07. How to prevent SQL injection attacks?

Introduction

SQL injections are one of the most dangerous vulnerabilities for websites and online applications. It occurs when a malicious user adds untrusted data into a database query. We can take an example to understand SQL injections more. For instance, whenever you fill a web form, the malicious attackers create a user input to steal valuable data, cross your authentication and corrupt or steal the records in your database.

There are many types of SQL injections but their main cause is to inject untrusted data into the query string.

Before digging deeper into this interesting topic let us know about SQL first,

Table of Content

Introduction

What is SQL?

Queries
Data Manipulation Language
Data Definition Language
Data Control Language

What is SQL injection?

In-Band SQLI Attacks
Inferential SQLI Attacks
Out-of-Band SQLI Attack

Why is SQL injection a Danger?

How to prevent SQL Attacks?

Do not rely on client-side input validation
Use a database user with restricted privileges
Use prepared statements and query parameterization
Scan your code for SQL injection vulnerabilities
Use an ORM layer

Don’t rely on blocklisting
Perform input validation
Be careful with stored products

Conclusion

Closing

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What is SQL?

SQL is an acronym used from Structured Query Language. It is a type of computer language used for the management, modification and management of databases. In the recent digital era, SQL is directly processed and abstracted in your computer user interface. In ancient times, SQL queries were made on command line prompt, but now most of the operating system has it is in the interface and important files are sorted into folders on the device storage accordingly.

You might wonder, what SQL query is by some introduction of the SQL injection attacks,

Queries

These are commands that are used to request, organize data files or ask for information regarding any data file.

Data Manipulation Language

Commands that can update, modify or delete data are DML.

Data Definition Language

DDL is mostly used for managing tables and indexes.

Data Control Language

Commands that grant or revoke database rights for specific users are DCL.

Knowing about SQL and queries is important to know SQL injection attacks in depth. Let us have a quick explanation of what Is an SQL injection.

What is SQL injection?

The basic explanation for SQL injection is cyber attacks that rely on injecting malicious SQL code to a target’s database to retrieve some sensitive information that can benefit malicious users. Depending on the attacks, they can be any specific file or data that can be attacked on the target’s system to extract information about database structure.

There are several types of SQL attacks, those are,

In-Band SQLI Attacks

It is the most common type of SQL injection attack, the attacker uses the same communication method as the target to deliver malicious SQL code and gather sensitive information. These attacks are quite common because of their simplicity. In this attack, the malicious attacker provokes error messages to learn about the structure of the database.

Inferential SQLI Attacks

It is called a blind SQL injection attack because the attacker cannot collect information about the attack “In-Band”. These attacks inject SQL code and then the attacker waits for the response of the server afterwards. Based on how long the response takes so the attacker can tell if the query returned is true or false without having to see the actual message from the database.

Out-of-Band SQLI Attacks

This is a less popular mode of SQL injection in alternative to band or blind. These are typically used when the attacker cannot launch either one of the attacks to gather the information when the server is too slow or unstable. Here the attacker usually gathers information through DNS or HTTP requests.

Why is SQL injection a Danger?

One single line of SQL code can completely destroy your entire database. Even a single bit of data can entirely manipulate your whole DDL and delete crucial information. For example, a simple command can display you with the whole information of a database; it’s the same with deleting a whole dataset.

Alternatively, an SQL injection attack can be used to obtain usernames and passwords or confidential information from your database. It can give malicious attackers access to your user credentials that can be used for any future attacks.

The damage is harsh from different sorts of SQL injection attacks and can cause catastrophe and shouldn’t be underestimated. Your organization and users can be badly affected by the practices of these malicious attackers that will damage your system.

How to prevent SQL Attacks?

There are several ways to stop an SQL injection attack. These are some basic strategies that can help you identify illicit user inputs that manipulate your data,

Do not rely on client-side input validation

Client-side input validation can prevent invalid codes set to your system logic. However, a drawback to client-side input validation is that it only works for users that don’t have any bad intentions and use the site as designed. It can be used for direct feedback that is not very much helpful with SQL injection attacks. Client-side validation helps you increase your user experience due to its helpful and user-friendly nature.

When you are dealing with SQL injection, it’s not a reliable method to be dependent on. You can cut out client-side validation from your JavaScript code that is loaded in your browser.

You should validate your server-side as everything a client sends can be potentially harmful so relying on client-side validation is a terrible idea.

Use a database user with restricted privileges

There are different types of SQL injection attacks as we discussed earlier, some of them are very much harmful for your data.

When you create a user for your application, you have to think about user privileges. You need to add the roles and Permission such as ability to read, write and update the databases. If you limit the application privileges on your database, it helps you in minimizing any SQL injection attack. Security issues are most likely to cause heavy damage and being aware and taking preventive measures is necessary. It is vise to have a single database user to a database but having multiple database users you need to have specific permissions and roles assigned.

Use prepared statements and query parameterization

You can prevent SQL injection through built-in features as many languages provide this as default. Whenever you write an SQL query you can set a parameter to your statement to compile the query. You can create some base queries that you can safely attach to the user parameters.

When using statements that are parameterized, the database itself takes care of the escaping. First, it builds query execution and sends parameters to databases. The query plan is created to prevent injection.

Scan your code for SQL injection vulnerabilities

Creating custom code for SQL injection vulnerabilities is easy. To check your code, you can have security scans to check SQL vulnerabilities. You can automatically examine the vulnerabilities like SQL injection. You can use tools that can detect security vulnerabilities like SQL injection.

Use an ORM layer

The use of object-relational mapping can be efficient as it transforms data from a database into objects. Using an ORM reduces SQL queries that makes your database less vulnerable to SQL injection. You can use ORM for languages such as Java and C# as these languages strongly make it possible for mapping between object and database tables. This way you avoid getting involved in SQL queries yourself avoiding SQL injection.

To make sure your ORM doesn’t contain SQL injection problems, scanning the vulnerabilities can greatly help in avoiding injections. Using an updated ORM is necessary as using updated versions can get you in trouble.

Don’t rely on blocklisting

Blocklist approach to the collection of rules that can make your site vulnerable. That makes implementing a blocklist to your parameters can be making your website vulnerable to SQL injection. If the input meets the rules injected, the malicious user gets blocked, but if your parameters are weak the malicious entry will still be effective.

Perform input validation

Performing input validation is a must as prepared statements with parameterization acts as the best defence against SQL injection as it always creates multiple defence layers. By adding limited privileges to the user, you can reduce your site risk for SQL injection by input validation.

Some languages do not support this technique or databases that are older don’t allow you with new input parameters.

Make sure input parameters don’t rely on blocklisting as we discussed earlier. Combining the statements and parameterization can greatly help you in making your defence stronger.

Be careful with stored products

There is a myth that working with stored products can avoid SQL injection, that is absolutely wrong. Stored products can be injected with SQL injection and Parameterizing the queries in stored products can easily avoid injections.

These are the few ways you can prevent your database from SQL injection attacks.

Another more reliable solution is adding a web application firewall to the SQLI traffic of your network.

Proactively testing your network can help in finding out vulnerabilities of your site.

Conclusion

SQL injection can be a major threat to your site’s database but you can use the mentioned strategies to valid these vulnerabilities.

Closing

IntCIS provides you with a strong combination of WAF (Web Application Firewall) that can avoid SQL injection attacks and keep your data protected.

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