Client Registration - OAuth Authentication

Every OAuth relying party must be defined as a CAS service:



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{
  "@class" : "org.apereo.cas.support.oauth.services.OAuthRegisteredService",
  "clientId": "clientid",
  "clientSecret": "clientSecret",
  "serviceId" : "^(https|imaps)://<redirect-uri>.*",
  "name" : "OAuthService",
  "id" : 100,
  "supportedGrantTypes": [ "java.util.HashSet", [ "...", "..." ] ],
  "supportedResponseTypes": [ "java.util.HashSet", [ "...", "..." ] ],
  "scopes": [ "java.util.HashSet", [ "MyCustomScope" ] ],
  "audience": [ "java.util.HashSet", [ "MyAudience" ] ],
}

The following fields are supported:

Field Description
serviceId The pattern that authorizes the redirect URI(s), or same as clientId in case redirect_uri is not required by the grant type (i.e client_credentials, etc). Note that the redirect_uri parameter that is ultimately matched against pattern must not have URL fragments, invalid schemes such as javascript or data or suspicious parameters such as code, state, etc.
clientId The client identifier for the application/service.
clientSecret The client secret for the application/service. The client secret received from the service will be URL decoded before being compared to the secret in the CAS service definition.
userProfileViewType Formatting options for the user profiles; Default is undefined. Options are NESTED, FLAT.
scopes Collection of authorized scopes for this service that act as a filter for the requested scopes in the authorization request.
supportedGrantTypes Collection of supported grant types for this service.
supportedResponseTypes Collection of supported response types for this service.
bypassApprovalPrompt Whether approval prompt/consent screen should be bypassed. Default is false.
generateRefreshToken Whether a refresh token should be generated along with the access token. Default is false.
renewRefreshToken Whether the existing refresh token should be expired and a new one generated (and sent along) whenever a new access token is requested (with grant_type = refresh_token). Only possible if generateRefreshToken is set to true. Default is false.
jwtAccessToken Whether access tokens should be created as JWTs. Default is false.
jwtRefreshToken Whether refresh tokens should be created as JWTs. Default is false.
jwtAccessTokenSigningAlg The JWT signing algorithm to use for JWT access tokens. Defaults to the signing key’s algorithm.
introspectionSignedResponseAlg Optional. The algorithm header value used to sign the JWT introspection response. Default is RS512.
introspectionEncryptedResponseAlg Optional. The algorithm header value used for content key encryption relevant for introspection JWT responses.
introspectionEncryptedResponseEncoding Optional. The algorithm method header value used to content encryption relevant for introspection JWT responses.
responseMode Allow CAS to alter the mechanism used for returning responses back to the client. See this.
audience Optional. Set of values that can control the aud field in JWT access tokens or ID tokens. If left undefined, the client ID will typically be used instead.
:information_source: Keep What You Need!

You are encouraged to only keep and maintain properties and settings needed for a particular integration. It is UNNECESSARY to grab a copy of all service fields and try to configure them yet again based on their default. While you may wish to keep a copy as a reference, this strategy would ultimately lead to poor upgrades increasing chances of breaking changes and a messy deployment at that.

Service definitions are typically managed by the service management facility.

Encryptable Client Secrets

Client secrets for OAuth relying parties may be defined as encrypted values prefixed with {cas-cipher}:



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{
  "@class": "org.apereo.cas.support.oauth.services.OAuthRegisteredService",
  "clientId": "clientid",
  "clientSecret": "{cas-cipher}eyJhbGciOiJIUzUxMiIs...",
  "serviceId" : "^(https|imaps)://<redirect-uri>.*",
  "name": "Sample",
  "id": 100
}

Client secrets may be encrypted using CAS-provided cipher operations either manually or via the CAS Command-line shell.

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. In other words, you should only include this field in your configuration if you need to modify the default value or if you need to turn on the feature controlled by the setting.

This CAS feature is able to accept signing and encryption crypto keys. In most scenarios if keys are not provided, CAS will auto-generate them. The following instructions apply if you wish to manually and beforehand create the signing and encryption keys.

Note that if you are asked to create a JWK of a certain size for the key, you are to use the following set of commands to generate the token:



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wget https://raw.githubusercontent.com/apereo/cas/master/etc/jwk-gen.jar
java -jar jwk-gen.jar -t oct -s [size]

The outcome would be similar to:



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{
  "kty": "oct",
  "kid": "...",
  "k": "..."
}

The generated value for k needs to be assigned to the relevant CAS settings. Note that keys generated via the above algorithm are processed by CAS using the Advanced Encryption Standard (AES) algorithm which is a specification for the encryption of electronic data established by the U.S. National Institute of Standards and Technology.

Control global properties that are relevant to Hibernate, when CAS attempts to employ and utilize database resources, connections and queries.

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, specially 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.

Attribute Release

Attribute/claim filtering and release policies are defined per OAuth service. See this guide for more info.