CWE-1332: Improper Handling of Faults that Lead to Instruction Skips

What is Improper Handling of Faults that Lead to Instruction Skips?

• Overview: Improper Handling of Faults that Lead to Instruction Skips (CWE-1332) occurs when a device lacks the necessary circuitry or sensors to detect and mitigate the skipping of security-critical CPU instructions, which can alter the intended flow of a program and potentially compromise security.

• Exploitation Methods:

• Attackers can exploit this vulnerability by using fault injection techniques to manipulate the hardware's operating conditions, causing critical instructions to be skipped.
• Common attack patterns include electrical disturbances or environmental changes that the hardware is not designed to handle, leading to altered instruction execution.

• Security Impact:

• Direct consequences include unauthorized actions such as bypassing password checks or skipping authentication procedures.
• Potential cascading effects can involve broader system compromise, as the foundation of security checks is undermined.
• Business impact may include data breaches, loss of customer trust, and potential legal liabilities due to insufficient security measures.

• Prevention Guidelines:

• Specific code-level fixes include implementing redundant security checks and using error detection/correction codes.
• Security best practices involve designing hardware with built-in fault detection and response mechanisms, as well as ensuring operating conditions are monitored and maintained.
• Recommended tools and frameworks include using hardware security modules (HSMs) and platforms that support integrity verification and fault tolerance.

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Technical Details

Likelihood of Exploit: Not specified

Affected Languages: Not Language-Specific

Affected Technologies: System on Chip

Vulnerable Code Example

JavaScript Example

// This function checks user permissions to perform an action.
// It assumes that a failure to retrieve the user roles is benign,
// and allows the action by default, which could lead to instruction skipping.
function checkPermissions(userId, action) {
    let userRoles;
    try {
        userRoles = getUserRolesFromDB(userId); // Fetch roles from database
    } catch (error) {
        console.error("Error retrieving user roles:", error);
        // Improper handling: defaults to allowing the action if there's an error
        return true; // Dangerous: allows action without verifying roles
    }
    
    // Check if the user has the required role for the action
    return userRoles.includes(getRequiredRoleForAction(action));
}

function getUserRolesFromDB(userId) {
    // Simulate DB call
    if (Math.random() < 0.1) throw new Error("Database error"); // Simulate random DB error
    return ["user", "admin"];
}

function getRequiredRoleForAction(action) {
    // Simulate required role retrieval
    return "admin";
}

How to fix Improper Handling of Faults that Lead to Instruction Skips?

The key issue in the vulnerable code is the inappropriate handling of errors when retrieving user roles. By defaulting to allowing action on error, the system inadvertently enables a fault that could lead to instruction skipping, allowing unauthorized actions. Proper handling should ensure that any failure in retrieving user roles results in denying the action unless explicitly verified.

Fix Approach:

1. Fail Securely: Instead of allowing access by default, deny it unless explicitly allowed.
2. Log and Alert: Implement logging and alerting for errors to monitor and respond to potential issues.
3. Graceful Degradation: Ensure that the system handles errors without compromising security, possibly by retrying or using a fallback mechanism.

Fixed Code Example

// Fixed function that checks user permissions to perform an action.
// Properly handles retrieval errors by defaulting to denying the action.
function checkPermissions(userId, action) {
    let userRoles = [];
    try {
        userRoles = getUserRolesFromDB(userId); // Fetch roles from database
    } catch (error) {
        console.error("Error retrieving user roles:", error);
        // Secure handling: default to denying the action on error
        return false; // Secure: denies action unless roles are verified
    }
    
    // Check if the user has the required role for the action
    return userRoles.includes(getRequiredRoleForAction(action));
}

function getUserRolesFromDB(userId) {
    // Simulate DB call
    if (Math.random() < 0.1) throw new Error("Database error"); // Simulate random DB error
    return ["user", "admin"];
}

function getRequiredRoleForAction(action) {
    // Simulate required role retrieval
    return "admin";
}

In this fixed example, the checkPermissions function denies permission by default if an error occurs while retrieving user roles, thus preventing unauthorized access due to instruction skipping. This approach ensures that any errors in fetching roles do not inadvertently grant access to restricted actions.