CWE-1256: Improper Restriction of Software Interfaces to Hardware Features

What is Improper Restriction of Software Interfaces to Hardware Features?

• Overview: The vulnerability occurs when software interfaces to hardware features like power and clock management are insufficiently restricted, allowing for unauthorized modifications or observations of hardware components.

• Exploitation Methods:

• Attackers can exploit this vulnerability by manipulating device voltage and frequency to inject faults or gather side-channel information.
• Common attack patterns include fault injection to bypass security checks and side-channel attacks to extract sensitive data.

• Security Impact:

• Direct consequences include unauthorized access or data leakage through fault injection and side-channel analysis.
• Potential cascading effects include compromised system integrity and exposure of cryptographic keys.
• Business impact can involve loss of customer trust, legal repercussions, and significant financial loss due to data breaches.

• Prevention Guidelines:

• Implement strict access control measures for hardware control interfaces and limit their exposure.
• Follow security best practices such as input validation, error handling, and regular security audits.
• Use recommended tools and frameworks that provide secure APIs for hardware interface management and monitor for unusual activity.

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Technical Details

Likelihood of Exploit: Not specified

Affected Languages: Not Language-Specific

Affected Technologies: Not Technology-Specific, Memory Hardware, Power Management Hardware, Clock/Counter Hardware

Vulnerable Code Example

import subprocess

class DeviceController:
    def __init__(self):
        # Directly executing a shell command to control hardware features
        self.control_command = "echo change_power_mode > /dev/hardware"

    def change_power_mode(self, mode):
        # Vulnerability: No validation or restriction on the mode value
        complete_command = f"{self.control_command} {mode}"
        subprocess.call(complete_command, shell=True)

Explanation:

In this vulnerable code example, the DeviceController class is designed to change the power mode of a hardware device by executing a shell command. The key security issue here is the lack of validation and restriction on the mode parameter in change_power_mode. This parameter is directly incorporated into a shell command without any checks, allowing an attacker to execute arbitrary commands. This could potentially lead to unauthorized hardware access or control, as the attacker could inject additional shell commands through the mode parameter.

How to fix Improper Restriction of Software Interfaces to Hardware Features?

To fix this vulnerability, it is crucial to validate and restrict the input parameters that control hardware features. This involves:

1. Input Validation: Ensure that the input to the hardware control interface is strictly validated. Only allow predefined values that are safe and expected.

2. Use of Secure APIs: Avoid directly executing shell commands with user-provided input. Instead, use secure libraries or APIs that abstract hardware interactions and enforce security policies.

3. Least Privilege Principle: Ensure that the process executing the code runs with the least privileges necessary to perform its function, reducing the impact of a potential exploit.

4. Error Handling: Implement comprehensive error handling to ensure that unexpected behavior is logged and managed securely.

Fixed Code Example

import subprocess

class DeviceController:
    def __init__(self):
        # Predefined safe commands for hardware control
        self.allowed_modes = {
            'low_power': 'echo change_power_mode low > /dev/hardware',
            'high_performance': 'echo change_power_mode high > /dev/hardware'
        }

    def change_power_mode(self, mode):
        # Validate the mode and use the safe predefined command
        if mode in self.allowed_modes:
            subprocess.call(self.allowed_modes[mode], shell=True)
        else:
            raise ValueError("Invalid mode specified")

Explanation:

In the fixed code example, the DeviceController class now uses a predefined set of allowed modes (allowed_modes) for changing the power mode. This ensures that only safe and expected commands are executed.

• Input Validation: The change_power_mode method checks if the mode is in the allowed_modes dictionary before executing the command, ensuring that only valid and safe commands are used. This prevents any arbitrary command execution.

• Error Handling: If an invalid mode is specified, a ValueError is raised, which prevents any unauthorized command execution and provides feedback to the caller.

By implementing these changes, the vulnerability is mitigated, and the software interface to hardware features is properly restricted, enhancing the overall security of the application.