awx/docs/auth/oauth.md

Introduction

Starting from Tower 3.3, OAuth 2 will be used as the new means of token-based authentication. Users will be able to manage OAuth tokens as well as applications, a server-side representation of API clients used to generate tokens. By including an OAuth token as part of the HTTP authentication header, a user will be able to authenticate herself and gain more restrictive permissions on top of the base RBAC permissions of the user. The degree of restriction is controllable by the scope of an OAuth token. Refer to RFC 6749 for more details of OAuth 2 specification.

Usage

Managing OAuth applications and tokens

The root of OAuth management endpoints is /api/<version>/me/oauth/, which gives a list of endpoint roots for managing individual type of OAuth resources: OAuth application under /api/<version>/me/oauth/applications/ and OAuth token under /api/<version>/me/oauth/tokens/. The reason for OAuth management endpoints to be under /api/<version>/me/ is because, as an authentication approach, OAuth resources will only take effect to the underlying user.

Each OAuth application belongs to a specific user, and is used to represent a specific API client on the server side. For example, if AWX user Alice wants to make her curl command to talk to AWX, the first thing is creating a new application and probably name it Alice' curl client.

Individual applications will be accessible via their primary keys: /api/<version>/me/oauth/applications/<primary key of an application>/. Here is a typical application:

{
    "id": 1,
    "type": "application",
    "url": "/api/v2/me/oauth/applications/1/",
    "related": {
        "user": "/api/v2/users/1/",
        "tokens": "/api/v2/me/oauth/applications/1/tokens/",
        "activity_stream": "/api/v2/me/oauth/applications/1/activity_stream/"
    },
    "summary_fields": {
        "user": {
            "id": 1,
            "username": "admin",
            "first_name": "",
            "last_name": ""
        },
        "tokens": {
            "count": 13,
            "results": [
                {
                    "token": "UdglJ1IkG3YrkzPWkEIwBqWP2xL8X7",
                    "id": 16
                },
                ...
            ]
        }
    },
    "created": "2017-12-07T16:08:21.341687Z",
    "modified": "2017-12-07T16:08:21.342015Z",
    "name": "admin's app",
    "user": 1,
    "client_id": "l7VbJdYxqKzoewQR7iZAYkiUI7AdqQhJuiAF4TqJ",
    "client_secret": "gsplwGti48nJhs5dJ9IMJ0BqN3LvwvFPFgbrQzhXz4bT2oOJBmoCj2egpAUF6Ivme1LFLYAeLwYkmj8AVHEkpYfYxMvK6LTNJG8nO2AIGt7l6MCgj9oD5cgwLvsfGxl2",
    "client_type": "confidential",
    "redirect_uris": "",
    "authorization_grant_type": "password",
    "skip_authorization": false
}

In the above example, user is the underlying user this application associates to; name can be used as a human-readable identifier of the application. The rest fields, like client_id and redirect_uris, are mainly used for OAuth authorization, which will be covered later in 'Using OAuth token system' section.

Fields client_id and client_secret are immutable identifiers of applications, and will be generated during creation; Fields user and authorization_grant_type, on the other hand, are immutable on update, meaning they are required fields on creation, but will become read-only after that.

On RBAC side:

• system admins will be able to see and manipulate all applications in the system;
• Organization admins will be able to see and manipulate all applications belonging to Organization members;
• Other normal users will only be able to see, update and delete their own applications, but cannot create any new application.

Note a default new application will be created for each new user. So each new user is supposed to see at least one application available to them.

Tokens, on the other hand, are resources used to actually authenticate incoming requests and mask the permissions of underlying user. There are two ways of creating a token: POSTing to /me/oauth/tokens/ endpoint by providing application and scope fields to point to related application and specify token scope; or POSTing to /me/oauth/applications/<pk>/tokens/ by providing only scope, while the parent application will be automatically linked.

