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Row-Level Security (RLS) is a feature in SQL Server that offers a streamlined means of restricting access to data at a row level based on user attributes or permissions. RLS simplifies the design and coding of security in your application.
What is Row-level security?
Row-level security (RLS) is a feature that allows you to manage who can view and access certain rows in a table, providing a more granular level of security in your database. It’s an easy way to add an extra layer of protection to sensitive data and ensure that your clients see only what they’re allowed to see.
Implementing Row-Level Security in SQL Server
Defining a Predicate Function
The first step in setting up RLS is to define a predicate function. This function will return true if the user should be able to access the rows, otherwise it will return false.
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CREATE FUNCTION Security.fn_securitypredicate(@SalesRep AS sysname) RETURNS TABLE WITH SCHEMABINDING AS RETURN SELECT 1 AS fn_securitypredicate_result WHERE @SalesRep = USER_NAME() OR USER_NAME() = 'dbo' |
Adding a Security Policy
After defining the predicate function, you can now add a security policy to the table you want to implement RLS on.
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CREATE SECURITY POLICY SalesFilter ADD FILTER PREDICATE Security.fn_securitypredicate(SalesRep) ON dbo.Sales WITH (STATE = ON); |
In the example above, the policy SalesFilter invokes the function Security.fn_securitypredicate on the column SalesRep in the table dbo.Sales.
Testing the Security Policy
You can test this security policy by logging in as a different user and trying to select rows from the Sales table.
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EXECUTE AS USER = 'Bob' SELECT * FROM dbo.Sales REVERT |
With the RLS implemented, the user ‘Bob’ can only see the rows in the Sales table for which he is the sales representative.
Conclusion
Row-Level Security is a powerful SQL Server feature that can help organizations safeguard their sensitive data. It’s flexible, simple to set up, and makes managing data access at a granular level a breeze.