CWE-291: Reliance on IP Address for Authentication

What is Reliance on IP Address for Authentication?

• Overview: Reliance on IP Address for Authentication (CWE-291) occurs when a system uses an IP address as the sole method for verifying a user's identity. This approach is flawed because IP addresses can be easily spoofed, allowing attackers to impersonate legitimate users.

• Exploitation Methods:

• Attackers can exploit this vulnerability by forging the source IP address in their network packets to appear as a trusted entity.
• Common attack patterns include IP spoofing to gain unauthorized access and network sniffing to capture sensitive information.

• Security Impact:

• Direct consequences of successful exploitation include unauthorized access to restricted systems and data.
• Potential cascading effects may involve data breaches, data manipulation, and compromised network integrity.
• Business impact can include financial loss, reputational damage, and legal ramifications due to data protection violations.

• Prevention Guidelines:

• Specific code-level fixes involve implementing multi-factor authentication (MFA) that does not rely solely on IP addresses.
• Security best practices include using secure protocols like TLS, deploying firewalls with strict rules, and monitoring for unusual network activity.
• Recommended tools and frameworks include intrusion detection systems (IDS), network monitoring tools, and authentication frameworks that support MFA.

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Technical Details

Likelihood of Exploit: High

Affected Languages: Not Language-Specific

Affected Technologies: Not specified

Vulnerable Code Example

from flask import Flask, request, jsonify

app = Flask(__name__)

# Vulnerable: Using IP address for authentication
AUTHORIZED_IP = "192.168.1.100"

@app.route('/sensitive-data')
def get_sensitive_data():
    # Check if the request IP matches the authorized IP
    if request.remote_addr == AUTHORIZED_IP:  # Vulnerable to IP spoofing
        return jsonify({"data": "This is sensitive data"})
    else:
        return jsonify({"error": "Unauthorized access"}), 403

if __name__ == '__main__':
    app.run()

Explanation:

• The above code relies on the client's IP address for authentication, which is insecure because IP addresses can be spoofed. An attacker could manipulate their IP address to match the authorized IP, thereby gaining unauthorized access to sensitive data.

How to fix Reliance on IP Address for Authentication?

To properly secure the application, avoid using IP addresses for authentication. Instead, implement a more robust authentication mechanism such as token-based authentication (e.g., JWT), OAuth, or using an API key. These methods ensure that even if an IP address is spoofed, the attacker cannot access the system without valid authentication credentials.

Fixed Code Example

from flask import Flask, request, jsonify
import jwt

app = Flask(__name__)

# Secure: Using JWT for authentication
SECRET_KEY = "your_secret_key"

def verify_jwt(token):
    try:
        # Decode the JWT with the secret key
        decoded = jwt.decode(token, SECRET_KEY, algorithms=["HS256"])
        return decoded
    except jwt.InvalidTokenError:
        return None

@app.route('/sensitive-data')
def get_sensitive_data():
    # Extract the token from the Authorization header
    auth_header = request.headers.get('Authorization')
    if auth_header:
        parts = auth_header.split(" ")
        if len(parts) == 2 and parts[0] == "Bearer":
            token = parts[1]
            user_data = verify_jwt(token)
            if user_data:
                return jsonify({"data": "This is sensitive data"})
    
    return jsonify({"error": "Unauthorized access"}), 403

if __name__ == '__main__':
    app.run()

Explanation:

• In the fixed version, the application uses JWT (JSON Web Tokens) for authentication. A valid token is required to access sensitive data.
• The JWT is decoded using a secret key, ensuring that only clients with a valid token can access the resource.
• This approach significantly enhances security by requiring cryptographic proof of authentication rather than relying on IP addresses, which can be easily spoofed.
• The code checks for the "Bearer" scheme in the Authorization header to ensure the token is well-formed before attempting to verify it.