REST Authentication

Be Careful

This documentation describes how to delegate and submit authentication requests to a remote REST endpoint. It has nothing to do with the native CAS REST API, whose configuration and caveats are documented here.

REST authentication is enabled by including the following dependencies in the WAR overlay:

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

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implementation "org.apereo.cas:cas-server-support-rest-authentication:${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-rest-authentication"
}

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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-rest-authentication"
}

This allows the CAS server to reach to a remote REST endpoint via a POST for verification of credentials. Credentials are passed via an Authorization header whose value is Basic XYZ where XYZ is a Base64 encoded version of the credentials.

The response that is returned must be accompanied by a 200 status code where the body should contain id and attributes fields, the latter being optional, which represent the authenticated principal for CAS:

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{
  "@class": "org.apereo.cas.authentication.principal.SimplePrincipal",
  "id": "casuser",
  "attributes": {
    "@class": "java.util.LinkedHashMap",
    "names": [
      "java.util.List", ["cas", "user"]
    ]
  }
}

Expected responses from the REST endpoint are mapped to CAS as such:

Code Result
200 Successful authentication.
403 Produces a AccountDisabledException
404 Produces a AccountNotFoundException
423 Produces a AccountLockedException
412 Produces a AccountExpiredException
428 Produces a AccountPasswordMustChangeException
Other Produces a FailedLoginException

Authentication Warnings

The remote REST endpoint can send warnings back to the CAS server using custom headers. If the authentication is successful, these warnings will be shown to the user directly after the login.

Header Description
X-CAS-Warning For each X-CAS-Warning header present in the response, a corresponding message will be shown to the user. The header value can either be the key for a localized message or the message itself.
X-CAS-PasswordExpirationDat If this header is present in the response and contains a RFC1123 date a special message will be shown to warn the user about the expiring password. If a password management provider is configured, the user will be able to directly change the password.

Configuration

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.rest.password-encoder.encoding-algorithm=

    • The encoding algorithm to use such as MD5. Relevant when the type used is DEFAULT or GLIBC_CRYPT.

    org.apereo.cas.configuration.model.core.authentication.PasswordEncoderProperties.

    How can I configure this property?

  • cas.authn.rest.password-encoder.type=NONE

    • Define the password encoder type to use. Type may be specified as blank or NONE to disable password encoding. It may also refer to a fully-qualified class name that implements the Spring Security's PasswordEncoder interface if you wish you define your own encoder.

    The following types may be used:

    • NONE: No password encoding (i.e. plain-text) takes place.
    • DEFAULT: Use the DefaultPasswordEncoder of CAS. For message-digest algorithms via character-encoding and encoding-algorithm.
    • BCRYPT: Use the BCryptPasswordEncoder based on the strength provided and an optional secret.
    • SCRYPT: Use the SCryptPasswordEncoder.
    • PBKDF2: Use the Pbkdf2PasswordEncoder based on the strength provided and an optional secret.
    • STANDARD: Use the StandardPasswordEncoder based on the secret provided.
    • SSHA: Use the LdapShaPasswordEncoder supports Ldap SHA and SSHA (salted-SHA). The values are base-64 encoded and have the label {SHA} or {SSHA} prepended to the encoded hash.
    • GLIBC_CRYPT: Use the GlibcCryptPasswordEncoder based on the encoding-algorithm, strength provided and an optional secret.
    • org.example.MyEncoder: An implementation of PasswordEncoder of your own choosing.
    • file:///path/to/script.groovy: Path to a Groovy script charged with handling password encoding operations.

    org.apereo.cas.configuration.model.core.authentication.PasswordEncoderProperties.

    How can I configure this property?

  • cas.authn.rest.uri=

    • Endpoint URI to use for verification of credentials.

    org.apereo.cas.configuration.model.support.rest.RestAuthenticationProperties.

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

  • cas.authn.rest.password-encoder.character-encoding=UTF-8

    • The encoding algorithm to use such as 'UTF-8'. Relevant when the type used is DEFAULT.

    org.apereo.cas.configuration.model.core.authentication.PasswordEncoderProperties.

    How can I configure this property?

  • cas.authn.rest.password-encoder.hash-length=16

    • When used by PasswordEncoderTypes#ARGON2, it indicates the hash strength/length.

    org.apereo.cas.configuration.model.core.authentication.PasswordEncoderProperties.

    How can I configure this property?

  • cas.authn.rest.password-encoder.secret=

    • Secret to use with PasswordEncoderTypes#STANDARD, PasswordEncoderTypes#PBKDF2, PasswordEncoderTypes#BCRYPT, PasswordEncoderTypes#GLIBC_CRYPT password encoders. Secret usually is an optional setting.

    org.apereo.cas.configuration.model.core.authentication.PasswordEncoderProperties.

    How can I configure this property?

  • cas.authn.rest.password-encoder.strength=16

    • Strength or number of iterations to use for password hashing. Usually relevant when dealing with PasswordEncoderTypes#PBKDF2, PasswordEncoderTypes#BCRYPT or PasswordEncoderTypes#GLIBC_CRYPT. When used by PasswordEncoderTypes#ARGON2, it indicates the salt strength.

    org.apereo.cas.configuration.model.core.authentication.PasswordEncoderProperties.

    How can I configure this property?

  • cas.authn.rest.charset=US-ASCII

    • Charset to encode the credentials sent to the REST endpoint.

    org.apereo.cas.configuration.model.support.rest.RestAuthenticationProperties.

    How can I configure this property?

  • cas.authn.rest.name=

    • Name of the authentication handler.

    org.apereo.cas.configuration.model.support.rest.RestAuthenticationProperties.

    How can I configure this property?

  • cas.authn.rest.order=

    • Order of the authentication handler in the chain.

    org.apereo.cas.configuration.model.support.rest.RestAuthenticationProperties.

    How can I configure this property?

  • cas.authn.rest.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.rest.RestAuthenticationProperties.

    How can I configure this property?

    If you need to design your own password encoding scheme where the type is specified as a fully qualified Java class name, the structure of the class would be similar to the following:

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    package org.example.cas;

import org.springframework.security.crypto.codec.*;
import org.springframework.security.crypto.password.*;

public class MyEncoder extends AbstractPasswordEncoder {
    @Override
    protected byte[] encode(CharSequence rawPassword, byte[] salt) {
        return ...
    }
}

    If you need to design your own password encoding scheme where the type is specified as a path to a Groovy script, the structure of the script would be similar to the following:

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    import java.util.*

byte[] run(final Object... args) {
    def rawPassword = args[0]
    def generatedSalt = args[1]
    def logger = args[2]
    def casApplicationContext = args[3]

    logger.debug("Encoding password...")
    return ...
}

Boolean matches(final Object... args) {
    def rawPassword = args[0]
    def encodedPassword = args[1]
    def logger = args[2]
    def casApplicationContext = args[3]

   logger.debug("Does match or not ?");
   return ...

    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.