CWE-56: Path Equivalence: 'filedir*' (Wildcard)

What is Path Equivalence: 'filedir*' (Wildcard)?

• Overview: This vulnerability arises when software accepts path inputs containing asterisks as wildcards (e.g., 'filedir*') without sufficient validation. This can lead to ambiguous path resolution, allowing attackers to navigate the file system and access unintended files or directories.

• Exploitation Methods:

• Attackers can exploit this by crafting inputs that manipulate file paths to include sensitive directories or files.
• Common techniques include directory traversal attacks, where path inputs are manipulated to access files outside the intended directory.

• Security Impact:

• Direct consequences include unauthorized access to sensitive files or directories.
• Cascading effects may involve data breaches or system compromise if critical files are accessed or modified.
• Business impact includes potential data loss, legal liabilities, and reputational damage.

• Prevention Guidelines:

• Implement strict input validation to sanitize and validate path inputs before processing.
• Avoid using wildcards in path inputs where possible, or handle them with clear constraints and controls.
• Utilize security libraries or frameworks that provide safe file path handling functions.
• Regularly review and test code for path traversal vulnerabilities using static analysis tools.

Corgea can automatically detect and fix Path Equivalence: 'filedir*' (Wildcard) 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

import os
import glob

def read_files(directory):
    # Vulnerable: Uses wildcards in file paths without validation
    # This allows for path equivalence issues where unintended files may be read
    files = glob.glob(os.path.join(directory, 'filedir*'))
    for file in files:
        with open(file, 'r') as f:
            print(f.read())
    
# Example usage
read_files('/var/data/')  # Potentially dangerous if /var/data/ can be controlled by the user

Explanation

• Wildcard Usage: The use of glob.glob(os.path.join(directory, 'filedir*')) can match unintended files, leading to security issues if the directory is user-controlled.
• Lack of Validation: There is no validation of the files being read, which could lead to reading sensitive or unintended files if the directory is not properly secured.

How to fix Path Equivalence: 'filedir*' (Wildcard)?

To fix this vulnerability, the code should incorporate strong input validation, avoid wildcards, and use a whitelist approach to ensure only intended files are accessed. Here's how:

1. Input Validation: Verify that the directory exists and is a valid directory.
2. Use of a Whitelist: Define a list of explicitly allowed filenames.
3. Avoiding Wildcards: Instead of using wildcards, iterate through a predefined list of files.
4. Sanitization: Ensure that the directory path is sanitized to prevent directory traversal.
5. Use Secure Libraries: Utilize libraries that handle file operations securely.

Fixed Code Example

import os

def read_files(directory):
    # Validate and sanitize the directory input
    if not os.path.exists(directory) or not os.path.isdir(directory):
        raise ValueError("Invalid directory path provided")

    # Whitelist of allowed files
    allowed_files = ['filedir1.txt', 'filedir2.txt']
    for filename in allowed_files:
        file_path = os.path.join(directory, filename)
        # Securely check if the file exists
        if os.path.isfile(file_path):
            with open(file_path, 'r') as f:
                print(f.read())

# Example usage
read_files('/var/data/')  # Now restricted to known files in the directory

Explanation

• Input Validation: The code checks if the directory exists and is a directory using os.path.exists() and os.path.isdir().
• Whitelist: Only files listed in allowed_files are accessed, preventing unintended file access.
• Avoiding Wildcards: The code no longer uses wildcards, reducing the risk of matching unintended files.
• Secure File Check: os.path.isfile() ensures that only existing files are accessed, further securing the operation.

This improved example demonstrates a secure approach to handling file paths, mitigating the risks associated with path equivalence and wildcard usage.