open-vault/website/source/docs/auth/approle.html.md

layout	page_title	sidebar_current	description
docs	Auth Backend: AppRole	docs-auth-approle	The AppRole backend allows machines and services to authenticate with Vault.

Auth Backend: AppRole

This backend allows machines and services (apps) to authenticate with Vault via a series of administratively defined roles: AppRoles. The open design of AppRole enables a varied set of workflows and configurations to handle large numbers of apps and their needs. This backend is oriented to automated workflows, and is the successor to the App-ID backend.

AppRoles

An AppRole represents a set of Vault policies and login constraints that must be met to receive a token with those policies. The scope can be as narrow or broad as desired -- an AppRole can be created for a particular machine, or even a particular user on that machine, or a service spread across machines. The credentials required for successful login depend upon the constraints set on the AppRole associated with the credentials.

Credentials/Constraints

RoleID

RoleID is an identifier that selects the AppRole against which the other credentials are evaluated. When authenticating against this backend's login endpoint, the RoleID is a required argument (via role_id) at all times. By default, RoleIDs are unique UUIDs, which allow them to serve as secondary secrets to the other credential information. However, they can be set to particular values to match introspected information by the client (for instance, the client's domain name).

SecretID

SecretID is a credential that is required by default for any login (via secret_id) and is intended to always be secret. (For advanced usage, requiring a SecretID can be disabled via an AppRole's bind_secret_id parameter, allowing machines with only knowledge of the RoleID, or matching other set constraints, to fetch a token). SecretIDs can be created against an AppRole either via generation of a 128-bit purely random UUID by the role itself (Pull mode) or via specific, custom values (Push mode). Similarly to tokens, SecretIDs have properties like usage-limit, TTLs and expirations.

Pull And Push SecretID Modes

If the SecretID used for login is fetched from an AppRole, this is operating in Pull mode. If a "custom" SecretID is set against an AppRole by the client, it is referred to as a Push mode. Push mode mimics the behavior of the deprecated App-ID backend; however, in most cases Pull mode is the better approach. The reason is that Push mode requires some other system to have knowledge of the full set of client credentials (RoleID and SecretID) in order to create the entry, even if these are then distributed via different paths. However, in Pull mode, even though the RoleID must be known in order to distribute it to the client, the SecretID can be kept confidential from all parties except for the final authenticating client by using Response Wrapping.

Push mode is available for App-ID workflow compatibility, which in some specific cases is preferable, but in most cases Pull mode is more secure and should be preferred.

Further Constraints

role_id is a required credential at the login endpoint. AppRole pointed to by the role_id will have constraints set on it. This dictates other required credentials for login. The bind_secret_id constraint requires secret_id to be presented at the login endpoint. Going forward, this backend can support more constraint parameters to support varied set of Apps. Some constraints will not require a credential, but still enforce constraints for login. For example, bound_cidr_list will only allow requests coming from IP addresses belonging to configured CIDR blocks on the AppRole.

Comparison to Tokens

Authentication

Via the CLI

Enable AppRole authentication

$ vault auth-enable approle

Create a role

$ vault write auth/approle/role/testrole secret_id_ttl=10m token_num_uses=10 token_ttl=20m token_max_ttl=30m secret_id_num_uses=40

Fetch the RoleID of the AppRole

$ vault read auth/approle/role/testrole/role-id

role_id     db02de05-fa39-4855-059b-67221c5c2f63

Get a SecretID issued against the AppRole

$ vault write -f auth/approle/role/testrole/secret-id

secret_id               6a174c20-f6de-a53c-74d2-6018fcceff64
secret_id_accessor      c454f7e5-996e-7230-6074-6ef26b7bcf86

Login to get a Vault Token

$ vault write auth/approle/login role_id=db02de05-fa39-4855-059b-67221c5c2f63 secret_id=6a174c20-f6de-a53c-74d2-6018fcceff64

token           65b74ffd-842c-fd43-1386-f7d7006e520a
token_accessor  3c29bc22-5c72-11a6-f778-2bc8f48cea0e
token_duration  20m0s
token_renewable true
token_policies  [default]

Via the API

Enable the AppRole authentication.

$ curl -X POST -H "X-Vault-Token:$VAULT_TOKEN" -d '{"type":"approle"}' http://127.0.0.1:8200/v1/sys/auth/approle

Create an AppRole with desired set of policies.

$ curl -X POST -H "X-Vault-Token:$VAULT_TOKEN" -d '{"policies":"dev-policy,test-policy"}' http://127.0.0.1:8200/v1/auth/approle/role/testrole

Fetch the identifier of the role.

$ curl -X GET -H "X-Vault-Token:$VAULT_TOKEN" http://127.0.0.1:8200/v1/auth/approle/role/testrole/role-id | jq .

{
  "auth": null,
  "warnings": null,
  "wrap_info": null,
  "data": {
    "role_id": "988a9dfd-ea69-4a53-6cb6-9d6b86474bba"
  },
  "lease_duration": 0,
  "renewable": false,
  "lease_id": "",
  "request_id": "ef5c9b3f-e15e-0527-5457-79b4ecfe7b60"
}

Create a new secret identifier under the role.

$ curl -X POST -H "X-Vault-Token:$VAULT_TOKEN" http://127.0.0.1:8200/v1/auth/approle/role/testrole/secret-id | jq .

{
  "auth": null,
  "warnings": null,
  "wrap_info": null,
  "data": {
    "secret_id_accessor": "45946873-1d96-a9d4-678c-9229f74386a5",
    "secret_id": "37b74931-c4cd-d49a-9246-ccc62d682a25"
  },
  "lease_duration": 0,
  "renewable": false,
  "lease_id": "",
  "request_id": "c98fa1c2-7565-fd45-d9de-0b43c307f2aa"
}

Perform the login operation to fetch a new Vault token.

$ curl -X POST \
     -d '{"role_id":"988a9dfd-ea69-4a53-6cb6-9d6b86474bba","secret_id":"37b74931-c4cd-d49a-9246-ccc62d682a25"}' \
     http://127.0.0.1:8200/v1/auth/approle/login | jq .

{
  "auth": {
    "renewable": true,
    "lease_duration": 2764800,
    "metadata": {},
    "policies": [
      "default",
      "dev-policy",
      "test-policy"
    ],
    "accessor": "5d7fb475-07cb-4060-c2de-1ca3fcbf0c56",
    "client_token": "98a4c7ab-b1fe-361b-ba0b-e307aacfd587"
  },
  "warnings": null,
  "wrap_info": null,
  "data": null,
  "lease_duration": 0,
  "renewable": false,
  "lease_id": "",
  "request_id": "988fb8db-ce3b-0167-0ac7-1a568b902d75"
}

API

The AppRole authentication backend has a full HTTP API. Please see the AppRole API for more details.