A JISC-funded project
//EduServ have released a tool they’re calling “Student Access Decision Maker” which makes you answer 9 questions to help you decide if a student, group of students, or students full stop should be able to access a particular resource.
The tool is embedded below:
//The OAuth working group have released an initial security review of the OAuth 2.0 specification which looks at a number of potential threats that implementors could face and how to mitigate them.
The document can be read here http://tools.ietf.org/html/draft-tschofenig-oauth-security-00.
The abstract of the document is below:
> The OAuth working group has finished work on the OAuth 2.0 core protocol as well as the Bearer Token specification. The Bearer Tokenis a TLS-based solution for ensuring that neither the interaction with the Authorization Server (when requesting a token) nor the interaction with the Resource Server (for accessing a protected resource) leads to token leakage. There has, however, always been the desire to develop a security solution that is “better” than Bearer Tokens (or at least different) where the Client needs to show
possession of some keying material when accessing a Resource Server.
> This document tries to capture the discussion and to come up with requirements to process the work on solutions.
> This document aims to discuss threats, security requirements and desired design properties of an enhanced OAuth security mechanism.
//This afternoon I decided to join the JANET Access and Identity Management group.
I hit the join group button on the site and was then prompted to join the JANET community. Seeing that it supported UK Access Management Federation (UK AMF) sign in, I entered my university’s name and clicked continue.
I was then forwarded to a login screen on the OpenAthens site. I don’t think I have any OpenAthens credentials so I clicked “Alternative login” (but first I accidentally clicked “Forgotten password?” thanks to my haste and the tiny links).
Then I had to choose my institution (again???).
Then I was asked to click on a link to take me to my institution’s login page.
Then I was forwarded onto our current Athens sign-in endpoint where I authenticated with my University of Lincoln network credentials.
Finally I was returned to the JANET Community sign-up screen only to see that none of the form fields had been pre-filled because of course the UK AMF is anonymised.
What a waste of time and a terrible user experience.
//One of the outputs of the Linkey project is an open source PHP library that implements the SAML bearer assertion extension (draft 13 at time of writing) to the OAuth 2.0 specification.
But what is SAML?
SAML, or Security Assertion Markup Language, is an XML-based framework that allows identity and security information to be shared across security domains – for example between two websites.
Information is exchanged through the concept of assertion tokens, which are XML documents that state facts about the assertion’s subject. For example, a SAML assertion about me might look like:
<saml:Response ID="_257f9d9e9fa14962c0803903a6ccad931245264310738" IssueInstant="2012-09-03T18:45:10Z" Version="2.0">
<saml:Issuer Format="urn:oasis:names:tc:SAML:2.0:nameid-format:entity">
https://www.lincoln.ac.uk
</saml:Issuer>
<saml:Status>
<saml:StatusCode Value="urn:oasis:names:tc:SAML:2.0:status:Success"/>
</saml:Status>
<saml:Assertion ID="_3c39bc0fe7b13769cab2f6f45eba801b1245264310738" IssueInstant="2012-09-03T18:45:10Z" Version="2.0">
<saml:Issuer Format="urn:oasis:names:tc:SAML:2.0:nameid-format:entity">
https://www.lincoln.ac.uk
</saml:Issuer>
<saml:Subject>
<saml:NameID Format="urn:oasis:names:tc:SAML:1.1:nameid-format:unspecified">
abilbie@lincoln.ac.uk
</saml:NameID>
<saml:SubjectConfirmation Method="urn:oasis:names:tc:SAML:2.0:cm:bearer">
<saml:SubjectConfirmationData NotOnOrAfter="2012-09-03T18:50:10Z" Recipient="https://sso.lincoln.ac.uk"/>
</saml:SubjectConfirmation>
</saml:Subject>
<saml:Conditions NotBefore="2012-09-03T18:45:10Z" NotOnOrAfter="2012-09-03T18:50:10Z">
<saml:AudienceRestriction>
<saml:Audience>https://sso.lincoln.ac.uk</saml:Audience>
</saml:AudienceRestriction>
</saml:Conditions>
<saml:AuthnStatement AuthnInstant="2012-09-03T18:45:10Z">
<saml:AuthnContext>
<saml:AuthnContextClassRef>urn:oasis:names:tc:SAML:2.0:ac:classes:unspecified</saml:AuthnContextClassRef>
</saml:AuthnContext>
</saml:AuthnStatement>
<saml:AttributeStatement>
<saml:Attribute Name="name">
<saml:AttributeValue xsi:type="xs:anyType">Alex Bilbie</saml:AttributeValue>
</saml:Attribute>
<saml:Attribute Name="network_id">
<saml:AttributeValue xsi:type="xs:anyType">abilbie</saml:AttributeValue>
</saml:Attribute>
<saml:Attribute Name="division">
<saml:AttributeValue xsi:type="xs:anyType">ICT Services</saml:AttributeValue>
</saml:Attribute>
<saml:Attribute Name="staff_directory_url">
<saml:AttributeValue xsi:type="xs:anyType">http://staff.lncd.org/abilbie</saml:AttributeValue>
</saml:Attribute>
</saml:AttributeStatement>
</saml:Assertion>
</saml:Response>
This assertion here states that my name is Alex Bilbie, my network ID is abilbie, my division is ICT Services and that my staff directory page is http://staff.lncd.org/abilbie.
