Difference between revisions of "MQP:Java Security"

Revision as of 20:59, 25 August 2008

Overview

Java, since 1.2, has some interesting security features related to access control. There are many security features dealing with Java's class loaders, assuring that the code is from a trusted source, and certificate/key management that will not be discussed here. These features are important to Java's overall security design, but are not important to the scope of this project.

This article focuses on the design and usage of Java's ability to provide fine-grained access control to features such as file access, socket communication, program configuration, and security configuration.

Security Architecture Overview

Most of Java's security classes reside in the java.security package. For the purposes of this section, if no package is noted, java.security can be assumed.

Permission Classes

Permission (Abstract Class)

Defines a type of permission

PermissionCollection (Abstract Class)

Contains a number of related Permission objects

Permissions (Object Class)

Contains a number of PermissionClass objects, sorted in a map by the Class of Permissions they contain

ProtectionDomain (Object Class)

Defines a group of classes that are protected with similar permissions

Policy (Abstract Class)

Defines the security policy (all permission grants) for the running application

Contains a number of PermissionCollection objects sored in a map, keyed by their ProtectionDomain

Determines if proper permissions are available for a given Permission based on its existence in the proper ProtectionDomain

java.lang.SecurityManager (Object Class)

Provides permission resolution to the whole program (via System.getSecurityManager()) by acting as the "central point of access control"

For most permission checks, this class calls out to java.security.AccessController

SecurityManager can be subclassed and replaced, as described below

AccessController (Object Class, Singleton)

Implements access control algorithm

Also deals with "doPrivileged()"

When checkPermission() is called, this class unrolls the call stack (using native code), determines all the permissions required, then decides if the call is ok

--Diagram Here--

Guarded Object Classes

Using Java Security

Activating the SecurityManager

Applications launched normally (using the java command) do not have security enabled - System.getSecurityManager() will return null, causing all permissions to simply be granted. To turn on the default SecurityManager:

java -Djava.security.manager [Main Class]

To specify your own SecurityManager:

java -Djava.security.manager=[SecurityManager Class] [Main Class]

or, to set it at runtime, use:

SecurityManager sm = new YourSecurityManagerClass();
System.setSecurityManager(sm);

Setting Policy

To set the policy file for the JVM:

java -Djava.security.manager -Djava.security.policy=[URL to policy file]

Using "==" in place of "=" will cause the JVM to ignore other policy files. (not sure what this means...)

The Policy File

Lot more to learn about this.

There is a tool packaged with Java called policytool that "specifies, generates, edits, exports, and imports a security policies". The user guide is here

References

• An architecture overview - http://articles.techrepublic.com.com/5100-10878_11-6177275.html
• Overview of objects in the security library - http://articles.techrepublic.com.com/5100-10878_11-6178805.html?tag=rbxccnbtr1
• Detailed documentation list - http://java.sun.com/javase/6/docs/technotes/guides/security/index.html
• Details of each of Java's packaged Permission classes - http://java.sun.com/j2se/1.4.2/docs/guide/security/permissions.html

• policytool user guide - http://java.sun.com/javase/6/docs/technotes/guides/security/PolicyGuide.html
• Details about the policy file - http://java.sun.com/javase/6/docs/technotes/guides/security/PolicyFiles.html