Sun OpenSSO Enterprise 8.0 Technical Overview

Chapter 11 Choosing a Federation Option

Sun OpenSSO Enterprise supports multiple federation standards, such as those developed by the Organization for the Advancement of Structured Information Standards (OASIS) and the Liberty Alliance Project. This chapter contains information on these federation options.

Federation Options

Federation is used to solve the problem of cooperation across heterogeneous, autonomous environments. In the beginning, federation meant using the Liberty Alliance Project Identity Federation Framework (Liberty ID-FF). Since then, other federation specifications have been developed including the Security Assertion Markup Language (SAML) and WS-Federation. OpenSSO Enterprise supports all of these specifications.

To get started, SAML v2 is strongly preferred for federation. WS-Federation is an alternative for integrating with Active Directory Federation Services (ADFS). Liberty ID-FF and SAML v1.x are still supported but should only be used when SAML v2 is not an option as the SAML v2 specification supersedes both the Liberty ID-FF and SAML v1.x specifications. More information on these options can be found in the following sections:

Note –

OpenSSO Enterprise has appropriated the terms from the Liberty ID-FF for all federation protocol implementations in the OpenSSO Enterprise console.

Using SAML

SAML defines an XML-based framework for exchanging identity information across security domains for purposes of authentication, authorization and single sign-on. It was designed to be used within other specifications (the Liberty Alliance Project, the Shibboleth project, and the Organization for the Advancement of Structured Information Standards have all adopted aspects of SAML) although the latest release (SAML v2) has incorporated back into the framework elements from the specifications developed by those very same organizations. The SAML specifications consist of a number of components, illustrated by Figure 11–1.

Figure 11–1 Components of the SAML Specifications

Components of the SAML specifications

The SAML specification defines the assertion security token format as well as profiles that standardize the HTTP exchanges required to transfer XML requests and responses between an asserting authority and a trusted partner. An assertion is a package of verified security information that supplies one or more statements concerning a principal’s authentication status, access authorization decisions, or identity attributes. (A person identified by an email address is a principal as might be a printer.) Assertions are issued by an asserting authority (a platform or application that declares whether a subject has been authenticated into its system), and received by relying parties (partner sites defined by the authority as trusted). Asserting authorities use different sources to configure assertion information, including external data stores or assertions that have already been received and verified.

The most recent SAML v2 specifications are defined more broadly than those developed for SAML v1.x — with particular attention paid to functionality dealing with federation. Before SAML v2 was introduced, SAML v1.x was simply a way to exchange identity data. In fact, up to version 1.1, the Liberty Alliance Project Identity Federation Framework (Liberty ID-FF) was developed using the SAML 1.0 specification. Liberty ID-FF version 1.2 was also developed using the SAML v1.1 specification. But, following the release of version 1.2, the Liberty ID-FF was incorporated into the SAML v2 specification. Additionally, SAML v2 adds components of the Shibboleth initiative. Thus, SAML v2 is a major revision, providing significant additional functionality and making the previous versions of SAML incompatible with it. Going forward, SAML v2 will be the basis on which OpenSSO Enterprise implements federation. Figure 11–2 illustrates the convergence.

Figure 11–2 Liberty ID-FF and SAML Convergence

Illustration of Liberty ID-FF and SAML convergence

Note –

For more information on this convergence (including how the Shibboleth Project was also integrated), see the Federation section of Strategic Initiatives on the Liberty Alliance Project web site.

More information on the SAML implementations can be found in the following sections).

Caution – Caution –

SAML v1.x and SAML v2 assertions and protocol messages are incompatible.

About SAML v2

OpenSSO Enterprise delivers a solution that allows businesses to establish a framework for sharing trusted information across a distributed network of partners using the standards-based SAML v2. Towards this end, HTTP(S)-based service endpoints and SOAP service endpoints are supplied as well as assertion and protocol object manipulating classes. A web browser can access all HTTP(S)-based service endpoints and an application can make use of the SOAP endpoints and API as long as metadata for each participating business on BOTH sides of the SAML v2 interaction is exchanged beforehand.

Figure 11–3 illustrates the SAML v2 framework which consists of web-based services [using SOAP, XML over HTTP(S) or HTML over HTTP(S)], and Java™-based application provider interfaces (API) and service provider interfaces (SPI). Additionally, the figure shows an agent embedded into a web container in which a service provider application is deployed. This agent enables the service provider to participate in the SAML v1.x or Liberty ID-FF protocols.

