json-to-ssh_config

A simple JSON to ssh_config file generator. The basic usage model is that you
stick all the JSON files into a certain folder (the default value is
~/.ssh/confs/, overrideable via the -s parameter), which then in turn get
loaded/validated via Python’s json.load(), and translated to
ssh_config(5) file format.

There are some assumptions that the script makes:

• All JSON files are in the same folder
• All JSON files end with a .conf suffix
• All JSON files get {displayed,written} alphabetically, except for global.conf,
  which is always last

There are two basic syntax models that are supported:

{
    "Hosts":
    [{
        "Host": "aliasname",
        "HostName": "fqdnname",
        "Port": 12345
    }]
}

Which results in:

$ ./gensshconf.py -s .
# Content from ./demo1.conf
Host aliasname
  HostName fqdnname
  Port 12345

And:

{
    "Options":
    {
        "IdentityFile": "pathtoidentityfile",
        "Port": 12345
    },
    "Hosts":
    [{
        "Host": "aliasname1",
        "HostName": "fqdnname1"
    },
    {
        "Host": "aliasname2",
        "HostName": "fqdnname2",
        "Port": 23456
    }]
}

Which results in:

$ ./gensshconf.py -s .
# Content from ./demo2.conf
Host aliasname1
  HostName fqdnname1
  IdentityFile pathtoidentityfile
  Port 12345
Host aliasname2
  HostName fqdnname2
  Port 23456
  IdentityFile pathtoidentityfile

The global.conf file is a special case, its intended usage is to contain the
Host * settings that apply to all hosts:

{
    "Hosts":
    [{
        "Host": "*",
        "ControlMaster": "auto",
        "ControlPath": "somepath",
        "ForwardAgent": "no",
        "IdentityFile": "somefile",
        "IdentitiesOnly": "yes",
        "Protocol": 2,
        "User": "username",
        "VisualHostKey": "yes"
    }]
}

Which results in:

$ ./gensshconf.py -s .
# Content from ./global.conf
Host *
  ControlMaster auto
  ControlPath somepath
  ForwardAgent no
  IdentityFile somefile
  IdentitiesOnly yes
  Protocol 2
  User username
  VisualHostKey yes

Note that there are some aspects of ssh_config(5) which are not supported
directly, such as overriding a set of hosts via wildcards (*.example.com).
That could be hacked around via a combination of some smart file naming and
existing syntax.

There are two supported output modes, screen and file, controlled via the
-o parameter. The default value is screen. When used with the -o file
parameter, the default output file is outfile-example in the script
directory. This can be overridden via the -f parameter:

$ ./gensshconf.py -o file -f ~/.ssh/config

This is still a fairly rudimentary implementation, but it seems to work
properly for me. YMMV disclaimer is implied, as always. :)