JAAS Application Programming Interface Developer's Guide

Java Authentication and Authorization Service (JAAS) 1.0

Developer's Guide

Overview
Who Should Read This Document
Related Documentation
Introduction
Core Classes
Common Classes
Subject
Principals
Credentials
Authentication Classes
LoginContext
LoginModule
CallbackHandler
Callback
Authorization Classes
Policy
AuthPermission
PrivateCredentialPermission
Implementation
"Hello World", JAAS style!
Appendix A: JAAS Settings in the java.security Security Properties File
Appendix B: Login Configuration File
Appendix C: Authorization Policy File
Appendix D: ThreadSubject (NT, Windows 2000, Windows 2000 64 Bit, and OS/390)
Appendix E: SAFPermission for OS/390 JAAS
Appendix F: OS/390 LoginModule

Overview
The Java Authentication and Authorization Service (JAAS) is a standard extension to the Java 2 Software Development Kit, v 1.3.1. Currently, Java 2 provides codesource-based access controls (access controls based on where the code originated from and who signed the code). It lacks, however, the ability to additionally enforce access controls based on who runs the code. JAAS provides a framework that augments the Java 2 security model with such support.
Who Should Read This Document
This document is intended for experienced programmers wishing to create applications constrained by a CodeSource-based and Subject-based security model.
Related Documentation
This document assumes you have already read the following documentation:

Java 2 Software Development Kit, v 1.3.1, API Specification

JAAS API Specification

Java Security Architecture (Java 2 Platform, Standard Edition, v 1.3.1)

A supplement to this guide is the LoginModule Developer's Guide.
Introduction
The JAAS infrastructure can be divided into two main components: an authentication component and an authorization component. The JAAS authentication component provides the ability to reliably and securely determine who is currently executing Java code, regardless of whether the code is running as an application, an applet, a bean, or a servlet. The JAAS authorization component supplements the existing Java 2 security framework by providing the means to restrict the executing Java code from performing sensitive tasks, depending on its codesource (as is done in Java 2) and depending on who was authenticated.
JAAS authentication is performed in a pluggable fashion. This permits Java applications to remain independent from underlying authentication technologies. Therefore new or updated authentication technologies can be plugged under an application without requiring modifications to the application itself. Applications enable the authentication process by instantiating a LoginContext object, which in turn references a Configuration to determine the authentication technology, or LoginModule, to be used in performing the authentication. Typical LoginModules may prompt for and verify a username and password. Others may read and verify a voice or fingerprint sample.
Once the user executing the code has been authenticated, the JAAS authorization component works in conjunction with the existing Java 2 access control model to protect access to sensitive resources. Unlike in Java 2, where access control decisions are based solely on code location and code signers (a CodeSource), in JAAS access control decisions are based both on the executing code's CodeSource, as well as on the user running the code, or the Subject. Note that the JAAS policy merely extends the Java 2 policy with the relevant Subject-based information. Therefore permissions recognized and understood in Java 2 (java.io.FilePermission and java.net.SocketPermission, for example) are also understood and recognized by JAAS. Furthermore, although the JAAS security policy is physically separate from the existing Java 2 security policy, the two policies, together, form one logical policy.

Core Classes
The JAAS core classes can be broken into 3 categories: Common, Authentication, and Authorization.

Common Classes

Subject, Principals, Credentials

Authentication Classes

LoginContext, LoginModule, CallbackHandler, Callback

Authorization Classes

Policy, AuthPermission, PrivateCredentialPermission

Common Classes
Common classes are shared within both the JAAS authentication and authorization components.
The key JAAS class is Subject, which represents a grouping of related information for a single entity such as a person. It encompasses the entity's Principals, public credentials, and private credentials.
Note that JAAS uses the existing Java 2 java.security.Principal interface to represent a Principal. Also note that JAAS does not introduce a separate credential interface or class. A credential, as defined by JAAS, may be any Object.

Subject
To authorize access to resources, applications first need to authenticate the source of the request. The JAAS framework defines the term, Subject, to represent the source of a request. A Subject may be any entity, such as a person or service. Once authenticated, a Subject is populated with associated identities, or Principals. A Subject may have many Principals. For example, a person may have a name Principal ("John Doe") and a SSN Principal ("123-45-6789") which distinguishes it from other Subjects.
A Subject may also own security-related attributes, which are referred to as credentials. Sensitive credentials that require special protection, such as private cryptographic keys, are stored within a private credential Set. Credentials intended to be shared, such as public key certificates or Kerberos tickets are stored within a public credential Set. Different permissions are required to access and modify the different credential Sets.
Subjects are created using these constructors:
    public Subject();

    public Subject(boolean readOnly, Set principals,
                   Set pubCredentials, Set privCredentials);
The first constructor creates a Subject with empty (non-null) Sets of Principals and credentials. The second constructor creates a Subject with the specified Sets of Principals and credentials. It also has a boolean argument which can create a read-only Subject (immutable Principal and credential Sets).
An alternative way to obtain a reference to an authenticated Subject without using these constructors will be shown in the LoginContext section.
If a Subject was not instanitated to be in a read-only state, it can be set to a read-only state by calling this method:
    public void setReadOnly();
An AuthPermission("setReadOnly") is required to invoke this method. Once in a read-only state, any attempt to add or remove Principals or credentials will result in an IllegalStateException being thrown.
This method may be called to test a Subject's read-only state:
    public boolean isReadOnly();
To retrieve the Principals associated with a Subject, two methods are available:
    public Set getPrincipals();
    public Set getPrincipals(Class c);
The first method returns all Principals contained in the Subject, while the second method only returns those Principals that are an instance of the specified Class c, or an instance of a subclass of Class c. An empty set will be returned if the Subject does not have any associated Principals.
To retrieve the public credentials associated with a Subject, these methods are available:
    public Set getPublicCredentials();
    public Set getPublicCredentials(Class c);
The observed behavior of these methods is identical to that for the getPrincipals method.
To access private credentials associated with a Subject, the following methods are available:
    public Set getPrivateCredentials();
    public Set getPrivateCredentials(Class c);
The observed behavior of these methods is identical to that for the getPrincipals and getPublicCredentials methods.
To modify or operate upon a Subject's Principal Set, public credential Set, or private credential Set, callers use the methods defined in the java.util.Set class. The following example demonstrates this:
    Subject subject;
    Principal principal;
    Object credential;

