Does asp.net protect against sql injection attacks

Question

By default does ASP.net protect against SQL injection attacks when using ASP controls?

Schoolroom

For better answers, you should let people know how exactly you access your database (what controls are you using). – Humbug

I don't actually have a specific use case right now. But when designing pages in the future I wanted to get an idea of the safety features built into the controls. At first I assumed I would get a number of safety features "for free" by using ASP. From the answers here I have learned a lot though. For a limited number of controls there is safety built in, for most controls there is no safety and that when coding parameters should be used to keep yourself safe. I wish I could vote several of these as "the answer" because there are lots of good things here. – Schoolroom

Answer 1

No. As long as you're supplying the SQL, it's up to you to be smart in how you use the controls.

That usually means sanitizing input and using Parameterized Queries or Stored Procedures over dynamic SQL strings.

If the control is generating the queries for you (like the Membership Controls, etc.) then you're well protected.

Immure

So when using standard ASP controls like asp:TextBox and rolling your own SQL statements in the code behind their is zero safety. When using preconfigured controls like asp:datagrid which hooks up to an asp:sqldatasource then you are protected. – Schoolroom

@Schoolroom - I would add that if you use parameterization in the codebehind, it's just as secure as the sqldatasource version. And it's possible to set up a sqldatasource without parameterizing it, which is just as unsafe as doing it in the codebehind. So parameterization is the key. – Hildredhildreth

Answer 2

Yes and no.

ADO.NET has very good support for parameterization, and when you use it properly, the parameter values will be automatically sanitized to prevent SQL injection. So you can add parameters to a SqlCommand (or a SqlDataSource control) without worrying too much about what's in them.

The good news is that parameterizing your stuff is really easy. I'll show you a C# example for doing it programmatically, but you can do it declaratively with server controls if you prefer.

The bad news is that just like anything else, you still need to think about what you're doing. Any string from an unsafe source must be parameterized if you want to have any security. If you paste it verbatim into the query, you'll have bypassed ADO.NET's security features.

Secure:

string name = txtName.Text;
sqlCommand.CommandText = "select * from product where name = @name";
sqlCommand.Parameters.AddWithValue("name", name);

Not secure:

string name = txtName.Text;
sqlCommand.CommandText = "select * from product where name = " + name;

If anything in your SQL query comes straight from the user, you need to put it in a parameter or all bets are off. And just like almost anything else, it's possible to shoot yourself in the foot if you really want to. For example, you could take SQL code, put it in a parameter, and pass it to a SQL EXEC statement. But you wouldn't do that, would you, because it is a Very Bad Idea.

Still not secure (yes, I saw this in production code)!

string sql = "select * from product where name = " + txtName.Text;
sqlCommand.CommandText = "exec(@sql)";
sqlCommand.Parameters.AddWithValue("sql", sql);

TL;DR: ADO.NET has great features to stop SQL injection, but only if you to use them correctly.

Hildredhildreth

No idea why I typed eval instead of exec. Fixed. – Hildredhildreth

Your sqlCommand2 example is a nice one. The CommandText is completely parameterized and still we're under attack. Hopefully never ever did this IRL :-) – Kymric

@Steven: I wish that were the case. This is almost exactly what I saw IRL, and I cried a little when I saw it. – Hildredhildreth

Answer 3

Most ASP.Net controls (except for DataGrid) do not use SQL at all.

If you have your own SQL in your code (using SqlCommands), you don't get any free protection; you need to use parameters.

The few controls that do use SQL (SqlDataSource and the membership framework) do use parameters and are safe against injection.

Ingeborgingelbert

Answer 4

ASP.NET does not protect against SQL injections!

ASP.NET is just the framework for web applications and it does not dictate in what way you access your database. It depends on how you implement your data access:

• If you are using ADO.NET, and are building your SQL queries as strings, then you have to sanitize any user-input to be safe from injections.
• If you are using ADO.NET and use SqlParameters, then I think you are safe against injections.
• If you are using an ORM tool for data access, then I'd say you are safe (at least when using the common ones)
• If you are using DataSets, then you are probably safe as well.
• If you are using some 3rd-party databound controls, then I hope they are taking care of protecting against SQL injections

Probably I forgot to mention a lot in my answer, but you can see that the answer is: "it depends"

Humbug

Answer 5

If you always use SqlParameters, and never concatenate user input into SQL, you should be safe. You can use SqlParameters without stored procedures too.

Hardback

Answer 6

No, ASP.Net does not protect against SQL Injections. The MS shipped code for the ASP.NEt controls is supposed to be SQL Injection free, but this does not prevent all problems one developer can corner himself into. The best defense is a good understanding of SQL Injection and careful coding. When this is unattainable, for whatever reasons, there are tools that can help like Microsoft Code Analysis Tool .NET (CAT.NET). This is a free VS plug-in that can analyze the generated assemblies and detect SQL Injection, XSS and XPath injection risks. Such a tool is not bulletproof, but is much better than nothing.

Itinerant

I found this tool very unhelpful. It didn't even find the simplest form of SQL injection such as: var cmd = con.CreateCommand();cmd.CommandText = "UPDATE T SET V = '" + text + "'";. This tool has a long way to go. – Kymric

Answer 7

Partially. There is a filter which is turned on by default which makes constructing an SQL injection attack difficult unless it's turned off.

The method which many ASPNET applications use to access MSSQL databases also makes them generally resistant to SQL injection attacks.

But it is still POSSIBLE to create a vulnerable application if you are careless enough.

Yardage

In what way does ASP's connection to DB's protect against injection attacks? If you can compromise a query then the connection method doesn't matter, yes? – Schoolroom

@Schoolroom - I didn't read that as referring to the connection itself, but the whole SqlClient stack and its security capabilities. @MarkR, maybe some elaboration is in order? – Hildredhildreth

Many applications use either a command object with parameters, or a dataset (datarow, etc) object which then generates parameterised queries internally. These patterns are not susceptible to SQL injections. Of course if you ignore those and write your own SQL, you are at risk, but still protected (somewhat) by the request filter which is turned on by default. – Yardage

That's about what I thought you meant. +1 from me. – Hildredhildreth