Re: ncat exec or sending a one-shot login string

[Daniel Miller <bonsaiviking () gmail com>]

Spencer,

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Dan

On Mon, Dec 14, 2015 at 7:38 PM, Spencer Robick <srobick97 () gmail com> wrote:

> Can u please take me out of the group
>
>
> On Monday, December 14, 2015, Brian Franklin <brian.is.still () gmail com>
> wrote:
>
> > I tried the subshell+sleep, and it actually works pretty well.  Except
> > after the sleep is over, I get "Ncat: Input/output error."  I'm also using
> > the --no-shutdown option, but it doesn't seem to work the way I need it to.
> >
> > So my command line looks like:
> >
> > $ (echo "login"; sleep 5) | ncat --no-shutdown -C --ssl [server] [port]
> >
> > And the login works successfully, and the data flows back, until
> > (apparently) the sleep ends, and then I get the i/o error.
> >
> > Am I missing something??
> >
> > On Mon, Dec 14, 2015 at 3:53 PM, Daniel Miller <bonsaiviking () gmail com>
> > wrote:
> >
> > > Brian,
> > >
> > > From your description, it sounds like --no-shutdown is the option you
> > > want. This would prevent the need for the extra "-" in the cat command.
> > >
> > > Dan
> > >
> > > P.S. please keep dev () nmap org in the CC line of replies so that other
> > > users can benefit from your experience.
> > >
> > > On Mon, Dec 14, 2015 at 2:12 PM, Brian Franklin <
> > > brian.is.still () gmail com> wrote:
> > >
> > > > Dan,
> > > >
> > > > Thanks for your reply.  I'll try upgrading to 7.00 and see if it helps.
> > > >
> > > > I had seen the changelog, and the 'recv-only' option appeals to me,
> > > > except I'm still required to send out an identification string before the
> > > > data starts to flow.  (So my case isn't strictly a receive-only situation.)
> > > >
> > > > I'll have to try the subshell+sleep.  I had the impression the
> > > > 'disappearance' of stdin was something that the shell was complaining
> > > > about.  I was using 'cat "login" -' so that the '-' was an indefinite input
> > > > from stdin.
> > > >
> > > > You've given me some ideas!
> > > >
> > > > Brian
> > > >
> > > >
> > > >
> > > >
> > > > On Mon, Dec 14, 2015 at 3:03 PM, Daniel Miller <bonsaiviking () gmail com>
> > > > wrote:
> > > >
> > > > > Brian,
> > > > >
> > > > > We've fixed a lot of these socket, pipe, and stdin EOF handling issues
> > > > > in recent versions. Most recently in version 7.00, we added an option that
> > > > > some folks needed for cron scripts, --no-shutdown, which prevents Ncat from
> > > > > closing the network connection when it receives EOF on STDIN. Other
> > > > > relevant options (which may or may not help your particular situation) are:
> > > > >
> > > > > -k or --keep-open, accept multiple connections in listen mode
> > > > > --send-only, only send data, ignoring received; quit on EOF
> > > > > --recv-only, Only receive data, never send anything
> > > > >
> > > > > Finally, sometimes you need to give Ncat some extra time to receive a
> > > > > reply, especially with UDP communication. For example this will fail:
> > > > >
> > > > > echo -ne
> > > > > '\0\x06\x01\0\0\x01\0\0\0\0\0\0\x07version\x04bind\0\0\x10\0\x03' | ncat -u
> > > > > 192.168.1.1 53
> > > > >
> > > > > But this will succeed:
> > > > >
> > > > > (echo -ne
> > > > > '\0\x06\x01\0\0\x01\0\0\0\0\0\0\x07version\x04bind\0\0\x10\0\x03'; sleep 5)
> > > > > | ncat -u 192.168.1.1 53
> > > > >
> > > > > We don't yet have a command option for that, but a subshell+sleep
> > > > > works pretty well.
> > > > >
> > > > > Dan
> > > > >
> > > > > On Sun, Dec 13, 2015 at 9:02 AM, Brian Franklin <
> > > > > brian.is.still () gmail com> wrote:
> > > > >
> > > > > > Hi there!  I'm a big fan of ncat, particularly the ssl support.  Well
> > > > > > done!
> > > > > >
> > > > > > Recently, I'm trying to use it from within cron.  I can't seem to get
> > > > > > it to work.  Basically, I connect as a client and then pass a login string
> > > > > > to a remote server, and then it streams some data to me, which I then pipe
> > > > > > to another process.  I use something like:
> > > > > >
> > > > > > cat "login" - | ncat -C --ssl [server] [port] | [some other script]
> > > > > >
> > > > > > This works perfectly from the command line (it always does...) but
> > > > > > the cron job won't work.  Turning up the verbosity provides some
> > > > > > interesting clues, but I don't know how to interpret most of it.  I've
> > > > > > applied all my standard "tricks" for debugging a cron job, but I'm getting
> > > > > > nowhere.  The closest I've come is that it might be related to my use of
> > > > > > 'cat' and it's reliance on stdin to 'hold' the pipe open?
> > > > > >
> > > > > > If I remove the last pipe, and just collect the ncat output using the
> > > > > > MTA from cron, then it reports a successful connection, but it just seems
> > > > > > to quit after that.
> > > > > >
> > > > > > What I'm trying to achieve is this:
> > > > > >
> > > > > > 1.  Connect to remote server
> > > > > > 2.  Send login string (really just an identity)
> > > > > > 3.  Receive data
> > > > > > 4.  Pipe data to another script for processing
> > > > > >
> > > > > > Sending the login string is a one-shot deal; after that it's all
> > > > > > uni-directional communication and I don't send anything back.  I have no
> > > > > > control over the remote server.
> > > > > >
> > > > > > Using ncat 6.40 on Ubuntu 14.04.
> > > > > >
> > > > > > Can anyone point me in the right direction?
> > > > > >
> > > > > > Thanks,
> > > > > >
> > > > > > Brian
> > > > > >
> > > > > > _______________________________________________
> > > > > > Sent through the dev mailing list
> > > > > > https://nmap.org/mailman/listinfo/dev
> > > > > > Archived at http://seclists.org/nmap-dev/
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