Developer

AppRole Pull Authentication

Before a client can interact with Vault, it must authenticate against an auth method to acquire a token. This token has policies attached so that the behavior of the client can be governed.

Since tokens are the core method for authentication within Vault, there is a token auth method (often referred to as token store). This is a special auth method responsible for creating and storing tokens.

» Auth Methods

Auth methods perform authentication to verify the user or machine-supplied information. Some of the supported auth methods are targeted towards users while others are targeted toward machines or apps. For example, LDAP auth method enables user authentication using an existing LDAP server while AppRole auth method is recommended for machines or apps.

The Getting Started guide walks you through how to enable the GitHub auth method for user authentication.

This introductory guide focuses on generating tokens for machines or apps by enabling the AppRole auth method.

» Personas

The end-to-end scenario described in this guide involves two personas:

  • admin with privileged permissions to configure an auth method
  • app is the consumer of secrets stored in Vault

» Challenge

Think of a scenario where a DevOps team wants to configure Jenkins to read secrets from Vault so that it can inject the secrets to an app's environment variables (e.g. MYSQL_DB_HOST) at deployment time.

Instead of hardcoding secrets in each build script as plain text, Jenkins retrieves secrets from Vault.

As a user, you can authenticate with Vault using your LDAP credentials, and Vault generates a token. This token has policies granting you permission to perform the appropriate operations.

How can a Jenkins server programmatically request a token so that it can read secrets from Vault?

» Solution

Enable AppRole auth method so that the Jenkins server can obtain a Vault token with appropriate policies attached. Since each AppRole has attached policies, you can write fine-grained policies limiting which app can access which path.

» Prerequisites

To perform the tasks described in this guide, you need to have a Vault environment. Refer to the Getting Started guide to install Vault. Make sure that your Vault server has been initialized and unsealed.

» Policy requirements

To perform all tasks demonstrated in this guide, your policy must include the following permissions:

# Mount the AppRole auth method
path "sys/auth/approle" {
  capabilities = [ "create", "read", "update", "delete", "sudo" ]
}

# Configure the AppRole auth method
path "sys/auth/approle/*" {
  capabilities = [ "create", "read", "update", "delete" ]
}

# Create and manage roles
path "auth/approle/*" {
  capabilities = [ "create", "read", "update", "delete", "list" ]
}

# Write ACL policies
path "sys/policy/*" {
  capabilities = [ "create", "read", "update", "delete", "list" ]
}

# Write test data
# Set the path to "secret/data/mysql/*" if you are running `kv-v2`
path "secret/mysql/*" {
  capabilities = [ "create", "read", "update", "delete", "list" ]
}

If you are not familiar with policies, complete the policies guide.

» Steps

AppRole is an authentication mechanism within Vault to allow machines or apps to acquire a token to interact with Vault. It uses Role ID and Secret ID for login.

The basic workflow is: AppRole auth method workflow

In this guide, you are going to perform the following steps:

  1. Enable AppRole auth method
  2. Create a role with policy attached
  3. Get Role ID and Secret ID
  4. Login with Role ID & Secret ID
  5. Read secrets using the AppRole token

Step 1 through 3 need to be performed by an admin user. Step 4 and 5 describe the commands that an app runs to get a token and read secrets from Vault.

» Step 1: Enable AppRole auth method

(Persona: admin)

Like many other auth methods, AppRole must be enabled before it can be used.

» CLI command

Enable approle auth method by executing the following command:

$ vault auth enable approle

» API call using cURL

Enable approle auth method by mounting its endpoint at /sys/auth/approle:

$ curl --header "X-Vault-Token: <TOKEN>" \
       --request POST \
       --data <PARAMETERS> \
       <VAULT_ADDRESS>/v1/sys/auth/approle

Where <TOKEN> is your valid token, and <PARAMETERS> holds configuration parameters of the method.

Example:

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

The above example passes the type (approle) in the request payload at the sys/auth/approle endpoint.

