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Insecure encryption algorithm - Blowfish

Need​

Secure encryption algorithm for protecting sensitive information

Context​

  • Usage of Go 1.16 for developing high-performance and efficient applications
  • Usage of gin-gonic/gin for building web applications in Go
  • Usage of blowfish encryption algorithm from golang.org/x/crypto/blowfish for secure data encryption

Description​

Non compliant code​

package main

import (
	"github.com/gin-gonic/gin"
	"golang.org/x/crypto/blowfish"
)

func main() {
	r := gin.Default()

	r.POST("/encrypt", func(c *gin.Context) {
		data := c.PostForm("data")
		key := []byte("example key 1234")

		cipher, err := blowfish.NewCipher(key)
		if err != nil {
			c.JSON(500, gin.H{
				"message": "Error in encryption",
			})
			return
		}

		src := []byte(data)
		dst := make([]byte, len(src))

		cipher.Encrypt(dst, src)

		c.JSON(200, gin.H{
			"message": "Data encrypted successfully",
			"data":    dst,
		})
	})

	r.Run()
}

In the provided code, we have a simple Go web server using the Gin framework. The server has an endpoint "/encrypt" that accepts POST requests. The endpoint takes a "data" field from the form data of the request and encrypts it using the Blowfish encryption algorithm.

The Blowfish encryption is done in the following steps:

  1. A key is defined for the Blowfish cipher. In this case, the key is a hard-coded string "example key 1234".

  2. A new Blowfish cipher is created with the defined key.

  3. The data to be encrypted is converted to bytes.

  4. A byte slice is created to hold the encrypted data.

  5. The Encrypt method of the Blowfish cipher is used to encrypt the data. The encrypted data is stored in the created byte slice.

  6. The server responds with a success message and the encrypted data.

The vulnerability in this code is the use of the insecure Blowfish encryption algorithm. Blowfish is a symmetric-key block cipher that is known to be vulnerable to attacks such as birthday attacks and other forms of cryptanalysis. Therefore, it is not recommended for use in new systems.

Steps​

  • Replace the insecure encryption algorithm (Blowfish) with a secure encryption algorithm such as AES.
  • Use a secure key generation method to generate the encryption key.
  • Ensure that the encryption key is stored securely and not hardcoded in the code.
  • Implement proper error handling for encryption operations.
  • Consider using a secure encryption mode such as AES-GCM for authenticated encryption.
  • Regularly update the encryption algorithm and key management practices to stay up-to-date with the latest security standards.

Compliant code​

package main

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

func main() {
	r := gin.Default()

	r.POST("/encrypt", func(c *gin.Context) {
		data := c.PostForm("data")
		key := generateKey()

		block, err := aes.NewCipher(key)
		if err != nil {
			c.JSON(500, gin.H{
				"message": "Error in encryption",
			})
			return
		}

		aesGCM, err := cipher.NewGCM(block)
		if err != nil {
			c.JSON(500, gin.H{
				"message": "Error in encryption",
			})
			return
		}

		nonce := make([]byte, aesGCM.NonceSize())
		if _, err = io.ReadFull(rand.Reader, nonce); err != nil {
			c.JSON(500, gin.H{
				"message": "Error in encryption",
			})
			return
		}

		ciphertext := aesGCM.Seal(nonce, nonce, []byte(data), nil)

		c.JSON(200, gin.H{
			"message": "Data encrypted successfully",
			"data":    hex.EncodeToString(ciphertext),
		})
	})

	r.Run()
}

func generateKey() []byte {
	key := make([]byte, 32)
	if _, err := rand.Read(key); err != nil {
		panic(err.Error())
	}
	return key
}

The above code replaces the insecure Blowfish encryption algorithm with the secure AES encryption algorithm. The AES encryption algorithm is currently one of the most secure encryption algorithms and is widely used in many security-critical applications.

The generateKey function is used to generate a secure random key for the AES encryption. This key is 32 bytes long, which corresponds to a 256-bit key size. This is the maximum key size for AES and provides a very high level of security.

The AES encryption is used in GCM (Galois/Counter Mode), which is an authenticated encryption mode. This means that it not only provides confidentiality, but also ensures the integrity and authenticity of the data.

The Seal function encrypts and authenticates the data, and also appends the result to the nonce. The nonce is a random number that is used only once, and it is generated for each encryption operation to ensure the uniqueness of each ciphertext.

The key is not hardcoded in the code, but is generated for each encryption operation. This is a good practice as it prevents the key from being exposed in the code. However, in a real-world application, you would typically use a securely stored key and not generate a new key for each operation.

The error handling has been improved to handle any errors that may occur during the encryption operation. If an error occurs, a 500 status code is returned along with a message indicating that an error occurred in the encryption.

This code should be regularly reviewed and updated to ensure that it continues to follow the latest security standards and best practices.

References​

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