ssh hang on wrong port - is it a bug ?

[Gary E. Miller]

Yo Darren!

On Tue, 18 Jun 2002, Darren Tucker wrote:

> That's because you know the FTP protocol.  What I was getting that is to
> a user who doesn't, the telnet session "hangs" (ie no "login:" prompt).
> Telnet didn't disconnect just because it didn't find a telnet server.

If telnet gets an RST on connect  (a subset of not finding a server)
then it does disconnect.

If telnet does not get a SYN-ACK in a short while (a subset of not
finding a server) then it does disconnect.  This is usually about 2 minutes.

> OK, let's see you do an active-mode file transfer using only telnet :-)

Trivial, if you really know FTP

In session one:

hobbes:/usr/local/netsaint/var# telnet ratbert ftp
Trying 216.228.186.178...
Connected to ratbert.rellim.com.
Escape character is '^]'.
USER ge220 ProFTPD 1.2.4 Server (ProFTPD Default Installation) [ratbert.rellim.com]
m
331 Password required for gem.
PASS ********
230 User gem logged in.
PASV
227 Entering Passive Mode (216,228,186,178,222,152).
RETR /etc/issue
150 Opening ASCII mode data connection for /etc/issue (24 bytes).
226 Transfer complete.


In session 2:
hobbes:/usr/local/src/OpenOffice# telnet ratbert 56984
Trying 216.228.186.178...
Connected to ratbert.rellim.com.
Escape character is '^]'.

Welcome to \s \r (\l)

Connection closed by foreign host.


> My original point? ssh's behaviour is consistent with clients of other
> protocols.

Agreed.

> FWIW, I don't think it's worth protecting a user who deliberately
> misconfigures ssh from having to hit CTRL-C if it means providing
> another failure mode for a slow but otherwise valid connection.

Agreed.

RGDS
GARY
---------------------------------------------------------------------------
Gary E. Miller Rellim 20340 Empire Blvd, Suite E-3, Bend, OR 97701
	gem at rellim.com  Tel:+1(541)382-8588 Fax: +1(541)382-8676