Consul Secrets Engine

The Consul secrets engine generates Consul API tokens dynamically based on Consul ACL policies.

Setup

Most secrets engines must be configured in advance before they can perform their functions. These steps are usually completed by an operator or configuration management tool.

Enable the Consul secrets engine:
```
$ vault secrets enable consul
Success! Enabled the consul secrets engine at: consul/
```
By default, the secrets engine will mount at the name of the engine. To enable the secrets engine at a different path, use the -path argument.

In Consul versions below 1.4, acquire a management token from Consul, using the acl_master_token from your Consul configuration file or another management token:

$ curl \
    --header "X-Consul-Token: my-management-token" \
    --request PUT \
    --data '{"Name": "sample", "Type": "management"}' \
    https://consul.rocks/v1/acl/create

Vault must have a management type token so that it can create and revoke ACL tokens. The response will return a new token:

{
  "ID": "7652ba4c-0f6e-8e75-5724-5e083d72cfe4"
}

For Consul 1.4 and above, use the command line to generate a token with the appropriate policy:

$ CONSUL_HTTP_TOKEN=d54fe46a-1f57-a589-3583-6b78e334b03b consul acl token create -policy-name=global-management
AccessorID:   865dc5e9-e585-3180-7b49-4ddc0fc45135
SecretID:     ef35f0f1-885b-0cab-573c-7c91b65a7a7e
Description:
Local:        false
Create Time:  2018-10-22 17:40:24.128188 -0700 PDT
Policies:
    00000000-0000-0000-0000-000000000001 - global-management

Configure Vault to connect and authenticate to Consul:

$ vault write consul/config/access \
    address=127.0.0.1:8500 \
    token=7652ba4c-0f6e-8e75-5724-5e083d72cfe4
Success! Data written to: consul/config/access

Configure a role that maps a name in Vault to a Consul ACL policy. Depending on your Consul version, you will either provide a policy document and a token_type, or a set of policies. When users generate credentials, they are generated against this role. For Consul versions below 1.4:
```
$ vault write consul/roles/my-role policy=$(base64 <<< 'key "" { policy = "read" }')
Success! Data written to: consul/roles/my-role
```
The policy must be base64-encoded. The policy language is documented by Consul.
For Consul versions 1.4 and above, generate a policy in Consul, and proceed to link it to the role:
```
$ vault write consul/roles/my-role policies=readonly
Success! Data written to: consul/roles/my-role
```
Token lease duration: If you do not specify a value for ttl (or lease for Consul versions below 1.4) the tokens created using Vault's Consul secrets engine are created with a Time To Live (TTL) of 30 days. You can change the lease duration by passing -ttl=<duration> to the command above with "duration" being a string with a time suffix like "30s" or "1h".

Usage

After the secrets engine is configured and a user/machine has a Vault token with the proper permission, it can generate credentials.

Generate a new credential by reading from the /creds endpoint with the name of the role:

$ vault read consul/creds/my-role
Key                Value
---                -----
lease_id           consul/creds/my-role/b2469121-f55f-53c5-89af-a3ba52b1d6d8
lease_duration     768h
lease_renewable    true
token              642783bf-1540-526f-d4de-fe1ac1aed6f0

When using Consul 1.4, the response will include the accessor for the token

$ vault read consul/creds/my-role
Key                Value
---                -----
lease_id           consul/creds/my-role/7miMPnYaBCaVWDS9clNE0Nv3
lease_duration     768h
lease_renewable    true
accessor           6d5a0348-dffe-e87b-4266-2bec03800abb
token              bc7a42c0-9c59-23b4-8a09-7173c474dc42

Expired token rotation: Once a token's TTL expires, then Consul operations will no longer be allowed with it. This requires you to have an external process to rotate tokens. At this time, the recommended approach for operators is to rotate the tokens manually by creating a new token using the vault read consul/creds/my-role command. Once the token is synchronized with Consul, apply the token to the agents using the Consul API or CLI.

Learn

Refer to Administer Consul Access Control Tokens with Vault for a step-by-step tutorial.

API

The Consul secrets engine has a full HTTP API. Please see the Consul secrets engine API for more details.