Timeout of detached threads to prevent DOS Attack

Stefan Donoval Sat, 05 Apr 2008 19:23:01 -0700

Hi,

i wrote a prethreading server deamon that also reuse finished threads.
However I have a problem with possibel DOS attacks.
$fh is the


my $STATUS       = '';
my %STATUSTIME   = 0;
my $ACCEPT_LOCK  = '';
my %STATUS       = ();
my $DONE         = 0;
share(%STATUS);
share(%STATUSTIME);
share($ACCEPT_LOCK);

$SIG{INT} = $SIG{TERM} = sub { $DONE++ };
$SIG{ALRM} = sub {};

#MAIN Webserver with Multithreading
print "Binding socket on $ip_listen Port $port_listen\n";
#Bind Socket

my $socket = IO::Socket::INET->new( LocalPort => $port_listen,
                                    LocalAddr => $ip_listen,
                                    Listen    => 100,

Reuse => 1 ) or die "Can'tcreate listen socket: $!";

my $SOCKIN = IO::Select->new($socket);

launch_thread($socket) for (1..$PRETHREAD);  # launch threads

while (!$DONE) {
  lock %STATUS;
  cond_wait %STATUS;
  warn join(' ', map {"$_=>$STATUS{$_}"} keys %STATUS),"\n" if DEBUG;
  my @idle = sort {$a <=> $b} grep {$STATUS{$_} eq 'idle'} keys %STATUS;
  my @busy = sort {$a <=> $b} grep {$STATUS{$_} eq 'busy'} keys %STATUS;
  if (@idle < $LO_WATER_MARK) {

launch_thread($socket) for ([EMAIL PROTECTED]); # bringthe number up

  } elsif (@idle > $HI_WATER_MARK) {

my @goners = @[EMAIL PROTECTED] - $HI_WATER_MARK - 1]; # kill theoldest ones

    status($_ => 'goner') foreach @goners;
    warn "decomissioning @goners\n" if DEBUG;
  }
  if (scalar(@busy) > $threadsmaxbusy) {
    $threadsmaxbusy=scalar(@busy);
  }
}
warn "Server will terminate when last thread has finished...\n" if DEBUG;
status($_ => 'goner') foreach keys %STATUS;
exit 0;

sub do_thread {
  my $socket = shift;
  my $cycles = $MAX_REQUEST;
  my $tid = threads->self->tid;
  my $c;
  warn "Thread $tid: starting\n" if DEBUG;
  threads->self->detach;        # don't save thread status info
  $SIG{__DIE__} =  sub {&status($tid=>undef);close $c;};
  status($tid => 'idle');
  while (status($tid) ne 'goner' && $cycles > 0) {
    next unless $SOCKIN->can_read(1);
    {
      lock $ACCEPT_LOCK;
      next unless $c = $socket->accept();

    }
    $cycles--;
    status($tid => 'busy');
    $STATUSTIME{$tid}=time;
    warn "Thread $tid: handling connection\n" if DEBUG;
    new_connection($c);
    close $c;
    status($tid => 'idle');
  }
  warn "Thread $tid done\n" if DEBUG;
  status($tid=>undef);
  exit 1;
}

sub status {
  my $tid = shift;
  lock %STATUS;
  return $STATUS{$tid} unless @_;
  my $status = shift;
  if ($status) {
    $STATUS{$tid} = $status
      unless defined $STATUS{$tid} and $STATUS{$tid} eq 'goner';
  } else {
    delete $STATUS{$tid};
    delete $STATUSTIME{$tid};
  }
  cond_broadcast %STATUS;
}

sub new_connection {
        my $fh = shift;
        my $ip = "";
        my $port = "";
        my $iaddr = "";
  my $return = eval(($port, $iaddr) = sockaddr_in(getpeername($fh)));
  if ($return) {
    $ip=inet_ntoa($iaddr);
        binmode $fh;
        my $doexit = 0;
        my %req;
        $req{HEADER}={};

        my $request_line = <$fh>; <== Here is the problem
....

if i write a simple cgi-script

use IO::Socket;

my $socket = new IO::Socket::INET( PeerAddr => $deamonserver, PeerPort=> 80, Proto => 'tcp', );

if ($socket)   {
  my $counter=0;
  while (1) {
    sleep 1;
    $counter++;
    print "$counter\n";
  }
  close($socket);
}
The server will never break out the thread

With forking servers I used to do it with ALRM signal,
but this doesn't work with threads.

Any solution?

I am searching arround the net now for more than one week,
and didn't didn't find any solution.
Neither socket timeout works nor any signal handler modul I tired.

Thank you for helping

Timeout of detached threads to prevent DOS Attack

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