Current File(s): conf/saml-nameid.xml, conf/saml-nameid.properties
Format: Native Spring / Deprecated Custom Schema
Legacy V2 File(s): conf/attribute-resolver.xml
Generation of SAML NameIdentifier/NameID content is handled by the NameIdentifierGeneration service. See the NameIdentifiers topic for a general discussion of name identifiers and a list of specific examples.
The saml-nameid.xml file is used to control the generation of SAML 1 NameIdentifier and SAML 2 NameID content. SAML assertion subjects contain a special slot for an identifier that is less commonly used in Shibboleth deployments (because SAML Attributes are more general and useful) but is very commonly used by vendors seeking to do the bare minimum necessary to support SAML.
When interoperating with Shibboleth SPs, it's rare to need to modify this file, but you might need to do so to add support for more application-oriented identifier types, such as email addresses, or to enable support for so-called "persistent" identifiers, special privacy-preserving identifiers that are targeted to specific services.
The configuration defines two list beans, each containing "generator" plugins for the appropriate SAML version. Each plugin is specific to an identifier Format, a SAML constant that identifies the kind of value being expressed. The generation process involves selecting a list of Formats to try and generate, and then attempting to generate each one until a value is obtained by running each configured generator in order.
The Format determination is based on combining the SP's request (SAML 2 requests can include a
<NameIDPolicy> element), the
<NameIDFormat> element(s) in the SP's metadata, and the
nameIDFormatPrecedence profile configuration property, if set for the matching relying party configuration. Default Formats are set via saml-nameid.properties and are used in the event that nothing else is called for.
The default configuration includes generators for "transient" identifiers. These plugins are configured using saml-nameid.properties to control the strategies used to generate and reverse-map the values (the latter being necessary for attribute queries, primarily).
In the case of SAML 2, a plugin is present, but commented out, to generate "persistent" identifiers. Certain properties in saml-nameid.properties must be set in order to safely uncomment this plugin (discussed below).
The default configuration also demonstrates how to generate a custom identifier using an arbitrary Format based on an attribute from the attribute resolution process. This mirrors the V2 approach of encoding attributes, but separates the two operations in the configuration. This plugin also has the capability, unlike the resolver-based approach, of selecting the first value present from a list of possible source attributes.
In summary, supporting "transient" identifiers is automatic. If you want "persistent" / pair-wise support, see below. If you want custom values based on an attribute, uncomment one or more copies of the example bean(s) appropriately and ensure the underlying source attribute(s) are released to the applicable relying party or parties.
Transient Identifier Generation
The strategy used to generate transient identifiers is controlled with the idp.transientId.generator property in saml-nameid.properties.
The default strategy is based on the use of a secret key, discussed in the SecurityConfiguration topic (see the idp.sealer.* properties). This maintains support for attribute queries without requiring shared state between a cluster of nodes, apart from sharing the secret key.
You can set this property to "shibboleth.StoredTransientIdGenerator" to generate random values tracked by server-side storage (this makes them shorter, but requires more complex storage approaches when clustering if attribute queries need to be supported).
Persistent Identifier Generation
The strategy used to generate persistent identifiers is controlled with the idp.persistentId.generator property in saml-nameid.properties.
The default strategy is a hash-based approach called "Computed" that avoids the need for a database to store the IDs, but is incapable of reverse-mapping a given identifier, or revoking or changing the identifier associated with a subject. Tracking back to a subject for debugging purposes generally involves the use of audit logs rather than direct access to a mapping of users. It's not the best approach in the abstract, but it is much simpler to deploy.
To enable the Computed strategy, you must set two properties:
- A list of attributes from which to derive a key for the subject. The key is used as the hash input, and should be a very stable value for each subject and must never be reassigned later to a different subject. Usually this should be a permanent serial number associated by an IDMS to each account, and not a name-based identifier like a login ID or email address. It must be released (in terms of attribute filter policy) to the relying party, but need not have any attribute encoders attached (which means it won't actually be visible to the relying party in the SAML response).
- A secret string used as a salt when hashing the subject key derived from the property above. This is required to prevent trivial attacks to determine the identifier for a given subject, and must be kept secret.
The alternative strategy is to generate simple random identifiers on first use and store them in a database for future use. This has significant benefits and addresses most of the limitations of the computed strategy, but requires a highly available database accessible to every IdP node. Using this strategy requires the above settings and requires changing the idp.persistentId.generator property to "shibboleth.StoredPersistentIdGenerator" and setting the idp.persistentId.store property to the name of a bean you must define. You can place it in saml-nameid.xml if you like. The main content of that bean is a reference to a JDBC DataSource object.
