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Java security: How to install the security manager and customize your security policy
Learn about the security manager and the Java API, what remains unprotected by the security manager, and security beyond the JVM architecture
Page 6 of 7
Authentication
The support for authentication introduced in Java 1.1 in the java.security package expands your ability to establish multiple security policies by enabling you to implement a sandbox that varies depending
on who actually created the code. Authentication allows you to verify that a set of class files was blessed as trustworthy
by some vendor, and that the class files were not altered en route to your virtual machine. Thus, to the extent you trust
the vendor, you can ease the restrictions placed on the code by the sandbox. You can establish different security policies
for code that comes from different vendors.
For links to more information about authentication and java.security, see the Resources at the bottom of this article.
Security beyond the architecture
To be effective, a computer or network security strategy must be comprehensive. It cannot consist exclusively of a sandbox for running downloaded Java code. For instance, it may not matter much that the Java applets you download from the Internet and run on your computer can't read the word processing file of your top-secret business plan if you:
- Routinely download untrusted native executables from the Internet and run them
- Throw away extra printed copies of your business plan without shredding them
- Leave your doors unlocked when you're gone
- Hire someone to help you who is actually a spy for your arch-rival
In the context of a comprehensive security strategy, however, Java's security model can play a useful role.
Security is a tradeoff between cost and risk: The lower the risk of a security breach, the higher the cost of security. The costs associated with any computer or network security strategy must be weighed against the costs that would be associated with the theft or destruction of the information or computing resources being protected. The nature of a computer or network security strategy should be shaped by the value of the assets being protected.
The nice thing about Java's security model is that once you set it up, it does most of the work for you. You don't have to worry about whether a particular program is trusted or not -- the Java runtime will determine that for you. If the program is untrusted, the Java runtime will protect your assets by encasing the untrusted code in a sandbox.
Java's overall security strategy
Just as users of Java software must have a comprehensive security policy appropriate to their requirements, the security strategy of Java technology itself does not rely exclusively on the architectural security mechanisms described in this section. For example, one aspect of Java's security strategy is that anyone can sign a license agreement and get a copy of the source code of Sun's Java Platform implementation. Instead of keeping the internal implementation of Java's security architecture a secret "black box," it is open to anyone who wishes to look at it. This encourages security experts seeking a good technical challenge to seek out security holes in the implementation. When security holes are discovered, they can be patched. Thus, the openness of Java's internal implementation is part of Java's overall security strategy.
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More from JavaWorld
Resources
- The book The Java virtual machine Specification (http://www.aw.com/cp/lindholm-yellin.html), by Tim Lindholm and Frank Yellin (ISBN 0-201-63452-X), part of The Java Series (http://www.aw.com/cp/javaseries.html), from Addison-Wesley, is the definitive Java virtual machine reference.
- Secure Computing with JavaNow and the Future (a whitepaper) http://www.javasoft.com/marketing/collateral/security.html
- Applet Security FAQ http://www.javasoft.com/sfaq/
- Low Level Security in Java, by Frank Yellin http://www.javasoft.com/sfaq/verifier.html
- The Java Security Home Page http://www.javasoft.com/security/
- See the Hostile Applets Home Page http://www.math.gatech.edu/~mladue/HostileApplets.html
- For more information about authentication in JDK 1.1, see http://www.javasoft.com/products/jdk/1.1/docs/guide/security/index.html.
- A whitepaper that describes the various aspects of Java's overall security strategy is http://www.javasoft.com/security/whitepaper.html.
- The book Java SecurityHostile Applets, Holes, and Antidotes, by Dr. Gary McGraw and Ed Felton, gives a thorough analysis of security issues surrounding Java. http://www.rstcorp.com/java-security.html
- Previous "Under The Hood" articles
- The Lean, Mean Virtual Machine -- Gives an introduction to the Java virtual machine.
- The Java Class File Lifestyle -- Gives an overview of the Java class file, the file format into which all Java programs are compiled.
- Java's Garbage- Collected Heap -- Gives an overview of garbage collection in general and the garbage-collected heap of the Java virtual machine in particular.
- Bytecode Basics -- Introduces the bytecodes of the Java virtual machine, and discusses primitive types, conversion operations, and stack operations in particular.
- Floating Point Arithmetic -- Describes the Java virtual machine's floating-point support and the bytecodes that perform floating point operations.
- Logic and Arithmetic -- Describes the Java virtual machine's support for logical and integer arithmetic, and the related bytecodes.
- Objects and Arrays -- Describes how the Java virtual machine deals with objects and arrays, and discusses the relevant bytecodes.
- Exceptions -- Describes how the Java virtual machine deals with exceptions, and discusses the relevant bytecodes.
- Try-Finally -- Describes how the Java virtual machine implements try-finally clauses, and discusses the relevant bytecodes.
- Control Flow -- Describes how the Java virtual machine implements control flow and discusses the relevant bytecodes.
- The Architecture of Aglets -- Describes the inner workings of aglets, IBM's autonomous Java-based software agent technology.
- The Point of Aglets -- Analyzes the real-world utility of mobile agents such as aglets, IBM's autonomous Java- based software agent technology.
- Method Invocation and Return -- Describes the four ways the Java virtual machine invokes methods, including the relevant bytecodes.
- Thread Synchronization -- Shows how thread synchronization works in the Java virtual machine. Discusses the bytecodes for entering and exiting monitors.
- Java's Security Architecture -- Gives an overview of the security model built into the JVM and looks at the JVM's built-in safety features.
- Security and Class Loaders -- Shows how the JVM's class loader architecture contributes to Java's overall security strategy.
- Security and the Class Verifier -- Explains how the class verifier fits into the JVM's security architecture.
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