CWE-1259: Improper Restriction of Security Token Assignment

What is Improper Restriction of Security Token Assignment?

• Overview: CWE-1259 refers to a vulnerability where a System-On-A-Chip (SoC) fails to adequately protect the assignment of Security Tokens. These tokens are critical for distinguishing which actions are permitted by different entities within a system. Improper protection allows malicious entities to manipulate these tokens, potentially spoofing actions from trusted agents.

• Exploitation Methods:

• Attackers can exploit this vulnerability by accessing and modifying Security Tokens, allowing them to perform unauthorized actions.
• Common attack patterns include token spoofing, where an attacker assigns themselves elevated privileges, and token tampering, where token values are altered to bypass security checks.

• Security Impact:

• Direct consequences include unauthorized access or modification of system functions, data breaches, and privilege escalation.
• Potential cascading effects involve compromised system integrity, disclosure of sensitive information, and unintended system behavior.
• Business impact can be severe, leading to loss of customer trust, financial loss, and legal ramifications due to data protection violations.

• Prevention Guidelines:

• Implement strict access controls to ensure only trusted components can assign or modify Security Tokens.
• Use cryptographic techniques to protect the integrity and authenticity of Security Tokens.
• Regularly audit and monitor token assignments and access logs for suspicious activities.
• Employ tools and frameworks that provide robust security token management and enforce least privilege principles.

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Technical Details

Likelihood of Exploit: Not specified

Affected Languages: Not Language-Specific

Affected Technologies: Not Technology-Specific, System on Chip

Vulnerable Code Example

class TokenManager:
    def __init__(self):
        self.tokens = {}  # Dictionary to store tokens for users

    def assign_token(self, user_id, token):
        # Vulnerable code: improperly protects token assignment
        self.tokens[user_id] = token  # Direct assignment without validation

In this example, the assign_token method directly assigns a token to a user without any validation or restrictions. This can lead to security issues if an attacker can assign arbitrary tokens to users, potentially escalating privileges or impersonating another user.

How to fix Improper Restriction of Security Token Assignment?

To fix this vulnerability, you should implement proper validation and restrictions on token assignments. This involves verifying that the token being assigned is valid and appropriate for the user. Additionally, ensure that tokens are generated securely and cannot be easily guessed or manipulated by an attacker.

• Validate Tokens: Ensure that any token being assigned is checked against a known set of valid tokens.
• Use Secure Tokens: Generate tokens using secure random generators to prevent predictability.
• Restrict Token Assignment: Implement logic to verify the user's identity and permissions before assigning tokens.

Fixed Code Example

import secrets

class TokenManager:
    def __init__(self):
        self.tokens = {}
        self.valid_tokens = set()  # Set of valid tokens

    def generate_secure_token(self):
        # Generate a secure token using a strong random generator
        token = secrets.token_hex(16)
        self.valid_tokens.add(token)
        return token

    def assign_token(self, user_id, token):
        # Fixed code: validate token before assignment
        if token in self.valid_tokens:
            self.tokens[user_id] = token
            self.valid_tokens.remove(token)  # Prevent token reuse
        else:
            raise ValueError("Invalid or unauthorized token")

In the fixed version, we added the following improvements:

1. Secure Token Generation: We use the secrets module to generate cryptographically secure tokens. This makes it difficult for attackers to predict or forge tokens.
2. Token Validation: Before assigning a token to a user, the token is checked against a set of valid tokens to ensure it is authorized for use.
3. Token Revocation: Once a token is assigned, it is removed from the valid tokens set to prevent reuse, which helps in maintaining token integrity and security.

This approach ensures that only authorized and valid tokens are assigned to users, reducing the risk of improper token assignments.