The ComputedId data connector generates an attribute from the (usually SHA-1) digest of the requesting entityID, an attribute value, and a salt that must be kept secret to prevent off-line generation of the hashes to recover the underlying attribute value.

The attribute value is therefore opaque and unique per user, per relying party, suitable for use as a SAML "persistent" NameID or "pairwise-id" Subject Attribute.

Schema Name and Location

This xsi:type is defined by the urn:mace:shibboleth:2.0:resolver schema^3.3, located at http://shibboleth.net/schema/idp/shibboleth-attribute-resolver.xsd

Prior to V3.3 supplied plugins were defined by a schema type (xsi:type) in the urn:mace:shibboleth:2.0:resolver:dc namespace, the schema for which is located at http://shibboleth.net/schema/idp/shibboleth-attribute-resolver-dc.xsd. This is still supported, but every element or type in the urn:mace:shibboleth:2.0:resolver:dc namespace has an equivalently named (but not necessarily identical) version in the urn:mace:shibboleth:2.0:resolver namespace. The use of the urn:mace:shibboleth:2.0:resolver namespace also allows a relaxation of the ordering requirements of child elements to reduce strictness.\

Reference

Attributes

Any of the common attributes can be specified. In addition the following attributes are supported:

Name	Type	Default	Description
generatedAttributeID	string	ID of the connector	The id of the IdPAttribute that is generated
`sourceAttributeID`	string		DEPRECATED in V3.4 The id of the IdPAttribute used as input to the computed ID, required for older versions
`salt`	string. required		A salt, of at least 16 bytes, used in the computed ID
`encoding`^3.3.2	string	BASE64	Controls the eventual text encoding of the value, this should be set to "BASE32" for new deployments (see the warning box about case sensitivity under PersistentNameIDGenerationConfiguration)
`algorithm` ^3.4	string	SHA	Controls the digest algorithm applied

Configuring salt prior to V3.3

Prior to release 3.3 the parser mishandled the provided salt and stripped trailing and leading spaces from it, see case IDP-982. This rendered the values incompatible with those used in V2.

A workaround is to indirect through a property: for instance:

Attribute-resolver.xml:

<DataConnector id="computed" xsi:type="ComputedId" 
	sourceAttributeID="theSourceRemainsTheSame"
	generatedAttributeID="Foo"
	salt="%{idp.persistentId.salt}">

idp.properties

idp.persistentId.salt = String with Spaces before and after

Child Elements

Any of the common child elements can be specified.

Examples

The example produces a hashed value using an input value "Foo" from a DataConnector named "DataSourceForFoo".

<DataConnector id="ComputedIDConnector" xsi:type="ComputedId" 
	generatedAttributeID="ComputedID"
	salt="abcdefghijklmnopqrstuvwxyz"
	encoding="BASE32">

	<InputDataConnector ref="DataSourceForFoo" attributeNames="Foo" />

</DataConnector>

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