Go Reproducer

This is a tool you can use to verify that golang binaries used by Briar (such as obfs4proxy and snowflake) were built exactly from the public source code and no modifications (such as backdoors) were added.

Current packages:

• https://mvnrepository.com/artifact/org.briarproject/obfs4proxy-android
• https://mvnrepository.com/artifact/org.briarproject/obfs4proxy-linux
• https://mvnrepository.com/artifact/org.briarproject/obfs4proxy-windows
• https://mvnrepository.com/artifact/org.briarproject/snowflake-android
• https://mvnrepository.com/artifact/org.briarproject/snowflake-linux
• https://mvnrepository.com/artifact/org.briarproject/snowflake-windows

More information about these so called reproducible builds is available at reproducible-builds.org.

The source code for this tool is available at https://code.briarproject.org/briar/go-reproducer

How to use

Make sure the version of Go you want to verify is included in versions.json.

Verify that you have docker installed:

docker --version

If this command does not work, please install Docker and continue once it is installed.

Note: While not guaranteed to work, it might also be possible to perform the steps below without Docker on a Debian stable system.

Using our pre-built image

If you trust that our pre-built Docker image was built exactly from its source, you can use it for faster verification. If not, you can read the next section to learn how to build the image yourself. Then you are only trusting the official debian:stable image which is out of our control.

Otherwise, you can skip the next section and move directly to Run the verification.

Building your own image

Check out the source repository:

git clone https://code.briarproject.org/briar/go-reproducer.git

Build our Docker image:

docker build -t briar/go-reproducer go-reproducer

To ensure reproducibility we build the image from a fixed snapshot of Debian and ignore expiry warnings for Debian packages. This means the build process inside the Docker container may use outdated packages that could contain known vulnerabilities.

Run the verification

To verify a specific version of a binary, run

docker run briar/go-reproducer:latest ./verify-binary.py <binary> [version]

Where <binary> is either obfs4proxy or snowflake and [version] is the version of the binary you want to test, for example 0.0.14-tor1.

You can find a list of versions in versions.json. These are based on tags in the source code repositories for obfs4proxy and snowflake.

If you leave out [version] it will build the latest version that was registered in versions.json.

In case there is an issue with the verification of an old build, this might be caused by an update of the container. You can try to use the original container by running:

docker run briar/go-reproducer:[version] ./verify-binary.py <binary> [version]

There should be a tag with the name [version] in this repository that you could be used to reproduce the old container. Note that this will not work if the issue is caused by an updated Debian package.

Only build the binary

To build a specific version of a binary without verifying it, run

docker run briar/go-reproducer:latest ./build-binary.py <binary> [version]