Create a token for Vault with Consul storage backend

This topic describes how to create a token for Vault’s Consul storage backend.

Introduction

If you are using Vault to manage secrets in your infrastructure, you can configure Vault to use Consul's key/value (KV) store as backend storage to persist Vault's data. Refer to the Consul KV documentation and the Vault storage documentation for additional information.

Requirements

Core ACL functionality is available in all versions of Consul.

The Vault Consul storage backend must present a token linked to policies that grant the following permissions:

• agent:read: Provides KV visibility to all agents
• key:write: Enables writing to the KV store
• service:write: Enables the Vault service to register into the catalog
• session:write: Enables the agent to initialize a new session

Authentication

You must provide an ACL token linked to a policy with acl:write permissions to create and modify ACL tokens and policies using the CLI or API.

You can provide the token manually using the -token option on the command line, but we recommend setting the CONSUL_HTTP_TOKEN environment variable to simplify your workflow:

$ export CONSUL_HTTP_TOKEN=<acl-token-secret-id>

The Consul CLI automatically reads the CONSUL_HTTP_TOKEN environment variable so that you do not have to pass the token to every Consul CLI command.

To authenticate calls to the Consul HTTP API, you must provide the token in the X-Consul-Token header for each call:

$ curl --header "X-Consul-Token: $CONSUL_HTTP_TOKEN" ...

To learn about alternative ways to authenticate, refer to the following documentation:

• CLI Authentication
• API Authentication

Create a token linked to a policy

To create a token for Vault’s Consul storage backend, you must define a policy, register the policy with Consul, and link the policy to a token.

Define a policy

You can send policy definitions as command line or API arguments or define them in an external HCL or JSON file. Refer to ACL Rules for details about all of the rules you can use in your policies.

The following example policy is defined in a file. The policy grants the appropriate permissions to enable Vault to register as a service named vault and provides access to the vault/ path in Consul's KV store.

agent_prefix "" {
  policy = "read"
}
key_prefix "vault/" {
  policy = "write"
}
service "vault" {
  policy = "write"
}
session_prefix "" {
  policy = "write"
}

{
  "agent_prefix": {
    "": [{
      "policy": "read"
    }]
  },
  "key_prefix": {
    "vault/": [{
      "policy": "write"
    }]
  },
  "service": {
    "vault": [{
      "policy": "write"
    }]
  },
  "session_prefix": {
    "": [{
      "policy": "write"
    }]
  }
}

Register the policy with Consul

After defining the policy, you can register the policy with Consul using the command line or API endpoint.

$ consul acl policy create -partition "default" -namespace "default" \
  -name vault-storage-backend -rules @vault-storage-backend.hcl \
  -description "Policy for the Vault Consul storage backend"

$ curl --request PUT http://127.0.0.1:8500/v1/acl/policy \
  --header "X-Consul-Token: $CONSUL_HTTP_TOKEN" \
  --data '{
  "Name": "vault-storage-backend",
  "Description": "Policy for the Vault Consul storage backend",
  "Rules": "agent_prefix \"\" {\n  policy = \"read\"\n}\nkey_prefix \"vault/\" {\n  policy = \"write\"\n}\nservice \"vault\" {\n  policy = \"write\"\n}\nsession_prefix \"\" {\n  policy = \"write\"\n}\n"
}'

Link the policy to a token

After registering the policy into Consul, you can create and link tokens using the Consul command line or API endpoint. You can also enable Consul to dynamically create tokens from trusted external systems using an auth method.

$ consul acl token create \
    -description "Token for the Vault Consul storage backend" \
    -policy-name "vault-storage-backend"

$ curl --request PUT http://127.0.0.1:8500/v1/acl/token \
  --header "X-Consul-Token: $CONSUL_HTTP_TOKEN" \
  --data '{
  "Policies": [
    {
      "Name": "vault-storage-backend"
    }
  ]
}'