PowerShell View Remote Server Certificate Details

Get-Cert.ps1

# This example lacks error checking

# late binding, call main AFTER defining check_ssl dependency
function main() { check_ssl -fqdn "your.fqdn.com" -port 443 }

function check_ssl($fqdn, $port) {
    $tcpsocket = New-Object Net.Sockets.TcpClient($fqdn, $port)
    $tcpstream = $tcpsocket.GetStream()
    $sslStream = New-Object Net.Security.SslStream($tcpstream, $false)
    $sslStream.AuthenticateAsClient($fqdn)
    $certinfo = New-Object security.cryptography.x509certificates.x509certificate2($sslStream.RemoteCertificate)
    # look at $tcpsocket.Client.RemoteEndPoint to see Server IP the client is using for connection
    $certinfo | fl
    $certinfo.Extensions | where {$_.Oid.FriendlyName -like 'subject alt*'} | `
      foreach { $_.Oid.FriendlyName; $_.Format($true) }
    $tcpsocket.Close() # Dispose() missing from older .NET, use Close()
}

main # run late-binding function defined at top of script

# Based on https://blogs.technet.microsoft.com/parallel_universe_-_ms_tech_blog/2014/06/26/reading-a-certificate-off-a-remote-ssl-server-for-troubleshooting-with-powershell/
# Subject Alternative Name info is displayed using technique suggested by Craig Landis
# ... https://social.technet.microsoft.com/wiki/contents/articles/1447.display-subject-alternative-names-of-a-certificate-with-powershell.aspx

This might bypass the system or user proxy settings. If so, it would be nice to have some way to test SSL using the proxy settings too.