U2F - FIDO Universal Authentication

U2F is an open authentication standard that enables internet users to securely access any number of online services, with one single device, instantly and with no drivers, or client software needed. The CAS U2F implementation is built on top of Yubico and the technical specifications are hosted by the open-authentication industry consortium known as the FIDO Alliance.

Note that not all browsers today support U2F. While support in recent versions of Chrome and Opera seem to exist, you should always verify that U2F support is available for your target browser.

Support is enabled by including the following module in the WAR overlay:



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<dependency>
    <groupId>org.apereo.cas</groupId>
    <artifactId>cas-server-support-u2f</artifactId>
    <version>${cas.version}</version>
</dependency>





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implementation "org.apereo.cas:cas-server-support-u2f:${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-u2f"
}





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dependencies {
    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-u2f"
}

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.u2f.core.bypass.groovy.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.

    org.apereo.cas.configuration.model.support.mfa.GroovyMultifactorAuthenticationProviderBypassProperties.
  • cas.authn.mfa.u2f.core.bypass.rest.url=

    • The endpoint URL to contact and retrieve attributes.

    org.apereo.cas.configuration.model.support.mfa.RestfulMultifactorAuthenticationProviderBypassProperties.
    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.

  • cas.authn.mfa.u2f.core.bypass.authentication-attribute-name=

    • Skip multifactor authentication based on designated authentication attribute names.

    org.apereo.cas.configuration.model.support.mfa.MultifactorAuthenticationProviderBypassProperties.
  • cas.authn.mfa.u2f.core.bypass.authentication-attribute-value=

    • Optionally, skip multifactor authentication based on designated authentication attribute values.

    org.apereo.cas.configuration.model.support.mfa.MultifactorAuthenticationProviderBypassProperties.
  • cas.authn.mfa.u2f.core.bypass.authentication-handler-name=

    • Skip multifactor authentication depending on form of primary authentication execution. Specifically, skip multifactor if the a particular authentication handler noted by its name successfully is able to authenticate credentials in the primary factor.

    org.apereo.cas.configuration.model.support.mfa.MultifactorAuthenticationProviderBypassProperties.
  • cas.authn.mfa.u2f.core.bypass.authentication-method-name=

    • Skip multifactor authentication depending on method/form of primary authentication execution. Specifically, skip multifactor if the authentication method attribute collected as part of authentication metadata matches a certain value.

    org.apereo.cas.configuration.model.support.mfa.MultifactorAuthenticationProviderBypassProperties.
  • cas.authn.mfa.u2f.core.bypass.credential-class-type=

    • Skip multifactor authentication depending on form of primary credentials. Value must equal the fully qualified class name of the credential type.

    org.apereo.cas.configuration.model.support.mfa.MultifactorAuthenticationProviderBypassProperties.
  • cas.authn.mfa.u2f.core.bypass.http-request-headers=

    • Skip multifactor authentication if the http request contains the defined header names. Header names may be comma-separated and can be regular expressions; values are ignored.

    This settings supports regular expression patterns. [?].

    org.apereo.cas.configuration.model.support.mfa.MultifactorAuthenticationProviderBypassProperties.
  • cas.authn.mfa.u2f.core.bypass.http-request-remote-address=

    • Skip multifactor authentication if the http request's remote address or host matches the value defined here. The value may be specified as a regular expression.

    This settings supports regular expression patterns. [?].

    org.apereo.cas.configuration.model.support.mfa.MultifactorAuthenticationProviderBypassProperties.
  • cas.authn.mfa.u2f.core.bypass.principal-attribute-name=

    • Skip multifactor authentication based on designated principal attribute names.

    org.apereo.cas.configuration.model.support.mfa.MultifactorAuthenticationProviderBypassProperties.
  • cas.authn.mfa.u2f.core.bypass.principal-attribute-value=

    • Optionally, skip multifactor authentication based on designated principal attribute values.

    org.apereo.cas.configuration.model.support.mfa.MultifactorAuthenticationProviderBypassProperties.
  • cas.authn.mfa.u2f.core.bypass.rest.basic-auth-password=

    • If REST endpoint is protected via basic authentication, specify the password for authentication.

    org.apereo.cas.configuration.model.support.mfa.RestfulMultifactorAuthenticationProviderBypassProperties.
  • cas.authn.mfa.u2f.core.bypass.rest.basic-auth-username=

    • If REST endpoint is protected via basic authentication, specify the username for authentication.

    org.apereo.cas.configuration.model.support.mfa.RestfulMultifactorAuthenticationProviderBypassProperties.
  • cas.authn.mfa.u2f.core.bypass.rest.headers=

    • Headers, defined as a Map, to include in the request when making the REST call. Will overwrite any header that CAS is pre-defined to send and include in the request. Key in the map should be the header name and the value in the map should be the header value.