» Step 2: Create a role with policy attached

(Persona: admin)

When you enabled the AppRole auth method, it gets mounted at the /auth/approle path. In this example, you are going to create a role for the app persona (jenkins in our scenario).

The scenario in this guide requires the app to have the following policy (jenkins-pol.hcl):

# Login with AppRole
path "auth/approle/login" {
  capabilities = [ "create", "read" ]
}

# Read test data
# Set the path to "secret/data/mysql/*" if you are running `kv-v2`
path "secret/mysql/*" {
  capabilities = [ "read" ]
}

» CLI command

Before creating a role, create a jenkins policy:

$ vault policy write jenkins jenkins-pol.hcl

The command to create a new AppRole:

$ vault write auth/approle/role/<ROLE_NAME> [parameters]

There are a number of parameters that you can set on a role. If you want to limit the use of the generated secret ID, set secret_id_num_uses or secret_id_ttl parameter values. Similarly, you can specify token_num_uses and token_ttl. You may never want the app token to expire. In such a case, specify the period so that the token generated by this AppRole is a periodic token. To learn more about periodic token, refer to the Tokens guide.

Example:

The following example creates a role named jenkins with jenkins policy attached. (NOTE: This example creates a role operates in pull mode.)

$ vault write auth/approle/role/jenkins policies="jenkins"

# Read the jenkins role
$ vault read auth/approle/role/jenkins

  Key                   Value
  ---                   -----
  bind_secret_id        true
  bound_cidr_list
  period                0
  policies              [jenkins]
  secret_id_num_uses    0
  secret_id_ttl         0
  token_max_ttl         0
  token_num_uses        0
  token_ttl             0
$ vault write auth/approle/role/jenkins policies="jenkins,anotherpolicy"

» API call using cURL

Before creating a role, create jenkins policy:

$ curl --header "X-Vault-Token: ..." --request PUT --data @payload.json \
     http://127.0.0.1:8200/v1/sys/policy/jenkins

$ cat payload.json
{
  "policy": "path \"auth/approle/login\" {  capabilities = [ \"create\", \"read\" ] } ... }"
}

Now, you are ready to create a role.

Example:

The following example creates a role named jenkins with a jenkins policy attached. (NOTE: This example creates a role which operates in pull mode.)

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

There are a number of parameters that you can set on a role. If you want to limit the use of the generated secret ID, set secret_id_num_uses or secret_id_ttl parameter values. Similarly, you can specify token_num_uses and token_ttl. You may never want the app token to expire. In such a case, specify the period so that the token generated by this AppRole is a periodic token. To learn more about periodic tokens, refer to the Tokens guide.

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

To read the Jenkins role you just created:

$ curl --header "X-Vault-Token: ..." --request GET \
        http://127.0.0.1:8200/v1/auth/approle/role/jenkins | jq
{
  "request_id": "b18054ad-1ab5-8d83-eeed-193d97026ee7",
  "lease_id": "",
  "renewable": false,
  "lease_duration": 0,
  "data": {
    "bind_secret_id": true,
    "bound_cidr_list": "",
    "period": 0,
    "policies": [
      "jenkins"
    ],
    "secret_id_num_uses": 0,
    "secret_id_ttl": 0,
    "token_max_ttl": 0,
    "token_num_uses": 0,
    "token_ttl": 0
  },
  "wrap_info": null,
  "warnings": null,
  "auth": null
}

» Step 3: Get Role ID and Secret ID

The Role ID and Secret ID are like a username and password that a machine or app uses to authenticate.

Since the example created a jenkins role which operates in pull mode, Vault will generate the Secret ID. You can set properties such as usage-limit, TTLs, and expirations on the secret IDs to control its lifecycle.

» CLI command

Now, you need to fetch the Role ID and Secret ID of a role.

