Insecure encryption algorithm - Anonymous cipher suites - Ruby

Need

Secure encryption algorithm for secure connections

Context

Usage of Ruby for building dynamic and object-oriented applications
Usage of OpenSSL for secure communication and encryption
Usage of Socket for real-time communication and event-based messaging

Description

Non compliant code

        require 'openssl'
require 'socket'

tcp_server = TCPServer.new(5000)
ssl_context = OpenSSL::SSL::SSLContext.new
ssl_context.ciphers = 'aNULL'

ssl_server = OpenSSL::SSL::SSLServer.new(tcp_server, ssl_context)

loop do
  ssl_connection = ssl_server.accept
  data = ssl_connection.gets
  ssl_connection.puts "Received: #{data}"
  ssl_connection.close
end

The provided Ruby code snippet represents a simple server that accepts SSL connections. The server is set up to listen on port 5000 and uses the OpenSSL library to handle the SSL context.

The vulnerability lies in the following line:

                ssl_context.ciphers = 'aNULL'

Here, the server is configured to use anonymous cipher suites, as indicated by the 'aNULL' string. This means that the server accepts connections that do not authenticate the server's identity to the client. As a result, the client has no way of verifying the server's identity, which makes the connection vulnerable to man-in-the-middle attacks.

In a man-in-the-middle attack, an attacker intercepts the communication between the client and the server, potentially gaining access to sensitive information or injecting malicious data into the connection.

To fix this vulnerability, the server should be configured to use secure cipher suites that require server authentication.

Steps

Update the OpenSSL library to the latest version.
Use a secure encryption algorithm instead of the anonymous cipher suites.
Disable support for anonymous cipher suites in the SSL/TLS configuration.
Implement proper certificate validation to ensure secure connections.
Regularly monitor and update the SSL/TLS configuration to address any new vulnerabilities.

Compliant code

        require 'openssl'
require 'socket'

tcp_server = TCPServer.new(5000)
ssl_context = OpenSSL::SSL::SSLContext.new
ssl_context.ciphers = 'AES256-SHA'

ssl_server = OpenSSL::SSL::SSLServer.new(tcp_server, ssl_context)

loop do
  ssl_connection = ssl_server.accept
  data = ssl_connection.gets
  ssl_connection.puts "Received: #{data}"
  ssl_connection.close
end

The original code was using an insecure encryption algorithm, specifically an anonymous cipher suite. This is a vulnerability because it allows connections with anonymous cipher suites, which do not provide authentication. This means that an attacker could potentially intercept the communication.

The updated code fixes this vulnerability by using a secure encryption algorithm, specifically 'AES256-SHA'. This is a strong, non-anonymous cipher suite that provides both authentication and encryption, ensuring that the communication is secure.

In addition to changing the cipher suite, it's also important to keep the OpenSSL library updated to the latest version, disable support for anonymous cipher suites in the SSL/TLS configuration, implement proper certificate validation, and regularly monitor and update the SSL/TLS configuration to address any new vulnerabilities.

References

092. Insecure encryption algorithm - Anonymous cipher suites