#!/usr/bin/perl -w
#
# $Id: ssh-ppp 356 2011-09-24 23:25:47Z svnuser $
#
# $Log: ssh-ppp,v $
# Revision 1.9  1999/07/06 22:22:27  merlin
# Name option is really an option now
# Removed full pathnames
#
# Revision 1.8  1999/06/17 00:42:51  merlin
# Added -n option, and added SIGTERM to the list of signals after which we
# cleanup (Doh!)
#
# Revision 1.7  1999/06/15 00:34:21  merlin
# Boy, this works sooo much better if you run ssh in the child and ppp in the
# father.
# I also made the script a little more robust
#
# Revision 1.6  1999/06/14 22:15:22  merlin
# Lots of minor changes as I was chasing an annoying bug my($d)=@_ vs my $d=@_
# but now this script works again.
#
# Revision 1.5  1999/06/10 18:13:51  merlin
# Added lock detection
#
# Revision 1.4  1999/06/09 18:32:50  merlin
# Cleaned up, added some more debugging stuff and a sample call command line
#
# Revision 1.3  1998/07/10 06:42:17  merlin
# Erased useless fifo
#
# Revision 1.2  1998/05/25 19:19:40  merlin
# A bunch of modifications and hacks to make it work
#
# Revision 1.1  1998/05/24 05:23:44  merlin
# First version checked in CVS
#


# Start an ssh connection and a pppd running on top of it.
# by Olaf Titz, July 1996
#
# Lots of modifications by Marc Merlin <marcsoft@merlins.org>, more than
# half done on VA Linux Systems' time (http://www.valinux.com/)
#
# Sample call:
# ssh-ppp -v -d -l remotepppuser distanthost


require "getopts.pl";
require "sys/syscall.ph";
use FileHandle;

STDIN->autoflush(1);
STDOUT->autoflush(1);
STDERR->autoflush(1);


# I know, most of those should never happen, but I like to be safe :-)
$SIG{'HUP'} = $SIG{'INT'} = $SIG{'QUIT'} = $SIG{'ILL'} = $SIG{'TRAP'} = $SIG{'ABRT'} = $SIG {'FPE'} = $SIG {'BUS'} = $SIG {'SEGV'} = $SIG {'PIPE'} = $SIG {'ALRM'} = $SIG{'QUIT'} = 'sighld';


# disable escape, and compress
#$ssh="ssh -c blowfish -e none -C -v -P";
$ssh="ssh -c idea -e none -C -v -P";
$pppd="pppd nodetach noipdefault lcp-echo-failure 2";

# defaults
# It's safer to put a script in the remote user that starts ppp
#$opt_c="pppd";
$opt_c="";
chomp($opt_l=`whoami`);
$opt_n="";
$opt_p="22";
$opt_d=0;
$opt_v=0;
Getopts("p:c:l:n:d:v");

$pppd =~ s/pppd/pppd name $opt_n/ if ($opt_n);
$debug=$opt_d;
$verbose=$opt_v;
$opt_l="-l $opt_l";
$opt_p="-p $opt_p";
$pppd =~ s/pppd/pppd debug/ if $verbose;
$opt_c =~ s/pppd/pppd debug/ if $verbose;

($host=shift) or die "usage: $0 [-v] [-d file] [-p port] [-l user] [-n local ppp hostname/username] [-c command] host";

if ($debug)
{
    open(CONSOLE, ">>$debug") or die "Can't open debugging file/device $debug: $!";
    # Used by the father of the next fork to warn bugdaemon before starting ppp
    CONSOLE->autoflush(1);
}

srand(time);
$fifofile="/tmp/ssh_ppp.$$".rand(99999);
system "mkfifo -m 600 $fifofile";

foreach $maj ("p".."s") 
{
    foreach $min ("0".."9", "a".."f") 
    {
       tryopen("$maj$min");
    }
}
die "Couldn't alloc master pty\n";


sub tryopen
{
    my ($d)=@_;

    $master=sprintf("/dev/pty%s", $d);
    $slave=sprintf("/dev/tty%s", $d);

    if (open(PTY, "+<$master")) 
    {
	$pid=fork;
	defined($pid) or die "can't fork: $!";

	if ($pid) 
	{
	    close PTY;
	    print CONSOLE "Father: reading from fifo while waiting for child to complete ssh connection\n" if $debug;

	    open(FIFO, "$fifofile") or die "Can't open fifo: $!";
	    FIFO->autoflush(1);

 	    while (<FIFO>)
 	    {
 		print CONSOLE "Child sent: $_" if $debug;
 		last if /Entering interactive session./;
		last if /Permission denied./;
		last if /Host key not found from the list of known hosts/;
		last if /Selected cipher type .* not supported by server./;
		# If you find something to add here, let me know -- Marc
	    }
	    if (! defined($_) or ! /Entering interactive session./)
	    {
		$_="\n[unexpected output from ssh. Rerun in debug mode and look at log file]" if (! defined($_));
		print CONSOLE "Father: connection aborted: $_\n" if $debug;
		print CONSOLE "Father: killing child (pid $pid)\n" if $debug;
		kill (15, $pid);
		die "connection aborted, ssh returned: $_\n";
	    }
	    print CONSOLE "Father: ssh has connected\n" if $debug;
	    unlink($fifofile) or die "can't unlink $fifofile: $!";

	    open(STDIN, "+<$slave") or die "Can't open slave: $!";
	    open(STDOUT, ">&STDIN") or die "Can't dup2 STDOUT: $!";

	    # Yeah, it's a dirty kludge: ssh needs to be kicked for the ppp
	    # packets to be able to ride over it. Don't ask me why -- Marc
	    kill ("STOP", $pid);
	    sleep 1;
	    kill ("CONT", $pid);

	    print CONSOLE "Father: Going to run $pppd on $slave\n" if $debug;
	    exec $pppd;
	    die "Father: can't exec $pppd: $!";
	}
	else
	{
	    print CONSOLE "Child: running on $master; ssh=$$, pppd=".getppid."\n" if $debug;
	    open(STDIN, "<&PTY") or die "Can't dup2 STDIN: $!";
	    open(STDOUT, ">&PTY") or die "Can't dup2 STDOUT: $!";
	    close PTY;
	    
	    open(FIFO, ">$fifofile") or die "Can't open $fifofile for writing: $!";
	    open(STDERR, ">&FIFO") or die "Can't dup2 STDERR: $!";
	    
	    print CONSOLE "Child: about to run $ssh -t $opt_p $opt_l $opt_c $host\n" if $debug;
	    exec "$ssh -t $opt_p $opt_l $opt_c $host";
	    die "Child can't exec $ssh: $!";
	}
    }
}

sub sighld
{
    # Do some cleanup. It might get called by the father and the child, but
    # I don't care.
    unlink($fifofile);

    exit 0;
}