Improve StringEncryptTransformer

[jonesdevelopment]

• Improves the encryption and decryption method
  • Optional: Instead of passing the encrypted string to the decryption method, pass a character array

TODO:

• Pool strings in an array (initialized in a generated method called in <clinit>)
• Encrypt InvokeDynamicInsnNode bsm strings

[jonesdevelopment]

In order to keep the changes only to the string encryption, I've copied the old encryption function and method generator to InvokeDynamicTransformer.

I have tested this with my Minecraft plugin, and it worked fine. More extensive testing is recommended.

[jonesdevelopment]

@SpartanB312 I need some help with replacing invoke dynamic bsm arguments (strings) with a local variable representation (or something else). This way, we can obfuscate invoke dynamic bsms as well as ldcs.

[SpartanB312]

Bsm args are actually const pool index, which can't be replaced by localvar or field.

[SpartanB312]

You can refer to GOTO obfuscator's string encrypt transformer. It has a method for handling invoice dynamics

[SpartanB312]

or replace makeConcatWithConstants with StringBuilder (This is what the compiler did before Java8)

[jonesdevelopment]

You can refer to GOTO obfuscator's string encrypt transformer. It has a method for handling invoice dynamics

I've implemented parts of their system into Grunt's code and it seems to be working. I'm still going to do some more testing.

[jonesdevelopment]

@SpartanB312 Let me know if this is production ready. I've tested it several times and it works fine.

I'm going to recode the number obfuscation later and make it use a pool too.

[jonesdevelopment]

@SpartanB312 Can you make sure this also works in your environment? I'd like to merge this PR.

[SpartanB312]

Let me test more samples later