CWE-1303: Non-Transparent Sharing of Microarchitectural Resources

What is Non-Transparent Sharing of Microarchitectural Resources?

• Overview: Non-Transparent Sharing of Microarchitectural Resources (CWE-1303) occurs when hardware components that handle multiple execution contexts, like caches and branch predictors, do not isolate these contexts as expected, allowing information to be shared inadvertently.

• Exploitation Methods:

• Attackers can exploit this vulnerability through side-channel attacks, observing the behavior of shared resources to infer sensitive data.
• Common attack patterns include cache-timing attacks, branch prediction attacks, and exploiting speculative execution to leak data.

• Security Impact:

• Direct consequences include unauthorized access to sensitive information, such as cryptographic keys or personal data.
• Potential cascading effects involve broader system compromise if sensitive data is used to escalate privileges or further penetrate networks.
• Business impact may involve data breaches, loss of consumer trust, regulatory fines, and financial losses.

• Prevention Guidelines:

• Specific code-level fixes are challenging due to the hardware nature of the issue, but developers can use constant-time algorithms to minimize data-dependent variations in execution.
• Security best practices include applying patches and firmware updates from processor manufacturers, and using defensive programming techniques.
• Recommended tools and frameworks involve leveraging security features in modern CPUs, such as hardware isolation technologies, and employing static and dynamic analysis tools to detect vulnerabilities in software.

Corgea can automatically detect and fix Non-Transparent Sharing of Microarchitectural Resources in your codebase. [Try Corgea free today](https://corgea.app).

Technical Details

Likelihood of Exploit: Not specified

Affected Languages: Not Language-Specific

Affected Technologies: Not Technology-Specific

Vulnerable Code Example

const http = require('http');
const crypto = require('crypto');

// A function to simulate sensitive data processing
function processSensitiveData(data) {
    // Vulnerable: Using shared cache without isolation
    // Attackers could exploit cache side-channels to infer sensitive data
    const hash = crypto.createHash('sha256').update(data).digest('hex');
    return hash;
}

http.createServer((req, res) => {
    if (req.url === '/process-data') {
        // Simulate processing sensitive data
        const sensitiveData = 'user_secret';
        const result = processSensitiveData(sensitiveData);
        res.end(result);
    } else {
        res.end('Hello World');
    }
}).listen(3000);

Explanation of the Vulnerability

• Shared Cache Without Isolation: The code processes sensitive data (user_secret) using a shared resource (cache) without any form of isolation. This can lead to side-channel attacks, where an attacker could potentially infer the sensitive data by analyzing cache usage patterns.
• Lack of Constant-Time Operations: The hashing operation does not use a constant-time algorithm, which could be exploited through timing attacks to deduce information about the input data.

How to fix Non-Transparent Sharing of Microarchitectural Resources?

To address the vulnerability of non-transparent sharing of microarchitectural resources, it is crucial to minimize the risk of side-channel attacks by isolating the processing of sensitive data. One effective method is to use constant-time algorithms and avoid shared resources when handling sensitive operations. Additionally, consider using hardware-based isolation technologies, such as Intel's SGX or ARM's TrustZone, which provide enclaves for secure processing.

In this example, the processing of sensitive data should be modified to use a constant-time algorithm to prevent timing and cache side-channel attacks. Additionally, consider running sensitive operations on dedicated hardware or isolated environments to further mitigate the risks.

Fixed Code Example

const http = require('http');
const crypto = require('crypto');

// A function to simulate sensitive data processing with constant-time algorithm
function processSensitiveData(data) {
    // Fixed: Use a constant-time comparison to mitigate side-channel attacks
    // Generate a hash of the data
    const hash = crypto.createHash('sha256').update(data).digest();
    // Use a constant-time comparison with a known value
    const isValid = crypto.timingSafeEqual(hash, Buffer.from('expected_hash_value', 'hex'));
    return isValid ? 'Valid' : 'Invalid';
}

http.createServer((req, res) => {
    if (req.url === '/process-data') {
        // Simulate processing sensitive data
        const sensitiveData = 'user_secret';
        const result = processSensitiveData(sensitiveData);
        res.end(result);
    } else {
        res.end('Hello World');
    }
}).listen(3000);

Explanation of the Fix

• Constant-Time Algorithm: The fixed code uses crypto.timingSafeEqual to perform a constant-time comparison of the hashed value against a known expected value. This approach helps prevent timing attacks by ensuring that the execution time of the comparison is independent of the input data.
• Isolation and Dedicated Resources: Although not shown in code, it is recommended to use hardware-based isolation for processing sensitive data. This might involve using virtual machines, containers, or hardware enclaves to ensure that sensitive operations do not share microarchitectural resources with potentially malicious processes.

By implementing these changes, you reduce the risk of attackers exploiting shared microarchitectural resources to infer sensitive information through side-channel attacks.