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.
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:
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. 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 ofinotify 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 .
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cas.authn.token.crypto.encryption.key=
The encryption key is a JWT whose length is defined by the encryption key size setting.
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cas.authn.token.crypto.signing.key=
The signing key is a JWT whose length is defined by the signing key size setting.
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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.
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cas.authn.token.principal-transformation.case-conversion=NONE
Indicate whether the principal identifier should be transformed into upper-case, lower-case, etc. Available values are as follows:
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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.
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cas.authn.token.principal-transformation.prefix=
Prefix to add to the principal id prior to authentication.
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cas.authn.token.principal-transformation.suffix=
Suffix to add to the principal id prior to authentication.
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cas.authn.token.crypto.alg=
The signing/encryption algorithm to use.
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cas.authn.token.crypto.enabled=true
Whether crypto operations are enabled.
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cas.authn.token.crypto.encryption-enabled=true
Whether crypto encryption operations are enabled.
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cas.authn.token.crypto.encryption.key-size=512
The encryption key size.
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cas.authn.token.crypto.signing-enabled=true
Whether crypto signing operations are enabled.
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cas.authn.token.crypto.signing.key-size=512
The signing key size.
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cas.authn.token.crypto.strategy-type=ENCRYPT_AND_SIGN
Control the cipher sequence of operations. The accepted values are:
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cas.authn.token.webflow.enabled=true
Whether webflow auto-configuration should be enabled.
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cas.authn.token.webflow.order=0
The order in which the webflow is configured.
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