I have a SOCKS5 proxy set up through PuTTY with port 7777 configured as a dynamic port. I can use firefox/filezilla/etc by configuring them to use a SOCKS proxy with localhost and port 7777. But I can't figure out how to ssh (through Cygwin) to a remote server by using the dynamic port. Is this possible?

I've tried using ProxyCommand via the following method.

  1. Create ~/.ssh/config with the following line:

    ProxyCommand /usr/bin/nc -X connect -x %h %p
  2. Run ssh -p22 user@remotehost

The message I get is ssh_exchange_identification: Connection closed by remote host

  • 1
    To make a program whuch does not support SOCKS go through SOCKS, you can use a so-called proxifer; see en.wikipedia.org/wiki/Comparison_of_proxifiers . In particular, I recommand my open source tun2socks proxifer ( code.google.com/p/badvpn/wiki/tun2socks ). – Ambroz Bizjak Jul 26 '12 at 15:34
  • Thanks for the comment Ambroz. I need it to work in cygwin, and I see from the wikipedia page on proxifiers that all of the ones it mentions are either not implemented in cygwin or not applicable. Is there a way to get a proxifier to work in cygwin? – Rusty Lemur Jul 26 '12 at 15:41
  • you don't need it to specifically support Cygwin. Cygwin programs are in the end just Windows programs, but with a POSIX interface implemented as a library. If a proxifier works on Windows, it should be able to proxify Cygwin programs just fine. – Ambroz Bizjak Jul 26 '12 at 16:50

You are using 'connect' for HTTPS as your proxy version, this is from man nc:

-X proxy_version Requests that nc should use the specified protocol when talking to the proxy server. Supported protocols are ''4'' (SOCKS v.4), ''5'' (SOCKS v.5) and 'connect' (HTTPS proxy). If the protocol is not specified, SOCKS version 5 is used.

So you should use the following to use SOCKS 5:

ProxyCommand /usr/bin/nc -X 5 -x %h %p

Or simply:

ProxyCommand /usr/bin/nc -x %h %p

I hope it helps.

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  • Thanks Saman, that worked! Also, thanks for the explanation, it helps. – Rusty Lemur Jul 26 '12 at 18:19
  • The ProxyCommand must be the first line of your ~/.ssh/config', or else nested inside a specify Host` section. Not really sure why. It doesn't work if it's the last line in the ~/.ssh/config – Aaron McDaid Jul 14 '16 at 19:21
  • @AaronMcDaid: From man ssh_config: "For each parameter, the first obtained value will be used." Therefore... global settings need to be before any Host sections. The last line of ~/.ssh/config is part of the final Host section. – mpb Jun 26 '17 at 2:41
  • Worth mentioning is that netcat is in /bin/nc on Debian and Ubuntu. – Per Lundberg May 18 '18 at 10:25
ssh -o ProxyCommand='nc --proxy-type socks4 --proxy %h %p' user@host

fc19 x86_64, Ncat: Version 6.25

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  • just curious - why proxy-type socks4? – suspectus Oct 19 '13 at 9:57
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    Can you add a little more explanation to this to say why it's the solution. – ChrisF Oct 19 '13 at 10:48
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    @ChrisF it is the same as accepted solution, but it is one-liner! No need to modify any config file. – j123b567 Dec 2 '15 at 9:39
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    This is the nmap ncat program (comes via apt install nmap on APT systems like Ubuntu and Debian), which is different from netcat (be it netcat-openbsd or Hobbit's netcat-traditional). – Adam Katz Nov 5 '16 at 0:07
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    @suspectus related to @Adam Katz comment, the proxy-type is socks4 because the nmap ncat program didn't support sock5 until more recently. Indeed, this is an issue even now (Nov 2017), as RHEL 7/Centos 7 switched to the nmap package but used an older build that does not support socks5 – Randall Nov 27 '17 at 16:09

tsocks (http://tsocks.sourceforge.net/) is a nice wrapper that uses LD_PRELOAD to make any program use SOCKS proxy transparently:

tsocks ssh example.com

Just works, remember to configure SOCKS proxy IP in /etc/tsocks.conf

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  • it's too complex to have a configuration file – Jiang YD Mar 14 '17 at 3:10

This following command will do, to just use nc:

ssh examplehost.com -o "ProxyCommand=nc --proxy localhost:7000 %h %p"

Default is HTTP proxy, there is an HTTP proxy running on port 7000.

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