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CAS-NG A small enhancement to CAS 3 to provide new services.

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Presentation on theme: "CAS-NG A small enhancement to CAS 3 to provide new services."— Presentation transcript:

1 CAS-NG A small enhancement to CAS 3 to provide new services

2 Objectives [of this talk] TrustedOtherCas – single sign-on to more than one instance of the CAS codebase ScriptedValidate – Extend CAS ServiceValidate with Access Control rules written in simple scripting languages CAS Extensibility – How and where these extensions fit into the architecture

3 Enable Additional CAS Function Now Existing Central CAS 3 (or 2) Enhanced CAS 3 Trust Existing Satisfied Services New Services requiring new function Validate

4 Departmental Local Function Existing Central CAS 3 (or 2) Departmental CAS 3 Trust Department Service Validate Departmental CAS 3 Trust Department Service Validate Central Service

5 Simple Peer Federation CAS Service Campus CAS client trust Other Institution

6 cas-server-support-trusted existing CAS 3 optional subproject J2EE Container Web Listener Container Based Authentication S E R V L E T api CAS request.getRemoteUser()

7 trustedOtherCas – a WebFlow bean that generates trusted credentials CAS login WebFlow /cas/login cookie x.509 cert other stuff Form or OtherCAS CAS Filter logic turned into a Web Flow Bean

8 TrustedOtherCas Step by Step Get it in the WAR Get cas-server-support-trusted-otherCAS project, put it in CAS 3 source directory Add name to top level POM module list [so it gets compiled by Maven into a JAR] Add the cas-server-support-trusted and trusted-otherCAS artifact JARs to the webapp project POM dependency list [so JAR gets added to the WAR WEB-INF/lib]

9 TrustedOtherCas Step by Step Spring Configuration Add trusted project beans to the Handler and Resolver bean list [so credentials can be processed] in deployerConfigContext.xml In cas-servlet.xml, configure an instance of the trustedOtherCas bean with the login and validation URL of the other CAS Add OtherCas bean to login-webflow.xml and change flow logic to go to it

10 There can be more than one If you have more than one trustedOtherCas, each can have its own configured bean, but Each needs its own /loginXXX URL and its own WebFlow because the ticket= doesnt tell you which CAS it came from, so you have to know this based on the URL that CAS redirected back to

11 Current CAS doesnt do Access Control Service created by Humanities Professor Bin Laden front end CAS Q: Who is this guy? A: Bin Laden Should I let Bin Laden in? All the institutional data about people is over there somewhere, but ordinary users dont have access to it.

12 Allow access to licensed MP3 files to Music department faculty Music graduate students Undergraduate Music majors Students enrolled in Music 202 Beyond the programming skills of a Music prof

13 Access Control Problems Dont want to give out access to HR, student systems, and other institutional data to everyone who has a Web application Access control is too complicated for non- programmers to get it right XACML is irrational Institutional logic: Just what is a …

14 CASNG makes the decisions Bin Laden Dumb Service CAS Client with script uri CAS /cas/scriptedValidate,ticket=…, service=…,acscript={uri} script data getter HR student system FBI Alumni

15 CAS 3 Web (MVC) View (JSP or Redirect) Controller Validate Login WebFlow Ticket CRUD Business Logic handler resolver Ticket Cache optional store Auth Mgr TrustedOtherCas scripts

16 Background: Spring MVC CAS mod of Spring Servlet HTTP Web.xml servlet URL mappings Bean MVC URL mappings Bean Login Web flow /login /validate Spring SideServlet Side

17 WEB-INF/web.xml URL mapping cas org.jasig.cas.web.init.SafeDispatcherServlet cas /scriptedValidate

18 cas-servlet.xml then maps each URL to a Spring Bean serviceValidateController scriptedValidateController legacyValidateController …

19 Spring MVC request lifecycle Spring Servlet URL to bean map Action Bean Request ModelAndView Properties file JSP (or View Bean) ViewName varnamevalue varnamevalue varnamevalue Model EL

20 Plug it In Spring Servlet URL to bean map Scripted Validate Controller /scriptedValidate ModelAndView Properties file JSP (or View Bean) ViewName varnamevalue varnamevalue varnamevalue Model EL Service Validate Controller

21 CAS Business Logic API Ticket CRUD Business Logic handler resolver Ticket Cache optional store Auth Mgr If this was a real J2EE application, this would be the EJB layer String createTicketGrantingTicket(Cred) String grantServiceTicket(st, Service) String grantServiceTicket(st, Service, Cred) Assertion validateServiceTicket(st, Service) void destroyTicketGrantingTicket(st) String delegateTicketGrantingTicket(st, Cred)

22 Credentials Credentials is a marker interface (no methods) added to any class that may authenticate a user (X.509 Cert, Password, …) A Handler validates the credentials (The Cert was issued by a trusted CA) A Resolver maps the Credential to a netid (by extracting the Netid from, say, the first CN in the Cert DN)

23 CAS API Ticket CRUD Business Logic handler handler I do resolver resolver I do Ticket Cache Auth Mgr who handles this type of Credential? WebFlow Action Bean returns Credential Principal

24 Spring WebFlow URL mapped to WebFlow [new XML] Set Initial state ActionState runs a bean or makes a EL test. Success/Failure chooses new state ViewStates display a Form, input goes to an Action Bean An EndState releases Flow scoped objects Use for a single page is unexpected

