Perl SSH connection to execute telnet - perl

Question

I tried the following to access a router via a central admin server as "ssh hop" server
#!/usr/bin/perl -X
use strict;
use Net::OpenSSH;
use Net::Telnet;
my $lhost = "linuxserver";
my $luser = "linuxuser";
my $lpass = "linuxpassword";
my $chost = "routername";
my $cpass = "Routerpassword";
my $prompt = '/(?:Password: |[>])/m';
my #commands = ("show users\r");
my $ssh = Net::OpenSSH->new($lhost,
'user' => $luser,
'password' => $lpass,
'master_opts' => [ '-t' ],
#'async' => 1 # if enabled then password cannot be set here
);
my ($pty, $err, $pid) = $ssh->open2pty("telnet $chost");
my $t = new Net::Telnet(
-telnetmode => 0,
-fhopen => $pty,
-prompt => $prompt,
-cmd_remove_mode => 1,
-output_record_separator => "\r",
#-dump_log => "debug.log",
);
my $end = 0;
while (!$end) {
my ($pre, $post) = $t->waitfor($prompt);
if ($post =~ /Password: /m) {
# send password
$t->print("$cpass");
}
elsif ($post =~ /[>#]/ && #commands) {
my $cmd = shift(#commands);
if ($cmd !~ /[\r\n]/) {
$t->print($cmd);
}
else {
print $t->cmd($cmd);
}
}
else {
$end = 1;
$t->cmd("exit");
}
}
#close $pty;
$t->close();
Unfortunately I always get the following error:
read error: Input/output error at test.pl line 71
Can somebody help me please or is there a better solution only to test if a telnet connection via the "hop" server is possible or not?
The connection looks like:
workstation --ssh-> server --telnet-> router
Thanks in advance.

Answer 1

I think best option is to make an SSH-tunnel to your admin server and use it for telnetting to the router.

Answer 2

Getting Net::Telnet to work over Net::OpenSSH sometimes is not as easy as it should be and it requires some experimentation to get to the right combination of flags and calls that make it work.
For instance, instead of telneting to the target host, use netcat to open a raw connection (or Net::OpenSSH support for TCP forwarding if tunnels are allowed on the proxy).
Expect + Net::OpenSSH may be a better option.