CWE-1239: Improper Zeroization of Hardware Register

What is Improper Zeroization of Hardware Register?

• Overview: Improper Zeroization of Hardware Register occurs when a hardware product fails to correctly clear sensitive information from its registers when the hardware block user changes, leaving sensitive data accessible to unauthorized users.

• Exploitation Methods:

• Attackers can access residual sensitive data in hardware registers when no zeroization occurs.
• Common attack patterns include monitoring changes in operating modes or conditions to intercept data left in registers.

• Security Impact:

• Direct consequences include unauthorized access to sensitive information such as passwords and encryption keys.
• Potential cascading effects involve broader data breaches or system compromises if attackers leverage exposed data.
• Business impact includes loss of customer trust, legal consequences, and financial losses due to data breaches.

• Prevention Guidelines:

• Implement proper zeroization techniques to ensure registers are cleared when the hardware block user changes.
• Adopt security best practices by integrating zeroization procedures in hardware designs, especially in cryptographic hardware.
• Use recommended tools and frameworks like FIPS-140-2 standards to guide secure implementation of hardware zeroization practices.

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Technical Details

Likelihood of Exploit: Not specified

Affected Languages: Not Language-Specific

Affected Technologies: System on Chip

Vulnerable Code Example

// Simulate a hardware register using a global variable
var hardwareRegister = "sensitiveData"

// Function to simulate a change in the user of the hardware block
func switchUser() {
    // Vulnerable: The hardware register is not cleared before switching users
    // This can lead to leakage of sensitive information to the new user
    fmt.Println("Switching user without zeroizing register:", hardwareRegister)
}

Explanation

In this vulnerable code example, a global variable hardwareRegister is used to simulate a hardware register. The function switchUser is called to simulate a change in the user of the hardware block. However, the hardware register is not cleared before switching users, which can lead to sensitive information leakage to the new user. This demonstrates improper zeroization of hardware registers.

How to fix Improper Zeroization of Hardware Register?

Improper zeroization of hardware registers can lead to sensitive data being exposed when the user of a hardware block changes. To fix this issue, it's crucial to ensure that any sensitive information is completely cleared from hardware registers before switching users. This can be done by setting the register to a default or zero value. In Go, this involves setting the variable representing the hardware register to an empty string or another non-sensitive default value. Additionally, it's good practice to use a function for zeroization to ensure consistency and reduce the possibility of errors.

Fixed Code Example

// Simulate a hardware register using a global variable
var hardwareRegister = "sensitiveData"

// Function to zeroize the hardware register
func zeroizeRegister() {
    hardwareRegister = "" // Properly zeroizing the register to prevent data leakage
}

// Function to simulate a change in the user of the hardware block
func switchUser() {
    zeroizeRegister() // Ensure the register is cleared before switching users
    fmt.Println("Switching user after zeroizing register:", hardwareRegister)
}

Explanation

In this fixed code example, the zeroizeRegister function is introduced, which sets the hardwareRegister to an empty string, effectively clearing any sensitive data. This function is called in switchUser before switching users to ensure that no sensitive data is leaked. This approach promotes a secure handling of hardware registers by implementing proper zeroization, which is a critical step in secure hardware management. The comments and structure clearly demonstrate the vulnerability and the fix, following best practices for secure coding in Go.