#!/usr/bin/perl -w

# dlkern v41, created by Darxus@ChaosReigns.com.
#
# 100% PURE FEATURE BLOAT
#
# Queries ftp.kernel.org for current Linux kernel versions, via finger,
# and then downloads the requested versions (stable/beta/pre-patch) as
# specified by commandline flags, from ftp.kernel.org using ncftpget or
# wget, and will automatically verify signitures if GnuPG.pm
# (http://indev.insu.com/GnuPG/gnupg.html & http://www.gnupg.org/)  is
# present.
#
# Execute "dlkern -h" for usage.
#
# Example:
#
#  dlkern -s -c us
#
# will download the current stable (-s) version from the United States (-c us) 
# mirror.  It is strongly recommended that you use -c to specify your 2 letter
# country code, from the list at http://www.kernel.org/mirrors/ but it is not
# manditory.
#
# This program is is released under the GNU GPL
# (http://www.gnu.org/copyleft/gpl.html)
#
# Requirements:
# * Perl
#
# Requirements for signiture verification:
# * GnuPG.pm
# * gpg
# * The kernel archive public key must be added to your keyring
#
# To add the Kernel Archive public key to your keyring, execute:
# wget http://www.kernel.org/signature.html && gpg --import signature.html
#
# Net::Finger may be obtained from:
# Debian package:  libnet-finger-perl
# RedHat package:  perl-Net-Finger
# Others:  http://search.cpan.org/search?dist=Net-Finger
#
# TODO:
# * Verbose signiture output.
# * Allow specification of mirror to download from.
# * Use netselect to select mirror.
# * Config file to store parameters.
# * handle case where GnuPG.pm is present, but gpm is not in the path.
# * Detect presence of downloaders, set default accordingly.
# * If no downloader found, use Net::FTP
# * Make more cron friendly ?
# * Use uname & if_exist output_file to see if it actually needs to be downloaded.
# * Debian package.
# * RedHat package.
# * use strict.
#
# For mct to do:
# * Hostname & filename expanders for -d
# * Handle directory names being passed to -d (old versions used -d
#   for output directory, which is now -o)
#
# v15 Jan  9 20:28 EST 1st release.
# v16 Jan 20 01:09 EST Changed finger address from "@linux.kernel.org" (not 
#                      working) to "@ftp.kernel.org".
# v17 Jan 21 14:43 EST Code cleanup & documentation.
# v18 Jan 21 15:19 EST wget support.
# v19 Jan 21 15:29 EST Handle prepatch version "none".
# v20 Jan 21 15:59 EST Handle failed finger.
# v21 Jan 21 16:18 EST Output directory argument.
# v22 Jan 21 16:47 EST Added support for The Linux Kernel Archive Mirror System.
# v23 Jan 21 16:54 EST Allow specification of filetype (.gz/.bz2).
# v23 Jan 21 17:00 EST -h (usage) flag.
# v24 Jan 21 17:18 EST Fixed a couple minor warnings.
# v25 Jan 21 18:34 EST Automatically download signitures (inebrieated).
# v26 Jun 13 16:32 EDT Removed beginnings of signiture verification so
#                      signiture download could work cleanly.
# v27 Jun 14 18:02 EDT Automatic signiture verification.
# v28 Jun 14 18:21 EDT Cleanup.
# v29 Jun 17 14:17 EDT Compensate for pre-patch location change.
# v30 Jun 17 14:54 EDT Clarified signiture verification failure output.
# v31 Jun 17 15:29 EDT Unbroke pre-patch signiture verification.
# v32 Jun 18 21:43 EDT Added -- option to specify arguments to downloader w/
#                      help from michael@toren.org.
# v33 Jun 18 22:48 EDT Allow specification of any downloader via -d (Suggested by
#                      mct).  Changed output directory flag to -o.  Clearer 
#                      output when proper flags are not specified for downloaders 
#                      & versions.
# v34 Jun 18 23:25 EDT Put back default downloader (ncftpget) removed in v33.
# v35 Jun 19 09:19 EDT use strict.  Aren't you all proud ?
# v36 Jun 19 09:25 EDT Default to downloading stable, if none specified.
# v37 Jun 19 09:59 EDT -u: only display URLs.  Stopped displaying args.
# v38 Jun 19 10:16 EDT -h displays URLs.
# v39 Jun 19 13:59 EDT Nolonger dependant on Net::Finger.
# v40 Jun 19 14:38 EDT Output error if call to downloader fails.  Added -w.
# v41 Jun 20 17:08 EDT Handle absence of downloaders more gracefully.
#
# I decided I don't like standard version numbers.  The version numbers for this
# program started at "1", and have been incremented every time I made a change.
# Numbers before 15 were not fit for public consumption.

