Users using Perl script to bypass Squid Proxy
- by mk22
The users on our network have been using a perl script to bypass our Squid proxy restrictions. Is there any way we can block this script from working??
#!/usr/bin/perl
########################################################################
# (c) 2008 Indika Bandara Udagedara
# [email protected]
# http://indikabandara19.blogspot.com
#
# ----------
# LICENCE
# ----------
# This work is protected under GNU GPL
# It simply says
# " you are hereby granted to do whatever you want with this
# except claiming you wrote this."
#
#
# ----------
# README
# ----------
# A simple tool to download via http proxies which enforce a download
# size limit. Requires curl.
# This is NOT a hack. This uses the absolutely legal HTTP/1.1 spec
# Tested only for squid-2.6. Only squids will work with this(i think)
# Please read the verbose README provided kindly by Rahadian Pratama
# if u r on cygwin and think this documentation is not enough :)
#
# The newest version of pget is available at
# http://indikabandara.no-ip.com/~indika/pget
#
# ----------
# USAGE
# ----------
# + Edit below configurations(mainly proxy)
# + First run with -i <file> giving a sample file of same type that
# you are going to download. Doing this once is enough.
# eg. to download '.tar' files first run with
# pget -i my.tar ('my.tar' should be a real file)
# + Run with
# pget -g <URL>
#
#
########################################################################
########################################################################
# CONFIGURATIONS - CHANGE THESE FREELY
########################################################################
# *magic* file
# pls set absolute path if in cygwin
my $_extFile = "./pget.ext" ;
# download in chunks of below size
my $_chunkSize = 1024*1024; # in Bytes
# the proxy that troubles you
my $_proxy = "192.168.0.2:3128"; # proxy URL:port
my $_proxy_auth = "user:pass"; # proxy user:pass
# whereis curl
# pls set absolute path if in cygwin
my $_curl = "/usr/bin/curl";
########################################################################
# EDIT BELOW ONLY IF YOU KNOW WHAT YOU ARE DOING
########################################################################
use warnings;
my $_version = "0.1.0";
PrintBanner();
if (@ARGV == 0)
{
PrintHelp();
exit;
}
PrimaryValidations();
my $val;
while(scalar(@ARGV))
{
my $arg = shift(@ARGV);
if($arg eq '-h')
{
PrintHelp();
}
elsif($arg eq '-i')
{
$val = shift(@ARGV);
if (!defined($val))
{
printf("-i option requires a filename\n");
exit;
}
Init($val);
}
elsif($arg eq '-g')
{
$val = shift(@ARGV);
if (!defined($val))
{
printf("-g option requires a URL\n");
exit;
}
GetURL($val);
}
elsif($arg eq '-c')
{
$val = shift(@ARGV);
if (!defined($val))
{
printf("-c option requires a URL\n");
exit;
}
ContinueURL($val);
}
else
{
printf ("Unknown option %s\n", $arg);
PrintHelp();
}
}
sub GetURL
{
my ($URL) = @_;
chomp($URL);
my $fileName = GetFileName($URL);
my %mapExt;
my $first;
my $readLen;
my $ext = GetExt($fileName);
ReadMap($_extFile, \%mapExt);
if ( exists($mapExt{$ext}))
{
$first = $mapExt{$ext};
GetFile($URL, $first, $fileName, 0);
}
else
{
die "Unknown ext in $fileName. Rerun with -i <fileName>";
}
}
sub ContinueURL
{
my ($URL) = @_;
chomp($URL);
my $fileName = GetFileName($URL);
my $fileSize = 0;
$fileSize = -s $fileName;
printf("Size = %d\n", $fileSize);
my $first = -1;
if ( $fileSize > 0 )
{
$fileSize -= 1;
GetFile($URL, $first, $fileName, $fileSize);
}
else
{
GetURL($URL);
}
}
sub Init
{
my ($fileName) = @_;
my ($key, $value);
my %mapExt;
my $ext = GetExt($fileName);
if ( $ext eq "")
{
die "Cannot get ext of \'$fileName\'";
}
ReadMap($_extFile, \%mapExt);
my $b = GetFirst($fileName);
$mapExt{$ext} = $b;
WriteMap($_extFile, \%mapExt);
print "I handle\n";
while ( ($key, $value) = each(%mapExt) )
{
print "\t$key -> $value\n";
}
}
sub GetExt
{
my ($name) = @_;
my @x = split(/\./, $name);
my $ext = "";
if (@x != 1)
{
$ext = pop @x;
}
return $ext;
}
sub ReadMap
{
my($fileName, $mapRef) = @_;
my $f;
my @arr;
open($f, '<', $fileName) or die "Couldn't open $fileName";
my %map = %{$mapRef};
while (<$f>)
{
my $line = $_;
chomp($line);
@arr = split(/[ \t]+/, $line, 2);
$mapRef->{ $arr[0]} = $arr[1];
}
printf("known ext\n");
while (($key, $value) = each(%$mapRef))
{
print("$key, $value\n");
}
close($f);
}
sub WriteMap
{
my ($fileName, $mapRef) = @_;
my $f;
my @arr;
open($f, '>', $fileName) or die "Couldn't open $fileName";
my ($k, $v);
while( ($k, $v) = each(%{$mapRef}))
{
print $f "$k" . "\t$v\n";
}
close($f);
}
sub PrintHelp
{
print "usage:
-h Print this help
-i <filename> Initialize for this filetype
-g <URL> Get this URL\n
-c <URL> Continue this URL\n"
}
sub GetFirst
{
my ($fileName) = @_;
my $f;
open($f, "<$fileName") or die "Couldn't open $fileName";
my $buffer = "";
my $first = -1;
binmode($f);
sysread($f, $buffer, 1, 0);
close($f);
$first = ord($buffer);
return $first;
}
sub GetFirstFromMap
{
}
sub GetFileName
{
my ($URL) = @_;
my @x = split(/\//, $URL);
my $fileName = pop @x;
return $fileName;
}
sub GetChunk
{
my ($URL, $file, $offset, $readLen) = @_;
my $end = $offset + $_chunkSize - 1;
my $curlCmd = "$_curl -x $_proxy -u $_proxy_auth -r $offset-$end -# \"$URL\"";
print "$curlCmd\n";
my $buff = `$curlCmd`;
${$readLen} = syswrite($file, $buff, length($buff));
}
sub GetFile
{
my ($URL, $first, $outFile, $fileSize) = @_;
my $readLen = 0;
my $start = $fileSize + 1;
my $file;
open($file, "+>>$outFile") or die "Couldn't open $outFile to write";
if ($fileSize <= 0)
{
my $uc = pack("C", $first);
syswrite ($file, $uc, 1);
}
do
{
GetChunk($URL, $file, $start ,\$readLen);
$start = $start + $_chunkSize;
$fileSize += $readLen;
}while ($readLen == $_chunkSize);
printf("Downloaded %s(%d bytes).\n", $outFile, $fileSize);
close($file);
}
sub PrintBanner
{
printf ("pget version %s\n", $_version);
printf ("There is absolutely NO WARRANTY for pget.\n");
printf ("Use at your own risk. You have been warned.\n\n");
}
sub PrimaryValidations
{
unless( -e "$_curl")
{
printf("ERROR:curl is not at %s. Pls install or provide correct path.\n", $_curl);
exit;
}
unless( -e "$_extFile")
{
printf("extFile is not at %s. Creating one\n", $_extFile);
`touch $_extFile`;
}
if ( $_chunkSize <= 0)
{
printf ("Invalid chunk size. Using 1Mb as default.\n");
$_chunkSize = 1024*1024;
}
}
