Handle unverifiable jumps into the middle of instructions.

[leibnitz27]

https://anthony.som.codes/blog/2019-12-30-jvm-hackery-noverify/ (
@half-cambodian-hacker-man ) points out some fun stuff allowing jumps to vector into the middle of other byte code.

[leibnitz27]

  public static int foo();
    Code:
       0: nop
       1: nop
       2: goto          6
       5: sipush        8
       8: istore        0
      10: getstatic     #14                 // Field java/lang/System.out:Ljava/io/PrintStream;
      13: iload         0
      15: invokevirtual #8                  // Method java/io/PrintStream.println:(I)V
      18: sipush        1
      21: ireturn

Now gives

/*
 * Handled unverifiable bytecode (illegal jump).
 */
public static int foo() {
    int n = 5;
    System.out.println(n);
    return 1;
}

[leibnitz27]

And here are a couple of examples.

NoVerify.class.zip
NoVerify2.class.zip

(classes renamed as zip to make github happy)

[char]

Does this work for conditional branches?

[leibnitz27]

Should do (there's nothing jump specific in here, just handling instructions whose successor isn't a legitimate index). Feel free to try to break it ;)

[leibnitz27]

(And if you do, pls provide class file ;) )