Copyright 2002 Urbancode Software Development, Inc. All Rights Reserved. Developing with JAAS...

Copyright 2002 Urbancode Software Development, Inc. All Rights Reserved.

Developing with JAAS

Presented by Maciej Zawadzki

[email protected]


What is JAAS

• Java Authentication and Authorization Service

• Introduced as an optional package in J2SE 1.3

• Integrated into J2SE 1.4

• Implements a Java Pluggable Authentication Module (PAM) framework

• Access decisions are based on CodeSource and the user running the code


Goals

• JAAS is an extensive and complicated library.

• The goals for this presentation are:– To give an overview JAAS and its constituent parts

and illustrate how they all work together– Provide enough information that you will be able to

decide when it is appropriate to use JAAS– Provide an introduction on how to use JAAS; code

examples to help you get started


Outline

• Introduction– What is JAAS– Authentication vs. Authorization– Subject– Principal

• Authentication

• Authorization


Authentication vs. Authorization

• Authentication is the process of verifying the users’ identity. Typically this entails obtaining a user name and a password or some other credential from the user.

• Authorization is the process of verifying whether a user has access to protected resources.

Authentication

Andy

AuthenticationService

Is the user who hesays he is?

User NamePassword

Authorization

Andy

Resource

AuthorizationService

Some Action

Can this userperform this

action on me?


Overview of the Subject

• The Subject is a container for associated Principals, Public Credentials (public keys), and Private Credentials (passwords, private keys).

The Subject in Detail

Subject

PrincipalPrincipal

Principal

PublicCredential

PublicCredential

PublicCredential

PrivateCredential

PrivateCredential

PrivateCredential


Subject

1. package javax.security.auth;2. public class Subject {3. ...4.5. public Set getPrincipals() {}6. public Set getPrincipals(Class c) {}7.8. public Set getPrivateCredentials() {}9. public Set getPrivateCredentials(Class c) {}10.11. public Set getPublicCredentials() {}12. public Set getPublicCredentials(Class c) {}13.14. public boolean isReadOnly() {}15. public void setReadOnly() {}16.}


Principal

• A Principal identifies a Subject. The Subject can a person, a corporation, and application, etc.

• A single Subject may have many Principals that serve to identify the entity. For example, a user can have a user name principal, an employee id principal, social security number principal, etc.

1. package java.security;2. public interface Principal {3. ...4. public String getName();5. }


Obtaining a Specific Principal from a Subject

• Applications (and app. servers) typically adopt a convention stating that the Set of Principals on a Subject can only contain one instance of a particular Principal class.

1. // List the UserPrincipalExample principals2. Set userPrinSet = subject.getPrincipals(UserPrincipalExample.class);3. Iterator userPrinItr = userPrinSet.iterator();4. System.out.println("Found the following UserPrincipalsExample:");5. while (userPrinItr.hasNext()) {6. Principal p = (Principal) userPrinItr.next();7. System.out.println("\t" + p.toString());8. }


Outline

• Introduction

• Authentication

• Authorization


Pluggable Authentication Modules

• An application using JAAS for authentication can remain independent of the underlying authentication technology.

Pluggable Authentication

Login Modules

Application

Login Context

JndiLoginModule

NTLoginModule

UnixLoginModule

Krb5LoginModule

MyLoginModule

LDAP Server

DbLoginModule

NTAuthentication

UnixAuthentication

KerberosAuthentication

RDBMS

BiometricAuthentication


LoginConfiguration File

• The default implementation parses a configuration file in the above format

• Configuration file specified via java.security.auth.login.config System parameter

Application1 { ModuleClass Flag ModuleOptions;};Application2 { ModuleClass Flag ModuleOptions; ModuleClass Flag ModuleOptions;};other { ModuleClass Flag ModuleOptions; ModuleClass Flag ModuleOptions;};


LoginConfiguration Control Flags

• Required – The LoginModule is required to succeed. Regardless of success, authentication proceeds to next LoginModule

• Requisite – Is required to succeed. If succeeds, authentication proceeds. If fails, control returned.

• Sufficient – Not required to succeed. If suceeds, control returned. If fails, authentication proceeds.

• Optional – Not required to succeed. Regardless of success, authentication proceeds.

• Overall authentication succeeds if all Required and Requisite modules before a Sufficient module succeed.

• If not Required or Requisite modules are configured, then at least one Sufficient or Optional module must succeed.


