Need

Prevention of automatic information enumeration and unauthorized access to system information.

Context

• Usage of Ruby for developing web applications and scripting
• Usage of Socket for real-time communication and event-based messaging

Description

Non compliant code

        require 'socket'

server = TCPServer.new 5678

while session = server.accept
  request = session.gets
  puts request

  session.print "HTTP/1.1 200\\r\\n" 
  session.print "Content-Type: text/html\\r\\n"
  session.print "\\r\\n"
  session.print "Port 5678 is open.\\r\\n"

  session.close
end
        
        

The above code is a simple Ruby server that listens on port 5678. When a client sends a request to this server, it simply responds with a message stating that port 5678 is open.

This code is vulnerable to information enumeration because it publicly exposes the fact that port 5678 is open. An attacker can easily use this information to their advantage. For instance, they can attempt to exploit any vulnerabilities that may exist in the services running on this port.

Moreover, the server indiscriminately accepts all incoming connections and handles them the same way. It does not perform any authentication or authorization checks. This could potentially allow unauthorized users to gain access to sensitive information.

Furthermore, this server does not sanitize or validate the client's request in any way. A malicious client could potentially send a specially crafted request to enumerate more information from the server or to perform other malicious actions.

Steps

• Avoid printing sensitive information such as system details or personal data.
• Implement proper input validation and sanitization to prevent unauthorized access or data leakage.
• Use authentication and authorization mechanisms to control access to sensitive information.
• Implement rate limiting to prevent automated enumeration attacks.
• Regularly update and patch the server and application to address any known vulnerabilities.
• Implement logging and monitoring to detect and respond to any suspicious activities or enumeration attempts.

Compliant code

        require 'socket'
require 'rack'
require 'rack/lobster'

app = Rack::Lobster.new
server = Rack::Handler::WEBrick

server.run app, :Port => 5678
        
        

The original code was vulnerable as it was revealing sensitive system information (open port) to the client. This could potentially be exploited by an attacker to enumerate system information and launch further attacks.

The revised code uses the Rack middleware library, which provides a modular and adaptable interface for developing web applications in Ruby. By using Rack, we can take advantage of its built-in security features and avoid exposing sensitive system information.

In the revised code, we create a new instance of Rack::Lobster, which is a simple Rack application. We then use Rack::Handler::WEBrick to start a WEBrick server and run our Rack application on port 5678.

This way, we are not directly handling the TCP connection or manually printing HTTP responses, which can be error-prone and potentially insecure. Instead, we delegate these tasks to Rack and WEBrick, which are designed to handle them securely and efficiently.

Furthermore, by not revealing any system information in our responses, we reduce the risk of information enumeration attacks. The client only receives the response generated by the Rack::Lobster application, which does not include any sensitive system information.

Remember to always follow best practices for secure coding, such as input validation, authentication and authorization, rate limiting, regular updates and patches, and logging and monitoring.

References

• 047. Automatic information enumeration