How To Steal Data Using Second Order SQL Injection Attacks

Published on: 2018-03-20

One misconception some people have about SQL injection is that it can only happen when concatenating a user input parameter directly into your dynamically built query string:

While this type of injection flaw is easy to spot, there are other less direct ways an injection attack can occur.

Second Order SQL Injection Attacks

SQL injection attacks that delay execution until a secondary query are known as “second order”.

This means a malicious user can inject a query fragment into a query (that’s not necessarily vulnerable to injection), and then have that injected SQL execute in a second query that is vulnerable to SQL injection.

Let’s look at an example.

Doggo Pics

Imagine a website where dog owners can share pictures of their best friends:

The internet is a great place

Now imagine that users of Doggo Pics can set a preference for what order they view pictures when they visit the website:

When a user saves their sorting preference, the sort column and order get saved to a preferences table in the database:

No SQL injection vulnerabilities here

The next time the user goes to view the page, the doggo pictures will be sorted based on their saved preferences.  This works because the query pulling the pics/descriptions is dynamically sorting the data based on the user’s preference:

We are dynamically sorting based on the user’s preference
Viewing doggos sorted by longest tongue length

The above flow is how the website is supposed to function.  So how does a malicious user inject SQL code into these queries if the only query they directly save input into is the UpdateSortOrder procedure?

The Attack

So the developer of Doggo Pics was too busy enjoying pictures of doggos to implement any type of input validation on sort order preferences.  This means a hacker can do something like inject a SQL statement onto the end of the sort order dropdown:

The hacker modifies the “desc” value to include an INSERT statement

When our dbo.UpdateSortOrder procedure executes on the backend, it looks like this:

See where this is going?  Now when our stored procedure that dynamically sorts the picture data executes, the hacker’s INSERT statement is going to execute as well:

What happens next is simple: The first time our malicious user goes to view the Doggo Pics, they receive the pictures in their preferred sort order.  Additionally an INSERT INTO statement executes back on the server.

The second time the user views the Doggo Pics page, the values from that previously ran INSERT INTO statement are now visible on the screen:

So even though the first query the user encounters (saving sort order preferences) is entirely SQL injection free, our second order SQL injection attack occurs when our second SQL query dynamically executes the injected code that was stored in our user preferences table in the database.

How do I first and second order SQL injection attacks?

I recently presented at the GroupBy conference where I showed exactly how to protect your data from these types of attacks.

My presentation was recorded and is available for you to watch on YouTube:

You can also read more about different types of SQL injection attacks and preventative solutions by reading through my blog archives.

Thanks for reading. You might also enjoy following me on Twitter.

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2.5 Ways Your ORM Is Vulnerable To SQL Injection

Published on: 2018-03-06

Someone recently told me that they don’t need to worry about SQL injection because they are using an ORM.

Oh boy.

ORMs don’t automatically prevent SQL injection

Object-relational mapping (ORM) tools allow developers to easily access an application’s data layer without having to write lots of redundant code.

 

Most ORMs will safely parameterize certain types of queries.  The following examples use Entity Framework and SQL Server, but these examples should apply to most other major ORMs and RDBMSs).

Our LINQ query making it easy to access our data layer:

A beautiful, clean, LINQ query

And then the SQL query that our ORM generated.

A query structure that only a mother could love

You’ll notice the generated SQL query is using sp_executesql that has parameterized our input variable value “TFly37”.  In this instance we can say the ORM did a good job following best practices in preventing a successful SQL injection attack.

But while ORMs may prevent some SQL injection attempts, there is no guarantee that they will prevent all injection attempts.

 

What follows are examples of when ORMs can allow for successful injection attacks.

Programatically assembled SQL

ORMs often provide the ability for developers to map the results of adhoc SQL queries to models.  Adhoc queries mean potential injection vulnerabilities.

Consider the following:

Looks a lot like your typical SQL injection vulnerability doesn’t it?

Entity Framework, or any ORM for that matter, won’t be able to recognize a parameter concatenated directly into the query string.

Now hopefully the developer has some really strong input validation  on the “username” parameter, but the fact still stands: this query is injectable and the ORM will happily execute it.

Stored Procedures

Does the logic needed in your app already exist as a stored procedure?

Excellent!  Let’s be DRY (don’t-repeat-yourself) and call our procedure directly from our ORM:

Parameterized with the value AND datatype – give this developer a raise!

