Go Reproducer

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

Current packages:

• https://bintray.com/briarproject/org.briarproject/obfs4proxy
• https://bintray.com/briarproject/org.briarproject/obfs4proxy-android

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

Building the image might fail due to expired Debian packages. You can disable the expiry check by adding a build argument:

docker build --build-arg IGNORE_EXPIRY=1 -t briar/go-reproducer go-reproducer

However, note that this might expose the build process to MITM attacks which inject outdated vulnerable packages.

Run the verification

To verify a specific version of obfs4proxy, run

docker run briar/go-reproducer:latest ./verify-obfs4proxy.py [version]

Where [version] is the version of obfs4proxy you want to test, for example 0.3.3.6.

You can find a list of versions in obfs4proxy's source code repository. Just remove the obfs4proxy- from obfs4proxy-0.0.7.

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-obfs4proxy.py [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 obfs4proxy

To build a specific version of obfs4proxy, run

docker run briar/go-reproducer:latest ./build-obfs4proxy.py [version]