Introduction to the Java security model

As a language born of the rise of the Internet, Java from the outset with security considerations, how to ensure that the download to the local Java program on the Internet is safe, how to access the Java program permissions to local resources Limited authorization, these security considerations from the outset to affect the Java The design and implementation of language. It can be said that Java in these aspects of exploration and experience, some of the later language and products have brought a positive impact.

This article will introduce the security model in Java and how to use secure access control mechanisms to achieve some specific goals.

The security model in Java

In Java, the execution program is divided into two local and remote, and the local code is treated as trustworthy by default, while remote code is considered untrusted. For the local code of the credit, you can access all local resources. For non-credit remote code in the early Java implementation, security relies on the sandbox (Sandbox) mechanism. The sandbox mechanism is to limit the Java code to the specific operational scope of the virtual machine (JVM), and strictly restrict the code's access to the local system's resources, so as to ensure effective isolation of remote code and prevent damage to the local system. As shown in Figure 1,

Graph 1.jdk1.0 Security Model

But such stringent security mechanisms also pose obstacles to the extension of the program's functionality, such as when users want remote code to access files on the local system. As a result, improvements to the security mechanism have been made in subsequent Java1.1 releases, adding security policies that allow users to specify code access to local resources. As shown in Figure 2,

Graph 2.jdk1.1 Security Model

In the Java1.2 version, the security mechanism was again improved and code signing was added. Regardless of the local code or remote code, according to the user's security policy settings, the class loader loaded into the virtual machine in different permissions of the operating space, to achieve differentiated code execution rights control. As shown in Figure 3,

Graph 3.jdk1.2 Security Model