Computer Security, Privacy, Programming, Technology, Tutorials, Web Security

Hacking And Protecting Websites From SQL Injection Attacks

August 16, 2017

Introduction

SQL injection is a widespread attack vector employed to run statements on a web site’s database server. If a black hat hacker acquires access to a site’s SQL database, he may steal, erase, or insert information. SQL injection attacks are annoying and arduous to fix. Hence, it’s recommended that the webmaster implements the relevant safeguards prior becoming a victim.

Before protecting a site from SQL injections, the webmaster needs to know how SQL injection attack vectors work.

This article will demonstrate the following:

  • Writing SQL Statements
  • How Black Hat Hackers Can Write SQL To Exploit And Gain Control A Target’s SQL Database
  • How To Defend Sites From SQLi
  • Mitigating Effectiveness Of Code Injection Techniques Deployed To Exploit Data-Driven Web Applications

NOTE: All information in this article is for educational purposes only.

How To Write SQL

Prior to understanding how SQL injection works, the site owner needs to have some understanding of the SQL language. SQL is the language for Oracle, MySQL, and SQL Server. These three database engines contain distinct syntax, though all of them utilize four basic functions: INSERT, SELECT, DELETE, and UPDATE. Black hat hackers can deploy any of these functions to manipulate a site’s data. Thus, it is imperative to protect against any type of SQL injection.

Let’s look at the following basic SQL code example:

select * from customer

The statement illustrated above queries all records in the customer table and returns them all back including every column in the table. Fundamentally, this query returns all of the customer information. For nearly all queries, you don’t need to return every record and column. You may use the SQL WHERE clause to filter records with merely a particular set of values.

For nearly all queries, you don’t need to return every record and column. You may use the SQL WHERE clause to filter records with merely a particular set of values.

For example, the subsequent SQL code returns every record where the customer’s first name is “Sunny”:

select * from customer where first_name=’sunny’

The aforementioned code returns merely records where the first name “sunny,” and this kind of statement is where malicious actors use to their benefit.

An example of the structure of an SQL statement.

 SQL Injection Syntax

SQL Injection may be extremely intricate, but let’s analyze some basic examples. As you grasp basic concepts, you may examine more complicated SQL injection attack vectors.

SQL injections typically occur through a site’s form submissions. The subsequent code serves as an example of a form that requests the user to fill in their first name.

<form method=”post”>

<input type=”test” name=”first_name”

id=”first_name”>

<input type=”submit” value=”Submit Form”>

</form>

Generally, you would expect the person to enter in their first name and submit the form. Nevertheless, this is where the malicious actors exploit poorly constructed site code to their own advantage. Let’s assume this form inserts a new record into the site’s tables. The subsequent SQL code serves as an example of an INSERT statement:

insert into customer (first_name) values (‘ +

$_POST[“first_name”] + ‘);

The aforementioned code assembles a SQL statement from the form’s first_name variable. By chance, the syntax deployed is PHP, though this approach works with any language. The semicolon abolishes the statement, permitting you to establish numerous SQL statements within the same line of code.

The secret to SQL injection involves the apostrophe character, which initiates and closes string values in SQL. Black hat hackers precipitately cease strings and run their own SQL statements.

Let’s imagine that the hacker filled in the subsequent value into the form’s first_name input text book:

‘); select * from customer; —

The above example would then construct the subsequent SQL statement and run it on the site’s database:

insert into customer (first_name) values (“); select

* from customer; —

‘);

Depending on whether you’re a beginner or a seasoned veteran, these examples can be burdensome to grasp. Note that there are two apostrophe characters created in the INSERT statement.

The actor’s SQL statement embeds a blank value into the first_name column, still, then the statement is abolished with a SELECT statement affixed to the end. The SELECT statement then regains all of the data in the site’s customer table. The purpose behind this SQL injection attack vector is to steal the site’s data.

An example of a SQL Injection. SQL Injections come in all flavors.

