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Configuring TLS Cipher Suites in ESXi 8.0 Update 1

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For organizations that mandate specific TLS cipher suites for compliance purposes, you may have used the instructions outlined in this VMware KB 79476 to modify the ESXi Reverse Proxy Configuration File to select the desired supported TLS cipher suites prior to ESXi 8.0 Update 1.

As of ESXi 8.0 Update 1, all configurations including configuration files have been migrated to the new ESXi Configuration Store, which was initially introduced back in vSphere 7.0 Update 1 and you can learn more about it HERE and HERE. Additionally, I recently came to learn from one of our customers, who had inquired about changing the TLS cipher suites for ESXi that as of vSphere 8.0 Update 1, ESXi now runs two reverse proxy: rhttpproxy and Envoy with port 443 now being owned by the Envoy service, which is a popular and lightweight solution for reverse proxy usage.

The implication of this change is that modifying the TLS cipher suites for ESXi as of 8.0 Update 1 now requires the use of the ESXi Configuration Store and with Envoy as the reverse proxy, it is helpful to understand the types of TLS cipher suites that can be supported will be based on Google's BoringSSL TLS implementation, which Envoy itself consumes.

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Auditing & Automating Disabled Protocols (TLS/SSLv3) for ESXi 6.0u3 & 6.5 using PowerCLI

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A couple of weeks back, I had received a question from one of our TAMs in regards to automating the disablement of specific TLS/SSL protocols for their ESXi 6.0 Update 3 hosts. As of vSphere 6.0 Update 3 and vSphere 6.5, customers now have the ability to completely disable TLS 1.0, TLS 1.1 and SSLv3 using the new TLS Reconfiguration Tool. Mike Foley did a nice write up here if you are interested in more details.

The TLS Reconfiguration Tool works well if you have the same version of vSphere for both your vCenter Server and ESXi host, but has challenges when you are in a mixed environment like this particular customer. In their environment, they are running vCenter Server 6.5 and ESXi 6.5 Update 3 which prevented them from using the TLS Reconfiguration Tool as this is a limitation with the tool today.

UPDATE (05/11/17) - Added support for ESXi 6.5 hosts as well

Given the TLS Reconfiguration Tool was written in Python, I was able to take a closer look at its implementation and I found that the settings that controlled the disabled protocols were just merely a few ESXi Advanced Settings which meant that this could be automated using standard vSphere Automation Tools that our customers were already familiar with. As part of this exercise, I also discovered the tool currently does NOT support disabling TLS/SSLv3 protocols for the Small Footprint CIM Broker (SFCB) service which is also required if you want to be in full compliance for a particular TLS protocol. Although there is not a direct SFCB API that allows you to manage the sfcb.cfg configuration file, there is still a way we can automate this without requiring SSH to the ESXi host which would technically be the alternative. Lastly, I was a bit surprised to see the TLS Reconfiguration Tool did not have a "query" option for listing the current disabled protocols for all ESXi hosts, but they do have it for vCenter Server itself.

To help this particular customer and others who may have specific TLS compliance requirements, I have created the following PowerCLI script called ESXiDisableProtocolConfiguration.ps1 which includes the following two functions:

  • Get-ESXiDPC - Retrieve the current disabled protocols for all ESXi hosts within a vSphere Cluster
  • Set-ESXiDPC - Configure the specific disabled protocols for all ESXi hosts within a vSphere Cluster

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Quick Tip - Connect-OMServer throws The request was aborted: Could not create SSL/TLS secure channel.

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While doing some work with PowerCLI and vRealize Operations Manager (vROps), I ran into the following error message when trying to connect to my vROps instance using PowerCLI:

Connect-OMServer : 2/17/2017 5:27:50 AM Connect-OMServer The request was aborted: Could not create SSL/TLS secure channel.
At line:1 char:1
+ Connect-OMServer -Server vrops.primp-industries.com -User admin -Password VMware ...
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+ CategoryInfo : NotSpecified: (VMware.VimAutom...tionServiceImpl:OMConnectionServiceImpl) [Connect-OMServer], OMException
+ FullyQualifiedErrorId : OM_ConnectivityServiceImpl_ConnectOMServer_ByUserNameAndPassword_ConnectError,VMware.VimAutomation.vROps.Commands.Cmdlets.ConnectOMServer

Although there were some hits on Google, none of the suggestions has worked. I had also found that this issue was only happening in one of my lab environments which was running Windows 2008 R2, for my other system which had Windows 8.1, the issue was not observed.

I had reached out to the PowerCLI Engineering team and it looks like the issue is due to a change in the hashing algorithm (SHA512) that vROps uses for its SSL Certificates. When using TLS 1.2, SHA512 is not supported by default. The fix is to simply install the following patch here which will resolve the problem.