Figure 11–3 SAML v2 Architecture

This figure illustrates the architecture of SAML v2.

The following sections contain more information about the SAML v2 framework.

Key Features

The key features of SAML v2 in OpenSSO Enterprise include:

Additionally, OpenSSO Enterprise has received high scores and passed the Liberty Alliance Project interoperability tests for SAML v2. For more information, see the SAMLv2 support matrix on the Liberty Alliance Project web site.


In order to communicate using the SAML v2 profiles you need, at least, two instances of OpenSSO Enterprise. One instance will act for the identity provider and the other will act for the service provider. Name identifiers are used to communicate regarding a user.

Note –

SAML v2 single sign-on interactions support both persistent and transient identifiers. A persistent identifier is saved to a particular user entry as the value of two attributes. A transient identifier is temporary and no data will be written to the user's data store entry.

To prepare your instances for SAML v2 interactions, you need to exchange a particular provider's configuration information or metadata between all participating identity and service providers, and assemble the providers into a circle of trust. Utility APIs can then be used to communicate with the data store, reading, writing, and managing the relevant properties and property values. For more information see the Sun OpenSSO Enterprise 8.0 Administration Guide.

Application Programming Interfaces

The SAML v2 framework contains API that can be used to construct and process assertions, requests, and responses. The SAML v2 Java API packages include:

More information can be found in Using the SAML v2 SDK in Sun OpenSSO Enterprise 8.0 Developer’s Guide and the Sun OpenSSO Enterprise 8.0 Java API Reference.

Service Provider Interfaces

The com.sun.identity.saml2.plugins package provides pluggable interfaces to implement SAML v2 functionality into your application. Default implementations are provided, but a customized implementation can be plugged in by modifying the corresponding attribute in the provider's extended metadata configuration file. The interfaces include mappers for:

More information can be found in Service Provider Interfaces in Sun OpenSSO Enterprise 8.0 Developer’s Guide and the Sun OpenSSO Enterprise 8.0 Java API Reference.

JavaServer Pages

The SAML v2 framework provides JSP that can be used to initiate single sign-on, single logout and termination requests from either the identity provider or the service provider using a web browser. The JSP accept query parameters to allow flexibility in constructing SAML v2 requests; they can be modified for your deployment. More information can be found in JavaServer Pages in Sun OpenSSO Enterprise 8.0 Developer’s Guide.

About SAML v1.x

OpenSSO Enterprise can be configured to use SAML v1.x to achieve interoperability between vendor platforms that provide SAML v1.x assertions. Assertions are issued by a SAML v1.x asserting authority (a platform or application that declares whether a subject has been authenticated into its system), and received by relying parties (partner sites defined by the authority as trusted). SAML v1.x authorities use different sources to configure the assertion information, including external data stores or assertions that have already been received and verified. SAML v1.x can be used to allow OpenSSO Enterprise to:

Note –

Although Liberty ID-FF (as described in Using the Liberty ID-FF) integrates aspects of the SAML v1.x specifications, its usage of SAML v1.x is independent of the SAML v1.x framework as described in this section.

Figure 11–4 illustrates how SAML v1.x interacts with the other components in OpenSSO Enterprise.

Figure 11–4 SAML v1.x Interaction in OpenSSO Enterprise

This figure illustrates SAML v1.x interaction
within OpenSSO Enterprise.

Which Flavor of SAML to Use?

When choosing the flavor of SAML to use there are a number of things that should be taken into account. For example, SAML v1.x and SAML v2 assertions and protocol messages are incompatible. The following section have more information to help make the decision.

Using SAML v2 or OpenSSO Enterprise CDSSO

Cross Domain Single Sign On (CDSSO) is a proprietary mechanism from Sun OpenSSO Enterprise, designed before any federation specifications existed. The basic difference between the proprietary CDSSO (as described in Part II, Access Control Using OpenSSO Enterprise) and SAML v2 is that CDSSO uses a single authentication authority, a mechanism to move a cookie between multiple DNS domains. SAML v2, on the other hand, gives you the option of using multiple authentication authorities, with one authority asserting the identity of the user to the other.

