CWE-281: Improper Preservation of Permissions

What is Improper Preservation of Permissions?

• Overview: Improper Preservation of Permissions occurs when software fails to maintain or incorrectly maintains object permissions during operations like copying, restoring, or sharing, potentially resulting in less restrictive access than intended.

• Exploitation Methods:

• Attackers can exploit this vulnerability by gaining unauthorized access to sensitive data or functionalities due to overly permissive settings.
• Common attack patterns include accessing files or settings with default or inherited permissions that should have been more restrictive.

• Security Impact:

• Direct consequences of successful exploitation include unauthorized access to sensitive data and operations.
• Potential cascading effects involve privilege escalation, data breaches, and unauthorized system control.
• Business impact may include legal penalties, loss of customer trust, and financial damage due to data leaks.

• Prevention Guidelines:

• Specific code-level fixes include explicitly setting permissions after operations like copying or restoring objects.
• Security best practices involve regularly auditing permissions and using least privilege principles.
• Recommended tools and frameworks include automated security testing tools that check for permission misconfigurations and logging frameworks that track permission changes.

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Technical Details

Likelihood of Exploit: Not specified

Affected Languages: Not Language-Specific

Affected Technologies: Not specified

Vulnerable Code Example

const fs = require('fs');

function copyFile(source, destination) {
    // Copying a file without preserving the file permissions
    fs.copyFileSync(source, destination);  
    // The destination file might have different permissions than the source,
    // which can lead to potential security issues if the default permissions are too permissive.
}

How to fix Improper Preservation of Permissions?

In Node.js, you can manually set the file permissions after copying. After using fs.copyFileSync, retrieve the original file's permissions using fs.statSync and then apply those permissions to the new file using fs.chmodSync. This ensures that the file permissions are preserved and do not default to potentially insecure settings.

Fixed Code Example

const fs = require('fs');

function copyFile(source, destination) {
    // Copy the file content
    fs.copyFileSync(source, destination);
    
    // Retrieve the original file permissions
    const sourcePermissions = fs.statSync(source).mode;  
    
    // Apply the original permissions to the destination file
    fs.chmodSync(destination, sourcePermissions);  
    // This ensures that the destination file has the same permissions as the source file,
    // preventing any security issues related to improper permission settings.
}

These examples demonstrate how improperly preserving file permissions can lead to security vulnerabilities, such as unauthorized access or modification of files. The fix involves using appropriate methods to ensure permissions are maintained during file operations, thereby mitigating potential security risks.