Need

Secure token generation mechanism

Context

• Usage of Go 1.16 for building high-performance and scalable applications
• Usage of gin-gonic/gin for building web applications in Go

Description

Non compliant code

        package main

import (
	"github.com/gin-gonic/gin"
	"math/rand"
	"time"
)

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

	r.GET("/generate-token", func(c *gin.Context) {
		token := generateToken()
		c.JSON(200, gin.H{
			"token": token,
		})
	})

	r.Run()
}

func generateToken() string {
	rand.Seed(time.Now().UnixNano())
	token := rand.Int()
	return string(token)
}
        
        

The above code is a simple Go application using the Gin framework. It has a single endpoint ( /generate-token) that generates a token and returns it in the response.

The vulnerability lies in the generateToken function. It uses the math/rand package to generate a pseudo-random number and then converts it into a string. This number is then used as a token.

The math/rand package is not cryptographically secure. The numbers it generates are predictable if the seed is known. In this case, the seed is the current time ( time.Now().UnixNano()), which is also predictable.

This means that an attacker could predict the tokens that this function will generate and use them to impersonate other users or gain unauthorized access to resources.

Moreover, the tokens are not hashed, so if an attacker can intercept the communication between the client and the server, they can read the tokens directly.

To mitigate this vulnerability, you should use a cryptographically secure random number generator and hash the tokens before sending them to the client.

Steps

• Use a secure cryptographic mechanism to generate the token.
• Avoid using predictable or easily guessable values for the token.
• Ensure that the token has sufficient entropy to make it difficult to crack.
• Consider using a library or framework-provided function for generating secure tokens.
• Regularly update the token generation mechanism to incorporate any new security best practices or recommendations.

Compliant code

        package main

import (
	"crypto/rand"
	"encoding/base64"
	"github.com/gin-gonic/gin"
)

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

	r.GET("/generate-token", func(c *gin.Context) {
		token, err := generateToken()
		if err != nil {
			c.JSON(500, gin.H{
				"message": "Error generating token",
			})
			return
		}
		c.JSON(200, gin.H{
			"token": token,
		})
	})

	r.Run()
}

func generateToken() (string, error) {
	b := make([]byte, 32)
	_, err := rand.Read(b)
	if err != nil {
		return "", err
	}
	token := base64.StdEncoding.EncodeToString(b)
	return token, nil
}
        
        

The previous code was vulnerable because it used the math/rand package to generate tokens. This package is not suitable for generating secure tokens because it is not cryptographically secure. The tokens it generates can be predictable and easily guessable, which makes them susceptible to attacks.

The fixed code uses the crypto/rand package to generate tokens. This package is a cryptographically secure random number generator. It generates random bytes and then encodes them into a base64 string to create the token. This makes the tokens unpredictable and difficult to guess, which enhances their security.

The generateToken function now returns an error along with the token. This allows the function to handle any errors that occur during the token generation process. If an error occurs, the function returns the error and an empty string. The error is then checked in the route handler, and if an error occurred, a 500 response is sent to the client with a message indicating that there was an error generating the token.

This approach ensures that the tokens are generated in a secure manner and that any errors that occur during the token generation process are properly handled.

References

• 078. Insecurely generated token