    org.apereo.cas.configuration.model.support.mfa.RestfulMultifactorAuthenticationProviderBypassProperties.
  • cas.authn.mfa.u2f.core.bypass.rest.method=GET

    • HTTP method to use when contacting the rest endpoint. Examples include GET, POST, etc.

    org.apereo.cas.configuration.model.support.mfa.RestfulMultifactorAuthenticationProviderBypassProperties.
  • cas.authn.mfa.u2f.core.expire-devices=30

    • Expire and forget device registration records after this period.

    org.apereo.cas.configuration.model.support.mfa.u2f.U2FCoreMultifactorAuthenticationProperties.
  • cas.authn.mfa.u2f.core.expire-devices-time-unit=

    • Device registration record expiration time unit.

    org.apereo.cas.configuration.model.support.mfa.u2f.U2FCoreMultifactorAuthenticationProperties.
  • cas.authn.mfa.u2f.core.expire-registrations=30

    • Expire and forget device registration requests after this period.

    org.apereo.cas.configuration.model.support.mfa.u2f.U2FCoreMultifactorAuthenticationProperties.
  • cas.authn.mfa.u2f.core.expire-registrations-time-unit=

    • Device registration requests expiration time unit.

    org.apereo.cas.configuration.model.support.mfa.u2f.U2FCoreMultifactorAuthenticationProperties.
  • cas.authn.mfa.u2f.core.failure-mode=CLOSED

    • The failure mode policy for this MFA provider. The authentication policy by default supports fail-closed mode, which means that if you attempt to exercise a particular provider available to CAS and the provider cannot be reached, authentication will be stopped and an error will be displayed. You can of course change this behavior so that authentication proceeds without exercising the provider functionality, if that provider cannot respond. Each defined multifactor authentication provider can set its own failure mode policy. Failure modes set at this location will override the global failure mode, but defer to any failure mode set by the registered service. Available values are as follows:

    • OPEN: Disallow MFA, proceed with authentication but don't communicate MFA to the RP.
    • CLOSED: Disallow MFA, block with authentication.
    • PHANTOM: Disallow MFA, proceed with authentication and communicate MFA to the RP.
    • NONE: Do not check for failure at all.
    • UNDEFINED: The default one indicating that no failure mode is set at all.

    org.apereo.cas.configuration.model.support.mfa.u2f.U2FCoreMultifactorAuthenticationProperties.
  • cas.authn.mfa.u2f.core.id=

    • The identifier for the multifactor provider. In most cases, this need not be configured explicitly, unless multiple instances of the same provider type are configured in CAS.

    org.apereo.cas.configuration.model.support.mfa.u2f.U2FCoreMultifactorAuthenticationProperties.
  • cas.authn.mfa.u2f.core.name=

    • The name of the authentication handler used to verify credentials in MFA. Remember that if you have more than one authentication handler of the same type, the names must be defined uniquely for each authentication scheme. Failing to do so may force CAS to not register authentication handlers with a duplicate name.

    org.apereo.cas.configuration.model.support.mfa.u2f.U2FCoreMultifactorAuthenticationProperties.
  • cas.authn.mfa.u2f.core.order=

    • The order of the authentication handler in the chain.

    org.apereo.cas.configuration.model.support.mfa.u2f.U2FCoreMultifactorAuthenticationProperties.
  • cas.authn.mfa.u2f.core.rank=0

    • At times, CAS needs to determine the correct provider when step-up authentication is required. Consider for a moment that CAS already has established an SSO session with/without a provider and has reached a level of authentication. Another incoming request attempts to exercise that SSO session with a different and often competing authentication requirement that may differ from the authentication level CAS has already established. Concretely, examples may be:

    • CAS has achieved an SSO session, but a separate request now requires step-up authentication with DuoSecurity.
    • CAS has achieved an SSO session with an authentication level satisfied by DuoSecurity, but a separate request now requires step-up authentication with YubiKey.
    In certain scenarios, CAS will attempt to rank authentication levels and compare them with each other. If CAS already has achieved a level that is higher than what the incoming request requires, no step-up authentication will be performed. If the opposite is true, CAS will route the authentication flow to the required authentication level and upon success, will adjust the SSO session with the new higher authentication level now satisfied. Ranking of authentication methods is done per provider via specific properties for each. Note that the higher the rank value is, the higher on the security scale it remains. A provider that ranks higher with a larger weight value trumps and override others with a lower value.

    org.apereo.cas.configuration.model.support.mfa.u2f.U2FCoreMultifactorAuthenticationProperties.
  • cas.authn.mfa.u2f.core.trusted-device-enabled=false

    • Indicates whether this provider should support trusted devices.

    org.apereo.cas.configuration.model.support.mfa.u2f.U2FCoreMultifactorAuthenticationProperties.