Actors may also choose to delete the data, which indicates that you have to recoup data from backups. The actor can also replace the SELECT statement with the subsequent SQL code:

drop table customer;

Constructing the SQL statement, you presently have the subsequent code:

insert into customer (first_name) values (“); drop

table customer; —

‘);

Lol. Funny, right?

The “drop table” statement entirely erases the table from the website’s database. The only method to recoup the data is to retrieve it from your backups. If the site’s backup is one week old, then the webmaster just lose one week’s worth of data. This problem can be extremely detrimental to the owner’s business, particularly if they work with orders.

How To Protect Websites From SQL Injection Attacks (SQLi)

Mitigation
Use Stored Procedures And Avoid Dynamic SQL

 

 

 

 

 

 

 

Even web developers who believe they’ve protected a website from SQL injection attack vectors may end up being amazed when a black hat hacker discovers a security flaw.

The ideal way to defend against SQL injection (SQLi) is to use stored procedures. These are called “prepared statements” in PHP. Stored procedures are pre-designed SQL functions that a developer may reuse throughout the whole website code. They make it quicker to create sites that utilize backend databases since the developer doesn’t need to recreate SQL code for every page. Initially, stored procedures do take more time to set up. Therefore, most programmers decide to select faster means of development, constructing dynamic statements like the ones used in our typical SQL injection examples. Hence, it’s recommended to avoid using dynamic SQL whenever possible.

How Stored Procedures Protect Against SQLi

When a malicious actor tries to use SQL injection, and the programmer uses stored procedures, the apostrophe characters are sent as literals. This signifies that rather than abolishing a string and executing malicious SQL, the database inserts the apostrophe as part of the data’s value. Every programming language contains its own structure of stripping or escaping special characters in SQL statements. The programmer needs to employ these functions when he doesn’t employ stored procedures in dynamically built SQL code. For example, the majority of WordPress developers utilize dynamically built SQL statements in their plugins. Poorly created SQL statements are the primary reason why WordPress is continually an easy target for hackers.

Use A Web Application Firewall

Implementing a web application firewall (WAF) will supply SQLi protection to the web applications which will also shield the web server. Some easily deployable cloud/hardware appliances/ WAF solutions include Cloudflare, Incapsula, Akamai, F5, Fortinet, Sucuri, Cloudbric (Penta Security Systems), Citrix, Barracuda Networks, Ergon Informatik, NSFOCUS, Venustech, and DenyAll. Some of these security vendors have a stronger market presence in Europe or China.

Make Sure To Keep Web Applications Updated

For instance, if a webmaster is responsible for managing a WordPress site then remembering to keep the installation up-to-date when a new version is released is imperative. New versions released by vendors can patch any current security problems. It’s of course also important to update any plugins used.Even popular plugin developers have discovered security vulnerabilities in their software. Hence, try to minimize the number of software used. If the software developer fails to issue new versions and security fixes for their software then it is a very good idea to ditch using it.

Minimize The Number Of Software Used

Even popular plugin developers have discovered security vulnerabilities in their software. Hence, try to minimize the number of software used. If the software developer fails to issue new versions and security fixes for their software then it is a very good idea to ditch using it.

Try To Hack Your Own Website

The developer can use various penetration tools to identify security vulnerabilities like SQLi in a site. This is a very effective way to find any serious security flaws before a malicious actor does. I do comprehensive penetration testing on my site on a regular basis as part of an effort in ensuring that my web property remains secure from black hat hackers. Many of the hackers, especially script kiddies, use automated scripts to find whether a site is vulnerable. These penetration tools deploy identical techniques. Lastly, when the developer is performing their penetration testing on the web property he is assigned to secure, he has to remember to use penetration tools that have numerous SQL scripts which identify simple and complicated SQL injection vulnerabilities.

Conclusion

SQL injection attacks are a deliberate security vulnerability on the Internet. Thus, it is the webmaster’s responsibility to ensure that the site is secured. If webmasters do not think their site is a target, they’re wrong.

Black hat hackers utilize scripts to automate searches on the Internet to locate vulnerable sites. It doesn’t take too much time to protect from SQL injections, though it may take days or even weeks to recoup if the site is successfully compromised.

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