25 Login Webflow /login Is a cookie/TGT provided Yes Issue ST No Gateway request Yes Redirect back No X.509 cert provided Yes Create TGT No Display the Form Submit Password Valid No Yes Create TGT

26 Trusted Other Cas /login Is a cookie/TGT provided Yes Issue ST No Gateway request Yes Redirect back No X.509 cert provided Yes Create TGT No ticket= present (and validates to other CAS) Yes Create TGT No Redirect to Other CAS

27 Add to WEB-INF/cas-servlet.xml

28 WEB-INF/login-webflow.xml … Note: now you never get here

29 CAS WebFlow Bean public final class PrincipalFromOtherCasNonInteractiveCredentialsAction extends AbstractNonInteractiveCredentialsAction implements ViewSelector { … protected Credentials constructCredentialsFromRequest( … return new PrincipalBearingCredentials( new SimplePrincipal(remoteUser));

30 CAS internal API mapped to WebFlow concepts Return null follows failure state change (View method redirects to other CAS) Return Credentials follows success state change (to Create TGT) deployerConfigContext.xml must have cas- server-support-trusted Handler and Resolver that process this type of Credentials

31 There can be more than one If you have more than one trustedOtherCas, each can have its own configured bean, but Each needs its own /loginXXX URL and its own WebFlow because the ticket= doesnt tell you which CAS it came from, so you have to know this based on the URL that CAS redirected back to

32 WEB-INF/deployerConfigContext.xml { "@context": "http://schema.org", "@type": "ImageObject", "contentUrl": "http://images.slideplayer.com/7/1699141/slides/slide_32.jpg", "name": "WEB-INF/deployerConfigContext.xml

33 cas-server-webapp/pom.xml org.jasig.cas cas-server-support-trusted ${project.version} org.jasig.cas cas-server-support-trusted-otherCAS ${project.version} org.jasig.cas cas-server-scripting ${project.version}

34 Browser Comes to CAS 3 Test Existing Cookie X509 Windows login Redirect to CAS 2

35 Redirect to Other CAS (CAS 2) display Form Validate password Issue TGT cookie Issue ST for CAS3

36 Redirect back to CAS 3 (as Other CAS Service) Validate CAS2 ST CAS2 Netid becomes CAS3 principal Issue CAS3 TGT cookie Issue CAS 3 ST Validate ticket= in cookie and ticket= back

37 Validate ST (with scripting) Script library Rhino JavaScript Engine Ticket Cache ScriptedValidateController ServiceValidate Controller Is ST valid? Is access permitted? handleRequestInternal()

38 Several ways to intercept the call to a single method Subclassing [requires removing final from parent class] Delegation: Create a separate ServiceValidateController bean instance AOP: Intercept the handleRequestInternal call, add script advice to the return

39 Success and Failure ViewName properties Subclass: one object (inherit the field) Delegate: ScriptedValidate is configured, then it sets the property value in the captive ServiceValidate object AOP: ???

40 cas-servlet.xml scriptedValidateController … List of beans that add variables to the JS environment... list of inline scripts keyed by URI … resource url of script files (file:. classpath:, http:, …)

41 There can be more than one You can have multiple /scriptedValidate URLs, with more than one Bean, with more than one configuration One for scripts with public data One for more carefully controlled scripts with access to more sensitive data …

42 /scriptedValidate,acscript=…uri…,… Service (through the configured Filter init- param) designates a script by URI Spring XML configuration passes a Map to the bean. The keys are URIs. The values are – The inline text of the script – A file (local path, in WAR, http: URL) – A directory (if the URI key ends in :*)

43 The Directory Rule The CAS XML Map associates cas:stuff:* with /usr/local/casscripts/ The Service sets acscript=cas:stuff:foo.js CAS runs /usr/local/casscripts/foo.js

44 Java 6 JS (Rhino) Bindings contains a Map Key becomes a JS variable name Java object becomes a JS object (script can reference properties, call methods) Rhino adds built in packages. and java. variables so script can use native Java objects, but we want to prevent access to local files and stuff.

45 Built-In JS Variables java and packages override netid is Principal ID request provided limited access to some HttpServletRequest info (parameters) log is log4j as in log.info(msg)

46 ObjectBuilder public interface ObjectBuilder { public abstract Map buildObjects(String netid);

47 LDAP Object Builder

48 JDBC Object Builder

49 ScriptedValidateController property

50 ScriptedValidateController [run the script] Object info = null; try { info = engine.eval(scriptReader, bindings); } catch (Exception e) { log.error("Error in the access control script: " + e); failClient("ScriptError","The access control script ended in error.", result); return result; } if (info instanceof String) {

51 Script Result The result of the script is the value of the last expression as in drop dead; or 666; Access permitted by or 0 Access refused if non-empty string or non zero number, but Nothing from the script is sent back to the service, just the OK or rejection.

52 Prereqs Modified version of CAS 3 client – Generates the acscript= parameter – processes ScriptReject validation failure response and turns it into a 403 Forbidden status.

53 Client CASValidateFilter org.jasig.cas.client.validation. Cas20ProxyReceivingTicketValidationFilter casServerUrlPrefix https://cas.example.com:8443/cas serverName http://cas.example.com:8080 scriptUri cas:some:name scriptParams group list or something

54 Research Add prepackaged script URIs acscript=cas:isInAdGroup, acparam=wizards Remote debug error messages for a script developer Mostly, how to turn this from a working testbed into a finished product.


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