functions/Set-DbaSpn.ps1

function Set-DbaSpn {
    <#
    .SYNOPSIS
        Sets an SPN for a given service account in active directory (and also enables delegation to the same SPN by default)
 
    .DESCRIPTION
        This function will connect to Active Directory and search for an account. If the account is found, it will attempt to add an SPN. Once the SPN is added, the function will also set delegation to that service, unless -NoDelegation is specified. In order to run this function, the credential you provide must have write access to Active Directory.
 
        Note: This function supports -WhatIf
 
    .PARAMETER SPN
        The SPN you want to add
 
    .PARAMETER ServiceAccount
        The account you want the SPN added to
 
    .PARAMETER Credential
        The credential you want to use to connect to Active Directory to make the changes
 
    .PARAMETER NoDelegation
        Skips setting the delegation
 
    .PARAMETER EnableException
        By default, when something goes wrong we try to catch it, interpret it and give you a friendly warning message.
        This avoids overwhelming you with "sea of red" exceptions, but is inconvenient because it basically disables advanced scripting.
        Using this switch turns this "nice by default" feature off and enables you to catch exceptions with your own try/catch.
 
    .PARAMETER Confirm
        Turns confirmations before changes on or off
 
    .PARAMETER WhatIf
        Shows what would happen if the command was executed
 
    .NOTES
        Tags: SPN
        Author: Drew Furgiuele (@pittfurg), http://www.port1433.com
 
        Website: https://dbatools.io
        Copyright: (c) 2018 by dbatools, licensed under MIT
        License: MIT https://opensource.org/licenses/MIT
 
    .LINK
        https://dbatools.io/Set-DbaSpn
 
    .EXAMPLE
        PS C:\> Set-DbaSpn -SPN MSSQLSvc/SQLSERVERA.domain.something -ServiceAccount domain\account
        PS C:\> Set-DbaSpn -SPN MSSQLSvc/SQLSERVERA.domain.something -ServiceAccount domain\account -EnableException
 
        Connects to Active Directory and adds a provided SPN to the given account.
        Connects to Active Directory and adds a provided SPN to the given account, suppressing all error messages and throw exceptions that can be caught instead
 
    .EXAMPLE
        PS C:\> Set-DbaSpn -SPN MSSQLSvc/SQLSERVERA.domain.something -ServiceAccount domain\account -Credential ad\sqldba
 
        Connects to Active Directory and adds a provided SPN to the given account. Uses alternative account to connect to AD.
 
    .EXAMPLE
        PS C:\> Set-DbaSpn -SPN MSSQLSvc/SQLSERVERA.domain.something -ServiceAccount domain\account -NoDelegation
 
        Connects to Active Directory and adds a provided SPN to the given account, without the delegation.
 
    .EXAMPLE
        PS C:\> Test-DbaSpn -ComputerName sql2016 | Where-Object { $_.isSet -eq $false } | Set-DbaSpn
 
        Sets all missing SPNs for sql2016
 
    .EXAMPLE
        PS C:\> Test-DbaSpn -ComputerName sql2016 | Where-Object { $_.isSet -eq $false } | Set-DbaSpn -WhatIf
 
        Displays what would happen trying to set all missing SPNs for sql2016
 
    #>

    [cmdletbinding(SupportsShouldProcess, DefaultParameterSetName = "Default")]
    param (
        [Parameter(Mandatory, ValueFromPipelineByPropertyName)]
        [Alias("RequiredSPN")]
        [string]$SPN,
        [Parameter(Mandatory, ValueFromPipelineByPropertyName)]
        [Alias("InstanceServiceAccount", "AccountName")]
        [string]$ServiceAccount,
        [Parameter(ValueFromPipelineByPropertyName)]
        [PSCredential]$Credential,
        [switch]$NoDelegation,
        [switch]$EnableException
    )

    process {
        #did we find the server account?
        Write-Message -Message "Looking for account $ServiceAccount..." -Level Verbose
        $searchfor = 'User'
        if ($ServiceAccount.EndsWith('$')) {
            $searchfor = 'Computer'
        }
        try {
            $Result = Get-DbaADObject -ADObject $ServiceAccount -Type $searchfor -Credential $Credential -EnableException
        } catch {
            Stop-Function -Message "AD lookup failure. This may be because the domain cannot be resolved for the SQL Server service account ($ServiceAccount). $($_.Exception.Message)" -EnableException $EnableException -InnerErrorRecord $_ -Target $ServiceAccount
        }
        if ($Result.Count -gt 0) {
            try {
                $adentry = $Result.GetUnderlyingObject()
            } catch {
                Stop-Function -Message "The SQL Service account ($ServiceAccount) has been found, but you don't have enough permission to inspect its properties $($_.Exception.Message)" -EnableException $EnableException -InnerErrorRecord $_ -Target $ServiceAccount
            }
        } else {
            Stop-Function -Message "The SQL Service account ($ServiceAccount) has not been found" -EnableException $EnableException -Target $ServiceAccount
        }
        # Cool! Add an SPN
        $delegate = $true
        if ($PSCmdlet.ShouldProcess("$spn", "Adding SPN to service account")) {
            try {
                $null = $adentry.Properties['serviceprincipalname'].Add($spn)
                $status = "Successfully added SPN"
                $adentry.CommitChanges()
                Write-Message -Message "Added SPN $spn to $ServiceAccount" -Level Verbose
                $set = $true
            } catch {
                Write-Message -Message "Could not add SPN. $($_.Exception.Message)" -Level Warning -EnableException $EnableException.ToBool() -ErrorRecord $_ -Target $ServiceAccount
                $set = $false
                $status = "Failed to add SPN"
                $delegate = $false
            }

            [pscustomobject]@{
                Name           = $spn
                ServiceAccount = $ServiceAccount
                Property       = "servicePrincipalName"
                IsSet          = $set
                Notes          = $status
            }
        }

        #if we have the SPN set, we can add the delegation
        if ($delegate) {
            # but only if $NoDelegation is not passed
            if (!$NoDelegation) {
                if ($PSCmdlet.ShouldProcess("$spn", "Adding constrained delegation to service account for SPN")) {
                    try {
                        $null = $adentry.Properties['msDS-AllowedToDelegateTo'].Add($spn)
                        $adentry.CommitChanges()
                        Write-Message -Message "Added kerberos delegation to $spn for $ServiceAccount" -Level Verbose
                        $set = $true
                        $status = "Successfully added constrained delegation"
                    } catch {
                        Write-Message -Message "Could not add delegation. $($_.Exception.Message)" -Level Warning -EnableException $EnableException.ToBool() -ErrorRecord $_ -Target $ServiceAccount
                        $set = $false
                        $status = "Failed to add constrained delegation"
                    }

                    [pscustomobject]@{
                        Name           = $spn
                        ServiceAccount = $ServiceAccount
                        Property       = "msDS-AllowedToDelegateTo"
                        IsSet          = $set
                        Notes          = $status
                    }
                }
            } else {
                Write-Message -Message "Skipping delegation as instructed" -Level Verbose
            }
        }
    }
}