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For each protocol supported by the WSO2 Identity Server, there should be an inbound authenticator. The Identity Server includes inbound authenticators for SAML 2.0, OpenID, OpenID Connect, OAuth 2.0, Kerberos KDC, WS-Trust STS and WS-Federation (passive). In other words, the The responsibility of the SAML 2.0 request processor is to accept a SAML request from a service provider, validate the SAML request and then build a common object model understood by the authentication framework and handover the request to it. The responsibility of the SAML response builder is to accept a common object model from the authentication framework and build a SAML response out of it.
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