Attribute Definitions

The definition of an attribute in CAS, when fetched and resolved from an authentication or attribute repository source, tends to be defined and referenced using its name without any additional metadata or decorations. For example, you may wish to retrieve a uid attribute and virtually rename and map it to a userIdentifier attribute either globally or for specific application integrations. For most use cases, this configuration works quite comfortably and yet, depending on the nature of the target application and the authentication protocol used to complete the integration, additional requirements could be imposed and may have to be specified to define an attribute with additional pointers, when shared and released with a relying party. For example, a SAML2 service provider may require a scoped attribute for an eduPersonPrincipalName whose value is always determined from the uid attribute with a special friendly-name that is always provided regardless of the target application.

While bits and pieces of metadata about a given attribute can be defined either globally in CAS configuration settings or defined inside a service definition, an attribute definition store allows one to describe metadata about necessary attributes with special decorations to be considered during attribute resolution and release. The specification of the attribute definition store is entirely optional and the store may not contain any attribute definitions.

The following settings and properties are available from the CAS configuration catalog:

The configuration settings listed below are tagged as Required in the CAS configuration metadata. This flag indicates that the presence of the setting may be needed to activate or affect the behavior of the CAS feature and generally should be reviewed, possibly owned and adjusted. If the setting is assigned a default value, you do not need to strictly put the setting in your copy of the configuration, but should review it nonetheless to make sure it matches your deployment expectations.

  • cas.authn.attribute-repository.attribute-definition-store.json.location=

    • The location of the resource. Resources can be URLs, or files found either on the classpath or outside somewhere in the file system.

    In the event the configured resource is a Groovy script, specially if the script set to reload on changes, you may need to adjust the total number of inotify instances. On Linux, you may need to add the following line to /etc/sysctl.conf: fs.inotify.max_user_instances = 256.

    You can check the current value via cat /proc/sys/fs/inotify/max_user_instances.

    In situations and scenarios where CAS is able to automatically watch the underlying resource for changes and detect updates and modifications dynamically, you may be able to specify the following setting as either an environment variable or system property with a value of false to disable the resource watcher: org.apereo.cas.util.io.PathWatcherService.

    org.apereo.cas.configuration.model.SpringResourceProperties.

    How can I configure this property?

    The configuration settings listed below are tagged as Optional in the CAS configuration metadata. This flag indicates that the presence of the setting is not immediately necessary in the end-user CAS configuration, because a default value is assigned or the activation of the feature is not conditionally controlled by the setting value. In other words, you should only include this field in your configuration if you need to modify the default value or if you need to turn on the feature controlled by the setting.

    Configuration Metadata

    The collection of configuration properties listed in this section are automatically generated from the CAS source and components that contain the actual field definitions, types, descriptions, modules, etc. This metadata may not always be 100% accurate, or could be lacking details and sufficient explanations.

    Be Selective

    This section is meant as a guide only. Do NOT copy/paste the entire collection of settings into your CAS configuration; rather pick only the properties that you need. Do NOT enable settings unless you are certain of their purpose and do NOT copy settings into your configuration only to keep them as reference. All these ideas lead to upgrade headaches, maintenance nightmares and premature aging.

    YAGNI

    Note that for nearly ALL use cases, declaring and configuring properties listed here is sufficient. You should NOT have to explicitly massage a CAS XML/Java/etc configuration file to design an authentication handler, create attribute release policies, etc. CAS at runtime will auto-configure all required changes for you. If you are unsure about the meaning of a given CAS setting, do NOT turn it on without hesitation. Review the codebase or better yet, ask questions to clarify the intended behavior.

    Naming Convention

    Property names can be specified in very relaxed terms. For instance cas.someProperty, cas.some-property, cas.some_property are all valid names. While all forms are accepted by CAS, there are certain components (in CAS and other frameworks used) whose activation at runtime is conditional on a property value, where this property is required to have been specified in CAS configuration using kebab case. This is both true for properties that are owned by CAS as well as those that might be presented to the system via an external library or framework such as Spring Boot, etc.

    :information_source: Note

    When possible, properties should be stored in lower-case kebab format, such as cas.property-name=value. The only possible exception to this rule is when naming actuator endpoints; The name of the actuator endpoints (i.e. ssoSessions) MUST remain in camelCase mode.

    Settings and properties that are controlled by the CAS platform directly always begin with the prefix cas. All other settings are controlled and provided to CAS via other underlying frameworks and may have their own schemas and syntax. BE CAREFUL with the distinction. Unrecognized properties are rejected by CAS and/or frameworks upon which CAS depends. This means if you somehow misspell a property definition or fail to adhere to the dot-notation syntax and such, your setting is entirely refused by CAS and likely the feature it controls will never be activated in the way you intend.

    Validation

    Configuration properties are automatically validated on CAS startup to report issues with configuration binding, specially if defined CAS settings cannot be recognized or validated by the configuration schema. Additional validation processes are also handled via Configuration Metadata and property migrations applied automatically on startup by Spring Boot and family.

