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Insecure encryption algorithm - Anonymous cipher suites

Need​

Use of secure and authenticated encryption algorithms

Context​

  • Usage of Scala for building scalable and high-performance applications
  • Usage of javax.net.ssl for secure communication over HTTPS
  • Usage of java.security.SecureRandom for generating secure random numbers
  • Usage of X509Certificate for working with X.509 certificates in Java security

Description​

Non compliant code​

import javax.net.ssl._
import java.security.SecureRandom
import java.security.cert.X509Certificate

val sslContext = SSLContext.getInstance("SSL")
sslContext.init(null, Array(new X509TrustManager {
  override def getAcceptedIssuers: Array[X509Certificate] = null

  override def checkClientTrusted(certs: Array[X509Certificate], authType: String): Unit = {}

  override def checkServerTrusted(certs: Array[X509Certificate], authType: String): Unit = {}
}), new SecureRandom())

val ssf = sslContext.getSocketFactory
val socket = ssf.createSocket("localhost", 443)
val sslSocket = socket.asInstanceOf[SSLSocket]

sslSocket.setEnabledCipherSuites(sslSocket.getSupportedCipherSuites)

In the above code, the application is using SSLContext with 'SSL' as the protocol. This is considered insecure because it allows the use of deprecated and insecure cipher suites, including anonymous cipher suites.

The SSLContext is initialized with a TrustManager that does not perform any checks, which means any certificate (even an invalid one) will be trusted. This makes the application vulnerable to man-in-the-middle attacks.

The most critical part is the line sslSocket.setEnabledCipherSuites(sslSocket.getSupportedCipherSuites). This line enables all supported cipher suites including the anonymous ones. Anonymous cipher suites do not authenticate the server, which leaves the application vulnerable to man-in-the-middle attacks.

In a production environment, it's recommended to use only strong cipher suites and to validate certificates properly.

Steps​

  • Remove the usage of anonymous cipher suites.
  • Use a secure encryption algorithm instead of the default 'SSL' algorithm.
  • Implement proper certificate validation for both client and server certificates.
  • Enable only the necessary and secure cipher suites supported by the SSL socket.

Compliant code​

import javax.net.ssl._
import java.security.SecureRandom
import java.security.cert.X509Certificate

// Create a TrustManager that checks all certificates
val trustAllCerts = Array[TrustManager](new X509TrustManager {
  def getAcceptedIssuers: Array[X509Certificate] = Array()

  def checkClientTrusted(certs: Array[X509Certificate], authType: String): Unit = {
    throw new CertificateException("Client certificate not trusted")
  }

  def checkServerTrusted(certs: Array[X509Certificate], authType: String): Unit = {
    throw new CertificateException("Server certificate not trusted")
  }
})

// Initialize the SSLContext with the TrustManager array and a new SecureRandom
val sslContext = SSLContext.getInstance("TLS")
sslContext.init(null, trustAllCerts, new SecureRandom())

val ssf = sslContext.getSocketFactory
val socket = ssf.createSocket("localhost", 443)
val sslSocket = socket.asInstanceOf[SSLSocket]

// Enable only the necessary and secure cipher suites
val enabledCipherSuites = Array(
  "TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384",
  "TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384",
  "TLS_DHE_RSA_WITH_AES_256_GCM_SHA384"
)
sslSocket.setEnabledCipherSuites(enabledCipherSuites)

The original code was vulnerable because it allowed connections with anonymous cipher suites and did not implement proper certificate validation. This could allow an attacker to perform a man-in-the-middle attack.

The fixed code addresses these issues by:

  1. Using the 'TLS' encryption algorithm instead of the insecure 'SSL' algorithm. 'TLS' is currently the most secure protocol for securing communications between web applications and servers.

  2. Implementing a TrustManager that throws a CertificateException for both client and server certificates. This ensures that only trusted certificates are used for secure communication.

  3. Enabling only the necessary and secure cipher suites. The cipher suites chosen are currently some of the most secure options available. They use strong encryption (AES 256) and secure key exchange mechanisms (ECDHE and DHE).

References​

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