Read the documentation for ProxyCommand directive in the ssh_config manual.

If netcat (or socat or some similar utility) is available in machine C, then it can be done as follows: 

my $ssh = Net::OpenSSH->new($host, 
                            master_opts => [-o "ProxyCommand ssh machi
+neC /usr/bin/nc %h:%p"]);

[download]

Otherwise, if perl (or any other scripting language) is available on machine C, you could write a netcat clone yourself with it.

As a last resort, you can use this (not very efficient) ProxyCommand: 

ProxyCommand ssh machineC ssh -p %p %h sshd -i

[download]
If you want to use password authentication between machine A and machine C, you will have to do it using an auxiliary Net::OpenSSH object.

Post the full details of your setup and I will be able to provide further instructions on how to do it.

update: oh, and of course, you can use ssh to create a tunnel from machine A to B through C if they are not administratively forbidden in machine C... in my experience, something very unlikely.

In reply to Re: Net::OpenSSH and tunnels by salva
in thread Net::OpenSSH and tunnels by vxp

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.