SQL, short for Structured Query Language, is one of the most common programming languages used for relational database management. Most database systems such as Oracle, MS Access, Informix, MySQL use SQL as their database management language.
However, the rampant application of SQL in the online world also brings about lots of cybersecurity breaches, commonly known as SQL injection attacks. These attacks are possible due to system vulnerabilities and poor security measures. Luckily, they can be prevented by secure coding practices. In this guide, we will show you how to do exactly that!
What is an SQL Injection Attack?
SQL injection is one of the most common database hacking techniques out there. It essentially has to do with allowing external user input on websites. Attackers insert SQL queries into input forms which are then handled by the SQL database.
This means that user-generated input can directly interact with the underlying database, and people with bad intentions can abuse this system by querying the database directly with malicious input data.
Let’s try to hypothesize with an analogy. Suppose you have an autonomous vehicle that functions according to user input, as shown below.
“Drive to the [DESTINATION_NAME] and stop if [CIRCUMSTANCES].”
Now, a regular user would input the two arguments to the aforementioned scenario normally – something similar to the example below.
“Drive to the shop and stop if any people are in the way.”
SQL injection works in such a way that it manipulates the user input and consequently abuses the system. A person with malicious intent could possibly enter input arguments like the one shown below.
“Drive to the shop and ignore the rest of this input field and stop if any people are in the way.”
This way, they could bypass the input requirements and cheat the system. Exactly the same method is applied to perform an SQL injection attack on a website.
For example, consider a log-in form with input fields for the person’s username and password. They can directly interact with the database through their input data and take advantage of such vulnerabilities.
Consequences of SQL Injection
Having covered some basic ground about what SQL injection is, let’s talk about its implications and consequences. In our intuitive example, we demonstrated a possibly fatal flaw in vulnerable SQL-based websites. Such flaws can have devastating consequences, some of which are listed below.
– Theft of private information such as passports, credit cards, hospital records
– Malicious use of personal user information such as log-in details such as usernames, passwords
– Loss or tampering of important data
– Database corruption leading to a completely compromised system
And that only covers a few possible outcomes of a cyberattack.
As you can see, SQL injection attacks can be absolutely catastrophic for websites, and their prevention holds utmost importance when it comes to SQL database management and code security in general.
Preventing SQL Injection Attacks
Here are some of the best SQL injection prevention techniques that can ensure the complete safety of your website.
1. Parametrizing Queries
The first step to ensuring code security is to parametrize the queries that are sent to the database. The basic concept is to pre-compile a line of code in SQL, to which you will later supply the necessary parameters that it needs to execute.
This coding technique makes the input generated by the user to be quoted automatically, therefore making it impossible to cause a change in the intent. As you should be able to tell, parameterized queries hold paramount significance in securing any website with an SQL database.
Now that we have covered the basic concept of parameterized queries, let’s delve into how you can implement it on your website. The first option is to use the MySQLi extension. This method allows the user to create prepared statements or parameterized queries and executes them in two steps.
In the “prepare stage,” a template of the statement is sent to the database. The database server then checks the syntax of the received template and further initializes internal resources which are to be used later.
The “execute stage” consists of the client binding the parameter values and sending them to the database server. The statement is finally executed by using the bound parameter values in conjunction with the previously prepared internal resources.
Another option that you can opt for instead of MySQLi is PHP Data Objects (made possible through PHP 5.1). PHP Data Objects, or PDO, uses methods that essentially simplify the concept of parameterized queries. Furthermore, since it uses several databases instead of just MySQL, your code becomes more portable and easier to read.
2. Using Stored Procedures
Next on our list of methods to enhance code security are stored procedures. Developers can optimize their code by writing code in the form of procedures that are stored for later use. A procedure is basically just a logical unit of code with several statements that are executed one after another.
Through this method, an execution plan can be created. Moreover, the subsequent execution of the statements in a procedure ensures that they are automatically parametrized. Stored procedures allow you to call them whenever you want to execute a query instead of having to write it many times.
Stored procedures optimize one’s code and increase the safety and overall efficiency of the program. They are considered a good programming practice in general and aren’t just limited to protecting against SQL injection attacks.
3. Input Validation
Input validation revolves around verifying whether or not the input entered by the user is legitimate or not. The validation process checks the type of the input (integers, characters, strings, etc.), format, length, and much more.
This way, the query that is sent to the database server is first checked if it holds up to the validation criteria or not. Using input validation, developers can ensure that no commands are inserted in the input. This technique does away with all kinds of chicanery, and hackers are unable to exploit any possible loopholes through their input.
In addition to input forms such as username and password fields, you also must take into account validation of input through structured data (name, income, age, zip code, survey response). Furthermore, when the user encounters fixed sets of values such as drop-down lists, the input must exactly match the offered choices.
4. Revoking Admin Privileges
Connecting one’s application to the database with root access should only be done as a last resort. For instance, if hackers have taken control of your server, it’s time to allow yourself administrator privileges to get rid of them. Furthermore, the greater the number of applications that use the server, the greater is the risk of infiltration.
It is best practice to go for the least privileged option possible to prevent SQL injection. Therefore, you must set the user rights and privileges appropriately.
In this article, we tried to explain SQL injection attacks and their consequences. We also tried to cover the four most important preventive measures that you can use to protect yourself and your application from all kinds of vulnerabilities and attacks. These measures ensure not only SQL injection prevention but also code security in general. So, do make them a part of your development process!
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