Command Injection

What is Command Injection?

• Command Injection is a type of security vulnerability where an attacker can execute arbitrary commands on a host operating system via a vulnerable application.

• It typically occurs in web applications that improperly process user input to execute system-level commands.

How Does Command Injection Occur?

• Vulnerable Input Processing: When user input is not properly validated or sanitized, and directly used in a system command.

• Commonly Affected Languages/Technologies: PHP, Java, Python, Shell scripts, SQL databases with system command functions.

Examples of Command Injection

• A web form that takes a user input (like a username) and uses it in a system command without proper validation.

• URL parameters or HTTP headers that are concatenated directly into system commands.

Basic Example

• Unsafe code in PHP: shell_exec('ping ' . $_GET['ip']);

• In this example, if an attacker inputs 8.8.8.8; rm -rf /, it could lead to the execution of a harmful command (rm -rf /).

Impact

• Data Breach: Unauthorized access to or theft of data.

• System Compromise: Gain control over the host system.

• Denial of Service: Disrupt services by executing resource-intensive commands.

Prevention and Mitigation

• Input Validation: Strictly validate user inputs for expected formats.

• Use Safe APIs: Use language-specific safe APIs that abstract command execution.

• Escaping Inputs: Properly escape special characters in user inputs.

• Least Privilege Principle: Run applications with the least privileges necessary.

• Regular Security Auditing: Regularly audit code and applications for vulnerabilities.

Testing for Command Injection

• Manual Testing: Attempt to input system commands through the application.

• Automated Tools: Use security scanning tools like OWASP ZAP, Burp Suite.

• Code Review: Regularly review code for potential vulnerabilities.