Ticket-Granting Ticket REST Protocol

Ticket-granting tickets can be issued by the REST protocol:

POST /cas/v1/tickets HTTP/1.0
'Content-type': 'Application/x-www-form-urlencoded'
username=battags&password=password&additionalParam1=paramvalue

You may also specify a service parameter to verify whether the authenticated user may be allowed to access the given service.

Successful Response

201 Created
Location: http://www.whatever.com/cas/v1/tickets/{TGT id}

Remember that REST is stateless. Since the caller is the recipient of the ticket-granting ticket that represents a single sign-on session, that means the caller is also responsible for managing and creating single sign-on sessions, removing that responsibility from CAS. In other words, the REST protocol allows one to use CAS as an authentication engine, and not a single sign-on provider. There have been many workarounds, modifications and hacks over the years to bypass this barrier and have REST calls to also, somehow, create the necessary cookies, flows and interactions and whatever else necessary to allow applications to leverage a single sign-on session established via REST. Needless to say, all such endeavors over time have resulted in maintenance headaches, premature aging and loss of DNA.

Unsuccessful Response

If incorrect credentials are sent, CAS will respond with a 401 Unauthorized. A 400 Bad Request error will be sent for missing parameters, etc. If you send a media type it does not understand, it will send the 415 Unsupported Media Type.

JWT Ticket Granting Tickets

Ticket-granting tickets created by the REST protocol may be issued as JWTs instead. Support is enabled by including the following in your overlay:

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

implementation "org.apereo.cas:cas-server-support-rest-tokens:${project.'cas.version'}"

dependencyManagement {
  imports {
    mavenBom "org.apereo.cas:cas-server-support-bom:${project.'cas.version'}"
  }
}

dependencies {  
  implementation "org.apereo.cas:cas-server-support-rest-tokens"
}

To request a ticket-granting ticket as JWT next, ensure the POST request matches the following:

POST /cas/v1/tickets HTTP/1.0

username=battags&password=password&token=true&additionalParam1=paramvalue

The token parameter may either be passed as a request parameter or a request header. The body of the response will include the ticket-granting ticket as a JWT. Note that JWTs created are typically signed and encrypted by default with pre-generated keys.

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.}

_{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. You should only include this field in your
configuration if you need to modify the default value.}

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.

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. The validation process is on by default and can be skipped on startup using a special system property SKIP_CONFIG_VALIDATION that should be set to true. 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.

X509 Authentication

The feature extends the CAS REST API communication model to non-interactive X.509 authentication where REST credentials may be retrieved from a certificate embedded in the request rather than the usual and default username/password.

This pattern may be of interest in cases where the internal network architecture hides the CAS server from external users behind firewall, reverse proxy, or a messaging bus and allows only trusted applications to connect directly to the CAS server.

Usage Warning!

The X.509 feature over REST using a body parameter or a http header provides a tremendously convenient target for claiming user identities or obtaining TGTs without proof of private key ownership. To securely use this feature, network configuration MUST allow connections to the CAS server only from trusted hosts which in turn have strict security limitations and logging. It is also recommended to make sure that the body parameter or the http header can only come from trusted hosts and not from the original authenticating client.

It is also possible to let the servlet container validate the TLS client key / X.509 certificate during TLS handshake, and have CAS server retrieve the certificate from the container.

Support is enabled by including the following in your overlay:

<dependency>
  <groupId>org.apereo.cas</groupId>
  <artifactId>cas-server-support-rest-x509</artifactId>
  <version>${cas.version}</version>
</dependency>

implementation "org.apereo.cas:cas-server-support-rest-x509:${project.'cas.version'}"

dependencyManagement {
  imports {
    mavenBom "org.apereo.cas:cas-server-support-bom:${project.'cas.version'}"
  }
}

dependencies {  
  implementation "org.apereo.cas:cas-server-support-rest-x509"
}