Dynamic secrets

Now that you've experimented with the kv secrets engine, it is time to explore another feature of Vault: dynamic secrets.

Unlike the kv secrets where you had to put data into the store yourself, dynamic secrets are generated when they are accessed. Dynamic secrets do not exist until they are read, so there is no risk of someone stealing them or another client using the same secrets. Because Vault has built-in revocation mechanisms, dynamic secrets can be revoked immediately after use, minimizing the amount of time the secret existed.

Enable the AWS secrets engine

Unlike the kv secrets engine which is enabled by default, the AWS secrets engine must be enabled before use. This step is usually done via a configuration management system.

$ vault secrets enable -path=aws aws

Success! Enabled the aws secrets engine at: aws/

The AWS secrets engine is now enabled at aws/. Different secrets engines allow for different behavior. In this case, the AWS secrets engine generates dynamic, on-demand AWS access credentials.

Configure the AWS secrets engine

After enabling the AWS secrets engine, you must configure it to authenticate and communicate with AWS. This requires privileged AWS account credentials.

If authenticating with an IAM user, set your AWS Access Key as an environment variable in the terminal that is running your Vault server:

$ export AWS_ACCESS_KEY_ID=<aws_access_key_id>

Next, set your secret key.

$ export AWS_SECRET_ACCESS_KEY=<aws_secret_key>

Your keys must have the IAM permissions listed in the Vault documentation to perform the actions on the rest of this page.

Configure the AWS secrets engine.

$ vault write aws/config/root \
    access_key=$AWS_ACCESS_KEY_ID \
    secret_key=$AWS_SECRET_ACCESS_KEY \
    region=us-east-1

Output:

Success! Data written to: aws/config/root

These credentials are now stored in this AWS secrets engine. The engine will use these credentials when communicating with AWS in future requests.

Create a role

The next step is to configure a role. Vault knows how to create an IAM user via the AWS API, but it does not know what permissions, groups, and policies you want to attach to that user. This is where roles come in - a role in Vault is a human-friendly identifier to an action.

For example, here is an IAM policy that enables all actions on EC2, but not IAM or other AWS services.

{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Sid": "Stmt1426528957000",
      "Effect": "Allow",
      "Action": ["ec2:*"],
      "Resource": ["*"]
    }
  ]
}

You need to map this policy document to a named role. To do that, write to aws/roles/:name where :name is your unique name that describes the role (such as aws/roles/my-role):

$ vault write aws/roles/my-role \
        credential_type=iam_user \
        policy_document=-<<EOF
{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Sid": "Stmt1426528957000",
      "Effect": "Allow",
      "Action": [
        "ec2:*"
      ],
      "Resource": [
        "*"
      ]
    }
  ]
}
EOF

You just told Vault:

When I ask for a credential for "my-role", create it and attach the IAM policy { "Version": "2012..." }.

Generate the secret

Now that the AWS secrets engine is enabled and configured with a role, you can ask Vault to generate an access key pair for that role by reading from aws/creds/:name, where :name corresponds to the name of an existing role:

$ vault read aws/creds/my-role
Key                Value
---                -----
lease_id           aws/creds/my-role/0bce0782-32aa-25ec-f61d-c026ff22106e
lease_duration     768h
lease_renewable    true
access_key         AKIAJELUDIANQGRXCTZQ
secret_key         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
security_token     <nil>

Success! The access and secret key can now be used to perform any EC2 operations within AWS. Notice that these keys are new, they are not the keys you entered earlier. If you were to run the command a second time, you would get a new access key pair. Each time you read from aws/creds/:name, Vault will connect to AWS and generate a new IAM user and key pair.

Copy the full path of this lease_id value found in the output. This value is used for renewal, revocation, and inspection.

Revoke the secret

Vault will automatically revoke this credential after 768 hours (see lease_duration in the output), but perhaps you want to revoke it early. Once the secret is revoked, the access keys are no longer valid.

To revoke the secret, use vault lease revoke with the lease ID that was outputted from vault read when you ran it.

Example:

$ vault lease revoke aws/creds/my-role/0bce0782-32aa-25ec-f61d-c026ff22106
Success! Revoked lease: aws/creds/my-role/0bce0782-32aa-25ec-f61d-c026ff22106e

Done! If you login to your AWS account, you will see that no IAM users exist. If you try to use the access keys that were generated, you will find that they no longer work.

Next

In this tutorial, you experienced your first dynamic secret and you also saw the revocation system in action. Dynamic secrets are incredibly powerful. The Dynamic Secrets: Database Secrets Engine tutorial demonstrates another dynamic secrets engine.

Before going further, you're going to take a quick detour to learn about the built-in help system.