Attribute Value Filters

While each policy defines what principal attributes may be allowed for a given service, there are optional attribute filters that can be set per policy to further weed out attributes based on their values.

Chaining Filters

Attribute filters can be chained together so as to associate multiple filters with a single service definition.

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{
  "@class" : "org.apereo.cas.services.RegexRegisteredService",
  "serviceId" : "sample",
  "name" : "sample",
  "id" : 200,
  "description" : "sample",
  "attributeReleasePolicy" : {
    "@class" : "org.apereo.cas.services.ReturnAllowedAttributeReleasePolicy",
    "attributeFilter" : {
      "@class" : "org.apereo.cas.services.support.RegisteredServiceChainingAttributeFilter",
      "filters": [ "java.util.ArrayList",
        [
            {
              "@class" : "org.apereo.cas.services.support.RegisteredServiceRegexAttributeFilter",
              "pattern" : "^\\w{3}$",
              "order": 10
            },
            {
              "@class" : "..."
            }
        ]
      ]
    },
    "allowedAttributes" : [ "java.util.ArrayList", [ "uid", "groupMembership" ] ]
  }
}

Chained attribute filters are sorted given their order property first before execution.

Regex

The regex filter that is responsible to make sure only attributes whose value matches a certain regex pattern are released.

Suppose that the following attributes are resolved:

Name Value
uid jsmith
groupMembership std
cn JohnSmith

The following configuration for instance considers the initial list of uid, groupMembership and then only allows and releases attributes whose value’s length is 3 characters. Therefor, out of the above list, only groupMembership is released to the application.

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{
  "@class" : "org.apereo.cas.services.RegexRegisteredService",
  "serviceId" : "sample",
  "name" : "sample",
  "id" : 200,
  "description" : "sample",
  "attributeReleasePolicy" : {
    "@class" : "org.apereo.cas.services.ReturnAllowedAttributeReleasePolicy",
    "attributeFilter" : {
      "@class" : "org.apereo.cas.services.support.RegisteredServiceRegexAttributeFilter",
      "pattern" : "^\\w{3}$"
    },
    "allowedAttributes" : [ "java.util.ArrayList", [ "uid", "groupMembership" ] ]
  }
}

Mapped Regex

The regex filter that is responsible to make sure only a selected set of attributes whose value matches a certain regex pattern are released. The filter selectively applies patterns to attributes mapped in the configuration. If an attribute is mapped, it is only allowed to be released if it matches the linked pattern. If an attribute is not mapped, it may optionally be excluded from the released set of attributes.

For example, the below example only allows release of memberOf if it contains a value that is 3 characters in length. If no values are found, the memberOf is excluded from the final released bundle.

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{
  "@class" : "org.apereo.cas.services.RegexRegisteredService",
  "serviceId" : "sample",
  "name" : "sample",
  "id" : 200,
  "description" : "sample",
  "attributeReleasePolicy" : {
    "@class" : "org.apereo.cas.services.ReturnAllowedAttributeReleasePolicy",
    "attributeFilter" : {
      "@class": "org.apereo.cas.services.support.RegisteredServiceMappedRegexAttributeFilter",
      "patterns": {
          "@class" : "java.util.TreeMap",
          "memberOf": "^\\w{3}$"
      },
      "excludeUnmappedAttributes": false,
      "completeMatch": false,
      "caseInsensitive": true,
      "order": 0
    },
    "allowedAttributes" : [ "java.util.ArrayList", [ "uid", "memberOf" ] ]
  }
}

The following fields are supported by this filter:

Name Description
patterns A map of attributes and their associated pattern tried against value(s).
completeMatch Indicates whether pattern-matching should execute over the entire value region.
excludeUnmappedAttributes Indicates whether unmapped attributes should be removed from the final bundle.
caseInsensitive Indicates whether pattern matching should be done in a case-insensitive manner.

Reverse Mapped Regex

Identical to the Mapped Regex filter, except that the filter only allows a selected set of attributes whose value does not match a certain regex pattern are released.

