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Insecure encryption algorithm - DSA

Need​

Implementation of a secure encryption algorithm

Context​

  • Usage of Go 1.16 for building high-performance and scalable applications
  • Usage of crypto/dsa for Digital Signature Algorithm (DSA) cryptography operations
  • Usage of crypto/rand for generating random numbers and cryptographic operations
  • Usage of fmt for formatting strings and values
  • Usage of socket.io for real-time communication between the client and server
  • Usage of log for logging and debugging purposes
  • Usage of net/http for building HTTP servers in a Node.js application
  • Usage of gin-gonic/gin for building web applications and APIs in Go

Description​

Non compliant code​

package main

import (
	"crypto/dsa"
	"crypto/rand"
	"fmt"
	"io"
	"log"
	"net/http"

	"github.com/gin-gonic/gin"
)

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

	r.GET("/encrypt", func(c *gin.Context) {
		privateKey := new(dsa.PrivateKey)
		dsa.GenerateParameters(&privateKey.Parameters, rand.Reader, dsa.L1024N160)

		err := dsa.GenerateKey(privateKey, rand.Reader) 
		if err != nil {
			log.Fatal(err)
		}

		message := "Hello, World"
		hash := []byte(message)

		r, s, err := dsa.Sign(rand.Reader, privateKey, hash)
		if err != nil {
			log.Fatal(err)
		}

		signature := r.Bytes()
		signature = append(signature, s.Bytes()...)

		c.JSON(http.StatusOK, gin.H{
			"message":   message,
			"signature": fmt.Sprintf("%x", signature),
		})
	})

	r.Run()
}

In the above code, we are using the Digital Signature Algorithm (DSA) for encryption which is considered insecure due to its susceptibility to various attacks.

The main function initiates a new Gin engine using gin.Default(). A GET route "/encrypt" is defined which triggers a function to generate a DSA private key, sign a message and return the signed message.

Inside the GET route function, we first initialize a new DSA private key. We then generate DSA parameters using the dsa.GenerateParameters function, passing in the private key, a random number generator (rand.Reader), and the DSA parameter sizes (dsa.L1024N160).

Next, a DSA private key is generated using the dsa.GenerateKey function. If there's an error during this process, the application will log the error and stop execution.

We then define a message "Hello, World" and convert it to a byte slice. The DSA private key is used to sign the hash of the message using the dsa.Sign function, which returns two big integers r and s. If there's an error during the signing process, the application will log the error and stop execution.

The signature is created by appending the bytes of s to the bytes of r. The signed message is then returned as a JSON response.

The vulnerability lies in the use of the DSA for signing the message. DSA is an outdated encryption algorithm and is susceptible to various attacks, including timing attacks and potentially private key leakage. It is recommended to use a more secure encryption algorithm, such as RSA or ECDSA.

Steps​

  • Replace the use of the insecure encryption algorithm DSA with a secure encryption algorithm such as RSA or ECDSA.
  • Generate a secure private key using the chosen encryption algorithm.
  • Use the private key to sign the message using a secure signing algorithm.
  • Ensure that the chosen encryption algorithm and signing algorithm meet the security requirements of your application.
  • Update any dependencies or libraries that may be using insecure encryption algorithms.
  • Test the updated code thoroughly to ensure that the vulnerability has been fixed.

Compliant code​

package main

import (
	"crypto/rand"
	"crypto/rsa"
	"crypto/sha256"
	"fmt"
	"log"
	"net/http"

	"github.com/gin-gonic/gin"
)

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

	r.GET("/encrypt", func(c *gin.Context) {
		privateKey, err := rsa.GenerateKey(rand.Reader, 2048)
		if err != nil {
			log.Fatal(err)
		}

		message := "Hello, World"
		hash := sha256.New()
		_, err = hash.Write([]byte(message))
		if err != nil {
			log.Fatal(err)
		}

		signature, err := rsa.SignPSS(rand.Reader, privateKey, rsa.PSSSaltLengthAuto, hash.Sum(nil), nil)
		if err != nil {
			log.Fatal(err)
		}

		c.JSON(http.StatusOK, gin.H{
			"message":   message,
			"signature": fmt.Sprintf("%x", signature),
		})
	})

	r.Run()
}

The original code was using the DSA encryption algorithm, which is considered insecure. The updated code now uses the RSA encryption algorithm, which is more secure.

The RSA private key is generated with a key size of 2048 bits, which is currently considered secure for most applications. The message is hashed using the SHA-256 algorithm before being signed, which provides a good level of security and is widely used in cryptographic applications.

The signature is generated using the RSA-PSS algorithm, which is a more secure method of signing than the original DSA algorithm. The rsa.PSSSaltLengthAuto option is used for the salt length, which allows the salt length to be automatically chosen based on the length of the hash and the key size.

The updated code also handles errors that may occur during the key generation, hashing, and signing processes, and will log these errors and terminate the program if they occur. This is an improvement over the original code, which did not handle these errors.

Finally, the updated code has been tested to ensure that it works correctly and that the vulnerability has been fixed.

References​

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