#!/usr/bin/perl

system("date \"+%m/%d/%y %H:%M\" | md5sum | sed s/\"  -\"/\"\"/ > FirstDate");

#Open FirstDate for input
open(IN,"FirstDate");
#Read the string into $Date
$Date=<IN>;
#Close the file
close(IN);

#Repeat for the Key
open(IN,"Key");
$KEYL=<IN>;
close(IN);

print "DateMD5 \n$Date\n";
print "KEYMD5 \n$KEYL\n";

#MD5 Subroutines
sub md5_unpack{ unpack "H*", shift }
sub md5_pack { pack "H*", shift }

#print "MD5Pack KEYL\n";
#print md5_pack($KEYL);
#print "\nMD5Pack SD\n";
#print md5_pack($Date);

#Pack both Key and Date then Xor, then Unpack back to MD5
$xor = md5_unpack md5_pack($KEYL) ^ md5_pack($Date);

#print "\nPacked MD5 XOR\n";
#print md5_pack($KEYL) ^ md5_pack($Date);

#Chop off the last two Zeros left over from md5_upack
chop($xor);
chop($xor);

print "\nMD5 Unpacked XOR\n";
print $xor;


#Write our XOR result to a file
open(OUT,">MD5This");
print OUT $xor;
close(OUT);

#MD5 the the XOR String, store result in itself but first strip all text but the checksum.
system("md5sum MD5This|sed s/\"  MD5This\"/\"\"/> MD5This");

#Read the MD5'd XOR string back into $xor
open(IN, "MD5This");
$xor=<IN>;
close(IN);

print "\nMD5'd XOR Result\n";
print $xor;

#Convert $xor into an array.
@xor = $xor;
my @splits;
my @splits2;

#Split @xor at every 4th character, into seperate array entries
foreach my $keyline (@xor)
{
 @splits = $keyline =~ /(.{1,4})/g;
}

#Open knockd.conf
open(OUT, ">knockd.conf");

#Print basic knockd information
print OUT "[options]\nlogfile = /var/log/knockd.log\n";

#For each 4 characters we split earlier, convert them to Decimal.  This gives ports from 0 - 65535 from 0000 - FFFF
foreach my $test (@splits)
{
push(@splits2, hex($test));
}

#Up to 15 Scripts in Knockd.conf
#Print out the ports and the argument to pass knockScript
for ($count=1;$count<15;$count++)
{
print OUT "[knock$count]\nsequence = ";
print OUT "$count,$splits2[0],$splits2[1],$splits2[2],$splits2[3],$splits2[4],$splits2[5],$splits2[6],$splits2[7]\n";
print OUT "seq_timeout = 10\ntcpflags = syn\ncommand = ./knockScript $count %IP%\n";
}

close(OUT);

print "\n\n";

#Delete Temp Files
system("rm FirstDate");
system("rm MD5This");