Java Security, 2nd Edition

Comparison with Previous Releases

The security manager has existed in every release of Java. In Java 1.0 and 1.1, the security manager is the only thing that affects the security policy of the program. Because there is no way to install a default security manager via the command line prior to Java 2, most Java 1.0 and 1.1 applications do not have a security manager. In addition, the implementation of the security manager between 1.1-based browsers varies in important aspects between different browser vendors. Even though some browser vendors claim to support the Java 2 platform, they still implement their own security manager rather than using the permission and policy-based default security manager.

We’ll discuss many of the major differences here. In addition, in Appendix D, we’ll show how a security manager could be implemented in order to specify a policy for applications run in 1.1.

Trusted and Untrusted Classes

The default notion of what constitutes a trusted class has changed significantly between releases of Java:

• In Java 1.0, a class that is loaded from the classpath is considered trusted and a class that is loaded from a class loader is considered untrusted.

• In Java 1.1, the same rule applies but a class that is loaded from a jar file may carry with it a digital signature that allows it to be given extra privileges. These privileges are typically all-or-nothing: if you trust the entity that signed the jar file, then that code can do anything it wants. Some browser vendors ...