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:

1
2
3
4
5
<dependency>
    <groupId>org.apereo.cas</groupId>
    <artifactId>cas-server-support-trusted-mfa</artifactId>
    <version>${cas.version}</version>
</dependency>
1
implementation "org.apereo.cas:cas-server-support-trusted-mfa:${project.'cas.version'}"
1
2
3
4
5
6
7
8
9
dependencyManagement {
    imports {
        mavenBom "org.apereo.cas:cas-server-support-bom:${project.'cas.version'}"
    }
}

dependencies {
    implementation "org.apereo.cas:cas-server-support-trusted-mfa"
}
1
2
3
4
5
6
7
8
9
10
dependencies {
    /*
    The following platform references should be included automatically and are listed here 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-trusted-mfa"
}

Actuator Endpoints

The following endpoints are provided by CAS:

 Remove trusted device using its key.

 Remove expired trusted devices given an expiration date as a threshold.

 Remove all trusted devices that have expired.

 Get collection of trusted devices.

 Get collection of trusted devices for the user.

 Export all device records as a zip file for a given username.

 Export all device records as a zip file.

 Import a single trusted device record as a JSON document in the request body.


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.

    This setting supports the Spring Expression Language.

    org.apereo.cas.configuration.model.core.util.EncryptionJwtCryptoProperties.

    How can I configure this property?

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

    This setting supports the Spring Expression Language.

    org.apereo.cas.configuration.model.core.util.SigningJwtCryptoProperties.

    How can I configure this property?

  • cas.authn.mfa.trusted.device-fingerprint.cookie.crypto.encryption.key=
  • The encryption key is a JWT whose length is defined by the encryption key size setting.

    This setting supports the Spring Expression Language.

    org.apereo.cas.configuration.model.core.util.EncryptionJwtCryptoProperties.

    How can I configure this property?

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

    This setting supports the Spring Expression Language.

    org.apereo.cas.configuration.model.core.util.SigningJwtCryptoProperties.

    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.

  • cas.authn.mfa.trusted.crypto.alg=
  • The signing/encryption algorithm to use.

    org.apereo.cas.configuration.model.core.util.EncryptionJwtSigningJwtCryptographyProperties.

    How can I configure this property?

  • cas.authn.mfa.trusted.crypto.enabled=true
  • Whether crypto operations are enabled.

    org.apereo.cas.configuration.model.core.util.EncryptionJwtSigningJwtCryptographyProperties.

    How can I configure this property?

  • cas.authn.mfa.trusted.crypto.encryption.key-size=512
  • The encryption key size.

    org.apereo.cas.configuration.model.core.util.EncryptionJwtCryptoProperties.

    How can I configure this property?

  • cas.authn.mfa.trusted.crypto.signing.key-size=512
  • The signing key size.

    org.apereo.cas.configuration.model.core.util.SigningJwtCryptoProperties.

    How can I configure this property?

  • cas.authn.mfa.trusted.crypto.strategy-type=ENCRYPT_AND_SIGN
  • Control the cipher sequence of operations. The accepted values are:

    • ENCRYPT_AND_SIGN: Encrypt the value first, and then sign.
    • SIGN_AND_ENCRYPT: Sign the value first, and then encrypt.

    org.apereo.cas.configuration.model.core.util.EncryptionJwtSigningJwtCryptographyProperties.

    How can I configure this property?

  • cas.authn.mfa.trusted.device-fingerprint.cookie.crypto.alg=
  • The signing/encryption algorithm to use.

    org.apereo.cas.configuration.model.core.util.EncryptionJwtSigningJwtCryptographyProperties.

    How can I configure this property?

  • cas.authn.mfa.trusted.device-fingerprint.cookie.crypto.enabled=true
  • Whether crypto operations are enabled.

    org.apereo.cas.configuration.model.core.util.EncryptionJwtSigningJwtCryptographyProperties.

    How can I configure this property?

  • cas.authn.mfa.trusted.device-fingerprint.cookie.crypto.encryption.key-size=512
  • The encryption key size.

    org.apereo.cas.configuration.model.core.util.EncryptionJwtCryptoProperties.

    How can I configure this property?

  • cas.authn.mfa.trusted.device-fingerprint.cookie.crypto.signing.key-size=512
  • The signing key size.

    org.apereo.cas.configuration.model.core.util.SigningJwtCryptoProperties.

    How can I configure this property?

  • cas.authn.mfa.trusted.device-fingerprint.cookie.crypto.strategy-type=ENCRYPT_AND_SIGN
  • Control the cipher sequence of operations. The accepted values are:

    • ENCRYPT_AND_SIGN: Encrypt the value first, and then sign.
    • SIGN_AND_ENCRYPT: Sign the value first, and then encrypt.

    org.apereo.cas.configuration.model.core.util.EncryptionJwtSigningJwtCryptographyProperties.

    How can I configure this property?

  • cas.authn.mfa.trusted.core.authentication-context-attribute=isFromTrustedMultifactorAuthentication
  • If an MFA request is bypassed due to a trusted authentication decision, applications will receive a special attribute as part of the validation payload that indicates this behavior. Applications must further account for the scenario where they ask for an MFA mode and yet don’t receive confirmation of it in the response given the authentication session was trusted and MFA bypassed.

    org.apereo.cas.configuration.model.support.mfa.trusteddevice.TrustedDevicesMultifactorCoreProperties.

    How can I configure this property?

  • cas.authn.mfa.trusted.core.auto-assign-device-name=false
  • When device registration is enabled, indicate whether a device name should be automatically selected and assigned by CAS.

    org.apereo.cas.configuration.model.support.mfa.trusteddevice.TrustedDevicesMultifactorCoreProperties.

    How can I configure this property?

