Manage SSH config entries with a PowerShell module

#powershell #ssh

I wanted to do this for months now. This afternoon, to procrastinate a slightly more complex task on my vacation bucket list, I finally took the time and created this PowerShell module.

It is quite simple but supports my caters to manage clean configuration files.

!!!DISCLAIMER!!! no warranty - please test the behavior of this script for thoroughly your environment and make regular backups

How to use the module

Once the module is imported

Import-Module .\ManageSshConfig.psm1

it allows

a - to read the list of configured hosts into a HashTable

$hostList = Get-ConfigHostList

b - to add a new entry to this list of hosts

$hostList = Add-ConfigHostInList -HostList $hostList -HostName "dummy" -HostValues @{
    identityfile = "~/.ssh/myprivatekey"
    hostname     = "dummy.somecloud.com"
    user         = "johndoe"
}

c - to update an existing entry in this list of hosts

$hostList = Update-ConfigHostInList -HostList $hostList -HostName "dummy" -HostValues @{
    identityfile = "~/.ssh/myprivatekey"
    hostname     = "dummy.somecloud.com"
    user         = "johndoe"
}

d - to remove an existing entry from this list of hosts

$hostList = Remove-ConfigHostFromList -HostList $hostList -HostName "dummy"

e - and then write this list back to disk

Set-ConfigHostList $hostList

Features

Line breaks

The script should be able to identify the line breaks used in the config file. This could be CR/LF on Windows and definitely are LF on Linux, macOS & alike.

If this sounds unfamiliar to you, check out Scott Hanselman's nice explanation on this topic.

on my Windows machine I forced Visual Studio Code to always safe it with LF line endings - just to be safe when copying this file back and forth between various OS platforms

Keywords

Keywords like IdentityFile or HostName are harmonized when

reading from config file into HashTable
adding or updating entries

according to notation usually seen in documentation like.

JSON

Once list of hosts is loaded, it can also by converted to JSON:

$hostList = Get-ConfigHostList
$hostList | ConvertTo-Json

{
  "dummy": {
    "User": "johndoe",
    "HostName": "dummy.somecloud.com",
    "IdentityFile": "~/.ssh/myprivatekey"
  }
}

This even allows to export SSH config to a JSON file, manage it in that format and then import it back:

$hostList = Get-ConfigHostList
$hostList | ConvertTo-Json -AsHashtable | Set-Content "ssh-config.json"
... do your magic here ...
$hostList = Get-Content "ssh-config.json" | ConvertFrom-Json -AsHashtable
Set-ConfigHostList $hostList

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