Active Directory Federation Services (ADFS) is a standards-based web Single Sign-On federated identity which implements claims based authentication across forests.
Active Directory Federation Services (ADFS for short) is a standards-based Web Single Sign-On federated identity which implements claims based authentication across forests. There are multiple versions ADFS 2.0 on WS2008/R2, ADFS in WS2012 (also called 2.1), ADFS in WS2012R2 (also called 3.0) and ADFS in WS2016 (also called 4.0)
ADFS provides authentication services for applications over standard protocols. We typically refer to these apps as claims based applications. Claims based authentication is the process of authenticating a user based on a set of claims about its identity contained in a trusted token. Such a token is often issued and signed by an entity that is able to authenticate the user by other means, and that is trusted by the entity doing the claims based authentication. Claims are essentially attributes derived from Active Directory, a LDAP or SQL server.
In ADFS, identity federation is established between two organizations by establishing trust between two security realms. A federation server on one side (the Accounts side) authenticates the user through the standard means in Active Directory Domain Services and then issues a token containing a series of claims about the user, including its identity.
On the other side, the Resources side, another federation server validates the token and issues another token for the local servers to accept the claimed identity. This allows a system to provide controlled access to its resources or services to a user that belongs to another security realm without requiring the user to authenticate directly to the system and without the two systems sharing a database of user identities or passwords.
Latest developer oriented information can be found at links below.
AD FS OpenID Connect/OAuth Concepts https://learn.microsoft.com/en-us/windows-server/identity/ad-fs/development/ad-fs-openid-connect-oauth-concepts
AD FS OpenID Connect/OAuth flows and Application Scenarios https://learn.microsoft.com/en-us/windows-server/identity/ad-fs/overview/ad-fs-openid-connect-oauth-flows-scenarios
