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Shibboleth A Technical Overview

Shibboleth A Technical Overview. Tom Scavo trscavo@ncsa.uiuc.edu NCSA. What is Shibboleth?. Shibboleth provides cross-domain single sign-on and attribute-based authorization while preserving user privacy Shibboleth is simultaneously: A project A specification An implementation.

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Shibboleth A Technical Overview

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  1. ShibbolethA Technical Overview Tom Scavotrscavo@ncsa.uiuc.edu NCSA

  2. What is Shibboleth? • Shibboleth provides cross-domain single sign-on and attribute-based authorization while preserving user privacy • Shibboleth is simultaneously: • A project • A specification • An implementation

  3. Shibboleth Project • Shibboleth, a project of Internet2-MACE: • Advocates a federated identity management policy framework focused on user privacy • Develops middleware architectures to facilitate inter-institutional attribute sharing • Manages an open source reference implementation of the Shibboleth spec • Shibboleth has made significant contributions to the SAML-based identity management space

  4. Collaborations Internet2 OASIS E-Auth Shibboleth Educause Liberty Vendors

  5. Shibboleth Specification • Shibboleth is an extension of the SAML 1.1 browser profiles: • Shibboleth Browser/POST Profile • Shibboleth Browser/Artifact Profile • Shibboleth Attribute Exchange Profile • See the Shibboleth spec for details:S. Cantor et al., Shibboleth Architecture: Protocols and Profiles. Internet2-MACE, 10 September 2005.

  6. Shibboleth Implementation • The Shibboleth implementation consists of two components: • Shibboleth Identity Provider • Shibboleth Service Provider • The Identity Provider is a J2EE webapp • The Service Provider is a C++ Apache module • A pure Java Service Provider is in beta

  7. The Shibboleth Experience

  8. The Shibboleth Wiki • For example, the Shibboleth wiki (hosted at ohio-state.edu) is “shibbolized”:https://authdev.it.ohio-state.edu/twiki/bin/view/GridShib/WebHome • To edit wiki pages, a user must be known to the wiki • Users have wikiNames but do not have wiki passwords • Users log into their home institution, which asserts user identity to the wiki

  9. Shib Browser Profile • The user clicks the link “Login via InQueue IdP” • This initiates a sequence of steps known as the Shibboleth Browser Profile 3 C L I E N T UIUC 4 InQueue 1 6 7 2 5 OSU 8

  10. Shib Browser Profile • InQueue provides a “Where Are You From?” service • The user chooses their preferred identity provider from a menu 3 C L I E N T UIUC 4 InQueue 1 6 7 2 5 OSU 8

  11. Shib Browser Profile • The user is redirected to UIUC login page • After login, the user is issued a SAML assertion and redirected back to the wiki 3 C L I E N T UIUC 4 InQueue 1 6 7 2 5 OSU 8

  12. Shib Browser Profile • After validating the assertion, the wiki@OSU retrieves user attributes via back-channel Shib attribute exchange 3 C L I E N T UIUC 4 InQueue 1 6 7 2 5 OSU 8

  13. Asserting Identity • Initially, the user is unknown to the wiki • After querying the home institution, the wiki knows the user’s identity • “trscavo-uiuc.edu” is wiki-speak for trscavo@uiuc.edu • The latter is eduPersonPrincipalName, an identity attribute asserted by the user’s home institution

  14. OpenIdP.org • By design, a user with an account at an institution belonging to InCommon, InQueue, or SDSS can log into the wiki:https://authdev.it.ohio-state.edu/twiki/bin/view/GridShib/WebHome • Other users can register at openidp.org, which is a zero-admin Shibboleth IdP • The openidp asserts an alternate form of identity (email addresses as opposed to eduPersonPrincipalName)

  15. Shibboleth SSO Profiles

  16. The Actors • Identity Provider • The Identity Provider (IdP) creates, maintains, and manages user identity • A Shibboleth IdP produces SAML assertions • Service Provider • The Service Provider (SP) controls access to services and resources • A Shibboleth SP consumes SAML assertions Identity Provider Authentication Authority Attribute Authority SSO Service Artifact Resolution Service Assertion Consumer Service Attribute Requester Resource Service Provider

  17. Shib SSO Profiles • Shibboleth SSO profiles are SP-first • Shibboleth specifies an Authentication Request Profile • Shibboleth Browser/POST Profile = Shib Authn Request Profile + SAML Browser/POST Profile • Shibboleth Browser/Artifact Profile = Shib Authn Request Profile + SAML Browser/Artifact Profile

  18. Shib AuthN Request Profile • A Shibboleth authentication request is an ordinary GET request:https://idp.org/shibboleth/SSO? providerId=https://sp.org/shibboleth/& shire=https://sp.org/shibboleth/SSO& target=https://sp.org/myresource& time=1102260120 • The client is redirected to this location after requesting a protected resource at the SP without a security context

