Category Archive: Security

Apr 19

Supported vSphere vCenter and ESXi Ciphers

Hi everyone,

One question that comes up regularly is “What ciphers are supported on vCenter and ESXi?”. I’m happy to share that we have published a VMware Knowledge Base article outlining the supported ciphers!

With all of the challenges around SSL/TLS the past year or two, having a solid idea of what ciphers are being used is becoming critical information that is necessary for IT and security teams to do their jobs.

Rather than list the ciphers here, I’ll just point you at the KB as it will be the central repository for this information and will be updated as necessary.

Please note that on some products like VCSA you’ll find more than one OpenSSL binary. For example, the VCSA will ship with a default OpenSSL binary from SUSE, the OS provider and from VMware. VMware uses OpenSSL we develop and ship and not the OS binaries. When this list was created it was done using the VMware binaries. This is helpful to understand in case your scanning tools only check against the OS binaries and report a false positive.

If you have questions, please respond directly to the KB using the provided feedback mechanism at the end of the KB article.

Thanks for reading!

If you liked these posts, please let me know! If you have comments, please reply here, to @vspheresecurity or @mikefoley on Twitter or via email to or

Apr 07

Authorized Keys and ESXi 6.0 Update 2 – Changes to OpenSSH

sshWilliam Lam brought up some feedback on Socialcast the other day. The story was of a customer who updated to ESXi 6.0 Update 2 and the SSH keys he was using no longer worked. The customer was advocating for changing the file /etc/sshd_config so that he could continue to use the keys on his ESXi server. IMHO, that’s the wrong course of action.

ESXi 6.0 Update 2 has shipped with an updated version of OpenSSH. The version has been updated to 7.1p1. One of the major changes in this release is the disablement of “ssh-dss” and “ssh-dss-cert-*” (a.k.a DSA) keys. They have also announced the future deprecation of legacy cryptography. I urge you to read more about these changes as they may impact you in other places in your infrastructure.

Now, the customer had added dss keys to the /etc/authorized_keys file so that he could easily log into his ESXi system. Ok, I get that. Adding authorized keys is a supported configuration outlined in this KB.

What happened is that now that ESXi 6.0 U2 is running the new OpenSSH bits his SSH connections were refused. This is expected behavior! This issue could be remediated by generating new keys using RSA keys. As I said above, that is the wrong course of action. You put your ESXi host at risk for convenience?

Please don’t bring up the “but DSA keys are faster/less overhead/etc” argument. I’m pretty darned sure that OpenSSH is using AES-NI instructions (I looked) that are plenty fast for a simple SSH session. Performance is no longer an excuse to use less security! It’s 2016.

Bottom line, if you are using Authorized Keys on your ESXi server and they were generated with DSA keys, it’s time to be proactive and re-generate them with RSA keys.

Final note: Limit who can log into your ESXi host. Only those you trust the most should have access. If you are logging in to “run scripts and stuff” (as many customers tell me they do) then you might want to look into using tools like the vSphere API and scripting tools like PowerCLI or Python.

If you have something you CAN’T do via API or scripting, please let us know! Reply here or send email.

Thanks for reading!

If you liked these posts, please let me know! If you have comments, please reply here, to @vspheresecurity or @mikefoley on Twitter or via email to or

Apr 01

Two Factor Authentication for vSphere – RSA SecurID – Part 2


In Part 1 of Two Factor Authentication for vSphere – RSA SecurID, we configured RSA Authentication Manager to get it ready for adding the PSC as an Authentication Manager agent. In this post, we’ll configure the Platform Services Controller (PSC) itself by uploading the sdconf.rec file and running the appropriate CLI commands to enable RSA SecurID. We’ll also talk about other authentication options you can enable or disable as you see fit.

Configure Platform Services Controller

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