19. Token-Based Authentication¶

19.1.1. Access Rules for Applications¶

Access rules for applications are as follows:

• System administrators can view and manipulate all applications in the system

• Organization administrators can view and manipulate all applications belonging to Organization members

• Other users can only view, update, and delete their own applications, but cannot create any new applications

Tokens, on the other hand, are resources used to actually authenticate incoming requests and mask the permissions of the underlying user. There are two ways to create a token:

• POST to the /api/v2/tokens/ endpoint with application and scope fields to point to the related application and specify token scope

• POST to the /api/v2/applications/<pk>/tokens/ endpoint with the scope field (the parent application will be automatically linked)

Individual tokens are accessible via their primary keys: /api/<version>/tokens/<pk>/. Here is an example of a typical token:

{
    "id": 4,
    "type": "o_auth2_access_token",
    "url": "/api/v2/tokens/4/",
    "related": {
        "user": "/api/v2/users/1/",
        "application": "/api/v2/applications/1/",
        "activity_stream": "/api/v2/tokens/4/activity_stream/"
},
    "summary_fields": {
        "application": {
            "id": 1,
            "name": "Default application for root",
            "client_id": "mcU5J5uGQcEQMgAZyr5JUnM3BqBJpgbgL9fLOVch"
        },
        "user": {
            "id": 1,
            "username": "root",
            "first_name": "",
            "last_name": ""
        }
    },
    "created": "2018-02-23T14:39:32.618932Z",
    "modified": "2018-02-23T14:39:32.643626Z",
    "description": "App Token Test",
    "user": 1,
    "token": "*************",
    "refresh_token": "*************",
    "application": 1,
    "expires": "2018-02-24T00:39:32.618279Z",
    "scope": "read"
},

For an OAuth 2 token, the only fully editable fields are scope and description. The application field is non-editable on update, and all other fields are entirely non-editable, and are auto-populated during creation, as follows:

• user field corresponds to the user the token is created for, and in this case, is also the user creating the token

• expires is generated according to the Tower configuration setting OAUTH2_PROVIDER

• token and refresh_token are auto-generated to be non-clashing random strings

Both application tokens and personal access tokens are shown at the /api/v2/tokens/ endpoint. The application field in the personal access tokens is always null. This is a good way to differentiate the two types of tokens.

19.1.2. Access rules for tokens¶

Access rules for tokens are as follows:

• Users can create a token if they are able to view the related application; and are also able to create a personal token for themselves

• System administrators are able to view and manipulate every token in the system

• Organization administrators are able to view and manipulate all tokens belonging to Organization members

• System Auditors can view all tokens and applications

• Other normal users are only able to view and manipulate their own tokens

19.2.1. Token scope mask over RBAC system¶

The scope of an OAuth 2 token is a space-separated string composed of valid scope keywords, ‘read’ and ‘write’. These keywords are configurable and used to specify permission level of the authenticated API client. Read and write scopes provide a mask layer over the Role-Based Access Control (RBAC) permission system of Ansible Tower. Specifically, a ‘write’ scope gives the authenticated user the full permissions the RBAC system provides, while a ‘read’ scope gives the authenticated user only read permissions the RBAC system provides. Note that ‘write’ implies ‘read’ as well.

For example, if you have administrative permissions to a job template, you can view, modify, launch, and delete the job template if authenticated via session or basic authentication. In contrast, if you are authenticated using OAuth 2 token, and the related token scope is ‘read’, you can only view, but not manipulate or launch the job template, despite being an administrator. If the token scope is ‘write’ or ‘read write’, you can take full advantage of the job template as its administrator.

To acquire and use a token, first create an application token:

1. Make an application with authorization_grant_type set to password. HTTP POST the following to the /api/v2/applications/ endpoint (supplying your own organization ID):

{
    "name": "Admin Internal Application",
    "description": "For use by secure services & clients. ",
    "client_type": "confidential",
    "redirect_uris": "",
    "authorization_grant_type": "password",
    "skip_authorization": false,
    "organization": <organization-id>
}

2. Make a token and POST to the /api/v2/tokens/ endpoint:

{
    "description": "My Access Token",
    "application": <application-id>,
    "scope": "write"
}

This returns a <token-value> that you can use to authenticate with for future requests (this will not be shown again).

