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Insecure encryption algorithm - AES

Need​

Implementation of secure encryption algorithms

Context​

  • Usage of Scala for building scalable and high-performance applications
  • Usage of javax.crypto for cryptographic operations

Description​

Non compliant code​

import javax.crypto.Cipher
import javax.crypto.spec.SecretKeySpec
import javax.crypto.spec.IvParameterSpec

// AES encryption
val key = "0123456789abcdef" // 128 bit key
val initVector = "RandomInitVector" // 16 bytes IV

val skeySpec = new SecretKeySpec(key.getBytes("UTF-8"), "AES")
val iv = new IvParameterSpec(initVector.getBytes("UTF-8"))

val cipher = Cipher.getInstance("AES/CBC/PKCS5PADDING")
cipher.init(Cipher.ENCRYPT_MODE, skeySpec, iv)

val encrypted = cipher.doFinal("This is a test.".getBytes())

// RSA encryption
val cipherRSA = Cipher.getInstance("RSA/ECB/PKCS1Padding")
val keyRSA = new SecretKeySpec(key.getBytes("UTF-8"), "RSA")
cipherRSA.init(Cipher.ENCRYPT_MODE, keyRSA)

val encryptedRSA = cipherRSA.doFinal("This is a test.".getBytes())

In this Scala code, we are using the AES/CBC/PKCS5PADDING and RSA/ECB/PKCS1Padding encryption methods, which are considered insecure.

The AES encryption method uses a Cipher Block Chaining (CBC) mode. This mode is vulnerable to padding oracle attacks, where an attacker can decrypt data without knowing the encryption key, by observing the server's response to manipulated ciphertexts.

The RSA encryption method uses Electronic Codebook (ECB) mode. This mode encrypts each block of plaintext separately, which makes it vulnerable to various forms of analysis and attacks. Particularly, the same plaintext block will always produce the same ciphertext block, which may reveal patterns to an attacker.

The PKCS1Padding and PKCS5PADDING padding methods used are also insecure. They have vulnerabilities that can be exploited through techniques such as padding oracle attacks, where an attacker can decrypt data without knowing the encryption key.

The use of a hard-coded key ("0123456789abcdef") and initialization vector ("RandomInitVector") is also a bad practice as it reduces the security of the encryption.

In addition, other parts of the code reference the CTR and CFB modes, which are also considered insecure.

To fix these vulnerabilities, the code should use secure encryption methods and modes, such as AES/GCM/NoPadding for AES and RSA/OAEPWithSHA-1AndMGF1Padding for RSA. Also, keys and initialization vectors should be generated securely and not hard-coded.

Steps​

  • Replace the insecure AES encryption algorithm with a secure one, such as AES/GCM or AES/CTR.
  • Ensure that a secure key management system is used to generate and store the encryption keys.
  • Use a secure random initialization vector (IV) for AES encryption.
  • Replace the insecure RSA encryption algorithm with a secure one, such as RSA/OAEP.
  • Ensure that a secure key management system is used to generate and store the RSA encryption keys.
  • Implement proper key size and key strength for both AES and RSA encryption algorithms.
  • Follow best practices for encryption and decryption operations, such as securely handling sensitive data, protecting against side-channel attacks, and securely storing encrypted data.

Compliant code​

import javax.crypto.Cipher
import javax.crypto.spec.SecretKeySpec
import javax.crypto.spec.IvParameterSpec
import java.security.SecureRandom
import javax.crypto.spec.GCMParameterSpec

// AES encryption
val key = Array.fill[Byte](16)(0) // 128 bit key
(new SecureRandom()).nextBytes(key) // generate a random key

val initVector = new Array[Byte](12) // 12 bytes IV, GCM recommended
(new SecureRandom()).nextBytes(initVector) // generate a random IV

val skeySpec = new SecretKeySpec(key, "AES")
val iv = new GCMParameterSpec(128, initVector)

val cipher = Cipher.getInstance("AES/GCM/NoPadding")
cipher.init(Cipher.ENCRYPT_MODE, skeySpec, iv)

val encrypted = cipher.doFinal("This is a test.".getBytes())

// RSA encryption
val cipherRSA = Cipher.getInstance("RSA/ECB/OAEPWithSHA-256AndMGF1Padding")
val keyRSA = new SecretKeySpec(key, "RSA")
cipherRSA.init(Cipher.ENCRYPT_MODE, keyRSA)

val encryptedRSA = cipherRSA.doFinal("This is a test.".getBytes())

The updated code now uses secure encryption algorithms for both AES and RSA.

For AES, we have replaced the insecure "AES/CBC/PKCS5PADDING" with "AES/GCM/NoPadding". GCM (Galois/Counter Mode) is a mode of operation that provides both data authenticity (integrity) and confidentiality. It's considered secure and efficient.

For RSA, we have replaced the insecure "RSA/ECB/PKCS1Padding" with "RSA/ECB/OAEPWithSHA-256AndMGF1Padding". OAEP (Optimal Asymmetric Encryption Padding) is a padding scheme often used together with RSA encryption. It provides a level of security against attacks that the older PKCS1Padding does not.

We also generate a random key and initialization vector (IV) for AES encryption using SecureRandom. This is a best practice as it makes the encryption more secure by ensuring that the key and IV are not predictable.

For both AES and RSA, we use a SecretKeySpec to generate a key from a byte array. This is a simple and secure way to generate keys.

Finally, we use the doFinal method of the Cipher class to perform the encryption. This method is secure and efficient, and it ensures that all data is processed in a single operation.

References​

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