CWE-268: Privilege Chaining

What is Privilege Chaining?

• Overview: Privilege Chaining refers to a security vulnerability where two or more distinct privileges, roles, capabilities, or rights can be combined by an entity to perform actions that are unsafe and would not be permissible without this specific combination.

• Exploitation Methods:

• Attackers can exploit this vulnerability by gaining access to multiple roles or permissions and using them in combination to bypass security restrictions.
• Common attack patterns include role escalation, where an attacker with access to multiple roles can chain their privileges to perform unauthorized actions, and leveraging misconfigured permissions that allow unintended access.

• Security Impact:

• Direct consequences include unauthorized access to sensitive data or critical system functions, potentially leading to data breaches or system compromise.
• Potential cascading effects involve further exploitation of other users or systems, creating a larger security incident.
• Business impact can include financial loss, reputational damage, and legal consequences due to non-compliance with data protection regulations.

• Prevention Guidelines:

• Specific code-level fixes include implementing least privilege principles, ensuring users have only the minimal necessary permissions required for their roles.
• Security best practices involve regularly reviewing and updating privilege assignments, conducting thorough access control audits, and enforcing separation of duties.
• Recommended tools and frameworks include using role-based access control (RBAC) systems, privilege management solutions, and continuous monitoring tools to detect and prevent privilege misuse.

Corgea can automatically detect and fix Privilege Chaining in your codebase. [Try Corgea free today](https://corgea.app).

Technical Details

Likelihood of Exploit: High

Affected Languages: Not Language-Specific

Affected Technologies: Not specified

Vulnerable Code Example

class User:
    def __init__(self, username, role):
        self.username = username
        self.role = role

    def can_edit(self):
        # Check if the user is an editor or admin
        return self.role in ['editor', 'admin']

    def can_delete(self):
        # Check if the user is an admin
        return self.role == 'admin'

def perform_action(user, action_type):
    if action_type == 'edit':
        if user.can_edit():
            print(f"{user.username} is editing the document.")
        else:
            print(f"{user.username} is not authorized to edit.")
    elif action_type == 'delete':
        if user.can_edit() and user.can_delete():
            # Privilege chaining vulnerability: incorrect assumption that editor rights plus delete rights are needed
            print(f"{user.username} is deleting the document.")
        else:
            print(f"{user.username} is not authorized to delete.")

# Example usage
user = User("Alice", "editor")
perform_action(user, "delete")  # Incorrectly allows delete operation

Explanation of the Vulnerability

In the above code, the perform_action function incorrectly checks for both can_edit() and can_delete() privileges for the delete operation. This creates a privilege chaining vulnerability because it assumes that having both edit and delete permissions is necessary for deletion. As a result, a user with editing rights (but not deletion rights) can perform a delete operation, which should be restricted to users with admin rights only.

How to fix Privilege Chaining?

Fixed Code Example

class User:
    def __init__(self, username, role):
        self.username = username
        self.role = role

    def can_edit(self):
        return self.role in ['editor', 'admin']

    def can_delete(self):
        return self.role == 'admin'

def perform_action(user, action_type):
    if action_type == 'edit':
        if user.can_edit():
            print(f"{user.username} is editing the document.")
        else:
            print(f"{user.username} is not authorized to edit.")
    elif action_type == 'delete':
        if user.can_delete():  # Fixed: Only check for delete privilege
            # The delete operation now correctly requires only the delete privilege
            print(f"{user.username} is deleting the document.")
        else:
            print(f"{user.username} is not authorized to delete.")

# Example usage
user = User("Alice", "editor")
perform_action(user, "delete")  # Properly restricts delete operation

Explanation of the Fix

In the fixed code, the perform_action function now correctly checks only the can_delete() method for the delete action. This ensures that only users with admin rights can delete documents, thereby eliminating the privilege chaining vulnerability. The code follows best practices by ensuring that each action is guarded by the appropriate privilege check, preventing unauthorized actions.