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{
  "@class" : "org.apereo.cas.services.RegexRegisteredService",
  "serviceId" : "sample",
  "name" : "sample",
  "id" : 200,
  "description" : "sample",
  "attributeReleasePolicy" : {
    "@class" : "org.apereo.cas.services.ReturnAllowedAttributeReleasePolicy",
    "attributeFilter" : {
      "@class": "org.apereo.cas.services.support.RegisteredServiceReverseMappedRegexAttributeFilter",
      "patterns": {
          "memberOf": "^\\w{3}$"
      },
      "excludeUnmappedAttributes": false,
      "completeMatch": false,
      "caseInsensitive": true,
      "order": 0
    },
    "allowedAttributes" : [ "java.util.ArrayList", [ "uid", "memberOf" ] ]
  }
}

Mutant Mapped Regex

This filter structurally, in terms of settings and properties, is identical to the Mapped Regex filter. Its main ability is to filter attribute values by a collection of patterns and then supplant the value dynamically based on the results of the regex match.

For example, the following definition attempts to filter all values assigned to the attribute memberOf based on the given patterns. Each pattern is linked via -> to the expected return value that may reference specific groups in the produced regex result. Assuming the attribute memberOf has values of math101 and marathon101, the filter will produce values courseA-athon101 and courseB-h101 after processing.

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{
  "@class" : "org.apereo.cas.services.RegexRegisteredService",
  "serviceId" : "sample",
  "name" : "sample",
  "id" : 200,
  "description" : "sample",
  "attributeReleasePolicy" : {
    "@class" : "org.apereo.cas.services.ReturnAllowedAttributeReleasePolicy",
    "attributeFilter" : {
      "@class": "org.apereo.cas.services.support.RegisteredServiceMutantRegexAttributeFilter",
      "patterns": {
          "@class" : "java.util.TreeMap",
          "memberOf": [ "java.util.ArrayList", [ "^mar(.+)(101) -> courseA-$1$2", "^mat(.+)(101) -> courseB-$1$2" ] ]
      },
      "excludeUnmappedAttributes": false,
      "completeMatch": false,
      "caseInsensitive": true,
      "order": 0
    },
    "allowedAttributes" : [ "java.util.ArrayList", [ "uid", "memberOf" ] ]
  }
}

Groovy

Attribute value filtering may also be carried out using an inline or external Groovy script. Scripts have access to the current resolved attributes via attributes and a logger. The returned result of the script must be a Map<String, Object>.

Inlined Groovy

An inline groovy filter allows you to embed the script directly in the service definition.

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{
  "@class" : "org.apereo.cas.services.RegexRegisteredService",
  "serviceId" : "sample",
  "name" : "sample",
  "id" : 200,
  "description" : "sample",
  "attributeReleasePolicy" : {
    "@class" : "org.apereo.cas.services.ReturnAllowedAttributeReleasePolicy",
    "attributeFilter" : {
      "@class" : "org.apereo.cas.services.support.RegisteredServiceScriptedAttributeFilter",
      "script" : "groovy { return attributes }"
    },
    "allowedAttributes" : [ "java.util.ArrayList", [ "uid", "groupMembership" ] ]
  }
}

External Groovy

An external groovy filter allows you to define the script in file located outside of the CAS web application.

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{
  "@class" : "org.apereo.cas.services.RegexRegisteredService",
  "serviceId" : "sample",
  "name" : "sample",
  "id" : 200,
  "description" : "sample",
  "attributeReleasePolicy" : {
    "@class" : "org.apereo.cas.services.ReturnAllowedAttributeReleasePolicy",
    "attributeFilter" : {
      "@class" : "org.apereo.cas.services.support.RegisteredServiceScriptedAttributeFilter",
      "script" : "file:/etc/cas/filter-this.groovy"
    },
    "allowedAttributes" : [ "java.util.ArrayList", [ "uid", "groupMembership" ] ]
  }
}

The outline of the script may be as follows:

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import java.util.*

def run(final Object... args) {
    def attributes = args[0]
    def logger = args[1]

    logger.info "Attributes currently resolved: ${attributes}"
    def map =...
    return map
}

The parameters passed are as follows:

Parameter Description
attributes A Map of current attributes resolved from sources.
logger The object responsible for issuing log messages such as logger.info(...).