Re: zlibscan : script to find suid binaries possibly affected byzlib vulnerability

[Florian Weimer <Weimer@CERT.Uni-Stuttgart.DE>]

hologram <holo@brained.org> writes:

> The following is a quick shell script to find suid binaries that are
> potentially affected by the zlib vulnability (i.e., those dynamically
> linked).

The hard case are statically linked binaries, though.  I've written a
short Perl script which scans for signatures found in compiled zlib
code.  The signatures are based on zlib's data tables, not machine
code, so they are fairly architecture-independent (modulo the 32/64
bit and endian issues addressed by the script).

-- 
Florian Weimer 	                  Weimer@CERT.Uni-Stuttgart.DE
University of Stuttgart           http://CERT.Uni-Stuttgart.DE/people/fw/
RUS-CERT                          +49-711-685-5973/fax +49-711-685-5898

#!/usr/bin/perl -w

# find-zlib - scan for zlib tables in compiled code
# Copyright (C) 2002 RUS-CERT, University of Stuttgart.
# Written by Florian Weimer <Weimer@CERT.Uni-Stuttgart.DE>.
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.

# $Id: find-zlib,v 1.8 2002/03/13 18:42:44 rusfw Exp $
# <http://CERT.Uni-Stuttgart.DE/files/fw/find-zlib>

use strict;

if (@ARGV == 0 or $ARGV[0] eq '-h') {
    print <<EOF;
find-zlib - scan for zlib tables in compiled code
Copyright (C) 2002 RUS-CERT, University of Stuttgart.

Usage: find-zlib [-v] filename...

In non-verbose mode (without the "-v" flag), find-zlib scans only for
three signatures:

  - The "cplenx table".  It is not specific to zlib, but used
    by any inflate decoder.
  - The "cplext table".  This table is specific to zlib and
    also gives some version information.
  - The "inflate" copyright string.

Even if the copyright string has been removed, the other two signatures
permit the identification of zlib inflate code.

In verbose mode, additional signatures are tested:

  - The "configuration table".  It is specific to zlib, but not
    required by the inflate code.
  - Some common messages found in zlib.
  - The "deflate" copyright string. Note that the deflate code is
    independent of the inflate code.

Thanks to Mark Adler for helpful suggestions.

Send comments to fw-tracker\@CERT.Uni-Stuttgart.DE.

EOF
    exit 1;
}

my $verbose = 0;

if ($ARGV[0] eq "-v") {
  $verbose = 1;
  shift @ARGV;
}

$/ = undef;

my @cplens_table = (3, 4, 5, 6, 7, 8, 9, 10, 11, 13, 15, 17, 19, 23, 27, 31,
		     35, 43, 51, 59, 67, 83, 99, 115, 131, 163, 195, 227,
		     258, 0, 0);
my @cplext_table_092 = (0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 2, 2, 2, 2,
			3, 3, 3, 3, 4, 4, 4, 4, 5, 5, 5, 5, 0, 128, 128);
my @cplext_table_104 = (0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 2, 2, 2, 2,
			3, 3, 3, 3, 4, 4, 4, 4, 5, 5, 5, 5, 0, 192, 192);
my @cplext_table_114 = (0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 2, 2, 2, 2,
			3, 3, 3, 3, 4, 4, 4, 4, 5, 5, 5, 5, 0, 112, 112);

sub table_to_re (@) {
    my $be = "";
    my $le = "";
    my $e;
    foreach $e (@_) {
	$be .= pack "N", $e;
	$le .= pack "V", $e;
    }
    return (quotemeta($be), quotemeta($le));
}

sub table_to_re_config (@) {
    my $be = "";
    my $le = "";
    my $e;
    foreach $e (@_) {
	$be .= pack "n", $e;
	$le .= pack "v", $e;
    }
    return (quotemeta($be), quotemeta($le));
}

sub table_to_re_combined (@) {
  my ($be, $le) = table_to_re(@_);
  return "($be|$le)";
}

my ($cplens_table_be, $cplens_table_le) = table_to_re (@cplens_table);
my ($cplext_table_092, $cplext_table_104, $cplext_table_114) =
  (table_to_re_combined(@cplext_table_092),
   table_to_re_combined(@cplext_table_104),
   table_to_re_combined(@cplext_table_114));

