(Note: the size given by unshar may be wrong due to tab mangling.)

Subject: Script for running ppp over ssh
From: Olaf Titz <olaf@bigred.inka.de>
Date: 12 Oct 1996
Message-Id: <dz6jxe.g63@bigred.inka.de>
Organization: private Linux site, southern Germany
Newsgroups: alt.sources,comp.security.unix

This program is a bit trivial IMHO, but there seems to be popular
demand for it. :-)

Note that on my system (Linux 2.0.12, ssh 1.2.13) the original version
of this program fails in a subtle way. After requesting a pty, the
local ssh process hangs in some blocking read operation. It can
however be revived by sending the process SIGSTOP and then SIGCONT.
Looks like a problem with nonblocking I/O (or failure to activate it).
I don't know if the error exists in other versions of ssh or on other
platforms. I have included a kluge around that: -b<s> will send it the
mentioned signals after <s> seconds.

olaf

#!/bin/sh
# This is a shell archive (produced by GNU sharutils 4.1).
# To extract the files from this archive, save it to some FILE, remove
# everything before the `!/bin/sh' line above, then type `sh FILE'.
#
# Made on 1996-10-12 22:32 MET DST by <olaf@bigred.inka.de>.
# Source directory was `/var/home/olaf/security'.
#
# Existing files will *not* be overwritten unless `-c' is specified.
#
# This shar contains:
# length mode       name
# ------ ---------- ------------------------------------------
#   1787 -rwxrwxr-x ssh-ppp
#
touch -am 1231235999 $$.touch >/dev/null 2>&1
if test ! -f 1231235999 && test -f $$.touch; then
  shar_touch=touch
else
  shar_touch=:
  echo
  echo 'WARNING: not restoring timestamps.  Consider getting and'
  echo "installing GNU \`touch', distributed in GNU File Utilities..."
  echo
fi
rm -f 1231235999 $$.touch
#
# ============= ssh-ppp ==============
if test -f 'ssh-ppp' && test X"$1" != X"-c"; then
  echo 'x - skipping ssh-ppp (file already exists)'
else
  echo 'x - extracting ssh-ppp (text)'
  sed 's/^X//' << 'SHAR_EOF' > 'ssh-ppp' &&
#!/usr/bin/perl
X
# Start an ssh connection and a pppd running on top of it.
# Usage: ssh-ppp [-l user] [-c command] [-b seconds] host
# Connect to "host" using the user name "user" and run "command" on the
# remote end. (Default is "root" and "/usr/sbin/pppd")
# by Olaf Titz, July 1996
X
require "getopts.pl";
require "sys/syscall.ph";
X
# Customize if necessary
$ssh="/usr/local/bin/ssh";
$pppd="/usr/sbin/pppd";
X
# defaults
$opt_l="root";
$opt_c="/usr/sbin/pppd";
&Getopts("l:c:b:");
($host=shift) || die "usage: $0 [-l user] [-c command] host";
X
foreach $maj ("p".."s") { # adjust this to the ptys you have
X    foreach $min ("0".."9", "a".."f") {
X       &tryopen("$maj$min");
X    }
}
die "Couldn't alloc master pty\n";
X
sub tryopen
{
X    local($d)=@_;
X    $master=sprintf("/dev/pty%s", $d);
X    $slave=sprintf("/dev/tty%s", $d);
X    if (open(PTY, "+>$master")) {
X       $pid=fork;
X       defined($pid) || die "can't fork";
X       if (!$pid) {
X           close PTY;
X           (syscall(&SYS_setsid)>0) || die "setsid: $!";
X           open(STDIN, "+>$slave") ||
X               die "open slave: $!";
X           open(STDOUT, ">&STDIN");
X           open(STDERR, ">&STDIN");
X           print STDOUT "\n";
X           exec $pppd;
X           die "exec $pppd: $!";
X       }
X       open(STDIN, "<&PTY") || die "reopen stdin";
X       open(STDOUT, ">&PTY") || die "reopen stout";
X       close PTY;
X       $opt_l="-l$opt_l";
X       &bugdaemon($opt_b) if ($opt_b);
X       print STDERR "running on $master; ssh=$$, pppd=$pid\n";
X       exec $ssh, "-t", $opt_l, $host, $opt_c;
X       die "exec $ssh: $!";
X    }
}
X
sub bugdaemon
# This cures a "hang" of the local ssh process
{
X    local($secs)=@_;
X    local($p)=fork;
X    if (!defined($p)) {
X       warn "can't fork, no bug daemon";
X       return;
X    }
X    return if (!$p);
X    # returning the child avoids a zombie
X    sleep $secs;
X    kill "STOP", $p;
X    sleep 1;
X    kill "CONT", $p;
X    exit 0;
}
SHAR_EOF
  $shar_touch -am 1012222596 'ssh-ppp' &&
  chmod 0775 'ssh-ppp' ||
  echo 'restore of ssh-ppp failed'
  shar_count="`wc -c < 'ssh-ppp'`"
  test 1787 -eq "$shar_count" ||
    echo "ssh-ppp: original size 1787, current size $shar_count"
fi
exit 0
--
___        Olaf.Titz@inka.de or @{stud,informatik}.uni-karlsruhe.de       ____
__ o           <URL:http://www.inka.de/~bigred/>     <IRC:praetorius>
__/<_              >> Just as long as the wheels keep on turning round
_)>(_)______________ I will live for the groove 'til the sun goes down << ____