Authorization layer API and low level access checks.

[Peter Firmstone]

Summary of Proposed Changes:

 1. GuardFactory & GuardFactorySpi to provide hooks for authorization
    checks without SecurityManager or Policy. (Note GuardFactory should
    never return null and instead return a no-op Guard that hotspot can
    optimize out.
 2. Existing Permission implementations to be obtained using
    GuardFactorySpi implementations, until their removal.  Note that
    when SecurityManager is stubbed out and Permission implementations
    are deprecated for removal, these should no longer be provided by
    default, but instead need to be enabled by entries in the
    java.security config file, in preparation for their removal.
 3. JDK code, no longer call Permission implementations directly,
    instances obtained using GuardFactory, only when enabled in the
    java.security configuration file.
 4. Threads (system and virtual) updated to use a singleton
    *unprivileged* AccessControlContext, instead of inherited
    AccessControlContext, this is more appropriate for Executors, the
    original inherited context was designed before Executors were
    introduced.
 5. Deprecation for removal of all Permission implementations from the
    JDK platform.   The existing implementations of Permission introduce
    unnecessary complexity; they lack sufficient flexibility resulting
    in a proliferation of Permission grants required in policy files and
    some make blocking network calls.
 6. Introduce a system property to change AccessController default
    behaviour, disable the stack walk by default, but allow it to be
    re-enabled with a system property, replace the stack walk array
    result of ProtectionDomains with an *unprivileged*
    AccessControlContext, the SubjectDomainCombiner can replace it with
    a, AccessControlContext containing a single element array,
    containing one ProtectionDomain with Principals.
 7. AccessController::doPrivileged erases the DomainCombiner by default,
    deprecate these methods, retain doPrivilegedWithCombiner methods
    that preserve the SubjectDomainCombiner.   Developers should replace
    their doPrivileged methods with doPrivilegedWithCombiner
 8. Deprecate for removal the CodeSource::implies method.
 9. Give unique ProtectionDomain's with a meaninful CodeSource to Java
    modules mapped to the boot loader, rather than using a Shared
    ProtectionDomain with a null CodeSource.

To clarify what an *unprivileged* AccessControlContext is:

    An instance of AccessControlContext, that contains a single element
    array, containing a ProtectionDomain, with a non null CodeSource,
    containing a null URL.

Retention of AccessController, AccessControlContext, DomainCombiner and 
SubjectDomainCombiner and Subject::doAs methods.

Stubbing of SecurityManager and Policy, for runtime backward 
compatibility. Update ProtectionDomain::implies method, to *not* consult 
with the Policy.  Note it's possible to get access to the 
ProtectionDomain array contained within AccessControlContext using a 
DomainCombiner.

This is backward compatible with existing usages of JAAS and least 
painful method of transition for all concerned as well as allowing 
complete flexibility of implementation.

Regards,

Peter Firmstone.

On 25/06/2021 3:59 pm, Peter Firmstone wrote:
> Thanks Dalibor,
>
> Would targeting Java 18 be practical?
>
> Also it won't take long to code a prototype, just not sure of the 
> process.
>
> Cheers,
>
> Peter.
>
>
> On 24/06/2021 9:30 pm, Dalibor Topic wrote:
>> On 24.06.2021 04:24, Peter Firmstone wrote:
>>> Thanks Andrew,
>>>
>>> For the simple case, of replacing the SecurityManager stack walk, 
>>> one could use reflection.
>>>
>>> Thank you for also confirming that is not possible (or at least very 
>>> unlikely) to add a GuardBuilder to Java 8, the proposal is for JDK 
>>> code to use a provider mechanism, to intercept permission checks, so 
>>> custom authentication layers can be implemented, this could be 
>>> accepted in future versions of Java, but not existing. As it is 
>>> said, there is no harm in asking.
>>
>> Generally speaking, adding any public APIs to a platform release 
>> after its specification has been published, is always going to be a 
>> very tall order involving the JCP, among other things. It's not 
>> really worth it, when other technical solutions, such as 
>> multi-release JARs, already exist, that alleviate the necessity.
>>
>> cheers,
>> dalibor topic
>>
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