Enable Encrypted Connections to the Database Engine
This topic describes how to enable encrypted connections for an instance of the SQL Server Database Engine by specifying a certificate for the Database Engine using SQL Server Configuration Manager. The server computer must have a certificate provisioned, and the client machine must be set up to trust the certificate's root authority. Provisioning is the process of installing a certificate by importing it into Windows.
Starting with SQL Server 2016 (13.x), Secure Sockets Layer (SSL) has been discontinued. Use Transport Layer Security (TLS) instead.
Transport Layer Security (TLS)
SQL Server can use Transport Layer Security (TLS) to encrypt data that is transmitted across a network between an instance of SQL Server and a client application. The TLS encryption is performed within the protocol layer and is available to all supported SQL Server clients. TLS can be used for server validation when a client connection requests encryption. If the instance of SQL Server is running on a computer that has been assigned a certificate from a public certification authority, identity of the computer and the instance of SQL Server is vouched for by the chain of certificates that lead to the trusted root authority. Such server validation requires that the computer on which the client application is running be configured to trust the root authority of the certificate that is used by the server. Encryption with a self-signed certificate is possible and is described in the following section, but a self-signed certificate offers only limited protection. The level of encryption used by TLS, 40-bit or 128-bit, depends on the version of the Microsoft Windows operating system that is running on the application and database computers.
Usage of 40-bit encryption level is considered unsafe.
TLS connections that are encrypted by using a self-signed certificate do not provide strong security. They are susceptible to man-in-the-middle attacks. You should not rely on TLS using self-signed certificates in a production environment or on servers that are connected to the Internet.
Enabling TLS encryption increases the security of data transmitted across networks between instances of SQL Server and applications. However, when all traffic between SQL Server and a client application is encrypted using TLS, the following additional processing is required:
- An extra network roundtrip is required at connect time.
- Packets sent from the application to the instance of SQL Server must be encrypted by the client TLS stack and decrypted by the server TLS stack.
- Packets sent from the instance of SQL Server to the application must be encrypted by the server TLS stack and decrypted by the client TLS stack.
The certificate must be issued for Server Authentication. The name of the certificate must be the fully qualified domain name (FQDN) of the computer.
Certificates are stored locally for the users on the computer. To install a certificate for use by SQL Server, you must be running SQL Server Configuration Manager with an account that has local administrator privileges.
The client must be able to verify the ownership of the certificate used by the server. If the client has the public key certificate of the certification authority that signed the server certificate, no further configuration is necessary. Microsoft Windows includes the public key certificates of many certification authorities. If the server certificate was signed by a public or private certification authority for which the client does not have the public key certificate, you must install the public key certificate of the certification authority that signed the server certificate.
To use encryption with a failover cluster, you must install the server certificate with the fully qualified DNS name of the virtual server on all nodes in the failover cluster. For example, if you have a two-node cluster, with nodes named test1.*<your company>*.com and test2.*<your company>*.com, and you have a virtual server named virtsql, you need to install a certificate for virtsql.*<your company>*.com on both nodes. You can set the value of the ForceEncryption option on the Protocols for virtsql property box of SQL Server Network Configuration to Yes.
When creating encrypted connections for an Azure Search indexer to SQL Server on an Azure VM, see Configure a connection from an Azure Search indexer to SQL Server on an Azure VM.
For SQL Server to load a TLS certificate, the certificate must meet the following conditions:
The certificate must be in either the local computer certificate store or the current user certificate store.
The SQL Server Service Account must have the necessary permission to access the TLS certificate.
The current system time must be after the Valid from property of the certificate and before the Valid to property of the certificate.
The certificate must be meant for server authentication. This requires the Enhanced Key Usage property of the certificate to specify Server Authentication (220.127.116.11.18.104.22.168.1).
The certificate must be created by using the KeySpec option of AT_KEYEXCHANGE. Usually, the certificate's key usage property (KEY_USAGE) will also include key encipherment (CERT_KEY_ENCIPHERMENT_KEY_USAGE).
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. When using the host name, the DNS suffix must be specified in the certificate. 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.
SQL Server 2008 R2 and the SQL Server 2008 R2 Native Client (SNAC) support wildcard certificates. SNAC has since been deprecated and replaced with the Microsoft OLE DB Driver for SQL Server and Microsoft ODBC Driver for SQL Server. Other clients might not support wildcard certificates. For more information, see the client documentation and KB 258858.