A mocked up example of a persistent store using MySQL and the DBCP pooling library follows:
It's possible to override the default table and column names used in the data store with properties on the JDBCPersistentIdStore class. The default DDL is designed to be compatible with the V2 data connector.
Lastly, a default feature of the stored strategy is that it uses the computed strategy to produce the initial identifier for each subject, to help with migration. If you don't need that to happen, you can set the idp.persistentId.computed property to an empty value.
Beans defined in saml-nameid.xml and related system configuration follow:
|SAML 2 NameID generator plugins to use|
|SAML 1 NameIdentifier generator plugins to use|
|Plugins for generating transient identifiers using pluggable strategies|
|shibboleth.StoredTransientIdGenerator||TransientIdGenerationStrategy||Strategy plugin that generates transient identifiers randomly and stores them in a server-side StorageService|
|shibboleth.CryptoTransientIdGenerator||TransientIdGenerationStrategy||Strategy plugin that generates transient identifiers by encrypting a subject identity into a long opaque string|
|shibboleth.SAML2PersistentGenerator||SAML2NameIDGenerator||Plugin for generating persistent identifiers using pluggable strategy|
|shibboleth.ComputedPersistentIdGenerator||PersistentIdGenerationStrategy||Strategy plugin that generates persistent identifiers with a salted hash of an input value|
|shibboleth.StoredPersistentIdGenerator||PersistentIdGenerationStrategy||Strategy plugin that generates persistent identifiers and stores them in a database|
|Template beans for plugins that generate custom identifiers based on resolved and released attribute values|
|Plugins supporting deprecated use of attribute resolver configuration to produce and encode name identifiers|
Properties are defined in saml-nameid.properties to customize various aspects of default identifier generation behavior:
|idp.transientId.generator||Bean ID of a TransientIdGenerationStrategy||shibboleth.CryptoTransientIdGenerator||Identifies the strategy plugin for generating transient IDs|
|idp.persistentId.generator||Bean ID of a PersistentIdGenerationStrategy||shibboleth.ComputedPersistentIdGenerator||Identifies the strategy plugin for generating persistent IDs|
|idp.persistentId.store||Bean ID of a PersistentIdStore||Identifies the data store when using a storage-based strategy for persistent IDs|
|idp.persistentId.computed||Bean ID of a ComputedPersistentIdGenerationStrategy||shibboleth.ComputedPersistentIdGenerator||May be null, Identifies a strategy plugin to use to generate the first persistent identifier for each subject, used to migrate from the computed to stored strategies|
|idp.persistentId.sourceAttribute||Comma-delim'd List||List of attributes to search for a value to uniquely identify the subject of a persistent identifier, it MUST be stable, long-lived, and non-reassignable|
|idp.persistentId.salt||String||A secret salt for the hash when using computed persistent IDs|
|idp.persistentId.algorithm||String||SHA||The hash algorithm used when using computed persistent IDs|
|idp.nameid.saml2.legacyGenerator||Bean ID||Identifies a default generator plugin to use as a last resort if no others succeed|
|idp.nameid.saml1.legacyGenerator||Bean ID||Identifies a default generator plugin to use as a last resort if no others succeed|
|idp.nameid.saml2.default||URI||urn:oasis:names:tc:SAML:2.0:nameid-format:transient||The default Format to generate if nothing else is indicated|
|idp.nameid.saml1.default||URI||urn:mace:shibboleth:1.0:nameIdentifier||The default Format to generate if nothing else is indicated|
The V3 IdP uses a new dedicated service for configuring NameID generation. The legacy V2 approach of encoding attributes into identifiers using attribute-resolver.xml and special attribute encoders that generate NameIdentifiers or NameIDs instead of Attributes is supported for compatibility purposes, but is deprecated and may be removed from a future version.
To enable the legacy support, the idp.nameid.saml2.legacyGenerator and idp.nameid.saml1.legacyGenerator properties must be uncommented and set to the values commented out in the saml-nameid.properties file. This is done for you when performing an upgrade from V2.
The IdP should load any existing V2 attribute-resolver.xml file and configure itself in an expected manner, but that configuration will be superseded by the content of the new saml-nameid.xml file and will fall back to the resolver only as a backstop. You can short-circuit the new functionality by commenting out the content of the two generator list beans and leaving them empty.
Note that unlike in V2, the transient or persistent identifiers produced by the new V3 generation service are not treated as attributes and are not release-controlled via an attribute filter policy. Rather, transients are viewed as harmless (because they are merely one-time values) and persistent identifiers cannot be generated without configuring an appropriate source attribute or other properties.
Finally, note that the two supplied strategies for generating persistent IDs are compatible with the connector plugins in V2 used for this purpose.