    Indexed Settings

    CAS settings able to accept multiple values are typically documented with an index, such as cas.some.setting[0]=value. The index [0] is meant to be incremented by the adopter to allow for distinct multiple configuration blocks.

    JSON Attribute Definitions

    Attribute definitions may be defined inside a JSON file whose location is provided via CAS settings. The structure of the JSON file may match the following:

    

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    {
    "@class" : "java.util.TreeMap",
    "employeeId" : {
      "@class" : "org.apereo.cas.authentication.attribute.DefaultAttributeDefinition",
      "key" : "employeeId",
      "scoped" : true,
      "attribute" : "empl_identifier"
    }
}

    Generally-speaking, attribute definitions are specified using a Map whose key is the attribute name, as resolved by the CAS attribute resolution engine. The attribute name as the key to the Map must match the key attribute of the attribute definition itself. If the attribute in question is not already resolved as principal attribute with a valid set of values, it might be possible, depending on the attribute release policy, to resolve and create that attribute on the fly as an attribute definition that can produce values.

    :information_source: Authorization

    Please note that as of this writing, attribute definitions cannot be used to drive authorization decisions via the likes of RBAC. Such definitions are typically evaluated during the attribute release phase which is too late for authorization decisions. If you need to produce attributes specifically for authorization decisions, consider defining a specific attribute repository which would be evaluated during the attribute resolution phase instead.

    The following settings can be specified by an attribute definition:

    Name Description
    key Attribute name, as resolved by the CAS attribute resolution engine.
    name Comma-separated list of attribute name(s) to virtually rename/remap and share with the target application during attribute release.
    scoped (Optional) If true, the attribute value will be scoped to the scope of the CAS server deployment defined in settings.
    encrypted (Optional) If true, the attribute value will be encrypted and encoded in base-64 using the service definition’s defined public key.
    attribute (Optional) The source attribute to provide values for the attribute definition itself, replacing that of the original source.
    patternFormat (Optional) Template used in a java.text.MessageFormat to decorate the attribute values.
    script (Optional) Groovy script, external or embedded to process and produce attributes values. This field supports the Spring Expression Language syntax.
    canonicalizationMode (Optional) Control transformation of attribute values; allowed values are UPPER, LOWER or NONE.
    patterns (Optional) A map of regular expression patterns to static/dynamic constructs to build values, in scenarios where the attribute definition is built off of an existing attribute.
    flattened (Optional) Indicate whether attribute definitions with multiple values should be flattened into a single value, separated by the assigned delimiter.

    The following operations in the order given should take place, if an attribute definition is to produce values:

    • Produce attribute values based on the attribute setting specified in the attribute definition, if any.
    • Produce attribute values based on the script setting specified in the attribute definition, if any.
    • Produce attribute values based on the patterns setting specified in the attribute definition, if any.
    • Produce attribute values based on the scoped setting specified in the attribute definition, if any.
    • Produce attribute values based on the patternFormat setting specified in the attribute definition, if any.
    • Produce attribute values based on the encrypted setting specified in the attribute definition, if any.
    • Produce attribute values based on the canonicalizationMode setting specified in the attribute definition, if any.
    • Produce attribute values based on the flattened setting specified in the attribute definition, if any.

    • Define an attribute definition for employeeId to produce scoped attributes based on another attribute empl_identifier as the source:

      

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      {
    "@class" : "java.util.TreeMap",
    "employeeId" : {
      "@class" : "org.apereo.cas.authentication.attribute.DefaultAttributeDefinition",
      "key" : "employeeId",
      "scoped" : true,
      "attribute" : "empl_identifier"
    }
}

      Now that the definition is available globally, the attribute can then be released as usual with the following definition:

      

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      ...
  "attributeReleasePolicy" : {
    "@class" : "org.apereo.cas.services.ReturnAllowedAttributeReleasePolicy",
    "allowedAttributes" : [ "java.util.ArrayList", [ "employeeId" ] ]
  }
...

    • Same use case as above, except the attribute value will be encrypted and encoded using the service definition’s public key:

      

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      {
    "@class" : "java.util.TreeMap",
    "employeeId" : {
      "@class" : "org.apereo.cas.authentication.attribute.DefaultAttributeDefinition",
      "key" : "employeeId",
      "encrypted" : true,
      "attribute" : "empl_identifier"
    }
}

      The service definition should have specified a public key definition:

      

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      ...
  "publicKey" : {
    "@class" : "org.apereo.cas.services.RegisteredServicePublicKeyImpl",
    "location" : "classpath:public.key",
    "algorithm" : "RSA"
  }
...