3. Use the token to access a resource. The following uses curl as an example:

curl -H "Authorization: Bearer <token-value>" -H "Content-Type: application/json" -X GET https://<tower>/api/v2/users/

The -k flag may be needed if you have not set up a CA yet and are using SSL.

To revoke a token, you can make a DELETE on the detail page for that token, using that token’s ID. For example:

curl -ku <user>:<password> -X DELETE https://<tower>/api/v2/tokens/<pk>/

Similarly, using a token:

curl -H "Authorization: Bearer <token-value>" -X DELETE https://<tower>/api/v2/tokens/<pk>/ -k

19.3.1. Application using authorization code grant type¶

The application authorization code grant type should be used when access tokens need to be issued directly to an external application or service.

{
    "name": "AuthCodeApp",
    "user": 1,
    "client_type": "confidential",
    "redirect_uris": "http://<tower>/api/v2",
    "authorization_grant_type": "authorization-code",
    "skip_authorization": false
}


.. _`Django-oauth-toolkit simple test application`: http://django-oauth-toolkit.herokuapp.com/consumer/

The workflow that occurs when you issue a GET to the authorize endpoint from the client application with the response_type, client_id, redirect_uris, and scope:

1. Tower responds with the authorization code and status to the redirect_uri specified in the application.

2. The client application then makes a POST to the api/o/token/ endpoint on Tower with the code, client_id, client_secret, grant_type, and redirect_uri.

3. Tower responds with the access_token, token_type, refresh_token, and expires_in.

Refer to Django’s Test Your Authorization Server toolkit to test this flow.

You may specify the number of seconds an authorization code remains valid in the Configure Tower - System settings:

Requesting an access token after this duration will fail. The duration defaults to 600 seconds (10 minutes), based on the RFC6749 recommendation.

The best way to set up app integrations with Ansible Tower using the Authorization Code grant type is to whitelist the origins for those cross-site requests. More generally, you need to whitelist the service or application you are integrating with Tower, for which you want to provide access tokens. To do this, have your Administrator add this whitelist to their local Tower settings:

CORS_ORIGIN_REGEX_WHITELIST = [
    r"http://django-oauth-toolkit.herokuapp.com*",
    r"http://www.example.com*"
]

Where http://django-oauth-toolkit.herokuapp.com and http://www.example.com are applications needing tokens with which to access Tower.

19.3.2. Application using password grant type¶

The password grant type or Resource owner password-based grant type is ideal for users who have native access to the web app and should be used when the client is the Resource owner. The following supposes an application, ‘Default Application’ with grant type password:

{
    "id": 6,
    "type": "application",
    ...
    "name": "Default Application",
    "user": 1,
    "client_id": "gwSPoasWSdNkMDtBN3Hu2WYQpPWCO9SwUEsKK22l",
    "client_secret": "fI6ZpfocHYBGfm1tP92r0yIgCyfRdDQt0Tos9L8a4fNsJjQQMwp9569eIaUBsaVDgt2eiwOGe0bg5m5vCSstClZmtdy359RVx2rQK5YlIWyPlrolpt2LEpVeKXWaiybo",
    "client_type": "confidential",
    "redirect_uris": "",
    "authorization_grant_type": "password",
    "skip_authorization": false
}

Logging in is not required for password grant type, so you can simply use curl to acquire a personal access token through the /api/v2/tokens/ endpoint:

curl -k --user <user>:<password> -H "Content-type: application/json" \
-X POST \
--data '{
    "description": "Token for Nagios Monitoring app",
    "application": 1,
    "scope": "write"
}' \
https://<tower>/api/v2/tokens/

Upon success, a response displays in JSON format containing the access token, refresh token and other information:

