Category: Security

Bert Wagner has a two-part series on SQL injection.  In the first post, he shows how to use sp_executesql to parameterize queries:

The important thing to note in the query above is that we are generating a dynamic SQL statement; that is, we are building the SQL query string, and then we are executing it.

Imagine this stored procedure is running in order to display a “Welcome <Full Name>!” message in our app — a website visitor types in their@ParmUserName and we execute the stored procedure to return their full name.

In his second post, Bert shows what to do if you need to run a query off of a dynamically-selected table:

Unfortunately we have to fall back on SQL’s EXEC command.

However, like we discussed last week, we need to be vigilant about what kind of user input we allow to be built as part of our query.

Assuming our app layer is already sanitizing as much of the user input as possible, here are some precautions we can take on the SQL side of the equation:

Read on for more.

Joe Obbish shows how easy it is to reverse Dynamic Data Masking:

Armed with our new knowledge, we can create a single SQL query that decodes all of the SSNs. The strategy is to define a single CTE with all ten digits and to use one CROSS APPLY for each digit in the SSN. Each CROSS APPLY only references the SSN column in the WHERE clause and returns the matching prefix of the SSN that we’ve found so far. Here’s a snippet of the code:

Click through for progressively faster solutions.  This is the main reason I do not care for DDM as a feature.  Its main benefit seems to be preventing shoulder-surfing on reports; any concerted attacker with a little bit of access to writing queries can subvert it.

Brent Ozar gives us some good pointers on when to use Always Encrypted:

But that comes with a few big drawbacks. They’re really well-documented, but here’s the highlights:

Do you need to query that data from other apps? Do you have a data warehouse, reporting tools, PowerBI, Analysis Services cubes, etc? If so, those apps will also need to be equipped with the latest database drivers and your decryption certificates. For example, here’s how you access Always Encrypted data with PowerBI. Any app that expects to read the encrypted data is going to need work, and that’s especially problematic if you’re replicating the data to other SQL Servers.

Click through to read the rest.  Always Encrypted was designed to encrypt a few columns, not everything in a database.