Microsoft Kinda, Sorta Broke RDP: That CredSSP RDP Error

If you’re running into this, it probably started on May Patch Tuesday, which was last week (the 8th). You are getting this error when you try to RDP to a/some servers:

An authentication error has occurred.

The function requested is not supported.

This could be due to CredSSP encryption oracle remediation.

Here’s what happened

An authentication error has occurred. The function requested is not supported. … This could be due to CredSSP encryption oracle remediation.

Errors make me sad

In March, a vulnerability in CredSSP (Credential Security Support Provider) was patched, which would affect authentication via RDP (this is outlined in advisory CVE-2018-0886).  However, it was implemented in such a way that the behavior change didn’t have to be “honored” by either the server or the client involved in an RDP session.


The intent was that this would be controlled by GPO in enterprise environments, and a new GPO setting to activate or deactivate this behavior was released at the same time.

GPO settings have a default value, which they will use when nothing has been explicitly set for a particular setting. In this case, the GPO has three possible values: Force Updated Clients (for servers to only take connections from patched clients), Mitigated (for both, and on a workstation means that it won’t fall back to old/insecure behavior when attaching to unpatched servers), and Vulnerable (for both, and means what it sounds like–anything goes!).

In March, the default behavior was set to “Vulnerable”, which means everything kept working for everyone. But in the May security rollup, the default setting for that GPO was flipped to “Mitigated” if there was not an explicit setting for it… end result being the core problem some are running into: Clients that have received the May update are no longer able to connect to RPD servers that have not received the March vulnerability fix.


(For a bit more background on all of this, see this Microsoft blog post:

Good News: Easy Workaround

Fortunately, there’s an easy workaround that can be applied to any Windows workstation facing this behavior, with a couple caveats.

If you are getting the above error trying to RDP to a server, all you have to do is set the corresponding GPO on your local workstation to Vulnerable.

To set this, run “gpedit.msc” on your machine. When the Local Group Policy Editor launches, navigate to Computer Configuration\Administrative Templates\System\Credentials Delegation on the left side, and then find Encryption Oracle Remediation on the right. Open that up, flip it to Enabled, and then choose “Vulnerable” for Protection Level. Hit OK, close GPEdit & you’re done; the change will take effect immediately.

There are a couple caveats: First is, this means you’re choosing to operate in an unpatched situation, which I don’t recommend. The second is that you can only apply this GPO setting on your local workstation if you’re not in an AD environment where it’s been set at the domain level and it’s getting applied to your machine. If that’s the case, the AD-level GPO will stomp on your local setting if it’s different.

Again: This should only be a temporary measure. The real fix is to get the March updates on your servers so you can set your workstation back to at least Mitigated (really should be Force Updated Clients). It’s not going to be my fault if you leave things unpatched and in Vulnerable and then something bad happens!


Some have been referring to this as a “bug” and…This isn’t a bug; I mean, the “breaking RDP” part isn’t a bug (the original vuln obviously is). This is 100% “system functions as designed.” There’s a vulnerability in a widely-used feature of Windows, and MS pulled the “better to be on the ground wishing you were in the air, than being in the air wishing you were on the ground” card here. Being a patch hard-liner (I saw too much shit in the early 2000s), I think this is fine. If you don’t like it, there’s a workaround. But, my attitude on this is tempered by the fact that it’s only listed as an “Important” update, and the exploitability seems a little bit out there. Maybe give us all a few more months to notice?

Regardless, I DO think there was a communication failure here, though. Since few people read patch notes on a regular basis (I don’t even, anymore), relying on those to get the message to people isn’t going to work. Even that PFE blog post–which is great–is still a little bit of shouting into the void until someone runs into the problem and goes looking for a solution.

I don’t know what to do about this part, because there’s really just not a mechanism to deal with it. And really, do we need another thing to watch for alerts and stuff? Plus, breaking changes happen on a regular basis… where do you draw the line? And what, should they have made the RDP client throw a pop-up message about this? That seems like an awful big hammer.

I guess I’m going to have to go back to reviewing KB articles for patches again :-/

Let’s Talk About Group Managed Service Accounts

SQL Server service dialog, Log On tabWe all know the best practices for SQL Server service accounts–domain account (if you’re using Active Directory), non local admin, different one for each service (and server/instance), etc, etc. These are, of course, good best practices and they should be followed as closely as possible in Production and on servers/instances that house Production data.

A problem arises if you have more than just a couple-few servers or run some of the BI components, however. The number of service accounts involved in your SQL Server plant could be very large, necessitating an incredible amount of overhead when it comes to managing those accounts. This goes beyond simply creating and assigning them–chances are good that there are policies in place that require changing passwords. User accounts, service accounts, and other automation accounts likely all fall under this umbrella. If you’re lucky, maybe non-user accounts have a longer change interval, but it’s still something that is going to need to be done on a regular basis. In large environments, this could take an excruciatingly awful amount of time to do.

