Implementation

In analyzing the effectiveness of Java security, it is necessary to check if there are adequate methods of controlling each of the resources specified in Section 2.1.

• File system - Access to the file system is well protected, with specific SecurityManager checks for read and write access to a given file. This allows flexible policies such as access control lists to be fairly easily implemented.
• Network - Access to the network is well protected. There are SecurityManager checks on the methods necessary for both accepting and creating of sockets, as well as protection of calls to other network related methods. Again, these methods are flexible, allowing access controls.
• Random Memory - Protection of memory is done by the language specification itself. There is protection against access to the already allocated memory, but there is no protection against an Applet allocating all of the current memory available (by creating objects).
• Output Devices - One protection provided for output devices is that any Applet windows can be forced to have a special marking noting that they are unsafe. Additionally, an Applet cannot directly access devices, instead it must use the mechanisms provided by the Java libraries.
• Input Devices - An Applet can only access the keystrokes or mouse clicks of the user when the Applet's window has been selected. Currently other input devices are not supported, although one would assume that any access to devices such as camera's or microphones would be through a Java library which could add security checks. Currently there are no explicit security checks involving input.
• Process Control - Access to control of threads is fairly limited. There are SecurityManager checks of access the threads and threadgroups. Additionally, the maximum priority of threads can be set to make sure an Applet's thread does not dominate.
• User Environment - Access to environment variables is protected by SecurityManager checks. Additional access control to the Java language environment is provided by the languages access control mechanisms for classes.
• System Calls - The SecurityManager checks any attempted system calls, including attempts to exit.

The control of a few of these resources stand out. First, the current SecurityManager does not have a method for controlling the creation of top level windows (aside from forcing them to be marked as unsafe), or control of what can be displayed or played back audibly. Second, there is no mechanism for controlling an Applet's access to user input. There are certainly situations it would be desirable to have a more specific security policy regarding various input devices. Finally, an Applet can currently allocate an arbitrary amount of memory by creating new objects. The problem of allocating memory is difficult because it does not provide a very direct threat; there is no single operation or set of operations that can be controlled. The problem is not horrible since the browser can limit the amount of memory available to Java. The browser could also provide a method of killing the current Java Applet, causing the memory to be recovered.

• Scenarios
• Digital Signatures