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Insecure encryption algorithm - TripleDES

Need​

Implementation of secure encryption algorithms and modes

Context​

  • Usage of Go 1.16 for developing scalable and efficient applications
  • Usage of crypto/cipher for encryption and decryption operations
  • Usage of crypto/des for Data Encryption Standard (DES) cryptography operations
  • Usage of gin-gonic/gin for building web applications in Go
  • Usage of log for logging messages and debugging purposes
  • Usage of net/http for creating HTTP servers in a Node.js application

Description​

Non compliant code​

package main

import (
	"crypto/cipher"
	"crypto/des"
	"github.com/gin-gonic/gin"
	"log"
	"net/http"
)

func main() {
	r := gin.Default()
	r.POST("/encrypt", func(c *gin.Context) {
		plaintext := c.PostForm("plaintext")
		key := []byte("supersecretkey") // This should be a secret!
		block, err := des.NewTripleDESCipher(key)
		if err != nil {
			log.Fatal(err)
		}

		ciphertext := make([]byte, len(plaintext))
		mode := cipher.NewCBCEncrypter(block, key[:des.BlockSize])
		mode.CryptBlocks(ciphertext, []byte(plaintext))

		c.String(http.StatusOK, string(ciphertext))
	})

	r.Run() // listen and serve on 0.0.0.0:8080
}

The above code snippet is a simple encryption server using the Gin framework in Go. It accepts a POST request to the "/encrypt" endpoint with a plaintext message in the form data, then encrypts the message using the Triple DES algorithm in ECB mode.

The encryption is performed by the des.NewTripleDESCipher(key) function, which creates a new cipher.Block. A cipher.Block represents a block cipher running in a block-based mode (like CBC, ECB, OFB, CFB), using the given key.

The encryption key is hard-coded as supersecretkey and is passed as a byte slice to the function. This key is used to create a new cipher block.

The cipher.NewCBCEncrypter(block, key[:des.BlockSize]) function creates a new cipher.BlockMode which encrypts in cipher block chaining mode, using the given Block. The key[:des.BlockSize] is used as the initialization vector.

The mode.CryptBlocks(ciphertext, []byte(plaintext)) function encrypts or decrypts a number of blocks. The length of the plaintext must be a multiple of the block size. The ciphertext and plaintext may alias exactly if and only if the block cipher is being used in ECB mode.

Finally, the encrypted text is returned as a response to the POST request.

The vulnerability here lies in the use of the insecure Triple DES algorithm for encryption and the hard-coded encryption key. Triple DES is considered to be insecure due to its short block size and susceptibility to certain attacks, such as the Sweet32 attack. Additionally, using a hard-coded encryption key is a bad practice because if the key is compromised, all data encrypted with that key is at risk.

Steps​

  • Replace the use of TripleDES with a more secure encryption algorithm, such as AES.
  • Ensure that the encryption key used is strong and securely stored.
  • Use a secure mode of operation for the encryption algorithm, such as CBC (Cipher Block Chaining) mode.
  • Implement proper padding for the plaintext to ensure secure encryption.
  • Regularly update the encryption library and dependencies to stay protected against known vulnerabilities.

Compliant code​

package main

import (
	"crypto/aes"
	"crypto/cipher"
	"crypto/rand"
	"encoding/base64"
	"github.com/gin-gonic/gin"
	"io"
	"log"
	"net/http"
)

func main() {
	r := gin.Default()
	r.POST("/encrypt", func(c *gin.Context) {
		plaintext := c.PostForm("plaintext")
		key := []byte("supersecretkey") // This should be a secret!
		block, err := aes.NewCipher(key)
		if err != nil {
			log.Fatal(err)
		}

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

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

		c.String(http.StatusOK, base64.StdEncoding.EncodeToString(ciphertext))
	})

	r.Run() // listen and serve on 0.0.0.0:8080
}

The above code is a fixed version of the original vulnerable code. The main changes are:

  1. AES Encryption Algorithm: The insecure TripleDES encryption algorithm has been replaced with the more secure AES (Advanced Encryption Standard) algorithm.

  2. Random Initialization Vector (IV): A random IV is generated for each encryption operation, which is a recommended practice for ensuring the security of CBC mode.

  3. Base64 Encoding: The encrypted ciphertext is encoded using Base64 before being sent in the response. This ensures that the ciphertext can be safely transmitted and stored, as it may contain non-printable characters.

  4. Key Management: The encryption key is still hardcoded in this example, which is not a secure practice. In a real-world application, the key should be securely generated and stored, and should not be hardcoded into the application code.

  5. Error Handling: Proper error handling is implemented to ensure that any issues with the encryption operation are caught and handled appropriately.

  6. Library Updates: Although not shown in the code, it's important to regularly update the encryption library and any other dependencies to ensure protection against known vulnerabilities.

References​

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