How to configure security for SQL Server log shipping


This article provides information about how to configure security for log shipping. There are several issues to consider when you are configuring security for SQL Server log shipping that range from the startup account for SQL Server to share permissions for the network share where the transaction log backups reside. These issues are described in this article.

Startup Account for SQL Server and SQL Server Agent Services on Log Shipping Servers

Domain Account

If you have placed SQL Server in a domain, Microsoft recommends that you use a domain account to start SQL Server services. You must use a domain account if you are going to configure SQL Server to run as a Virtual server under Windows Clustering. A domain account provides the benefit of minimal maintenance in case of password changes. However, you may not be able to start SQL under a domain account if SQL Server resides on a server that is in a workgroup.

Local Network Account

You can use SQL Server to start under a locally-created network account. In the situation where there is network access required by a SQL Server process, which is the case if you have configured SQL Server to use log shipping, you can use network pass-through security. With pass-through security, all machines that will be accessed by SQL Server must have the same network account with the same password and appropriate permissions, configured locally. Additionally, when the SQL Server process requests resources from the second computer, traditional network security is bypassed if the same account (under which the requesting SQL Server service is started) exists with the same password. As long the account on the second computer is configured with enough permission to carry out the task that is requested by calling SQL Server, the task will be successful.

Local System Account

You can also configure SQL Server to start under the Local System account. Modifying the password for the LocalSystem account may result in the failure of some services that are critical for system stability. This account is local to the computer where it resides, which means that the security context that SQL Server services uses is local. As stated in the Local Network Account section, you cannot use network pass-through security when you start SQL Server under the LocalSystem account because the passwords for the LocalSystem account on different computers are different. The starting of SQL Server under this account when network resource access is required will most likely result in the unsuccessful completion of tasks.

For information about the minimal required rights for a network account to successfully start and run SQL Server and SQL Server Agent services, view the following topic in SQL Server Books Online:

Understanding the SQL Server Security Model

To completely understand the security implications, it is important to understand the security model that Microsoft implemented in SQL Server 2000. When you create a login, it is added to the syslogins table in the MASTER database. For each database that this newly-added login is provided access to, it is added to the sysusers table in that database. The mapping between syslogins table and sysusers table is on the SID field.

If a user database is moved to a different server, the SID values are carried over from the previous server. Either database security breaks when logins on the second server are not created with the same SID values or if the security is improperly configured because of mismatching SID values.

For additional information, click the article number below to view the article in the Microsoft Knowledge Base:

240872 INF: How to Resolve Permission Issues When a Database Is Moved

Configuration of Log Shipping

Security Requirements

Backup Share

Configure the network share that is configured to hold the transaction log backups to have read/change permissions for the account under which SQL Server services (on the secondary server that is configured for log shipping) are starting.

The network share that is configured to hold the transaction log backups, should be configured to have read/change permissions for the account under which SQL Server services, on the secondary server configured for log-shipping, are starting. This share is accessed by the Copy job on the secondary server to copy the transaction log backups to the local folder on the respective secondary server. The Load job then loads these backups from the local folder.

Cross Domain Log Shipping

If computers that are running SQL Server are placed in a multi-domain environment, Microsoft recommends that you set up two-way trusts between all domains that are involved in log shipping. However, if you cannot establish trusts between domains, you can use network pass-through security for log shipping. Refer to the section of this article that discusses the LocalSystem network account startup option for SQL Server-related services.

Selecting Authentication Mode to Connect to Monitor Server

You can select either Windows authentication or SQL authentication (by primary and secondary servers) to connect to monitor server and to update the monitor tables. You can select this either while setting up log shipping or after you have set up log shipping and it is functional. By default, SQL Server uses Windows authentication; however, if you select SQL authentication, a new SQL login log_shipping_monitor_probe is created on the primary, secondary, and monitor servers if one does not exist. If you select SQL authentication for this purpose, configure SQL Server to use the SQL and Windows authentication option.

Security Configuration On Secondary Server For Standby Databases

If you configure the secondary database in standby mode, you can access this database in read-only state. By restoring the secondary database in this mode, this can provide a means by which to run offline reports, thereby offloading some of the work from the production system. However, for the standby database to support read-only functionality, you may have to apply the same security settings on secondary server. Because the database is in standby state, you cannot even make any modifications for the purposes of configuring security. In this case, you have to create all SQL Server logins with the same SID values on the secondary server. Windows logins automatically retain the same SIDs because the Windows GUID is globally unique, even when using multiple domains.

For additional information about how to create SQL logins with the same SID on different servers, click the following article number to view the article in the Microsoft Knowledge Base:
303722 How To Grant Access to SQL Logins on a Standby Database When "guest" User Is Disabled

Security Configuration When Performing Role Change

The role-change procedure for log shipping involves promoting a secondary server to take over as the primary. You can do this with or without the primary server being online. As part of the role change, there are up to four stored procedures that are executed. One of these stored procedures, sp_resolve_logins, helps to correct the SID values for logins that reside in the standby database just before it is made available for use as the primary database.

As part of this stored procedure, a .bcp file of the syslogins table from the former primary server is loaded into a temporary table. Each login that is present in this temporary table is then compared to the syslogins table in the MASTER database of the secondary server and the sysusers table of the secondary database. For each login in the temporary table that has a login with the same name in the syslogins table and same SID as the one in the sysusers table of the secondary database, the SID is corrected (in the secondary database) by using sp_change_users_login to match the one that is in the syslogins table.

Security configuration using this stored procedure requires the following:

  • SQL logins must already be created on the secondary server. To do so, use the Transfer Logins DTS task (which is explained in SQL Server Books Online topic, "How to set up and perform log shipping role change."
  • You must provide a .bcp file of the syslogins table from the primary server. This file must be current because an out-of-date file might result in sp_resolve_logins failing to fix the logins.
You must meet the following three conditions before sp_resolve_logins can actually fix the logins in the secondary database:

  1. The name of login from the .bcp file of the syslogins table must match the name in the syslogins table from the primary server.
  2. The SID value must match between the login the .bcp file and the sysusers table in the secondary database
  3. The SID value from the secondary database must be different than the SID value in the syslogins table in the MASTER database on the secondary server.
If you create SQL Server logins as described in Q303722, it does not have to run this stored procedure because all logins are already be present with the same SID value in the syslogins table (in MASTER database on the secondary server) and the sysusers table (in the secondary database).

Frequently Asked Questions

Question: Does log shipping propagate security-related changes to a secondary server automatically?

Answer: Yes. Because all changes to the system tables are logged operations, these are propagated through to the secondary server (or servers) automatically.

Question: Can you have two logins on the secondary server with the same SID? I need this because I am using the same SQL Server computer to maintain multiple standby databases from multiple servers.

Answer: No. SQL Server security model does not permit having two logins with the same SID. If there is a conflict on SID while using log shipping with multiple servers, the only way to correct this is to drop the conflicting login on the primary server, and then to create it with an SID that does not exist on the secondary server.
For additional information about log shipping role change, click the article number below to view the article in the Microsoft Knowledge Base:

314515 INF: Frequently Asked Questions - SQL Server 2000 - Log Shipping