4 essentials to prevent OS command injection attacks

Injection attacks, one of the most common security threats, are included in the OWASP Top 10 list of most critical web application security risks. The OWASP Top 10 is a standard for web application security that provides a comprehensive list of the most significant risks to web applications. Injection attacks occur when untrusted data is sent to an interpreter as part of a command or query. Attackers can use injection attacks to manipulate the behavior of the interpreter and gain unauthorized access to the system. Injection attacks can take many forms, including SQL injection, LDAP injection, OS command injection, etc.

OS command injection is a type of security vulnerability that arises when an application or system allows an attacker to execute operating system commands by injecting malicious input. This issue can lead to unauthorized access, data breaches, and other security issues.

In this article, we will discuss what OS command injection is, how it works, and provide a C++ demonstration.

How OS command injection works

OS command injection occurs when an application or system allows user input to be included as part of an operating system (OS) command without validating or sanitizing the input. Attackers can manipulate this input to execute malicious commands, which can result in data breaches, system compromise, and other security issues.

To understand how OS command injection works, consider the following example of a C++ program that takes user input to run a system command:

// This program demonstrates a potential OS command injection vulnerability


#include <iostream>
#include <stdlib.h>

using namespace std;

int main()

{
   char command[100];
   cout << "Enter the command: ";
   cin >> command;
   system(command); // Pass the command to the system function, which executes it on the system
 
   return 0;
}

In this program, the user is prompted to enter a command, which is then executed using the system function. This program is vulnerable to OS command injection because it does not validate or sanitize the user input before including it as part of the system command.

An attacker could exploit this vulnerability by entering a malicious command that the system can execute. For example, the attacker could enter the following command:

ls; rm -rf /

This command would execute the ls command, followed by the rm -rf / command, which would delete all files and directories on the system. This example demonstrates the severity of OS command injection vulnerabilities, as they can be used to execute any command the attacker can access.

4 ways to prevent OS command injection attacks

Developers can find and fix vulnerabilities in their code to prevent OS command injection attacks. Follow these 4 best practices:

1. Validate and sanitize user input: Developers should validate and sanitize all user input that will be included as part of a system command. Do this by checking the input for any special characters or commands that could be used to execute malicious commands. This includes restricting input to only the allowed characters, removing any special characters that are not allowed, and ensuring that input is properly encoded.
2. Use safe coding practices: Developers should follow safe coding practices, such as avoiding system commands whenever possible, using safe functions like execvp, and using secure coding techniques like parameter binding.
3. Conduct security testing: Developers should conduct regular security testing of their applications, including automated testing tools and manual testing by security experts. This can help identify any vulnerabilities in the code, including OS Command Injection vulnerabilities.
4. Stay up-to-date on security patches: Developers should stay up-to-date on the latest security patches and updates for the systems and software they use. This can help prevent known vulnerabilities from being exploited.

An example of securing system commands

In C++, the execvp function can be used to safely execute system commands because it requires the user to provide a list of arguments rather than a string that includes the command and arguments. Here is an example of a C++ program that uses execvp to safely execute a system command:

#include <iostream>
#include <unistd.h>

using namespace std;

int main()

{
    char *args[] = {"/bin/ls", "-la", NULL};
    execvp(args[0], args);

    return 0;
}

In this program, the execvp function executes the ls command with the -la option. The command and its arguments are stored in an array of strings, which is then passed to the execvp function. This approach is safer than using the system function because it does not allow the user to include arbitrary commands as part of the system command.

A few OS command injection vulnerabilities were found recently by Red Hat and identified as CVE-2020-14324, CVE-2022-29078, CVE-2019-14905, and CVE-2020-8130. Red Hat's product security team quickly responded to those vulnerabilities, provided fixes, and encouraged developers to follow secure coding practices.

Addressing security vulnerabilities and risks

This article explained how OS command injection vulnerabilities are a serious security risk that can lead to system compromise, data breaches, and other security issues. These vulnerabilities occur when system commands are executed using input from untrusted sources without proper validation or sanitization.

To prevent OS command injection vulnerabilities in their code, developers should follow best practices such as validating and sanitizing user input, using safe coding practices, conducting regular security testing, and staying up-to-date on security patches.

Prioritizing security in the development process is crucial to ensure that user data and systems remain protected from potential attacks. By taking the necessary steps to prevent OS command injection attacks, developers can ensure the security and integrity of their applications and protect against security threats.

Last updated: August 14, 2023