JWT Authentication

JSON Web Tokens are an open, industry standard RFC 7519 method for representing claims securely between two parties. CAS provides support for token-based authentication on top of JWT, where an authentication request can be granted an SSO session based on a form of credentials that are JWTs.

JWT Service Tickets

CAS may also be allowed to fully create signed/encrypted JWTs and pass them back to the application in form of service tickets. In this case, JWTs are entirely self-contained and contain the authenticated principal as well as all authorized attributes in form of JWT claims. To learn more about this functionality, please review this guide.

Overview

CAS expects a token parameter (or request header) to be passed along to the /login endpoint. The parameter value must be a JWT.

:information_source: JCE Requirement

It's safe to make sure you have the proper JCE bundle installed in your Java environment that is used by CAS, specially if you need to use specific signing/encryption algorithms and methods. Be sure to pick the right version of the JCE for your Java version. Java versions can be detected via the java -version command.

Here is an example of how to generate a JWT via Pac4j:



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var signingSecret = RandomUtils.randomAlphanumeric(256);
var encryptionSecret = RandomUtils.randomAlphanumeric(48);

System.out.println("signingSecret " + signingSecret);
System.out.println("encryptionSecret " + encryptionSecret);

var g = new JwtGenerator<>();
g.setSignatureConfiguration(new SecretSignatureConfiguration(signingSecret, JWSAlgorithm.HS256));
g.setEncryptionConfiguration(new SecretEncryptionConfiguration(encryptionSecret,
        JWEAlgorithm.DIR, EncryptionMethod.A192CBC_HS384));

var profile = new CommonProfile();
profile.setId("casuser");
var token = g.generate(profile);
System.out.println("token: " + token);

Once the token is generated, you may pass it to the /login endpoint of CAS as such:



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/cas/login?service=https://...&token=<TOKEN_VALUE>

The token parameter may also be passed as a request header.

Configuration

JWT authentication support is enabled by including the following dependency in the WAR overlay:



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





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implementation "org.apereo.cas:cas-server-support-token-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-token-webflow"
}





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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-token-webflow"
}

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.token.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.token.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.token.crypto.alg=

    • The signing/encryption algorithm to use.

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

    How can I configure this property?

  • cas.authn.token.crypto.enabled=true

    • Whether crypto operations are enabled.

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

    How can I configure this property?

  • cas.authn.token.crypto.encryption-enabled=true

    • Whether crypto encryption operations are enabled.

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

    How can I configure this property?

  • cas.authn.token.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.token.crypto.signing-enabled=true

    • Whether crypto signing operations are enabled.

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

    How can I configure this property?

  • cas.authn.token.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.token.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.EncryptionOptionalSigningOptionalJwtCryptographyProperties.

    How can I configure this property?

  • cas.authn.token.webflow.enabled=true

    • Whether webflow auto-configuration should be enabled.

    org.apereo.cas.configuration.model.core.web.flow.WebflowAutoConfigurationProperties.

    How can I configure this property?

  • cas.authn.token.webflow.order=0

    • The order in which the webflow is configured.

    org.apereo.cas.configuration.model.core.web.flow.WebflowAutoConfigurationProperties.

    How can I configure this property?

  • cas.authn.token.credential-criteria=

    • A number of authentication handlers are allowed to determine whether they can operate on the provided credential and as such lend themselves to be tried and tested during the authentication handler selection phase. The credential criteria may be one of the following options:

    • 1) A regular expression pattern that is tested against the credential identifier.
    • 2) A fully qualified class name of your own design that implements Predicate.
    • 3) Path to an external Groovy script that implements the same interface.

    This settings supports regular expression patterns. [?].

    org.apereo.cas.configuration.model.support.token.TokenAuthenticationProperties.

    How can I configure this property?

  • cas.authn.token.name=

    • Name of the authentication handler.

    org.apereo.cas.configuration.model.support.token.TokenAuthenticationProperties.

    How can I configure this property?

  • cas.authn.token.order=

    • Order of the authentication handler in the chain.

    org.apereo.cas.configuration.model.support.token.TokenAuthenticationProperties.

    How can I configure this property?

  • cas.authn.token.sso-token-enabled=false

    • When set to true, will generate a token and store it as an authentication attribute into the single sign-on session. This token can be used later on for token-based authentication attempts, and should allow SSO access to the server.

    org.apereo.cas.configuration.model.support.token.TokenAuthenticationProperties.

    How can I configure this property?

