CWE-924: Improper Enforcement of Message Integrity During Transmission in a Communication Channel

What is Improper Enforcement of Message Integrity During Transmission in a Communication Channel?

• Overview: This vulnerability occurs when a communication channel lacks adequate checks to ensure that messages are not altered during transmission. Without proper integrity enforcement, attackers can modify data sent between systems without detection.

• Exploitation Methods:

• Attackers can intercept and alter messages as they traverse the network, effectively performing a man-in-the-middle attack.
• Common techniques include packet sniffing and message injection, allowing attackers to spoof endpoints or redirect connections to malicious servers.

• Security Impact:

• Direct consequences include unauthorized data manipulation, leading to incorrect application behavior or data corruption.
• Potential cascading effects involve unauthorized access or escalation of privileges if attack vectors are leveraged effectively.
• Business impact could include data breaches, loss of customer trust, legal repercussions, and financial losses due to compromised systems.

• Prevention Guidelines:

• Implement cryptographic techniques such as HMAC or digital signatures to verify message integrity.
• Use secure communication protocols like TLS/SSL to encrypt data in transit.
• Employ end-to-end encryption to ensure data remains unaltered from the source to the destination.
• Regularly update and patch systems to mitigate known vulnerabilities.
• Utilize tools and frameworks that provide built-in support for secure communications, such as OpenSSL or libraries within your development environment that support integrity checks.

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Technical Details

Likelihood of Exploit: Not specified

Affected Languages: Not Language-Specific

Affected Technologies: Not specified

Vulnerable Code Example

import socket

def receive_message():
    # Create a socket connection
    sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    sock.connect(('example.com', 12345))

    # Receive a message from the server
    message = sock.recv(1024)  # Vulnerable: No integrity check
    sock.close()

    print("Received:", message.decode('utf-8'))

receive_message()

Explanation

In the above code, a message is received over a socket connection without any mechanism to verify its integrity. This creates a vulnerability to man-in-the-middle (MITM) attacks, where an attacker could intercept and modify the message without detection. The absence of an integrity check means the application cannot ensure that the received message is authentic or unaltered.

How to fix Improper Enforcement of Message Integrity During Transmission in a Communication Channel?

To address this vulnerability, we must implement a mechanism to verify message integrity. A common approach is to use an HMAC (Hash-based Message Authentication Code), which combines a cryptographic hash function with a secret key. This allows the receiving end to verify the message's integrity and authenticity.

Fixed Code Example

import socket
import hmac
import hashlib

SECRET_KEY = b'supersecretkey'  # Shared secret key for HMAC

def receive_message():
    # Create a socket connection
    sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    sock.connect(('example.com', 12345))

    # Receive a message and its HMAC from the server
    message = sock.recv(1024)
    received_hmac = sock.recv(64)  # Assume we receive the HMAC separately
    sock.close()

    # Verify the HMAC to ensure integrity
    expected_hmac = hmac.new(SECRET_KEY, message, hashlib.sha256).digest()
    if hmac.compare_digest(received_hmac, expected_hmac):  # Secure HMAC comparison
        print("Received:", message.decode('utf-8'))
    else:
        print("Integrity check failed: Message has been tampered!")

receive_message()

Explanation

• HMAC Implementation: We added a secret key (SECRET_KEY) and used the hmac module to generate an HMAC for the message. The hmac.new() function creates an HMAC using the SHA-256 hash function.
• Integrity Check: The hmac.compare_digest() function securely compares the received HMAC with the expected HMAC. This method is resistant to timing attacks that can exploit simple equality checks.
• Security Assurance: By verifying the HMAC, the application ensures that the message has not been altered in transit, providing both integrity and authenticity guarantees.

This solution significantly enhances the security of the communication channel by mitigating the risk of message tampering during transmission.