With public TLS certificates moving to significantly shorter certificate lifetimes, eventually just 47 days, Always On VPN administrators supporting Secure Socket Tunneling Protocol (SSTP) connections must prepare to address this eventuality. The first milestone for shortened public TLS certificate lifetimes is a few months, on March 15, 2026, when public TLS certificate lifetimes will be reduced from a maximum of 398 days to 200 days. One year later, on March 15, 2027, they will be reduced to just 100 days. Now is the time to begin planning an automated certificate enrollment solution to reduce administrative overhead and ensure uninterrupted connectivity for remote users.
Previous Approaches: PowerShell and Posh-ACME
In the past, I’ve written about using Let’s Encrypt Certificates for Always On VPN using the Posh-ACME PowerShell module. I’ve also posted some sample code to demonstrate how to integrate with a DNS provider to automate publishing the ACME challenge to public DNS for certificate enrollment verification. However, this assumes your DNS provider supports this option. Some do not. In addition, granting write permissions to public DNS via an API key introduces significant security risks. So, if direct ACME DNS automation isn’t viable in your environment, CertKit is an excellent alternative.
CertKit: Automated Certificate Issuance, Monitoring, and Alerting
To address these limitations, administrators can use the CertKit service. With CertKit, you delegate the Let’s Encrypt certificate enrollment process to them by simply creating a CNAME record in your public DNS. Once complete, CertKit handles the entire process transparently.
Issuance
Today, CertKit supports issuing certificates using Let’s Encrypt. In the future, support for additional certificate providers such as Google Trust and ZeroSSL will be added. CertKit supports Let’s Encrypt certificates using RSA (2048-bit) and Elliptic Curve (recommended). Certificates can be issued for an individual resource, a group of resources (multi-SAN), and a domain wildcard (e.g., *.example.net).
Monitoring
In addition to certificate issuance and management, CertKit offers domain TLS certificate monitoring to track your public assets. You can monitor your CertKit-managed certificates easily, but you can also add other services using TLS and track them on the same console. In this example, I’m using CertKit to manage certificates for two VPN servers (indicated by solid green dots) and to monitor my public websites, for which certificate management is handled by their respective hosting providers.
Alerts and Notifications
CertKit will automatically send emails to let you know when a certificate is expiring and if a CertKit-managed certificate has been renewed.
Pending certificate expiration.
Successful certificate renewal.
Certificate Retrieval
Once CertKit completes the enrollment process on your behalf, it stores all certificate files (.PFX, .PEM, and .KEY) in a secure S3-compatible storage bucket. While an administrator could easily retrieve and install them manually, automation will help reduce administrative overhead, especially as public TLS certificate lifetimes are further reduced. You can download certificate files programmatically in several ways.
PowerShell
The first way to download the certificate files from CertKit is to use the AWSPowerShell module. However, the AWSPowerShell is relatively heavy and is overkill for this specific use case. A better alternative is to use the MinIO client.
MinIO
The MinIO client (mc.exe) is an open-source command-line tool developed by MinIO. It provides access to any S3-compatible storage, which CertKit uses in its environment. MinIO is a single, portable executable installer that’s easy to use and well-documented.
Sample Code
I’ve published some sample code to demonstrate how to use the MinIO client to retrieve certificates from CertKit and install them on a Windows Server Routing and Remote Access (RRAS) server. You can find the sample code on GitHub here.
https://github.com/richardhicks/aovpn/blob/master/Install-SstpLetsEncryptCertificate-Certkit.ps1
Note: This sample code demonstrates how to download a .PFX file from CertKit and install it on the RRAS server. It is designed to run as a scheduled task in Windows during non-peak times. The code includes robust checks for service viability and will reboot the server if they fail. As such, this sample code could cause service disruptions, so use it with caution.
Cost
Today, CertKit is in beta and is free for everyone to use. In the future, there will be both free and paid tiers. You can learn more about their pricing models and sign up for the service at CertKit.io.
Learn More
If you’d like to learn more about CertKit and how you can leverage it for Always On VPN and other workloads in your environment, or you’d like to see a demonstration of CertKit, fill out the form below, and I’ll provide you with more information.
Additional Information
Install-SstpLetsEncryptCertificate-Certkit.ps1 on GitHub
