Integrated: 8217920: Lookup.defineClass injects a class that can access private members of any class in its own module

[Mandy Chung]

On Thu, 26 Jan 2023 21:03:59 GMT, Mandy Chung <mchung at openjdk.org> wrote:

> Currently, a `Lookup` object with `PACKAGE` access can be used to inject a class in the runtime package of the Lookup's lookup class via `Lookup::defineClass`.   The classes that are injected have the same access as other members in the module and can access private members of all types in the module via reflection.
> 
> However, changing `Lookup.defineClass` to require full privilege access (`PRIVATE` + `MODULE`) is an incompatible change that would break existing frameworks which use `privateLookupIn` and `Lookup::defineClass` to inject auxiliary classes in a module.   A module authorizes the framework by opening a package for it to access and `Lookup::defineClass` was the supported replacement for `setAccessible` on `ClassLoader::defineClass` hack in JDK 9.    
> 
> This PR proposes to keep existing behavior and provide better documentation to help developers to beware of the permissions given out when opening a package to another module. A class injected in a module has the same privilege as other module members.

This pull request has now been integrated.

Changeset: 7f05d57a
Author:    Mandy Chung <mchung at openjdk.org>
URL:       https://git.openjdk.org/jdk/commit/7f05d57a87d8b41b53194aa0dacc4057cbb58544
Stats:     31 lines in 2 files changed: 30 ins; 0 del; 1 mod

8217920: Lookup.defineClass injects a class that can access private members of any class in its own module

Reviewed-by: psandoz, alanb, darcy

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PR: https://git.openjdk.org/jdk/pull/12236