SQL Injection

SQL Injection (SQLi) is a web security vulnerability that allows an attacker to interfere with the queries an application makes to its database. It typically involves injecting malicious SQL code into a query, which can manipulate the database to execute unintended commands.

How an Attacker Can Exploit SQL Injection:

1. Injection via Input Fields: Attackers insert malicious SQL code into input fields (e.g., login forms, search boxes) that are concatenated into SQL queries.

2. URL Manipulation: Attackers modify query parameters in the URL to include SQL code.

3. Cookies: Malicious SQL code can be inserted into cookies that are used in SQL queries.

4. HTTP Headers: SQL code can be injected through HTTP headers such as User-Agent.

Potential Damage:

1. Data Theft: Unauthorized access to sensitive data (e.g., user credentials, personal information).

2. Data Manipulation: Modification or deletion of data.

3. Authentication Bypass: Gaining unauthorized access by bypassing login mechanisms.

4. Database Corruption: Destroying or corrupting database data.

5. Escalation of Privileges: Gaining administrative access to the database server.

6. Remote Code Execution: In some cases, executing commands on the server hosting the database.

Brief Use Cases:

1. Extracting User Data: Accessing usernames and passwords stored in the database.

2. Dumping Database: Retrieving the entire contents of a database.

3. Administrative Operations: Performing administrative operations like adding or deleting users.

4. Compromising Systems: Escalating privileges to control the database server and potentially the underlying operating system.

Protection Measures and Implementation:

1. Parameterized Queries (Prepared Statements):

   • Description: Ensures that SQL code is defined separately from the data.

   • Implementation:

     # Example in Python using SQLite
     import sqlite3
     
     conn = sqlite3.connect('example.db')
     cursor = conn.cursor()
     cursor.execute("SELECT * FROM users WHERE username = ? AND password = ?", (username, password))

   • Requirements: Database and application support for parameterized queries.

2. Stored Procedures:

   • Description: Encapsulates SQL queries within the database, reducing direct SQL manipulation.

   • Implementation:

     -- Example in SQL Server
     CREATE PROCEDURE AuthenticateUser
     @username NVARCHAR(50),
     @password NVARCHAR(50)
     AS
     BEGIN
         SELECT * FROM users WHERE username = @username AND password = @password
     END

   • Requirements: Database support for stored procedures.

3. Input Validation:

   • Description: Validates and sanitizes user input to ensure it adheres to expected formats.

   • Implementation:

     # Example in Python
     import re
     
     def validate_input(user_input):
         if re.match("^[a-zA-Z0-9_]+$", user_input):
             return True
         else:
             return False

   • Requirements: Implementation of robust input validation functions.

4. Escaping Inputs:

   • Description: Escapes special characters in user inputs to neutralize any SQL code.

   • Implementation:

     // Example in PHP
     $username = mysqli_real_escape_string($conn, $_POST['username']);
     $password = mysqli_real_escape_string($conn, $_POST['password']);

   • Requirements: Functions or libraries for escaping inputs.

5. Web Application Firewalls (WAF):

   • Description: Inspects and filters traffic to block malicious SQL injection attempts.

   • Implementation: Configure a WAF like ModSecurity with rules to detect and prevent SQLi.

   • Requirements: Deployment and configuration of a WAF.

6. Least Privilege Principle:

   • Description: Restrict database user permissions to the minimum necessary for the application to function.

   • Implementation:

     -- Example in MySQL
     CREATE USER 'appuser'@'localhost' IDENTIFIED BY 'password';
     GRANT SELECT, INSERT, UPDATE ON database.* TO 'appuser'@'localhost';

   • Requirements: Proper database user role configuration.

By implementing these protective measures, you can significantly reduce the risk of SQL Injection attacks on your web applications.