April 19, 2021

Replacing a Self-Signed Certificate on vCenter 7.x +


Demonstration on how to replace the self-signed certificate on VMware vCenter.


Having valid certificates is not only crucial today and going forward, it has been crucial for the last few years as well. Having valid certificates not only ensures that a certain security posture being maintained, it removes any unsightly certificate warnings that make various products unfriendly to use for the administrators/engineers/architects.

I recently made a transition from Nutanix Community Edition (CE) to VMware vSphere in my home lab due to upgrade issues with the most recent release of CE. VMware vSphere 7.x and above resolved an issue where the NIC in an Intel NUC 10 was not detecting during installation and the driver needed to be sideloaded before CE could be installed. This is a continuation of my blog series where I take a focus in on security from a virtualization standpoint. Here is a similar themed blog about how to replace the self-signed certificate in Nutanix Prism Element and Prosim Central.

Today we will talk about how to replace the certificate on vCenter and how significantly easier it has become to do so. Before I start, I am going to preface this that process only applies to VMware vCenter 7.0 and above at the time of this writing. If folks are still running a vCenter 6.5 or 6.7 this will not work there as the process is completely different. Also this not only affects Citrix, it affects VMware Horizon and any other solutions that integrate into vCenter.

How many of us have in the past or even today check the box on this message to acknowledge and trust the self-signed certificate in an on-prem or cloud based full Citrix Studio?

Most of us probably click through it without second thinking why  the warning applies or also just wave it off as “that is not my problem and it is the vSphere team’s problem”. While it may be the vSphere teams problem, security should be a concern from all IT folks as there are always ways that system compromises can easily be fixed if there was a security first mentality. In addition to this, replacing the certificate will remove the warning from vCenter when folks use the vCenter web console. 

In vCenter 7.0 and above it is very easy to replace the certificate so that the warning never even pops up when establishing the Hosting connection string from Studio. 

Configuration Steps:

First we will need to create a certificate, in my case I will be using a domain certificate authority (CA). A certificate from a 3rd party well trusted CA can also be configured in this manner as well. 

I find it easier to generate the CSR on the vCenter and later will have some interesting issues from generating the CSR elsewhere.

Go to vCenter and login as administrator@vsphere.local (this is the only account that has permissions to change the certificate management) On the Top, go to Menu -> Administration

On the left pane -> Click Certificate Management

Under Actions -> Click Generate Certificate Signing Request (CSR)

Fill out the information appropriately -> Click Next

Copy or Download the CSR -> Click Finish

Open a browser and go to https://domainca.fqdn.com/certsrv replacing with your domainca FQDN. In my case it is domain1.domain.lab. -> Click Request a Certificate

Click Advanced Certificate Request

Click Submit a certificate request by using a base-64-encoded CMC or PKCS #10 file, or submit a renewal request by using a base-64-encoded PKCS #7 file

Copy and paste the contents of the CSR file generated earlier into the large field -> Select the appropriate certificate template -> Click Submit

After submitting the certificate may be pending if the CA is configured for approval (as such in my lab). Get the proper approval to issue the certificate

After approval go back to https://domainca.fqdn.com/certsrv -> Click View the Status of a Pending Certificate Request

Click on the Request from earlier -> Click on the Request
Select Base64 encoded -> Download the Certificate

Save with to a location where it can be accessed with an appropriate name –> Click Save

The domain CA’s root and intermediate certificates are required to be exported as .cer as well. In my case, these can be found on the domain controller under Certificate Manager for the Local Machine -> Trusted Root Certificate Authorities Certificates.

Back on vCenter -> Administration -> Certificate Management we need to import the Root and intermediate certificates so that the cert is trusted. -> Click Add

Browse to the root cert -> Click Add

After adding, there are now multiple Trusted Root Certificates

For the Machine Cert section Click Action -> Import and Replace Certificate

Select Replace with external CA certificate where CSR is generated from vCenter Server (private key embedded) as the CSR was generated on the vCenter -> Click Next

On the first field -> Click Browse File and select the certificate that the Domain CA issued. On the second field -> Click Browse File and select the domain CA root certificate that was exported. If there are both root and intermediate certificates they may need to be combined in notepad –> Click Next

vCenter Services will automatically restart which will take a few minutes. It is common to get this message as services are restarted.

When vCenter is back and ready log back in and go to the Certificate Management section. The Machine cert should have an updated expiration date. Track that date and make sure to repeat the process again before the certificate expires to ensure everything continues to run smoothly for any services that integrate with vCenter.

There also are no longer certificate warnings when going to the vSphere web client and when the certificate is viewed, it is the appropriate certificate

The Hosting section in Studio connects to vCenter without a warning now as well.

If you tried to generate the CSR outside of vCenter and went through the process of generating the certificate. You could get this error like I did. There really isn’t a reason why the character was invalid but this is why I recommend generating the CSR on vCenter.


VMware has made it significantly easier to replace the certificate in vSphere 7.x then it was in 6.x. It makes it almost a no-brainer to do this in my opinion. We didn't need to incure any additional costs as the certificate was generated from a domain CA, but this process would work if you need to get a signed certificate from a third party CA. If we take an overall approoach of focusing in on security in each layer of the infrastructure, we significantly improve the security posture of the entire environment and eliminate as many security flaws in the environment as possible.

We would like to hear from you so feel free to drop us a note if you have any questions.

Johnny @mrjohnnyma

No comments:

Post a Comment