CWE-1267: Policy Uses Obsolete Encoding

What is Policy Uses Obsolete Encoding?

• Overview: The vulnerability CWE-1267, "Policy Uses Obsolete Encoding," occurs when a product employs an outdated encoding mechanism to implement access controls, potentially leading to security weaknesses.

• Exploitation Methods:

• Attackers can exploit this vulnerability by crafting transactions that bypass or manipulate the obsolete encoding to gain unauthorized access.
• Common attack patterns include replay attacks, where old transactions are reused, and encoding downgrades, where attackers force the system to use weaker encoding schemes.

• Security Impact:

• Direct consequences of successful exploitation include unauthorized access to sensitive data or system functions.
• Potential cascading effects involve compromised system integrity, data breaches, and unauthorized control over system operations.
• Business impact may include loss of customer trust, legal liabilities, and financial losses due to data breaches or service disruptions.

• Prevention Guidelines:

• Specific code-level fixes include updating the encoding mechanism to a more secure, currently trusted standard.
• Security best practices involve regularly reviewing and updating security policies, implementing strong encryption and access control measures, and conducting security audits.
• Recommended tools and frameworks include using secure coding libraries that support modern encoding standards and employing automated tools to identify outdated encoding practices.

Corgea can automatically detect and fix Policy Uses Obsolete Encoding 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

Python Example

import base64

def is_authorized(user_token):
    # Vulnerable: Using Base64 encoding as an access control mechanism
    # Base64 is not secure as it is merely an encoding, not encryption
    allowed_token = base64.b64encode(b'secret_admin_token').decode('utf-8')
    return user_token == allowed_token

# Example usage
print(is_authorized('c2VjcmV0X2FkbWluX3Rva2Vu'))  # True if token matches

How to fix Policy Uses Obsolete Encoding?

The vulnerability arises from using Base64 encoding for access control. Base64 is a reversible encoding method, not a secure means of protecting sensitive data. It can easily be decoded, exposing sensitive access control tokens. To fix this, switch to using a secure hashing mechanism or, when necessary, cryptographic libraries that provide proper encryption.

Best Practices:

1. Use Secure Hashing: For storing and comparing tokens, use a cryptographic hash function such as SHA-256.
2. Implement Secure Storage: For sensitive tokens, store them securely using encryption methods instead of reversible encoding.
3. Leverage Environment Variables: Store sensitive tokens as environment variables and access them securely within the application.

Fixed Code Example

import hashlib
import os

def is_authorized(user_token):
    # Fixed: Using a secure hash (SHA-256) for access control
    # This ensures the token cannot be easily reversed or guessed
    allowed_token_hash = hashlib.sha256(b'secret_admin_token').hexdigest()
    user_token_hash = hashlib.sha256(user_token.encode('utf-8')).hexdigest()
    return user_token_hash == allowed_token_hash

# Example usage
print(is_authorized('secret_admin_token'))  # True if token matches

In the fixed version, we use the hashlib library to create a SHA-256 hash of the token for comparison. This approach enhances security by ensuring that sensitive tokens are not stored or compared using reversible encoding methods like Base64, which can easily be decoded by attackers. By using a cryptographic hash function, we ensure that even if the hash is exposed, it cannot be used to retrieve the original token.