Insecure encryption algorithm - AES - Go

Insecure encryption algorithm - AES - Go

Need

Implementation of secure encryption algorithms

Context

  • Usage of Go 1.16 for building high-performance and efficient applications
  • Usage of crypto/aes for AES encryption and decryption
  • Usage of crypto/cipher for cryptographic encryption and decryption
  • Usage of crypto/rand for generating secure random numbers or bytes
  • Usage of fmt for formatting text or data
  • Usage of socket.io for real-time communication and event-based programming

Description

Non compliant code

        package main

import (
	"crypto/aes"
	"crypto/cipher"
	"crypto/rand"
	"fmt"
	"io"
)

func main() {
	text := []byte("This is a test.")
	key := []byte("This is an insecure key.")

	ciphertext, err := encrypt(text, key)
	if err != nil {
		fmt.Println("Error: ", err)
		return
	}

	fmt.Printf("%s => %x\\n", text, ciphertext)
}

func encrypt(text, key []byte) ([]byte, error) {
	block, err := aes.NewCipher(key)
	if err != nil {
		return nil, err
	}

	ciphertext := make([]byte, aes.BlockSize+len(text))
	iv := ciphertext[:aes.BlockSize]
	if _, err := io.ReadFull(rand.Reader, iv); err != nil {
		return nil, err
	}

	mode := cipher.NewCBCEncrypter(block, iv)
	mode.CryptBlocks(ciphertext[aes.BlockSize:], text)

	return ciphertext, nil
}

In this code, we are using the AES encryption algorithm with Cipher Block Chaining (CBC) mode and PKCS5 Padding. The key is hardcoded and insecure.

The encrypt function takes a plaintext and a key as input. It first creates a new AES cipher block using the key. Then it creates a slice of bytes for the ciphertext that is the size of the block size plus the size of the plaintext. The Initialization Vector (IV) is randomly generated and stored in the first block of the ciphertext.

The cipher.NewCBCEncrypter function is used to create a new CBC encrypter using the AES block and the IV. The CryptBlocks method is then called on this encrypter to encrypt the plaintext and store the result in the ciphertext.

The problem with this code is that it uses an insecure encryption algorithm
- AES with CBC mode and PKCS5 Padding. CBC mode is vulnerable to bit-flipping attacks, and PKCS5 Padding is vulnerable to padding oracle attacks. Furthermore, the key is hardcoded and can be easily discovered by an attacker.

The code should be modified to use a secure encryption algorithm, such as AES with Galois/Counter Mode (GCM), and the key should be securely generated and stored.

Steps

  • Replace the insecure encryption algorithm AES/CBC/PKCS5PADDING with a more secure algorithm such as AES/GCM or AES/CTR.
  • Generate a secure and random encryption key instead of using a hardcoded insecure key.
  • Use a secure mode of operation such as AES/GCM or AES/CTR instead of AES/CBC.
  • Ensure that the encryption algorithm and mode of operation are supported and recommended by security standards and best practices.
  • Update any other references in the codebase that use insecure encryption algorithms to use secure alternatives.

Compliant code

        package main

import (
	"crypto/aes"
	"crypto/cipher"
	"crypto/rand"
	"fmt"
	"io"
)

func main() {
	text := []byte("This is a test.")

	key := make([]byte, 32)
	if _, err := io.ReadFull(rand.Reader, key); err != nil {
		fmt.Println("Error: ", err)
		return
	}

	ciphertext, err := encrypt(text, key)
	if err != nil {
		fmt.Println("Error: ", err)
		return
	}

	fmt.Printf("%s => %x\\n", text, ciphertext)
}

func encrypt(text, key []byte) ([]byte, error) {
	block, err := aes.NewCipher(key)
	if err != nil {
		return nil, err
	}

	gcm, err := cipher.NewGCM(block)
	if err != nil {
		return nil, err
	}

	nonce := make([]byte, gcm.NonceSize())
	if _, err = io.ReadFull(rand.Reader, nonce); err != nil {
		return nil, err
	}

	ciphertext := gcm.Seal(nonce, nonce, text, nil)
	return ciphertext, nil
}

The original code was using the AES/CBC/PKCS5PADDING encryption algorithm, which is considered insecure. The key used for encryption was also hardcoded, which is a bad practice as it makes the encryption predictable and easily breakable.

The updated code now uses the AES/GCM encryption algorithm, which is considered more secure. A new key is generated for each encryption operation using the crypto/rand package, which generates a cryptographically secure random number. This makes the encryption more secure as the key is unpredictable and unique for each encryption operation.

The cipher.NewGCM function is used to create a new GCM (Galois/Counter Mode) cipher. This mode of operation is secure and recommended for modern applications.

The gcm.Seal function is used to encrypt the plaintext and append the result to the nonce, creating the final ciphertext. The nonce is also generated using a cryptographically secure random number generator.

This updated code ensures that the encryption is secure and adheres to modern security standards and best practices.

References