30 December 2020

How to cleanup expired certificates from a Microsoft CA with PowerShell and Shrink the DB



This a shameless copy of the original post by André Gibel over at https://www.gibel.net/

The reason why I copied it is because there is very little info on this subject and even though the post is from 2014, it still applies today.

Regularly (depending on the number of issued certificates) you have to perform a clean-up of expired certificates from your CA (Certification Authority) DB and then shrink the DB to get rid of the “white space”.

You have to perform the following 3 steps in order:
1. Make a backup of your CA DB (protected with a password) to another Server / medium





- this backup also "removes" the maybe hundres of db log files (each of the has a size of 1 MB) – in my case 828



2.      Clean-up all expired certificates from all 4 categories  with my PowerShell Script


- in a first step it's the best to run the script in a "view only" modus to see which certificates would be deleted
- the script and all the details are explained 
below.

3.      Shrink your CA database to get rid of the “whitespace”

- for this you use the esentutl tool with the “/d” (= defragmentation) option

Before executing the esentutl command stop the AD Certificate service and disable it




- run the following command with the path to the .edb DB file



- at the end the DB - file is more than 100 MB smaller than before, depending on the size your database is.



- at this point you have to enable and start the CA Service again

Here I explain the PowerShell script in detail (the script is used in step 2)

The Microsoft Enterprise CA I’m responsible for is running on a Microsoft Windows Server 2008 Enterprise Server

- with PowerShell 2.0 installed
- no 3rd party PS modules are used
- the certutil.exe is used by the PowerShell (PS) script
- the PS script I created is "Cleanup_MSPKI_Cert_v1.1.ps1" and contains 3 functions

On this CA Server in the C:\ root drive I create a folder “_scripts “ (I don’t use PS remoting) and copy my PowerShell script “Cleanup_MSPKI_Cert_v1.1.ps1” into this folder


Per default the functions "Remove-ExpiredCertFromDB" writes the temporary files to a subfolder within C:\_scripts\PKICleanupLog.

You can change this default folder path with the parameter  “CleanedFolderLogPath”


The 3 functions I have implemented are:

A.) Get-PublishedCATemplate
B.) Get-IssuedCert
C.) Remove-ExpiredCertFromDB

A.) Get-PublishedCATemplate


When you run this function without a parameter, it displays all Templates from the "Certificate Templates" folder with it's OID. This OID is used by the other to functions to display or delete certificates issued with this certain template. In the following picture you see the corresponding templates from the PKI Snap In



function Get-PublishedCATemplate{             

    [CmdletBinding()]

    Param (

        [parameter()]

        [string]$filter   

    )      

    $FilterLen = ("msPKI-Cert-Template-OID =").length+3   

    $AllPublishedTemplates = Invoke-Expression "certutil.exe –catemplates –v | select-string msPKI-Cert-Template-OID"     

    $AllPublishedTemplates | foreach{       

        $tmp= ($_.line).Substring($FilterLen)       

        $splitarr = $tmp.split(" ",2)     

        $obj = New-Object PSObject                                     

        Add-Member -Input $obj -Name "name" -MemberType Noteproperty -Value $Splitarr[1].trim()

        Add-Member -Input $obj -Name "oid" -MemberType Noteproperty -Value $Splitarr[0].trim()              

        if ($PSBoundParameters["filter"]){  

            if ($Splitarr[1].trim() -match $filter){

                write-output $obj             

            }

        }

        else{

            write-output $obj             

        }

    }              

}

Below I run the script with the -filter parameter and so I only get templates with “SCCM” in their name



I assign the oid of ONE template (=> change filter that you get only one result)  to the variable WSTemplate

$WSTemplate = (Get-PublishedCATemplate -filter workstation).oid


B.) Get-IssuedCert

With this function  you can list the certificates  issued from all templates or a certain template (specified with it’s oid = $CertTemplate variable)  which are issued beginning at a certain date.

 function Get-IssuedCert{

  [CmdletBinding()]

  Param (

    [ValidatePattern('^([0-9\.\s])+$')]

    [string]$CertTemplate,

    [ValidatePattern('^\d\d[\./]{1}\d\d[\./]{1}\d\d\d\d$')]

    [string]$Date

  )

  if ($PSBoundParameters["CertTemplate"]){   

    Invoke-Expression "certutil.exe -view -restrict 'certificate template=$CertTemplate,disposition=20,notbefore>=$Date' -out 'Request.RequestID,Request.RequesterName,NotBefore,NotAfter,Request.Disposition'"       

  }

  else {

    # displays Certificates issued with any custom template   

    Invoke-Expression "certutil.exe -view -restrict 'disposition=20,notbefore>=$Date' -out 'Request.RequestID,Request.RequesterName,NotBefore,NotAfter,Request.Disposition'"             

  }

}

 

