Re: Paper: SQL Injection Attacks by Example

[Chip Andrews <chip@xxxxxxxxxxxxxxx>]

Michael,

I think David's point was that the lack of input validation that caused 
the SQL injection problem in the first place will not be mitigated by 
changing to a stored procedure.  For example if we changed the following 
standard query implementation:

Set myRS = Conn.execute("select foo from bar where id=" & 
request.form("someIntValue"))

To the following Stored Procedure implementation:

Set myRS = Conn.execute("exec usp_getFooBar " & 
request.form("someIntValue"))

We have not mitigated anything.   (simply supply the following exploit 
code in the second example:  1;exec master..xp_cmdshell 
'blahblahblah'--  etc etc)  It doesn't matter that the stored procedure 
input was well typed - our injection happens outside the stored 
procedure anyway.  And, as you mentioned, if the stored procedure uses 
the EXECUTE statment or sp_executesql  procedures then we *may* still 
have a SQL injection issue INSIDE the stored procedure as well.

If the response is "well, of course, you need to call your stored 
procedure using a parameterized query".  However, if we used 
parameterized queries then both are mitigated so changing to a stored 
procedure is a wash. 

The correct way to do data access above is like this (C# sample): 
(whether you use stored procs or not)

//Begin Sample
con = new SqlConnection(YourConnectionString);
con.Open();
string CommandText = "usp_getFooBar";
cmd = new SqlCommand(CommandText,con);
cmd.CommandType = StoredProcedure;   //Change to Text for an adhoc query
cmd.Parameters.Add(new SqlParameter("@ID", System.Data.SqlDbType.Int );
cmd.Parameters["@ID"].Value = Request.Form("someIntValue");
SqlDataReader rdr = cmd.ExecuteReader();
//close stuff as usual
//End Sample

Chip Andrews
www.sqlsecurity.com


Scovetta, Michael V wrote:

> David,
>
> Actually, to nitpick your comment a bit, stored procedures usually have
> typed input variables:
>
> 	create procedure foo ( a int, b varchar(20) ) as ...
>
> At least in MSSQL, you'd have to do something bad like use sp_executesql
> or some other function that will re-form a complete sql query and pass
> that to the interpreter. As long as you do more sensible stuff like:
>
> 	insert into table (name, age) values (@b, @a)
>
> you should be fine.
>
> Michael Scovetta
> Computer Associates
> Senior Application Developer
>
>