All of this is not to mention the human factor involved here. One of the recurring themes in a couple of my presentations is making an effort to automate as many things as possible to remove the human from the process. Not that we’re bad, but there are some things, especially tedious and repetitious tasks, where dumb things go wrong simply because of the nature of the work. Changing a bunch of service account passwords is definitely one of them. There used to be two types of sysadmins: those that have changed a service account’s password but forgot to update and restart the service itself, and those who will.

Enter Group Managed Service Accounts

Group Managed Service accounts (gMSAs) are a way to avoid most of the above work. They are special accounts that are created in Active Directory and can then be assigned as service accounts. They are completely managed by Active Directory, including their passwords. This means no more manual work to meet the password-changing policy–the machine takes care of that for you.

There are other security-related controls that can be gained with them, but this is the major feature.

I’ll also note that you–the DBA–are likely to need some help from your AD admin to get these set up. They’re going to need to actually create the accounts for you in the system, and there may be some changes needed to their AD configuration in order to support them. They’ll also need to have a Windows Server 2012 (or R2) domain controller in their domain, but I’d hope today that’s not going to be a hurdle to overcome.

Since I’m mostly here to talk about SQL Server, I’ll note a couple of different support situations. gMSAs are supported from SQL Server 2014 and on running on Windows Server 2012 R2 and on for everything you can do with SQL Server–standalone instances, Failover Clusters, Availability Groups. Just plain Managed Service Accounts (MSAs) can go back a little further, but they only support standalone instances of SQL Server.

From a non-SQL Server perspective, one of the major disadvantages of gMSAs is that one can’t just use them everywhere. Services have to be specifically designed to support the use of these accounts, and that’s not going to be the case everywhere.

Since this isn’t exactly a new feature, there’s plenty of documentation and blog posts out there to read about this feature and the various requirements to implement. There’s a great overview and setup blog post on MSDN here:

That post links to this old TechNet article, which still is a pretty good resource for understanding what these things are and a little more detail on what is going on in the back-end:

Finally, my coworker Joey has a slightly older writeup here,, that walks through the process of setting this up. Note that some of the requirements have changed since that was written, but the general process remains the same.

gMSAs are a nice feature that aren’t too onerous to setup, but go a long way to make your life easier and your data far more secure.

PSA: SQL Server 2016 SP1 CU7 is a Security Update

This week (Thursday the 4th), SQL 2016 SP1 CU7 was released. Right, fine, nothing out of the ordinary.

Except there is something out of the ordinary here. CU7 includes the patches for SQL Server related to the Spectre and Meltdown vulnerabilities (for more info on these as they relate to SQL Server, see Joey’s post here and Allen’s post here), and as a result, it is being flagged and published as a security update from Microsoft as KB 4058561.

So What?

Since this is a security update, that means it will be pushed down by/via Windows Update like other normal security patches. 4058561 says that, “This update will be provided via Microsoft Update at a future date”, but it’s probably safe to assume that this “future date” will be next Tuesday, January 9th, as that is the normal Patch Tuesday this month.

All that said, then, if you are or support a shop that likes to test their SQL CUs before they get deployed, if there aren’t also positive controls on what Windows Update does, it will be a good idea to start testing this update now. Sure, the Venn diagram of “people who test CUs” and “people who let Windows Update go to town on their SQL Servers, whether it be right off the bat Tuesday night or on the next weekend” probably don’t overlap much, but in case you fall into that category: Heads up.

Remember that CUs include all patches since their “baseline” (in this case, SP1), so you’re not going to just be getting the most recent updates–you’re going to be getting an additional six CUs’ worth, too.


Once again, as everyone else is (or should be) saying, this is a big-deal security vulnerability, and you (all of you, yes, even YOU) really need to apply this patch. For SQL Servers, see guidance from MS here:

Seriously… patch your stuff.

SQL Server 2017: New Security in Analysis Services Tabular 1400

With SQL Server 2017 going GA this week, there’s been a lot of talk last week and this about new and improved features; this post is no different, but, I’m going a slightly different direction.

SQL Server Analysis Services Tabular models were first introduced with SQL Server 2012 (suddenly that seems so long ago) and have undergone continual and sometimes rapid revisions ever since. This remains true with SQL Server 2017, with the introduction of decent list of new features and other improvements.

One of the most exciting for me is the introduction of built-in support for object-level security.

But, We’ve Had Roles and Row Filters the Whole Time!

