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From Dennis Reedy <dennis.re...@gmail.com>
Subject Re: PAM - Pluggable Authentication Modules Any Ideas?
Date Thu, 13 May 2010 21:38:22 GMT

On May 13, 2010, at 531PM, Gregg Wonderly wrote:

> Dennis Reedy wrote:
>> On May 13, 2010, at 1123AM, Gregg Wonderly wrote:
>>> If you use System.load(), then you can use a static initialization
>>> block to copy the jni bits from the jar into a temp directory and then load it
from that path.  Associated permissions need to be granted of 
> >>course.
>>> 
>> Sure, you can copy the native lib to a temp directory, and assuming you 
> > have set the JVM up to load native libs from that directory that would
> > work, but you still need to address the class loader issue right?
> 
> There are no requirements for "setting up the JVM" except for permissions needed when
you use System.load() as opposed to the less flexible System.loadLibrary().  So, any code
with appropriate permissions granted can use System.load() to load a dynamic library which
will bind with JNI class definition.

FWIW, in my experience dealing with native libraries it gets very very tricky if you want
different class loaders to use the same loaded native library. So *any* code is generally
subjective based on the class loader, is not just the permissions.

> 
>> I think that you'd rather want to have the native libraries required for 
> > authentication part of your 'platform'.
> 
> As the service provider, you want the authentication to happen correctly. I don't want
to lead on that a client would be using a JNI JAAS authentication implementation locally.
 But, I wanted to point out that System.load() works fine.  I have my JAAS authentication
in a utilities jar. 

What classloader loads your utlities.jar?

> My authentication class  loads the .so from the file system, using System.load() to load
it, with no properties set in the JVM to indicate where libraries are at.  It would work just
fine to use ClassLoader.getResource() to find the library (even using the os.name or some
such property to pick the appropriate one), copy it out the the filesystem and load it from
a different, more random path.



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