Authentication Overview

1. The application creates a LoginContext and calls login()

2. The LoginContext refers to the LoginConfiguration to set up the appropriate LoginModules

3. The LoginContext delegates the authentication to the LoginModules

4. The LoginModules use the CallbackHandler to communicate with the application

Authentication Participants

Application

LoginContext

LoginConfiguration

LoginModule

LoginModule

LoginModuleCallback

Handler


Login Example

1. // Use the "Example" entry in the login configuration file2. // to authenticate users.3. LoginContext loginContext = null;4. try {5. loginContext = new LoginContext("Example",6. new ExampleCallbackHandler());7. loginContext.login();8. } catch (AccountExpiredException e) {9. ...10.} catch (CredentialExpiredException e) {11. ...12.} catch (FailedLoginException e) {13. ...14.} catch (LoginException e) {15. ...16.} catch (Exception e) {17. ...18.}


Login Example

• Once the login succeeds we can get the principal from the LoginContext and get the authenticated Principals from the Subject.

1. // List the Principals the authenticated user has2. Subject subject = loginContext.getSubject();3. Iterator principalItr = subject.getPrincipals().iterator();4. System.out.println("The authenticated user has the " +5. "following Principals:");6. while (principalItr.hasNext()) {7. Principal p = (Principal) principalItr.next();8. System.out.println("\t" + p.toString());9. }


Creating a LoginContext

• The name parameter is used to retrieve the appropriate login Configuration

• If a login Configuration with the specified name is not found, a default entry with the name “other” is used. If there is no Configuration with the name “other”, a LoginException is thrown

1. public class LoginContext {2. public LoginContext(String name) { ... }3. public LoginContext(String name, Subject subject) {...}4.5. public LoginContext(String name,6. CallbackHandler handler) { ... }7. public LoginContext(String name, Subject subject,8. CallbackHandler handler) { ... }9.10. ...11.}


Creating a LoginContext

• The constructors without a CallbackHandler either:– Rely on the default CallbackHandler specified in the java.security file under property named auth.login.defaultCallbackHandler

– Do not use a CallbackHandler and rely on the LoginModules to have another means of obtaining the information

• Callers of a LoginContext constructor require an AuthPermission with target “createLoginContext.<name>”


Logging In

• Authentication occurs with a call to the login() method• The login() method invokes all the configured LoginModules to perform authentication

• When authentication succeeds, the Subject can be retrieved using the getSubject() method

• The logout() method logs out the Subject and removes its authenticated Principals

• NTLoginModule – Authenticates against Windows Security Domain

1. public class LoginContext {2. ...3. public void login() throws LoginException { }4. public void logout() throws LoginException { }5. public Subject getSubject() { }6. }


LoginModule

• Two-phase authentication:– login() is 1st phase method– commit() and abort() are 2nd phase methods

1. package javax.security.auth.spi;

2. public interface LoginModule {3. public void initialize(Subject subject,4. CallbackHandler callbackHandler,5. Map sharedState,6. Map options);7. public boolean abort() throws LoginException;8. public boolean commit() throws LoginException;9. public boolean login() throws LoginException;10. public boolean logout() throws LoginException;11.}


LoginModules in J2SE 1.4

• JndiLoginModule – Authenticates against an LDAP tree

• Krb5LoginModule – Authenticates against a Kerberos domain

• UnixLoginModule – Authenticates against Unix security


Custom LoginModule Example

1. public boolean login()2. throws LoginException {3. Callback[] callbacks = new Callback[2];4. callbacks[0] = new NameCallback("userName: ");5. callbacks[1] = new PasswordCallback("password: ",false);6. try {7. callbackHandler.handle(callbacks);8. userName = ((NameCallback) callbacks[0]).getName();9. char[] charPass = ((PasswordCallback) callbacks[1])10. .getPassword();11. if (charPass == null) charPass = new char[0];12. password = new String(charPassword);13. } catch (IOException ioe) {14. ...15. } catch (UnsupportedCallbackException uce) {16. ...17. }18. if (isUserAuthentic()) succeeded = true;19.20. return succeeded;21.}


Callbacks

• javax.security.auth.callback.Callback Marker interface used to indicate a callback.

• Callbacks provide a means for the underlying authentication implementation to communicate with the application and obtains security data such as user name and password as well as provide information such as error and warning messages.