To read the Role ID:

$ vault read auth/approle/role/<ROLE_NAME>/role-id

To generate a new Secret ID:

$ vault write -f auth/approle/role/<ROLE_NAME>/secret-id

Example:

$ vault read auth/approle/role/jenkins/role-id
  Key       Value
  ---       -----
  role_id   675a50e7-cfe0-be76-e35f-49ec009731ea

$ vault write -f auth/approle/role/jenkins/secret-id
  Key                   Value
  ---                   -----
  secret_id             ed0a642f-2acf-c2da-232f-1b21300d5f29
  secret_id_accessor    a240a31f-270a-4765-64bd-94ba1f65703c

If you specified secret_id_ttl, secret_id_num_uses, or bound_cidr_list on the role in Step 2, the generated secret ID carries out the conditions.

» API call using cURL

To read the Role ID:

$ curl --header "X-Vault-Token:..." \
       --request GET \
       <VAULT_ADDRESS>/v1/auth/approle/role/<ROLE_NAME>/role-id

To generate a new Secret ID:

$ curl --header "X-Vault-Token:..." \
       --request POST \
       --data <PARAMETERS>
       <VAULT_ADDRESS>/v1/auth/approle/role/<ROLE_NAME>/secret-id

You can pass parameters in the request payload, or invoke the API with an empty payload.

Example:

$ curl --header "X-Vault-Token:..." --request GET \
       http://127.0.0.1:8200/v1/auth/approle/role/jenkins/role-id | jq

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

If you specified secret_id_ttl, secret_id_num_uses, or bound_cidr_list on the role in Step 2, the generated secret ID carries out the conditions.

» Step 4: Login with Role ID & Secret ID

(Persona: app)

The client (in this case, Jenkins) uses the role ID and secret ID passed by the admin to authenticate with Vault. If Jenkins did not receive the role ID and/or secret ID, the admin needs to investigate.

» CLI command

To login, use the auth/approle/login endpoint by passing the role ID and secret ID.

Example:

$ vault write auth/approle/login role_id="675a50e7-cfe0-be76-e35f-49ec009731ea" \
  secret_id="ed0a642f-2acf-c2da-232f-1b21300d5f29"

  Key                   Value
  ---                   -----
  token                 eeaf890e-4b0f-a687-4190-c75b1d6d70bc
  token_accessor        fcee5d4e-7281-8bb0-2901-e743c52e0502
  token_duration        768h0m0s
  token_renewable       true
  token_policies        [jenkins]
  token_meta_role_name  "jenkins"

Now you have a client token with default and jenkins policies attached.

» API call using cURL

To login, use the auth/approle/login endpoint by passing the role ID and secret ID in the request payload.

Example:

$ cat payload.json
  {
    "role_id": "675a50e7-cfe0-be76-e35f-49ec009731ea",
    "secret_id": "ed0a642f-2acf-c2da-232f-1b21300d5f29"
  }

$ curl --request POST --data @payload.json http://127.0.0.1:8200/v1/auth/approle/login | jq
{
  "request_id": "fccae32b-1e6a-9a9c-7666-f5cb07805c1e",
  "lease_id": "",
  "renewable": false,
  "lease_duration": 0,
  "data": null,
  "wrap_info": null,
  "warnings": null,
  "auth": {
    "client_token": "3e7dd0ac-8b3e-8f88-bb37-a2890455ca6e",
    "accessor": "375c077e-bf02-a09b-c864-63d7f967e86b",
    "policies": [
      "default",
      "jenkins"
    ],
    "metadata": {
      "role_name": "jenkins"
    },
    "lease_duration": 2764800,
    "renewable": true,
    "entity_id": "54e0b765-6daf-0ff5-70b9-32c0d491f473"
  }
}

Now you have a client token with default and jenkins policies attached.

» Step 5: Read secrets using the AppRole token

(Persona: app)

Once receiving a token from Vault, the client can make future requests using this token.

» CLI command

Example:

You can pass the client_token returned in Step 4 as a part of the CLI command.

