and run the tests:
$ cd java
$ ./gradlew test
$ ./gradlew build # if you need AAR outputsYou can pass -P debugLevelLogs to Gradle to build without filtering out debug- and verbose-level
logs from Rust.
Alternately, a build system using Docker is available:
$ cd java
$ makeWhen exposing new APIs to Java, you will need to run rust/bridge/jni/bin/gen_java_decl.py in
addition to rebuilding. This requires installing the cbindgen Rust tool, as detailed above.
Signal publishes Java packages on Maven Central for its own use, under the names org.signal:libsignal-server, org.signal:libsignal-client, and org.signal:libsignal-android. libsignal-client and libsignal-server contain native libraries for Debian-flavored x86_64 Linux as well as Windows (x86_64) and macOS (x86_64 and arm64). libsignal-android contains native libraries for armeabi-v7a, arm64-v8a, x86, and x86_64 Android.
When building for Android you need both libsignal-android and libsignal-client, but the Windows
and macOS libraries in libsignal-client won't automatically be excluded from your final app. You can
explicitly exclude them using packagingOptions:
android {
// ...
packagingOptions {
resources {
excludes += setOf("libsignal_jni*.dylib", "signal_jni*.dll")
}
}
// ...
}
You can additionally exclude libsignal_jni_testing.so if you do not plan to use any of the APIs
intended for client testing.
To learn about the Swift build process see swift/README.md
You'll need Node installed to build. If you have nvm, you can run nvm use to select an
appropriate version automatically.
We use npm as our package manager, and node-gyp to control building the Rust library.
$ cd node
$ nvm use
$ npm install
$ npx node-gyp rebuild # clean->configure->build
$ npm run tsc
$ npm run testWhen testing changes locally, you can use npm run build to do an incremental rebuild of the Rust library. Alternately, npm run build-with-debug-level-logs will rebuild without filtering out debug- and verbose-level logs.
When exposing new APIs to Node, you will need to run rust/bridge/node/bin/gen_ts_decl.py in
addition to rebuilding.
Signal publishes the NPM package @signalapp/libsignal-client for its own use, including native
libraries for Windows, macOS, and Debian-flavored Linux. Both x64 and arm64 builds are included for
all three platforms, but the arm64 builds for Windows and Linux are considered experimental, since
there are no official builds of Signal for those architectures.
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.
You can run the styler on the entire project by running:
just format-allYou can run more extensive tests as well as linters and clippy by running:
just check-pre-commitWhen making a PR that adjusts dependencies, you'll need to regenerate our acknowledgments files. See acknowledgments/README.md.
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.
Copyright 2020-2024 Signal Messenger, LLC
Licensed under the GNU AGPLv3: https://www.gnu.org/licenses/agpl-3.0.html