I'm sort of stewing some ideas how to locally lock down sections of a program so that a restricted section isn't able to see or modify things it hasn't already been given access to. An idea is to start using B::Util to look for specifically disallowed constructions like unpack "p", pack 'p', "foo". One of the immediate problems is how do the same auditing for BEGIN blocks in the about-to-be-called code. AFAIK there's no way to run this sort of code on a BEGIN block to audit it. Ideas?

This spot of code (blatantly unfinished with all sorts of holes) checks pack's first argument for 'P' or 'p' if the argument is a constant. This could be beefed up but not just now.

BEGIN {
  use B::Utils qw(opgrep walkallops_filtered);
  walkallops_filtered (
    # Search for pack() with a constant first arg
    sub { opgrep( { name => 'pack',
                    first => { name => 'const' }
                  }
                )
        },
    sub { my $pack = shift;
          my $const = $pack->first;

          # Disallow p and P
          if ($const->pv =~ m/p/i)
            {
              die "Format p or P was used in pack"
            }
        }
    
  );
}

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Fun Fun Fun in the Fluffy Chair

In reply to Auditing BEGIN blocks? by diotalevi

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