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Re: How to tell if Perl has -DDEBUGGING?

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From:
Nicholas Clark
Date:
October 24, 2003 09:31
Subject:
Re: How to tell if Perl has -DDEBUGGING?
Message ID:
20031024162956.GB52109@plum.flirble.org
On Fri, Oct 24, 2003 at 05:14:55PM +0100, Steve Hay wrote:

> I was looking at the Filter::decrypt module as a means of encrypting 
> source code.  (And I don't want a flame war about the ethics or merits 
> or doing that.)

Indeed. It would be off topic for p5p. Probably even off topic for
advocacy.


> The documentation suggests statically linking the Filter::decrypt 
> extension against a non-DEBUGGING Perl.  I don't want to statically link 
> it, but I don't want people (devious miscreants or otherwise) to take 
> the dynamically linked module and slap it into their DEBUGGING Perl and 
> start hacking either.
> 
> It occurred to me that if the module knew for sure whether or not the 
> Perl in question was a DEBUGGING Perl then the dynamically linked plan 
> is a little safer.

I don't think that you can know for sure, because someone versed in the
perl source can always bugger about with their interpreter until they
find a way to convince your module that -DDEBUGGING isn't set when it
is. (And one can set -g without -DDEBUGGING if one Configures by hand).

However, you should be able to outdo everyone who has to use a precompiled
perl (er from regular sources), plus anyone who isn't knowledgeable enough
to modify the sources before compiling their own.

As with every attacker/ defender situation, you can't win. You have to keep
all the holes plugged to stay in the game. They only have to find one hole
to win. Plus they work in parallel. But hopefully beating most people is
good enough for your purposes.

Nicholas Clark

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