VPN via interactive session

expect.pl

#!/usr/bin/perl

# expect.pl (c) 2012 Piotr Roszatycki <dexter@debian.org>

use strict;
use Expect;

die "Usage: $0 cmd [-echo] expect1 send1 expect2 send2 ...\n"
    unless @ARGV;

my $cmd = shift @ARGV;

my $exp = Expect->spawn($cmd)
    or die "Cannot spawn $cmd: $!\n";

if ($ARGV[0] eq '-echo') {
    shift @ARGV;
    $exp->slave->stty(qw(-echo));
    $exp->log_stdout(0);
}

while (@ARGV) {
    my $expect = shift @ARGV;
    $exp->expect(10, $expect) or die "Cannot expect $expect\n";
    my $send = shift @ARGV;
    $exp->send(My::interpolate($send));
    $exp->exp_continue;
}

$exp->interact();


sub My::interpolate {
    local $_ = shift;
    return eval "qq($_)";
}

vpn-interact.sh

#!/bin/sh

IPNET=10.0.2.0

IPHOST="${IPNET%.0}.2"
SELF=`cd $(dirname $0); pwd`/`basename $0`

if [ -z "$I_AM_IN_PPPD" ]; then
    export I_AM_IN_PPPD=true
    exec /usr/sbin/pppd pty "$SELF" nodetach local :$IPHOST
fi

expect.pl \
    "ssh -t -e none some.server.example.com" \
    \
    "Enter PIN for 'eToken':" \
    "1234\n" \
    \
    "user@some's password: " \
    "mypassword\n" \
    \
    "$ " \
    "slirp 'special addr $IPNET' ppp\n"