    // add a Principal and credential to the Subject
    subject.getPrincipals().add(principal);
    subject.getPublicCredentials().add(credential);
Note that an AuthPermission("modifyPrincipals"), AuthPermission("modifyPublicCredentials"), or AuthPermission("modifyPrivateCredentials") is required to modify the respective Sets. Also note that only the sets returned via the getPrincipals, getPublicCredentials, and getPrivateCredentials methods are backed by the Subject's respective internal sets. Therefore any modification to the returned set affects the internal sets as well. The sets returned via the getPrincipals(Class c), getPublicCredentials(Class c), and getPrivateCredentials(Class c) methods are not backed by the Subject's respective internal sets. A new set is created and returned for each method invocation. Modifications to these sets will not affect the Subject's internal sets. The following method returns the Subject associated with the specified AccessControlContext, or null if no Subject is associated with the specified AccessControlContext.
    public static Subject getSubject(final AccessControlContext acc);
An AuthPermission("getSubject") is required to call Subject.getSubject.
The Subject class also includes these methods inherited from java.lang.Object:
    public boolean equals(Object o);
    public String toString();
    public int hashCode();
The following static methods may be called to perform work as a particular Subject:
    public static Object doAs(final Subject subject,
                         final java.security.PrivilegedAction action);

    public static Object doAs(final Subject subject,
                         final java.security.PrivilegedExceptionAction action)
                         throws java.security.PrivilegedActionException;
Both methods first associate the specified subject with the current Thread's AccessControlContext, and then execute the action. This achieves the effect of having the action run as the subject. The first method can throw runtime exceptions but normal execution has it returning an Object from the run() method of its action argument. The second method behaves similarly except that it can throw a checked exception from its PrivilegedExceptionAction run() method. An AuthPermission("doAs") is required to call the doAs methods.
Here are two examples utilizing the first doAs method. Assume that a Subject with a Principal of class com.ibm.security.Principal named "BOB" has been authenticated by a LoginContext "lc". Also, assume that a SecurityManager has been installed, and the following exists in the JAAS access control policy (see the Policy section for more details on the JAAS policy file):
   // Grant "BOB" permission to read the file "foo.txt"
   grant Principal com.ibm.security.Principal "BOB" {
      permission java.io.FilePermission "foo.txt", "read";
};
Subject.doAs Example 1
    class ExampleAction implements java.security.PrivilegedAction {
        public Object run() {
            java.io.File f = new java.io.File("foo.txt");

            // exists() invokes a security check
            if (f.exists()) {
                System.out.println("File foo.txt exists.");
            }
            return null;
        }
    }

    public class Example1 {
        public static void main(String[] args) {

            // Authenticate the subject, "BOB".
            // This process is described in the
            // LoginContext section.

            Subject bob;
            ...

            // perform "ExampleAction" as "BOB":
            Subject.doAs(bob, new ExampleAction());
        }
    }
During execution, ExampleAction will encounter a security check when it makes a call to, f.exists(). However, since ExampleAction is running as "BOB", and because the JAAS policy (above) grants the necessary FilePermission to "BOB", the ExampleAction will pass the security check.
Example 2 has the same scenario as Example 1.
Subject.doAs Example 2
    public class Example2 {
        // Example of using an anonymous action class.
        public static void main(String[] args) {
            // Authenticate the subject, "BOB".
            // This process is described in the
            // LoginContext section.

            Subject bob;
            ...

            // perform "ExampleAction" as "BOB":
            Subject.doAs(bob, new ExampleAction() {
                public Object run() {
                    java.io.File f = new java.io.File("foo.txt");
                    if (f.exists()) {
                        System.out.println("File foo.txt exists.");
                    }
                    return null;
                }
            });
        }
    }
Both examples throw a SecurityException if the example permission grant statement is altered correctly, such as adding an incorrect CodeBase or changing the Principal to "MOE". Removing the Principal field from the grant block and then moving it to a Java 2 policy file will not cause a SecurityException to be thrown because the permission is more general now (available to all Principals).
Since both examples perform the same function, there must be a reason to write code one way over the other. Example 1 may be easier to read for some programmers unfamiliar with anonymous classes. Also, the action class could be placed in a separate file with a unique CodeBase and then the permission grant could utilize this information. Example 2 is more compact and the action to be performed is easier to find since it is right there in the doAs call.
The following methods also perform work as a particular Subject. However, the doAsPrivileged methods will have security checks based on the supplied action and subject. The supplied context will be tied to the specified subject and action. A null context object will disregard the current AccessControlContext altogether.
    public static Object doAsPrivileged(final Subject subject,
                         final java.security.PrivilegedAction action,
                         final java.security.AccessControlContext acc);

    public static Object doAsPrivileged(final Subject subject,
                         final java.security.PrivilegedExceptionAction action,
                         final java.security.AccessControlContext acc)
                         throws java.security.PrivilegedActionException;
The doAsPrivileged methods behave similarly to the doAs methods: the subject is associated with the context acc, an action is performed, and runtime exceptions or checked exceptions may be thrown. However, the doAsPrivileged methods first empties the existing Thread's AccessControlContext before associating the subject with the supplied context, and before invoking the action. A null acc argument has the effect of causing access control decisions (invoked while the action executes) to be based solely upon the subject and action. An AuthPermission("doAsPrivileged") is required when calling the doAsPrivileged methods.

Principals
As mentioned previously, Principals may be associated with a Subject. Principals represent Subject identities, and must implement the java.security.Principal and java.io.Serializable interfaces. The Subject section describes ways to update the Principals associated with a Subject.