$ VAULT_TOKEN=3e7dd0ac-8b3e-8f88-bb37-a2890455ca6e vault kv get secret/mysql/webapp
No value found at secret/mysql/webapp

Or you can first authenticate with Vault using the client_token.

$ vault login 3e7dd0ac-8b3e-8f88-bb37-a2890455ca6e
Successfully authenticated! You are now logged in.
token: 3e7dd0ac-8b3e-8f88-bb37-a2890455ca6e
token_duration: 2762013
token_policies: [default jenkins]

$ vault kv get secret/mysql/webapp
No value found at secret/mysql/webapp

Since there is no value at secret/mysql/webapp, it returns a "no value found" message.

Optional: Using the admin user's token, you can store some secrets in the secret/mysql/webapp path.

$ vault kv put secret/mysql/webapp @mysqldb.txt

$ cat mysqldb.txt
{
  "url": "foo.example.com:35533",
  "db_name": "users",
  "username": "admin",
  "password": "pa$$w0rd"
}

Now, try to read secrets from secret/mysql/webapp using the client_token again. This time, it should return the values you just created.

» API call using cURL

You can now pass the client_token returned in Step 4 in the X-Vault-Token header.

Example:

$ curl --header "X-Vault-Token: 3e7dd0ac-8b3e-8f88-bb37-a2890455ca6e" \
       --request GET \
       http://127.0.0.1:8200/v1/secret/data/mysql/webapp | jq
{
  "errors": []
}

Since there is no value at secret/mysql/webapp, it returns an empty array.

Optional: Using the admin user's token, create some secrets in the secret/mysql/webapp path.

$ curl --header "X-Vault-Token: ..." --request POST --data @mysqldb.txt \

$ cat mysqldb.text
{
  "url": "foo.example.com:35533",
  "db_name": "users",
  "username": "admin",
  "password": "p@ssw0rd"
}

Now, try to read secrets from secret/mysql/webapp using the client_token again. This time, it should return the values you just created.

» Advanced Features

The Role ID is equivalent to a username, and Secret ID is the corresponding password. The app needs both to log in with Vault. Naturally, the next question becomes how to deliver those values to the expected client.

A common solution involves three personas instead of two: admin, app, and trusted entity. The trusted entity delivers the Role ID and Secret ID to the client by separate means.

For example, Terraform as a trusted entity can deliver the Role ID onto the virtual machine. When the app runs on the virtual machine, the Role ID already exists on the virtual machine.

AppRole auth method workflow

Secret ID is like a password. To keep the Secret ID confidential, use response wrapping so that only the expected client can unwrap the Secret ID.

In Step 3, you executed the following command to retrieve the Secret ID:

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

Instead, use response wrapping by passing the -wrap-ttl parameter:

$ vault write -wrap-ttl=60s -f auth/approle/role/jenkins/secret-id

Key                             Value
---                             -----
wrapping_token:                 9bbe23b7-5f8c-2aec-83dc-e97e94a2e632
wrapping_accessor:              cb5bdc8f-0cdb-35ff-0e68-9de57a79c3bf
wrapping_token_ttl:             1m0s
wrapping_token_creation_time:   2018-01-08 21:29:38.826611 -0800 PST
wrapping_token_creation_path:   auth/approle/role/jenkins/secret-id

Send this wrapping_token to the client so that the response can be unwrapped and obtain the Secret ID.

$ VAULT_TOKEN=9bbe23b7-5f8c-2aec-83dc-e97e94a2e632 vault unwrap

Key                 Value
---                 -----
secret_id           575f23e4-01ad-25f7-2661-9c9bdbb1cf81
secret_id_accessor  7d8a40b7-a6fd-a634-579b-b7d673ff86fb

NOTE: To retrieve the Secret ID alone, you can use jq as follows:

$ VAULT_TOKEN=2577044d-cf86-a065-e28f-e2a14ea6eaf7 vault unwrap -format=json | jq -r ".data.secret_id"

b07d7a47-1d0d-741d-20b4-ae0de7c6d964

» Help and Reference