Extending SecurityManager

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Domagoj Klepac - 15 Nov 2005 07:50 GMT

I'm using my own SecurityManager in my Java application because of two
reasons:
- RMI requires the SecurityManager to be installed
- my application accepts telnet-like connections from remote users,
and I want to maintain a "whitelist" of the IPs from which users can
connect to the application

I'm currently overriding the checkAccept method to implement the
whitelist. However, I've found out that I also need to override the
checkPermission method, and basically allow everything in order to get
my application to be able to do anything.

I know that the best security is implemented by disallowing everything
and then allowing only the things that are used, but when I checked
what calls checkPermission I got a ton of output; it's impossible to
examine and allow all those things one-by-one.

But if I allow everything, I'm wondering if I'm allowing anything I
shouldn't.

So my question is basically what is allowed if there's no security
manager installed - everything? What do I do when I want to use
default security, and restrict only one part of the system (incoming
connections)?

Domchi

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Richard Wheeldon - 15 Nov 2005 22:43 GMT

> I know that the best security is implemented by disallowing everything
> and then allowing only the things that are used, but when I checked
> what calls checkPermission I got a ton of output; it's impossible to
> examine and allow all those things one-by-one.

Don't. Just do what I did with my app. Run it, wait for it to moan
about a lack of permission, fix it, repeat. This took me about 20-30
goes to get right on a 30000-40000 line app. ymmv.

You might well be suprised how useful an exercise it is for uncovering
things that shouldn't be there in the first place.

> So my question is basically what is allowed if there's no security
> manager installed - everything?

Yes.

> What do I do when I want to use default security, and restrict
> only one part of the system (incoming connections)?

Try two codebases. e.g. two packages com.foo.stuffitrust and
com.foo.stuffidonttrust

grant codebase com.foo.stuffitrust {
java.security.AllPermission;
}
grant codebase com.foo.stuffidonttrust {
java.net.SocketPermission "localhost:8888", "accept,resolve";
}

Or something similar. There's probably some syntax errors in the
above, but you should get the idea,

Richard

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Domagoj Klepac - 16 Nov 2005 18:14 GMT

>> I know that the best security is implemented by disallowing everything
>> and then allowing only the things that are used, but when I checked
[quoted text clipped - 4 lines]
>about a lack of permission, fix it, repeat. This took me about 20-30
>goes to get right on a 30000-40000 line app. ymmv.

There is a way do it without restarting. Install your security
manager, and override checkPermission:

public void checkPermission(Permission perm) throws SecurityException
{
System.out.println("Requested permission: " perm.getName());
}

Then run the app, scroll through the output and make a list. :)

>> So my question is basically what is allowed if there's no security
>> manager installed - everything?
>
>Yes.

Excellent, that's what I needed to know.

Thanks for your help.

Domchi

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Domagoj Klepac - 16 Nov 2005 18:16 GMT

>public void checkPermission(Permission perm) throws SecurityException
>{
> System.out.println("Requested permission: " perm.getName());
>}

This line should be:

System.out.println("Requested permission: " + perm.getName());

Domchi

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Extending SecurityManager

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