Imagine an application that doesn’t contain any data. You most likely read that sentence and thought, “Then that application is pretty pointless from a business perspective.” Business applications offer value precisely because users can ask questions and get answers. However, the application typically needs to query a database to get those answers and SQL is one of the more common methods. Unfortunately, as with nearly every other programming language, threat actors target vulnerabilities in SQL queries to steal sensitive information.
With this SQL injection cheat sheet, you can learn about a SQL injection attack and how to protect your application from one.
What is SQL Injection?
In an SQL injection attack, threat actors insert or “inject” data into an SQL query that enables them to
- Read sensitive data
- Modify data
- Execute operations
- Recover file contents
- Issue commands
When programming in SQL, developers often combine two or more strings, a sequence of characters representing a constant or variable. When joining these together, known as a string concatenation, developers can accidentally introduce vulnerabilities, allowing attackers to change a variable’s value and how the application interacts with the database.
Depending on the attackers’ sophistication, some actions that they can take include:
- Spoofing identities
- Tampering with data
- Voiding transactions
- Changing balances
- Accessing data
- Deleting data
- Gaining administrative access to the database server
Best Coding Practices to Mitigate SQL Attack Threats
SQL injections are only one type of injection attack, one of the OWASP Top 10 Web Application Security Risks. As a developer, you should implement some coding best practices to protect your application.
Prepared statements with parameterized queries
Prepared statements separate the database SQL code from the data using a pre-compiled template with constant values. Since the database does all parsing, compiling, and optimization performance without executing the query, parameter values are transmitted later. Using an anonymized placeholder rather than defining the values within the query gives attackers no visibility into the application’s logic.
Stored procedures
When implemented safely, stored procedures impact application security like prepared statements. However, where the application stores the prepared statement, the database stores the stored procedure and then exposes it to the application. Stored procedures should not include dynamic SQL generation to ensure a secure implementation.
Since stored procedures and prepared statements work similarly, you should decide which approach to use then use it consistently.
Allow-list input validation
Input validation ensures that properly formed data enters the workflow. Allow-list validation defines the authorized user-provided input fields. Often, programmers can turn part of the SQL query into a parameter known as a bind variable. However, in some cases, bind variables may not work, like for:
- Table names
- Column names
- Order indicators
Input validation provides added defense when users must supply parameter values to ensure they map to the appropriate database location and prevent unvalidated user input from being in the query.
Additionally, input validation provides an additional layer of defense in all cases.
Escaping all user-supplied input
User inputs are strings that can provide attackers visibility into the application’s logic. Every database management system (DBMS) has its own set of escape characters that tell the processing engine to evaluate control characters as text, not code. By changing how the database reads the input, attackers can’t manipulate the queries in a way that changes the code.
As the least effective defensive measure, escaping user-supplied inputs should be a last resort because the escape characters are database-specific and cannot prevent SQL injections in all cases. Usually, programmers use this technique to rework legacy code because input validation becomes cost-prohibitive.
Reviewing Code for SQL Injection Vulnerabilities
To test for SQL injection vulnerabilities, you need to understand how and when the application talks to the database, with typical examples like the following:
- Authentication forms: users inputting credentials that get checked against a database
- Search engines: users inputting search terms to extract information from a database
- E-commerce site: product information being pulled from a database
Some suggestions of issues to look for when reviewing your code include:
- Missing validations and sanitizations
- Manually checking for vulnerable endpoints
- Limiting when to use database calls
- Reviewing strings to ensure that they use placeholders rather than literal values
- Ensuring that no one can insert file paths into a parameter
Qwiet AI: Automated Vulnerability Testing to Mitiate SQL Injection Risks
Manually reviewing your code for potential SQL vulnerabilities is time-consuming and prone to human error risks. With Qwiet AI’s preZero platform, you can check for vulnerabilities in millions of lines of code in minutes, enabling you to get the accurate and detailed findings necessary to protect your application from SQL injections.
PreZero identifies vulnerabilities and then adds context to help you prioritize remediation activities by giving you visibility into the ones attackers can actually exploit. Using Qwiet AI, you can eliminate thousands of false positives for a noise-free list that prioritizes your riskiest code, enabling faster time-to-market.
Take our preZero platform for a free spin to see how Qwiet AI can help you identify and remediate risky SQL vulnerabilities.