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Posts Tagged ‘wildcard’

To SSL or not to SSL, that is the question….

Posted by Sudarshan Narasimhan on October 22, 2011


A lot of database administrators out there would have heard of SSL (Secure Sockets Layer) and the security it offers, and thus want to configure their SQL Servers to use SSL for encryption of data on the wire. Bear in mind that SSL Encryption is very different from the built-in database encryption features like TDE. SSL is used for encrypting data transmitted across the network (on the wire) between the SQL Server and a client/application. Once configured all traffic between SQL Server and a client application is encrypted which has its advantages (secure transmission) and its disadvantages (performance impact due to the encryption and extra round-trip at connection time). SSL is a powerful feature that is a given standard of most systems and will definitely feature in a list of To-Have items if any security audit or standards are enforced in your company.

In this post I am not going to talk about what the SSL/IPSec standards, but going to focus on how to get a SSL configured for your SQL Server instance. Anyone who has setup SSL for SQL Server before might have encountered a situation where the certificate from a trusted authority does not get detected in SQL Configuration Manager. I am going to elaborate how to tackle that issue as well, so read on and stay safe!


What do you need for SSL?

Certificates! You will need to purchase/provision a certificate from a certificate authority such as VeriSign or GoDaddy.com


Pre-Requisite Reading Material

Encrypting Connections to SQL Server
http://msdn.microsoft.com/en-us/library/ms189067.aspx

How to enable SSL encryption for an instance of SQL Server by using Microsoft Management Console
http://support.microsoft.com/default.aspx?scid=kb;en-us;316898

How to Enable Channel Encryption
http://blogs.msdn.com/b/sql_protocols/archive/2005/10/04/476705.aspx

SQL Server fails to start with error 17182 "TDSSNIClient initialization failed with error 0xd, status code 0x38" when server is configured to use SSL
http://support.microsoft.com/default.aspx?scid=kb;en-US;2023869

I would highly recommend you read the above mentioned articles from MSDN and only then proceed with the steps listed below. Before going further I want to highlight a few important points from the above article regarding Certificate requirements. For SQL Server to load a SSL certificate, these are the requirements.

  1. The certificate must be in either the local computer certificate store or the current user certificate store.
  2. The current system time must be after the Valid from property of the certificate and before the Valid to property of the certificate.
  3. The certificate must be meant for server authentication. This requires the Enhanced Key Usage property of the certificate to specify Server Authentication (1.3.6.1.5.5.7.3.1).
  4. The certificate must be created by using the KeySpec option of AT_KEYEXCHANGE
  5. The Subject property of the certificate must indicate that the common name (CN) is the same as the host name or fully qualified domain name (FQDN) of the server computer. If SQL Server is running on a failover cluster, the common name must match the host name or FQDN of the virtual server and the certificates must be provisioned on all nodes in the failover cluster.

Now, these are the mandatory requirements. But how do you verify these properties are satisfied before trying to load this certificate in SQL Server. Here is where the tool CERTUTIL.exe comes in very handy. (Certutil.exe comes with Windows)

I have a certificate named SUDA24322118 which I am going to check to see if the above 5 requirements are satisfied. From an elevated command prompt, run the following: certutil -v -store "my" "SUDA24322118" >certprop.txt

Open certprop.txt in Notepad and check the following values:

Validity of the certificate (Requirement #2)

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Certificate is created for Server Authentication (Requirement #3)

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Key Specification Property (Requirement #4)

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Subject Name (Requirement #5)

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The last one is the tricky one. In my case, my machine name is SUDA24322118 and hence the subject name must be the same. Once all of the above are verified, the certificate is good to be used with SQL Server.


Wild-Card Certificates

SQL Server 2008 R2 and onwards support wildcard certificates. E.g., *.ABCXYZ.com could be the CN of a certificate. This means that the SQL Server Engine (Server side components) will allow you to load a wildcard certificate for SSL. There are some caveats you need to know regarding client-side issues, so please read the accepted wildcard examples HERE.

 

Unable to see the certificate in the drop-down list box in SQL Server Configuration Manager

If you have religiously followed all the steps till now but still unable to see/pick the certificate to load in SQL Server, then you can follow the workaround given below to use the certificate. To reproduce this issue I created 2 certificates on the same lab machine SUDA24322118 which is in a WORKGROUP.

1. Create a test certificate: I used MAKECERT.exe which is available with Windows SDK. I have Win7 SDK installed and makecert.exe is available in "C:\Program Files\Microsoft SDKs\Windows\v7.1\Bin\".

makecert -r -pe -n "CN= SUDA24322118" -b 01/01/2000 -e 01/01/2036 -eku 1.3.6.1.5.5.7.3.1 -ss my -sr localMachine -sky exchange -sp "Microsoft RSA SChannel Cryptographic Provider" -sy 12

makecert -r -pe -n "CN= SUDA24322118.bplogix.com" -b 01/01/2000 -e 01/01/2036 -eku 1.3.6.1.5.5.7.3.1 -ss my -sr localMachine -sky exchange -sp "Microsoft RSA SChannel Cryptographic Provider" -sy 12

The subject name in the 1st certificate has just the hostname of the computer whereas the second one has the FQDN. Both of them are stored in the local user store called ”my”.

2. If you open you SSCM, you see that only the 1st certificate is listed and the second one is missing.

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Surprised? Don’t be. Both of them have the same properties and satisfied all the 5 certificate requirements. You can see the certificate if you open up mmc and add the snap-in for Certificates. When asked to chose the account, select “Computer Account” for the Local computer. Both of the above certificates will be present under Personal –> Certificates.

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How do I get SQL Server to use the certificate with FQDN? Fortunately, there is a simple workaround for this.

3. Locate the Certificate Hash Value: We make use of certutil.exe again to get the cert hash value

certutil -store "my" "SUDA24322118"

certutil -store "my" "SUDA24322118.bplogix.com"

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You can pipe the results of the above command to a text file and copy the hash value highlighted above. Remove all the blank spaces, trailing and leading spaces. For the sample above, the final hash value would be: 278e30a6ba1748bbabd360b9b8ad1d78e9104d87

4. Add the hash to the SQL Server instance Registry: Open up the registry (regedit) and navigate to the SQL Server instance hive. For e.g. a default instance of SQL Server 2008 R2 would be HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Microsoft SQL Server\MSSQL10_50.MSSQLSERVER\MSSQLServer\SuperSocketNetLib\

In the above location there would be a entry called “Certificate” which would be blank by default. Paste the hash value noted in step #3 here. This associates the certificate with this hash in the local store with this instance of SQL Server. Next time, when SQL Server starts it will load this certificate.

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5. Enable Force Encryption to “Yes” using SQL Server Configuration Manager.

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Note: DO NOT navigate to the Certificate tab and try to make any changes there. Just ignore the certificate tab altogether since we have directly modified the registry (which is what the tool does anyway).

6. Restart the SQL Server service. Open the latest ERRORLOG and you can see that the certificate with FQDN has been loaded successfully.

2011-10-11 22:34:10.80 Server The certificate [Cert Hash(sha1) "278E30A6BA1748BBABD360B9B8AD1D78E9104D87"] was successfully loaded for encryption.

 

7. Make a test connection from Management Studio (SSMS) and verify using the value of column encrypt_option in the DMV sys.dm_exec_connections is TRUE, meaning the connection is being encrypted. For the real techies out there you can use Netmon or Wireshark to check if the network packet is actually being encrypted.

 

That’s all folks. There is more to client-side encryption using SSL which you can read about in the above mentioned MSDN articles. Stay secure & safe. I’ll be back with more SQL Server stuff…

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