my $line;
my (@config_table_le, @config_table_be) = ();
foreach $line ([8,   32, 128, 256],
	       [32, 128, 258, 1024],
	       [32, 258, 258, 4096]) {
    my ($be, $le) = table_to_re_config(@$line);
    push @config_table_be, $be;
    push @config_table_le, $le;
}
my ($config_table_be_32,
    $config_table_be_64,
    $config_table_le_32,
    $config_table_le_64)
    = (join("....", @config_table_be),
       join("........", @config_table_be),
       join("....", @config_table_le),
       join("........", @config_table_le));

my $file;
my $found = 1;
for $file (@ARGV) {
  warn "$file: non-regular file ignored\n" unless -f $file;
  unless (open(FILE, "<$file")) {
    warn("$file: cannot read file\n"); 
    next;
  }
  my $data = <FILE>;
  close FILE;

  if ($data =~/inflate ([0-9][ 0-9a-zA-Z.\-]{1,100}[0-9a-zA-Z.\-])/) {
    print "$file: inflate version: \"$1\"\n";
    $found = 0;
  }
  if ($verbose
      and $data =~/deflate ([0-9][ 0-9a-zA-Z.\-]{1,100}[0-9a-zA-Z.\-])/) {
    print "$file: deflate version: \"$1\"\n";
    $found = 0;
  }

  if ($data =~ /$cplens_table_le/o) {
    print "$file: zlib cplens table, little endian\n";
    $found = 0;
  }
  if ($data =~ /$cplens_table_be/o) {
    print "$file: zlib cplens table, big endian\n";
    $found = 0;
  }
  if ($data =~ /$cplext_table_092/o) {
    print "$file: zlib cplext table (version 0.1 to 0.92)\n";
    $found = 0;
  }
  if ($data =~ /$cplext_table_104/o) {
    print "$file: zlib cplext table (version 0.93 to 1.0.4)\n";
    $found = 0;
  }
  if ($data =~ /$cplext_table_114/o) {
    print "$file: zlib cplext table (version 1.0.5 to 1.1.4)\n";
    $found = 0;
  }
  next if not $verbose;

  if ($data =~ /$config_table_le_32/o) {
    print "$file: zlib configuration table, little endian, 32 bit\n";
    $found = 0;
  }

  if ($data =~ /$config_table_be_32/o) {
    print "$file: zlib configuration table, big endian, 32 bit\n";
    $found = 0;
  }
  if ($data =~ /$config_table_le_64/o) {
    print "$file: zlib configuration table, little endian, 64 bit\n";
    $found = 0;
  }
  if ($data =~ /$config_table_be_64/o) {
    print "$file: zlib configuration table, big endian, 64bit\n";
    $found = 0;
  }

  my $msg = 0;
  my $total = 0;
  $msg++ if $data =~ /empty distance tree with lengths/; $total++;
  $msg++ if $data =~ /incomplete distance tree/; $total++;
  $msg++ if $data =~ /incomplete dynamic bit lengths tree/; $total++;
  $msg++ if $data =~ /incomplete literal\/length tree/; $total++;
  $msg++ if $data =~ /incorrect data check/; $total++;
  $msg++ if $data =~ /incorrect header check/; $total++;
  $msg++ if $data =~ /invalid bit length repeat/; $total++;
  $msg++ if $data =~ /invalid block type/; $total++;
  $msg++ if $data =~ /invalid stored block lengths/; $total++;
  $msg++ if $data =~ /invalid stored block lengths/; $total++;
  $msg++ if $data =~ /invalid window size/; $total++;
  $msg++ if $data =~ /need dictionary/; $total++;
  $msg++ if $data =~ /oversubscribed distance tree/; $total++;
  $msg++ if $data =~ /oversubscribed dynamic bit lengths tree/; $total++;
  $msg++ if $data =~ /oversubscribed literal\/length tree/; $total++;
  $msg++ if $data =~ /too many length or distance symbols/; $total++;
  $msg++ if $data =~ /too many length or distance symbols/; $total++;
  $msg++ if $data =~ /unknown compression method/; $total++;
  if ($msg > 0) {
    print "$file: $msg out of $total messages\n";
    $found = 0;
  }
}
exit $found;