Multifactor Authentication Trusted Device/Browser

In addition to triggers that are provided by the MFA functionality of CAS, there may be cases where you wish to let the user decide if the current browser/device should be trusted so as to skip subsequent MFA requests. The objective is for CAS to remember that decision for a configurable period of time and not bother the user with MFA until the decision is either forcefully revoked or considered expired.

Trusting a device during an MFA workflow would mean that the ultimate decision is remembered for that user of that location of that device. These keys are combined together securely and assigned to the final decision.

Before deployment, you should consider the following:

  • Should users be optionally allowed to authorize the “current” device?
  • …or must that happen automatically once MFA is commenced?
  • How should user decisions and choices be remembered? Where are they stored?
  • How long should user decisions be trusted by CAS?
  • How is a trusted authentication session communicated back to an application?

Note that enabling this feature by default means it’s globally applied to all in the case if you have multiple MFA providers turned on. This can be optionally disabled and applied only to a selected set of providers.

Configuration

Support is provided via the following module:

implementation "org.apereo.cas:cas-server-support-trusted-mfa:${project.'cas.version'}"
<dependency>
  <groupId>org.apereo.cas</groupId>
  <artifactId>cas-server-support-trusted-mfa</artifactId>
  <version>${cas.version}</version>
</dependency>
dependencyManagement {
  imports {
    mavenBom "org.apereo.cas:cas-server-support-bom:${project.'cas.version'}"
  }
}

dependencies {  
  implementation "org.apereo.cas:cas-server-support-trusted-mfa"
}

Administrative Endpoints

The following endpoints are provided by CAS:

Endpoint Description
multifactorTrustedDevices Expose devices currently registered and trusted by the CAS multifactor authentication engine. A GET operation produces a list of all trusted devices. Specifying a username in the URL as the placeholder/selector will fetch devices registered for that user (i.e. multifactorTrustedDevices/{username}). A DELETE operation with a device key id will attempt to remove the trusted device (i.e. multifactorTrustedDevices/{id}).

Settings

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.mfa.trusted.crypto.encryption.key=
  • The encryption key is a JWT whose length is defined by the encryption key size setting.

  • cas.authn.mfa.trusted.crypto.signing.key=
  • The signing key is a JWT whose length is defined by the signing key size setting.

    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.