We have; you’re right. But, one thing that Tabular has never had–or Multidimensional models, either–is a built-in, easy way to do security in the other direction–columns!

Row level security is a very robust feature, and remains great. However, if there are situations where some columns or tables in the model shouldn’t be visible by all users (think Personally Identifiable Information), there wasn’t really a way to handle this before. Hoops would have to be jumped through utilizing DAX and possibly utilizing two different copies/versions of the same table in order to implement this behavior. Sometimes there would even need to be different versions of the same reports, based on which user group they were intended to target (with the underlying security/configuration of the cube driving what the user could or couldn’t see). This was, generally, a pain.

Perspectives are/were never intended as a security feature, and that hasn’t effectively changed with this.

In order to utilize this new feature (and the others), your tabular models will need to be developed/deployed in the 1400 compatibility level. This can be set when creating new models, in addition to being able to upgrade existing models (but this is a one-way street).

Azure Analysis Services

Since AAS is still my favorite thing, I can’t talk about SSAS without plugging it a little bit. Although 1400 compatibility has only been available in the on-prem product for about 24 hours now, it has been available in Preview in AAS since May. This is indicative of Microsoft’s cloud-first strategy–features will be available here first, filtering down to the on-premises software “later.” This may not be for everyone, but I think it’s one of the great reasons to consider Azure’s Platform as a Service offerings (another one is the built-in high availability).

PowerShell While Not an Admin: Well, That Wasn’t Any Fun!

Long story short (this backstory is the only thing that’s short about this post), I’m ridiculously behind in my RSS reader, but I’m working through it, as I refuse to Mark as Read en masse. One of the articles that I decided to carefully read through and follow along with is Thomas LaRock’s (blog | @SQLRockstar) SQL University post from Jan 19 (SQL University info).

Since one of my “goals” for this year is to learn PowerShell (if I stay a DBA), I followed the steps to get a feel for things (I’ve used PoSh before, but pretty much only in a copy-and-paste sense), and although the first couple commands worked as advertised, they were accompanied by some errors:

PowerShell WarningsAt first, it seemed a little odd to be getting Access Denied errors while all of the commands I was running were working. The “SQL Server Service” part & mention of WMI made it sound like a Windows-level function that the warnings were about. The commands I was running only dealt with SQL server, which could explain why they were working.

Alright, let’s back up a bit & go over the environment a little bit.

Principle of Least Privilege

The SQL Server I was connecting to is on a different machine on the network, not a local instance. Although my Windows account has SA rights on SQL, it doesn’t have any rights on the box itself (ie, not a local admin). Even though this is just equipment in the house, I have as much set up as I can in accordance with the Principle of Least Privilege. I both think this is a good idea and it gives us a more realistic environment to do testing and experimentation in.

(This whole exercise is actually a good example of why I have things set up this way: If I had gone to do anything with PoSh on, for example, our Accounting server at work, I would have run into this same situation, as the DBAs don’t have Local Admin on those servers. Instead of being surprised by this and having to run down what is going on and how to fix it, I already found it, figured out the problem & now would know what needs to be requested at the office.)

Since my account doesn’t have Admin access to the Server itself, it makes sense that I didn’t have rights for the system’s WMI service, especially remotely. Unfortunately, at the time, I hadn’t thought through the different parts of the system that PoSh was trying to touch, so I generally went in search based on the warning message.

What do WMI & DCOM have to do with Powershell?

WMI (Windows Management Instrumentation) is, put pretty simply, a way to get to administrative-type information about a machine. There are lots of ways to interact with it, and at the end of the day, it can be summed up as a way to programmatically interact with a Windows system. An example of something it can do is, say, return the status of a Windows Service…

DCOM (I had to look this chunk of stuff up) is a communication protocol used for inter-server communications by MS technologies. That’s a pretty stripped-down definition, too, but that’s the general idea.

WMI uses DCOM to handle the calls it makes to a remote machine. Since when we start it up from SSMS, Powershell seems interested in checking the status of the SQL Server service (I tried to find documentation of this, but couldn’t find anything), it makes a remote WMI call to do that. Out of the box, Server (2008 at least), doesn’t grant that right to non-Administrators, which was causing the Warning message I was getting.

Granting Remote WMI/DCOM Access

Interestingly, while searching for a resolution to this, I didn’t find anything that related to Powershell at all, let alone SQL Server specifically. For some reason I got distracted by this and wound up flopping around on a bunch of unhelpful sites and coming around the long way to a solution. However, I think this did help me notice something that I didn’t find mentioned anywhere. I’ll get to that in a second.

