Comments on Roland Schulz: SSH ProxyCommand without netcat

I came across this having the problem of no netcat...

2011-06-03T05:57:39.285+01:00

I came across this having the problem of no netcat on the gateway, but unfortunately it has no /dev/tcp either.

I did nonetheless eventually find a solution! See, there _was_ a copy of netcat on the final target, and I could use that with an extra ssh hop:

ProxyCommand ssh {gw} ssh {host} netcat -w1 {host} 22.

It does end up with an extraneous loopback from the target to itself, but otherwise seems to work.

I updated the post to make it more clear. Yes you ...

2011-03-03T01:31:26.990Z

I updated the post to make it more clear. Yes you can use %h if that is the valid hostname. gw is the gateway you use as intermediary machine. And you need to make sure you use bash with /dev/tcp enabled.

I am sorry to bump up an old post, I am trying you...

2011-03-03T00:34:52.877Z

I am sorry to bump up an old post, I am trying your solution with a slightly different approach, but doesn't seem to work and it's mainly because I don't think I understand the proxy command line correctly.

What's the {gw} string? and is the {host} the same as the %h variable?

And on a second note /dev/tcp directory doesn't exist either on my local or remote machine during an ssh connection.

Is it possible to explain the expression with the exec:
exec 3<>/dev/tcp/{host}/22

My setup looks something like this:

Host proxy
Hostname proxy.server.com
User myuser
DynamicForward localhost:3128

Host *.server.com
ProxyCommand /usr/bin/nc -x localhost:3128 -Pmyseconduser %h %p

In a perfect world, I'd ssh to proxy, then ssh in another console to the dev.server.com, and use proxy to browse the same server on ports 80 and 3000

The problem is that proxy doesn't have netcat installed. so no nc love there.

Any help that allows me to rewrite this trick and adapt it to my context would be appreciated.

Closeing the file descriptor doesn't exit the ...

2009-10-22T23:41:08.053+01:00

Closeing the file descriptor doesn't exit the background cat for me. But your comment made me realized one can just kill the background cat after the connection is finished. Thanks. I updated it in the article.

How about closing the file descriptor #3 after eve...

2009-10-22T19:08:35.244+01:00

How about closing the file descriptor #3 after everything was done? Will this work? --
ProxyCommand ssh {gw} 'exec 3<>/dev/tcp/{host}/22;(cat <&3 & );cat >&3; exec 3>&-;'

Yes, it leaves one cat around. Didn't worry ab...

2009-08-05T17:21:35.480+01:00

Yes, it leaves one cat around. Didn't worry about it. Not sure how one could prevent that.

Not bad the idea, but for me that leaves one idle ...

2009-08-05T16:07:28.233+01:00

Not bad the idea, but for me that leaves one idle cat around after teminating the connection.

That is one great trick, I'll try this one on diff...

2008-10-23T09:28:00.000+01:00

That is one great trick, I'll try this one on different UNIX/Linux systems! Thanks for this hint!