» 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 configuration management.

$ vault secrets enable -path=aws aws
Success! Enabled the aws secrets engine at: aws/

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

» Configuring the AWS Secrets Engine

After enabling the AWS secrets engine, you must configure it to authenticate and communicate with AWS. This requires privileged account credentials. If you are unfamiliar with AWS, use your root account keys.

$ vault write aws/config/root \
    access_key=AKIAI4SGLQPBX6CSENIQ \
    secret_key=z1Pdn06b3TnpG+9Gwj3ppPSOlAsu08Qw99PUW+eB
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.

» Creating a Role

The next step is to configure a "role". A "role" in Vault is a human-friendly identifier to an action. Think of it as a symlink.

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 - roles map your configuration options to those API calls.

For example, here is an IAM policy that enables all actions on EC2. When Vault generates an access key, it will automatically attach this policy. The generated access key will have full access to EC2 (as dictated by this policy), but not IAM or other AWS services. If you are not familiar with AWS' IAM policies, that is okay - just use this one for now.

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

As mentioned above, we need to map this policy document to a named role. To do that, write to aws/roles/:name:

$ vault write aws/roles/my-role policy=-<<EOF
{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Sid": "Stmt1426528957000",
      "Effect": "Allow",
      "Action": [
        "ec2:*"
      ],
      "Resource": [
        "*"
      ]
    }
  ]
}
EOF
Success! Data written to: aws/roles/my-role

Again, we're using a special path here aws/roles/:name to write an IAM policy to Vault. We just told Vault:

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

» Generating the Secret

Now that the AWS secrets engine is enabled and configured with a role, we 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.

Take careful note of the lease_id field in the output. This value is used for renewal, revocation, and inspection. Copy this lease_id to your clipboard. Note that the lease_id is the full path, not just the UUID at the end.

» Revoking the Secret

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

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

$ 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.

With such easy dynamic creation and revocation, you can hopefully begin to see how easy it is to work with dynamic secrets and ensure they only exist for the duration that they are needed.

» Next

On this page we experienced our first dynamic secret, and we also saw the revocation system in action. Dynamic secrets are incredibly powerful. As time goes on, we expect that more systems will support some sort of API to create access credentials, and Vault will be ready to get the most value out of this practice.

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