CDSSO, in certain cases, is easier to set up and manage than federation but, federation solves a broader set of single sign-on issues than CDSSO. CDSSO requires all policy agents to be configured to use a single OpenSSO Enterprise server. This means only one user identity can exist in the entire system whereas, when using SAML v2, user identities can exist on multiple systems (service providers or identity providers). Because of the single identity in CDSSO interactions, issues such as account mapping, attribute flow and session synchronization are not relevant thus, if you need to implement these features, use SAML v2. If the following points are valid to your planned deployment, CDSSO may be a simpler and more suitable solution than federation.

For more information on CDSSO, see Chapter 6, Models of the User Session and Single Sign-On Processes.

Using SAML v1.x or Liberty ID-FF

The Liberty ID-FF (as described in Using the Liberty ID-FF) and SAML v1.x should only be used when integrating with a partner that is not able to use SAML v2. SAML v1.x was designed to address the issue of cross-domain single sign-on. It does not solve issues such as privacy, single logout, and federation termination. The Liberty Alliance Project was formed to develop technical specifications that would solve business process issues including single sign-on, account linking and consent, among others.

The SAML v1.x specifications and the Liberty Alliance Project specifications do not compete with one another. They are complementary. In fact, the Liberty Alliance Project specifications leverage profiles from the SAML specifications. The decision of whether to use SAML v1.x or the Liberty specifications depends on your goal. In general, SAML v1.x should suffice for single sign-on basics. The Liberty Alliance Project specifications can be used for more sophisticated functions and capabilities, such as global sign-out, attribute sharing, web services. The following table compares the benefits of the two.

Table 11–1 Comparison of the SAML v1.x and Liberty Alliance Project Specifications

SAML v1.x Uses 

Liberty Alliance Project Uses 

Cross-domain single sign-on 

Single sign-on only after user federation

No user federation 

User federation 

No privacy control, best for use within one company 

Built on top of SAML 

User identifier is sent in plain text 

User identifier is sent as a unique handle 

Single log out 

Single log out 

Using the Liberty ID-FF

The Liberty Alliance Project was formed to develop technical specifications that would solve business process issues including single sign-on, federation and consent. The Liberty Alliance Project Identity Federation Framework (Liberty ID-FF) uses a name identifier to pass identity data between identity providers and service providers. The name identifier is a randomly generated character string that is assigned to a principal and used to federate the principal's accounts at the identity provider and service provider sites. This pseudonym allows all providers to identify a principal without knowing the user's actual identity. The name identifier has meaning only in the context of the relationship between providers. SAML v1.x is used for provider interaction.

Note –

Liberty ID-FF was initially defined as an extension of SAML 1.0 (and later SAML 1.1). The extensions have now been contributed back into SAML v2 which, going forward, will be the basis on which the Liberty Alliance Project builds additional federated identity applications. See Using SAML for more information on this convergence.

The following sections contain information about the Liberty ID-FF and the features implemented in OpenSSO Enterprise.

Liberty ID-FF Features

The following sections contain information about the Liberty ID-FF features implemented in OpenSSO Enterprise.

Federated Single Sign-On

Let's assume that a principal has separate user accounts with a service provider and an identity provider in the same circle of trust. In order to gain access to these individual accounts, the principal would authenticate with each provider separately. If federating with the Liberty ID-FF though, after authenticating with the service provider, the principal may be given the option to federate the service provider account with the identity provider account. Consenting to the federation of these accounts links them for SSO, the means of passing a user's credentials between applications without the user having to reauthenticate. SSO and federated SSO have different processes. With OpenSSO Enterprise, you can achieve SSO in the following ways:

To set up federated SSO, you must first establish SSO. Following that, enable federation in the metadata for the service provider entity and the identity provider entity using OpenSSO Enterprise. Liberty ID-FF providers differentiate between federated users by defining a unique identifier for each account. (They are not required to use the principal's actual provider account identifier.) Providers can also choose to create multiple identifiers for a particular principal. However, identity providers must create one handle per user for service providers that have multiple web sites so that the handle can be resolved across all of them.

Note –

Because both the identity provider entity and the service provider entity in a federation need to remember the principal's identifier, they create entries that note the value in their respective user repositories. In most scenarios, the identity provider's identifier is conveyed to a service provider and not visa versa. For example, if a service provider does not maintain its own user repository, the identity provider's identifier is used.

OpenSSO Enterprise can accommodate the following SSO and federation-related functions:

Additionally, OpenSSO Enterprise can accommodate the federation features explained in the following sections.