Credentials
Public and private credential classes are not part of the core JAAS class library. Any java class, therefore, can represent a credential. However, developers may elect to have their credential classes implement two interfaces related to credentials: Refreshable and Destroyable.
Refreshable
This interface provides the capability for a credential to refresh itself. For example, a credential with a particular time-restricted lifespan may implement this interface to allow callers to refresh the time period for which it is valid. The interface has two abstract methods:
    boolean isCurrent();
Determines if the credential is current or valid.
    void refresh() throws RefreshFailedException;
Updates or extends the validity of the credential. This method implementation should perform an AuthPermission("refreshCredential") security check to ensure the caller has permission to refresh the credential.
Destroyable
This interface provides the capability of destroying the contents within a credential. The interface has two abstract methods:
    boolean isDestroyed();
Determines if the credential has been destroyed.
    void destroy() throws DestroyFailedException;
Destroys and clears the information associated with this credential. Subsequent calls to certain methods on this credential will result in an IllegalStateException being thrown. This method implementation should perform an AuthPermission("destroyCredential") security check to ensure the caller has permission to destroy the credential.
Authentication Classes
To authenticate a Subject, the following steps are performed:

An application instantiates a LoginContext.

The LoginContext consults a Configuration to load all of the LoginModules configured for that application.

The application invokes the LoginContext's login method.

The login method invokes all of the loaded LoginModules. Each LoginModule attempts to authenticate the Subject. Upon success, LoginModules associate relevant Principals and credentials with the Subject.

The LoginContext returns the authentication status to the application.

If authentication succeeded, the application retrieves the authenticated Subject from the LoginContext.

LoginContext
The LoginContext class provides the basic methods used to authenticate Subjects, and provides a way to develop an application independent of the underlying authentication technology. The LoginContext consults a Configuration to determine the authentication services, or LoginModules, configured for a particular application. Therefore, different LoginModules can be plugged in under an application without requiring any modifications to the application itself.
LoginContext offers four constructors to choose from:
    public LoginContext(String name) throws LoginException;

    public LoginContext(String name, Subject subject) throws LoginException;

    public LoginContext(String name, CallbackHandler callbackHandler)
           throws LoginException

    public LoginContext(String name, Subject subject,
           CallbackHandler callbackHandler) throws LoginException
All of the constructors share a common parameter: name. This argument is used by the LoginContext to index the login Configuration. Constructors that do not take a Subject as an input parameter instantiate a new Subject. Null inputs are disallowed for all constructors. Callers require an AuthPermission("createLoginContext") to instantiate a LoginContext.
Actual authentication occurs with a call to the following method:
    public void login() throws LoginException;
When login is invoked, all of the configured LoginModules' respective login methods are invoked to perform the authentication. If the authentication succeeded, the authenticated Subject (which may now hold Principals, public credentials, and private credentials) can be retrieved by using the following method:
    public Subject getSubject();
To logout a Subject and remove its authenticated Principals and credentials, the following method is provided:
    public void logout() throws LoginException;
The following snippet of code in an application will authenticate a Subject called "bob" after accessing a configuration file with a configuration entry named "moduleFoo":
    Subject bob = new Subject();
    LoginContext lc = new LoginContext("moduleFoo", bob);
    try {
        lc.login();
        System.out.println("authentication successful");
    } catch (LoginException le) {
        System.out.println("authentication unsuccessful"+le.printStackTrace());
    }
This snippet of code in an application will authenticate a "nameless" Subject and then use the getSubject method to retrieve it:
    LoginContext lc = new LoginContext("moduleFoo");
    try {
        lc.login();
        System.out.println("authentication successful");
    } catch (LoginException le) {
        System.out.println("authentication unsuccessful"+le.printStackTrace());
    }
    Subject subject = lc.getSubject();
If the authentication failed, then getSubject returns null. Also, there isn't an AuthPermission("getSubject") required to do this as is the case for Subject.getSubject.

LoginModule
The LoginModule interface gives developers the ability to implement different kinds of authentication technologies that can be plugged under an application. For example, one type of LoginModule may perform a username/password-based form of authentication.
The LoginModule Developer's Guide is a detailed document that gives developers step-by-step instructions for implementing LoginModules.
To instantiate a LoginModule, a LoginContext expects each LoginModule to provide a public constructor that takes no arguments. Then, to initialize a LoginModule with the relevant information, a LoginContext calls the LoginModule's initalize method. The provided subject is guaranteed to be non-null.
   void initialize(Subject subject, CallbackHandler callbackHandler,
                Map sharedState, Map options);
This following method begins the authentication process:
     boolean login() throws LoginException;
An example method implementation may prompt the user for a username and password, and then verify the information against the data stored in a naming service such as NIS or LDAP. Alternative implementations might interface smart cards and biometric devices, or may simply extract user information from the underlying operating system. This is considered phase 1 of the JAAS authentication process.
The following method completes and finalizes the authentication proces:
     boolean commit() throws LoginException;
If phase 1 of the authentication process was successful, then this method continues with phase 2: associating Principals, public credentials, and private credentials with the Subject. If phase 1 failed, then the commit method removes any previously stored authentication state, such as usernames and passwords.
The following method halts the authentication process if phase 1 was unsuccessful:
    boolean abort() throws LoginException;
Typical implementations of this method clean up previously stored authentication state, such as usernames or passwords. The following method logs out a Subject:
    boolean logout() throws LoginException;
This method removes the Principals and credentials originally associated with the Subject during the commit operation. Credentials should be destroyed upon removal.

CallbackHandler
In some cases a LoginModule must communicate with the user to obtain authentication information. LoginModules use a CallbackHandler for this purpose. Applications implement the CallbackHandler interface and pass it to the LoginContext, which forwards it directly to the underlying LoginModules. LoginModules use the CallbackHandler both to gather input from users (such as a password or smart card pin number) or to supply information to users (such as status information). By allowing the application to specify the CallbackHandler, underlying LoginModules can remain independent of the different ways applications interact with users. For example, the implementation of a CallbackHandler for a GUI application might display a Window to solicit input from a user. On the other hand, the implementation of a CallbackHandler for a non-GUI tool might simply prompt the user for input directly from the command line.
CallbackHandler is an interface with one method to implement:
     void handle(Callback[] callbacks)
     throws java.io.IOException, UnsupportedCallbackException;
The CallbackHandler javadocs have a lengthy example not included in this document readers may want to examine.

