arizzix / ssh-key-action

GitHub Action that installs SSH key to .ssh

Install SSH Key

This action installs SSH key in ~/.ssh.

Useful for SCP, SFTP, and rsync over SSH in deployment script.

tested on:

• all available virtual machines (Windows Server 2019/2016, macOS Catalina, and Ubuntu 20.04/18.04)
• Docker container (Ubuntu) / requires openssh-client package; apt install -y openssh-client
• Docker container (CentOS) / requires openssh-clients package; yum install -y openssh-clients
• Docker container (Alpine Linux) / requires openssh-client package; apk add openssh-client

Usage

Add your SSH key to your product secrets by clicking Settings - Secrets - Add a new secret beforehand.

PEM(RSA), PKCS8, and RFC4716(OpenSSH) formats are OK.

runs-on: ubuntu-latest
steps:
- name: Install SSH key
  uses: shimataro/ssh-key-action@v2
  with:
    key: ${{ secrets.SSH_KEY }}
    name: id_rsa # optional
    known_hosts: ${{ secrets.KNOWN_HOSTS }}
    config: ${{ secrets.CONFIG }} # ssh_config; optional
    if_key_exists: fail # replace / ignore / fail; optional (defaults to fail)
- name: rsync over ssh
  run: rsync ./foo/ user@remote:bar/

See Workflow syntax for GitHub Actions for details.

Install multiple keys

If you want to install multiple keys, call this action multiple times. It is useful for port forwarding.

NOTE: When this action is called multiple times, the contents of known_hosts and config will be appended. key must be saved as different name, by using name option.

runs-on: ubuntu-latest
steps:
- name: Install SSH key of bastion
  uses: shimataro/ssh-key-action@v2
  with:
    key: ${{ secrets.SSH_KEY_OF_BASTION }}
    name: id_rsa-bastion
    known_hosts: ${{ secrets.KNOWN_HOSTS_OF_BASTION }}
    config: |
      Host bastion
        HostName xxx.xxx.xxx.xxx
        User user-of-bastion
        IdentityFile ~/.ssh/id_rsa-bastion
- name: Install SSH key of target
  uses: shimataro/ssh-key-action@v2
  with:
    key: ${{ secrets.SSH_KEY_OF_TARGET }}
    name: id_rsa-target
    known_hosts: ${{ secrets.KNOWN_HOSTS_OF_TARGET }} # will be appended to existing .ssh/known_hosts
    config: |                                         # will be appended to existing .ssh/config
      Host target
        HostName yyy.yyy.yyy.yyy
        User user-of-target
        IdentityFile ~/.ssh/id_rsa-target
        ProxyCommand ssh -W %h:%p bastion
- name: SCP via port-forwarding
  run: scp ./foo/ target:bar/

Q&A

SSH failed even though key has been installed.

Check below:

• Host key verification failed.:
  • Set known_hosts parameter correctly (use ssh-keyscan command).

I want to replace/ignore key if exists.

Use if_key_exists parameter.

• replace: replaces key
• ignore: does nothing
• fail: fails (default)

How do I use encrypted SSH key?

This action doesn't support encrypted key directly. Here are some solutions:

• decrypting key beforehand: best bet, and works on any VM
• sshpass command: next best bet, but not supported on Windows
• expect command: be careful not to expose passphrase to console
• SSH_ASKPASS environment variable: might be troublesome

Which one is the best way for transferring files, "direct SCP/SFTP/rsync" or "SCP/SFTP/rsync via bastion"?

I recommend rsync via bastion.

rsync -e "ssh bastion ssh" ./foo/ target:bar/

It has some advantages over other methods:

• "Rsync via bastion" doesn't require to update workflow files and secrets even if it is necessary to transfer files to multiple servers.
  • Other methods require to update known_hosts if servers have changed.
• Rsync:
  • is fastest of all.
  • does NOT break files even if disconnected during transferring.
  • can remove files that don't exist on server.
• SCP is deprecated by OpenSSH due to outdated and inflexible protocol.
• Using bastion is more secure because:
  • it is not necessarily to expose SSH port on servers to public.
    • Address filtering is less effective.
    • Because Azure address range is very wide.
    • And will be updated continuously.
  • if security incident ―e.g., private key leaked― occurs, it's OK just to remove authorized_keys on bastion.

I want to omit known_hosts.

First of all, you have to understand that it is NOT secure to SSH with no known_hosts and using StrictHostKeyChecking=no option.

Why do you want to omit it? If the reason is "I'm not understanding about the function of known_hosts" or "It's bother to fetch server key", you should not omit. If "It is hard to prefetch server key because the server will be created dynamically", you can use bastion server.

"known_hosts is unnecessary because I'm using secure method for SSH, such as SSHFP and signed server key." — OK, here is a special value to omit known_hosts. You should use it ONLY IF you are using secure methods... It is known_hosts: unnecessary.

License

The scripts and documentation in this project are released under the MIT License

Changelog

See CHANGELOG.md.