Duo Security User Registration

If users are unregistered with Duo Security or allowed through via a direct bypass, CAS will query Duo Security for the user account apriori to learn whether user is registered or configured for direct bypass. If the account is configured for direct bypass or the user account is not registered yet the new-user enrollment policy allows the user to skip registration, CAS will bypass Duo Security altogether and shall not challenge the user and will also NOT report back a multifactor-enabled authentication context back to the application.

:warning: YMMV

In recent conversations with Duo Security, it turns out that the API behavior has changed (for security reasons) where it may no longer accurately report back account status. This means even if the above conditions hold true, CAS may continue to route the user to Duo Security having received an eligibility status from the API. Duo Security is reportedly working on a fix to restore the API behavior in a more secure way. In the meanwhile, YMMV.

If you would rather not rely on Duo Security’s built-in registration flow and have your own registration application that allows users to onboard and enroll with Duo Security, you can instruct CAS to redirect to your enrollment application, if the user’s account status is determined to require enrollment. This typically means that you must turn on user-account-status checking in CAS so that it can verify the user’s account status directly with Duo Security. You must also make sure your integration type, as selected in Duo Security’s admin dashboard, is chosen to be the correct type that would allow CAS to execute such requests and of course, the user in question must not have been onboard, enrolled or created previously anywhere in Duo Security.

The redirect URL to your enrollment application may include a special principal parameter that contains the user’s identity as JWT. Cipher operations and settings must be enabled in CAS settings for Duo Security’s registration before this parameter can be built and added to the final URL.

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

cas.authn.mfa.duo[0].registration.crypto.encryption.keyThe encryption key is a string whose length is defined by the encryption key size setting.
no default
RequiredSpEL

The encryption key is a string whose length is defined by the encryption key size setting.

Type
String
Default
none
Defined by
EncryptionJwtCryptoProperties
Supports
Spring Expression Language
cas.authn.mfa.duo[0].registration.crypto.signing.keyThe signing key is a string whose length is defined by the signing key size setting.
no default
RequiredSpEL

The signing key is a string whose length is defined by the signing key size setting.

Type
String
Default
none
Defined by
SigningJwtCryptoProperties
Supports
Spring Expression Language
cas.authn.mfa.duo[0].registration.crypto.algThe signing/encryption algorithm to use.
A256CBC-HS512

The signing/encryption algorithm to use.

Type
String
Default
A256CBC-HS512
Defined by
EncryptionOptionalSigningOptionalJwtCryptographyProperties
cas.authn.mfa.duo[0].registration.crypto.enabledWhether crypto operations are enabled.
true

Whether crypto operations are enabled.

Type
boolean
Default
true
Defined by
EncryptionOptionalSigningOptionalJwtCryptographyProperties
cas.authn.mfa.duo[0].registration.crypto.encryption-enabledWhether crypto encryption operations are enabled.
true

Whether crypto encryption operations are enabled.

Type
boolean
Default
true
Defined by
EncryptionOptionalSigningOptionalJwtCryptographyProperties
cas.authn.mfa.duo[0].registration.crypto.encryption.key-sizeThe encryption key size.
512

The encryption key size.

Type
int
Default
512
Defined by
EncryptionJwtCryptoProperties
cas.authn.mfa.duo[0].registration.crypto.signing-enabledWhether crypto signing operations are enabled.
true

Whether crypto signing operations are enabled.

Type
boolean
Default
true
Defined by
EncryptionOptionalSigningOptionalJwtCryptographyProperties
cas.authn.mfa.duo[0].registration.crypto.signing.key-sizeThe signing key size.
512

The signing key size.

Type
int
Default
512
Defined by
SigningJwtCryptoProperties
cas.authn.mfa.duo[0].registration.crypto.strategy-typeControl the cipher sequence of operations.
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.
Type
String
Default
ENCRYPT_AND_SIGN
Defined by
EncryptionOptionalSigningOptionalJwtCryptographyProperties
cas.authn.mfa.duo[0].registration.registration-urlLink to a registration app, typically developed in-house in order to allow new users to sign-up for duo functionality.
no default

Link to a registration app, typically developed in-house in order to allow new users to sign-up for duo functionality. If the user account status requires enrollment and this link is specified, CAS will redirect the authentication flow to this registration app. Otherwise, the default duo mechanism for new-user registrations shall take over. Upon redirecting to the registration app, CAS would also build a principal parameter into the registration URL, typically in form of a JSON web token that conveys the user's identity. This JWT can be signed and/or encrypted using settings defined via the #getCrypto() configuration block here.

Type
String
Default
none
Defined by
DuoSecurityMultifactorAuthenticationRegistrationProperties

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.

Signing & encryption

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:

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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:

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{
  "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.


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.