REST Authentication

:warning: 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 are included automatically and are listed 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:

cas.authn.rest[0].password-encoder.encoding-algorithmThe encoding algorithm to use such as MD5 .
no default
Required

The encoding algorithm to use such as MD5. Relevant when the type used is DEFAULT or GLIBC_CRYPT. When used with PasswordEncoderTypes#PBKDF2, it should be one of PBKDF2WithHmacSHA1, PBKDF2WithHmacSHA256 or PBKDF2WithHmacSHA512.

Type
String
Default
none
Defined by
PasswordEncoderProperties
cas.authn.rest[0].password-encoder.typeDefine the password encoder type to use.
NONE
Required

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.
Type
String
Default
NONE
Defined by
PasswordEncoderProperties
cas.authn.rest[0].uriEndpoint URI to use for verification of credentials.
no default
RequiredSpEL

Endpoint URI to use for verification of credentials.

Type
String
Default
none
Defined by
RestAuthenticationProperties
Supports
Spring Expression Language
cas.authn.rest[0].methodHTTP method to use when contacting the REST API for authentication.
POST

HTTP method to use when contacting the REST API for authentication.

Type
String
Default
POST
Defined by
RestAuthenticationProperties
cas.authn.rest[0].nameName of the authentication handler.
no default

Name of the authentication handler.

Type
String
Default
none
Defined by
RestAuthenticationProperties
cas.authn.rest[0].orderOrder of the authentication handler in the chain.
no default

Order of the authentication handler in the chain.

Type
Integer
Default
none
Defined by
RestAuthenticationProperties
cas.authn.rest[0].password-encoder.character-encodingThe encoding algorithm to use such as 'UTF-8'.
UTF-8

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

Type
String
Default
UTF-8
Defined by
PasswordEncoderProperties
cas.authn.rest[0].password-encoder.hash-lengthWhen used by PasswordEncoderTypes#ARGON2 , it indicates the hash strength/length.
16

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

Type
int
Default
16
Defined by
PasswordEncoderProperties
cas.authn.rest[0].password-encoder.iterationsWhen used by PasswordEncoderTypes#PBKDF2 , it indicates the required number of iterations.
310000

When used by PasswordEncoderTypes#PBKDF2, it indicates the required number of iterations.

Type
int
Default
310000
Defined by
PasswordEncoderProperties
cas.authn.rest[0].password-encoder.secretSecret to use with PasswordEncoderTypes#STANDARD , PasswordEncoderTypes#PBKDF2 , PasswordEncoderTypes#BCRYPT , PasswordEncoderTypes#GLIBC_CRYPT password encoders.
no default

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

Type
String
Default
none
Defined by
PasswordEncoderProperties
cas.authn.rest[0].password-encoder.strengthStrength or number of iterations to use for password hashing.
16

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

Type
int
Default
16
Defined by
PasswordEncoderProperties
cas.authn.rest[0].stateDefine the scope and state of this authentication handler and the lifecycle in which it can be invoked or activated.
ACTIVE
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.
Type
AuthenticationHandlerStates
Default
ACTIVE
Defined by
RestAuthenticationProperties

Required settings may be needed to activate or affect the feature; review them even when they have a default. Optional settings only need to be set to change a default or to turn on the behavior they control. Third party settings belong to libraries such as Spring Boot that CAS builds on; their own documentation may have more detail.

Password encoding

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,generatedSalt,logger,applicationContext) = args
    logger.debug("Encoding password...")
    return ...
}

Boolean matches(final Object... args) {
    def (rawPassword,encodedPassword,logger,applicationContext) = args
    logger.debug("Does match or not ?");
    return ...

To prepare CAS to support and integrate with Apache Groovy, please review this guide.

Notes on configuration

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, especially 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.

Multitenancy

Configuration settings for database authentication can be specified in a multitenant environment. Please review this guide for more information.