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How Prevalent Are SQL Injection Vulnerabilities?
Krishna Dagli writes to tell us of an investigation, by Michael Sutton, attempting to get an estimate of how widespread SQL-injection vulnerabilities are among Web sites. Sutton made clever use of the Google API to turn up candidate vulnerable sites. You might quibble with his methodology (some posters on the blog site do), but he found that around 11% of sites are potentially vulnerable to SQL injection attacks. He believes the causes for this somewhat alarming situation include development texts that teach programmers insecure SQL syntax, and point-and-click tools that allow the untrained to put up database-backed sites.
This is a possibility that was obvious back when I was developing web applications as far back as 1996 using CGI. The approach in TFA was a similar approach we used "back when" to demonstrate the need for (a) not using GET, (b) turning off verbose error reporting, (c) controlling *how* queries were made (e.g. architecture of the app and DB I/O), and (d) storing sensitive data encrypted. The sad part is that it is *still* a problem. I guess it underscores the need for a decent architect as opposed to letting whiz-bang do-it-yourselfers start coding without design, and the need for security analysis, et. Al. Just my 2 cents.
The simple solution is to use parameterized queries. I don't know why more books don't know why more books don't push this methodology, as it makes you program faster, easier to read, and also makes you invulnerable to SQL injection attacks.
Anthropic principle: We see the universe the way it is because if it were different we would not be here to see it.
Won't work. The same 'novices' who leave gaping SQL injection holes will now be writing pages that need to access the file system. Now instead of accessing the DB, script kiddies will be traversing the filesystem. Yes, this can be mitigated through file permissions, but there are a lot of servers out there (set up by these same novices) where processes run as root and would have full access to read and write files. So, a bad script could allow them to write to /etc/passwd and have all sorts of fun.
Why convert to an entirely different structure when just implimenting proper code standards will suffice? Using parameterized stored procedure calls instead of dynamic SQL will not only protect you from the vast majority of SQL Injection attacks, but will also improve the performance of your web page.
-Rick
"Most people in the U.S. wouldn't know they live in a tyrannical state if it walked up and grabbed their junk." - MyFirs
In short, trusting the client (i.e. the web browser) to not send bad values - either through the INPUT tag's maxlength attribute, JavaScript scrubbing or whatever - is entirely the wrong way to go. The web script must check all user input for validity along with properly escaping everything from the database that's getting sent back via HTML.
Ita erat quando hic adveni.
This 11% was determine by a weak testing mechanism. For every site that baltently spews sql errors to the user there are two that silently return a generic sanitized error, and another two that return no error at all. It would produce more results if you take it a step further and ask yes no questions, such as:
?id=99999' OR '10
and see if the page returns the results of id=10 as expected. It's also common for people to use weak regexp (regexp should NEVER be used to protect against sql injection, see mysql_real_escape_string) and miss some characters:
?id=99999)
or fail to sanitize non us language encoding. Also, get variables are often the most protected. It is much more common to find sql injection in <input type=hidden variables, or in cookie data. The number 11% is extremely low. I'd guess more like 80%.
Yeah, but most people are still stupid and humorless. So, in the end, I come out ahead.
If anything, I'd question how FEW sites they claim are vulnerable to SQL injection. It's an insidious problem that just creeps up on you anytime you don't think about it sufficiently (as when writing something quickly, on a deadline... not that this ever happens!). I know that at my workplace we fell victim at one point to a SQL injection attack on one of our (many) custom PHP scripts. We eventually found out how it worked through the web logs and were able to fix it, but honestly even after we did our best to clean things up... I'm dead certain that there are still probably hundreds of places that we're still vulnerable. This is due to a number things including the sheer volume of PHP code in use, the fact that the code has been written at various points in time over a period of six years or so, and the fact that this code has been written by at least twenty different people. It's like trying to plug holes in a dam.
Microsoft VB.NET and ASP.NET texts are AWFUL in this regard. Nearly all examples use in-line SQL queries rather than paramaterized stored procedures. Why? Probably because they are trying to fit in with Microsoft's strategy that devoping applications should require absolutely no knowledge of code (or anything else for that matter). The big selling point for their VS 2005 suite is "no code required". That speaks volume.
Or use the appropriate PEAR classes with php, like MDB2, which documents how to do prepare/executes. Don't suggest that PHP is worse than PERL because PERL has DBI, PHP has addons as well.