awx/docs/credential_plugins.md

Credential Plugins

By default, sensitive credential values (such as SSH passwords, SSH private keys, API tokens for cloud services) in AWX are encrypted with a symmetric encryption cipher utilizing AES-256 in CBC mode alongside a SHA-256 HMAC and stored in the AWX database.

Alternatively, AWX supports retrieving secret values from third-party secret management systems, such as HashiCorp Vault and Microsoft Azure Key Vault. These external secret values will be fetched on demand every time they are needed (generally speaking, immediately before running a playbook that needs them).

Configuring Secret Lookups

When configuring AWX to pull a secret from a third party system, there are generally three steps.

Here is an example of creating an (1) AWX Machine Credential with a static username, example-user and (2) an externally sourced secret from HashiCorp Vault Key/Value system which will populate the (3) password field on the Machine Credential.

1. Create the Machine Credential with a static username, example-user.

   HTTP POST https://awx.example.org/api/v2/credentials/
   
   {
       "organization": X,
       "credential_type": <primary_key_of_machine_credential_type>,
       "inputs": {
           "username": "example-user"
       }
   }
   
   

2. Create a second credential used to authenticate with the external secret management system (e.g.,, in this example, specifying a URL and an OAuth2.0 token to access HashiCorp Vault)

   HTTP POST https://awx.example.org/api/v2/credentials/
   {
       "organization": X,
       "credential_type": <primary_key_of_hashicorp_vault_credential_type>,
       "inputs": {
           "url": "https://my-vault.example.org",
           "token": "some-oauth-token",
           "api_version": "v2",
       }
   }
   
   

3. Link the password field for the Machine credential to the external system by specifying the source (in this example, the HashiCorp credential) and metadata about the path (e.g., /some/path/to/my/password/).

   HTTP POST https://awx.example.org/api/v2/credentials/N/input_sources/
   {
       "input_field_name": "",
       "source_credential": <primary_key_of_hashicorp_vault_credential>
       "metadata": {
           "secret_path": "/path/to/my/secret/"
           "secret_field": "password"
           "secret_version": 92
       }
   }
   

Note that you can perform these lookups on any credential field - not just the password field for Machine credentials. You could just as easily create an AWS credential and use lookups to retrieve the Access Key and Secret Key from an external secret management system.

Writing Custom Credential Plugins

Credential Plugins in AWX are just importable Python functions that are registered using setuptools entrypoints (https://setuptools.readthedocs.io/en/latest/setuptools.html#dynamic-discovery-of-services-and-plugins)

Example plugins officially supported in AWX can be found in the source code at awx.main.credential_plugins.

Credential plugins are any Python object which defines attribute lookups for .name, .inputs, and .backend:

import collections

CredentialPlugin = collections.namedtuple('CredentialPlugin', ['name', 'inputs', 'backend'])

def some_callable(value_from_awx, **kwargs):
    return some_libary.get_secret_key(
        url=kwargs['url'],
        token=kwargs['token'],
        key=kwargs['secret_key']
    )

some_fancy_plugin = CredentialPlugin(
    'My Plugin Name',
    # inputs will be used to create a new CredentialType() instance
    #
    # inputs.fields represents fields the user will specify *when they create*
    # a credential of this type; they generally represent fields
    # used for authentication (URL to the credential management system, any
    # fields necessary for authentication, such as an OAuth2.0 token, or
    # a username and password). They're the types of values you set up _once_
    # in AWX
    #
    # inputs.metadata represents values the user will specify *every time
    # they link two credentials together*
    # this is generally _pathing_ information about _where_ in the external
    # management system you can find the value you care about i.e.,
    #
    # "I would like Machine Credential A to retrieve its username using
    # Credential-O-Matic B at secret_key=some_key"
    inputs={
        'fields': [{
            'id': 'url',
            'label': 'Server URL',
            'type': 'string',
        }, {
            'id': 'token',
            'label': 'Authentication Token',
            'type': 'string',
            'secret': True,
        }],
        'metadata': [{
            'id': 'secret_key',
            'label': 'Secret Key',
            'type': 'string',
            'help_text': 'The value of the key in My Credential System to fetch.'
        }],
        'required': ['url', 'token', 'secret_key'],
    },
    # backend is a callable function which will be passed all of the values
    # defined in `inputs`; this function is responsible for taking the arguments,
    # interacting with the third party credential management system in question
    # using Python code, and returning the value from the third party
    # credential management system
    backend = some_callable

Plugins are registered by specifying an entry point in the setuptools.setup() call (generally in the package's setup.py file - https://github.com/ansible/awx/blob/devel/setup.py):

setuptools.setup(
    ...,
    entry_points = {
        ...,
        'awx.credential_plugins': [
            'fancy_plugin = awx.main.credential_plugins.fancy:some_fancy_plugin',
        ]
    }
)

Fetching vs. Transforming Credential Data

While most credential plugins will be used to fetch secrets from external systems, they can also be used to transform data from Tower using an external secret management system. An example use case is generating signed public keys:

def my_key_signer(unsigned_value_from_awx, **kwargs):
    return some_libary.sign(
        url=kwargs['url'],
        token=kwargs['token'],
        public_data=unsigned_value_from_awx
    )

Programmatic Secret Fetching

If you want to programmatically fetch secrets from a supported external secret management system (for example, if you wanted to compose an AWX database connection string in /etc/tower/conf.d/postgres.py using an external system rather than storing the password in plaintext on your disk), doing so is fairly easy:

from awx.main.credential_plugins import hashivault
hashivault.hashivault_kv_plugin.backend(
    '',
    url='https://hcv.example.org',
    token='some-valid-token',
    api_version='v2',
    secret_path='/path/to/secret',
    secret_key='dbpass'
)