Here’s a rundown of what security settings I changed to get this straightened out. I’m not sure how manageable this is, but I’m going to work on that next. I’m fairly certain that everything I do here can be set via GPO, so it will be possible to distribute these changes to multiple servers without completely wanting to stab yourself in the face (and talking your Sysadin into doing it).

One of the first pages I found with useful information was this page from Reading that and this MSDN article at basically the same time got things rolling in the right direction.

Step 1: Adjust DCOM security settings

Fire up Component Services; easiest way to do this is Start | Run (Flag-R), and type in/run DCOMCNFG. Navigate to this path: Component Services\Computers\My Computer\DCOM Config\. Find Windows Management and Instrumentation, right-click on it, and choose Properties. On the Security tab, set the first two, “Launch and Activation Permissions” and “Access Permissions” to “Customize.” Click the Edit button in both of these sections and add the AD group that contains the users you want to grant access to (always grant to groups & not individual users). I checked all options in both of these places, as I want to allow remote access to DCOM.

Step 2: Add users to the DCOM Users group

The MSDN article mentioned a couple paragraphs up references granting users rights for various remote DCOM functions. While looking to set this up, I noticed something that no other article I read had mentioned (this is that bit I mentioned earlier), but I think is an important thing to cover, as it is a better way to deal with some of the security settings needed.

To see this, go back to Component Services, scroll back up to “My Computer” at the top and go to Properties again. On the “COM Security” tab, you will find two different sets of permissions that can be controlled. Click on one of the “Edit Limits” buttons (it doesn’t matter which one). The dialog will look something like this:

DCOM Users Group?

Distributed COM Users? ORLY?

A built-in security group for DCOM users? What is this? Well, turns out, it’s exactly what it sounds like it is—it’s a built-in group that already is configured to grant its members the rights needed for remote DCOM access.

That group makes this part of the setup really easy: Simply add the group containing, say, the DBAs, to this built-in group, and they magically have the needed remote DCOM rights. There’s no need to mess with the permissions on the COM Security tab talked about in this section.

Once to this point, I found that when I would run PS commands, I was now getting a different message:

Different Error after DCOM Secuirty set

The same root problem exists (“Could not obtain SQL Server Service information”, but the Access Denied part is gone, now replaced by an invalid WMI namespace message. That was much easier to troubleshoot, as it was only a WMI problem now. My assumption is that it was security-related, and that was the case, but as I found out, since I hadn’t dealt with the details of WMI security, there’s a little quirk that wound up making me burn a lot more time on this than I needed to.

Step 3: Adjust WMI security

The WMI Security settings are easier to get to than the DCOM stuff (at least it seems that way to me). In Server Manager, under Configuration, right below Services, is “WMI Control.” Right-click | Properties, Security Tab, and there ya go.

Now, here’s where some decisions need to be made. Basically, there are two options:

Grant access to everything

Only grant access to the SQL Server stuff.

Of course the easy way is to grant everything, but if these things are being changed in the first place, because a DBA doesn’t have Local Admin on the server, then that probably won’t line up with the in-use security policies.

Instead, the best thing is probably to set security on the SQL Server-specific Namespace. The path to this namespace is Root\Microsoft\SqlServer. Click on that folder, then hit the Security button. A standard Windows security settings dialog will come up. Add the desired user/group (again, probably the DBA group) here & add Execute Method & Remote Enable to the default as that should be the minimum needed. Don’t hit OK yet, however, as this is where the afore-mentioned quirk comes in.

By default, when you add a user & set rights in this WMI security dialog, it adds only for the current namespace—no subnamespaces are included. I got horribly burned by this because I’m used to NTFS permissions defaulting to “this folder & subfolders” when you add new ACLs.

WMI Security Advanced

Advanced WMI Security dialog

To fix this, click Advanced, then select the group that was just added, and click the Edit button. That will open the dialog shown above, at which point the listbox can be changed to “This namespace and subnamespaces.”

With all of that set, running SQL Server PowerShell commands should run successfully & not report any Warnings.

Firewall rules & other notes

I only addressed security-related settings here. In order for all of this to work, there may also be some firewall rules adjusted to allow DCOM traffic in addition to what is needed for PoSh access.

Putting my sysadmin hat on for a little bit, if a DBA came to me asking to change these settings, my response could be, “well that’s fine and all, but you really want me to make these changes on all dozen of our DB servers??” This is where Group Policies come in. I haven’t worked through the GPO settings needed to deploy these settings, but as I mentioned before, I’m pretty sure all of this can be set through them. I will work through that process soon & likewise document it as I go. Stay tuned for that post.

A slightly funny bit about this entire thing is due to the amount of time it took me to get this post together, I haven’t actually done anything related to Powershell! Whoops.

Good luck with Powershell everyone… I’ll get caught up eventually.