Callback
The javax.security.auth.callback package contains the Callback interface as well as several implementations. LoginModules may pass an array of Callbacks directly to the handle method of a CallbackHandler.
Please consult the various Callback APIs for more information on their use.
Authorization Classes
Upon successful authentication of a Subject, fine-grained access controls can be placed upon that Subject by invoking the Subject.doAs or Subject.doAsPrivileged methods. The permissions granted to that Subject are configured in a JAAS Policy.

Policy
This is an abstract class for representing the system-wide JAAS access control. As a default, JAAS provides a file-based subclass implementation, PolicyFile. Each Policy subclass must implement the following methods:
    public abstract java.security.PermissionCollection getPermissions
                                        (Subject subject,
                                        java.security.CodeSource cs);
    public abstract void refresh();
The getPermissions method returns the permissions granted to the specified Subject and CodeSource. The refresh method updates the runtime Policy with any modifications made since the last time it was loaded from its permanent store (a file or database, for example). The refresh method requires an AuthPermission("refreshPolicy").
The following method retrieves the current runtime Policy object, and is protected with a security check that requires the caller to have an AuthPermission("getPolicy").
    public static Policy getPolicy();
The following example code demonstrates how a Policy object can be queried for the set of permissions granted to the specified Subject and CodeSource:
    policy = Policy.getPolicy();
    PermissionCollection perms = policy.getPermissions(subject, codeSource);
To set a new Policy object for the Java runtime, the Policy.setPolicy method may be used. This method requires the caller to have an AuthPermission("setPolicy").
    public static void setPolicy(Policy policy);
Policy File Sample Entries:
These examples are relevant only for the default PolicyFile implementation.
Each entry in the Policy is represented as a grant entry. Each grant entry specifies a codebase/code-signers/Principals triplet, as well as the Permissions granted to that triplet. Specifically, the permissions will be granted to any code downloaded from the specified codebase and signed by the specified code signers, so long as the Subject running that code has all of the specified Principals in its Principal set. Refer to the Subject.doAs examples to see how a Subject becomes associated with running code.
    grant CodeBase ["URL"],
          Signedby ["signers"],
          Principal [Principal_Class] "Principal_Name",
          Principal ... {
        permission Permission_Class ["Target_Name"]
                                    [, "Permission_Actions"]
                                    [, signedBy "SignerName"];
    };

    // example grant entry (Unix)
    grant CodeBase "http://griffin.ibm.com", Signedby "davis",
          Principal com.ibm.security.auth.UsernamePrincipal "kent" {
        permission java.io.FilePermission "/home/kent/files/*", "read, write";
    };
    
    // example grant entry (Windows)
    grant CodeBase "http://griffin.ibm.com", Signedby "davis",
          Principal com.ibm.security.auth.UsernamePrincipal "kent" {
        permission java.io.FilePermission "c:/kent/files/*", "read, write";
    };
If no Principal information is specified in the JAAS Policy grant entry, a parsing exception will be thrown. However, grant entries that already exist in the regular Java 2 codesource-based policy file (and therefore have no Principal information) are still valid. In those cases, the Principal information is implied to be '*' (the grant entries applies to all Principals).
The CodeBase and Signedby components of the grant entry are optional in the JAAS Policy. If they are not present, then any codebase will match, and any signer (including unsigned code) will match.
In the example above, the grant entry specifies that code downloaded from "http://griffin.ibm.com", signed by "davis", and running as the user "kent", has one Permission. This Permission permits the executing code to read and write files in the directory "/home/kent/files" (Unix) or "c:\kent\files\*" (Windows).
Multiple Principals may be listed within one grant entry. The current Subject running the code must have all of the specified Principals in its Principal set to be granted the entry's Permissions.
    grant Principal com.ibm.security.auth.UsernamePrincipal "kent",
              Principal com.ibm.security.auth.UserIDPrincipal "10" {
            permission java.io.FilePermission "/home/kent/*", "read, write";
            permission java.net.SocketPermission "griffin.ibm.com", "connect";
    };
This entry grants any code running as both the Unix user "kent" with the Unix user identification number "10", permission to read and write files in kent's home directory, as well as permission to make socket connections to "griffin.ibm.com".

AuthPermission
This class encapsulates the basic permissions required for JAAS. An AuthPermission contains a name (also referred to as a "target name") but no actions list; you either have the named permission or you don't. In addition to inherited methods (from the Permission class), an AuthPermission has two public constructors:
    public AuthPermission(String name);
    public AuthPermission(String name, String actions);
The first constructor creates a new AuthPermission with the specified name. The second constructor also creates a new AuthPermission object with the specified name, but has an additional actions argument which is currently unused and should be null. This constructor exists solely for the Policy object to instantiate new Permission objects. For most code, the first constructor is appropriate.
Currently the AuthPermission object is used to guard access to the Policy, Subject, LoginContext, and Configuration objects. Please refer to the AuthPermission javadocs for the list of valid names that are supported.

PrivateCredentialPermission
This class protects access to a Subject's private credentials and provides one public constructor:
    public PrivateCredentialPermission(String name, String actions);
Please refer to the PrivateCredentialPermission javadocs for more detailed information on this class.

