CODEWITHSUNDEEP
java
Patriks
Patriks

Reputation: 1012

Limit access of a java class to some packages

I have a Java class which have some confidential information which I don't want to provide to any unauthorized class.

I want to access this class in some packages (classes from this packages are going to utilize confidential information), So that my secure class should be accessible in these packages.

Is there any way where I can check if caller of method is a authorized class from authorized package or not?

I know public/private/default all things (so please don't ask me to use it), but those are not useful here, because I want a class to be accessible in some packages(not one/same).

Upvotes: 5

Views: 6137

Answers (6)

Pavel Vornic
Pavel Vornic

Reputation: 35

Guideline 4-2 / EXTEND-2: Limit the accessibility of packages Containers may hide implementation code by adding to the package.access security property. This property prevents untrusted classes from other class loaders linking and using reflection on the specified package hierarchy. Care must be taken to ensure that packages cannot be accessed by untrusted contexts before this property has been set.

This example code demonstrates how to append to the package.access security property. Note that it is not thread-safe. This code should generally only appear once in a system.

private static final String PACKAGE_ACCESS_KEY = "package.access";

static {
    String packageAccess = Security.getProperty(PACKAGE_ACCESS_KEY);
    Security.setProperty(PACKAGE_ACCESS_KEY,
                         (packageAccess == null || packageAccess.trim().isEmpty()
                                 ? "" : packageAccess + ",")
                                 + "xx.example.product.implementation.");
}

Upvotes: 0

Matt
Matt

Reputation: 11805

You might be able to leverage aspectj here. It's theoretically possible to intercept the call to a given classes' methods based on the current flow scope, and have the aspect throw an exception or something. I'm no aspectj expert though, but the "cflow" pointcut qualifier would be your most likely bet. Maybe something like this

! cflow(call(* com.mycom.AllowedClient.*))

I haven't tested this kind of pointcut, but i believe it would work.

You'd probably want compile time weaving in this case though (as opposed to load time weaving).

As a side note, i agree with some of the others that i think this is the wrong approach to take. You protect data. You protected function access based on logged in user permissions. You typically don't protect function calls from other classes.

Upvotes: 0

kostja
kostja

Reputation: 61538

You can use the proxy pattern, implemented by the Proxy class in Java - it is designed exactly for your purpose.

Here is a how-to.

EDIT : AFAIK, you cannot use the regular Proxy mechanism for static methods, as the proxy and the proxied class must implement a common interface. However, there are more advanced tools, which may help you like javassist. Unfortunately I'm not familiar with it myself.

Upvotes: 0

Kent
Kent

Reputation: 195039

I feel that you are going in the wrong direction. It might be a design problem.

The security requirement is your business logic. You should implement your security policy somehow, not rely on the java language level visibility modifier or caller package names. since if you give your jar to someone, he can anyway get access to your "confidencial" class.

And moreover, a class is a type, something abstract. it should not contain "data". well sure sometimes conf information was written as static variable etc. However if some data is sensitive, it should not be written in class. It could be stored in database or encrypted file and so on. Once a request to the sensitive information comes, you check your implemented security policy, if it is allowed to access those data.

just my 2cents

Upvotes: 5

JB Nizet
JB Nizet

Reputation: 691655

The visibility modifiers in Java are not a security tool, but an OO design tool. Whatever you might do, if someone uses your class, it can access any private members of any class using reflection.

If your objects contain confidential information, leave these objects in your secure server.

Upvotes: 2

SJuan76
SJuan76

Reputation: 24780

You can create an Exception (no need for it to be thrown) and use the getStackTrace() to analize the call stack. I always found it ugly, though.

That said, anything that you put in a client machine is vulnerable to that machine; if you have something really confidential protect it in your server; make it available only as a service.

Upvotes: 1

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