How can I extract secrets using GitHub Actions?

Question

I have a fairly basic scenario. I made a dedicated ssh key for this purpose and added it to my repository secrets.

1. Code gets pushed to master

2. GitHub action uploads it to server using ssh by doing echo "${{ secrets.SSH_KEY }}" > key.

3. After that I can use this key to connect to my server e.g. ssh -i key [email protected] lsb_release -a

The problem is that for some reason GitHub actions cannot write it to file, it writes characters *** instead of the actual secret value into the file. Therefore obviously I cannot connect to my server.

How can I connect with ssh using this secret? Is there a way to connect without using a file? Can someone who did this common scenario using GitHub actions shed some light?

Answer 1

GitHub Actions should be able to write a secret to a file this way. The reason you see the stars is that the log is filtered, so if a secret would be logged, it's replaced in the log with three asterisks instead. This is a security measure against an accidental disclosure of secrets, since logs are often publicly available.

However, it's a good idea to avoid writing the secret to the log anyway if possible. You can write your command like this so you don't write the secret to the log:

    - run: 'echo "$SSH_KEY" > key'
      shell: bash
      env:
        SSH_KEY: ${{secrets.SSH_KEY}}

All you'll see in the log is echo "$SSH_KEY" > key, not the secret or any asterisks.

Note that you do want quotes here, since the > character is special to YAML.

If this doesn't work to log into your server, there's likely a different issue; this technique does work for writing secrets in the general case.