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Dynamic Secrets - AWS

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.

Note: Before starting this page, please register for an AWS account. You won't be using any features that cost money, so you shouldn't be charged for anything. However, we are not responsible for any charges you may incur.

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

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.

In the terminal that is running your Vault server, set an AWS_ACCESS_KEY_ID environment variable to hold your AWS access key ID.

export AWS_ACCESS_KEY_ID=

Set an AWS_SECRET_ACCESS_KEY environment variable to hold your AWS secret access key.

export AWS_SECRET_ACCESS_KEY=

If you are unfamiliar with AWS, use your root account keys. If you don't have access to the root account keys, here is a list of the required IAM permissions that Vault will need in order to perform the actions on the rest of this page.

Warning: Do not use your root account keys in production. This is a getting started tutorial and is not a best practices tutorial for production installations.

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": ["*"]
    }
  ]
}

NOTE: If you are not familiar with AWS' IAM policies, that is okay - just use this one for now.

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

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

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.