CWE-923: Improper Restriction of Communication Channel to Intended Endpoints

What is Improper Restriction of Communication Channel to Intended Endpoints?

• Overview: Improper Restriction of Communication Channel to Intended Endpoints (CWE-923) occurs when software establishes communication channels for sensitive operations but fails to verify that it is interacting with the correct endpoint, allowing unauthorized access.

• Exploitation Methods:

• Attackers can impersonate the intended endpoint, often through spoofing techniques, to gain unauthorized access.
• Common attack patterns include man-in-the-middle attacks and DNS spoofing to redirect communications to a malicious endpoint.

• Security Impact:

• Direct consequences include unauthorized access to sensitive data and operations.
• Potential cascading effects involve further compromise of systems and data leakage.
• Business impact can be significant, leading to loss of customer trust, regulatory penalties, and financial loss.

• Prevention Guidelines:

• Specific code-level fixes include implementing mutual authentication mechanisms to verify endpoints.
• Security best practices involve using strong encryption protocols (e.g., TLS) and validating endpoint credentials.
• Recommended tools and frameworks include using libraries that support secure communication channels and endpoint verification, such as OpenSSL for encryption and authentication.

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Technical Details

Likelihood of Exploit: Not specified

Affected Languages: Not Language-Specific

Affected Technologies: Not specified

Vulnerable Code Example

```python communication.py {10-12}
import socket

def send_sensitive_data(data):
    # Vulnerable: No verification of the endpoint
    # This code blindly sends data to the specified IP address and port
    with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as s:
        s.connect(('192.168.1.100', 8080))  # Hardcoded endpoint without verification
        s.sendall(data.encode())  # Sending data to potentially malicious endpoint
        print("Data sent to endpoint.")

Explanation of the Vulnerability

In this example, the function send_sensitive_data sends data to a hardcoded IP address and port without verifying the endpoint. This approach is insecure because:

• No Endpoint Verification: The connection is established without authenticating the server, potentially allowing data to be sent to an unintended or malicious endpoint.
• Hardcoded Endpoint: The IP address and port are hardcoded, making it difficult to change the endpoint without modifying the code. This increases the risk of misconfiguration and accidental exposure of sensitive data.

How to fix Improper Restriction of Communication Channel to Intended Endpoints?

To secure communication channels effectively, ensure that you are communicating with the correct and intended endpoint. This involves:

1. Endpoint Verification: Use mechanisms like TLS/SSL to verify that the endpoint you are connecting to is indeed the intended recipient. This helps prevent Man-in-the-Middle (MitM) attacks by ensuring the server's identity.

2. Use Secure Protocols: Always prefer using secure protocols such as HTTPS over plain HTTP, or TLS over raw TCP for communication.

3. Certificate Validation: Implement certificate validation to ensure the server's certificate is signed by a trusted Certificate Authority (CA).

4. Dynamic Configuration: Avoid hardcoding endpoint addresses. Use configuration files or environment variables to dynamically set endpoint addresses, allowing for easier updates and management.

Fixed Code Example

import socket
import ssl
import os

def send_sensitive_data_securely(data):
    # Secure: Establish an SSL/TLS connection to verify the endpoint
    context = ssl.create_default_context()  # Use a default SSL context

    # Use environment variables or configuration files to set endpoint dynamically
    endpoint = os.getenv('SECURE_ENDPOINT', 'secure.example.com')
    port = int(os.getenv('SECURE_PORT', '443'))

    with socket.create_connection((endpoint, port)) as sock:  # Use a secure endpoint
        with context.wrap_socket(sock, server_hostname=endpoint) as ssock:  # Wrap the socket to use SSL
            # The server's certificate will be verified against default CA certificates
            ssock.sendall(data.encode())  # Securely sending data
            print("Data securely sent to endpoint.")

Explanation of the Fix

In the fixed example, the function send_sensitive_data_securely uses SSL/TLS to secure the communication:

• SSL/TLS Encryption: The ssl module is used to create a secure connection, ensuring that the data is encrypted during transmission.
• Server Certificate Verification: The server's certificate is verified against the default trusted CA certificates, preventing connections to untrusted endpoints.
• Dynamic Configuration: The endpoint and port are retrieved from environment variables, allowing for flexible configuration management and reducing the risk of hardcoded values.
• Secure Endpoint: By connecting to a secure endpoint over port 443, the communication is encrypted and authenticated, mitigating risks of data interception or manipulation.