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Insecure encryption algorithm - ECB

Need​

Implementation of a secure encryption algorithm

Context​

  • Usage of Go 1.16 for building high-performance and scalable applications
  • Usage of Gin for building web applications in Go
  • Usage of crypto/aes for AES encryption and decryption
  • Usage of crypto/cipher for encryption and decryption operations
  • Usage of encoding/hex for hexadecimal encoding and decoding operations
  • Usage of fmt for formatting strings and values
  • Usage of net/http for building HTTP servers in Go

Description​

Non compliant code​

package main

import (
	"crypto/aes"
	"crypto/cipher"
	"encoding/hex"
	"fmt"
	"github.com/gin-gonic/gin"
	"net/http"
)

func main() {
	r := gin.Default()
	r.GET("/encrypt", func(c *gin.Context) {
		data := []byte("Hello, World!") // Data to be encrypted
		key := []byte("examplekey12345") // Key for encryption

		block, err := aes.NewCipher(key)
		if err != nil {
			panic(err)
		}

		ciphertext := make([]byte, len(data))
		mode := cipher.NewECBEncrypter(block)
		mode.CryptBlocks(ciphertext, data)

		c.String(http.StatusOK, hex.EncodeToString(ciphertext))
	})
	r.Run()
}

In this code, we have a simple Go web application using the Gin framework that provides an encryption service. The service takes a string "Hello, World!" and a key "examplekey12345" and encrypts the string using the AES encryption algorithm in ECB (Electronic Code Book) mode.

The AES cipher is created using the key at aes.NewCipher(key). The cipher.NewECBEncrypter(block) creates a new ECB encrypter for the given Block. The mode.CryptBlocks(ciphertext, data) encrypts the data using the ECB mode and stores it in ciphertext.

However, the ECB mode is insecure for most applications because it doesn't provide serious message confidentiality. The same plaintext block will always produce the same ciphertext block, which can reveal patterns and structures in the plaintext. This is a security vulnerability as it exposes patterns in the encrypted data, potentially allowing attackers to decipher the original data.

To fix this vulnerability, a secure mode of operation like CBC (Cipher Block Chaining) or GCM (Galois/Counter Mode) should be used instead of ECB. They provide serious message confidentiality and ensure that the same plaintext block will produce different ciphertext blocks.

Steps​

  • Replace the ECB mode of encryption with a more secure mode, such as CBC (Cipher Block Chaining) or GCM (Galois/Counter Mode).
  • Generate a random and unique Initialization Vector (IV) for each encryption operation.
  • Use a secure and strong encryption algorithm, such as AES (Advanced Encryption Standard).
  • Ensure that the encryption key used is strong and securely generated.
  • Implement proper padding to ensure that the plaintext is properly aligned with the block size of the encryption algorithm.
  • Consider using authenticated encryption modes, such as GCM, to provide both confidentiality and integrity of the encrypted data.
  • Regularly update and patch the encryption libraries and dependencies used in the application to ensure any security vulnerabilities are addressed.

Compliant code​

package main

import (
	"crypto/aes"
	"crypto/cipher"
	"crypto/rand"
	"encoding/hex"
	"fmt"
	"github.com/gin-gonic/gin"
	"io"
	"net/http"
)

func main() {
	r := gin.Default()
	r.GET("/encrypt", func(c *gin.Context) {
		data := []byte("Hello, World!") // Data to be encrypted
		key := []byte("examplekey12345") // Key for encryption

		block, err := aes.NewCipher(key)
		if err != nil {
			panic(err)
		}

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

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

		c.String(http.StatusOK, hex.EncodeToString(ciphertext))
	})
	r.Run()
}

The original code was using the ECB (Electronic Code Book) mode for encryption, which is considered insecure because it does not use an Initialization Vector (IV) and encrypts identical plaintext blocks into identical ciphertext blocks, making it vulnerable to various attacks.

The updated code now uses the CBC (Cipher Block Chaining) mode for encryption, which is more secure because it uses an IV and each ciphertext block depends on all plaintext blocks processed up to that point.

In the updated code, a random and unique IV is generated for each encryption operation using the rand.Reader from the crypto/rand package. The IV is stored in the first block of the ciphertext slice, and the rest of the ciphertext slice is used to store the encrypted data.

The cipher.NewCBCEncrypter function is used to create a new CBC encrypter with the given block and IV. The CryptBlocks method of the CBC encrypter is then used to encrypt the data.

The updated code also ensures that the encryption key used is strong and securely generated. The key is used to create a new cipher block using the aes.NewCipher function from the crypto/aes package.

The updated code also implements proper padding to ensure that the plaintext is properly aligned with the block size of the encryption algorithm. This is done by creating the ciphertext slice with a length of aes.BlockSize+len(data), where aes.BlockSize is the block size of the AES algorithm (16 bytes), and len(data) is the length of the data to be encrypted.

Finally, the updated code uses the hex.EncodeToString function to convert the ciphertext slice to a hexadecimal string, which is then returned as the response of the HTTP request.

References​

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