SecurityManager environments

Alan Bateman Alan.Bateman at
Wed Apr 5 17:53:41 UTC 2017

On 05/04/2017 16:26, Gregg Wonderly wrote:
> :
> At the forefront of the failure of the SecurityManager to be an avidly used element of Java applications, is the simple fact that the whole infrastructure is horribly inefficient and full of locks and mutable data which should not be locked and should instead be immutable.  But, because “assume no security manager in the picture” is the state of “the world”, the details have not been fixed, officially.  In the Jini community, Peter Firmstone (most of the recent work), and I, have spent quite a bit of time on understand and fixing these issues.  He has tried to push the knowledge of what needs to be done into various places, which I don’t recall at the moment.
You are right that the performance overhead when running with a security 
manager can be a problem. Walking the stack to get the intersection of 
the permissions has historically been a big part of this. If there are 
proposals and patches to improve the performance then security-dev is 
the place to bring those for discussion, maybe hotspot-dev if it gets 
into the stack walking in the VM.

> In the end because JDK-9 breaks everything (well not quite, but nearly, since spring and other similar libraries are broken), requiring command line arguments, why not just finally fix Java by instituting a default SecurityManager, instead of the command line flags, which enforces all of these things.  Why not just require the added command line argument to be the permissions file to use?
I assume the breakage you see is just a consequence of strong 
encapsulation. There is a lot of existing code that relies on being able 
to break into non-public members or access protected members from the 
wrong context. These are issues that should be reported to the owners of 
these libraries.  We know it will be difficult in the interim before the 
maintainers release new versions that work with JDK 9.

You mention Spring. There are some very smart people working on it and 
tracking JDK 9 closely from what I can tell. Existing versions 
SpringBoot  fail today for a couple of reasons - one is that it is 
helping itself to a non-public constructor for MethodHandles.Lookup. 
Another is that it wants to invoke the protected ClassLoader.defineClass 
from the wrong context. I'm confident that they will fix this code in 
time as there new APIs to address these use cases.  In the mean-time 
then there are command line options to keep existing versions working. 
Yes, command line options are pain but for executable JAR cases like 
this then there are JAR file attributes that come some relief from CLI 

As regards the security manager then it's hard to see how it fits into 
the discussion. To be honest, we don't see a lot of security manager 
usage on the server side these days. I look at a lot of bug reports and 
error logs that include the command line and I don't see very often. If the overhead was zero and it was 
easier to identify the permissions needed by each component then maybe 
it would have got more popular. Another reason is that the access checks 
that you see in the discussions here are the access checks that the JLS 
and JVMS specifies. They are access checks that have to be done when you 
are not running with a security manager. They are also at a completely 
different level, meaning can bytecode in C1.m can access a member of C2. 
This is very different to the stack based permission checks that a 
security manager does.


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