This is preliminary documentation regarding an unreleased feature and the details may change prior to availability.
One of the challenges of dealing with interoperability issues with SPs is maintaining all the custom configuration rules needed to drive the IdP's behavior in all kinds of different ways. Traditionally most of these kinds of settings are concentrated in the relying-party.xml file and involve defining "overrides" for SPs or groups of SPs, often through manually maintained lists of entityIDs.
As discussed in the RelyingPartyConfiguration topic in the section on dynamically-driven configuration, V3.3 introduced an advanced capability to produce these settings on the fly at runtime, which creates opportunities for more flexible configuration, at some cost in complexity. One of the techniques currently described in that section involves the use of metadata "tags" (a shorthand name for the
<mdattr:EntityAttributes> extension feature) to embed signals in metadata that can drive configuration. In the longer term, any hope for a simplified approach to configuration or even a GUI probably rests on a strategy of this general type.
V3.4 introduces a built-in layer of code and Spring wiring to enable the use of the metadata-driven approach to configuration in a systematic way that provides a set of conventions for tag names and values to use to drive a significant range of configuration settings. With a small amount of up-front adjustment to the relying-party.xml file, it's possible to enable comprehensive support for metadata-driven configuration that can be freely intermixed in most cases with more static settings as required.
Bear in mind that enabling this feature requires a total degree of trust and control over one's sources of metadata, because the information in the metadata can have a wide-ranging degree of impact on the behavior of the IdP, by design. It essentially off-loads pieces of your configuration to the metadata, with all that that entails.
All of these new features are optional and are essentially a "working example" of how to use the already-available features provided with V3.3 to do something useful. It is expected at the time of writing that an unofficial plugin may be available prior to the release of V3.4 to enable the same example features in the V3.3 release.
Support for this feature has been added to the runtime environment in a way that avoids overhead (and risk) if not used but allows for straightforward enablement on a per-profile basis. The existing parent beans used for defining relying party defaults, overrides, and profile configurations all have analogs with a ".MDDriven" suffix in their names. Changing the existing parent bean name by adding the suffix and reloading the configuration will cause the runtime to evaluate most of the commonly-used configuration settings by checking for appropriately-named "tags" in the SP's metadata before falling back to the default, or statically configured, value if no tag is found.
For example, if you would like to enable tag-driven configuration for SAML 2.0 Browser SSO, you can replace any reference to the SAML2.SSO bean with SAML2.SSO.MDDriven, as in this example:
EntityAttribute / Property Convention
The "bridge" between the metadata and this feature is the naming and syntax of the tags used to control the configuration properties in the IdP. As an implementation strategy this could be "brute forced" with arbitrary mapping dictionaries, but the supplied implementation takes the approach of automating a mapping between the names of settings, the identifiers used internally for the various profiles, and the names of the corresponding SAML Attributes in metadata for those profile/setting combinations.
Each setting has a "base" name matching its Java bean property name as would be used if the setting were explicitly configured in Spring. For example, the property set via
p:defaultAuthenticationMethods is named "defaultAuthenticationMethods".
The corrsponding SAML Attribute for a setting is named by suffixing the "base" name of the setting to a profile URL that is defined by the Shibboleth software for each of the supported profiles.
