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DRAFT

UC0: SP Requires Silver

The SP requires InCommon Silver LOA.

The SP includes http://id.incommon.org/assurance/silver in the SAML RequestedAuthnContext element. It accepts assertions that contain http://id.incommon.org/assurance/silver in the AuthnContext from IdPs with http://id.incommon.org/assurance/silver in InCommon metadata.

Commentary:

As usual, the SP should intelligently handle errors. In particular, the SP should be prepared to handle the case that not all users at a particular IdP may be eligible for Silver LOA (for example, users not vetted at Silver), so even if the IdP is tagged with http://id.incommon.org/assurance/silver in InCommon metadata, authentication for some users may result in an "AuthnFailed" response.

As an optimization, the SP may avoid issuing requests to IdPs that are not accredited at Silver, since these requests would always be rejected later anyway. The SP may locally block ("short-circuit") requests of this type. The SP may provide a local discovery interface that lists only IdPs with http://id.incommon.org/assurance/silver in InCommon metadata to constrain users to only choose Silver accredited IdPs.

Examples:

  • NIH SPs?

UC1: SP Requires Bronze

The SP requires InCommon Bronze LOA (or higher).

The SP includes http://id.incommon.org/assurance/silver and http://id.incommon.org/assurance/bronze in the SAML RequestedAuthnContext element. It accepts either:

Commentary:

As usual, the SP should intelligently handle errors. In particular, the SP should be prepared to handle the case that not all users at a particular IdP may be eligible for Silver or Bronze (for example, users not vetted at the Silver or passwords too weak for Bronze), so even if the IdP is tagged with http://id.incommon.org/assurance/silver or http://id.incommon.org/assurance/bronze in InCommon metadata, authentication for some users may result in an "AuthnFailed" response.

Examples:

  • The InCommon Federation Manager (FM)
  • The InCommon Certificate Manager (CM)

The FM and the CM recognize Bronze password credentials as the first factor of a two-factor authentication. The InCommon Operations Identity Provider is authoritative for the second "what you have" factor.

UC2: SP Prefers Silver

Motivation: The SP must operate in a world where not all IdPs can yet provide Silver assertions, and Silver-capable IdPs can't provide Silver assertions for all users/circumstances. In cases where lower LOA assertions are used, the SP restricts access/functionality and/or implements other compensating controls. The SP wants to get Silver assertions whenever possible. The SP can determine which IdPs are Silver-capable from metadata.

SP Strategy A: For IdPs that are Silver-capable according to metadata, the SP includes http://id.incommon.org/assurance/silver and urn:oasis:names:tc:SAML:2.0:ac:classes:unspecified in the SAML RequestedAuthnContext element. The IdP returns a SAML assertion containing http://id.incommon.org/assurance/silver in the AuthnContext when possible (i.e., the user is vetted at Silver and the authentication method is Silver), and otherwise returns a SAML assertion containing another AuthnContextClassRef value in the AuthnContext or returns an error. In other words, the IdP prefers to return Silver assertions when requested over other types of assertions. The SP checks to see if the assertion contains http://id.incommon.org/assurance/silver in the AuthnContext and the IdP has http://id.incommon.org/assurance/silver in its InCommon metadata. If the check passes, the SP considers the authentication to be at the Silver level. If not, the SP considers the authentication to be lower LOA.

SP Strategy B: Alternatively, the SP may include only http://id.incommon.org/assurance/silver in the SAML AuthnRequest element, and if the IdP returns an "AuthnFailed" response, possibly indicating the particular user is not Silver qualified, the SP makes a new request without a RequestedAuthnContext element, resulting in a lower LOA authentication. Ideally the user will not be prompted to authenticate a second time for this second request by the SP, i.e., the IdP has set a cookie in the user's browser.

For IdPs that are not Silver-capable according to metadata, the SP may choose to not include a SAML RequestedAuthnContext element, to avoid possible compatibility issues.

Examples:

  • CILogon

UC3: SP Prefers Bronze

...

Examples:

  • Research.Gov
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