Create Self Signed Certificate with PowerShell on Windows Server 2012 R2.

A little bit outdated. I know.

But customers not always have the latest server versions running.

Today a customer asked me how to create a self signed SSL certificate with “subject alternate names” (SAN) using PowerShell on Windows Server 2012 R2.

The default cmdlet “New-SelfSignedCertificate” has not all features on this server OS.

The customer found a script but it did not offer SAN. I found another one (in german language) that gave me the other information…

Sources:

https://docs.microsoft.com/en-us/archive/blogs/vishalagarwal/generating-a-certificate-self-signed-using-powershell-and-certenroll-interfaces

https://www.symplasson.de/it-blog/san-erweiterung-csr-windows-ca

I assembled both scripts. Here is the result.

# script assembled from these sources
#  - https://docs.microsoft.com/en-us/archive/blogs/vishalagarwal/generating-a-certificate-self-signed-using-powershell-and-certenroll-interfaces
#  - https://www.symplasson.de/it-blog/san-erweiterung-csr-windows-ca
# …by Ingo Karstein ( ik a.t. kenaro.com)
#
# Useful e.g. on Windows Server 2012R2 because there are less functionality in cmdlet New-SelfSignedCertificate.
#
# The SSL cert ist written to certstore "My" of "LocalMachine"

 $name = new-object -com "X509Enrollment.CX500DistinguishedName.1"
 $name.Encode("CN=srv", 0)

 $key = new-object -com "X509Enrollment.CX509PrivateKey.1"
 $key.ProviderName = "Microsoft RSA SChannel Cryptographic Provider"
 $key.KeySpec = 1
 $key.Length = 4096
 $key.SecurityDescriptor = "D:PAI(A;;0xd01f01ff;;;SY)(A;;0xd01f01ff;;;BA)(A;;0x80120089;;;NS)"
 $key.MachineContext = 1
 $key.Create()

 $serverauthoid = new-object -com "X509Enrollment.CObjectId.1"
 $serverauthoid.InitializeFromValue("1.3.6.1.5.5.7.3.1")

 $AlternativeNames=@("srv", "localhost")
 $AlternativeIPs=@("127.0.0.1", "::1")

 $SAN = New-Object -ComObject X509Enrollment.CX509ExtensionAlternativeNames
 $IANs = New-Object -ComObject X509Enrollment.CAlternativeNames

 foreach ($SANstr in $AlternativeNames)
 {
     $IAN = New-Object -ComObject X509Enrollment.CAlternativeName
     $IAN.InitializeFromString(0x3,$SANstr)
     $IANs.Add($IAN)
 }

 foreach ($SANstr in $AlternativeIPs)
 {
     $IAN = New-Object -ComObject X509Enrollment.CAlternativeName
     $IAN.InitializeFromString(0x3,$SANstr)
     $IANs.Add($IAN)
     $IAI = New-Object -ComObject X509Enrollment.CAlternativeName    
     $IAI.InitializeFromRawData(8, 0x1, 
        [Convert]::ToBase64String(
       ([System.Net.IpAddress] $SANstr).GetAddressBytes())) $IANs.Add($IAI)
 }

 $SAN.InitializeEncode($IANs)

 $ekuoids = new-object -com "X509Enrollment.CObjectIds.1"
 $ekuoids.add($serverauthoid)

 $ekuext = new-object -com "X509Enrollment.CX509ExtensionEnhancedKeyUsage.1"
 $ekuext.InitializeEncode($ekuoids)

 $cert = new-object -com "X509Enrollment.CX509CertificateRequestCertificate.1"
 $cert.InitializeFromPrivateKey(2, $key, "")
 $cert.Subject = $name
 $cert.Issuer = $cert.Subject
 $cert.NotBefore = (get-date).AddDays(-1)
 $cert.NotAfter = $cert.NotBefore.Addyears(50)
 $cert.X509Extensions.Add($ekuext)
 $cert.X509Extensions.Add($SAN)
 $cert.Encode()

 $enrollment = new-object -com "X509Enrollment.CX509Enrollment.1"
 $enrollment.InitializeFromRequest($cert)

 $certdata = $enrollment.CreateRequest(0)

 $enrollment.InstallResponse(2, $certdata, 0, "")

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