Since JAPH seems to be popping out all over

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Re: Since JAPH seems to be popping out all over
by davido (Cardinal) on Feb 06, 2005 at 05:21 UTC

You know what's interesting is the way in which B::Deparse breaks this obfu. In specific, Deparse breaks the portion that goes like this: $|[ $a++ ] = chr $;;. Deparse turns that into $|[ $a++ ] = chr $;. The important difference is the missing statement terminator, ';'. After being deparsed, until I manually add that back in, I get the following:

Scalar found where operator expected at mytest2.pl line 16, near "$;
        $;"
        (Missing operator before $;?)
syntax error at mytest2.pl line 16, near "$;
        $; "
Execution of mytest2.pl aborted due to compilation errors.
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I know the old mantra is "Only perl can parse Perl", and this is an example of that being the case. I'd say it's a bug in B::Deparse, but then we can't expect it to be perfect, especially when presented with an obfu. I'm just surprised that it got tripped up by something so trivial as a statement terminating semicolon.

Dave

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Re^2: Since JAPH seems to be popping out all over

by whio (Beadle) on Feb 06, 2005 at 07:59 UTC

B::Deparse

I suspect that something in Deparse mistakes $; as including the statement-terminating semicolon, particularly as it occurs on the end of a line. This is just guessing, though, as I have not really experimented with it much.

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Re: Since JAPH seems to be popping out all over
by jdalbec (Deacon) on Feb 06, 2005 at 22:29 UTC

The characters in the long ugly string are expanded to 3-digit numbers in base 5.

230 004 333 343 321 433 324 400 143 014 312 443 202 432 431 243
211 403 241 343 314 310 441 024 324 323 431 432 334 300 432 134
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These numbers are concatenated. The string is then (in effect) split at 4's since a 4 causes $; to be added to @| and then reset to 0.

230004 33334 33214 33324     4
  0014  3014  3124     4 32024
   324  3124 32114  0324   134
  3314  3104     4  1024   324
  3234   314 32334  3004 32134
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The digits in each number (omitting the final "4") are xor'd with 2

01222 1111 1103 1110    0
  223  123  130    0 1020
   10  130 1033  210   31
  113  132    0  320   10
  101   13 1011  122 1031
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and interpreted as numbers in base 4

hex values:
6a 55 53 54  0
2b 1b 1c  0 48
 4 1c 4f 24  d
17 1e  0 38  4
11  7 45 1a 4d
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which are converted back into (not necessarily printable) characters. These characters are (in effect) split into groups of 5 and each group is xor'd into $_ and the result is printed.

20 20 20 20 20 $_ = "     "
6a 55 53 54  0 @|
4a 75 73 74 20 $_ = "Just "
2b 1b 1c  0 48 @|
61 6e 6f 74 68 $_ = "anoth"
 4 1c 4f 24  d @|
65 72 20 50 65 $_ = "er Pe"
17 1e  0 38  4 @|
72 6c 20 68 61 $_ = "rl ha"
11  7 45 1a 4d @|
63 6b 65 72 2c $_ = "cker,"
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I ran the code through perl -MO=Deparse and perltidy and added some comments:

#! /usr/bin/perl
# $;=$\;$_=$"x5;$b=$|;for$%(map{$_*.04,$_/5=>$_}map{ord}split??,
# "A\4]bVvYd0\tR{4utI8gGbTPy\cNYXtu^Ku,"){if($%%5&4){$|[$a++]=chr
# $;;$;=0;print$_^=join$\,@|if!($a%=5);}else{$;=($;*4+$%%5^2);}}

use strict;
# use warnings;

$; = $\;
# undef
$_ = $" x 5;
# "     "
$b = $|;
# misdirection
foreach $% ( map { $_ * 0.04, $_ / 5, $_; }
    map( { ord $_; } split ( ??, "A\cD]bVvYd0\tR{4utI8gGbTPy\cNYXtu^Ku
+,", 0 ) )
  )
# { print $%%5; } # 3-digit base 5 expansion
{
    if ( $% % 5 & 4 ) {
# terminate base-4 number
        $|[ $a++ ] = chr $;;
        $; = 0;
# after 5 characters, xor and print
        print $_ ^= join ( $\, @| ) if not $a %= 5;
    }
    else {
# interpret base-4 number after xor'ing digits w/2
        $; = $; * 4 + $% % 5 ^ 2;
    }
}
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