RFR: 8013527: calling MethodHandles.lookup on itself leads to errors [v2]

[Johannes Kuhn]

On Wed, 3 Feb 2021 18:34:55 GMT, Mandy Chung <mchung at openjdk.org> wrote:

>> You are right, got it confused with the future use.
>> 
>> With this fix, MethodHandle -> Method.invoke -> MethodHandles.lookup() will still return a lookup on the injected invoker.  
>> I somehow missed that this is not part of the fix, but for the future use.
>
> `MethodHandle -> Method.invoke -> MethodHandles.lookup() ` is a corner case that can be fixed easily using the class data approach.  See the new commit.

The security issue I mentioned was in an other branch, method-invoke.  

I used commit https://github.com/mlchung/jdk/commit/4a3c914f1b46cf84b42f6b6bc19d421955faac3f (i.e. before strengthening the injected invoker checks) to test the [my exploit](https://gist.github.com/DasBrain/4dda6cc3a13e1636afe17e6a02ec3d12). (Yes, full sandbox escape.)

I hope the same is not possible with the nestmate requirement.  

PS.: Hidden Class -> MethodHandle -> Method.invoke -> MethodHandles might break due to mangling of the hidden class name for the injected invoker. Will write a test.

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PR: https://git.openjdk.java.net/jdk/pull/2367