  19. Shib Browser/POST Profile • Browser/POST is an SP-first profile • The IdP produces an assertion at step 4, which the SP consumes at step 5 Identity Provider C L I E N T Authentication Authority SSO Service Attribute Authority 4 3 Assertion Consumer Service 6 5 8 Resource 7 2 1 Service Provider

  20. Attributes

  21. Shib Attribute Exchange • A Shibboleth SP often queries an IdP for attributes after validating an authN assertion • An opaque, transient identifier called a handle is embedded in the authN assertion • The SP sends a SAML AttributeQuery message with handle attached

  22. Browser/POST Profile • The first 5 steps of this profile are identical to ordinary Browser/POST • Before redirecting the Client to the Resource Manager, the SP queries for attributes via a back-channel exchange Identity Provider C L I E N T Authentication Authority SSO Service Attribute Authority 4 3 7 6 Assertion Consumer Service Attribute Requester 8 5 10 Resource 9 2 1 Service Provider

  23. Browser/POST Step 1 • The Client requests a target resource at the SP Identity Provider C L I E N T Authentication Authority SSO Service Attribute Authority Assertion Consumer Service Resource 1 Service Provider

  24. Browser/POST Step 2 • The SP performs a security check on behalf of the target resource • If a valid security context at the SP does not exist, the SP redirects the Client to the single sign-on (SSO) service at the IdP Identity Provider C L I E N T Authentication Authority SSO Service Attribute Authority Assertion Consumer Service Resource 2 1 Service Provider

  25. Browser/POST Step 3 • The Client requests the SSO service at the IdP Identity Provider C L I E N T Authentication Authority SSO Service Attribute Authority 3 Assertion Consumer Service Resource 2 1 Service Provider

  26. Browser/POST Step 4 • The SSO service processes the authN request and performs a security check • If the user does not have a valid security context, the IdP identifies the principal (details omitted) • The SSO service produces an authentication assertion and returns it to the Client Identity Provider C L I E N T Authentication Authority SSO Service Attribute Authority 4 3 Assertion Consumer Service Resource 2 1 Service Provider

  27. Browser/POST Step 5 • The Client issues a POST request to the assertion consumer service at the SP • The authN assertion is included with the request Identity Provider C L I E N T Authentication Authority SSO Service Attribute Authority 4 3 Assertion Consumer Service 5 Resource 2 1 Service Provider

  28. Browser/POST Step 6 • The assertion consumer service validates the request, creates a security context at the SP • The attribute requester sends a (mutually authenticated) attribute query to the AA Identity Provider C L I E N T Authentication Authority SSO Service Attribute Authority 4 3 6 Assertion Consumer Service Attribute Requester 5 Resource 2 1 Service Provider

  29. Browser/POST Step 7 • The IdP returns an attribute assertion subject to attribute release policy • The SP filters the attributes according to attribute acceptance policy Identity Provider C L I E N T Authentication Authority SSO Service Attribute Authority 4 3 7 6 Assertion Consumer Service Attribute Requester 5 Resource 2 1 Service Provider

  30. Browser/POST Step 8 • The assertion consumer service updates the security context and redirects the Client to the target resource Identity Provider C L I E N T Authentication Authority SSO Service Attribute Authority 4 3 7 6 Assertion Consumer Service Attribute Requester 8 5 Resource 2 1 Service Provider

  31. Browser/POST Step 9 • The Client requests the target resource at the SP (again) Identity Provider C L I E N T Authentication Authority SSO Service Attribute Authority 4 3 7 6 Assertion Consumer Service Attribute Requester 8 5 Resource 9 2 1 Service Provider

  32. Browser/POST Step 10 • Since a security context exists, the SP returns the resource to the Client Identity Provider C L I E N T Authentication Authority SSO Service Attribute Authority 4 3 7 6 Assertion Consumer Service Attribute Requester 8 5 10 Resource 9 2 1 Service Provider

  33. Directory Schema • Neither Shibboleth nor SAML define any attributes per se • It is left to individual deployments to define their own attributes • A standard approach to user attributes is crucial • Without such standards, interoperability is impossible

  34. eduPerson • Internet2 and EDUCAUSE have jointly developed a set of attributes and associated bindings called eduPerson • The LDAP binding of eduPerson is derived from the standard LDAP object class called inetOrgPerson [RFC 2798] • Approximately 40 attributes have been defined by InCommon as common identity attributes

  35. InCommon Attributes • InCommon’s 6 “highly recommended” attributes: (eduPersonTargetedID does not have a precise value syntax)

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