Generally the assertion will be provided by an “identity provider” (a.k.a an IDP) and consumed by a “service provider” (a.ka. a SDP).
SAML is often used in single sign on environments. Let’s consider a student trying to sign in to the student union website:
How does SAML compare to OAuth?
For reference, this is how OAuth is used in a single sign on environment:
Now the OAuth flow looks longer it contains one important stage which is a requirement of the specification, specifically step 4 which is where the user is explicitly asked if they want to allow the client to access their data and also what data will be accessed. You could emulate this in the SAML flow but I think the upfront honesty so to speak in the OAuth flow is a huge advantage for users. Also most OAuth authentication servers allow users to revoke access to clients as well (i.e. their access token for that client is destroyed which immediately cuts access).
In both flows, the client/SDP itself is verified. In SAML this is done through certificate exchanges, in OAuth the client’s ID is validated at step 3 and step 6.
How does the assertion extension work?
Looking at the OAuth sign-in flow above, at step 6 the client exchanges the authorisation code for an access token. There are a number of ways this can step can actually work and each different method is called an authorisation grant type. The grant described above (and the grant is the generally used in most OAuth implementations) is the authorization_code grant.
The assertion extension defines a new authorisation grant type of urn:ietf:params:oauth:client-assertion-type:saml2-bearer. There is also another parameter called client_assertion which is a base64 encoded representation of the XML assertion. The client/SDP’s own credentials are in the assertion instead of being sent as client_id and client_secret parameters as in the authorisation code grant.
An example request would look like:
POST /token.oauth2 HTTP/1.1
Host: authz.example.net
Content-Type: application/x-www-form-urlencoded
grant_type=urn%3Aietf%3Aparams%3Aoauth%3Agrant-type%3Asaml2-
bearer&assertion=PEFzc2VydGlvbiBJc3N1ZUluc3RhbnQ9IjIwMTEtMDU
[...omitted for brevity...]aG5TdGF0ZW1lbnQ-PC9Bc3NlcnRpb24-
The specification includes a number of elements that must be included the assertion in order to provide the authorisation server with all the details it needs about the request.
As I understand it there is also an optional scope parameter that can be passed in the request any scopes that the client/SDP requires.
//I’ve spent the last few weeks working away on the OAuth PHP library which now includes a resource server as well as an authentication server. I’ve also started merging in Phil Sturgeon’s OAuth 2.0 client code library, which when I’ve finished, will result in a mean, lean PHP library for working with any aspect of OAuth 2.0 (authentication, resource sharing or client side). Both server classes are now fully unit tested and I’m at 90% code coverage for all of the methods. I’ve started writing documentation for the library too and I’m going to write a tutorial on how to build an OAuth secured API server in the CodeIgniter framework.
On the UAG side, both Tim and I have been reading Mastering Microsoft Forefront UAG 2010 Customisation (Amazon link). I’ve now got some ideas about how we can easily integrate the university’s OAuth server that I developed with our UAG install. More on this soon.