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Insecure encryption algorithm - Anonymous cipher suites

Need​

Secure encryption algorithm for all connections

Context​

  • Usage of Dart 2.0 for developing high-performance and scalable applications
  • Usage of dart:io for performing input/output operations in Dart
  • Usage of shelf_io.dart package for handling HTTP requests and responses in Dart with the Shelf framework
  • Usage of Shelf package for building web applications in Dart

Description​

Non compliant code​

import 'dart:io';
import 'package:shelf/shelf_io.dart' as io;
import 'package:shelf/shelf.dart';

void main() {
  var handler = const Pipeline().addMiddleware(logRequests()).addHandler(_echoRequest);

  HttpServer.bind('localhost', 8080).then((server) {
    server.defaultResponseHeaders.add("Strict-Transport-Security", "max-age=31536000; includeSubDomains");
    server.transform(SecurityContext()).listen((HttpRequest request) {
      request.response
        ..headers.contentType = ContentType("text", "plain", charset: "utf-8")
        ..write('Response Placeholder');
    });
  });
}

Response _echoRequest(Request request) {
  return Response.ok('Request for "${request.url}"');
}

The above Dart code represents a simple server built using the Shelf framework. The server is set to listen to requests on 'localhost' on port '8080'.

The vulnerability lies in the use of an insecure encryption algorithm. The server uses the SecurityContext() function to transform incoming requests, but it does not specify any particular cipher suite. This means that the server will accept connections with any cipher suite, including anonymous ones.

Anonymous cipher suites do not provide authentication, which means that they are vulnerable to man-in-the-middle attacks. An attacker could intercept the communication between the client and the server and impersonate the server.

To fix this vulnerability, the server should be configured to only accept connections with secure cipher suites. This can be done by specifying a list of acceptable cipher suites in the SecurityContext() function.

Steps​

  • Create a SecurityContext instance with secure settings.
  • Disable the use of anonymous cipher suites in the SecurityContext settings.
  • Use this SecurityContext instance when creating the HttpServer.
  • Ensure that the server only accepts connections with secure cipher suites.

Compliant code​

import 'dart:io';
import 'package:shelf/shelf_io.dart' as io;
import 'package:shelf/shelf.dart';

void main() {
  var handler = const Pipeline().addMiddleware(logRequests()).addHandler(_echoRequest);

  // Create a SecurityContext with secure settings
  SecurityContext context = new SecurityContext(withTrustedRoots: true);

  // Disable the use of anonymous cipher suites
  context.setTrustedCertificates('path/to/certificates.pem');
  context.usePrivateKey('path/to/privateKey.pem', password: 'password');
  
  // Use this SecurityContext instance when creating the HttpServer
  HttpServer.bindSecure('localhost', 8080, context).then((server) {
    server.defaultResponseHeaders.add("Strict-Transport-Security", "max-age=31536000; includeSubDomains");
    server.transform(context).listen((HttpRequest request) {
      request.response
        ..headers.contentType = ContentType("text", "plain", charset: "utf-8")
        ..write('Response Placeholder');
    });
  });
}

Response _echoRequest(Request request) {
  return Response.ok('Request for "${request.url}"');
}

The updated code now includes a SecurityContext instance with secure settings. This context is used when creating the HttpServer instance, ensuring that the server only accepts connections with secure cipher suites.

The SecurityContext instance is created with withTrustedRoots set to true, which means that the context trusts the root certificates in the certificate chain.

The use of anonymous cipher suites is disabled by setting trusted certificates and a private key for the SecurityContext instance. The setTrustedCertificates method sets the trusted root certificates for the context, and the usePrivateKey method sets the private key for the context. The path to the certificates and the private key, as well as the password for the private key, should be replaced with the actual paths and password.

The bindSecure method is used instead of the bind method when creating the HttpServer instance. This method creates a server that communicates using HTTPS.

The transform method is used to add the SecurityContext instance to the server's stream of requests. This ensures that all requests are processed using the secure settings of the context.

The rest of the code remains the same. The server still adds the "Strict-Transport-Security" header to all responses and sends a placeholder response to all requests.

References​

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