SQLCLR in SQL Server 2017

Published On: 2017-04-19By:

Security of your databases has become the most important part of your job as a DBA. No one wants to be the next company to leak a list of customers, leak photos of children and their parents using your company’s product, or have a key marketing database released. Security is also a very complicated, multi-layered thing. There’s not a switch you can turn on to suddenly have good security. Additionally, you can be doing all the right things, and a few bad lines of application code can subvert all of the measures you have taken to protect your data.

With this is mind, Microsoft has made some big changes to CLR in SQL Server 2017. SQL CLR has always been an interesting area of the engine—it allows for the use of .NET code in stored procedures and user defined types. For certain tasks , it’s an extremely powerful tool—things like RegEx and geo functions can be much faster in native CLR than trying to do the equivalent operation in T-SQL. It’s always been a little bit of a security risk, since under certain configurations, CLR had access to resources outside of the context of the database engine. This was protected by boundaries defined in the CLR host policy. We had SAFE, EXTERNAL_ACCESS, and UNSAFE levels that we could set. SAFE simply limited access of the assembly to internal computation and local data access. For the purposes of this post, we will skip UNSAFE and EXTERNAL_ACCESS, but it is sufficed to say, these levels allow much deeper access to the rest of the server.

Code Access Security in .NET (which is used to managed these levels) has been marked obsolete. What does this mean? The boundaries that are marked SAFE, may not be guaranteed to provide security. So “SAFE” CLR may be able to access external resources, call unmanaged code, and acquire sysadmin privileges. This is really bad.

So What Now?

Microsoft is recommending enabling “CLR Strict Security” in SQL Server 2017, which means users cannot create any CLR assemblies unless they have elevated permissions. This could be a breaking change anywhere you want to use dynamic CLR. The user needs to have CREATE ASSEMBLY and one of the following options has to be true:

  • Database has the TRUSTWORTHY property on AND the database owner (DBO) has the UNSAFE ASSEMBLY permission on the server
  • Assembly is signed with a certificate or asymmetric key that has a corresponding login with the UNSAFE ASSEMBLY permission on the server

In short, the engine treats all CLR assemblies as unsafe, even if they are created with SAFE or EXTERNAL_ACCESS permission sets.

You will need to sign your assemblies. Also, if you try to restore a database with CLR assemblies into SQL Server 2017, you may run into issues if your assemblies are unsigned.

But Now I Have to Do Work?

What does this mean for you, the SQL DBA or Developer? This is a breaking change (and breaking changes are a BIG DEAL at Microsoft—they don’t like to break things unless there are really good reasons). This means if you are using CLR, and you want to move to SQL Server 2017 (or really, let’s face it, these security risks are in lower versions of the code), you need to work out a signing system for your CLR assemblies and possibly some key management infrastructure. You need to evaluate your older CLR code to ensure that none of it is running under UNSAFE or EXTERNAL_ACCESS (unless you want to turn off “CLR Strict Security”, which you really don’t want to do). Also, if you want to run SQL Server 2017 on Linux, you will be limited to the SAFE permission set.

We Only Have Third Party Apps…

Good luck with that. This is a big change, and we all know lots of smaller independent software vendors (ISVs) have just gotten around to supporting SQL Server 2014. In most of my work with ISVs, I haven’t seen a ton of CLR in most of the vendor apps. That being said, I’m  sure it exists in many ISV apps. The angle I would take as a DBA towards my ISV(s) is to use the “audit hammer” with the vendor. If you are not familiar with this approach to managing your vendors, you can mention that your internal audit process is now failing unsigned assemblies that can’t run under CLR Strict Security. This is probably accurate anyway—CLR has been an audit flag for years. I would also recommend doing a comprehensive testing process to ensure your CLR functions as you would expect.


Don’t Assume that Your Sessions Need to Be 500 Level

Published On: 2017-04-13By:

You know what people say about what happens when you assume something, right? Don’t be an ass and make assumptions. One trend I’ve seen in recent years from some conference is that the conferences tend to prefer super advanced, internals, deep-dive sessions. While these sessions are very cool, and we all like to totally geek out about internals and the inter-workings of the query optimizer, and secret trace flags that make SQL Server return all query results as emojis. (Dear Conor, can you work on that one Smile )

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Anyway, while many of us in the SQL Server community have massive depth of knowledge about the product, and computer systems in general, it is important to realize that everyone attending SQL events is not an MCM, MVP, and MSCE. It’s great if you want to do a session on backup and restore, or how to install SQL Server (make sure to explain why you are doing each step). Topics like intro to T-SQL and Writing Your First Stored Procedure can be fantastic.

