SAML: An XML Framework for Exchanging Authentication and Authorization Information + SPML, XCBF Prateek Mishra August 2002

Agenda SAML Status and Impact SAML in a Nutshell SAML and Web Services [thanks to Eve Maler (SUN) and Marc Chanliau (Netegrity) for the materials used in this presentation]

SAML Status The SAML 1.0 Specification Set is at Commitee Specification maturity level Entered a balloting period in pursuit of OASIS Standard status on 1 June Available at open.org/committees/security/#documentshttp:// open.org/committees/security/#documents SSTC discussion around next steps ongoing WS-Security Profile of SAML

SAML Impact Implementations available from … JSR-155 Java API standard and Reference Implementation ongoing (complete in 2002) Liberty Alliance uses and extends SAML 1.0 Several products available (Baltimore, Entegrity) and many more announced (Netegrity, Tivoli, Oblix, RSA, SUN, Quadrasis, CrossLogic, Sigaba, ePeople, …)

SAML 1.0: Main Features Normative Specification is in two parts: Assertion and Protocol XML Schema Bindings and Profiles Assertion: a set of statements in a standard envelope Statement: a declaration of fact about a subject Three types: attribute, authentication and authorization decision Protocol: SAML web services defined as XML request-response pairs Services consume and/or produce SAML assertions

Bindings and Profiles SAML 1.0 includes a SOAP-over-HTTP binding for SAML protocol Trust model and SOAP-over-HTTP details required for interoperability Profile: use of SAML to solve a business problem SAML 1.0 includes a family of Web Browser SSO profiles

All assertions have some common information Issuer and issuance timestamp Assertion ID Subject Name plus the security domain Optional subject confirmation, e.g. public key “Conditions” under which assertion is valid SAML clients must reject assertions containing unsupported conditions Special kind of condition: assertion validity period Additional “advice” E.g., to explain how the assertion was made

Authentication Statement An issuing authority asserts that: subject S was authenticated by means M at time T Caution: Actually checking or revoking of credentials is not in scope for SAML! Password exchange Challenge-response Etc.

Attribute Statement An issuing authority asserts that: subject S is associated with attributes X, Y, Z with values “a”, “b”, “c”…(XML fragments) Often this would be gotten from an LDAP repository “john.doe” in “example.com” is associated with attribute “Department” with value “Human Resources”

Example “John Doe” logged in at 9AM at example.com. He is a manager with spending limit of $10K. John Doe John Doe Manager 10,000

Authorization decision assertion An issuing authority decides whether to grant the request: by subject S to perform action A on resource R given evidence E (other assertions) The subject could be a human or a program The resource could be a web page or a web service, for example

Example authorization decision assertion READ …

SAML Protocol Actors

SAML Protocol Defined via XML request-response pairs A includes one of two query forms Assertion Lookup based on simple query language Assertion Lookup by id or artifact Query for assertions with AuthN statements by matching against subject name and authentication method Query for assertions with Attribute statements by matching against subject name and attribute name(s) Authorization Decision Assertion Request

Authorization decision assertion request “Is this subject allowed to access the specified resource in the specified manner, given this evidence?” This type of request is the most complex Models classical PEP (policy enforcement point) and PDP (policy decision point) dialog

SAML and Web Services SAML Protocol describes a class of security services (expressed as web services) SAML responders support: Lookup by assertion id (remote) lookup of attributes or authentication information, Interaction between a PEP and a remote PDP SOAP Binding for SAML 1.0 provides interoperable implementation

Securing a web service using SAML WS-Security Profile of SAML draft-sstc-ws-sec-profile-03 available at element carries SAML assertions or assertion identifier references. Additional signatures may be added to provide proof-of-possession (and data integrity)

WS-Security profile WS-Security Header

Messaging Use-Case Two parties: a buyer and a seller Asymmetrical relationship is assumed Seller is already known to buyer, but buyer is not known to seller, a common situation E.g., server-side certificates might be used to authenticate seller If it were symmetrical, additional SAML steps would happen on the right side too This would be an extension of this scenario

Web service secured by SAML

Service Provisioning Markup Language What is SPML? Open standard for defining and exchanging identity provisioning requests in XML Loosely-coupled model for integration and operation of identity provisioning request flows What does it look like? An XML Schema – data layout for expressing the request (C.R.U.D) and attributes required for a given provisioning request A Protocol – a basic request/response dialog for exchanging request schema A Binding – the definition of how you pack the schema and protocol in a message transport like HTTP or SOAP. When is it available? Expected December 2002

XCBF – Common Biometric Format The XCBF TC will define a common set of secure XML encodings for the patron formats specified in CBEFF, the Common Biometric Exchange File Format (NISTIR 6529).