mullvadvpn-app/android/BuildInstructions.md

Build instructions

This document aims to explain how to build the Mullvad Android app. It's strongly recommended and primarily supported to build the app using the provided container, as it ensures the correct build environment.

Build process

The build process consist of two main steps. First building the native libraries (mullvad-daemon and wireguard-go) and then building the Android app/project which will bundle the previously built native libraries. Building the native libraries requires some specific toolchains and packages to be installed, so it's recommended to build using the provided build script and container image.

The native libraries doesn't have to be rebuilt very often, only when including daemon changes or after cleaning the project, so apart from that it's possible to build the Android app/project using the Gradle CLI or the Android Studio GUI.

Build with provided container (recommended)

NOTE: Build with provided container is only supported on Linux and may not work on other platforms.

Building both the native libraries and Android project can easily be achieved by running the containerized-build.sh script, which helps using the correct tag and mounting volumes. The script relies on podman by default, however another container runner such as docker can be used by setting the CONTAINER_RUNNER environment variable.

After the native libraries have been built, subsequent builds can that doesn't rely on changes to the native libraries can be ran using the Gradle CLI or the Android Studio GUI. This requires either:

• Rust to be installed, since a tooled called mullvad-version is used to resolved the version information for the Android app.

or

• Specifying custom version information by following these instructions.

Setup:

• Install podman and make sure it's configured to run in rootless mode.

• OPTIONAL: Get the latest stable Rust toolchain via rustup.rs.

Debug build

Run the following command to trigger a full debug build:

../building/containerized-build.sh android --dev-build

Release build

1. Configure a signing key by following these instructions.
2. Run the following command after setting the ANDROID_CREDENTIALS_DIR environment variable to the directory configured in step 1:

../building/containerized-build.sh android --app-bundle

Build without* the provided container

NOTE: This guide is only supported on Linux and may not work on other platforms, if you are using macOS please refer to macOS build instructions

Building without the provided container requires installing multiple Sdk:s and toolchains, and is therefore more complex.

*: A container is still used to build wireguard-go for Android since it requires a patched version of go. See this patch for more information.

Setup build environment

These steps explain how to manually setup the build environment on a Linux system.

1. Install podman

Podman is required to build wireguard-go. Follow the installation instructions for your distribution.

2. Install protobuf-compiler

Install a protobuf compiler (version 3 and up), it can be installed on most major Linux distros via the package name protobuf-compiler. An additional package might also be required depending on Linux distro:

• protobuf-devel on Fedora.
• libprotobuf-dev on Debian/Ubuntu.

3. Install gcc

4. Install Android toolchain

• Install the JDK

  sudo apt install zip openjdk-17-jdk
  

• Install the SDK

  The SDK should be placed in a separate directory, like for example ~/android or /opt/android. This directory should be exported as the $ANDROID_HOME environment variable.

  Note: if sdkmanager fails to find the SDK root path, pass the option --sdk_root=$ANDROID_HOME to the command above.

  cd /opt/android     # Or some other directory to place the Android SDK
  export ANDROID_HOME=$PWD
  
  wget https://dl.google.com/android/repository/commandlinetools-linux-11076708_latest.zip
  unzip commandlinetools-linux-11076708_latest.zip
  ./tools/bin/sdkmanager "platforms;android-33" "build-tools;30.0.3" "platform-tools"
  

• Install the NDK

  The NDK should be placed in a separate directory, which can be inside the $ANDROID_HOME or in a completely separate path. The extracted directory must be exported as the $ANDROID_NDK_HOME environment variable.

  cd "$ANDROID_HOME"  # Or some other directory to place the Android NDK
  wget https://dl.google.com/android/repository/android-ndk-r27c-linux.zip
  unzip android-ndk-r27c-linux.zip
  
  cd android-ndk-r27c
  export ANDROID_NDK_HOME="$PWD"
  

5. Install and configure Rust toolchain

• Get the latest stable Rust toolchain via rustup.rs.

• Configure Android cross-compilation targets and set up linker and archiver. This can be done by setting the following environment variables:

  Add to ~/.bashrc or equivalent:

  export NDK_TOOLCHAIN_DIR="$ANDROID_NDK_HOME/toolchains/llvm/prebuilt/linux-x86_64/bin"
  export AR_aarch64_linux_android="$NDK_TOOLCHAIN_DIR/llvm-ar"
  export AR_armv7_linux_androideabi="$NDK_TOOLCHAIN_DIR/llvm-ar"
  export AR_x86_64_linux_android="$NDK_TOOLCHAIN_DIR/llvm-ar"
  export AR_i686_linux_android="$NDK_TOOLCHAIN_DIR/llvm-ar"
  export CC_aarch64_linux_android="$NDK_TOOLCHAIN_DIR/aarch64-linux-android26-clang"
  export CC_armv7_linux_androideabi="$NDK_TOOLCHAIN_DIR/armv7a-linux-androideabi26-clang"
  export CC_x86_64_linux_android="$NDK_TOOLCHAIN_DIR/x86_64-linux-android26-clang"
  export CC_i686_linux_android="$NDK_TOOLCHAIN_DIR/i686-linux-android26-clang"
  export CARGO_TARGET_AARCH64_LINUX_ANDROID_LINKER="$NDK_TOOLCHAIN_DIR/aarch64-linux-android26-clang"
  export CARGO_TARGET_ARMV7_LINUX_ANDROIDEABI_LINKER="$NDK_TOOLCHAIN_DIR/armv7a-linux-androideabi26-clang"
  export CARGO_TARGET_I686_LINUX_ANDROID_LINKER="$NDK_TOOLCHAIN_DIR/i686-linux-android26-clang"
  export CARGO_TARGET_X86_64_LINUX_ANDROID_LINKER="$NDK_TOOLCHAIN_DIR/x86_64-linux-android26-clang"
  

