How to use certutil output as Objects within PowerShell

TobyU Powershell

Working with Certification Authorities (CA), native PowerShell commands are not too well established yet to fit all my needs, so I had to think about a solution how I could use the well-known certutil tool and use its output within PowerShell.

That is what I came up with (thanks to Shane’s blogpost):

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function certutilToObjectList($certutilOutput){
 
    $certutilObjectList = @()
    $currentKey = $null
    $currentValue = $null
    $certutilOutput -split [environment]::NewLine | foreach {
 
        switch -regex ($_){
 
            '[Entry|Row] \d+:(.*)' {
                # New Object found
                $currentObject = New-Object psobject
                $currentValue = $null
                continue
            }
 
            '(\s{2})(?[\w\s]+):\s*(?.*)' {
                # Add key / value pair to Object
                if($currentObject){ 
                    if( -not $matches.value){
                        $currentKey = $matches.key.Trim()
                        $currentValue = $null
                    }
                    else {
                        $currentObject | Add-Member -MemberType NoteProperty -Name $($matches.key.Trim()) -Value $($matches.value.trim(@("'",'"','`'))) -Force 
                    }
                }
            }
 
            '^$' {
                # Add Object to ObjectList if Object exists
                if($currentObject){ 
                    if($currentKey -and $currentValue){
                        $currentObject | Add-Member -MemberType NoteProperty -Name $($currentKey) -Value $($currentValue) -Force 
                    }
                    $certutilObjectList += $currentObject 
                    $currentObject = $null
                    $currentKey = $null
                    $currentValue = $null
                }
            }
 
            default {
                # Save Values of Multiline Parameters if a current Key exists
                if($currentObject -and $currentKey){ 
                    $currentValue += $_+"`n"
                }
            }
        }
    }
 
    # Add last Object to ObjectList if necessary
    if($currentKey -and $currentValue){
        $currentObject | Add-Member -MemberType NoteProperty -Name $($currentKey) -Value $($currentValue) -Force 
    }
    $certutilObjectList += $currentObject
 
    return $certutilObjectList
}
 
 
$certutil = "$($env:SystemRoot)\system32\certutil.exe"
$certutilOutput = Invoke-Expression "$certutil -view -restrict disposition==20 -out 'serialnumber,requestid,Issued Common Name,Certificate Expiration Date'"
$certutilObjectList = certutilToObjectList $certutilOutput

This function splits the certutil output into single rows and processes them one by one using regular expressions to figure out what to do with each row. It further creates a list (array) of PowerShell objects to make the output easily usable with PowerShell.

Used regex

1

[Entry|Row] \d+:(.*)

Matches every row starting with the word “Entry” or “Row” followed by at least one digit and finished by a colon “:” and zero one or multiple characters.

1

(\s{2})(?<key>[\w\s]+):\s*(?<value>.*)

Matches all word characters from a-z, A-Z, -0-9, the underscore “_” and whitespaces, after two spaces, until the colon “:” and stores it in the match variable “key”. It further matches every character after the colon and stores it in the match variable “value”.

1

^$

Matches with empty rows which signals the end of the object in this case

Example certutil output

Row 1:
  Serial Number: “MyCertSerialNumber”
  Issued Request ID: 0x8
  Issued Common Name: “MyCertCommonName”
  Certificate Expiration Date: 15.07.2017 12:00

Row 2:
  Serial Number: “MyCertSerialNumber”
  Issued Request ID: 0x9
  Issued Common Name: “MyCertCommonName”
  Certificate Expiration Date: 01.10.2017 13:30

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