SQL Injection Prevention Guidelines For Developers
July 16, 2008
One of the biggest flaws in the PHP language is the fact that it allows for web developers to make very big mistakes in regards to security. One example of this is through SQL injections- an exploit that malicious users take advantage of when web developers don’t accurately safeguard their application.
An SQL injection attack is, simply put, a vulnerability in the SQL query that programmers unwittingly leave wide open. When a web developer calls an SQL query, he or she will commonly forget to escape quotes that the user might input. Users might input text such as “MyVariable’ OR 1=1–” ; this line will actually give the malicious user to your database!
Magic quotes have long helped web developers secure their SQL query statements. But as it stands today, this function is depreciated and no longer in use. Magic quotes have received a bad reputation since they do escape quotes- but they do so on the entire input, and not necessarily just a certain field we need to escape. Magic quotes are a hassle, and can even lead to performance issues. Thus, developers tend to ignore them.
The common way to protect against an SQL injection attack is to simply use the mysql_real_escape_string() function that PHP has support for. When passing POST values through this function, the result becomes an escaped string that can’t be used to manipulate an SQL query- perfect for our situation.
Another good way to prevent SQL injections is to simply restrict authority in SQL users where possible. For instance: it would be a good idea to create individual users that do specific things: such as create a table or update rows in the said table. This can help make the task of ruining one’s hard work much harder for malicious web users, although it’s a lot more work for webmasters (Although well worth it).
A special word of advice for PHP developers: don’t buy into programs that claim they prevent SQL injections through their classes or web applications. While they may indeed do so, stopping an SQL injection is just as simple as using the previously mentioned function- no need to waste one’s money! Alternatively, SQL injection scanners can be used to help find holes.
Final Thoughts
Security is a big topic among webmasters, who make no money and achieve no fame by getting attacked via an SQL injection. To keep profits running high, it is recommended that webmasters make use of the tips previously mentioned. It’s also good to brush up on more PHP security tips, as well as make use of SQL injection scanners that are available over the Internet.
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