Implementation
Note: Appendix A contains a sample java.security file that includes the static properties mentioned here.
Because there exists default values for JAAS providers and policy files, users need not statically (in the java.security file) nor dynamically (command line -D option) list their values in order to implement JAAS. Also, the default configuration and policy file providers may be replaced by a user-developed provider. Therefore this section is an attempt to explain the JAAS default providers and policy files as well as the properties that enable alternative providers.
If desirable, read the Default Policy File API and Default Configuration File API for more information than is summarized here.
Authentication Provider
The authentication provider, or configuration class, is statically set with login.configuration.provider=[class] in the java.security file. This provider creates the Configuration object.
For example:
  login.configuration.provider=com.foo.Config
If the Security property login.configuration.provider is not found in java.security, then JAAS will set it to the default value:
com.ibm.security.auth.login.ConfigFile.
If a security manager is set before the Configuration is created, then an AuthPermission("getLoginConfiguration") will be required to be granted.
There isn't a way to dynamically set the configuration provider on the command line.
Authentication Configuration File
The authentication configuration files may be statically set in java.security with login.config.url.n=[URL], where n is a consecutively number integer starting with 1. The format is identical to the format for Java security policy files (policy.url.n=[URL]).
If the Security property policy.allowSystemProperty is set to "true" in java.security, then users can dynamically set policy files on the command line utilizing the -D option with this property: java.security.auth.login.config. The value may be a path or URL. For example,
(Unix):
  ... -Djava.security.auth.login.config=/usr/config_policy/login.config ...
  or
  ... -Djava.security.auth.login.config=file:/usr/config_policy/login.config ...
(Windows):
  ... -Djava.security.auth.login.config=c:\config_policy\login.config ...
  or
  ... -Djava.security.auth.login.config=file:c:/config_policy/login.config ...
Note: using double equal signs (==) on the command line allows a user to override all other policy files found.
If no configuration files can be found statically or dynamically, JAAS will try to load the configuration file from this default location: ${user.home}/.java.login.config where ${user.home} is a system dependent location.
Authorization Provider
The authorization provider, or JAAS Policy class, is statically set with auth.policy.provider=[class] in the java.security file. This provider creates the JAAS Subject-based Policy object.
For example:
  auth.policy.provider=com.foo.Policy
If the Security property auth.policy.provider is not found in java.security, then JAAS will set it to the default value:
com.ibm.security.auth.PolicyFile.
If a security manager is set before the Configuration is created, then an AuthPermission("getPolicy") will be required to be granted.
There isn't a way to dynamically set the authorization provider on the command line.
Authorization Policy File
The authorization policy files may be statically set in java.security with auth.policy.url.n=[URL], where n is a consecutively number integer starting with 1. The format is identical to the format for Java security policy files (policy.url.n=[URL]).
If the Security property policy.allowSystemProperty is set to "true" in java.security, then users can dynamically set policy files on the command line utilizing the -D option with this property: java.security.auth.policy. The value may be a path or URL. For example,
(Unix):
  ... -Djava.security.auth.policy=/usr/auth_policy/java.auth.policy ...
  or
  ... -Djava.security.auth.policy=file:/usr/auth_policy/java.auth.policy ...
(Windows)
  ... -Djava.security.auth.policy=c:\auth_policy\java.auth.policy ...
  or
  ... -Djava.security.auth.policy=file:c:/auth_policy/java.auth.policy ...
Note: using double equal signs (==) on the command line allows a user to override all other policy files found.
There is not a default location to load an authorization policy from.

"Hello World", JAAS style!
Put on your dark sunglasses and favorite fedora hat, then grab an alto sax ... it's time to get JAAS-y! Yes, another "Hello World!" program. In this section, a program will be made available to test your JAAS installation.
Installation
It is assumed that JAAS has been installed. For example, the JAAS JAR files have been copied to your Development Kit's extensions directory.
Retrieve Files
Download the tar">HelloWorld.tar to your test directory. Expand it using "jar xvf HelloWorld.tar".
You should verify the contents of your test directory. source files:

HWLoginModule.java

HWPrincipal.java

HelloWorld.java

class files

The source files have been precompiled for you into the classes directory.

policy files

jaas.config

java2.policy

jaas.policy

Compile Source Files
NOTE: the example uses Windows-style file separators ("\"). Unix users should substitute forward slashes ("/") in the example.
The three source files, HWLoginModule.java, HWPrincipal.java and HelloWorld.java, are already compiled and therefore do not need to be compiled.
If any of the source files are modified, then change to the test directory that they were saved to and enter:
javac -d .\classes *.java
The classpath should need the classes directory (.\classes) added to it in order to compile the classes.
Note: HWLoginModule and HWPrincipal are in the com.ibm.security package and will be created in the appropriate directory during compilation (\classes\com\ibm\security).
Examine Policy Files
The configuration file, jaas.config, contains one entry:
helloWorld {
   com.ibm.security.HWLoginModule required debug=true;
};
Only one LoginModule is supplied with the test case. When executing the HelloWorld application, please experiment by changing the LoginModuleControlFlag (required, requisite, sufficient, optional) and deleting the debug flag. If more LoginModules are available for testing, then feel free to alter this configuration and experiment with multiple LoginModules. HWLoginModule will be discussed shortly.
The Java 2 policy file, java2.policy, contains one permission block:
grant {
   permission javax.security.auth.AuthPermission "createLoginContext";
   permission javax.security.auth.AuthPermission "modifyPrincipals";
   permission javax.security.auth.AuthPermission "doAsPrivileged";
};
The three permissions are required because the HelloWorld application (1) creates a LoginContext object, (2) modifies the Principals of the the authenticated Subject and (3) calls the doAsPrivileged method of the Subject class.
The JAAS policy file, jaas.policy, also contains one permission block:
grant Principal com.ibm.security.HWPrincipal "bob" {
   permission java.util.PropertyPermission "java.home", "read";
   permission java.util.PropertyPermission "user.home", "read";
   permission java.io.FilePermission "foo.txt", "read";
};
The three permissions are initially granted to an HWPrincipal named bob. The actual Principal added to the authenticated Subject is the username used during the login process (more later). Here's the action code from HelloWorld with the three system calls (the reason for the required permissions) in bold:
Subject.doAsPrivileged(lc.getSubject(), new PrivilegedAction() {
    public Object run() {
        System.out.println("\nYour java.home property: "
                               +System.getProperty("java.home"));

        System.out.println("\nYour user.home property: "
                               +System.getProperty("user.home"));

        File f = new File("foo.txt");
        System.out.print("\nfoo.txt does ");
        if (!f.exists()) System.out.print("not ");
        System.out.println("exist in your current directory");

