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From Gregg Wonderly <gr...@wonderly.org>
Subject Re: Codebase service?
Date Fri, 21 May 2010 15:41:55 GMT
My understanding/recollection of what currently happens, is that any class that 
the client already has loaded, will be used by the proxy as long as it is not 
preferred, because of the classloader hierarchy.  This means, that non-preferred 
classes that a client has in the jars of its classpath, have been assumed to be 
safe, and having them in the classpath indicates, in a sense, trust in the 
content and activities of the code in such jars.

I don't think it's a good idea to "load" classes from network downloaded jars 
into the system class loader arbitrarily.

The convenience of having a lot of these things automated is a good thing, but I 
think the default must be that network downloaded code has no permissions 
explicitly granted by placing that code into a classloader that is not 
associated with a thread of execution that is based on the downloaded codes 
SecurityContext.

Gregg Wonderly

Peter Firmstone wrote:
> Actually this might cause a problem if the proxy has been granted 
> greater priviledges than a calling thread's Principal (a user) running 
> with a lesser set of Permissions than the proxy, it causes all 
> SecurityManager checks by the proxy to throw Security Exceptions.
> 
> Does this mean restricting the PermissionDomain of the *-api.jar is the 
> wrong thing to do?
> 
> Should it be allowed DynamicPolicy grant's?
> Perhaps it should be given the same Permissions as the most privileged 
> proxy instead, using the fore mentioned ClassDep tool to verify the 
> *-api.jar files don't depend on any security sensitive classes prior to 
> loading?
> 
> When performing dynamic grants to a class, get the classes interfaces 
> and do the dyanamic grant's on them too.
> 
> What do you think?
> 
> Peter Firmstone wrote:
>> Actually on Second thoughts, this security concern is unfounded 
>> (paranoia perhaps, security is hard!), the ProtectionDomain of the 
>> *-api.jar will be on the execution stack, the actual Permissions will 
>> be those common to all ProtectionDomain's on the caller's stack, so 
>> therefore having a ProtectionDomain with no permissions assigned to a 
>> *-api.jar will cause the calling thread to have no permissions (as the 
>> proxy sees it).
>>
>> Therefore a proxy, if it is to utilise it's own permission grants, it 
>> will need to use AccessController.doPrivileged()
>>
>> That sounds better.
>>
>> Anyway there will be no Permissions granted to any *-api.jar, ever as 
>> I'm going to utilise the pre java 1.4 ProtectionDomain constructor, 
>> that specifically prevents and excludes dynamic Policy grants.  It 
>> won't even consult the Policy.
>>
>> I'm modifying DynamicPolicy to include grants by Certificate[], an 
>> *-api.jar that is signed by a trusted certificate chain, still wont 
>> gain any permissions.  Can anyone see that as a problem?
>>
>> The *-api.jar classes must not have dependencies on anything outside 
>> of the Jini Platform, Java Platform or other *-api.jar classes.  The 
>> reason for this restriction, is if Someone want's to use OSGi or has a 
>> dependency on another version of a library, the *-api.jar importing an 
>> incompatible version, would obscure it's visibility and cause a 
>> runtime error.
>>
>> These restrictions shouldn't cause a problem for people as they're 
>> easy to design around.  It makes security  simpler for developers too. 
>> - You don't have to worry about the security of the code in *-api.jar
>>
>> Cheers,
>>
>> Peter.
>>
>> Peter Firmstone wrote:
>>> Dennis Reedy wrote:
>>>>> Chris, Dennis & Greg, your all spot on with the Service-spec.jar,

>>>>> I'd like to add something to the jar Manifest of these Service 
>>>>> Interfaces, to ensure River loads it into the top level 
>>>>> ClassLoader.  Any suggestions?
>>>>>     
>>>>
>>>> Why not just support the convention instead of adding configuration?
>>>>   
>>>
>>> Ok.
>>>
>>> There is one Security Concern that I will have to address with this 
>>> Approach:
>>>
>>> ClassLoader Structure:
>>>
>>>                 System ClassLoader
>>>                         |
>>>                Extension ClassLoader (incl jsk-policy.jar)
>>>                         |
>>>                Jini Platform ClassLoader (incl jsk-platform.jar, 
>>> *-api.jar)
>>>                         |
>>>          _______________|________________
>>>         |                                |
>>> Application ClassLoader         Proxy ClassLoader's
>>>
>>>
>>> The *-api.jar files will be placed into Jini Platform ClassLoader, so 
>>> the only files visible will be the jini platform classes, java 
>>> platform classes and any other *-api.jar classes.
>>>
>>> The *-api.jar classes will have their own ProtectionDomain's without 
>>> any Permissions.
>>>
>>> However this isn't enough to protect us from code that might be 
>>> included in the *-api.jar's that use the calling Threads Permissions 
>>> to perform security violating actions.
>>>
>>> Due to these security concerns, we need to place some restrictions on 
>>> the API classes:
>>>
>>>   1. They must not be allowed to depend on anything other than Jini,
>>>      Java Platform and other Service-api.jar's
>>>   2. They must not be allowed to depend on any Platform classes that
>>>      could cause a Security Violation.
>>>
>>> The Service API code really needs to be verified before loading, to 
>>> ensure that it does not utilise any platform classes that perform 
>>> security sensitive operations.
>>>
>>> The ClassDep tool can run a Dependency Analysis on any *-api.jar to 
>>> ensure that no security sensitive classes are accessed, prior to 
>>> loading.
>>>
>>> There is some residual risk that as the Java platform evolves, new 
>>> classes that perform Security Sensitive actions will be added, which 
>>> means the list of restricted classes will need to grow over time.
>>>
>>> Could the list itself be contained in a Maven Repository, we could 
>>> sign, such a list.
>>>
>>> Thoughts?
>>>
>>> Peter.
>>>
>>>
>>>
>>>
>>>
>>>
>>
>>
> 
> 


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