CWE-289: Authentication Bypass by Alternate Name

What is Authentication Bypass by Alternate Name?

• Overview: This vulnerability occurs when authentication is based on a name, but not all possible names for a resource or user are checked. Attackers can exploit this oversight by using alternative names to bypass authentication mechanisms.

• Exploitation Methods:

• Attackers can exploit this vulnerability by identifying alternative names for a user or resource that are not properly authenticated.
• Common attack patterns include using different formats or representations of names (e.g., case variations, aliases, or encoded representations) to gain unauthorized access.

• Security Impact:

• Direct consequences include unauthorized access to sensitive resources or data.
• Potential cascading effects involve further exploitation of the system, such as privilege escalation or data breaches.
• Business impact can be significant, including data loss, reputational damage, and compliance violations.

• Prevention Guidelines:

• Specific code-level fixes include ensuring comprehensive validation and normalization of all possible names for resources and users.
• Security best practices involve implementing strong authentication mechanisms that do not rely solely on user or resource names.
• Recommended tools and frameworks can include those that provide robust access control and identity management, such as OAuth, OpenID Connect, or other identity federation frameworks.

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Technical Details

Likelihood of Exploit: Not specified

Affected Languages: Not Language-Specific

Affected Technologies: Not specified

Vulnerable Code Example

# Vulnerable authentication logic using alternate names for admin access

def authenticate_user(username, password):
    # A dictionary of usernames and passwords
    users_db = {
        "admin": "securePassword123",
        "administrator": "securePassword123",
        "root": "securePassword123"
    }

    # Check if username exists and password matches
    if username in users_db and users_db[username] == password:
        # Grant admin access if any of the admin-like usernames match
        return "Admin Access Granted"
    return "Access Denied"

Explanation:

• Multiple Admin Aliases: The code allows multiple usernames with admin privileges ("admin", "administrator", "root"), increasing the risk of an authentication bypass if any additional aliases are added without proper oversight.
• Potential for Oversight: New aliases could be added inadvertently, creating security holes if not carefully managed.

How to fix Authentication Bypass by Alternate Name?

To fix this vulnerability, we should:

1. Use a Unique Identifier: Always authenticate users using a unique identifier like a user ID instead of relying on multiple names or aliases.
2. Centralize Authentication Logic: Ensure authentication logic is centralized and not scattered across multiple parts of the application.
3. Remove Redundant Usernames: Avoid having multiple usernames for the same account or privilege level to reduce the risk of bypass through unaccounted aliases.
4. Regularly Audit User Database: Regularly audit the user database to ensure no unauthorized alternate names exist.

Fixed Code Example

# Fixed authentication logic with a focus on unique user identification

def authenticate_user(user_id, password):
    # A dictionary of user IDs and user details
    users_db = {
        1: {"username": "admin", "password": "securePassword123"},
        2: {"username": "user", "password": "userPassword456"}
    }

    # Check if user_id exists and password matches
    if user_id in users_db and users_db[user_id]["password"] == password:
        # Ensure that admin access is strictly through user_id checks
        if user_id == 1:  # Unique ID for admin
            return "Admin Access Granted"
    return "Access Denied"

Explanation:

• Unique Identifier: We use a user_id to uniquely identify users, which eliminates the risk of using alternate names for authentication.
• Centralized Logic: The logic is centralized using IDs rather than names, making it easier to manage and audit.
• Reduced Redundancy: By using a single point of truth for username and access level, we avoid issues with multiple usernames for the same user.