APEREO CASDocumentation

Enterprise Authentication for All Earthlings and Beyond

Identity, Single Sign-On and Access Management
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Surrogate Authentication

Surrogate authentication (impersonation), sometimes known as sudo for the web, is the ability to authenticate on behalf of another user.

The two actors in this case are:

  1. The primary admin user whose credentials are verified upon authentication.
  2. The surrogate user, selected by the admin, to which CAS will switch after credential verification and is one that is linked to the single sign-on session.

Example use cases for impersonation include:

  1. Logging into an application on behalf of a user to execute and make changes.
  2. Troubleshoot a bothersome authentication experience with an application on behalf of another user.

Surrogate authentication is enabled by including the following dependencies in the WAR overlay:

Show in CAS Initializr Generate CAS Server WAR Overlay 


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<dependency>
    <groupId>org.apereo.cas</groupId>
    <artifactId>cas-server-support-surrogate-webflow</artifactId>
    <version>${cas.version}</version>
</dependency>





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implementation "org.apereo.cas:cas-server-support-surrogate-webflow:${project.'cas.version'}"





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dependencyManagement {
    imports {
        mavenBom "org.apereo.cas:cas-server-support-bom:${project.'cas.version'}"
    }
}

dependencies {
    implementation "org.apereo.cas:cas-server-support-surrogate-webflow"
}





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dependencies {
    /*
        The following platform references are included automatically and are listed for reference only.

        implementation enforcedPlatform("org.apereo.cas:cas-server-support-bom:${project.'cas.version'}")
        implementation platform(org.springframework.boot.gradle.plugin.SpringBootPlugin.BOM_COORDINATES)
        
    */
    implementation "org.apereo.cas:cas-server-support-surrogate-webflow"
}

Configuration

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

cas.authn.surrogate.core.principal-attribute-namesImpersonation can be authorized for all primary users/subjects carrying specific attributes with a predefined matching value specified via #principalAttributeValues .
no default

Impersonation can be authorized for all primary users/subjects carrying specific attributes with a predefined matching value specified via #principalAttributeValues. Needless to say, the attributes need to have been resolved for the primary principal prior to this step. Matching and comparison operations are case insensitive.

Type
List<String>
Default
none
Defined by
SurrogateCoreAuthenticationProperties
cas.authn.surrogate.core.principal-attribute-valuesThe regular expression that is cross matched against the principal attribute to determine if the account is authorized for impersonation.
no default
Regex

The regular expression that is cross matched against the principal attribute to determine if the account is authorized for impersonation. Matching and comparison operations are case insensitive.

Type
List<String>
Default
none
Defined by
SurrogateCoreAuthenticationProperties
cas.authn.surrogate.core.separatorThe separator character used to distinguish between the surrogate account and the admin/primary account.
+

The separator character used to distinguish between the surrogate account and the admin/primary account. For example, if you are casuser and you need to switch to jsmith as the surrogate (impersonated) user, the username provided to CAS would be jsmith+casuser.

Type
String
Default
+
Defined by
SurrogateCoreAuthenticationProperties

Required settings may be needed to activate or affect the feature; review them even when they have a default. Optional settings only need to be set to change a default or to turn on the behavior they control. Third party settings belong to libraries such as Spring Boot that CAS builds on; their own documentation may have more detail.

Notes on configuration

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, especially 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.

Account Storage

The following account stores may be configured and used to locate surrogates authorized for a particular user.

Storage Description
Simple See this guide.
JSON See this guide.
LDAP See this guide.
JDBC See this guide.
REST See this guide.
Groovy See this guide.
Custom See this guide.

Note that multiple account stores may be combined and can function simultaneously together to locate accounts from different stores.

Account Selection

Please see this guide.

Session Expiration

Please see this guide.

Surrogate Attributes

Upon a successful surrogate authentication event, the following attributes are communicated back to the application in order to detect an impersonation session:

Attribute Instructions
surrogateEnabled Boolean to indicate whether session is impersonated.
surrogatePrincipal The admin user whose credentials are validated and acts as the impersonator.
surrogateUser The surrogate user that is impersonated.

Surrogate Access Strategy

Please see this guide.

Surrogate Audits

Please see this guide.

Surrogate Principal Resolution

Please see this guide.

Actuator Endpoints

The following endpoints are provided by CAS:

impersonation
CAS endpoint1 operationNot exposed by default
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Turn the endpoint on and expose it over the web. One entry covers every operation. By default only info, health and status are exposed.



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management.endpoint.impersonation.access=UNRESTRICTED
management.endpoints.web.exposure.include=impersonation

Endpoints may be mapped to other paths. For example, to serve health at healthcheck:



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management.endpoints.web.path-mapping.health=healthcheck

REST Protocol

The feature extends the CAS REST API communication model to surrogate authentication, allowing REST credentials to specify a substitute and authenticate on behalf of another user. To activate surrogate authentication for the CAS REST API, you will need to choose one of the following options:

  • Format the credential username using the following syntax:


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[surrogate-userid][separator][primary-userid]
  • Pass along a special request header X-Surrogate-Principal that contains the surrogate userid.