• Included callbacks:– NameCallback– PasswordCallback– TextOutputCallback– TextInputCallback– ChoiceCallback– ConfirmationCallback– LanguageCallback


CallbackHandler

1. package javax.security.auth.callback;

2. public interface CallbackHandler {3. public void handle(Callback[] callbacks)4. throws IOException, UnsupportedCallbackException;5. }


Custom CallbackHandler Example

1. public void handle(Callback[] callbacks)2. throws IOException, UnsupportedCallbackException {3. for (int i = 0; i < callbacks.length; i++) {4. if (callbacks[i] instanceof TextOutputCallback) {5. ...6. } else if(callbacks[i] instanceof NameCallback) {7. NameCallback nc = (NameCallback) callbacks[i];8. System.out.print(nc.getPrompt());9. System.out.flush();10. nc.setName(readLine());11. } else if(callbacks[i] instanceof PasswordCallback){12. PasswordCallback pc = (PasswordCallback)13. callbacks[i];14. System.out.print(pc.getPrompt());15. System.out.flush();16. pc.setPassword(readLine().toCharArray());17. } else {18. throw new UnsupportedCallbackException19. (callbacks[i], "Invalid Callback");20. }21. }22.}


Custom LoginConfiguration

• javax.security.auth.login.Configuration is an abstract Class used to specify which LoginModules should be used to Authenticate a user for a particular application

1. package javax.security.auth.login;2. public abstract class Configuration {3. ...4. public AppConfigurationEntry[]5. getAppConfigurationEntry(String name) {}6. }

1. package javax.security.auth.login;2. public class AppConfigurationEntry {3. public ... getControlFlag() {}4. public String getLoginModuleName() {}5. public Map getOptions() {}6. }


Custom LoginConfiguration

• You can configure the security system to use your own Configuration implementation by specifying the login.configuration.provider property in the <JRE_HOME>/lib/security/java.security file.

1. public AppConfigurationEntry[] getAppConfigurationEntry(String name) {2. AppConfigurationEntry[] entries = new AppConfigurationEntry[1];3.4. entries[0] = new AppConfigurationEntry(5. ExampleLoginModule.class.getName(),6. AppConfigurationEntry.LoginModuleControlFlag.REQUISITE,7. new HashMap());8.9. return entries;10. }


Outline

• Introduction

• Authentication

• Authorization


CodeSource Based Authorization

• Before the integration of JAAS with Java security, authorization decisions were strictly based on the CodeSource

• A Trusted Library may be given access to sensitive resources while an Applet or another Library may have that access restricted.

Code Source Based Authorization

FileSystem

NetworkSockets

SystemProperties

Applet

TrustedLibrary

Library X


CodeSource and Principal Based Authorization

• With the integration of JAAS and J2SE Security, authorization decisions can be made based on the CodeSource and the Principal.

• A Library may not have access privileges to resources when running without a User context or when being executed by User Bart, but when User Andy executes the Library those permissions may be granted.

Code Source and Principal BasedAuthorization

FileSystem

NetworkSockets

SystemProperties

Library X

Andy

Bart


CodeSource & ProtectionDomain

• The CodeSource of a piece of Java code is the URL location that the code was loaded from and the Certificates that we used to sign the code

• The ProtectionDomain is a holder for the CodeSource and a Principal

• Each class is assigned a ProtectionDomain upon being loaded. The Principal is null when the class is first loaded.

ProtectionDomain

CodeSource

CodeSource

URL

Certificate

ProtectionDomain

CodeSource

Principal

Class


AccessControlContext – a Context for Authorization Decisions

• When making access decisions, the security system looks at every ProtectionDomain involved in the call. Access is granted only if every ProtectionDomain in the Context can have access.

• A less privileged PD can not gain privilege by calling a more privileged PD. And a more privileged PD must lose privilege when calling a less privileged PD. This is the principle of least privilege.

Authorization Context

ContextStack Snapshot

AccessController.checkPermission()

java.io.FileInputStream()

java.io.FileReader()

ReadTestFileUseCase.apply()

AuthorizationTestHarness.run()

...

Class

Class

Class

Class

Class

Class

PD

PD

PD

PD

PD

PD


Permission

• Permissions represent access to resources.• All Permission object have a name. The

meaning of the name parameter is implementation dependent. Typically the name identifies the resource to be accessed.

1. package java.security;2. public abstract class Permission {3. public Permission (String name) {}4. public abstract boolean implies(Permission p) {}5. public abstract boolean equals(Object o) {}6. public String toString() {}7. public PermissionCollection newPermissionCollection() {}8. }


Permission

• The implies() method is implementation dependent. A permission p1 implies permission p2 if the grant of p1 is also meant to grant p2.

