Harden-Runner GitHub Action installs a security agent on the GitHub-hosted runner (Ubuntu VM) to

1. Prevent exfiltration of credentials
2. Detect compromised dependencies and build tools
3. Detect tampering of source code during build

Compromised dependencies and build tools typically make outbound calls to exfiltrate data or credentials, or may tamper source code, dependencies, or artifacts during the build.

Harden-Runner GitHub Actions installs a daemon that monitors process, file, and network activity to:

Read this case study on how Harden-Runner detected malicious packages in the NPM registry.

1. Add step-security/harden-runner to your GitHub Actions workflow file as the first step in each job.

   steps:
     - uses: step-security/harden-runner@2e205a28d0e1da00c5f53b161f4067b052c61f34
       with:
         egress-policy: audit

2. In the workflow logs, you will see a link to security insights and recommendations.

3. Click on the link (example link). You will see a process monitor view of what activities happened as part of each step.

4. Below the insights, you will see the recommended policy. Add the recommended outbound endpoints to your workflow file, and only traffic to these endpoints will be allowed. When you use egress-policy: block mode, you can also set disable-telemetry: true to not send telemetry to the StepSecurity API.

5. If outbound network call is made to an endpoint not in the allowed list or if source code is tampered, you will see an annotation in the workflow run.

Install the Harden Runner App to use Harden-Runner GitHub Action for Private repositories.

• If you use Harden-Runner GitHub Action in a private repository, the generated insights URL is NOT public.
• You need to authenticate first to access insights URL for private repository. Only those who have access to the repository can view it.
• Harden Runner App only needs actions: read permissions on your repositories.

Read this case study on how Kapiche uses Harden Runner to improve software supply chain security in their open source and private repositories.

If you have questions or ideas, please use discussions.

1. Support for private repositories
2. Where should allowed-endpoints be stored?
3. Cryptographically verify tools run as part of the CI/ CD pipeline

1. Harden-Runner GitHub Action only works for GitHub-hosted runners. Self-hosted runners are not supported.
2. Only Ubuntu VM is supported. Windows and MacOS GitHub-hosted runners are not supported. There is a discussion about that here.
3. Detecting overwriting of source code only checks for a subset of file extensions right now. These files extensions are ".c", ".cpp", ".cs", ".go", ".java". We will be adding more extensions and options around detecting overwriting of source code in future releases.
4. Harden-Runner is not supported when job is run in a container as it needs sudo access on the Ubuntu VM to run. It can be used to monitor jobs that use containers to run steps. The limitation is if the entire job is run in a container. That is not common for GitHub Actions workflows, as most of them run directly on ubuntu-latest.

I think this is a great idea and for the threat model of build-time, an immediate network egress request monitoring makes a lot of sense - Liran Tal, GitHub Star, and Author of Essential Node.js Security

Harden-Runner strikes an elegant balance between ease-of-use, maintainability, and mitigation that I intend to apply to all of my 300+ npm packages. I look forward to the tool’s improvement over time - Jordan Harband, Open Source Maintainer

Harden runner from Step security is such a nice solution, it is another piece of the puzzle in helping treat the CI environment like production and solving supply chain security. I look forward to seeing it evolve. - Cam Parry, Staff Site Reliability Engineer, Kapiche

Some important workflows using harden-runner:

Harden-Runner GitHub Action downloads and installs the StepSecurity Agent.

• The code to monitor file, process, and network activity is in the Agent.
• The agent is written in Go and is open source at https://github.com/step-security/agent
• The agent's build is reproducible. You can view the steps to reproduce the build here.