Auto federation will automatically federate a user's disparate provider accounts based on a common attribute. During SSO, if it is deemed a user at provider A and a user at provider B have the same value for the defined common attribute (for example, an email address), the two accounts will be federated without consent or interaction from the principal. For more information, see Part II, Federation, Web Services, and SAML Administration, in Sun OpenSSO Enterprise 8.0 Administration Guide.

Bulk Federation

Federating one user's service provider account with their identity provider account generally requires the principal to visit both providers and link them. An organization though needs the ability to federate user accounts behind the scenes. OpenSSO Enterprise provides a script for federating user accounts in bulk. The script allows the administrator to federate many (or all) of a principal's provider accounts based on metadata passed to the script. Bulk federation is useful when adding a new service provider to an enterprise so you can federate a group of existing employees to the new service. For more information, see Part II, Federation, Web Services, and SAML Administration, in Sun OpenSSO Enterprise 8.0 Administration Guide.

Authentication and Authentication Context

SSO is the means by which a provider of either type can convey to another provider that a principal has been authenticated. Authentication is the process of validating user credentials; for example, a user identifier accompanied by an associated password. You can authenticate users with OpenSSO Enterprise in the following ways:

Identity providers use local (to the identity provider) session information mapped to a user agent as the basis for issuing SAML authentication assertions to service providers. Thus, when the principal uses a user agent to interact with a service provider, the service provider requests authentication information from the identity provider based on the user agent's session information. If this information indicates that the user agent's session is presently active, the identity provider will return a positive authentication response to the service provider. OpenSSO Enterprise allows providers to exchange the following minimum set of authentication information with regard to a principal.

SAML v1.x is used for provider interaction during authentication but not all SAML assertions are equal. Different authorities issue SAML assertions of different quality. Therefore, the Liberty ID-FF defines how the consumer of a SAML assertion can determine the amount of assurance to place in the assertion. This is referred to as the authentication context, information added to the SAML assertion that gives the assertion consumer the details they need to make an informed entitlement decision. For example, a principal uses a simple identifier and a self-chosen password to authenticate to a service provider. The identity provider sends an assertion to a second service provider that states how the principal was authenticated to the first service provider. By including the authentication context, the second service provider can place an appropriate level of assurance on the associated assertion. If the service provider were a bank, they might require stronger authentication than that which has been used and respond to the identity provider with a request to authenticate the user again using a more stringent context. The authentication context information sent in the assertion might include:

The Liberty ID-FF specifications define authentication context classes against which an identity provider can claim conformance. The Liberty ID-FF authentication contexts are listed and described in the following table.

Table 11–2 Authentication Context Classes




Identified when a mobile principal has an identity for which the identity provider has vouched. 


Identified by detailed and verified registration procedures, a user's consent to sign and authorize transactions, and DigitalID-based authentication. 


Identified when the real identity of a mobile principal has not been strongly verified. 


Identified when a principal authenticates to an identity provider by using a password over an unprotected HTTP session. 


Identified when a principal authenticates to an identity provider by using a password over an SSL-protected session. 


Identified when an identity provider must authenticate a principal for a current authentication event and the principal has previously authenticated to the identity provider. This affirms to the service provider a time lapse from the principal's current resource access request. 

Note –

The context for the previously authenticated session is not included in this class because the user has not authenticated during this session. Thus, the mechanism that the user employed to authenticate in a previous session should not be used as part of a decision on whether to now allow access to a resource.


Identified when a principal uses a smart card to authenticate to an identity provider. 


Identified when a principal uses a smart card with an enclosed private key and a PIN to authenticate to an identity provider. 


Identified when a principal uses an X.509 certificate stored in software to authenticate to the identity provider over an SSL-protected session. 


Identified when a principal authenticates through a time synchronization token. 

For more information, see the Liberty ID-FF Authentication Context Specification and . Additionally, there is an XML schema defined which the identity provider authority can use to incorporate the context of the authentication in the SAML assertions it issues.

The Common Domain for Identity Provider Discovery

Service providers need a way to determine which identity provider in a circle of trust is used by a principal requesting authentication. Because circles of trust are configured without regard to their location, this function must work across DNS-defined domains. A common domain is configured, and a common domain cookie written, for this purpose.

