sshrimp 🦐

SSH Certificate Authority in a lambda, automated by an OpenID Connect enabled agent.

Why? Check out this presentation Zero Trust SSH - linux.conf.au 2020.

~~ Warning ~~

This is still in very early development. Only use for testing. Not suitable for use in production yet. PR's welcome ;)

Quickstart

This project uses mage as a build tool. Install it.

Build the agent, lambda, and generate terraform code ready for deployment:

mage

Deployment

Terraform files are defined in /terraform and the generated sshrimp-ca.tf.json file can be used to automatically deploy sshrimp into multiple AWS regions.

terraform init
terraform apply

You will need AWS credentials in your environment to run terraform apply. You can also use aws-vault or aws-oidc to more securely manage AWS credentials on the command line.

sshd_config (on your server)

Server configruation is minimal. Get the public keys from KMS (using AWS credentials):

mage ca:keys

Put these keys in a file on your server /etc/ssh/trusted_user_ca_keys, owned by root permissions 0644.

Modify /etc/ssh/sshd_config to add the line:

TrustedUserCAKeys /etc/ssh/trusted_user_ca_keys

ssh_config (on your local computer)

Since OpenSSH (>= 7.3), you can use the IdentityAgent option in your ssh config file to set the socketname you configured:

Host *.sshrimp.io
    User jeremy
    IdentityAgent /tmp/sshrimp-agent.sock

This has the advantage of only using the agent for the group of hosts you need, and let other hosts use your regular agent (like github.com for cloning git repos). In fact, you can't add other identities to the sshrimp-agent. It's meant to be used for only the hosts you need it for.

For other SSH clients or older versions, set the SSH_AUTH_SOCK environment variable when invoking ssh: SSH_AUTH_SOCK=/tmp/sshrimp-agent.sock ssh user@host

Let's go!

Start the agent:

sshrimp-agent /path/to/sshrimp.toml

SSH to your host:

ssh example.server.sshrimp.io

🎉

Why sshrimp?

• Shrimp have shells.
• Shrimp are lightweight.
• Has a backronym: SSH. Really. Isn't. My. Problem.
• Shrimp on a barbie?
• Yeah...