        System.out.println("\nOh, by the way ...");

        try {
            Thread.currentThread().sleep(2000);
        } catch (Exception e) {
            // ignore
        }
        System.out.println("\n\nHello World!\n");
        return null;
    }
}, null);
When executing the HelloWorld program, use various usernames and alter jaas.policy accordingly. There should not be a need to alter java2.policy. Also, create a file called foo.txt in the test directory to test the last system call.
Examine Source Files
The LoginModule, HWLoginModule, simply authenticates any user who enters the correct password (case sensitive): Go JAAS.
The HelloWorld application permits users three attempts to do so. When Go JAAS is correctly entered, an HWPrincipal with a name equal the the username is added to the authenticated Subject.
The Principal class, HWPrincipal, represents a Principal based on the username entered. It is this name that is important when granting permissions to authenticated Subjects.
The main application, HelloWorld, first creates a LoginContext based on a configuration entry with the name helloWorld. The configuration file has already been discussed. Callbacks are used to retrieve user input. Look at the MyCallbackHandler class located in the HelloWorld.java file to see this process.
    LoginContext lc = null;
    try {
        lc = new LoginContext("helloWorld", new MyCallbackHandler());
    } catch (LoginException le) {
        le.printStackTrace();
        System.exit(-1);
    }
The user enters a username/password (up to three times) and if Go JAAS is entered as the password, then the Subject is authenticated (HWLoginModule adds a HWPrincipal to the Subject).
As mentioned previously, work is then performed as the authenticated Subject.
Run HelloWorld Test
To run the HelloWorld program, first change to the test directory. The configuration and policy files will need to be loaded. See Implementation for the correct properties to set either in java.security or on the command line. The latter method will be discussed here.
The following command has been broken up into several lines for clarity. Enter as one continuous command.
java -Djava.security.manager=
     -Djava.security.auth.login.config=.\jaas.config
     -Djava.security.policy=.\java2.policy
     -Djava.security.auth.policy=.\jaas.policy
     HelloWorld
Note: the use of ".\filename" for the policy files is necessary because each user's test directory canonical path will vary. If desired, substitute "." with the path to the test directory. For example, if the test directory is "c:\test\hello", then the first file would be changed to:
     -Djava.security.auth.login.config=c:\test\hello\jaas.config
If the policy files are not found, a SecurityException will be thrown. Otherwise, information concerning your java.home and user.home properties will be displayed. Also, the existence of a file called foo.txt in your test directory will be checked. Finally, the ubiquitous "Hello World" message is displayed.
Having Fun With HelloWorld
Rerun HelloWorld as many times as you like. It has already been suggested to vary the username/passwords entered, change the configuration file entries, change the policy file permissions, and to even add (stack) additional LoginModules to the helloWorld configuration entry. You could add codebase fields to the policy files too.
Finally, try running the program without a SecurityManager to see how it works if you run into problems.

Appendix A: JAAS Settings in the java.security Security Properties File
Below is a copy of the java.security file that appears in every Java 2 installation. This file appears in the lib/security (lib\security on Windows) directory of the Java 2 runtime. Thus, if the Java 2 runtime is installed in a directory called jdk1.3, the file would be

jdk1.3/lib/security/java.security (Unix)

jdk1.3\lib\security\java.security (Windows)

JAAS adds four new properties to java.security:

Authentication Properties

login.configuration.provider

login.policy.url.n

Authorization Properties

auth.policy.provider

auth.policy.url.n

The new JAAS properties are located at the end of this file:
#
# This is the "master security properties file".
#
# In this file, various security properties are set for use by
# java.security classes. This is where users can statically register
# Cryptography Package Providers ("providers" for short). The term
# "provider" refers to a package or set of packages that supply a
# concrete implementation of a subset of the cryptography aspects of
# the Java Security API. A provider may, for example, implement one or
# more digital signature algorithms or message digest algorithms.
#
# Each provider must implement a subclass of the Provider class.
# To register a provider in this master security properties file,
# specify the Provider subclass name and priority in the format
#
#    security.provider.n=className
#
# This declares a provider, and specifies its preference
# order n. The preference order is the order in which providers are
# searched for requested algorithms (when no specific provider is
# requested). The order is 1-based; 1 is the most preferred, followed
# by 2, and so on.
#
# className must specify the subclass of the Provider class whose
# constructor sets the values of various properties that are required
# for the Java Security API to look up the algorithms or other
# facilities implemented by the provider.
#
# There must be at least one provider specification in java.security.
# There is a default provider that comes standard with the JDK. It
# is called the "SUN" provider, and its Provider subclass
# named Sun appears in the sun.security.provider package. Thus, the
# "SUN" provider is registered via the following:
#
#    security.provider.1=sun.security.provider.Sun
#
# (The number 1 is used for the default provider.)
#
# Note: Statically registered Provider subclasses are instantiated
# when the system is initialized. Providers can be dynamically
# registered instead by calls to either the addProvider or
# insertProviderAt method in the Security class.

#
# List of providers and their preference orders (see above):
#
security.provider.1=sun.security.provider.Sun

#
# Class to instantiate as the system Policy. Name of the class
# that will be used as the Policy object.
#
policy.provider=sun.security.provider.PolicyFile

# The default is to have a single system-wide policy file,
# and a policy file in the user's home directory.
policy.url.1=file:${java.home}/lib/security/java.policy"
policy.url.2=file:${user.home}/.java.policy

# whether or not we expand properties in the policy file
# if this is set to false, properties (${...}) will not be expanded in policy
# files.
policy.expandProperties=true

# whether or not we allow an extra policy to be passed on the command line
# with -Djava.security.policy=somefile. Comment out this line to disable
# this feature.
policy.allowSystemProperty=true

# whether or not we look into the IdentityScope for trusted Identities
# when encountering a 1.1 signed JAR file. If the identity is found
# and is trusted, we grant it AllPermission.
policy.ignoreIdentityScope=false

#
# Default keystore type.
#
keystore.type=jks

#
# Class to instantiate as the system scope:
#
system.scope=sun.security.provider.IdentityDatabase

##############################################################################
#
# Java Authentication and Authorization Service (JAAS)
# properties and policy files:
#

# Class to instantiate as the system Configuration for authentication.
# Name of the class that will be used as the Authentication
# Configuration object.
#
login.configuration.provider=com.ibm.security.auth.login.ConfigFile