Individual tokens will be accessible via their primary keys: /api/<version>/me/oauth/tokens/<primary key of a token>/. Here is a typical token:

{
    "id": 17,
    "type": "access_token",
    "url": "/api/v2/me/oauth/tokens/17/",
    "related": {
        "user": "/api/v2/users/1/",
        "application": "/api/v2/me/oauth/applications/4/",
        "activity_stream": "/api/v2/me/oauth/tokens/17/activity_stream/"
    },
    "summary_fields": {
        "application": {
            "id": 4,
            "name": "admin's token",
            "client_id": "D6SwhKbfp2LuUjkmiUpMMYFyNqhpv5PTVci7eXTT"
        },
        "user": {
            "id": 1,
            "username": "admin",
            "first_name": "",
            "last_name": ""
        }
    },
    "created": "2017-12-12T16:48:10.489550Z",
    "modified": "2017-12-12T16:48:10.522189Z",
    "user": 1,
    "token": "kqHqxfpHGRRBXLNCOXxT5Zt3tpJogn",
    "refresh_token": "miZq3hqSugvYxhzdQYJIBDgIHxJPnT",
    "application": 4,
    "expires": "2017-12-13T02:48:10.488180Z",
    "scope": "read"
}

For an OAuth token, the only fully mutable field is scope. application field is immutable on update, and all other fields are totally immutable, and will be auto-populated during creation: user field will be the user field of related application; expires will be generated according to Tower configuration setting OAUTH2_PROVIDER; token and refresh_token will be auto- generated to be non-crashing random strings.

On RBAC side:

• A user will be able to create a token if she is able to see the related application;
• System admin is able to see and manipulate every token in the system;
• Organization admins will be able to see and manipulate all tokens belonging to Organization members;
• Other normal users will only be able to see and manipulate their own tokens.

Using OAuth token system

The most significant usage of OAuth is authenticating users. token field of a token is used as part of HTTP authentication header, in the format Authorization: Bearer <token field value>. Here is a curl command example:

curl -H "Authorization: Bearer kqHqxfpHGRRBXLNCOXxT5Zt3tpJogn" http://localhost:8013/api/v2/credentials/

According to OAuth 2 specification, users should be able to acquire, revoke and refresh an access token. In AWX the equivalent, and the easiest, way of doing that is creating a token, deleting a token, and deleting a token quickly followed by creating a new one.

On the other hand, the specification also provides standard ways of doing those. RFC 6749 elaborates on those topics, but in summary, an OAuth token is officially acquired via authorization using authorization information provided by applications (special application fields mentioned above). There are dedicated endpoints for authorization and token acquire; The token acquire endpoint is also responsible for token refresh; and token revoke is done by dedicated token revoke endpoint.

In AWX, our OAuth system is built on top of Django Oauth Toolkit, which provides full support on standard authorization, token revoke and refresh. AWX reuses them and puts related endpoints under /api/o/ endpoint. Detailed examples on some most typical usage of those endpoints are available as description text of /api/o/.

Token scope mask over RBAC system

The scope of an OAuth token is a space-separated string composed of keywords like 'read' and 'write'. These keywords are configurable and used to specify permission level of the authenticated API client. For the initial OAuth implementation, we use the most simple scope configuration, where the only valid scope keywords are 'read' and 'write'.

Read and write scopes provide a mask layer over the RBAC permission system of AWX. In specific, a 'write' scope gives the authenticated user full permissions the RBAC system provides, while 'read' scope gives the authenticated user only read permissions the RBAC system provides.

For example, if a user has admin permission to a job template, she can both see and modify, launch and delete the job template if authenticated via session or basic auth. On the other hand, if she is authenticated using OAuth token, and the related token scope is 'read', she can only see but not manipulate or launch the job template, despite she has admin role over it; if the token scope is 'write' or 'read write', she can take full advantage of the job template as its admin.

Acceptance Criteria

• All CRUD operations for OAuth applications and tokens should function as described.
• RBAC rules applied to OAuth applications and tokens should behave as described.
• A default application should be auto-created for each new user.
• Incoming requests using unexpired OAuth token correctly in authentication header should be able to successfully authenticate themselves.
• Token scope mask over RBAC should work as described.
• Tower configuration setting OAUTH2_PROVIDER should be configurable and function as described.
• /api/o/ endpoint should work as expected. In specific, all examples given in the description help text should be working (user following the steps should get expected result).