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REST Protocol

The REST protocol allows one to model applications as users, programmatically acquiring service tickets to authenticate to other applications. This means that other applications would be able to use a CAS client to accept Service Tickets rather than to rely upon another technology such as client SSL certificates for application-to-application authentication of requests. This is achieved by exposing a way to RESTfully obtain a Ticket Granting Ticket and then use that to obtain a Service Ticket.

Usage Warning!

The REST endpoint may become a tremendously convenient target for brute force dictionary attacks on CAS server. Consider enabling throttling support to ensure brute force attacks are prevented upon authentication failures.

Configuration

Support is enabled by including the following to the overlay:

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

Request a Ticket Granting Ticket

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POST /cas/v1/tickets HTTP/1.0

username=battags&password=password&additionalParam1=paramvalue

Successful Response

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

Unsuccessful Response

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

Request a Service Ticket

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POST /cas/v1/tickets/{TGT id} HTTP/1.0

service={form encoded parameter for the service url}

Successful Response

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200 OK
ST-1-FFDFHDSJKHSDFJKSDHFJKRUEYREWUIFSD2132

Validate Service Ticket

Service ticket validation is handled through the CAS Protocol via any of the validation endpoints such as /p3/serviceValidate.

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GET /cas/p3/serviceValidate?service={service url}&ticket={service ticket}

Unsuccessful Response

CAS will send a 400 Bad Request. If an incorrect media type is sent, it will send the 415 Unsupported Media Type.

Logout

Destroy the SSO session by removing the issued ticket:

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DELETE /cas/v1/tickets/TGT-fdsjfsdfjkalfewrihfdhfaie HTTP/1.0

Ticket Status

Verify the status of an obtained ticket to make sure it still is valid and has not yet expired.

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GET /cas/v1/tickets/TGT-fdsjfsdfjkalfewrihfdhfaie HTTP/1.0

Successful Response

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200 OK

Unsuccessful Response

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404 NOT FOUND

Add Service

Support is enabled by including the following in your maven overlay:

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

Invoke CAS to register applications into its own service registry. The REST call must be authenticated as it requires a TGT from the CAS server, and furthermore, the authenticated principal that submits the request must be authorized with a pre-configured role name and value that is designated in the CAS configuration via the CAS properties.

To see the relevant list of CAS properties, please review this guide.

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POST /cas/v1/services/add/{TGT id} HTTP/1.0
serviceId=svcid&name=svcname&description=svcdesc&evaluationOrder=1234&enabled=true&ssoEnabled=true

Successful Response

If the request is successful, the returned value in the response would be the generated identifier of the new service.

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200 OK
5463544213

X.509 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 or a messaging bus and allows only trusted applications to connect to the CAS server.

Usage Warning!

The X.509 feature over REST provides a tremendously convenient target for claiming user identities. 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.

Support is enabled by including the following in your maven overlay:

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

Request a Ticket Granting Ticket

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POST /cas/v1/tickets HTTP/1.0
cert=<ascii certificate>

Successful Response

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

CAS REST Clients

In order to interact with the CAS REST API, a REST client must be used to submit credentials, receive tickets and validate them. The following Java REST client is available by pac4j:

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String casUrlPrefix = "http://localhost:8080/cas";
CasRestAuthenticator authenticator = new CasRestAuthenticator(casUrlPrefix);
CasRestFormClient client = new CasRestFormClient(authenticator);

// The request object must contain the CAS credentials
final WebContext webContext = new J2EContext(request, response);
final HttpTGTProfile profile = client.requestTicketGrantingTicket(context);
final CasCredentials casCreds = client.requestServiceTicket("<SERVICE_URL>", profile);
final CasProfile casProfile = client.validateServiceTicket("<SERVICE_URL>", casCreds);
client.destroyTicketGrantingTicket(context, profile);

Throttling

To understand how to throttling works in CAS, please review the available options.

By default, throttling REST requests is turned off.