No More Backdoors: Know Who Has Access to What, Right Now
Jun 13
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Machine ID with Ansible

Ansible is a common tool for managing fleets of Linux hosts via SSH. In order to connect to the hosts, it requires a form of authentication. Machine ID can be used to provide short-lived certificates to Ansible that allow it to connect to SSH nodes enrolled in Teleport in a secure and auditable manner.

In this guide, you will configure the Machine ID agent, tbot, to produce credentials and an OpenSSH configuration, and then configure Ansible to use these to connect to your SSH nodes through the Teleport Proxy Service.

Prerequisites

You will need the following tools to use Teleport with Ansible.

  • A running Teleport cluster version 16.0.0 or above. If you want to get started with Teleport, sign up for a free trial or set up a demo environment.

  • The tctl admin tool and tsh client tool.

    Visit Installation for instructions on downloading tctl and tsh.

  • ssh OpenSSH tool

  • ansible >= 2.9.6

  • Optional: jq to process JSON output

  • tbot must already be installed and configured on the machine that will run Ansible. For more information, see the deployment guides.

  • If you followed the above guide, note the --destination-dir=/opt/machine-id flag, which defines the directory where SSH certificates and OpenSSH configuration used by Ansible will be written.

    In particular, you will be using the /opt/machine-id/ssh_config file in your Ansible configuration to define how Ansible should connect to Teleport Nodes.

  • To check that you can connect to your Teleport cluster, sign in with tsh login, then verify that you can run tctl commands using your current credentials. tctl is supported on macOS and Linux machines.

    For example:

    tsh login --proxy=teleport.example.com --user=[email protected]
    tctl status

    Cluster teleport.example.com

    Version 16.0.0

    CA pin sha256:abdc1245efgh5678abdc1245efgh5678abdc1245efgh5678abdc1245efgh5678

    If you can connect to the cluster and run the tctl status command, you can use your current credentials to run subsequent tctl commands from your workstation. If you host your own Teleport cluster, you can also run tctl commands on the computer that hosts the Teleport Auth Service for full permissions.

Step 1/4. Configure RBAC

As Ansible will use the credentials produced by tbot to connect to the SSH nodes, you first need to configure Teleport to grant the bot access. This is done by creating a role that grants the necessary permissions and then assigning this role to a Bot.

In this example, access will be granted to all SSH nodes for the username root. Ensure that you set this to a username that is available across your SSH nodes and that will have the appropriate privileges to manage your nodes.

Create a file called role.yaml with the following content:

kind: role
version: v6
metadata:
  name: example-role
spec:
  allow:
    # Allow login to the user 'root'.
    logins: ['root']
    # Allow connection to any node. Adjust these labels to match only nodes
    # that Ansible needs to access.
    node_labels:
      '*': '*'

Replace example-role with a descriptive name related to your use case.

For production use, you should use labels to restrict this access to only the hosts that Ansible will need to access. This is known as the principal of least privilege and reduces damage that exfiltrated credentials can do.

Use tctl create -f ./role.yaml to create the role.

Now, use tctl bots update to add the role to the Bot. Replace example with the name of the Bot you created in the deployment guide and example-role with the name of the role you just created:

$ tctl bots update example --add-roles example-role

Step 2/4. Configure the tbot output

Now, tbot needs to be configured with an output that will produce the credentials and SSH configuration that is needed by Ansible. For SSH, we use the identity output type.

Outputs must be configured with a destination. In this example, the directory destination will be used. This will write these credentials to a specified directory on disk. Ensure that this directory can be written to by the Linux user that tbot runs as, and that it can be read by the Linux user that Ansible will run as.

Modify your tbot configuration to add an identity output:

outputs:
- type: identity
  destination:
    type: directory
    # For this guide, /opt/machine-id is used as the destination directory.
    # You may wish to customize this. Multiple outputs cannot share the same
    # destination.
    path: /opt/machine-id

If operating tbot as a background service, restart it. If running tbot in one-shot mode, it must be executed before you attempt to execute the Ansible playbook.

You should now see several files under /opt/machine-id:

  • ssh_config: this can be used with Ansible or OpenSSH to configure them to use the Teleport Proxy Service with the correct credentials when making connections.
  • known_hosts: this contains the Teleport SSH host CAs and allows the SSH client to validate a host's certificate.
  • key-cert.pub: this is an SSH certificate signed by the Teleport SSH user CA.
  • key: this is the private key needed to use the SSH certificate.

Next, Ansible will be configured to use these files when making connections.

Step 3/4. Configure Ansible

Create a folder named ansible where all Ansible files will be collected.

mkdir -p ansible
cd ansible

Create a file called ansible.cfg. We will configure Ansible to run the OpenSSH client with the configuration file generated by Machine ID, /opt/machine-id/ssh_config. Note, example.com here is the name of your Teleport cluster.

[defaults]host_key_checking = Trueinventory=./hostsremote_tmp=/tmp
[ssh_connection]scp_if_ssh = Truessh_args = -F /opt/machine-id/ssh_config

You can then create an inventory file called hosts. This should refer to the hosts using their hostname as registered in Teleport and the name of your Teleport cluster should be appended to this. For example, if your cluster is called teleport.example.com and your host is called node1, the entry in hosts would be node1.teleport.example.com.

You can generate an inventory file for all your nodes that meets this requirement with a script like the following:

Source tsh env to get the name of the current Teleport cluster.

eval "$( tsh env )"

You can modify the `tsh ls` command to filter nodes based ont he label.

tsh ls --format=json | jq --arg cluster $TELEPORT_CLUSTER -r '.[].spec.hostname + "." + $cluster' > hosts

When Teleport's Auth Service receives a request to list Teleport Nodes (e.g., to display Nodes in the Web UI or via tsh ls), it only returns the Nodes that the current user is authorized to view.

For each Node in the user's Teleport cluster, the Auth Service applies the following checks in order and, if one check fails, hides the Node from the user:

  • None of the user's roles contain a deny rule that matches the Node's labels.
  • At least one of the user's roles contains an allow rule that matches the Node's labels.

If you are not seeing Nodes when expected, make sure that your user's roles include the appropriate allow and deny rules as documented in the Teleport Access Controls Reference.

Step 4/4. Run a playbook

Finally, let's create a simple Ansible playbook, playbook.yaml. The example playbook below runs hostname on all hosts.

- hosts: all
  remote_user: root
  tasks:
    - name: "hostname"
      command: "hostname"

From the folder ansible, run the Ansible playbook:

ansible-playbook playbook.yaml

PLAY [all] *****************************************************************************************************************************************

TASK [Gathering Facts] *****************************************************************************************************************************

ok: [terminal]

TASK [hostname] ************************************************************************************************************************************

changed: [terminal]

PLAY RECAP *****************************************************************************************************************************************

terminal : ok=2 changed=1 unreachable=0 failed=0 skipped=0 rescued=0 ignored=0

You are all set. You have provided your machine with short-lived certificates tied to a machine identity that can be rotated, audited, and controlled with all the familiar Teleport access controls.

Troubleshooting

In case if Ansible cannot connect, you may see error like this one:

example.host | UNREACHABLE! => {
    "changed": false,
    "msg": "Failed to connect to the host via ssh: ssh: Could not resolve hostname node-name: Name or service not known",
    "unreachable": true
}

You can examine and tweak patterns matching the inventory hosts in ssh_config.

Try the SSH connection using ssh_config with verbose mode to inspect the error:

ssh -vvv -F /opt/machine-id/ssh_config root@node-name.example.com

If ssh works, try running the playbook with verbose mode on:

ansible-playbook -vvv playbook.yaml

Next steps