Monday, August 26, 2013

Sending Encrypted S/MIME Messages with PowerShell

First you need the public key of the recipient.  In this example we will retrieve the public key from AD.  Public keys are stored in userCertificate which is a multivalued attribute, so we must pick a valid certificate from all the certificates that may be in the attribute.  We’re looking for a certificate which is usable for Secure Email and is currently valid for use (within a 5 minute skew).  We will pick the first certificate that meets those criteria.
$RecipientCN='someusername'
$RootDSE = [ADSI]("LDAP://RootDSE")
$SearchForestForPerson = New-Object DirectoryServices.DirectorySearcher
$SearchForestForPerson.SearchRoot = "GC://" + $RootDSE.rootDomainNamingContext
$SearchForestForPerson.SearchScope = "subtree"
$SearchForestForPerson.PropertiesToLoad.Add("distinguishedname") | Out-Null
$SearchForestForPerson.PropertiesToLoad.Add("mail") | Out-Null
$SearchForestForPerson.PropertiesToLoad.Add("usercertificate") | Out-Null
$SearchForestForPerson.Filter = ("(&(objectClass=person)(CN=$RecipientCN))")
$Recipient = $SearchForestForPerson.FindOne()
$ChosenCertificate = $null
$Now = Get-Date
If ($Recipient.Properties.usercertificate -ne $null) {
    ForEach ($UserCertificate in $Recipient.Properties.usercertificate) {
        $ValidForSecureEmail = $false
        $Certificate = [System.Security.Cryptography.X509Certificates.X509Certificate2]$UserCertificate
        $Extensions = $Certificate.Extensions
        ForEach ($Extension in $Extensions) {
            If ($Extension.EnhancedKeyUsages -ne $null) {
                ForEach ($EnhancedKeyUsage in $Extension.EnhancedKeyUsages) {
                    If ($EnhancedKeyUsage.FriendlyName -eq "Secure Email") {
                        $ValidForSecureEmail = $true
                        break
                    }
                }
                If ($ValidForSecureEmail) {
                    break
                }
            }
        }
        If ($ValidForSecureEmail) {
            If ($Now -gt $Certificate.NotBefore.AddMinutes(-5) -and $Now -lt $Certificate.NotAfter.AddMinutes(5)) {
                $ChosenCertificate = $Certificate
            }
        }
        If ($ChosenCertificate -ne $null) {
            break
        }
    }
}
Now that we have a valid certificate, compose and send the email.  The forum message at http://social.msdn.microsoft.com/Forums/en-US/74e4711e-1f66-43a7-9e3b-bc9cfbcd1b73/sending-smime-encrypted-email-using-c provided most of the basis for getting the encryption correct.
Add-Type -assemblyName "System.Security"
$MailClient = New-Object System.Net.Mail.SmtpClient "relay.widgets.com"
$Message = New-Object System.Net.Mail.MailMessage
$Message.To.Add($Recipient.properties.mail.item(0))
$Message.From = "noreply@widgets.com"
$Message.Subject = "Unencrypted subject of the message"
$Body = "Encrypted body of the message"
$MIMEMessage = New-Object system.Text.StringBuilder
$MIMEMessage.AppendLine('Content-Type: text/plain; charset="iso-8859-1"') | Out-Null
$MIMEMessage.AppendLine('Content-Transfer-Encoding: 7bit') | Out-Null
$MIMEMessage.AppendLine() | Out-Null
$MIMEMessage.AppendLine($Body) | Out-Null
[Byte[]] $BodyBytes = [System.Text.Encoding]::ASCII.GetBytes($MIMEMessage.ToString())
$ContentInfo = New-Object System.Security.Cryptography.Pkcs.ContentInfo (,$BodyBytes)
$CMSRecipient = New-Object System.Security.Cryptography.Pkcs.CmsRecipient $ChosenCertificate
$EnvelopedCMS = New-Object System.Security.Cryptography.Pkcs.EnvelopedCms $ContentInfo
$EnvelopedCMS.Encrypt($CMSRecipient)
[Byte[]] $EncryptedBytes = $EnvelopedCMS.Encode()
$MemoryStream = New-Object System.IO.MemoryStream @(,$EncryptedBytes)
$AlternateView = New-Object System.Net.Mail.AlternateView($MemoryStream, "application/pkcs7-mime; smime-type=enveloped-data;name=smime.p7m")
$Message.AlternateViews.Add($AlternateView)
$MailClient.Send($Message)

Tuesday, June 18, 2013

FIM CSExport fails to run as a scheduled task

 

In our FIM environment we want to retrieve the list of pending exports.  This is typically accomplished with a “csexport.exe MAName /f:x” command.  On my dev environment as a user with FIMSyncAdmins rights, the export is produced as expected.

When I ran the command as a scheduled task I would receive this error message in our log file

Microsoft Identity Integration Server Connector Space Export Utility v4.1.3419.0
c 2012 Microsoft Corporation. All rights reserved

Failed to export connector space.
Error: <error>The Synchronization Service Manager service has stopped.</error>

It’s an odd message in that the Sync service was absolutely running.

After making sure there was nothing wrong with the PowerShell script that was driving the command, I eventually tried elevating the service account to include local admin rights, and at that point it succeeded.

From there I took a leap of faith that the Sync service account really was running, but under a non-admin scheduled task, it couldn’t see that the service was running for some reason.  Recalling the Service Control Manager hardening from Windows Server 2003 SP1, I was guessing the scheduled task couldn’t query the SCM.

Sure enough, reviewing the default ACLs

C:\Windows>sc sdshow FIMSynchronizationService

D:(A;;CCLCSWRPWPDTLOCRRC;;;SY)(A;;CCDCLCSWRPWPDTLOCRSDRCWDWO;;;BA)(A;;CCLCSWLOCR
RC;;;IU)(A;;CCLCSWLOCRRC;;;SU)S:(AU;FA;CCDCLCSWRPWPDTLOCRSDRCWDWO;;;WD)

As an Interactive User (IU) you get read access to the service.  But as a scheduled task you don’t get the IU SID.  The solution is to grant the FIMSyncAdmins group read access to the service.

With a small PowerShell script to determine the local group’s SID, we can update the SDDL for the service

C:\Windows>sc sdset FIMSynchronizationService D:(A;;CCLCSWRPWPDTLOCRRC;;;SY)(A;;
CCDCLCSWRPWPDTLOCRSDRCWDWO;;;BA)(A;;CCLCSWLOCRRC;;;IU)
(A;;CCLCSWLOCRRC;;;S-1-5-2
1-2974223652-3803999246-3267058373-1009)
(A;;CCLCSWLOCRRC;;;SU)S:(AU;FA;CCDCLCSWR
PWPDTLOCRSDRCWDWO;;;WD)
[SC] SetServiceObjectSecurity SUCCESS

And now CSExport works from a scheduled task.