SSH Config

Author

Ken Kundert

Version

2.0.3

Released

2020-04-23

Introduction

SSH Config generates an SSH config file adapted to the network you are currently using. In this way, you always use the fastest paths available for your SSH related activities (sshfs, email, vnc, mercurial, etc.). You can also easily reconfigure SSH to make use of proxies as needed or select certain servers or ports based on your location or restrictions with the network.

The following situations are supported:

  1. You may give the mac address or addresses for your router or routers and your network will automatically be recognized.

  2. You can configure which hostname or IP address is used for a particular host depending on which network you are on. In this way you always use the fastest connection available for each host.

  3. You can specify that certain hosts are hidden behind other hosts, so that a SSH proxy should be used to access them.

  4. You can specify port forwarding information for each host. Then, two SSH configurations will be created for those hosts, one that includes port forwarding and one that does not. That way, once the port forwards are established, you can open additional shells on that host without SSH trying to create conflicting port forwards.

  5. You can enter multiple hostnames or IP addresses and give their locations. Then, if you specify your location, the closest server will be used automatically.

  6. You can specify proxy configurations and specify that one should be used for all hosts not on your current network.

  7. You can specify port restrictions and have SSH work around them if possible (if your server supports alternative ports).

  8. You can configure a default location, proxy, or set of port restrictions for each of your known networks.

  9. Once host names are defined, they do not change even though you are using different configurations (different networks, locations, proxies, and port restrictions). In this way you can hard code your host names in applications such as Mercurial or Git, and they automatically adapt to your existing network.

  10. The entire application, including the configuration files, are Python code, so you have considerable freedom to change the configuration based on things like the name of the machine or the user when generating the SSH config file.

Trivial Configuration

The hosts that you would like to connect to are described in the hosts.conf file. A very simple hosts.conf file would look like this:

from sshconfig import HostEntry

class Zeebra(HostEntry):
    user = 'herbie'
    hostname = 'zeebra.he.net'

Hosts are described by directly subclassing HostEntry. Attributes are added that are generally converted to fields in the SSH config file.

The contents of ~/.ssh/config are replaced when you run:

sshconfig

The above hosts.conf file is converted into the following SSH config file:

# SSH Configuration for unknown network
# Generated at 1:04 PM on 22 July 2014.

#
# HOSTS
#

host zeebra
    user herbie
    hostname zeebra.he.net
    forwardAgent no

The transformation between a host entry in the hosts.conf file and the SSH config file could be affected by the network you are on and any command line options that are specified to sshconfig, but in this case it is not. Notice that the class name is converted to lower case when creating the hostname.

In most cases, adding an attribute to the definition of your host simply results in that attribute being added the the SSH configuration, so:

class Zeebra(HostEntry):
    user = 'herbie'
    hostname = 'zeebra.he.net'
    port = 22022

becomes:

host zeebra
    user herbie
    hostname zeebra.he.net
    port 22022
    forwardAgent no

Installation Requirements

You can download and install the latest stable version of the code from PyPI using:

pip3 install --user sshconfig

You can find the latest development version of the source code on Github.

Requires in Python3.6 or later.

Issues

Please ask questions or report problems on Github Issues.