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From "James Carman" <>
Subject RE: [logging] tech.xml - child-first classloading not consideredharmful
Date Wed, 04 May 2005 20:41:11 GMT
If a security manager was in place to begin with, which it would be in an
environment which you would want to secure, it probably wouldn't allow
applications to create their own classloaders anyway (the ClassLoader class'
constructor checks to see whether you have that privilege).  A reasonable
SecurityManager wouldn't allow itself to be replaced, so a "malicious" one
wouldn't be able to let an application "break out of its sandbox."  If there
isn't a SecurityManager installed, there IS no sandbox.

-----Original Message-----
From: robert burrell donkin [] 
Sent: Wednesday, May 04, 2005 4:39 PM
To: Jakarta Commons Developers List
Subject: Re: [logging] tech.xml - child-first classloading not

On Wed, 2005-05-04 at 13:03 -0700, Mike Colbert wrote:
> > in the case of a parent-first classloader, the buggy implementation 
> > would not be exposed since the call would be delegated to the system 
> > classloader. in the case of a child-first classloader, a buggy 
> > implementation may try to define SecurityManager itself and this bug 
> > exploited.
> This would mean an attacker would have to take advantage of a bug in a 
> class loader which allows them to load a malicious SecurityManager in 
> such a way that it would be shared by all applications.  I can kind of 
> see how parent-first delegation would mitigate this, but one would 
> think that with appropriate levels of class loader isolation in place 
> the delegation order becomes a non-issue.  Maybe the bug has something 
> to do with broken isolation.

i was thinking that a malicious SecurityManager implementation might allow
an application to break out of it's sandbox but i'm not an expert and this
is really just speculation on my part. i don't think that this kind of
attack is any sort of realistic threat. this would be a good time for craig
to jump in...

- robert

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