CWE-46: Path Equivalence: 'filename ' (Trailing Space)

What is Path Equivalence: 'filename ' (Trailing Space)?

• Overview: This vulnerability occurs when a software product accepts path input with trailing spaces, such as 'filename ', without proper validation. This oversight can lead to ambiguous path resolution, allowing attackers to navigate the file system in unintended ways or access arbitrary files.

• Exploitation Methods:

• Attackers can exploit this by appending or inserting trailing spaces in file or directory names, potentially bypassing security checks.
• Common attack patterns include directory traversal attacks and unauthorized access to restricted files by using paths with trailing spaces.

• Security Impact:

• Direct consequences include unauthorized file access or modification, potentially leading to data breaches.
• Potential cascading effects include privilege escalation if sensitive system files are accessed.
• Business impact may involve loss of customer trust, legal repercussions, and financial losses due to data leaks or system compromise.

• Prevention Guidelines:

• Specific code-level fixes include stripping trailing spaces from file and directory paths before processing.
• Security best practices involve validating and normalizing file paths consistently across the application.
• Recommended tools and frameworks include static analysis tools that can detect path manipulation vulnerabilities and frameworks that offer secure path handling utilities.

Corgea can automatically detect and fix Path Equivalence: 'filename ' (Trailing Space) 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 specified

Vulnerable Code Example

const fs = require('fs');

function readFile(filePath) {
    // Vulnerable: accepts file path with trailing spaces, leading to path equivalence issues
    if (fs.existsSync(filePath)) {
        return fs.readFileSync(filePath, 'utf8');
    } else {
        return "File does not exist.";
    }
}

// Example usage:
// This could be exploited if 'file.txt ' exists and the system treats it differently from 'file.txt'
console.log(readFile("file.txt "));

How to fix Path Equivalence: 'filename ' (Trailing Space)?

To fix this issue, trim the input path to remove any leading or trailing whitespace before performing file operations. This ensures consistent treatment of file paths and prevents potential path equivalence issues. Additionally, it is good practice to validate and sanitize path inputs thoroughly and use libraries that handle path resolution securely.

Fixed Code Example

const fs = require('fs');

function readFile(filePath) {
    // Securely normalize the path by trimming whitespace
    const normalizedPath = filePath.trim();
    
    // Continue with file operations on the normalized path
    if (fs.existsSync(normalizedPath)) {
        return fs.readFileSync(normalizedPath, 'utf8');
    } else {
        return "File does not exist.";
    }
}

// Example usage:
// This will now treat 'file.txt' and 'file.txt ' as the same file
console.log(readFile("file.txt "));

In both examples, the key security control is normalizing the file path by removing any trailing spaces before using it in file operations. This effectively mitigates the CWE-46 vulnerability by ensuring path equivalence.