  • cas.authn.mfa.trusted.core.device-registration-enabled=true
  • Indicates whether CAS should ask for device registration consent or execute it automatically.

    org.apereo.cas.configuration.model.support.mfa.trusteddevice.TrustedDevicesMultifactorCoreProperties.

    How can I configure this property?

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

    This setting supports the Spring Expression Language.

    org.apereo.cas.configuration.model.core.util.EncryptionJwtCryptoProperties.

    How can I configure this property?

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

    This setting supports the Spring Expression Language.

    org.apereo.cas.configuration.model.core.util.SigningJwtCryptoProperties.

    How can I configure this property?

  • cas.authn.mfa.trusted.device-fingerprint.cookie.crypto.encryption.key=
  • The encryption key is a JWT whose length is defined by the encryption key size setting.

    This setting supports the Spring Expression Language.

    org.apereo.cas.configuration.model.core.util.EncryptionJwtCryptoProperties.

    How can I configure this property?

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

    This setting supports the Spring Expression Language.

    org.apereo.cas.configuration.model.core.util.SigningJwtCryptoProperties.

    How can I configure this property?

  • cas.authn.mfa.trusted.crypto.alg=
  • The signing/encryption algorithm to use.

    org.apereo.cas.configuration.model.core.util.EncryptionJwtSigningJwtCryptographyProperties.

    How can I configure this property?

  • cas.authn.mfa.trusted.crypto.enabled=true
  • Whether crypto operations are enabled.

    org.apereo.cas.configuration.model.core.util.EncryptionJwtSigningJwtCryptographyProperties.

    How can I configure this property?

  • cas.authn.mfa.trusted.crypto.encryption.key-size=512
  • The encryption key size.

    org.apereo.cas.configuration.model.core.util.EncryptionJwtCryptoProperties.

    How can I configure this property?

  • cas.authn.mfa.trusted.crypto.signing.key-size=512
  • The signing key size.

    org.apereo.cas.configuration.model.core.util.SigningJwtCryptoProperties.

    How can I configure this property?

  • cas.authn.mfa.trusted.crypto.strategy-type=ENCRYPT_AND_SIGN
  • Control the cipher sequence of operations. The accepted values are:

    • ENCRYPT_AND_SIGN: Encrypt the value first, and then sign.
    • SIGN_AND_ENCRYPT: Sign the value first, and then encrypt.

    org.apereo.cas.configuration.model.core.util.EncryptionJwtSigningJwtCryptographyProperties.

    How can I configure this property?

  • cas.authn.mfa.trusted.device-fingerprint.cookie.crypto.alg=
  • The signing/encryption algorithm to use.

    org.apereo.cas.configuration.model.core.util.EncryptionJwtSigningJwtCryptographyProperties.

    How can I configure this property?

  • cas.authn.mfa.trusted.device-fingerprint.cookie.crypto.enabled=true
  • Whether crypto operations are enabled.

    org.apereo.cas.configuration.model.core.util.EncryptionJwtSigningJwtCryptographyProperties.

    How can I configure this property?

  • cas.authn.mfa.trusted.device-fingerprint.cookie.crypto.encryption.key-size=512
  • The encryption key size.

    org.apereo.cas.configuration.model.core.util.EncryptionJwtCryptoProperties.

    How can I configure this property?

  • cas.authn.mfa.trusted.device-fingerprint.cookie.crypto.signing.key-size=512
  • The signing key size.

    org.apereo.cas.configuration.model.core.util.SigningJwtCryptoProperties.

    How can I configure this property?

  • cas.authn.mfa.trusted.device-fingerprint.cookie.crypto.strategy-type=ENCRYPT_AND_SIGN
  • Control the cipher sequence of operations. The accepted values are:

    • ENCRYPT_AND_SIGN: Encrypt the value first, and then sign.
    • SIGN_AND_ENCRYPT: Sign the value first, and then encrypt.

    org.apereo.cas.configuration.model.core.util.EncryptionJwtSigningJwtCryptographyProperties.

    How can I configure this property?

    This CAS feature is able to accept signing and encryption crypto keys. In most scenarios if keys are not provided, CAS will auto-generate them. The following instructions apply if you wish to manually and beforehand create the signing and encryption keys.

    Note that if you are asked to create a JWK of a certain size for the key, you are to use the following set of commands to generate the token:

    1
    2
    
    wget https://raw.githubusercontent.com/apereo/cas/master/etc/jwk-gen.jar
    java -jar jwk-gen.jar -t oct -s [size]
    

    The outcome would be similar to:

    1
    2
    3
    4
    5
    
    {
      "kty": "oct",
      "kid": "...",
      "k": "..."
    }
    

    The generated value for k needs to be assigned to the relevant CAS settings. Note that keys generated via the above algorithm are processed by CAS using the Advanced Encryption Standard (AES) algorithm which is a specification for the encryption of electronic data established by the U.S. National Institute of Standards and Technology.


    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.

    Authentication Context

    If an MFA request is bypassed due to a trusted authentication decision, applications will receive a special attribute as part of the validation payload that indicates this behavior. Applications must further account for the scenario where they ask for an MFA mode and yet don’t receive confirmation of it in the response given the authentication session was trusted and MFA bypassed.

    Device Fingerprint

    Please see this guide.

    Bypass

    Please see this guide.

    Storage

    If you do nothing, by default records are kept inside the runtime memory and cached for a configurable amount of time. This is most useful if you have a very small deployment with a small user base or if you wish to demo the functionality. A background cleaner process is also automatically scheduled to clean up expired records.

    Device registrations can also be managed using any one of the following strategies.

    Storage Description
    JSON See this guide.
    JDBC See this guide.
    MongoDb See this guide.
    DynamoDb See this guide.
    Redis See this guide.
    REST See this guide.