What is SQL Injection (SQLi) and How to Prevent It

Vulnerabilities are a serious issue and with new malicious activity and threats popping up every day, it can be difficult to keep track of them.

But it’s not uncommon to see that the older threats are still just as serious. SQL Injections are one of the oldest tricks in the trade, but one of the most serious. Let’s take a look at why. 

What Is A SQL Injection?

SQL Injection (SQLi) is a type of injection attack that executes malicious SQL statements. Attackers may use SQL Injection vulnerabilities to bypass application security measures. Typical SQLi attacks will bypass security measures through adding, deleting and modifying records in the database.

SQL Injections can affect a variety of web applications, but are most prominently an issue for web applications that use a SQL database. Depending on the use case, these databases may hold information about customers, intellectual property, and other sensitive information. This sensitive data may be used with malicious intent in a variety of ways.

SQL Injection attacks are one of the oldest, most prevalent, and most dangerous web application vulnerabilities. Several resources list a SQL injection attack as the top three vulnerabilities to address. 

SQL databases may be set up in a way that mitigates the potential for a serious SQL injection attack. Your web application and database server don’t have to be at risk.

How SQL Injection Attacks Are Performed

Insight on how these attacks occur helps provide the foundation for preventing them. 

To start SQL Injection attacks, attackers look for vulnerable user input within the web page or web application. An example of this could be a web form, or a landing page that takes this information and inserts it directly into the database. The vulnerability lies here in the process. 

The attacker can then create false input content and is the malicious part of the process. After the attacker sends this content, SQL commands are executed in the database opening up a variety of malicious activity. 

SQL is the query language designed to manage data stored in relational databases. In some cases, you can also use SQL commands to run operating system commands. Whether it’s a SQL query or SQL statement, a successful SQL Injection attack can have very serious consequences.

How To Prevent SQL Injection Attacks

An effective way to prevent SQL Injection attacks is through input validation and parameterized queries with prepared statements. The application code should never use the input in a direct manner. All input should be sanitized in order to remove potential malicious code elements such as single quotes.

It’s also a good idea to turn off the visibility of database errors on production sites. Database errors may be used with SQL Injection to gain information about your database.

There are a few potential issues with SQL injection vulnerabilities that can’t be addressed right away. If you discover an issue and it happens to be in an open source dependency your web application uses, you may have to wait for an update on that dependency or implement a firewall to keep your application safe. Web application firewalls are an effective method to help prevent SQL injections from libraries or dependencies.

Preventing SQL Injection vulnerabilities is not always an easy or straightforward task. Specific prevention techniques depend on the subtype of SQL injection vulnerability, on the SQL database engine, and on the programming language. However, there are certain general strategic principles that you should follow to keep your web application safe. Here are some methods to help mitigate SQL injection vulnerabilities. 

There are many types of SQL injection attacks, but no matter the attack, there are many ways to prevent SQL injection vulnerabilities throughout the development lifecycle.

Train Awareness And Prevention

Your team involved in building the web application should be aware of the risks associated with SQL injection. GuardRails provides Just In Time Training to keep your team members up to speed on how to prevent these vulnerabilities and what to do in the future to avoid them. 

Sanitize User Input

Treat all user input as untrusted. Treat input from authenticated and/or internal users the same way that you treat public input. A SQL injection can easily be introduced through modifications to input values.

Use Allowlists, Not Blocklists

Don’t filter user input based on blocklists. If possible, verify and filter user input using strict allowlists only. Allowlists are an ideal way to prevent a serious SQL injection.

Update Your Tech Stack

Older web development technologies don’t have SQL injection protection. Make sure you’re development environment is updated, and the programming language, libraries and dependencies you use are all up-to-date. Guardrails has Software Composition Analysis to help double check your dependencies for any issues on their end. 

Use Trusted Technology

Don’t try to build SQL injection vulnerability protection from scratch. Most modern development technologies can offer you mechanisms to protect against SQL injection vulnerabilities. Use such mechanisms instead of trying to reinvent the wheel. For example, use parameterized queries or stored procedures.

Scan On A Regular Basis

SQL Injection vulnerabilities may be introduced by your developers or through external libraries/modules/software. Guardrails offers the ability to regularly scan your codebase to detect vulnerabilities before they become more serious issues. 

Additional SQL Injection Defense

Least Privilege Access

To further protect and minimize the potential damage of a successful SQLi attack, you should minimize the privileges assigned to each database account in your environment. Avoid assigning admin access rights to application accounts at all costs. This shortcut is one of the more serious ways SQLi vulnerabilities can be introduced. 

If an account only needs access to portions of a table, consider creating a view that limits access to that portion of the data and assigning the account access to the view only.

If you adopt a policy where you use stored procedures everywhere, and don’t allow application accounts to directly execute their own queries, then restrict those accounts to only be able to execute the stored procedures they need. Don’t grant them rights to the tables in the database.

SQL injection is not the only threat to your database data. Attackers may change the parameter values from one of the legal values they are presented with to a value that is unauthorized for them.

Minimizing the privileges granted to your application will reduce the likelihood of unauthorized access attempts, even when an attacker is not trying to use SQL injection as part of their exploit.

Multiple DB Users

Different DB users should be used for the different web applications at your organization.

In general, each web application that requires access to the database should have a designated database user account that the web-app uses to connect to the DB. In this way, developers have granularity in what they can do with access control. Specific access simplifies overhead and makes the security process more straightforward.

GuardRails And SQL Injection Prevention

GuardRails provides the platform you need to be proactive in preventing SQL Injection attacks. From inception to production, write policies to adopt best practices, or scan dependencies to make sure they’re up-to-date and ready for production. SQL Injection vulnerabilities can be devastating, but with GuardRails your team will be up-to-speed on how to prevent them, allowing you to build fast and stay safe.