From: Paul Duncan <pabs@...>
Date: 2002-06-25T02:45:28+09:00
Subject: Re: How to use SSH from the cmd line in Ruby?

* Nikodemus Siivola (tsiivola@cc.hut.fi) wrote:
> 
> On Sat, 22 Jun 2002, Richard wrote:
> 
> > Since an SSH package for Ruby doesn't exist right now, I have been
> > trying to implement an SSH client through Ruby by sending text
> > directly to the command line and retrieving the results. It's not
> > working, though.
> 
> Just guessing, but I believe ssh implementations typically connect
> directly to the tty in use for password/phrase queries for security.

Yup.

openssh-3.3p1/readpass.c:100
  rppflags = (flags & RP_ECHO) ? RPP_ECHO_ON : RPP_ECHO_OFF;
  if (flags & RP_ALLOW_STDIN) {
    if (!isatty(STDIN_FILENO))
      use_askpass = 1;
  } else {
    rppflags |= RPP_REQUIRE_TTY;
    ttyfd = open(_PATH_TTY, O_RDWR);
    if (ttyfd >= 0)
      close(ttyfd);
    else
      use_askpass = 1;
  }


> This means that you need to use tools like expect or open a pty. Another
> option would be to use keypairs that do not require passphrases, or a
> daemon that supplies the passphrase provided it has already been provided
> once.
> 
> The last option is AFAIK the secure & "correct" one. Look into ssh-agent.
> 
> The basic idea is to start the daemon and supply it manually with the
> passphrase, which it stores in memory. After this the daemon supplies the
> information for all future connections.
> 
>  -- Nikodemus

-- 
Paul Duncan <pabs@pablotron.org>        pabs in #gah (OPN IRC)
http://www.pablotron.org/               OpenPGP Key ID: 0x82C29562