Fun with OpenAM13 Authz Policies over REST – the ‘ssoToken’ parameter of the ‘Subject’

I recently blogged about the using the ‘claims’ parameter of the subject item in a REST call for policy evaluation in OpenAM 13.  (See http://yaunap.blogspot.co.uk/2016/07/fun-with-openam13-authz-policies-over.html). In that article I blithely stated that using the ‘ssoToken’ parameter was fairly obvious.  However, I thought I’d take the time to explore this in a little more detail to ensure my understanding is complete.  This is partly because I started thinking about OIDC JWT tokens, and the fact that OpenAM stateless sessions (nothing to do with OIDC) also use JWT tokens.

Let’s first ensure we understand stateful and stateless sessions.
(It’s documented here, in the Admin guide: https://backstage.forgerock.com/#!/docs/openam/13.5/admin-guide#chap-session-state)

Stateful sessions are your typical OpenAM session.  When a user successfully authenticates with OpenAM they will establish a session.  A Stateful session means that all the details about that session are held by the OpenAM server-side services.  By default, this is ‘in-memory’, but can be persisted to an OpenDJ instances in order to support high-availability and scalability across geographically disperse datacentres.  The client of the authentication request receives a session identifier, typically stored by a web application as a session cookie, that is passed back to the OpenAM servers so that the session details can be retrieved.  It’s called ‘stateful’ because the server needs to maintain the state of the session.
A session identifier for a stateful session might look something like this:
AQIC5wM2LY4Sfcw4EfByyKNoSnml3Ngk0bxcJa-LD-qrwSc.*AAJTSQACMDEAAlNLABM3NzI1Nzk4NDU0NTIyMTczODA2AAJTMQAA*
Basically, it’s just a unique key to the session state.

Stateless sessions are new in OpenAM 13.  These alleviate the need for servers to maintain and store state, which avoids the need to replicate persisted state across multiple datacentres.  Of course, there is still session ‘state’…it’s just no longer stored on the server.  Instead all state information is packaged up into a JWT and passed to the client to maintain.  Now, on each request, the client can send the complete session information back to an OpenAM server in order for it to be processed.  OpenAM does not need to perform a lookup of the session information from the stateful repository because all the information is right there in the JWT.  This means that for a realm configured to operate with stateless sessions, the client will receive a much bigger token on successful authentication
Therefore, a stateless session token might look something like:

AQIC5wM2LY4Sfcx_OSZ6Qe07K0NShFK6hZ2LWb6Pn2jNBTs.*AAJTSQACMDEAAlNLABMzMjQ1MDI5NDA0OTk0MjQyMTY0AAJTMQAA*eyAidHlwIjogIkpXVCIsICJhbGciOiAiSFMyNTYiIH0.eyAic2VyaWFsaXplZF9zZXNzaW9uIjogIntcInNlY3JldFwiOlwiM2M0NzczYzQtM2ZkZS00MjI2LTk4YzctMzNiZGQ5OGY2MjU0XCIsXCJleHBpcnlUaW1lXCI6MTQ2ODg2MTk3NTE0OCxcImxhc3RBY3Rpdml0eVRpbWVcIjoxNDY4ODU0Nzc1MTQ4LFwic3RhdGVcIjpcInZhbGlkXCIsXCJwcm9wZXJ0aWVzXCI6e1wiQ2hhclNldFwiOlwiVVRGLThcIixcIlVzZXJJZFwiOlwiYm9iXCIsXCJGdWxsTG9naW5VUkxcIjpcIi9vcGVuYW0vVUkvTG9naW4_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.FSmj5Sn-ibGoqWTCerGBZ-IYVp1V54HVGj5A53Td8Ao

Obviously, this is much larger and looks more complex.  This token is essentially made up of two parts:
1. a fake stateful session identifier
2. a JWT
OpenAM always prepends a fake stateful session identifier to this JWT for backwards compatibility. So, the actual JWT starts *after* the second asterisk (*).  i.e. from the bit that begins eyAidH… right through to the end.

You can use tools like jwt.io and jwtinspector.io to unpack and read this JWT.
e.g, for the JWT above, you can see the payload data which is how OpenAM represents the session information:

Now, turning our attention to the policy evaluation REST calls we see that there is an option to use ‘ssoToken’ as a parameter to the ‘subject’ item.

In a realm that uses the default ‘stateful’ sessions then any policy evaluation REST call that uses the ‘ssoToken’ parameter should use a stateful session identifier.  The policy will then have full access to the session information as well the profile data of the user identified by the session.

A stateless realm works exactly the same way.  You now need to provide the *full* stateless token (including the ‘fake’ stateful identifier with the JWT component) and the policy will have access to the state information from the JWT as well as information about the user from the datastore (such as group membership)

For example:

curl --request POST --header "iPlanetDirectoryPro: AQIC5wM2LY4SfcxxJaG7LFOia1TVHZuJ4_OVm9lq5Ih5uXA.*AAJTSQACMDEAAlNLABQtMjU4MDgxNTIwMzk1NzA5NDg0MwACUzEAAA..*" --header "Content-Type: application/json" --data '{"resources":["orders"],"application":"api","subject":{"ssoToken":"AQIC5wM2LY4SfcyRBqm_r02CEJ5luC4k9A6HPqDitS9T5-0.*AAJTSQACMDEAAlNLABQtNTc4MzI5MTk2NjQzMjUxOTc2MAACUzEAAA..*eyAidHlwIjogIkpXVCIsICJhbGciOiAiSFMyNTYiIH0.eyAic2VyaWFsaXplZF9zZXNzaW9uIjogIntcInNlY3JldFwiOlwiN2RiODdhMjQtMjk5Ni00YzkxLTkyNTUtOGIwNzdmZDEyYmFkXCIsXCJleHBpcnlUaW1lXCI6MTQ2ODkzNTgyODUyNSxcImxhc3RBY3Rpdml0eVRpbWVcIjoxNDY4OTI4NjI4NTI1LFwic3RhdGVcIjpcInZhbGlkXCIsXCJwcm9wZXJ0aWVzXCI6e1wiQ2hhclNldFwiOlwiVVRGLThcIixcIlVzZXJJZFwiOlwiYm9iXCIsXCJGdWxsTG9naW5VUkxcIjpcIi9vcGVuYW0vVUkvTG9naW4_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.Dnjk-9MgANmhX4jOez12HcYAW9skck-HFuTPnzEmIq8"}}' http://as.uma.com:8080/openam/json/ScopeAz/policies?_action=evaluate
Might return:
[{"advices":{},"ttl":9223372036854775807,"resource":"orders","actions":{"permit":true},"attributes":{}}]
Assuming the policy looks something like this:
…and, in this specific case, that the authentication level for the ‘subject’ of the ssoToken is set to two or greater, as well as the ‘subject’ being a member of the the ‘api_order’ group in the datastore.
Next up, we’ll look at using OIDC tokens in the subject parameter of the REST call.

This blog post was first published @ yaunap.blogspot.no, included here with permission from the author.

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