DRAFT - Guidance for IdPs - DRAFT

Preparing IdP Metadata

To reduce user confusion and frustration, R&S SPs will provide a detailed error page with specific instructions in the event the user is returned to the SP without sufficient attributes. In particular, the SP will direct the user to the administrative contact at the IdP. Thus administrative contact information in IdP metadata is essential information in our effort to reduce manual boarding processes at the SP.

The IdP can short-circuit such an error page simply by including an errorURL in metadata. This gives the IdP the ability to own this problem by documenting (on the error page) and supporting whatever error handling process it desires.

Configuring a Shibboleth IdP to Release Attributes to an R&S SP

An IdP releases attributes to any R&S SP (identified by an entity attribute), not specific SPs (identified by entityID). In effect, an attribute release policy is configured once and for all R&S SPs.

An IDP can choose between possible configurations, depending on its policy needs:

1. Always release the same set of attributes to every R&S SP.
2. For each SP, only release those attributes that the SP requests via its metadata element.

Always Release the Same Set of Attributes

There is only step:

1. Configure a new <AttributeFilterPolicy> element for R&S SPs.

Only Release Those Attributes that the SP Requests

There are two steps to configure a new attribute release policy for R&S SPs:

1. Install and configure a general-purpose plugin that limits attribute release to the <md:RequestedAttribute> elements in SP metadata.
2. Configure a new <AttributeFilterPolicy> element for R&S SPs.

These two configuration steps taken together constrain the release of attributes to precisely those requested by R&S SPs (which are necessarily a subset of the R&S attribute bundle).

Install and Configure the Plugin

The uApprove addon to the Shibboleth IdP includes a plugin that limits attribute release to the <md:RequestedAttribute> elements in SP metadata.

To install and configure the plugin, perform the following steps:

1. Download and unpack the uApprove package
2. Copy the IdP plugin to your IdP build directory:
   
   $ cp $UAPPROVE_INSTALL$/idp-plugin-2.2.1/lib/* $IDP_INSTALL$/lib/
3. Rebuild the IdP
4. Add the namespace declaration xmlns:ua="http://www.switch.ch/aai/idp/uApprove/mf" to the root <AttributeFilterPolicyGroup> element.
5. Add the following at the end of the whitespace delimited list of values for the xsi:schemaLocation attribute:http://www.switch.ch/aai/idp/uApprove/mf classpath:/schema/uApprove-mf.xsd.

The plugin adds a new PermitValueRule of type ua:AttributeInMetadata.

Configure a New AttributeFilterPolicy

The following configuration requires Shibboleth IdP v2.3.4 or later, which fully supports using entity attributes in SP metadata as part of an attribute release filter policy.

The following IdP configuration implicitly releases attributes to any R&S SP. An attribute is released if and only if it is listed in SP metadata.

<AttributeFilterPolicy id="releaseToRandS">
  <PolicyRequirementRule xsi:type="saml:AttributeRequesterEntityAttributeExactMatch"
      attributeName="http://id.incommon.org/attribute/entity/category"
      attributeValue="research-and-scholarship"/>
  <AttributeRule attributeID="eduPersonPrincipalName">
    <PermitValueRule xsi:type="ua:AttributeInMetadata" onlyIfRequired="false"/>
  </AttributeRule>
  <AttributeRule attributeID="email">
    <PermitValueRule xsi:type="ua:AttributeInMetadata" onlyIfRequired="false"/>
  </AttributeRule>
  <AttributeRule attributeID="displayName">
    <PermitValueRule xsi:type="ua:AttributeInMetadata" onlyIfRequired="false"/>
  </AttributeRule>
  <AttributeRule attributeID="givenName">
    <PermitValueRule xsi:type="ua:AttributeInMetadata" onlyIfRequired="false"/>
  </AttributeRule>
  <AttributeRule attributeID="surName">
    <PermitValueRule xsi:type="ua:AttributeInMetadata" onlyIfRequired="false"/>
  </AttributeRule>
  <AttributeRule attributeID="eduPersonScopedAffiliation">
    <PermitValueRule xsi:type="ua:AttributeInMetadata" onlyIfRequired="false"/>
  </AttributeRule>
</AttributeFilterPolicy>

No other IdP implementation is known to support entity attributes in SP metadata.

Further Policy Controls

If a campus determines that it wants to block release of attributes for certain community members (e.g., students who have opted out under FERPA), IdP operators could create an additional attribute release policy to enforce this decision. An example is available on the Shibboleth wiki. IdP plugins, such as uApprove, that provide end-user control over attribute release may also be useful to satisfy additional controls.