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.

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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final String signingSecret = RandomUtils.randomAlphanumeric(256);
final String encryptionSecret = RandomUtils.randomAlphanumeric(48);

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

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

final CommonProfile profile = new CommonProfile();
profile.setId("casuser");
final String 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:

implementation "org.apereo.cas:cas-server-support-token-webflow:${project.'cas.version'}"
<dependency>
  <groupId>org.apereo.cas</groupId>
  <artifactId>cas-server-support-token-webflow</artifactId>
  <version>${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-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 is not strictly necessary in the end-user CAS configuration, because a default value may be assigned or the feature in question may not be immediately intended for use. You may want to own the setting and update it assigned value, assuming the intended feature controlled by the setting is utilized.

  • cas.authn.token.principal-transformation.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.

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

  • cas.authn.token.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.

  • cas.authn.token.webflow.order=0
  • The order in which the webflow is configured.

  • cas.authn.token.name=
  • Name of the authentication handler.

  • cas.authn.token.principal-transformation.blocking-pattern=
  • A regular expression that will be used against the username to match for blocking/forbidden values. If a match is found, an exception will be thrown and principal transformation will fail.

  • cas.authn.token.principal-transformation.case-conversion=
  • Indicate whether the principal identifier should be transformed into upper-case, lower-case, etc.NONE:No conversion..LOWERCASE:Lowercase conversion..UPPERCASE:Uppercase conversion..

  • cas.authn.token.principal-transformation.pattern=
  • A regular expression that will be used against the provided username for username extractions. On a successful match, the first matched group in the pattern will be used as the extracted username.

  • cas.authn.token.principal-transformation.prefix=
  • Prefix to add to the principal id prior to authentication.

  • cas.authn.token.principal-transformation.suffix=
  • Suffix to add to the principal id prior to authentication.

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

  • cas.authn.token.crypto.enabled=true
  • Whether crypto operations are enabled.

  • cas.authn.token.crypto.encryption-enabled=true
  • Whether crypto encryption operations are enabled.

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

  • cas.authn.token.crypto.signing-enabled=true
  • Whether crypto signing operations are enabled.

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

  • 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.