HTTP/1.1 200 OK
Server: nginx/1.12.2
Date: Tue, 05 Dec 2017 16:48:09 GMT
Content-Type: application/json
Content-Length: 163
Connection: keep-alive
Content-Language: en
Vary: Accept-Language, Cookie
Pragma: no-cache
Cache-Control: no-store
Strict-Transport-Security: max-age=15768000

{"access_token": "9epHOqHhnXUcgYK8QanOmUQPSgX92g", "token_type": "Bearer", "expires_in": 315360000000, "refresh_token": "jMRX6QvzOTf046KHee3TU5mT3nyXsz", "scope": "read"}

19.4.1. Refresh an existing access token¶

The following example shows an existing access token with a refresh token provided:

{
    "id": 35,
    "type": "access_token",
    ...
    "user": 1,
    "token": "omMFLk7UKpB36WN2Qma9H3gbwEBSOc",
    "refresh_token": "AL0NK9TTpv0qp54dGbC4VUZtsZ9r8z",
    "application": 6,
    "expires": "2017-12-06T03:46:17.087022Z",
    "scope": "read write"
}

The /api/o/token/ endpoint is used for refreshing the access token:

curl -X POST \
    -d "grant_type=refresh_token&refresh_token=AL0NK9TTpv0qp54dGbC4VUZtsZ9r8z" \
    -u "gwSPoasWSdNkMDtBN3Hu2WYQpPWCO9SwUEsKK22l:fI6ZpfocHYBGfm1tP92r0yIgCyfRdDQt0Tos9L8a4fNsJjQQMwp9569eIaUBsaVDgt2eiwOGe0bg5m5vCSstClZmtdy359RVx2rQK5YlIWyPlrolpt2LEpVeKXWaiybo" \
    http://<tower>/api/o/token/ -i

In the above POST request, refresh_token is provided by refresh_token field of the access token above that. The authentication information is of format <client_id>:<client_secret>, where client_id and client_secret are the corresponding fields of the underlying related application of the access token.

Upon success, a response displays in JSON format containing the new (refreshed) access token with the same scope information as the previous one:

HTTP/1.1 200 OK
Server: nginx/1.12.2
Date: Tue, 05 Dec 2017 17:54:06 GMT
Content-Type: application/json
Content-Length: 169
Connection: keep-alive
Content-Language: en
Vary: Accept-Language, Cookie
Pragma: no-cache
Cache-Control: no-store
Strict-Transport-Security: max-age=15768000

{"access_token": "NDInWxGJI4iZgqpsreujjbvzCfJqgR", "token_type": "Bearer", "expires_in": 315360000000, "refresh_token": "DqOrmz8bx3srlHkZNKmDpqA86bnQkT", "scope": "read write"}

Essentially, the refresh operation replaces the existing token by deleting the original and then immediately creating a new token with the same scope and related application as the original one. Verify that new token is present and the old one is deleted in the /api/v2/tokens/ endpoint.

19.4.2. Revoke an access token¶

Similarly, you can revoke an access token by using the /api/o/revoke-token/ endpoint.

Revoking an access token by this method is the same as deleting the token resource object, but it allows you to delete a token by providing its token value, and the associated client_id (and client_secret if the application is confidential). For example:

curl -X POST -d "token=rQONsve372fQwuc2pn76k3IHDCYpi7" \
-u "gwSPoasWSdNkMDtBN3Hu2WYQpPWCO9SwUEsKK22l:fI6ZpfocHYBGfm1tP92r0yIgCyfRdDQt0Tos9L8a4fNsJjQQMwp9569eIaUBsaVDgt2eiwOGe0bg5m5vCSstClZmtdy359RVx2rQK5YlIWyPlrolpt2LEpVeKXWaiybo" \
http://<tower>/api/o/revoke_token/ -i

Alternatively, you can use the manage utility, revoke_oauth2_tokens, to revoke tokens as described in the the Token and session management section.

This setting can be configured at the system-level in the Ansible Tower User Interface:

Upon success, a response of 200 OK displays. Verify the deletion by checking whether the token is present in the /api/v2/tokens/ endpoint.