sshproxy

What is sshproxy?

sshproxy is used on a gateway to transparently proxy a user SSH connection on the gateway to an internal host via SSH. scp, sftp, rsync, etc. are supported.

sshproxy defines routes which bind an SSH listening address to a pool of destination hosts. It can then choose the first available destination or load-balance the connections with a simple round-robin algorithm.

Because of its design sshproxy is stateless (it is launched as a ForceCommand by sshd). It can be made stateful by using etcd allowing to:

• remember users connections and always connects a user to the same destination while a connection to this destination is alive,

• periodically check if destination hosts are alive.

States stored in etcd can be displayed or modified with the sshproxyctl command.

sshproxy can be configured to monitor SSH sessions and either to save them in files or to send them to the very simple sshproxy-dumpd daemon. Sessions can be replayed with the sshproxy-replay command.

Compilation

Install the Go (version >= 1.22) compiler suite: see http://golang.org/doc/install for details.

Define and export the $GOPATH directory where the source code will be unpacked (e.g. $HOME/go):

$ export GOPATH=$HOME/go
$ mkdir -p $GOPATH/src/github.com/cea-hpc
$ cd $GOPATH/src/github.com/cea-hpc
$ tar xvJf sshproxy-X.Y.Z.tar.xz

Compile everything:

$ make

Installation

Install binaries and manpages:

# make install

sshproxy and sshproxy-dumpd are installed in /usr/sbin, sshproxyctl and sshproxy-replay in /usr/bin.

Optional installation

If you want to use clustershell groups with sshproxy, you have to install libnodeset.so from https://github.com/fdiakh/nodeset-rs

If you don’t, you’ll still be able to use nodesets, but not clustershell groups.

You can check if sshproxy uses libnodeset.so with this command:

$ sshproxyctl show config
[…]
libnodeset.so found
[…]

Configuration

There is a commented configuration file in the config directory.

Configure /etc/sshproxy/sshproxy.yaml to suit your needs.

Modify the SSH daemon configuration /etc/ssh/sshd_config by adding:

ForceCommand /usr/sbin/sshproxy

Migrating to sshproxy 2

Version 2 brings a lot of changes to sshproxy:

1. configuration file:

   • all configuration options can now be set outside of overrides (those are the default values) or inside an override

   • users, groups and routes options have been replaced by the overrides system:

     • old style:

       routes:
         default:
           some_default_options…
         service1:
           source: [an.ip.sshd.listens.to]
           some_sources_options…
       users:
         - alice,bob:
             some_users_options…
       groups:
         - foo,bar:
             some_groups_options…

     • new style:

       some_default_options…
       overrides:
         - match:
             - sources: [an.ip.sshd.listens.to]
           some_sources_options…
         - match:
             - users: [alice,bob]
           some_users_options…
       overrides:
         - match:
             - groups: [foo,bar]
           some_groups_options…

   • the match conditions of the overrides system can be combined. Here is an example meaning "match if (the user is in the group foo and in the group bar) or ((the user is alice or bob) and the user is connected to an.ip.sshd.listens.to)":

     overrides:
       - match:
           - groups: [foo]
             groups: [bar]
           - users: [alice,bob]
             sources: [an.ip.sshd.listens.to]

   • nodesets can now be used for the dest key

   • if libnodeset.so (from https://github.com/fdiakh/nodeset-rs) is found, it allows the use of clustershell groups where nodesets are allowed

   • new option: blocking_command runs a command before starting the ssh connection to the destination. If the command does not return 0, the connection is aborted

2. command line interface:

   • in all the tables, Host and Port columns are now merged into a single Host:Port

   • sshproxyctl get_config has been removed and replaced by sshproxyctl show config

   • sshproxyctl show hosts and sshproxyctl show users -all now display persist info

   • sshproxyctl enable HOST [PORT] has been removed and replaced by sshproxyctl enable -all|-host HOST [-port PORT]

   • sshproxyctl disable HOST [PORT] has been removed and replaced by sshproxyctl disable -all|-host HOST [-port PORT]

   • sshproxyctl forget HOST [PORT] has been removed and replaced by sshproxyctl forget host -all|-host HOST [-port PORT]

   • sshproxyctl error_banner (without any parameter) has been removed and replaced by sshproxyctl forget error_banner

Copying

Copyright © 2015-2025 CEA/DAM/DIF

sshproxy is distributed under the CeCILL-B, a French transposition of the BSD license. See the included files Licence_CeCILL-B_V1-en.txt (English version) and Licence_CeCILL-B_V1-fr.txt (French version) or visit http://www.cecill.info for details.

Authors

Current maintainer:

• Cyril Servant https://github.com/cyrilst <[email protected]>

Original author:

• Arnaud Guignard https://github.com/arno

Contributors:

• Olivier Delhomme https://github.com/od-cea

• François Diakhaté https://github.com/fdiakh

• Romain Fihue https://github.com/fihuer

• Dominique Martinet https://github.com/martinetd

Documentation

See files in the doc directory.