What are the security risks and implications of using extended stored procedures?

1 What are extended stored procedures?

Extended stored procedures are dynamic-link libraries (DLLs) that can be registered and executed by SQL Server. They are similar to regular stored procedures, except that they run code outside the SQL Server process. You can create your own extended stored procedures using C or C++, or use the ones provided by Microsoft or third-party vendors. To call an extended stored procedure, you use the sp_executesql system stored procedure or the EXECUTE statement with the xp_ prefix.

2 What are the security risks of extended stored procedures?

One of the main security risks of extended stored procedures is that they can bypass the normal SQL Server security mechanisms and permissions. This means that they can access any file, registry key, network resource, or system function that the SQL Server service account has access to. This can expose sensitive data, compromise system integrity, or allow malicious code execution. For example, an extended stored procedure could read or write files on the server, delete or modify database objects, or execute commands on the operating system.

3 How can you mitigate the security risks of extended stored procedures?

To mitigate the security risks of extended stored procedures, you should follow some best practices and guidelines. First, you should avoid using extended stored procedures unless absolutely necessary, and prefer using built-in features or CLR integration instead. Second, you should limit the use of extended stored procedures to trusted and authorized users, and grant only the minimum permissions required for the task. Third, you should validate and sanitize any input parameters and output values to prevent SQL injection or data corruption. Fourth, you should use encryption and authentication to protect the communication between SQL Server and the external code. Fifth, you should monitor and audit the activity and performance of extended stored procedures to detect any anomalies or errors.

4 How can you debug extended stored procedures?

Debugging extended stored procedures can be challenging, as they run in a separate process and environment from SQL Server. You cannot use the standard SQL Server debugging tools or error messages to troubleshoot them. Instead, you need to use a debugger that can attach to the DLL process and set breakpoints, watch variables, and step through the code. You can use Visual Studio, WinDbg, or other debuggers that support DLL debugging. You also need to enable the debug mode for the extended stored procedure by using the sp_addextendedproc system stored procedure with the debug option.

5 What are the alternatives to extended stored procedures?

If you need to execute external code from within SQL Server, but want to avoid the security risks and implications of extended stored procedures, you have some alternatives to consider. One option is to use CLR integration, which allows you to create and execute .NET code in SQL Server. CLR integration offers better security, performance, and compatibility than extended stored procedures, but requires some additional configuration and deployment steps. Another option is to use external scripts, which allow you to execute R or Python code in SQL Server. External scripts can be useful for data analysis, machine learning, or data visualization, but require installing and enabling the Machine Learning Services feature.