The following example lists all  29 certificates (from ALL templates) issued from 18 December 2014 and later …. (with this version it’s not possible to select a time range / only a “start-date”)

Get-IssuedCert  -Date 18.12.2014


The following example lists ONLY the 3 certificates which are issued with the Template $WSTemplate (OID of  “…- Workstation – Authentication Certificate”) beginning December 18. 2014

$WSTemplate = (Get-PublishedCATemplate -filter workstation).oid
Get-IssuedCert -CertTemplate $WSTemplate -Date 18.12.2014



C.) Remove-ExpiredCertFromDB

This is an advanced function and all available parameters are displayed with the get-help command

- the expired certificates to view (1st step) and then delete are in one of 4 folders


- I select this “folder” with the -state parameter


- the script creates a log file (also needed for further parsing) in a separate folder


These folders are created automatically if they don’t exist yet.
In a first step always run the cmdlet without the "-delete" parameter so nothing is really deleted.
I also recommend the ISE instead of the shell.
And I also always run this cmdlet with the “-verbose” parameter.

The following example displays all issued (and expired) certificates till 18.12.2014  --- they are not really deleted yet.

Remove-ExpiredCertFromDB -State issued -Date 18.12.2014  -Verbose 


Without the -delete switch parameter the log file has "-ViewOnly" in it’s name

Below is the output from the example above / 396 entries “would be” deleted from the “issued folder” (or category) if you run the cmdlet with “-delete”


The following example lists / deletes  certificates from a certain (workstation authentication) template expired up to 18 december 2014

$WSTemplate = (Get-PublishedCATemplate -filter workstation).oid
Remove-ExpiredCertFromDB -State issued -CertTemplate $WSTemplate -Date 18.12.2014 -Verbose


With the added-delete switch parameter you really delete the entries
T
his step can take some time if there are a lot of entries.

$WSTemplate = (Get-PublishedCATemplate -filter workstation).oid
Remove-ExpiredCertFromDB -State issued -CertTemplate $WSTemplate -Date 18.12.2014 -Verbose -delete


The output at the end (and the log file)


When  you run the same cmdlet again, you see that there aren’t any entries to delete from the DB



The latest (full) version of this script with the 3 functions you can download from the Microsoft Script Gallery: go to download

DirectDownload link

Since TechNet is retired and will be taken offline any time soon a backup can be downloaded here:

Cleanup_MSPKI_Cert_v1.2.ps1







7 comments:

  1. you left out how to run these commands? i know you know how to do this stuff, but i'm running the powershell and nothing happens. how do i actually run these functions. can you include the steps to actually run the powershell functions

    ReplyDelete
  2. You have to dot source the script to run the functions in the script, like so:
    ". .\Cleanup_MSPKI_Cert_v1.1.ps1"
    And the you can run one of the 3 functions in the script, like so:
    "Get-IssuedCert -Date 18.12.2021"

    ReplyDelete
  3. A little more information on the dot sourcing. Took me forever to figure it out!

    FIrst, you can only run the script from ISE IF you run ISE as Administrator. Better to just launch PowerShell As Administrator.
    2nd, CD to the folder where your script is. Mine was C:\Scripts so I had to modify the script to change it from _scripts.
    3rd, to dot source the script, enter it like this: . .\Cleanup_MSPKI_Cert_v1.2.ps1. If you just type clean & press tab after you put in the 1st dot, it'll fill in the script name for you. Press Enter to load the script.
    4th, enter the function that you want to use. I only used the Get-IssuedCert & Remove-ExpiredCertFromDB functions. If you're in the US, you have to enter the dates using US date format (MM/DD/YYYY), not the dotted European format shown in the examples above

    ReplyDelete
  4. I have trouble running the script. Trying to call the function Get-PublishedCATemplate or just dot sourcing the script generates this error:

    foreach : You cannot call a method on a null-valued expression.
    At C:\_scripts\Cleanup_MSPKI_Cert_v1.2.ps1:41 char:30
    + $AllPublishedTemplates | foreach{
    + ~~~~~~~~
    + CategoryInfo : InvalidOperation: (:) [ForEach-Object], RuntimeException
    + FullyQualifiedErrorId : InvokeMethodOnNull,Microsoft.PowerShell.Commands.ForEachObjectCommand

    I have tried looking at the different variables contents but not yet able to figure out why it fails. Tried ISE as admin and a powershell windows as admin.
    It looks like $PSBoundParameters returns NULL.

    ReplyDelete
    Replies
    1. Let me clear that up. I meant $PSBoundParameters contains NULL (when fed a parameter with -filter).
      But looking more into it, it rather seams to fail after outputting the first template in the .

      Delete
    2. Update: Some old templates do not have the template name at the end of the OID. This fails the script when inserting an empty field into the $obj. Using display name could be a solution.

      Delete