# The default is to have a system-wide login configuration file found in
# the user's home directory.  For multiple files, the format is similar to
# that of CodeSource-base policy files above, that is policy.url.n
login.config.url.1=file:${user.home}/.java.login.config

# Class to instantiate as the system Principal-based Authorization Policy.
# Name of the class that will be used as the Authorization
# Policy object.
#
auth.policy.provider=com.ibm.security.auth.PolicyFile

# The default is to have a system-wide Principal-based policy file found in
# the user's home directory.  For multiple files, the format is similar to
# that of CodeSource-base policy files above, that is policy.url.n and
# auth.policy.url.n
auth.policy.url.1=file:${user.home}/.java.auth.policy
Appendix B: Login Configuration Files
A login configuration file contains one or more LoginContext application names which have the following form:
Application {
    LoginModule Flag ModuleOptions;
    < more LoginModule entries >
    LoginModule Flag ModuleOptions;
};
Login configuration files are located using the login.config.url.n security property found in the java.security file. For more information about this property and the location of the java.security file, see Appendix A.
The Flag value controls the overall behavior as authentication proceeds down the stack. The following represents a description of the valid values for Flag and their respective semantics:

Required

The LoginModule is required to succeed.
If it succeeds or fails, authentication still continues to proceed down the LoginModule list.
Requisite

The LoginModule is required to succeed.
If it succeeds, authentication continues down the LoginModule list.
If it fails, control immediately returns to the application (authentication does not proceed down the LoginModule list).
Sufficient

The LoginModule is not required to succeed.
If it does succeed, control immediately returns to the application (authentication does not proceed down the LoginModule list).
If it fails, authentication continues down the LoginModule list.
Optional

The LoginModule is not required to succeed.
If it succeeds or fails, authentication still continues to proceed down the LoginModule list.
The overall authentication succeeds only if all Required and Requisite LoginModules succeed. If a SufficientLoginModule is configured and succeeds, then only the Required and Requisite LoginModules prior to that Sufficient LoginModule need to have succeeded for the overall authentication to succeed. If no Required or Requisite LoginModules are configured for an application, then at least one Sufficient or OptionalLoginModule must succeed.
Sample Configuration File:
/*  Sample Configuration File  */

Login1 {
   com.ibm.security.auth.module.SampleLoginModule required debug=true;
};

Login2 {
   com.ibm.security.auth.module.SampleLoginModule required;
   com.ibm.security.auth.module.JAASLoginModule sufficient;
   ibm.loginModules.SmartCard requisite debug=true;
   ibm.loginModules.Kerberos optional debug=true;
};
Note: the Flags are not case sensitive. REQUISITE = requisite = Requisite.
Login1 only has one LoginModule which is an instance of the class com.ibm.security.auth.module.SampleLoginModule. Therfore, a LoginContext associated with Login1 will have a successful authentication if and only if its lone module successfully authenticates. The Required flag is trivial in this example; flag values have a relevant effect on authentication when two or more modules are present.
Login2 is easier to explain with a table.

Login2 Authentication Status

SampleLoginModule required pass pass pass pass fail fail fail fail

JAASLoginModule sufficient pass fail fail fail pass fail fail fail

SmartCard requisite * pass pass fail * pass pass fail

Kerberos optional * pass fail * * pass fail *

Overall Authentication pass pass pass fail fail fail fail fail

* = trivial value due to control returning to the application because a previous REQUISITE module failed or a previous SUFFICIENT module succeeded.

Appendix C: Authorization Policy File
In case there weren't enough examples of Principal-based JAAS Policy grant blocks above, here are some more (Unix format).
// SAMPLE JAAS POLICY FILE:  java.auth.policy

// The following permissions are granted to Principal 'Pooh' and all codesource:

grant Principal com.ibm.security.Principal "Pooh" {
   permission javax.security.auth.AuthPermission "setPolicy";
   permission java.util.PropertyPermission "java.home", "read";
   permission java.util.PropertyPermission "user.home", "read";
   permission java.io.FilePermission "/usr/foo/jaas.txt", "read";
};

// The following permissions are granted to Principal 'Pooh' AND 'Eyeore'
// and CodeSource signedBy "DrSecure":

grant signedBy "DrSecure"
      Principal com.ibm.security.Principal "Pooh",
      Principal com.ibm.security.Principal "Eyeore" {
   permission javax.security.auth.AuthPermission "modifyPublicCredentials";
   permission javax.security.auth.AuthPermission "modifyPrivateCredentials";
   permission java.net.SocketPermission "us.ibm.com", "connect,accept,resolve";
   permission java.net.SocketPermission "griffin.ibm.com", "accept";
};

// The following permissions are granted to Principal 'Pooh' AND 'Eyeore' AND
// 'Piglet' and CodeSource from the /usr/jaas directory signed by "kent" and "bruce':

grant codeBase "file:/usr/jaas/*",
      signedBy "kent, bruce",
      Principal com.ibm.security.Principal "Pooh",
      Principal com.ibm.security.Principal "Eyeore",
          Principal com.ibm.security.Principal "Piglet"  {
   permission javax.security.auth.AuthPermission "getSubject";
   permission java.security.SecurityPermission "printIdentity";
   permission java.net.SocketPermission "guapo.ibm.com", "accept";
};
Appendix D: ThreadSubject

Applicable Platforms:
NT, Windows 2000, Windows 2000 64 Bit, and OS/390.
Description of Functionality:
This is an extension to the normal Subject.doAs. ThreadSubject.doAs basically replaces the current underlying OS's thread userid with the one in the passed in subject. This allows OS security checking to be done using the subject userid versus a possible different userid that is associated with the thread.
The methods used to invoke ThreadSubject.doAs are the same as the ones for Subject.doAs:
    public static Object doAs(final Subject subject,
                         final java.security.PrivilegedAction action);

    public static Object doAs(final Subject subject,
                         final java.security.PrivilegedExceptionAction action)
                         throws java.security.PrivilegedActionException;

    public static Object doAsPrivileged(final Subject subject,
                         final java.security.PrivilegedAction action,
                         final java.security.AccessControlContext acc);

    public static Object doAsPrivileged(final Subject subject,
                         final java.security.PrivilegedExceptionAction action,
                         final java.security.AccessControlContext acc)
                         throws java.security.PrivilegedActionException;
The above methods are utilized in the same manner as Subject.doAs.

