How to find certificates that are expiring on your server using PowerShell – Part 2

If you read part 1 then you know it’s pretty easy to get a list of certificates and display the days remaining until they expire. But what if you only want a list of certificates that are currently assigned (has a binding) to websites?

This is a little more challenging, but PowerShell provides some tools to help with this problem. First, let me break the steps down for you so you can try it, then I will show a single one-liner that can be easily used with PowerShell remoting to gather the list from multiple servers.

First, you need to import the WebAdministration module to load the IIS: file provider. This provider contains the SSLBindings for the websites. This will tell you which sites are using certificates.

PS> Import-Module WebAdministration

Gather a list of all certificates on the server and store them a variable:

PS> $CertAll=Get-ChildItem -Path Cert:\LocalMachine\My

Gather a list of only the certificates that are bound in IIS:

PS> $CertInUse=Get-Childitem -Path IIS:\SslBindings 

Using the PowerShell Compare-Object cmdlet, compare the two lists and only return the ones that are the same.

PS> $CertSame=Compare-Object -ReferenceObject $CertAll -DifferenceObject $CertInUse -Property ThumbPrint -IncludeEqual -ExcludeDifferent

Using the list of thumbprints from the difference object, get each certificate and display the days remaining until it expires.

PS> $CertSame | foreach{Get-Childitem –path Cert:\LocalMachine\My\$($_.thumbprint)} | Select-Object -Property Subject, @{n=’ExpireInDays’;e={($_.notafter – (Get-Date)).Days}}

You can also filter the display so that only the certificates that will expire in the next 90 days is displayed.

PS> $CertSame | foreach{Get-Childitem -path Cert:\LocalMachine\My\$($_.thumbprint)} | Select-Object -Property Subject, @{n=’ExpireInDays’;e={($_.notafter – (Get-Date)).Days}} | Where-Object {$_.ExpireInDays -lt 90}

And it can all be done in one line – Great for checking multiple servers using PowerShell Remoting.

PS> Compare-Object -ReferenceObject (Get-ChildItem -Path Cert:\LocalMachine\My) -DifferenceObject (Get-Childitem -Path IIS:\SslBindings) -Property ThumbPrint -IncludeEqual -ExcludeDifferent | Foreach{Get-Childitem -path Cert:\LocalMachine\My\$($_.thumbprint)} | Select-Object -Property Subject, @{n=’ExpireInDays’;e={($_.notafter – (Get-Date)).Days}} | Where-Object {$_.ExpireInDays -lt 90}

Kinda cool!

Jason Helmick
Director of PowerShell Technologies
Interface Technical Training