How Microsoft identity platform uses the SAML protocol
Microsoft identity platform uses the SAML 2.0 protocol to enable applications to provide a single sign-on experience to their users. The Single Sign-On and Single Sign-Out SAML profiles of Azure AD explain how SAML assertions, protocols, and bindings are used in the identity provider service.
SAML Protocol requires the identity provider (Microsoft identity platform) and the service provider (the application) to exchange information about themselves.
When an application is registered with Azure AD, the app developer registers federation-related information with Azure AD. This information includes the Redirect URI and Metadata URI of the application.
Microsoft identity platform uses the cloud service's Metadata URI to retrieve the signing key and the logout URI. Customer can open the app in Azure AD -> App Registration and then in Settings -> Properties, they can update the Logout URL. This way Microsoft identity platform can send the response to the correct URL.
Azure Active Directory exposes tenant-specific and common (tenant-independent) single sign-on and single sign-out endpoints. These URLs represent addressable locations -- they are not just identifiers -- so you can go to the endpoint to read the metadata.
The tenant-specific endpoint is located at
https://login.microsoftonline.com/<TenantDomainName>/FederationMetadata/2007-06/FederationMetadata.xml. The <TenantDomainName> placeholder represents a registered domain name or TenantID GUID of an Azure AD tenant. For example, the federation metadata of the contoso.com tenant is at: https://login.microsoftonline.com/contoso.com/FederationMetadata/2007-06/FederationMetadata.xml
The tenant-independent endpoint is located at
https://login.microsoftonline.com/common/FederationMetadata/2007-06/FederationMetadata.xml. In this endpoint address, common appears instead of a tenant domain name or ID.
For information about the federation metadata documents that Azure AD publishes, see Federation Metadata.