      The keys can be generated via the following commands:

      

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      openssl genrsa -out private.key 1024
openssl rsa -pubout -in private.key -out public.key -inform PEM -outform DER
openssl pkcs8 -topk8 -inform PER -outform DER -nocrypt -in private.key -out private.p8

    • Define an attribute definition to produce values based on a pattern format:

      

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      {
    "@class" : "java.util.TreeMap",
    "eduPersonPrincipalName" : {
      "@class" : "org.apereo.cas.authentication.attribute.DefaultAttributeDefinition",
      "key" : "eduPersonPrincipalName",
      "name" : "urn:oid:1.3.6.1.4.1.5923.1.1.1.6",
      "friendlyName" : "eduPersonPrincipalName",
      "scoped" : true,
      "patternFormat": "hello,{0}",
      "attribute" : "uid"
    }
}

      If the resolved set of attributes are uid=[test1, test2] and the CAS server has a scope of example.org, the final values of eduPersonPrincipalName would be [hello,test1@example.org,hello,test2@example.org] released as urn:oid:1.3.6.1.4.1.5923.1.1.1.6 with a friendly name of eduPersonPrincipalName.

    • Same use case as above, except the attribute value be additional processed by an embedded Groovy script

      

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      {
    "@class" : "java.util.TreeMap",
    "eduPersonPrincipalName" : {
      "@class" : "org.apereo.cas.authentication.attribute.DefaultAttributeDefinition",
      "key" : "eduPersonPrincipalName",
      "name" : "urn:oid:1.3.6.1.4.1.5923.1.1.1.6",
      "friendlyName" : "eduPersonPrincipalName",
      "scoped" : true,
      "script": "groovy { logger.info(\" name: ${attributeName}, values: ${attributeValues} \"); return ['Hi', attributes['firstname']] }"
    }
}

      If the CAS server has a scope of example.org, the final values of eduPersonPrincipalName would be [Hi, casuser] released as urn:oid:1.3.6.1.4.1.5923.1.1.1.6 with a friendly name of eduPersonPrincipalName.

    • Same use case as above, except the attribute value be additionally processed by an external Groovy script:

      

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      {
    "@class" : "java.util.TreeMap",
    "eduPersonPrincipalName" : {
      "@class" : "org.apereo.cas.authentication.attribute.DefaultAttributeDefinition",
      "key" : "eduPersonPrincipalName",
      "name" : "urn:oid:1.3.6.1.4.1.5923.1.1.1.6",
      "friendlyName" : "eduPersonPrincipalName",
      "scoped" : true,
      "script": "file:/attribute-definitions.groovy"
    }
}

      The outline of the Groovy script should be defined as:

      

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      def run(Object[] args) {
    def (attributeName,attributeValues,logger,registeredService,attributes) = args
    logger.info("name: ${attributeName}, values: ${attributeValues}, attributes: ${attributes}")
    return ["Hello " + attributes['givenName']]
}

      If the CAS server has a scope of example.org, the final values of eduPersonPrincipalName would be [Hello casuser] released as urn:oid:1.3.6.1.4.1.5923.1.1.1.6 with a friendly name of eduPersonPrincipalName.

    • Define an attribute definition to produce values conditionally based on pattern matching rules. If the attribute definition is to build its values off of an existing resolved attribute, each available value is examined against patterns defined here in the patterns map. For each match, the linked entry is used to determine the attribute definition value, either statically or dynamically which is typically an inlined Groovy script. If a pattern match is not found, then the value is skipped.

      

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      {
    "@class" : "java.util.TreeMap",
    "memberships" : {
        "@class" : "org.apereo.cas.authentication.attribute.DefaultAttributeDefinition",
        "key": "memberships",
        "attribute" : "memberships",
        "name": "affiliations",
        "patterns" : {
          "@class" : "java.util.TreeMap",
          "m[0-2].*" : "admins",
          "m[3-6].*" : "groovy { return 'users' }"
        }
    }
}

      The above snippet builds an attribute definition, memberships, that is ultimately encoded and released to applications under the name affiliations. The attribute values for this definition are sourced from the memberships attribute that must be made available to CAS. Each value is examined against the patterns defined and on a successful match, the linked construct will be evaluated to determine the final value.

      For example, if the resolved set of attributes are memberships=[m1, m2, m3, m4, m9], the final values of memberships would be [admins,users] which would then be released under the name affiliations.

    • If the collection of attributes values assembled for the attribute definition ultimately contain more than one value, the attribute definition may be instructed to flatten all values using the given delimiter character into a single value.

      

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      {
    "@class" : "java.util.TreeMap",
    "allgroups" : {
        "@class" : "org.apereo.cas.authentication.attribute.DefaultAttributeDefinition",
        "key": "allgroups",
        "attribute" : "memberships",
        "flattened": "/"
    }
}

      For example, if the resolved set of attributes are memberships=[m1, m2, m3, m4, m9], the final values of memberships would be m1/m2/m3/m4.

    Custom Attribute Definitions

    You may design and inject your own attribute definitions dynamically with CAS. First, you will need to design a @AutoConfiguration class to contain your own AttributeDefinitionStoreConfigurer implementation:

    

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    @AutoConfiguration
public class MyConfiguration {

    @Bean
    public AttributeDefinitionStoreConfigurer myAttributeDefinitionStore() {
        ...
    }
}

    Your configuration class needs to be registered with CAS. See this guide for better details.