Tuesday, February 14, 2017

Bootstrapping an OAuth2 Authorization server using UAA

A quick way to get a robust OAuth2 server running in your local machine is to use the excellent Cloud Foundry UAA project. UAA is used as the underlying OAUth2 authorization server in Cloud Foundry deployments and can scale massively, but is still small enough that it can be booted up on modest hardware.

I will cover using the UAA in two posts. In this post, I will go over how to get a local UAA server running and populate it with some of the actors involved in an OAuth2 authorization_code flow - clients and users, and in a follow up post I will show how to use this Authorization server with a sample client application and in securing a resource.

Starting up the UAA

The repository for the UAA project is at https://github.com/cloudfoundry/uaa


Downloading the project is simple, just clone this repo:
git clone https://github.com/cloudfoundry/uaa

If you have a local JDK available, start it up using:
./gradlew run

This version of UAA uses an in-memory database, so the test data generated will be lost on restart of the application.


Populate some data

An awesome way to interact with UAA is its companion CLI application called uaac, available here. Assuming that you have the uaac cli downloaded and UAA started up at its default port of 8080, let us start by pointing the uaac to the uaa application:

uaac target http://localhost:8080/uaa

and log into it using one of the canned client credentials(admin/adminsecret):

uaac token client get admin -s adminsecret

Now that a client has logged in, the token can be explored using :
uaac context

This would display the details of the token issued by UAA, along these lines:

[3]*[http://localhost:8080/uaa]

  [2]*[admin]
      client_id: admin
      access_token: eyJhbGciOiJIUzI1NiJ9.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.B-RmeIvYttxJOMr_CX1Jsinsr6G_e8dVU-Fv-3Qq1ow
      token_type: bearer
      expires_in: 43199
      scope: clients.read clients.secret clients.write uaa.admin clients.admin scim.write scim.read
      jti: d99b2850-bd45-4e97-822e-74a62e07f4c5

To see a more readable and decoded form of token, just run:
uaac token decode 
which should display a decoded form of the token:
jti: d99b2850-bd45-4e97-822e-74a62e07f4c5
  sub: admin
  authorities: clients.read clients.secret clients.write uaa.admin clients.admin scim.write scim.read
  scope: clients.read clients.secret clients.write uaa.admin clients.admin scim.write scim.read
  client_id: admin
  cid: admin
  azp: admin
  grant_type: client_credentials
  rev_sig: e78b0213
  iat: 1487039776
  exp: 1487082976
  iss: http://localhost:8080/uaa/oauth/token
  zid: uaa
  aud: admin clients uaa scim


Now, to create a brand new client(called client1), which I will be using in a follow on post:

uaac client add client1  \
  --name client1 --scope resource.read,resource.write \
  --autoapprove true  \
  -s client1 \
  --authorized_grant_types authorization_code,refresh_token,client_credentials \
  --authorities uaa.resource

This client is going to request a scope of resource.read, resource.write from users and will participate in authorization_code grant-type OAuth2 flows


Creating a resource owner or a user of the system:

uaac user add user1 -p user1 --emails user1@user1.com

and assigning this user a resource.read scope:

uaac group add resource.read
uaac member add resource.read user1


Exercise a test flow

Now that we have a client and a resource owner, let us exercise a quick authorization_code flow, uaac provides a handy command line option that provides the necessary redirect hooks to capture auth code and transforms the auth_code to an access token.

uaac token authcode get -c client1 -s client1 --no-cf

Invoking the above command should open up a browser window and prompt for user creds:



Logging in with the user1/user1 user that was created previously should respond with a message in the command line that the token has been successfully fetched, this can be explored once more using the following command:

uaac context

with the output, showing the details of the logged in user!:
jti: c8ddfdfc-9317-4f16-b3a9-808efa76684b
  nonce: 43c8d9f7d6264fb347ede40c1b7b44ae
  sub: 7fdd9a7e-5b92-42e7-ae75-839e21b932e1
  scope: resource.read
  client_id: client1
  cid: client1
  azp: client1
  grant_type: authorization_code
  user_id: 7fdd9a7e-5b92-42e7-ae75-839e21b932e1
  origin: uaa
  user_name: user1
  email: user1@user1.com
  auth_time: 1487040497
  rev_sig: c107f5c0
  iat: 1487040497
  exp: 1487083697
  iss: http://localhost:8080/uaa/oauth/token
  zid: uaa
  aud: resource client1

This concludes the whirlwind tour of setting up a local UAA and adding a couple of roles involved in a OAuth2 flow - a client and a user. I have not covered the OAuth2 flows itself, the Digital Ocean intro to OAuth2 is a very good primer on the flows.

I will follow this post with a post on how this infrastructure can be used for securing a sample resource and demonstrate a flow using Spring Security and Spring Boot.

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