I’m not saying the whole event needs to have 100 level sessions, but making an effort to reach out to people who are just getting started could go a long way to broadening the reach of a professional association.


PASS Summit Speaker Selection Changes—My Take

Published On: 2017-03-30By:

Monday PASS announced its changes to the speaker selection process, you can read the details here. This is a big change—there will be preselected speakers from a pool have folks who have a long track record of successfully speaking at PASS Summit. Is this a good thing or bad thing? I think it is a good thing, so long as it is implemented carefully. I don’t want to see new speakers get locked out of the speaking at Summit, but I also want to see good sessions from good speakers.
This change will allow PASS to better structure the conference. A good example of this is Nic Cain’s (b|t) idea for curated tracks. In order to have a “new DBA” or “new BI analyst” track, you need to have speakers collaborating with each other in order to build the complimentary track. 

Another consideration is NDA content—a good example of this was last year. I would have loved to have done a talk about SQL Server on Linux, which I knew was going to be un-NDAed by Summit, however since submission is public, I couldn’t submit an abstract on it.

My advice for new speakers who want to speak at Summit? It’s the same as it’s always been—blog (note—the blogging part of this is important!) and speak about whatever interests you. Of course, you need to be strategic about submitting to a large conference like Summit, but to a local SQL Saturday, or a user group? Those organizers are begging for speakers. Additionally, consider speaking at PASS Virtual Chapters—they are many, and they meet every month, and there is no cost (other than your time) involved with speaking there.

As you develop as a speaker and writer, you’ll get better known, and develop your own niche. You will also get rejected. Getting rejected sucks—trust me, I submitted to three Summits before I was chosen (I was also nominated for MVP like 10x before getting it, but I digress). When you get rejected look at your abstracts and try to understand how you can make them better. Have a friend or colleague review them. This is an ongoing process.

I don’t think most speakers will notice a big difference with this new process. The speakers who are preselected, were likely going to get selected anyway. The big difference is they will have chosen their topic versus being subject to the whim of the program committee. If you’re a new speaker–speak as much as you can. VCs are free, and your local user group needs speakers. If you live in the middle of nowhere, a lot of user groups will welcome remote presentations. Hone your skills. Write some blog posts (you may have noticed this is my third blogging mention, fire up your keyboard). There’s a new version of SQL Server this year. Get inspired!


Azure Resource Locks are Your Friend in Development

Published On: 2017-03-24By:

One of the great advantages of the cloud computing is the ability to power off resources that are not in use to save some money. Sure, your production database servers should be running 24×7, but that VM, or SQL Data Warehouse you are developing against during the week? You can shut it down at 7 PM (1900 for the Europeans reading this) and not start it up. Azure even recently introduced an auto-shutdown feature for VMs.

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Unfortunately, there is no auto-startup feature, but that is easy enough to code using an Azure automation job.

This sounds great, can it walk my dog, too?

Unfortunately, there’s one problem with our awesome budget saving proposal. Sometimes developers have jobs that run beyond the time they leave the office. For example, last night at one of my clients a developer had an SSIS package running after he left, and it got killed when the SSIS machine auto-shutdown at 7. That isn’t good.

The solution for this is Azure resource locks—you can put a lock on any resource in Azure. A lock can do one of the two things—first there are delete locks which simply keep a resource from being deleted. It is not a bad idea to put a delete lock on all of your production resources to prevent any accidental deletion from happening. The second type of lock is a read-only lock, and these are a little more aggressive. You can’t do anything to a resource with a read-only lock—you can’t add a drive to a VM, you can’t resize, and most importantly, you can’t shutdown the resource.

You can use the portal, PowerShell, or CLI to create a lock. It’s a fairly simple construct that can be extremely beneficial. You can get current details for lock creation from the Azure Documentation.

My developers have access to the portal (thanks to role based access control and resource groups), so I’ve instructed them on how to place locks on resources, and how to remove them. As an administrator, you probably want to monitor for locks, to ensure that they aren’t left in place after they are needed.


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