So in this example, the ORM and developer have done everything right.  So where’s the injection vulnerability?

Uh oh…

Now let me be clear: this injection vulnerability is not the ORM’s fault.

However, it is the developer’s fault if he is blindly using a procedure without knowing what it does.  It’s also the DBA’s fault if she provided an injectable procedure assuming the developer would sanitize any input values in the app.

Security is hard.  Everyone needs to work together and be responsible for doing everything within their means to secure their applications.

ORM injection

Technically this isn’t an example of SQL injection.

But that’s why the title of this post says “2.5” instead of “3”.

In this example I’m using a dynamic LINQ to access my data:

Hello concatenation my old friend

If we pass the value  \" OR 1 == 1 OR UserName==\" we will have the ORM convert it to the following query:

Game over

Injection takes many forms and doesn’t just come straight from SQL.  It’s important to follow best practices in all languages and tools to prevent security incidents.

Want to learn more?

If you are interested in learning more about how to protect yourself from SQL injection, be sure to  watch my online session at GroupBy at 9am Eastern on March 16th, 2018.

Thanks for reading. You might also enjoy following me on Twitter.

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4 Common Misconceptions About SQL Injection Attacks

Published on: 2017-11-07

Photo by Jaanus Jagomägi on Unsplash

Interested in learning more about SQL injection attacks, including how to prevent them?  Attend my online webcast on Tuesday November 14, 2017 at 1PM Eastern at the PASS Security Virtual Group.

SQL injection continues to be one of the biggest security risks that we face as database professionals.

Every year, millions of users’ personal information is leaked due to poorly written queries exploited by SQL injection.  The sad truth is that SQL injection is completely preventable with the right knowledge.

My goal today is to cover four common misconceptions that people have about SQL injection in an effort to dissuade any illusions that an injection attack is not something that can happen to you.

Prefer watching me get angry about these common misconceptions?  You can watch this content on my YouTube channel.

1. “My database information isn’t public”

Let’s see, without me knowing anything about your databases, I’m guessing you might have some tables with names like:

  • Users
  • Inventory
  • Products
  • Sales
  • etc…

Any of those sound familiar?

You might not be publicly publishing your database object names, but that doesn’t mean they aren’t easy to guess.

All a malicious user needs is a list of common database table names and they can iterate over the ones they are interested in until they find the ones that match in your system.

2. “But I obfuscate all of my table and column names!”

Oh jeez.  I hope you don’t do this.

Some people do this for job security (“since only I can understand my naming conventions, I’m guaranteeing myself a job!”) and that’s a terrible reason in and of itself.

Doing it for security reasons is just as horrible though.  Why?  Well, have you ever heard of some system tables like sys.objects and sys.columns?

A hacker wanting to get into your system can easily write queries like the ones above, revealing your “secure” naming conventions.

Security through obscurity doesn’t work.  If you have table names that aren’t common, that’s perfectly fine, but don’t use that as your only form of prevention.

3. “Injection is the developer’s/dba’s/somebody else’s problem”

You’re exactly right.  SQL injection is a problem that should be tackled by the developer/dba/other person.

But it’s also a problem that benefits from multiple layers of security, meaning it’s your problem to solve as well.

Preventing sql injection is hard.

Developers should be validating, sanitizing, parameterizing etc…  DBAs should be parameterizing, sanitizing, restricting access, etc..

Multiple layers of security in the app and in the database are the only way to confidently prevent an injection attack.

4. “I’m too small of a fish in a big pond – no one would go out of their way to attack me”

So you run a niche business making and selling bespoke garden gnomes.

You only have a few dozen/hundred customers, so who would bother trying to steal your data with SQL injection?

Well, most SQL injection attacks can be completely automated with tools like sqlmap.  Someone might not care about your business enough to handcraft some SQL injection code, but that won’t stop them from stealing your handcrafted garden gnome customers’ data through automated means.

No app, big or small, is protected from the wrath of automated SQL injection tooling.

Interested in learning more about SQL injection attacks, including how to prevent them?  Attend my online webcast on Tuesday November 14, 2017 at 1PM Eastern at the PASS Security Virtual Group.

Thanks for reading. You might also enjoy following me on Twitter.

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Sign up for my newsletter to receive weekly SQL tips!