Wildcard certificate cannot be selected by using the SQL Server Configuration Manager. To use a wildcard certificate, you must edit the
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Microsoft SQL Server\MSSQL12.MSSQLSERVER\MSSQLServer\SuperSocketNetLibregistry key, and enter the thumbprint of the certificate, without spaces, to the Certificate value.
Incorrectly editing the registry can severely damage your system. Before making changes to the registry, we recommend that you back up any valued data on the computer.
To provision (install) a certificate on a single server
With SQL Server 2019 (15.x), certificate management is integrated into the SQL Server Configuration Manager. SQL Server Configuration Manager for SQL Server 2019 (15.x) can be used with earlier versions of SQL Server. Refer to Certificate Management (SQL Server Configuration Manager) to add a certificate on a single SQL Server instance.
If using SQL Server 2012 (11.x) through SQL Server 2017 (14.x), and SQL Server Configuration Manager for SQL Server 2019 (15.x) is not available, follow these steps:
On the Start menu, click Run, and in the Open box, type MMC and click OK.
In the MMC console, on the File menu, click Add/Remove Snap-in.
In the Add/Remove Snap-in dialog box, click Add.
In the Add Standalone Snap-in dialog box, click Certificates, click Add.
In the Certificates snap-in dialog box, click Computer account, and then click Finish.
In the Add Standalone Snap-in dialog box, click Close.
In the Add/Remove Snap-in dialog box, click OK.
In the Certificates snap-in, expand Certificates, expand Personal, and then right-click Certificates, point to All Tasks, and then click Import.
Right-click the imported certificate, point to All Tasks, and then click Manage Private Keys. In the Security dialog box, add read permission for the user account used by the SQL Server service account.
Complete the Certificate Import Wizard, to add a certificate to the computer, and close the MMC console. For more information about adding a certificate to a computer, see your Windows documentation.
To provision (install) a certificate across multiple servers
With SQL Server 2019 (15.x), certificate management is integrated into the SQL Server Configuration Manager. SQL Server Configuration Manager for SQL Server 2019 (15.x) can be used with earlier versions of SQL Server. Refer to Certificate Management (SQL Server Configuration Manager) to add a certificate in a Failover Cluster configuration or in an Availability Group configuration.
If using SQL Server 2012 (11.x) through SQL Server 2017 (14.x), and SQL Server Configuration Manager for SQL Server 2019 (15.x) is not available, follow the steps in section To provision (install) a certificate on a single server for every server.
To export the server certificate
From the Certificates snap-in, locate the certificate in the Certificates / Personal folder, right-click the Certificate, point to All Tasks, and then click Export.
Complete the Certificate Export Wizard, storing the certificate file in a convenient location.
To configure the server to force encrypted connections
The SQL Server Service Account must have read permissions on the certicate used to force encryption on the SQL Server. For a non-privileged service account, read permissions will need to be added to the certificate. Failure to do so can cause the SQL Server service restart to fail.
In SQL Server Configuration Manager, expand SQL Server Network Configuration, right-click Protocols for <server instance>, and then selectProperties.
In the Protocols for <instance name> Properties dialog box, on the Certificate tab, select the desired certificate from the drop-down for the Certificate box, and then click OK.
On the Flags tab, in the ForceEncryption box, select Yes, and then click OK to close the dialog box.
Restart the SQL Server service.
To ensure secure connectivity between client and server, configure the client to request encrypted connections. More details are explained later in this article.
To configure the client to request encrypted connections
Copy either the original certificate or the exported certificate file to the client computer.
On the client computer, use the Certificates snap-in to install either the root certificate or the exported certificate file.
Using SQL Server Configuration Manager, right-click SQL Server Native Client Configuration, and then click Properties.
On the Flags page, in the Force protocol encryption box, click Yes.
To encrypt a connection from SQL Server Management Studio
On the Object Explorer toolbar, click Connect, and then click Database Engine.
In the Connect to Server dialog box, complete the connection information, and then click Options.
On the Connection Properties tab, click Encrypt connection.
Internet Protocol Security (IPSec)
SQL Server data can be encrypted during transmission by using IPSec. IPSec is provided by the client and server operating systems and requires no SQL Server configuration. For information about IPSec, see your Windows or networking documentation.