Let's suppose a circle of trust contains more than one identity provider. In this case, a service provider trusts more than one identity provider so, when a principal needs authentication, the service provider with which the principal is communicating must have the means to determine the correct identity provider. To ascertain a principal’s identity provider, the service provider invokes a protocol exchange to retrieve the common domain cookie, a cookie written for the purpose of introducing the identity provider to the service provider. If no common domain cookie is found, the service provider will present a list of trusted identity providers from which the principal can choose. After successful authentication, the identity provider writes (using the configured Writer Service URL) a common domain cookie and, the next time the principal attempts to access a service, the service provider finds and reads the common domain cookie (using the configured Reader Service URL), to determine the identity provider. More information on the Common Domain for Identity Provider Discovery is available in the following sections, and in Finding an Identity Provider for Authentication in Sun OpenSSO Enterprise 8.0 Administration Guide.

The Common Domain

The common domain is established for use only within the scope of identity provider discovery in a defined circle of trust. In OpenSSO Enterprise deployments, the identity provider discovery WAR is deployed in a web container installed in a predetermined and preconfigured common domain so that the common domain cookie is accessible to all providers in the circle of trust. For example, if an identity provider is available at, a service provider is available at, and the defined common domain is, the addresses will be and, respectively. If the HTTP server in the common domain is operated by the service provider, the service provider will redirect the user agent to the appropriate identity provider.

The Common Domain Cookie

After an identity provider authenticates a principal, the identity provider sets a URL-encoded cookie defined in a predetermined domain common to all identity providers and service providers in the circle of trust. The common domain cookie is named _liberty_idp for Liberty ID-FF and _saml_idp for SAML v2. After successful authentication, a principal’s identity provider appends their particular encoded identifier to a list in the cookie. If their identifier is already present in the list, the identity provider may remove the initial appearance and append it again. The intent is that the service provider reads the last identifier on the cookie’s list to find the principal’s most recently established identity provider.

Note –

The identifiers in the common domain cookie are a list of SuccinctID elements encoded in the Base64 format. One element maps to each identity provider in the circle of trust. Service providers then use this SuccinctID element to find the user's preferred identity provider.

The Writer Service and the Reader Service

After a principal authenticates with a particular identity provider, the identity provider redirects the principal's browser to the configured Writer Service URL using a parameter that indicates they are the identity provider for this principal. The Writer Service then writes a cookie using the parameter. Thereafter, all providers configured in this common domain will be able to tell which identity provider is used by this principal. Thus, the next time the principal attempts to access a service hosted by a service provider in the same common domain, the service provider retrieves and reads the common domain cookie, using the configured Reader Service URL, to determine the identity provider.

The Writer Service URL and the Reader Service URL can be defined for use with the Liberty ID-FF or the SAML v2 federation protocol. The URLs are defined when you create a circle of trust for federation. The Common Domain for Identity Provider Discovery for Liberty ID-FF is based on the Identity Provider Introduction Profile detailed in the Liberty ID-FF Bindings and Profiles Specifications. The Common Domain for Identity Provider Discovery for SAML v2 is an implementation of the Identity Provider Discovery Profile as described in the Profiles for the OASIS Security Assertion Markup Language (SAML) V2.0 specification.

Identifiers and Name Registration

OpenSSO Enterprise supports name identifiers that are unique across all providers in a circle of trust. This identifier can be used to obtain information for or about the principal without requiring the user to consent to a long-term relationship with the service provider. When beginning federation, the identity provider generates an opaque value that serves as the initial name identifier that both the service provider and the identity provider use to refer to the principal when communicating with each other. After federation, the identity provider or the service provider may register a different opaque value. If a service provider registers a different opaque value for the principal, the identity provider must use the new identifier when communicating with the service provider about the principal. The reasons for changing an identifier would be implementation-specific. The initial name identifier defined by the identity provider is always used to refer to the principal unless a new name identifier is registered.

Global Logout

A principal may establish authenticated sessions with both an identity provider and individual service providers, based on authentication assertions supplied by the identity provider. When the principal logs out of a service provider session, the service provider sends a logout message to the identity provider that provided the authentication for that session. When this happen, or the principal manually logs out of a session at an identity provider, the identity provider sends a logout message to each service provider to which it provided authentication assertions under the relevant session. The one exception is the service provider that sent the logout request to the identity provider.