Platform Specifics:
NT, Windows 2000, Windows 2000 64 Bit: A logged-on system administrator is allowed to authenticate other users when using an ActiveLogon LoginModule, i.e. NTActiveLoginModule or Win64ActiveLoginModule. Then the administrator may impersonate the authenticated user by applying their Subject to a system thread (using the ThreadSubject.doAs and ThreadSubject.doAsPrivileged methods listed above).
When using ThreadSubject methods, please note that the security policy will need to include AuthPermission("threadSubjectDoAs") or AuthPermission("threadSubjectDoAsPrivilege") entries as well as their cousins AuthPermission("doAs") or AuthPermission("doAsPrivileged") from the Subject class. OS/390: This version of ThreadSubject does things a little different. The way the current userid is associated with a thread makes it impossible to change it. Therefore, the code actually creates a separate thread and then associates the subject's userid with that thread and than executes the action. After the action is done executing, the thread ends. There is also some SAF (RACF) setup that must be before this function will work properly. This code makes use of the pthread_security_np service call. This call requires that main thread's userid have the necessary authority to be able to act as a surrogate for other users. Your local SAF (RACF) administrator should be able to enable this environment. The necessary information to set up this environment can be found in OS/390 V2R9.0 UNIX System Services Planning document number SC28-1890-09 in the section called "Defining Servers to Use Thread-Level Security" and in OS/390 V2R8.0 Security Server (RACF) Security Administrator's Guide document number SC28-1915-06 in the section titled "OS/390 Unix Application Considerations".

Appendix E: SAFPermission for OS/390
This class allows a program to do SAF (RACF) like security checking. A SAFPermission contains a SecurityClass, an entityName and an access. Basically, you supply these three values using one of the following constructors and the values are used by SAF (RACF) to determine if the user has the necessary access. The following are the constructors for this class:
    public SAFPermission(String securityClass,
                         String entityName,
                         Integer access)

    public SAFPermission(String securityClass,
                         String entityName)
 
    public SAFPermission(String entityName,
                         Integer access)

    public SAFPermission(String entityName)
The first constructor creates a new SAFPermission with the specified securityClass, entityName, and access.
The second one creates a new SAFPermission with the specified securityClass, entityName and an implied access of SAFPermission.__READ_RESOURCE.
The third constructor uses the specified entityName and access, as well as an implied securityClass of JAVA to create a new SAFPermission object.
The last one creates a new object of class SAFPermission with an implied securityClass of JAVA, a entityName as specified and an implied access of SAFPermission.__READ_RESOURCE.
The securityClass parameter is the security class to check with, the entityName parameter is the entity for which the check is to be done. These parameters can have any valid SAF (RACF) value.
The access parameter is the required access and must be one of the following:
    SAFPermission.__READ_RESOURCE

    SAFPermission.__UPDATE_RESOURCE

    SAFPermission.__CONTROL_RESOURCE

    SAFPermission.__ALTER_RESOURCE
A sample of using the above can be found in the OS/390 Samples or below:
    java.lang.SecurityManager sm = System.getSecurityManager();
    sm.checkPermission( new SAFPermission("FACILITY",
                                          "BPX.SERVER",
                                          SAFPermission.__UPDATE_RESOURCE ));
The code above creates a new SAFPermission and then uses the current SecurityManager to determine if the current subject has that permission. This will return an AccessControlException if the subject does not have the required access.

Policy Requirements for SAFPermission:
This class requires some entries in the java.policy file.
The first addition allows all code source to be able to ask checkPermission questions of a SAFPermission:
grant codeBase "file:/-" {
   permission com.ibm.security.auth.SAFPermission "*", "*";
};
The above could be changed to limit the codeBases that have ability to use SAFPermission by changing "file:/-" to the needed codebase or directory.
The following permissions need to be added to each grant block as well:
permission java.lang.RuntimePermission "loadLibrary.SecurityServices";
permission java.io.FilePermission ":${java.home}/lib/ext/-", "read";
permission java.util.PropertyPermission "java.execsuffix", "read";
The above are required for lower level function calls that SAFPermission makes.
A sample of a policy file that contains the above can also be found in OS/390 Samples.

Appendix F: OS/390 LoginModule

Name of the LoginModule :
The OS390LoginModule is in package com.ibm.security.auth.module.
Notes about LoginModule :
There are two types of logins that are allowed with this LoginModule: passive and active login.
If no CallbackHandler was specified on the creation of the LoginContext that is utilizing the OS390LoginModule, then the underlying operating system is queried for the current identity which is used to create a Subject. This is a passive login.
However, if a CallbackHandler was specified, then this OS390LoginModule drives a NameCallback and a PasswordCallback to get user information which in turn is used in a SAF (RACF) call to verify the userid and password. After the userid and password are verified, a Subject is created with this information. This is an active login. The Callback classes are part of the javax.security.auth.callback package.
Also, the OS390LoginModule ignores the sharedState parameter. The JAAS HelloWorld example code can be modified to use this LoginModule by using the helloOS390.config file instead of using the hello.config file. Look at OS/390 Samples for this configuraiton file.

Change record

June 21, 2000
Beta version with references to new, universal Principal classes.

October 13, 2000
Added Appendix D: ThreadSubject.
Added Appendix E: SAFPermission for OS/390.
Added ApPendix F: OS/390 LoginModule.

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Login2 Authentication Status
SampleLoginModule	required	pass	pass	pass	pass	fail	fail	fail	fail
JAASLoginModule	sufficient	pass	fail	fail	fail	pass	fail	fail	fail
SmartCard	requisite	*	pass	pass	fail	*	pass	pass	fail
Kerberos	optional	*	pass	fail	*	*	pass	fail	*
Overall Authentication		pass	pass	pass	fail	fail	fail	fail	fail