threshold/website/content/docs/configuration/worker/kms-worker.mdx

---
layout: docs
page_title: KMS worker configuration
description: |-
  KMS worker-specific parameters.
---

# KMS worker configuration

This page describes configuration for workers that authenticate to upstreams
using a shared KMS. This mechanism auto-registers the worker in addition to
authenticating it, and does not require on-disk storage for credentials since
each time it connects it reauthenticates using the trusted KMS.

~> If using 0.13+ workers with pre-0.13 controllers you _must_ set the
`use_deprecated_kms_auth_method` value to true. Additionally, a worker
registered using this method _against a pre-0.13 controller_ will only be able
to register directly to a controller, and cannot be used as part of multi-hop or
Vault private access capabilities.

KMS Workers require a `name` field. This specifies a unique name of this worker
within the Boundary cluster and _must be unique across workers_. The `name`
value can be:
- a direct name string (must be all lowercase)
- a reference to a file on disk (`file://`) from which the name is read
- an env var (`env://`) from which the name is read.

KMS Workers accept an optional `description` field. The `description` value can
be:
- a direct description string
- a reference to a file on disk (`file://`) from which the name is read
- an env var (`env://`) from which the name is read.

```hcl
worker {
  name = "example-worker"
  description = "An example worker"
  public_addr = "5.1.23.198"
  # Uncomment if using 0.13 worker against pre-0.13 controller
  # use_deprecated_kms_auth_method = true
}
```

KMS Workers also require a KMS block designated for `worker-auth`. This is the
KMS configuration for authentication between the workers and controllers and
must be present. Example (not safe for production!):

```hcl
kms "aead" {
	purpose = "worker-auth"
	aead_type = "aes-gcm"
	key = "X+IJMVT6OnsrIR6G/9OTcJSX+lM9FSPN"
	key_id = "global_worker-auth"
}
```

The upstream controller or worker must have a `kms` block that references the
same key and purpose. (If both a controller and worker are running as the same
server process only one stanza is needed.) It is also possible to specify a
`kms` block with the `downstream-worker-auth` purpose. If specified, this will
be a separate KMS that can be used for authenticating new downstream nodes.
Blocks with this purpose can be specified multiple times. This allows a single
upstream node to authenticate with one key to its own upstream (via the
`worker-auth` purpose) and then serve as an authenticating upstream to nodes
across various networks, each with their own separate KMS system or key:

```hcl
kms "aead" {
	purpose = "downstream-worker-auth"
	aead_type = "aes-gcm"
	key = "XthZVtFtBD1Bw1XwAWhZKVrIwRhR7HcZ"
	key_id = "iot-nodes-auth"
}

kms "aead" {
	purpose = "downstream-worker-auth"
	aead_type = "aes-gcm"
	key = "OLFhJNbEb3umRjdhY15QKNEmNXokY1Iq"
	key_id = "production-nodes-auth"
}
```

In the examples above we are encoding key bytes directly in the configuration
file. This is because we are using the `aead` method where you directly supply a
key; in production you'd want to use a KMS such as AWS KMS, GCP CKMS, Azure
KeyVault, or HashiCorp Vault. For a complete guide to all available KMS types,
see our [KMS documentation](/boundary/docs/configuration/kms).

## Complete configuration example

```hcl
listener "tcp" {
	purpose = "proxy"
	tls_disable = true
	address = "127.0.0.1"
}

worker {
  # Name attr must be unique across workers
  name = "demo-worker-1"
  description = "A default worker created for demonstration"

  # Workers must be able to reach upstreams on :9201
  initial_upstreams = [
    "10.0.0.1",
    "10.0.0.2",
    "10.0.0.3",
  ]

  public_addr = "myhost.mycompany.com"

  tags {
    type   = ["prod", "webservers"]
    region = ["us-east-1"]
  }

  # use_deprecated_kms_auth_method = true
}

# must be same key as used on controller config
kms "aead" {
	purpose = "worker-auth"
	aead_type = "aes-gcm"
	key = "X+IJMVT6OnsrIR6G/9OTcJSX+lM9FSPN"
	key_id = "global_worker-auth"
}
```

[`initial_upstreams`](/boundary/docs/configuration/worker/overview#initial_upstreams)
are used to connect to upstream Boundary clusters.

## Resources

For more on how `tags{}` in the above configuration are used to facilitate
routing to the correct target, refer to the [Worker
Tags](/boundary/docs/concepts/filtering/worker-tags) page.