• Install Android targets

  ./scripts/setup-rust android
  

• (Optional) Run the following to install a git post-checkout hook that will automatically run the setup-rust script when the Rust version specified in the rust-toolchain.toml file changes:

  .scripts/setup-rust install-hook
  

6. Download wireguard-go-rs submodule

Run the following command to download wireguard-go-rs submodule: git submodule update --init wireguard-go-rs/libwg/wireguard-go

Debug build

Run the following command to build a debug build:

../android/build.sh --dev-build

Release build

1. Configure a signing key by following these instructions.
2. Move, copy or symlink the directory from step 1 to ./credentials/ (<repository>/android/credentials/).
3. Run the following command to build:

   ../android/build.sh --app-bundle
   

Configure signing key

1. Create a directory to store the signing key, keystore and its configuration:

   export ANDROID_CREDENTIALS_DIR=/tmp/credentials
   mkdir -p $ANDROID_CREDENTIALS_DIR
   

2. Generate a key/keystore named app-keys.jks in ANDROID_CREDENTIALS_DIR and make sure to write down the used passwords:

   keytool -genkey -v -keystore $ANDROID_CREDENTIALS_DIR/app-keys.jks -alias release -keyalg RSA -keysize 4096 -validity 10000
   

3. Create a file named keystore.properties in ANDROID_CREDENTIALS_DIR. Enter the following, but replace key-password and keystore-password with the values from step 2:

   keyAlias = release
   keyPassword = key-password
   storePassword = keystore-password
   

Gradle dependency metadata verification lockfile

This lockfile helps ensuring the integrity of the gradle dependencies in the project.

Update lockfile

When adding or updating dependencies, it's necessary to also update the lockfile. This can be done in the following way:

1. Run update script:

   ./scripts/lockfile -u
   

   If you're on macOS make sure GNU sed is installed. Install with brew install gnu-sed and add it to your PATH so that it is used instead of the sed macOS ships with PATH="$HOMEBREW_PREFIX/opt/gnu-sed/libexec/gnubin:$PATH"

2. Check diff before committing.

Disable during development

This is easiest done by temporarily removing the lockfile:

rm ./gradle/verification-metadata.xml

Gradle properties

Some gradle properties can be set to simplify development, for the full list see android/gradle.properties. In order to override them, add the properties in <USER_GRADLE_HOME>/gradle.properties. See the gradle documentation for more info of the prioritization of properties.

Override version code and version name

To avoid or override the rust based version generation, the mullvad.app.config.override.versionCode and mullvad.app.config.override.versionName properties can be set:

mullvad.app.config.override.versionCode=123
mullvad.app.config.override.versionName=1.2.3

Disable version in-app notifications

To disable in-app notifications related to the app version during development or testing, the mullvad.app.config.inAppVersionNotifications.enable property can be set:

mullvad.app.config.inAppVersionNotifications.enable=false

Run tests highly affected by rate limiting

To avoid being rate limited we avoid running tests sending requests that are highly rate limited too often. If you want to run these tests you can override the mullvad.test.e2e.config.runHighlyRateLimitedTests gradle properties. The default value is false.

Reproducible builds

Reproducible builds are a way to verify that the app was built from the exact source code it claims to be built from. When a build is reproducible, compiling the same source code with the same tools will always produce bit-for-bit identical output.

The Mullvad Android app is by default reproducible when built using our build container, as the container ensures a consistent build environment with fixed versions of all tools and dependencies.

When building without the container on Linux systems, reproducibility depends on having the exact same versions of system tools (compilers, build tools, etc) installed. Small differences in tool versions or configurations can lead to different build outputs even when using the same source code.

Make sure that any gradle.properties has not changed or been overridden it will affect the reproducibility of the build such as changing mullvad.app.build.cargo.targets and mullvad.app.config.inAppVersionNotifications.enable.

To maximize reproducibility when building without the container:

• Build the app on a Linux system or virtual machine.
• Use the exact same versions of all build dependencies as specified in the root Dockerfile and Android Dockerfile. This includes for example the Go version and Android SDK and NDK versions.

How to verify reproducible builds across environments

A simple way to check that a build is reproducible across environments is to build the fdroid version of the app with and without the container and comparing the checksums of the produced APKs.

1. Build the app with the container: ../building/containerized-build.sh android --fdroid
2. Copy the resulting APK to a different folder as it will be overwritten in the following step: app/build/outputs/apk/ossProd/fdroid/app-oss-prod-fdroid-unsigned.apk fdroid-container.apk
3. Build the app locally without the container: ./build.sh --fdroid
4. Compare the checksums of the two APKs: sha256sum fdroid-container.apk app/build/outputs/apk/ossProd/fdroid/app-oss-prod-fdroid-unsigned.apk

Verifying that an official release is reproducible

1. Obtain the release APK (2025.2-beta1 or newer) from GitHub releases
2. Checkout the release tag: git checkout android/<version>
3. Build a release build using our build instructions
4. Delete the signatures from the two APKs by running zip -d app-oss-prod-release.apk "META-INF/*" and zip -d MullvadVPN-<version>.apk "META-INF/*"
5. Compare the checksums of the two APKs: sha256sum app-oss-prod-release.apk MullvadVPN-<version>.apk. If the checksums are equal the build is reproducible.

Troubleshooting reproducibility

If two APKs built from the same commit have different checksums the build is not reproducible. This could be because of either:

1. A build dependency on the local system has the wrong version.
2. There is a bug that breaks the build reproducibility.
3. The APK built is a version prior to 2025.2-beta1, which is the first version that supports reproducible builds.

If you suspect that a bug is causing the build to not be reproducible, please open a Github issue.