#!/usr/bin/perl -w

use strict;

use IPC::Open2;
use FileHandle;
use MIME::Base64;
use POSIX;

$| = 1;

if (!defined($ENV{GREETING}) || !defined($ENV{EHLORESP}))
{
    die "You must set the environment variables GREETING and EHLORESP.\n";
}

#$GREETING="220 mailweb.flinthomes.net ESMTP\r
#";
#$HELORESP="250-mailweb.flinthomes.net\r
#250-PIPELINING\r
#250-8BITMIME\r
#";

$ENV{GREETING} =~ s/\n/\r\n/g;
$ENV{EHLORESP} =~ s/\n/\r\n/g;

print $ENV{GREETING};
$ENV{SENTGREETING}=1;

while (my $l = <STDIN>)
{
  if ($l =~ /^EHLO/i)
    {
      print $ENV{EHLORESP};
      print "250 AUTH PLAIN\r\n";
      $ENV{EHLO}=$l;
    }
  elsif ($l =~ /^AUTH(.*)$/i)
    {
      if ($1 =~ /^\s+PLAIN\s+(\S*)\s*$/i)
	{
	  my($authorize,$authenticate,$pwd)=split(/\0/,decode_base64($1));
	  if (!defined($authorize) || !defined($authenticate) || !defined($pwd))
	    {
	      print "501 Unable to decode password.\r\n";
	      next;
	    }
	  &authproxy($authenticate,$pwd);
	}
      print "504 Unrecognized authentication type.\r\n";
    }
  else
    {
      $ENV{CMD}=$l;
      last;
    }
}

&runproxy;

sub runproxy
{
  shift @ARGV;
  exec(@ARGV);
  exit(0);
}

sub authproxy
{
  my($user,$pass)=@_;

  $ENV{RELAYCLIENT}="";
  $ENV{AUTHENTICATED}=$user;

  my($fdR,$fdW) = POSIX::pipe()
    or die "Couldn't create pipe: $!\n";
  
  warn "Starting authproxy\n";
  my $pid = fork;
  defined $pid or die "fork failed\n";
  if (!$pid)
    {
      # Child
      POSIX::dup2(3,$fdR)
	unless ($fdR == 3);

      POSIX::close($fdW)
	unless ($fdW == 3);

      warn "exec('".join("', '",@ARGV)."')\n";
      exec(@ARGV);
      die "exec error: $!\n";
    }
  # Parent
  POSIX::close($fdR);
  open(AUTHOUT,">&=$fdW")
    or die "Couldn't open fd #$fdW as AUTHOUT: $!\n";
  print AUTHOUT "$user\0$pass\0";
  close(AUTHOUT);
  wait == $pid or die "Bad pid returned by wait (?!?)\n";
  
  if ($? == 0)
  {
      ;
  }
  elsif ($? == 1)
  {
      print "535 Authentication credentials rejected\r\n";
  }
  elsif ( ($? == 2) || ($? == 111) )
  {
      print "454 Temporary authentication error\r\n";
  }
  else
  {
      warn "Child process exited with $?\n";
  }
  exit(0);
}