What potential pitfalls should be considered when using exec() to start external programs in PHP?

One potential pitfall when using exec() in PHP is the risk of command injection attacks if user input is not properly sanitized. To mitigate this risk, always validate and sanitize any user input before passing it to the exec() function. Additionally, limit the commands that can be executed and use absolute paths to the executable files to prevent any unintended execution of malicious commands. 

$user_input = $_POST['user_input'];

// Validate and sanitize user input
$validated_input = filter_var($user_input, FILTER_SANITIZE_STRING);

// Limit the commands that can be executed
$allowed_commands = ['ls', 'cat', 'grep'];
if (in_array($validated_input, $allowed_commands)) {
    $command = '/usr/bin/' . $validated_input; // Use absolute path to executable
    exec($command, $output);
    // Process output as needed
} else {
    echo "Invalid command";
}

Keywords

exec external programs security risks command injection input validation

Related Questions