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AppRole auth method

The approle auth method allows machines or apps to authenticate with OpenBao-defined roles. The open design of AppRole enables a varied set of workflows and configurations to handle large numbers of apps. This auth method is oriented to automated workflows (machines and services), and is less useful for human operators.

An "AppRole" represents a set of OpenBao 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.

Authentication​

Via the CLI​

The default path is /approle. If this auth method was enabled at a different path, specify auth/my-path/login instead.

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

Key                Value
---                -----
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​

The default endpoint is auth/approle/login. If this auth method was enabled at a different path, use that value instead of approle.

$ curl \
    --request POST \
    --data '{"role_id":"988a9df-...","secret_id":"37b74931..."}' \
    http://127.0.0.1:8200/v1/auth/approle/login

The response will contain the token at auth.client_token:

{
  "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"
  }
}
info

Application Integration: See the Code Example section for a code snippet demonstrating the authentication with OpenBao using the AppRole auth method.

Configuration​

Auth methods must be configured in advance before users or machines can authenticate. These steps are usually completed by an operator or configuration management tool.

Via the CLI​

  1. Enable the AppRole auth method:

    $ bao auth enable approle

  2. Create a named role:

    $ bao write auth/approle/role/my-role \
        secret_id_ttl=10m \
        token_num_uses=10 \
        token_ttl=20m \
        token_max_ttl=30m \
        secret_id_num_uses=40
warning

Note: If the token issued by your approle needs the ability to create child tokens, you will need to set token_num_uses to 0.

For the complete list of configuration options, please see the API documentation.

  1. Fetch the RoleID of the AppRole:

    $ bao read auth/approle/role/my-role/role-id
    role_id     db02de05-fa39-4855-059b-67221c5c2f63

  2. Get a SecretID issued against the AppRole:

    $ bao write -f auth/approle/role/my-role/secret-id
    secret_id               6a174c20-f6de-a53c-74d2-6018fcceff64
    secret_id_accessor      c454f7e5-996e-7230-6074-6ef26b7bcf86
    secret_id_ttl           10m
    secret_id_num_uses      40

Via the API​

  1. Enable the AppRole auth method:

    $ curl \
        --header "X-Vault-Token: ..." \
        --request POST \
        --data '{"type": "approle"}' \
        http://127.0.0.1:8200/v1/sys/auth/approle

  2. Create an AppRole with desired set of policies:

    $ curl \
        --header "X-Vault-Token: ..." \
        --request POST \
        --data '{"policies": "dev-policy,test-policy"}' \
        http://127.0.0.1:8200/v1/auth/approle/role/my-role

  3. Fetch the identifier of the role:

    $ curl \
        --header "X-Vault-Token: ..." \
        http://127.0.0.1:8200/v1/auth/approle/role/my-role/role-id

    The response will look like:

    {
      "data": {
        "role_id": "988a9dfd-ea69-4a53-6cb6-9d6b86474bba"
      }
    }

  4. Create a new secret identifier under the role:

    $ curl \
        --header "X-Vault-Token: ..." \
        --request POST \
         http://127.0.0.1:8200/v1/auth/approle/role/my-role/secret-id

    The response will look like:

    {
      "data": {
        "secret_id_accessor": "45946873-1d96-a9d4-678c-9229f74386a5",
        "secret_id": "37b74931-c4cd-d49a-9246-ccc62d682a25",
        "secret_id_ttl": 600,
        "secret_id_num_uses": 40
      }
    }

Credentials/Constraints​

RoleID​

RoleID is an identifier that selects the AppRole against which the other credentials are evaluated. When authenticating against this auth method'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 auth method; 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 auth method 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, secret_id_bound_cidrs will only allow logins coming from IP addresses belonging to configured CIDR blocks on the AppRole.