• Additional parameter called actions can be used to identify the type of access to the resource allowed.

• New Permissions are subclassed from Permission or from one of its existing subclasses such as java.security.BasicPermission.

• A special permission exists to indicate unrestricted access to all resource: java.security.AllPermission


Policy

• The mapping between PDs and associated Permissions is stored by the Policy.

• Policy is a singleton.

Policy Holds a Mapping of ProtectionDomain toPermissions

Policy

ProtectionDomain

ProtectionDomain

ProtectionDomain

PermissionCollection Permission

PermissionPermission






Policy

• The default implementation of Policy accepts text based configuration in the above format

• Each grant entry is composed of an optional CodeSource, Signers, Principals, and a list of Permissions

• Default security policy is <JRE_HOME>/lib/security/java.policy• Can provide supplemental policy file location via

– -Djava.security.policy=<file> JVM parameter

• Can override the default policy file with:– -Djava.security.policy==<file> JVM parameter

1. grant [CodeBase <URL>,] [Signedby <signers>,]2. [Principal <Principal_Class> <Principal_Name>] {3. Permission <Permission_Class> [<Target_Name>]4. [, <Permission_Actions>]5. [, signedBy <Signer_Name>];6. };


AccessController

• Your code would verify that the current context has a permission by creating a new instance of the permission in question and calling AccessController.checkPermission(p) ;

1. MyPermission p = new MyPermission(fileName, "display");2. AccessController.checkPermission(p);


AccessController

• The AccessController embodies the access control algorithm.

• It obtains the current AccessControlContext, which has an array of PDs and then for each PD checks whether the PD has the requested permission.

Authorization Participants

ProtectionDomain

CodeSource

Principal

PermissionCollection


PermissionPolicy

Class

AccessControlContext

AccessController


AccessController

1. package java.security;2. public final class AccessController {3. static public void checkPermission(Permission p) {}4. static public Object doPrivileged(PrivilegedAction pa) {}5. static public Object doPrivileged(PrivilegedAction pa,6. AccessControlContext ctx) {}7. static public Object doPrivileged(PrivilegedExceptionAction pa){}8. static public Object doPrivileged(PrivilegedExceptionAction pa,9. AccessControlContext ctx) {}10. static public AccessControlContext getContext() {}11. }


PrivilegedAction

• When a trusted library invokes a PrivilegedAction, the permissions of PDs in the call stack prior to the PrivilegedAction do not get checked.

Using a PrivilegedAction Truncates the AccessControlContext

ContextStack Snapshot

AccessController.checkPermission()

java.io.FileInputStream()

java.io.FileReader()

Trusted Library

Your Application

Your Application

Class

Class

Class

Class

Class

Class

PD

PD

PD

PD


PrivilegedAction

• Invoking a privileged action is done via a static method on the AccessController.

• PrivilegedExceptionAction can throw an Exception.• Methods invoking a PrivilegedAction should not return

references to resources.

1. AccessController.doPrivileged(2. new PrivilegedAction() {3. public Object run() {4. ...5. return null;6. }7. });


Associating a Subject with an Access Control Context

• To associate a Subject with the current execution context, one of the Subject.doAs(…) methods must be used.

1. package javax.security.auth;2. public class Subject {3. ...4.5. static public Object doAs(Subject s, PrivilegedAction pa) {}6. static public Object doAs(Subject s, PrivilegedExceptionAction pa){}7. static public Object doAsPrivileged(Subject s,8. PrivilegedAction pa) {}9. static public Object doAsPrivileged(Subject s,10. PrivilegedExceptionAction pa) {}11.}


Custom Policy

• You can substitute your own Policy implementation for the default one in one of two ways:– At runtime by calling Policy.setPolicy()– By changing the value of policy.provider property in

<JRE_HOME>/lib/security/java.security• The specified class name must point to a subclass of

Policy, and• The specified class must be in the boot classpath• Example included (you must change the java.security

property on your JRE)


Downloads

• All source code is included on your CDs

• You can check http://www.urbancode.com/presentations/ for updates


Evaluations

• Please fill out your speaker evaluations and drop them off at the registration desk

• Please fill out the comments:– What was the best part of the presentation– What part put you most to sleep


Thank you!Maciej Zawadzki

[email protected]

Copyright 2002 Urbancode Software Development, Inc. All Rights Reserved. Developing with JAAS...

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