Leveraging cloud.gov authentication
cloud.gov uses Cloud Foundry’s User Account and Authentication (UAA) server to provide identity management capabilities for the cloud.gov platform.
App developers can leverage cloud.gov’s UAA instance as a backend that brokers authentication with supported identity providers (currently EPA, FDIC, GSA, and a cloud.gov provider that supports other agencies). You can use cloud.gov’s authentication brokering if the users that you need to authenticate in your application are federal employees and contractors who can use those authentication methods.
This service handles only authentication, not authorization – it’s up to your application to manage what they can access within the application. Once you set it up, you can direct your users to the list of ways to get cloud.gov access; they don’t need any org or space roles, they just need to be able to log into cloud.gov.
Using cloud.gov authentication
Register your application instances
You will first need to register all instances (such as dev, staging, and production) with cloud.gov’s UAA. To register your instance, use the cloud.gov identity provider service.
Integrate with your application
UAA handles authentication according to the OpenID Connect specification, which is “a simple identity layer on top of the OAuth 2.0 protocol.”
There are two important cloud.gov URLs you will need to use:
https://login.fr.cloud.gov/oauth/authorize, which is where you will direct the user to login with their agency credentials
https://uaa.fr.cloud.gov/oauth/token, which is where you will exchange auth codes for auth tokens
If you are already familiar with OAuth 2.0, you might know where to go from here. If not, read on for a basic example of how to do the OAuth dance.
Send your user to login.fr.cloud.gov
First, generate a link (or redirect the user) to the authorize URL with these query parameters:
client_id=<YOUR APP'S REGISTERED NAME>
You can optionally set a
state parameter with any value you’d like.
It will be returned to you in a later step. While optional, it’s highly
recommended that you use it for security reasons.
Here is an example:
<a href="https://login.fr.cloud.gov/oauth/authorize?client_id=NAME&response_type=code"> Log in </a>
Once the user clicks on this link, they will be sent to cloud.gov to login.
The user is returned to your site
Once the user successfully logs in with their credentials, your app will
GET request to the callback URL associated with the registered
GET request will include query parameters:
code=<A UNIQUE ACCESS CODE>
state=<VALUE FROM STATE PARAM IN AUTHORIZE LINK>
Now your site’s backend will need to exchange the access code for an access token. Here is where things get fun.
First, exchange the
codefor an authorization token by sending a
POSTrequest to the token endpoint (
https://uaa.fr.cloud.gov/oauth/token) with the following form-encoded parameters:
code=<CODE FROM QUERY PARAM IN CALLBACK REQUEST>
client_id=<YOUR APP'S REGISTERED NAME>
client_secret=<THE SECRET KEY YOU RECEIVED WHEN REGISTERING YOUR APP>
If everything works and UAA is able to verify your request, the response from that
POSTrequest will be JSON encoded and will contain these important members:
access_token- a JSON Web Token
expires_in- time in seconds until the
refresh_token- a refresh token that can be exchanged for another
access_tokenwhen the current one expires
access_tokenis a JSON Web Token that can be decoded using a library such as node-jsonwebtoken. See https://jwt.io/ for a list of libraries for various languages. Decode it to get the authenticated user’s
If you get an expired token error at some point in the future, you can exchange the
refresh_tokenfrom the previous step to get a new
access_token, so you might want to securely save the
refresh_tokenassociated with the authenticated user.
For an example of this entire process in under 100 lines of node JS, see the example client.
Using the fake UAA server
During development, you may want to authenticate against a local server running cg-fake-uaa, a minimal “fake” version of the cloud.gov UAA server. Aside from making login easier and allowing for offline development, it also makes the OAuth handshake easier to debug.