Insecure encryption algorithm - Anonymous cipher suites - Python

Insecure encryption algorithm - Anonymous cipher suites - Python

Need

Secure encryption algorithm and cipher suite selection

Context

  • Usage of Python 3 for scripting and software development
  • Usage of Django for building web applications
  • Usage of OpenSSL for secure communication and encryption

Description

Non compliant code

        from django.core.servers.basehttp import get_internal_wsgi_application
from OpenSSL import SSL
import os

os.environ['DJANGO_SETTINGS_MODULE'] = 'myapp.settings'
application = get_internal_wsgi_application()

context = SSL.Context(SSL.TLSv1_METHOD)
context.set_cipher_list('aNULL')

This code snippet is a part of a Django backend application. The application is using the Django's built-in server and the PyOpenSSL library to handle SSL/TLS connections.

The key part of this code is the context.set_cipher_list('aNULL') line. This line sets the cipher suites that the server will use to establish SSL/TLS connections. The 'aNULL' value means that the server will use anonymous cipher suites.

Anonymous cipher suites are a security risk because they don't provide authentication. This means that an attacker could impersonate the server or the client, leading to man-in-the-middle attacks. This is why it's recommended to always use cipher suites that provide authentication.

In this case, the vulnerability lies in the fact that the server is explicitly set to use anonymous cipher suites, making it susceptible to the aforementioned attacks.

Steps

  • Replace the insecure encryption algorithm with a secure one. The 'aNULL' cipher suite is considered insecure because it allows anonymous connections, which can be exploited by attackers.
  • Remove the 'aNULL' from the cipher list. This will prevent the application from using anonymous cipher suites.
  • Use a secure cipher suite such as 'AES256-GCM-SHA384'. This cipher suite is considered secure and provides strong encryption.
  • Ensure that the application does not allow fallback to less secure cipher suites. This can be done by configuring the application to only use secure cipher suites.
  • Regularly update the cipher suites as new vulnerabilities may be discovered in the future. This will ensure that the application remains secure.

Compliant code

        from django.core.servers.basehttp import get_internal_wsgi_application
from OpenSSL import SSL
import os

os.environ['DJANGO_SETTINGS_MODULE'] = 'myapp.settings'
application = get_internal_wsgi_application()

context = SSL.Context(SSL.TLSv1_METHOD)
context.set_cipher_list('AES256-GCM-SHA384')

The original code was vulnerable due to the use of an insecure encryption algorithm, specifically the 'aNULL' cipher suite. This cipher suite is considered insecure because it allows anonymous connections, which can be exploited by attackers to compromise the security of the application.

The updated code replaces the 'aNULL' cipher suite with 'AES256-GCM-SHA384', a secure cipher suite that provides strong encryption. This change prevents the application from using anonymous cipher suites, thereby mitigating the vulnerability.

In the updated code:

- The 'DJANGO_SETTINGS_MODULE' environment variable is set to 'myapp.settings'. This is necessary for Django to know which settings to use.
- The application is configured to use the 'get_internal_wsgi_application' function from Django's 'basehttp' module. This function returns a WSGI application that Django's server can use to handle requests.
- An SSL context is created using the 'TLSv1_METHOD'. This method is used to specify the version of the SSL/TLS protocol to use for the connection.
- The 'set_cipher_list' method is used to specify the cipher suites that the SSL context should use. In the updated code, this is set to 'AES256-GCM-SHA384', a secure cipher suite.

By using a secure cipher suite and preventing the use of anonymous cipher suites, the updated code ensures that the application's connections are secure. It is also recommended to regularly update the cipher suites as new vulnerabilities may be discovered in the future.

References