The URLs are as follows:
|RelyingParty.MDDriven||RelyingPartyConfiguration||A template bean for use in defining metadata-driven RelyingParty overrides by hand|
|RelyingPartyByName.MDDriven||RelyingPartyConfiguration||A template bean for defining metadata-driven RelyingParty overrides based on matching by name|
|RelyingPartyByGroup.MDDriven||RelyingPartyConfiguration||A template bean for defining metadata-driven RelyingParty overrides based on matching by |
|RelyingPartyByTag.MDDriven||RelyingPartyConfiguration||A template bean for defining metadata-driven RelyingParty overrides based on matching |
|BrowserSSOProfileConfiguration||Default metadata-driven configuration for SAML 1.1 SSO profile|
|AttributeQueryProfileConfiguration||Default metadata-driven configuration for SAML 1.1 Attribute Query profile|
|ArtifactResolutionProfileConfiguration||Default metadata-driven configuration for SAML 1.1 Artifact Resolution profile|
|BrowserSSOProfileConfiguration||Default metadata-driven configuration for SAML 2.0 SSO profile|
|ECPProfileConfiguration||Default metadata-driven configuration for SAML 2.0 Enhanced Client/Proxy profile|
|SAML2.Logout.MDDriven||Default metadata-driven configuration for SAML 2.0 Single Logout profile|
|AttributeQueryProfileConfiguration||Default metadata-driven configuration for SAML 2.0 Attribute Query profile|
|ArtifactResolutionProfileConfiguration||Default metadata-driven configuration for SAML 2.0 Artifact Resolution profile|
|SSOSProfileConfiguration||Default metadata-driven configuration for Liberty ID-WSF Delegated SSO profile|
|CAS.LoginConfiguration.MDDriven||LoginConfiguration||Default metadata-driven configuration for CAS login prototol|
|CAS.ProxyConfiguration.MDDriven||ProxyConfiguration||Default metadata-driven configuration for CAS proxy login protocol|
|CAS.ValidateConfiguration.MDDriven||ValidateConfiguration||Default metadata-driven configuration for CAS ticket validation protocol|
|shibboleth.DefaultMDProfileAliases||List<String>||A built-in list of alternate URL "prefixes" to property names, this is used to automate the generation of property tag names that apply to all profiles at the same time.|
|shibboleth.MDProfileAliases||List<String>||An optional user-supplied list of additional URL prefixes to support custom property tag names|
|shibboleth.MDDrivenStringProperty||StringConfigurationLookupStrategy||Parent bean for defining new lookup strategies for string settings|
|shibboleth.MDDrivenBoolProperty||BooleanConfigurationLookupStrategy||Parent bean for defining new lookup strategies for boolean settings|
|shibboleth.MDDrivenIntProperty||IntegerConfigurationLookupStrategy||Parent bean for defining new lookup strategies for integer settings|
|shibboleth.MDDrivenLongProperty||LongConfigurationLookupStrategy||Parent bean for defining new lookup strategies for long integer settings|
|shibboleth.MDDrivenDoubleProperty||DoubleConfigurationLookupStrategy||Parent bean for defining new lookup strategies for double settings|
|shibboleth.MDDrivenDurationProperty||DurationConfigurationLookupStrategy||Parent bean for defining new lookup strategies for Duration settings|
|shibboleth.MDDrivenListProperty||ListConfigurationLookupStrategy||Parent bean for defining new lookup strategies for List settings|
|shibboleth.MDDrivenSetProperty||SetConfigurationLookupStrategy||Parent bean for defining new lookup strategies for Set settings|
|shibboleth.MDDrivenBeanProperty||BeanConfigurationLookupStrategy||Parent bean for defining new lookup strategies for arbitrary Spring bean settings|
Examples (In Progress)
Signed Assertions vs. Responses
Enabling signed assertions is advisedly handled by turning on
WantAssertionsSigned in metadata, but isn't always possible and sometimes has to be combined with disabling signed responses (or just for efficiency).
Setting idp.encryption.optional is usually a workaround for handling the majority of SPs without encryption support, but there are a couple of scenarios in which it's useful to be able to manually disable it. Some federations (InCommon for one) have limitations such that SPs without encryption support are stuck registering keys they don't support. Some SPs support encryption but build in time-bombs by forcing flag day key rotations on all IdPs that cause outages or manual work.
There are metadata extensions that are meant to be used to signal algorithm support, but they're not widely used at this point. The most common scenario is to force SHA-1 for older systems.
A common use case is enabling SAML 1 for legacy systems, often combined with either enabling queries or attribute push (to eliminate the queries).
NameID Format Exceptions
<NameIDFormat> elements in metadata (which can also be added at runtime with a filter) is the normal way to trigger them, but the "unspecified" Format has to be triggered with a profile setting. That's not common, but it's easy to define a tag for just in case. The problem is that any two SPs using it are only coincidentally going to want the same data, so this isn't solely a matter of format selection.
Some of the other profile settings are workarounds for bugs, e.g., omitting the NotBefore attribute. Likely not very common but easily tag-driven. We could also supply basic scripts for driving things like additional Audience values so the script would run based on a tag but the values would still be local to the script.
Handling SPs that require MFA but can't request it requires IdP-side configuration.
Attribute Release Consent
Triggering consent based on the SP is pretty common.
The authorization checking flow is another case, though the checking condition would probably to be extended for each different service/scenario.
Not relying-party-driven, but a canonical case for using metadata tagging is to drive attribute release, occasionally via bundles a la R&S and also piecemeal. FIltering is ultimately going to perform proportional to the number of policies times their individual overhead, so if tag-based rules are sufficiently fast, a policy per attribute would ultimately match or exceed the approach of defining policies per service.