NAME

B::Deobfuscate - Extension to B::Deparse for use in de-obfuscating source code

SYNOPSIS

perl -MO=Deobfuscate,-csynthetic.yml,-y synthetic.pl

DESCRIPTION

B::Deobfuscate is a backend module for the Perl compiler that generates perl source code, based on the internal compiled structure that perl itself creates after parsing a program. It adds symbol renaming functions to the B::Deparse module. An obfuscated program is already parsed and interpreted correctly by the B::Deparse program. Unfortunately, if the obfuscation involved variable renaming then the resulting program also has obfuscated symbols.

This module takes the last step and fixes names like $z5223ed336 to be a word from a dictionary. While the name still isn't meaningful it is at least easier to distinguish and read. Here are two examples - one from B::Deparse and one from B::Deobfuscate.

Initial input

if(@z6a703c020a){(my($z5a5fa8125d,$zcc158ad3e0)=File::Temp::tempfile(
'UNLINK',1));print($z5a5fa8125d "=over 8\n\n");(print($z5a5fa8125d
@z6a703c020a)or die(((("Can't print $zcc158ad3e0: $!"))); print($z5a5fa8125d
"=back\n");(close(*$z5a5fa8125d)or die(((("Can't close ".*$za5fa8125d.": $!")
));(@z8374cc586e=$zcc158ad3e0);($z9e5935eea4=1);}

After B::Deparse:

if (@z6a703c020a) {
    (my($z5a5fa8125d, $zcc158ad3e0) = File::Temp::tempfile('UNLINK', 1));
    print($z5a5fa8125d "=over 8\n\n");
    (print($z5a5fa8125d @z6a703c020a)
        or die((((q[Can't print ] . $zcc158ad3e0) . ': ') . $!)));
    print($z5a5fa8125d "=back\n");
    (close(*$z5a5fa8125d)
        or die((((q[Can't close ] . *$za5fa8125d) . ': ' . $!)));
    (@z8374cc586e = $zcc158ad3e0);
    ($z9e5935eea4 = 1);
}

After B::Deobfuscate:

if (@parenthesises) {
    (my($scrupulousity, $postprocesser) = File::Temp::tempfile('UNLINK', 1));
    print($scrupulousity "=over 8\n\n");
    (print($scrupulousity @parenthesises)
        or die((((q[Can't print ] . $postprocesser) . ': ') . $!)));
    print($scrupulousity "=back\n");
    (close(*$scrupulousity)
        or die((((q[Can't close ] . *$postprocesser) . ': ') . $!)));
    (@interruptable = $postprocesser);
    ($propagandaist = 1);
}

You'll note that the only real difference is that instead of variable names like $z9e5935eea4 you get $propagandist.

OPTIONS

As with all compiler backend options, these must follow directly after the '-MO=Deobfuscate', separated by a comma but not any white space. All options defined in B::Deparse are supported here - see the B::Deparse documentation page to see what options are provided and how to use them.

-dDICTIONARY

Normally B::Deobfuscate reads an internal dictionary of easily pronounced keywords. If you would like to specify a different dictionary follow the -d parameter with the path to the dictionary file. The path may not have commas in it and only lines in the dictionary that do not match /\W/ will be used. The entire dictionary will be loaded into memory at once.

-d/usr/share/dict/stop

For an alternate approach, see Acme::Floral's source code and how it installs an alternate dictionary of flower names. This writes a new dictionary to the *B::Deobfuscate::DATA filehandle before the B::Deobfuscate object decompiles the input perl code.

-mREGEX

Supply a different regular expression for deciding which symbols to rename. The default value is /\A[[:lower:][:digit:]_]+\z/. Your expression must be delimited by the '/' characters and you may not use that character within the expression. That shouldn't be an issue because '/' isn't valid in a symbol name anyway.

-a/\A[[:lower:][:digit:]_]+\z/

-y

print two YAML documents to STDOUT instead of the deparsed source code. The first document is a configuration document suitable for use with the -c parameter. The second document is the deparsed source code. Use this feature to generate a configuration document for further, iterative reverse engineering.

The intention here is that you could write some software to read this YAML document, present the information to the user, accept some alterations to the configuration and re-run the deobfuscator with the new input.

-cFILENAME

Supply a filename to a YAML configuration file. Normally you would generate this file by saving the results of the -y parameter to a file. You can then edit the file to provide your own names for symbols and not rely on the random symbol picker in B::Deobfuscate. You may create your own YAML configuration file as well.

CONFIGURATION FILE

The B::Deobfuscation symbol renamer can be controlled with by a configuration file. Use of this feature requires the YAML module be installed.

dictionary: '/usr/share/dict/propernames'
global_regex: '(?:)'
globals:
  kSDsfDS: Slartibartfast
  HGFdsfds: Triantaphyllos
lexicals:
  '$SdfSd': '$No'
  '$GsdDd': '$Ed'
  '$Ksdfs': '$Ji'

dictionary

This is a filename path to the operative dictionary.

dictionary: /usr/share/dict/stop

global_regex

This regular expression tests global symbols. Only symbols that match this expression may be renamed. The default value is '\A[[:lower:][:digit:]_]\z/. In perl, global symbols are independent of their sigil so the values being tested are bare. Future versions of B::Deobfuscate may add the sigil to the symbol name.

global_regex: '\A[[:lower:][:digit:]_]\z'

globals

This is a hash detailing symbol names as used in the original source and the name used in the deobfuscated source. For example - if the original source has a variable named @z12345 and you wish to rename all occurrances to @URLList then the hash would associate 'z12345' with 'URLList'. The dictionary picker fills these values in automatically.

If you wish to prevent B::Deobfuscate from renaming a symbol then specify the new value as '~' (which in YAML terms is undef).

globals:
  catfile: ~
  opt_n: ~
  opt_t: ~
  opt_u: ~
  z1234567890: Postprocesser
  z2345678901: Constructable
  z3456789012: Photosynthesises
  z4567890123: Undiscriminate
  z5678901234: Parenthesises
  z6789012345: Animadvertion

lexicals

Lexicals is a hash exactly like `globals' except that all the symbol names include the sigil which doesn't currently happen for globals.

lexicals:
  '$k1234567890': '$ivs'
  '$k2345678901': '$ehs'
  '$k3456789012': '$ans'
  '$k4567890123': '$ons'
  '$k5678901234': '$ofs'
  '$k6789012345': '$gos'
  '$k7890123456': '$dus'
  '$k8901234567': '$iis'
  '$k9012345678': '$ats'
  '$k0123456780': '$ets'

AUTHOR

Joshua ben Jore <jjore@cpan.org>

SEE ALSO

B::Deparse http://www.perlmonks.org/index.pl?node_id=243011 http://www.perlmonks.org/index.pl?node_id=244604 YAML