Dailydave mailing list archives

Re: Sending remote procedure calls through e-mail (RPC-Mail)


From: David Maynor <dmaynor () gmail com>
Date: Tue, 19 Oct 2004 22:47:56 -0400

I read this email 3 times hoping that I missed the security part of
your idea. Do you really want to be able to email rpc requests? You
are building an awesome avenue to bypass current security tools like
IPS. You can't really rely on the obscurity of the account name, it
would not take long for somebody to find it.


On Tue, 19 Oct 2004 22:27:38 -0400, Abe Usher
<securitylist () sharp-ideas net> wrote:
Have you ever had the need to remotely send a command to a system, but
you could not access it directly via ssh or telnet because the firewall
is blocking all inbound connections?

The practice of portknocking <http://www.portknocking.org/> provides an
interesting network authentication mechanism for establishing a
connection to a networked computer that has no open ports (as advertised
on portknocking.org).

While I find portknocking ingenious, it is somewhat cumbersome and
overly complex for most users. I propose an alternative - send remote
procedure calls via e-mail. I've coded an application that fits the
bill: RPC-Mail.

The premise of RPC-Mail is simple:
(1) Construct an e-mail message that has a command that you want one of
your remote PCs to execute.
(2) Send the e-mail to a special account that is only used by RPC-Mail.
(3) Have the remote PC set up with a scheduled task or cron job to
periodically execute the application RPC-Mail.py.
(4) When RPC-Mail.py executes, it parses all of the subject lines and
message bodies of e-mail messages that it finds. If the message body
contains a special passphrase, RPC-Mail executes the subject line as a
command, and returns standard output as an e-mail message.

For more information check out my full write up on:
http://www.sharp-ideas.net/

Cheers,
Abe Usher, CISSP

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