“It’s a Jump to the left…

… and then a double-hop to the right.” Or something like that.

I’ve commented before on the fact that I’m a consultant. I enjoy it. People will ask me what I do, and it varies. At one client they refer to their VB app as “the database” and because they found an ad of mine on Google where I talked about database administration, they hired me. About 80% of the work I do for them is actually on the VB app or related, very little is actually what I’d consider traditional database work. But that’s ok, they’re a pleasure to work with and I enjoy the work. Another client I recently worked with, asked me to help them conduct an audit of their web based product and help them with some steps to make it more secure. I was more than happy to help.

And then there’s my largest, by far, client. I actually get to do a fair amount of work that most of my #sqlfamily would recognize as “database work”. But there, perhaps more than any other, I describe my duties as “DBA and other duties as assigned.”¬† So between the work at this client and all my other clients, I’m often jumping or stepping around stuff.

The Double-Hop

This time though I was asked to double-hop. What is that exactly? It’s an issue that has to do with how Windows can pass security credentials from one server to another. This article, while old, describes it well. This was essentially the situation my client was trying to solve: Users needed to use their Active Directory (AD) Credentials to log into the Reporting Server (RS_Server) and run a report that in turn accessed data on a separate database server (DB_Server), and thus, the double-hop. Now, from my point of view, this isn’t really database work, but since the reporting server talks to the database server it was dropped in my lap under “other duties as assigned.”

Now, honestly, this SHOULD be simple to solve. It wasn’t. One reason was in part because, like many companies, this client has a separate team that handles much of their infrastructure needs, such as AD requests. And they have to go through tickets. To be clear, I support this concept, in theory. In practice, it can often take 2-3 weeks for even simple requests to go through. This meant that my first attempt at solving the double-hop failed. Their IT department did exactly what I requested. Unfortunately there was a typo in my ticket. So it failed. So round two. And round two didn’t work. Nor did round three. At this point though it wasn’t due to typos or mistakes on my end.

I started reading every article I could. My great editor at Red-Gate, Kathi Kellenberger has one, and trust me I wasn’t too shy to ask at that point! But nothing was working. I even asked another DBA at the client (they actually head up a different group and is their lead DBA). She pointed me to one of her people saying, “talk to him, he solved it.” I did, and he hadn’t. His solution was the one we were trying to avoid (basically using a fixed user in the datasource).

Frustration Sets In

I was getting frustrated. Fortunately at this point I started to exploit a loophole in the ticketing process. Since the problem wasn’t being fixed, I was able to keep it open and ended up getting assigned someone from their IT group who was as interested in fixing this as I was. This meant rather than “open a ticket, wait 1-2 weeks, have ticket be closed as complete, test, find out it failed, rinse” we could now actually schedule Zoom sessions and make changes in real-time. AND…. nothing we tried worked.

At this point you’re probably saying, “Yeah, yeah, get to the point. Did you solve it?”¬† The answer is yes, but I wanted you to feel a bit of my pain first, and I needed to make this post long enough to make it worth posting.

A Solution!

Now, let me say, I wish I could write out an exact recipe card solution for you. For various reasons, I can’t. But bear with me.

Finally, we found an additional resource in the IT group who had solved this before. His first recommendation was yet again, the solutions I mentioned above. He saw they didn’t work, agreed we were trying the right thing. So he said, “well let’s try a solution known as “Resource-based Kerberos Constrained Delegation“. This didn’t work at first either.

But then he suggested that we turn on 128 and 256 bit encryption on the DB_Server SQL account. Bingo that worked. Mostly. More on that in a second.

So here’s the setup we ended up with.

  1. RS_Server – running reporting services under an account domain\RS_Server_Service
  2. DB_Server – running SQL Server under an account domain\DB_Server_Service
  3. Setup some SPNs
    1. MSSQLsvc/DB_Server domain\DB_Server_Service
    2. MSSQLsvc/DB_Server.domain.com domain\DB_Server_Service
    3. Note in this case you do not appear to need one on the RS_Server side.
  4. Run a Powershell script
    1. $FEIdentity1 = Get-ADUser -Identity domain\RS_Server_Service
    2. $BEIdentity = Get-ADUser -Identity domain\DB_Server_Service
    3. Set-ADuser $BEIdentity -PrincipalsAllowedToDelegateToAccount $FEIdentitity1
  5. At this point things should have worked, but they didn’t until we then enabled the encryption options:

    encryption options for Kerberos

    Kerberos Encryption

  6. Then on our test box, things magically worked! Ok, not quite magically, but things worked. We had a solution.

And I was even more ecstatic when later that day, I tested this on a second report server box we had and it too suddenly was working without any changes. And this was a box where we had NOT even setup an SPN for the original double-hop solution, so I was pretty confident that the Resource-based Kerberos Constrained Delegation was working. In addition, in the rsserver.config file, the only authentication enabled was NTLM.

The next step was to try this on a production server. In that case, I did have to reconfigure the service it was running under to use the domain account domain\RS_Server_Service.

And… my test failed.

I was at wit’s end. I couldn’t quite figure out what was different. I checked my service names, my SPNs, the rsserver.config file, and more. Nothing was working. I took a break and came back and had an idea. In the datasource I changed it from:

Data source=DB_Server;Initial Catalog=TestDB

to

Data source=DB_Server.domain.com;Initial Catalog=TestDB

Bingo, it worked! A little digging confirmed my suspicion. This client actually has multiple DNS domains and the ordering and like under the TCP/IP settings was different on this box from the other two boxes. And that made the difference.

Sure enough when I tried deploying to a fourth box, I had the same issue, but changing it to the Fully Qualified Domain Name (FQDN) solved my issue.

So, my take-aways for this week:

  • ¬†Resource-based Kerberos Constrained Delegation may be a better solution at solving the Double-Hop solution than the solution generally proposed.
  • Once you’ve setup the “target” SQL Server service account and source Reporting Server Service accounts, additional reporting servers can be added to the mix without needing assistance from a domain admin.
  • It appears you still need an SPN (well multiple) for the SQL Server itself.
  • You need to run a PowerShell Script to setup the accounts. Note that if you run it again, it overwrites the old settings, so you need to add ALL of the source accounts in a single step.
  • Depending on your domains security setup, you may need to enable 128/256 bit Kerberos authentication.
  • DNS resolution may determine if you can use just the NetBIOS name or the FQDN in your data sources.
  • This solution will NOT work if you need to cross domains or have more complex setups, but in general, it can be simpler to setup and to maintain, especially if you have limited access to making changes to AD in the first place.
  • My reading indicates this only works on Windows 2012 and beyond. But you shouldn’t be running older versions of Windows in any case!

If I get the time and energy, I may setup a test environment in my home lab to further experiment with this and write up better demos, but for now, use this as you can. Hopefully it’ll save you some of the stress I experienced.

And that’s it from here, back to other duties as assigned.