Get-TkExistingCert.ps1

<#
.SYNOPSIS
Retrieves an existing certificate from the current user's certificate store based on the subject name.

.DESCRIPTION
The Get-TkExistingCert function searches for a certificate in the current user's certificate store with the specified subject name.
If the certificate exists, it provides instructions on how to remove the certificate and optionally removes it if confirmed by the user.

.PARAMETER CertName
The subject name of the certificate to search for in the current user's certificate store.

.EXAMPLE
PS C:\> Get-TkExistingCert -CertName "CN=example.com"
Searches for a certificate with the subject name "CN=example.com" in the current user's certificate store.
If found, it provides instructions on how to remove the certificate and optionally removes it if confirmed by the user.

.NOTES
This function uses the certificate store path 'Cert:\CurrentUser\My' to search for the certificate.
The function logs its operations using the Write-AuditLog cmdlet.
#>
function Get-TkExistingCert {
    [CmdletBinding(SupportsShouldProcess = $true, ConfirmImpact = 'High')]
    param (
        [Parameter(Mandatory = $true, HelpMessage = 'The subject name of the certificate to search for in the current user''s certificate store.')]
        [string]$CertName
    )

    if (-not $script:LogString) {
        Write-AuditLog -Start
    }
    else {
        Write-AuditLog -BeginFunction
    }

    $ExistingCert = Get-ChildItem -Path Cert:\CurrentUser\My -ErrorAction SilentlyContinue |
    Where-Object { $_.Subject -eq $CertName } -ErrorAction SilentlyContinue

    if ( $ExistingCert) {
        $VerbosePreference = 'Continue'
        Write-AuditLog "Certificate with subject '$CertName' already exists in the certificate store."
        Write-AuditLog 'You can remove the old certificate if no longer needed with the following commands:'
        Write-AuditLog '1. Verify if more than one cert already exists:'
        Write-AuditLog "Get-ChildItem -Path Cert:\CurrentUser\My | Where-Object { `$_.Subject -eq '$CertName' }"
        Write-AuditLog '2. If you are comfortable removing the old certificate, and any duplicates, run the following command:'
        Write-AuditLog "Get-ChildItem -Path Cert:\CurrentUser\My | Where-Object { `$_.Subject -eq '$CertName' } | Remove-Item"
        Write-AuditLog 'If you would like to remove the certificate, confirm the operation when prompted.'
        $shouldProcessOperation = 'Remove-Item'
        $shouldProcessTarget = "Certificate with subject '$CertName' with thumbprint $($ExistingCert.Thumbprint)"
        if ($PSCmdlet.ShouldProcess($shouldProcessTarget, $shouldProcessOperation)) {
            Get-ChildItem -Path Cert:\CurrentUser\My | Where-Object { $_.Subject -eq $CertName } -ErrorAction Stop | Remove-Item
            Write-AuditLog "Certificate with subject '$CertName' removed."
        }
        else {
            Write-AuditLog "Certificate with subject '$CertName' not removed."
            throw "Certificate with subject '$CertName' was not removed by user."
        }
        $VerbosePreference = 'SilentlyContinue'
    }
    else {
        Write-AuditLog "Certificate with subject '$CertName' does not exist in the certificate store. Continuing..."
    }

    Write-AuditLog -EndFunction
}