[GLLUG] Netcat Bash prompt

Daniel Griswold daniel at griswoldcomputing.com
Thu Dec 4 17:07:54 EST 2014


 

"ssh $jumpserver ssh $targetserver /bin/bash -i" will give the client an
interactive session on the target server 

if using ssh keys/agents to not require interactive authentication, you
can do: 

echo "command" | ssh $jumpserver ssh $targetserver /bin/bash 

which will run the command on the remote host and return when the
process on the remote host terminates. 

I'm confused as to whether the connections are initiating to terminating
at the linux servers. The Windows implementation may not support the
above. 

--Daniel 

On 2014-12-04 16:22, Michael P. Flaga wrote: 

> Yes, I can create a tunnel over, but not forwarded onto another IP, rather need a bash prompt. So that the telneting program can call bash commands at the remote linux box. 
> 
> The goal is to not simply tunnel the telnet. But rather translate it. Noting that telnetd is gone from the remote linux box. 
> 
> Netcat is there, so "-t" will answer TELNET negotiation in place of telnetd. 
> 
> Michael P. Flaga, michael at flaga.net 
> 
> FROM: Jason L. Froebe [mailto:jason.froebe at gmail.com] 
> SENT: Thursday, December 04, 2014 4:12 PM
> TO: Michael Flaga
> CC: GLLUG
> SUBJECT: Re: [GLLUG] Netcat Bash prompt 
> 
> On the windows box, use putty to create a ssh tunnel to your Linux box. This way nothing is transferred unencrypted over the network. 
> 
> Jason 
> 
> On Dec 4, 2014 4:02 PM, "Michael P. Flaga" <michael at flaga.net> wrote: 
> 
> I have closed source programs that telnet on windows boxes. Where I am constrained to Linux Jump servers. That now only have SSH. The Telnet is GONE on the jump servers. The closed source programs once connected (formerly via telnet) to the jump servers then know who to issue the commands to ssh into the remote targets. 
> 
> I need a way to translate Telnet to SSH on the jump servers. 
> 
> The netcat on the jump servers do not have the -e option, so I cannot run nc in telnet mode into /bin/bash. 
> 
> I have found 
> 
> mkfifo pipe_name_in 
> 
> mkfifo pipe_name_out 
> 
> nc -l 5555 < pipe_name_out | /bin/bash > pipe_name_in 
> 
> which kind of works. However, the Standard Error does not go down the pipe. 
> 
> So I don't get any echo or prompts, only the response. 
> 
> nc -l 5555 < pipe_name_out | /bin/bash 2> pipe_name_in 
> 
> does get the some of the prompts but then no responses. 
> 
> nc -l 5555 < pipe_name_out | /bin/bash 2>&1 pipe_name_in 
> 
> fails to allow connections. 
> 
> Any suggestions or solutions? 
> 
> Michael P. Flaga, michael at flaga.net 
> 
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