Joining Services via AWS EC2 Identity Document

This guide explains how to use the EC2 join method to configure Teleport processes to join your Teleport cluster without sharing any secrets when they a re running in AWS.

The EC2 join method is only available in self-hosted Teleport deployments. There are two other AWS join methods available depending on your use case:

1. The IAM join method is available to any Teleport process running anywhere with access to IAM credentials, such as an EC2 instance with an attached IAM role (see documentation). No specific permissions or IAM policy is required: an IAM role with no attached policies is sufficient. No IAM credentials are required on the Teleport Auth Service.
2. Tokens not signed by AWS: You can configure Teleport processes running on AWS to join a cluster via Teleport join tokens or, for Teleport processes running on Kubernetes, signed ServiceAccount tokens. These approaches allow you to join a Teleport process to a cluster when you don't want to rely on AWS-specific APIs, e.g., when adopting a cloud-agnostic approach.

How it works

The EC2 join method is available to any Teleport process running on an EC2 instance. Only one Teleport process per EC2 instance may use the EC2 join method. The process presents an EC2 instance identity document to the Teleport Auth Service.

Meanwhile, the Teleport Auth Service has AWS IAM credentials with ec2:DescribeInstances permissions in order to check that the identity document belongs to a legitimate EC2 instance. No IAM credentials are required on the Teleport processes joining the cluster.

Prerequisites

• A running self-hosted Teleport cluster. If you want to get started with self-hosted Teleport Enterprise, contact Sales. You can also set up a demo environment with Teleport Community Edition.

• The tctl admin tool and tsh client tool version >= 16.4.7.

  Visit Installation for instructions on downloading tctl and tsh.

• 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. For example:

  $ tsh login --proxy=teleport.example.com [email protected]
  $ tctl status
  # Cluster  teleport.example.com
  # Version  16.4.7
  # 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.
• An AWS EC2 instance to host a Teleport process, with the Teleport binary installed. The host should not have an existing data dir (/var/lib/teleport by default). Remove the data directory if this instance has previously joined a Teleport cluster.

Step 1/4. Set up AWS IAM credentials

The Teleport Auth Service needs permission to call ec2:DescribeInstances in order to check that the EC2 instances attempting to join your cluster are legitimate and currently running.

Create the IAM policy

Create the following AWS IAM policy named teleport-DescribeInstances-policy in your account:

{
   "Version": "2012-10-17",
   "Statement": [
	   {
		   "Effect": "Allow",
		   "Action": "ec2:DescribeInstances",
		   "Resource": "*"
	   }
   ]
}

Attach the IAM policy

If your Teleport Auth Service is running on an EC2 instance and already has an attached "IAM role for Amazon EC2", add the above teleport-DescribeInstances-policy to the existing role. If the instance does not already have an attached role, create an IAM role with the above policy and attach it to your EC2 instance running the Teleport Auth Service.

If you are running your Teleport Auth Service outside of AWS you can attach the teleport-DescribeInstances-policy directly to an IAM user which Teleport will use to authenticate.

You can provide the IAM credentials to Teleport through a shared configuration file or environment variables. See Specifying Credentials for details.

Step 2/4. Create the AWS joining token

Configure your Teleport Auth Service with a special dynamic token which will allow services from your AWS account to join your Teleport cluster.

Under the hood, services will prove that they are running in your AWS account by sending a signed EC2 Instance Identity Document which matches an allow rule configured in your AWS joining token.

Create the following token.yaml with an allow rule specifying your AWS account and the AWS regions in which your EC2 instances will run.