User lockout​

If a user provides bad credentials several times in quick succession, OpenBao will stop trying to validate their credentials for a while, instead returning immediately with a permission denied error. We call this behavior "user lockout". The time for which a user will be locked out is called “lockout duration”. The user will be able to login after the lockout duration has passed. The number of failed login attempts after which the user is locked out is called “lockout threshold”. The lockout threshold counter is reset to zero after a few minutes without login attempts, or upon a successful login attempt. The duration after which the counter will be reset to zero after no login attempts is called "lockout counter reset". This can defeat both automated and targeted requests i.e, user-based password guessing attacks as well as automated attacks.

The user lockout feature is enabled by default. The default values for "lockout threshold" is 5 attempts, "lockout duration" is 15 minutes, "lockout counter reset" is 15 minutes.

The user lockout feature can be disabled as follows:

  • It can be disabled globally using environment variable VAULT_DISABLE_USER_LOCKOUT.
  • It can be disabled for all supported auth methods (ldap, userpass and approle) or a specific supported auth method using the disable_lockout parameter within user_lockout stanza in configuration file. Please see user lockout configuration for more details.
  • It can be disabled for a specific auth mount using "auth tune". Please see auth tune command or auth tune api for more details.
warning

NOTE: This feature is only supported by the userpass, ldap, and approle auth methods.

API​

The AppRole auth method has a full HTTP API. Please see the AppRole API for more details.

Code example​

The following example demonstrates AppRole authentication with response wrapping.

package main

import (
	"context"
	"fmt"
	"os"

	openbao "github.com/openbao/openbao/api"
	auth "github.com/openbao/openbao/api/auth/approle"
)

// Fetches a key-value secret (kv-v2) after authenticating via AppRole.
func getSecretWithAppRole() (string, error) {
	config := openbao.DefaultConfig() // modify for more granular configuration

	client, err := openbao.NewClient(config)
	if err != nil {
		return "", fmt.Errorf("unable to initialize OpenBao client: %w", err)
	}

	// A combination of a Role ID and Secret ID is required to log in to OpenBao
	// with an AppRole.
	// First, let's get the role ID given to us by our OpenBao administrator.
	roleID := os.Getenv("APPROLE_ROLE_ID")
	if roleID == "" {
		return "", fmt.Errorf("no role ID was provided in APPROLE_ROLE_ID env var")
	}

	// The Secret ID is a value that needs to be protected, so instead of the
	// app having knowledge of the secret ID directly, we have a trusted orchestrator (https://learn.hashicorp.com/tutorials/vault/secure-introduction?in=vault/app-integration#trusted-orchestrator)
	// give the app access to a short-lived response-wrapping token (https://www.vaultproject.io/docs/concepts/response-wrapping).
	// Read more at: https://learn.hashicorp.com/tutorials/vault/approle-best-practices?in=vault/auth-methods#secretid-delivery-best-practices
	secretID := &auth.SecretID{FromFile: "path/to/wrapping-token"}

	appRoleAuth, err := auth.NewAppRoleAuth(
		roleID,
		secretID,
		auth.WithWrappingToken(), // Only required if the secret ID is response-wrapped.
	)
	if err != nil {
		return "", fmt.Errorf("unable to initialize AppRole auth method: %w", err)
	}

	authInfo, err := client.Auth().Login(context.Background(), appRoleAuth)
	if err != nil {
		return "", fmt.Errorf("unable to login to AppRole auth method: %w", err)
	}
	if authInfo == nil {
		return "", fmt.Errorf("no auth info was returned after login")
	}

	// get secret from the default mount path for KV v2 in dev mode, "secret"
	secret, err := client.KVv2("secret").Get(context.Background(), "creds")
	if err != nil {
		return "", fmt.Errorf("unable to read secret: %w", err)
	}

	// data map can contain more than one key-value pair,
	// in this case we're just grabbing one of them
	value, ok := secret.Data["password"].(string)
	if !ok {
		return "", fmt.Errorf("value type assertion failed: %T %#v", secret.Data["password"], secret.Data["password"])
	}

	return value, nil
}