1.2.3 Generating Keys

Generating the Keys

Concourse's various components use RSA keys to verify tokens and worker registration requests.

A minimal deployment will require the following keys:

Session Signing Key

Used by the web node for signing and verifying user session tokens.

TSA Host Key

Used by the web node for the SSH worker registration gateway server ("TSA").

The public key is given to each worker node to verify the remote host when connecting via SSH.

Worker Key

Each worker node verifies its registration with the web node via a SSH key.

The public key must be listed in the web node's authorized worker keys file in order for the worker to register.

To generate these keys, run:

concourse generate-key -t rsa -f ./session_signing_key
concourse generate-key -t ssh -f ./tsa_host_key
concourse generate-key -t ssh -f ./worker_key

or use ssh-keygen:

ssh-keygen -t rsa -b 4096 -m PEM -f ./session_signing_key
ssh-keygen -t rsa -b 4096 -m PEM -f ./tsa_host_key
ssh-keygen -t rsa -b 4096 -m PEM -f ./worker_key

At this point you should have the following files:

  • session_signing_key

  • tsa_host_key

  • tsa_host_key.pub

  • worker_key

  • worker_key.pub

You can remove the session_signing_key.pub file if you have one, it is not needed by any process in Concourse.

Multiple Worker Keys

Currently you have one worker_key. You can use this one key-pair with multiple worker nodes. Another good strategy is to have each worker or group of workers use a key that's unique to that one worker or group of workers.

In the second case you will end up with multiple private and public worker keys. The web node needs to know about all of the public worker keys. To pass all public worker keys to the web node create a file that contains all of the worker public keys. A common name for this file is authorized_worker_keys.pub. The file should look like this, with one public key per line.

$ cat authorized_worker_keys.pub
ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAACAQCgKtVnbGRJ7Y63QKoO+loS...
ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAACAQDU6lA4gSRYIc4MXzphJ2l5...
ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAACAQDgNU7KBz/QQusPO52pNcea...

You should now have all the necessary keys needed to deploy Web and Worker nodes.