Working with Base64 Strings in PowerShell

Base64 is an encoding method that enables transfer of arbitrary binary data through restrictive networks. The most obvious, to me anyway, case of this is email. The SMTP protocol was designed to transfer 7-bit (aka ASCII) characters. If you want to transmit binary data over such a 7-bit transport, you need to encode it some how – and that’s what Base64 does for you. There are loads of other uses for Base64.

For IT Pros, Base 64 can be encoded text that you need to see decoded. I got asked about this the other week in class. You can use .NET it’s current Unicode format using System.Convert and System.Text.Encoding. You can also covert Base 64 encoded strings back into Unicode by using the same .net methods, as you can see in this screen shot:

 

That works, when you can remember the magic incantation(s) but something simpler would be nice, my students mentioned. The obvious answer is to just use PowerShell’s Extensible Type System (ETS) and add a couple of properties onto System.String objects representing encoded/decoded Base 64. This is easy – just create a types.ps1xml file (mine is named My.Types.Ps1xml) that looks like this:

<Types>
<Type>
  <Name>System.String</Name>
    <Members>
      <ScriptProperty>
        <Name>ToBase64String</Name>
          <GetScriptBlock>
             [System.Convert]::ToBase64String([System.Text.Encoding]::Unicode.GetBytes($this))
          </GetScriptBlock>
      </ScriptProperty>
      <ScriptProperty>
        <Name>FromBase64String</Name>
          <GetScriptBlock>
             [System.Text.Encoding]::Unicode.GetString([System.Convert]::FromBase64String($this))
          </GetScriptBlock>
      </ScriptProperty>
    </Members>
  </Type>
</Types>

With that file saved you can add it into your PowerShell environment by using the Update-TypeData cmdlet, specifying your PS1XML file (e.g. Update-TypeData c:\foo\My.Types.PS1XML). Once that’s complete, System.String in nicely extended, as you can see here:

I have added this bit of type-XML to my type extensions file that I load in my $Profile – which means the ability to covert from/to Base64 is, as it were, now baked into PowerShell.

[Later]
Thanks to Bryan Price for catching two typos in this post.

 

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