# token.yaml
kind: token
version: v2
metadata:
  # the token name is not a secret because instances must prove that they are
  # running in your AWS account to use this token
  name: ec2-token
spec:
  # use the minimal set of roles required (e.g. Node, App, Kube, DB, WindowsDesktop)
  roles: [Node]

  # set the join method allowed for this token
  join_method: ec2

  # aws_iid_ttl is the amount of time after the EC2 instance is launched during
  # which it should be allowed to join the cluster. Use a short TTL to decrease
  # the risk of stolen EC2 Instance Identity Documents being used to join your
  # cluster.
  #
  # When launching your first Teleport process using the EC2 join method, you may need to
  # temporarily configure a higher `aws_iid_ttl` value so that you have time
  # to get Teleport set up and configured. This feature works best once Teleport
  # is configured in an EC2 AMI to start automatically on launch.
  aws_iid_ttl: 5m

  allow:
  - aws_account: "111111111111" # your AWS account ID
    aws_regions: # use the minimal set of AWS regions required
    - us-west-1
    - us-west-2

Run tctl create token.yaml to create the token.

Step 3/4. Configure your services

The EC2 join method can be used for Teleport processes running the SSH, Proxy, Kubernetes, Application, Database, or Windows Desktop Services. The Teleport process should be run directly on an AWS EC2 instance and must have network access to the AWS EC2 IMDSv2 (enabled by default for most EC2 instances).

Configure your Teleport process with a custom teleport.yaml file. Use the join_params section with token_name matching your token created in Step 2 and method: ec2 as shown in the following example config:

# /etc/teleport.yaml
version: v3
teleport:
  join_params:
    token_name: ec2-token
    method: ec2
  proxy_server: https://teleport.example.com:443
ssh_service:
  enabled: yes
auth_service:
  enabled: no
proxy_service:
  enabled: no

Step 4/4. Launch your Teleport process

IMPORTANT

The data directory (/var/lib/teleport by default) must be empty prior to launching the Teleport process. If this Teleport process had previously joined by another method (e.g. token or IAM) the host UUID will not match the expected name (<AWS Account number>-<instance id>) and will not be allowed to join.

Start Teleport on the host and confirm that it is able to connect to and join your cluster. You're all set!

Configuring the EC2 join method for Multiple AWS accounts

In order for Teleport processes to join from EC2 instances in AWS accounts other than the account in which your Teleport Auth Service is running, Teleport must have permissions to assume an IAM role in each of those accounts and call ec2:DescribeInstances in the foreign account.

In each AWS account where your EC2 instances will be running:

1. Create the teleport-DescribeInstances-policy from Step 1.1.

2. Create an IAM role teleport-DescribeInstances-role that can be assumed from the account where your Teleport Auth Service is running.

   Go to the AWS IAM Console, select Create Role, and for "Select type of trusted entity", select "Another AWS account" and enter the AWS Account ID of the account where your Teleport Auth Service is running.

3. Attach the teleport-DescribeInstances-policy to the role.

In the AWS account where your Teleport Auth Service is running:

1. Create an IAM policy named teleport-AssumeRole-policy with an AssumeRole statement for each foreign account:

{
   "Version": "2012-10-17",
   "Statement": [
        {
            "Effect": "Allow",
            "Action": "sts:AssumeRole",
            "Resource": "arn:aws:iam::222222222222:role/teleport-DescribeInstances-role"
        },
        {
            "Effect": "Allow",
            "Action": "sts:AssumeRole",
            "Resource": "arn:aws:iam::333333333333:role/teleport-DescribeInstances-role"
        }
   ]
}

1. Attach this teleport-AssumeRole-policy to the IAM role your Teleport Auth Service has credentials for, see Step 1.2.

When creating the AWS joining token, include an allow rule for each foreign account and specify the AWS ARN for the foreign teleport-DescribeInstances-role.

# token.yaml
kind: token
version: v2
metadata:
  name: ec2-multiaccount-token
spec:
  roles: [Node]
  aws_iid_ttl: 5m
  allow:
  - aws_account: "222222222222"
    aws_regions:
    - us-west-1
    - us-west-2
    aws_role: "arn:aws:iam::222222222222:role/teleport-DescribeInstances-role"
  - aws_account: "333333333333"
    aws_regions:
    - us-west-1
    - us-west-2
    aws_role: "arn:aws:iam::333333333333:role/teleport-DescribeInstances-role"