  • cas.authn.token.state=

    • Define the scope and state of this authentication handler and the lifecycle in which it can be invoked or activated. Available values are as follows:

    • ACTIVE: Active authentication handler, and is invoked by default automatically to verify credentials globally.
    • STANDBY: Authentication handler is in a semi-enabled state, waiting to be called only on-demand when explicitly asked for.

    org.apereo.cas.configuration.model.support.token.TokenAuthenticationProperties.

    How can I configure this property?

  • cas.authn.token.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.token.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.token.crypto.alg=

    • The signing/encryption algorithm to use.

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

    How can I configure this property?

  • cas.authn.token.crypto.enabled=true

    • Whether crypto operations are enabled.

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

    How can I configure this property?

  • cas.authn.token.crypto.encryption-enabled=true

    • Whether crypto encryption operations are enabled.

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

    How can I configure this property?

  • cas.authn.token.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.token.crypto.signing-enabled=true

    • Whether crypto signing operations are enabled.

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

    How can I configure this property?

  • cas.authn.token.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.token.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.EncryptionOptionalSigningOptionalJwtCryptographyProperties.

    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:

    

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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.

    Certain authentication handlers are allowed to determine whether they can operate on the provided credential and as such lend themselves to be tried and tested during the authentication handler selection phase. The credential criteria may be one of the following options:

    • A regular expression pattern that is tested against the credential identifier.
    • A fully qualified class name of your own design that looks similar to the below example:
    

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    import java.util.function.Predicate;
import org.apereo.cas.authentication.Credential;

public class PredicateExample implements Predicate<Credential> {
    @Override
    public boolean test(final Credential credential) {
        // Examine the credential and return true/false
    }
}
    • Path to an external Groovy script that looks similar to the below example:
    

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    import org.apereo.cas.authentication.Credential
import java.util.function.Predicate

class PredicateExample implements Predicate<Credential> {
    @Override
    boolean test(final Credential credential) {
        // test and return result
    }
}

    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.

    Configure the appropriate service in your service registry to hold the secrets:

    

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    {
  "@class" : "org.apereo.cas.services.CasRegisteredService",
  "serviceId" : "https://.+",
  "name" : "testId",
  "id" : 1,
  "properties" : {
    "@class" : "java.util.HashMap",
    "jwtSigningSecret" : {
      "@class" : "org.apereo.cas.services.DefaultRegisteredServiceProperty",
      "values" : [ "java.util.HashSet", [ "<SECRET>" ] ]
    },
    "jwtEncryptionSecret" : {
      "@class" : "org.apereo.cas.services.DefaultRegisteredServiceProperty",
      "values" : [ "java.util.HashSet", [ "<SECRET>" ] ]
    },
    "jwtSigningSecretAlg" : {
      "@class" : "org.apereo.cas.services.DefaultRegisteredServiceProperty",
      "values" : [ "java.util.HashSet", [ "HS256" ] ]
    },
    "jwtEncryptionSecretAlg" : {
      "@class" : "org.apereo.cas.services.DefaultRegisteredServiceProperty",
      "values" : [ "java.util.HashSet", [ "dir" ] ]
    },
    "jwtEncryptionSecretMethod" : {
      "@class" : "org.apereo.cas.services.DefaultRegisteredServiceProperty",
      "values" : [ "java.util.HashSet", [ "A192CBC-HS384" ] ]
    },
    "jwtSecretsAreBase64Encoded" : {
       "@class" : "org.apereo.cas.services.DefaultRegisteredServiceProperty",
       "values" : [ "java.util.HashSet", [ "false" ] ]
    }
  }
}

    Note that the only required property is jwtSigningSecret.

    Signing and encryption keys may also be defined on a per-service basis, or globally via CAS settings.

    The following properties are available and recognized by CAS for various modules and features:

    Name Default Value Type Group
    jwtSigningSecret STRING JWT_AUTHENTICATION
    jwtSigningSecretAlg HS256 STRING JWT_AUTHENTICATION
    jwtEncryptionSecret STRING JWT_AUTHENTICATION
    jwtEncryptionSecretAlg STRING JWT_AUTHENTICATION
    jwtEncryptionSecretMethod A192CBC-HS384 STRING JWT_AUTHENTICATION
    jwtSecretsAreBase64Encoded false BOOLEAN JWT_AUTHENTICATION

    Actuator Endpoints

    The following endpoints are provided by CAS:

     Validate an authentication token for the user and the intended application.

     Produce an authentication token for the user and the intended application.