Dynamic Identity Provider Proxying

An identity provider can choose to proxy an authentication request to an identity provider in another authentication domain if it knows that the principal has been authenticated with this identity provider. The proxy behavior is defined by the local policy of the proxying identity provider. However, a service provider can override this behavior and choose not to proxy. This function can be implemented as a form of authentication when, for instance, a roaming mobile user accesses a service provider that is not part of the mobile home network. For more information see ID-FF Federation Operations in Sun OpenSSO Enterprise 8.0 Administration Guide.

About the Liberty ID-FF Process

The Liberty ID-FF is designed to work with heterogeneous platforms, various networking devices (including personal computers, mobile phones, and personal digital assistants), and emerging technologies. The process of Liberty ID-FF federation begins with authentication. A user attempting to access a resource protected by OpenSSO Enterprise are redirected to the proprietary Authentication Service via an OpenSSO Enterprise login page. After the user provides credentials, the Authentication Service allows or denies access to the resource based on the outcome.

Note –

For more information about the proprietary Authentication Service, see the Chapter 7, Authentication and the Authentication Service.

When the user attempts access to a resource that belongs to a trusted member provider of a configured circle of trust, the process of user authentication begins with the search for a valid OpenSSO Enterprise session token from the proprietary Authentication Service. The process can go in one of two directions based on whether a session token is found.

Figure 11–5 illustrates these divergent paths. The process shown is the default process when no application has been deployed. When an application is deployed and using OpenSSO Enterprise, the process will change based on the query parameters and preferences passed to OpenSSO Enterprise from the participating application. For more information, see Sun OpenSSO Enterprise 8.0 Administration Guide.

Figure 11–5 Default Process of Federation

Illustration depicting the default process of Liberty ID-FF federation
in OpenSSO Enterprise.

As illustrated, the pre-login process establishes a valid OpenSSO Enterprise session. When a principal attempts to access a service provider site and no OpenSSO Enterprise session token is found, OpenSSO Enterprise searches for a federation cookie. A federation cookie is implemented by OpenSSO Enterprise and is called fedCookie. It can have a value of either yes or no, based on the principal’s federation status.

Note –

A federation cookie is not defined in the Liberty Alliance Project specifications.

At this point, the pre-login process may take one of the following paths:

Using WS-Federation

WS-Federation is part of the larger Web Services Security (WS-Security) framework which provides a means for applying security to web services through the use of security tokens. WS-Security describes how to attach signature and encryption headers as well as security tokens (including binary security tokens such as X.509 certificates and Kerberos tickets) to SOAP messages. WS-Trust, another specification in the WS-Security framework, provides for federation by defining a Security Token Service (STS) and a protocol for requesting and issuing the security tokens. WS-Federation, as implemented in OpenSSO Enterprise, uses the OpenSSO Enterprise Security Token Service (modelled on the WS-Trust specification) to allow providers in different security realms to broker trust using information on identities, identity attributes and authentication, and provider federation. A principal requests a token from the Security Token Services. This token, which may represent the principal's primary identity, a pseudonym, or the appropriate attributes, is presented to the service provider for authentication and authorization. WS-Federation uses several security tokens as well as the mechanism for associating them with messages. This release of OpenSSO Enterprise has implemented the following features of the WS-Federation specification.

The WS-Federation implementation in OpenSSO Enterprise is based on the application's SAML v2 code and uses WS-Federation 1.1 metadata. Authentication request parameters are represented directly as GET parameters, and the authentication response is a WS-Trust RequestSecurityTokenResponse element.

Note –

There is no authentication context mapping, persistent or transient NameID identifiers or auto-federation in the OpenSSO Enterprise implementation of WS-Federation.

The entry points for all WS-Federation functionality will be implemented as servlets. JavaServer Pages (JSP) are used only for HTML content (for example, the HTML form used to send the WS-Federation single response from the identity provider to the service provider). The following figure illustrates the flow of messages between OpenSSO Enterprise (acting as the service provider) and the Active Directory (acting as the identity provider).

Figure 11–6 WS-Federation Process Flow

Process flow of WS-Federation functionality

In a WS-Federation interaction, the request by an unauthenticated user attempting to access a protected web site is redirected to the Active Directory for Federation Services (ADFS) identity provider. After the user is authenticated (either by a back-end single sign-on or by entering credentials), ADFS posts a form containing a signed SAML assertion to the service provider. The service provider validates the assertion, copies the attributes into the user's session, and gives the appropriate access.

Note –

Microsoft Active Directory Federation Services supports single sign-on via WS-Federation.