use strict;
use vars qw(@new $i @dl_args $usage $opt_s $opt_b $opt_p %dl $opt_c $country $opt_d $downloader $opt_e 
$ext $opt_h $opt_o $dir $gnupg $gpg %trust @trees $tree_count $tree $dl_count $opt_w $opt_n @lines
$line $desc $ver %version $first $second %url %file $date $sig $opt_u $host $port $handle $opt_n);

# Load the Net::Finger module so I don't have to do any work to get the version 
# info via finger.
#use Net::Finger;
# Nolonger dependant on Net::Finger.
use IO::Socket;

# Create a list of version types (is "trees" an appropriate name?)
@trees = ("stable", "beta", "prepatch");

##########################################
#Grab downloader args, mostly by mct BEGIN

while ($i = shift @ARGV)
{
    if ($i eq "--")
    {
        @dl_args = @ARGV;
        last;
    }
    push @new, $i;
}
@ARGV = @new;

# For verbose output:
#print "dlkern args:\n", join("\n", @ARGV), "\n";
#print "downloader args:\n", join("\n", @dl_args), "\n";

#Grab downloader args END
#########################

###########################################
#Handle arguments (not to downloader) BEGIN

# Load getopts to read commandline options.
require 'getopts.pl';


# Read commandline options.  Colon goes after flags that take arguments.
&Getopts('usbpwnhd:c:e:o:');

sub usage {
################################################################################
print "
Usage:  dlkern [-sbp] [-nw | -d <downloader>] [-o <directory>] 
        [-c <country_code>] [-e <gz|bz2>] -- <downloader args>

        -s  Download stable version of Linux kernel.
        -b  Download beta version of Linux kernel.
        -p  Download prepatch version of Linux kernel.

        -n  Use ncftpget as downloader (default).
        -w  Use wget as downloader.
        -d  Specify another downloader.

        -o  Specify output directory.
        -c  Specify 2 letter country code from http://www.kernel.org/mirrors/
        -e  Specify extension (gz is default, bz2 is more compressed).
        -h  Show this usage information.

        -u  Only display URLs.  May use -c & -e.

        --  Specify aruments to the downloader.  Must be last.
   
" unless ($usage);
$usage=1;
}

# If there are no commandline options, display usage.  Normally you'd exit after
# displaying usage, but I keep going to display the URLs.
# Nolonger using this as of v36, defaulting to stable.
#unless ($opt_s or $opt_b or $opt_p)
#{
#  &usage;
#}

# Check kernel version flags, store info in the #dl hash, with the version
# type as the key.
# opt_e & opt_c must come before opt_u & opt_h.
if ($opt_e) { $ext = $opt_e; } else { $ext = "gz"; }
if ($opt_c) { $country = ".$opt_c"; } else { $country = ""; }
if ($opt_u) { &get_urls; exit(1); }
if ($opt_h) { &usage; &get_urls; exit; }
if ($opt_b) { $dl{"beta"}=1; }
if ($opt_d) { $downloader = $opt_d; }
if ($opt_o) { $dir = $opt_o; }
if ($opt_p) { $dl{"prepatch"}=1; }
if ($opt_s) { $dl{"stable"}=1; }

#Handle arguments (not to downloader) END
#########################################

####################
#Load GnuPG.pm BEGIN

if (!eval "require 'GnuPG.pm';") {
  print "No GnuPG.pm (http://indev.insu.com/GnuPG), cannot verify signitures.\n";
  $gnupg=0;
} else {
  print "GnuPG.pm loaded.\n";
  $gnupg=1;
  $gpg = new GnuPG();

  %trust = (-1, "UNDEFINED",
             0, "NEVER",
             1, "MARGINAL",
             2, "FULLY",
             3, "ULTIMATE");
}

#Load GnuPG.pm END
##################


# Use info from the commandline to list the versions that were requested.
$tree_count = 0;
print "Requested:";
foreach $tree (@trees)
{
  if ($dl{$tree})
  {
    print " $tree";
    $tree_count++;    
  }
}
unless ($tree_count)
{
  print " None.  Downloading stable.\n";
  $dl{"stable"}=1;
} else {
  print ".\n";
}

# Check downloader flags.

$dl_count = defined($opt_w) + defined($opt_n) + defined($downloader);

if ($dl_count > 1)
{
  &usage;
  print "You specified $dl_count downloaders.  Only specify 1.\n";
} elsif ($downloader)
{ # This space left intentionally blank.  I want an elsunless :)
} elsif ($opt_w) {
  $downloader="wget";
} elsif ($opt_n) {
  $downloader="ncftpget";
}

unless (&chkexe($downloader))
{
  print "$downloader does not appear to be installed.\n";
  $downloader = "";
}

unless ($downloader)
{
  if (&chkexe("ncftpget"))
  {
    $downloader="ncftpget";
  } elsif (&chkexe("wget")) {
    $downloader="wget";
  } else {
    print "No downloader was found.  Please install ncftpget or wget, or specify \nanother downloader via -d.\n\n";
    &get_urls; 
    exit(1);
  }
}

print "Downloader: $downloader.\n\n";


# Parse finger data into URLs.  Store them in the hash #url, using the tree 
# name for the key.
&get_urls;
sub get_urls {
  print "Retrieving version numbers:\n";
  # Query finger data.
  #@lines = finger('@ftp.kernel.org', 1) or die "Failed to obtain version info by fingering \@ftp.kernel.org.\n";

  $host = "ftp.kernel.org";
  $port = 79;

  unless ($handle = IO::Socket::INET->new(Proto     => 'tcp',
                                          PeerAddr  => $host,
                                          PeerPort  => $port))
  { 
    print "Failed to make finger connection to $host:$port.\n";
  } 

  print $handle "\n\r";

  while (<$handle>)
  { 
    s/(\n|\r)+/\n/g; #Net::Finger seemed to think this should be here.
    push @lines, $_;
  }

  #print "@lines\n";
  foreach $line (@lines)
  { 
    #Split each line into the description & version, using a ":" as a delimiter.
    ($desc, $ver) = split /:/, $line;

    if (defined($ver))
    { 
      #Strip spaces out of $ver.
      $ver =~ tr/" \n"//d;

      foreach $tree (@trees)
      { 
        if ($desc =~ $tree)
        { 
          $version{$tree} = $ver;
          print "$tree: $version{$tree} ";

          if ($tree eq "stable" or $tree eq "beta")
          { 

            # For kernel version 2.3.40, set $first equal to "2", and $second equal
            # to "3", so this thing still works when 2.4.x or 3.x.x happens, as long
            # as their path naming conventions stay the same.
            ($first, $second) = split /\./, $version{$tree};

            $url{$tree} = "ftp://ftp$country.kernel.org/pub/linux/kernel/v$first.$second/linux-$version{$tree}.tar.$ext";
            $file{$tree} = "linux-$version{$tree}.tar.$ext";
          } elsif ($ver eq "none") { 
            $url{$tree} = "";
          } else { 
            (undef,$date) = split(/\//, $version{$tree});
            $url{$tree} = "ftp://ftp$country.kernel.org/pub/linux/kernel/testing/pre$date.$ext";
            $file{$tree} = "pre$date.$ext";
          } 

          print "$url{$tree}\n";
        } 
      } 
    }
  }
}

if ($dir)
{
  print "Changing to output directory: $dir\n";
  chdir ($dir) or die "Can't cd to $dir $!\n";
}

# Call ncftpget for each requested tree.
foreach $tree (@trees)
{
  if ($dl{$tree})
  {
    if ($url{$tree})
    {
      print "\nDownloading $tree by calling \'$downloader \"",join('" "',@dl_args),"\" $url{$tree}\'\n";
      system ($downloader, @dl_args, "$url{$tree}") == 0 or print "Download failed: ",$? >> 8,"\n";
      print "Downloading $tree signiture by calling \'$downloader \"",join('" "',@dl_args),"\" $url{$tree}.sign\'\n";
      system ($downloader, @dl_args, "$url{$tree}.sign") == 0 or print "Download failed: ",$? >> 8,"\n";

      #linux-2.2.14.tar.gz.sign
      #$sig = $gpg->verify( signature => "linux-$version{$tree}.tar.$ext.sign", file => "linux-$version{$tree}.tar.$ext" );
      if ($gnupg)
      {
        print "Verifying $tree tarball $file{$tree} with signiture $file{$tree}.sign:\n";

        if (eval { $sig = $gpg->verify( signature => "$file{$tree}.sign", file => "$file{$tree}" );})
        {
          print "Signiture passed verification.\n";
          # For verbose output:
          #print "Signiture info:\n";
          #for $key (sort(keys(%$sig)))
          #{
          #  print "$key: $$sig{$key}\n";
          #}

          print "Signiture timestamp: ",scalar(localtime($$sig{"timestamp"})),"\n";
          print "Trust level for this signiture is: $trust{$$sig{trust}}\n";

        } else {
          print "SIGNITURE DID NOT PASS VERIFICATION.  Possible reasons:\n";
          print " * Kernel source has been maliciously modified.\n";
          print " * Kernel tarball or signiture was corrupted during download.\n";
          print " * You did not insert the kernel archive public key into your keyring via:\n";
          print "   wget http://www.kernel.org/signature.html && gpg --import signature.html\n";
        }
      }

    } else {
      print "There is currently no $tree version.\n";
    }
  }
}

sub chkexe
{
  return (system ("which $_[0] > /dev/null") == 0);
 }