Lack of data validation - OTP

Need

Implementation of data validation for OTP tokenCode parameter

Context

• Usage of Go 1.16 for building high-performance and scalable applications
• Usage of gin-gonic/gin for building web applications and APIs in Go
• Usage of net/http for creating HTTP servers in a Node.js application

Description

Non compliant code

package main

import (
	"github.com/gin-gonic/gin"
	"net/http"
)

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

	r.POST("/validateOTP", func(c *gin.Context) {
		tokenCode := c.PostForm("tokenCode")

		// Here the tokenCode is directly used without any validation
		if tokenCode == "123456" {
			c.JSON(http.StatusOK, gin.H{"status": "You are authenticated"})
		} else {
			c.JSON(http.StatusUnauthorized, gin.H{"status": "Unauthorized"})
		}
	})

	r.Run()
}

In the above code, we are creating a simple HTTP server using the Gin framework in Go. The server has a single endpoint /validateOTP which accepts a POST request. The request should contain a form parameter tokenCode.

The server checks if the tokenCode equals "123456", and if so, it returns a JSON response with a status of "You are authenticated". Otherwise, it returns a JSON response with a status of "Unauthorized".

The vulnerability here is that there is no validation of the tokenCode parameter. An attacker could potentially use random values in multiple attempts to guess the correct tokenCode. This kind of attack is commonly known as a brute force attack.

It is always a good practice to validate the inputs received from the client. In this case, the server should validate the tokenCode before using it. The validation could be as simple as checking the length of the tokenCode or it could be more complex like checking if the tokenCode is a number, has a certain pattern, or has not been used before.

Steps

• Implement input validation for the tokenCode parameter.
• Use a regular expression or a whitelist to validate the tokenCode value.
• Consider using a strong and secure algorithm for generating OTPs.
• Implement rate limiting to prevent brute force attacks on the OTP validation endpoint.
• Consider implementing a time-based expiration for the OTPs to enhance security.
• Ensure that the OTPs are securely stored and transmitted.
• Regularly review and update the validation logic to adapt to new security threats.

Compliant code

package main

import (
	"github.com/gin-gonic/gin"
	"github.com/gin-contrib/secure"
	"net/http"
	"regexp"
	"time"
)

var otpStore = make(map[string]time.Time)

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

	// Implement rate limiting middleware
	r.Use(secure.RateLimit(100, time.Minute))

	r.POST("/validateOTP", func(c *gin.Context) {
		tokenCode := c.PostForm("tokenCode")

		// Validate the tokenCode using a regular expression
		match, _ := regexp.MatchString("^[0-9]{6}$", tokenCode)
		if !match {
			c.JSON(http.StatusBadRequest, gin.H{"status": "Invalid OTP format"})
			return
		}

		// Check if the OTP is in the store and has not expired
		if otpTime, ok := otpStore[tokenCode]; ok && time.Since(otpTime) < 5*time.Minute {
			delete(otpStore, tokenCode)
			c.JSON(http.StatusOK, gin.H{"status": "You are authenticated"})
		} else {
			c.JSON(http.StatusUnauthorized, gin.H{"status": "Unauthorized"})
		}
	})

	r.Run()
}

The updated code includes several security enhancements to address the lack of data validation vulnerability in the OTP handling:

1. Input Validation: The tokenCode parameter is validated using a regular expression to ensure it is a six-digit number. This is a basic form of whitelist validation that only allows specific input formats.

2. Rate Limiting: A rate limiting middleware is used to limit the number of requests a client can make to the /validateOTP endpoint within a certain time period. This helps to prevent brute force attacks.

3. OTP Expiration: OTPs are stored in a map along with their creation time. When an OTP is validated, the code checks if it is in the map and if it has not expired (i.e., it was created within the last 5 minutes). This enhances security by ensuring OTPs cannot be used indefinitely.

4. Secure Storage and Transmission: Although not explicitly shown in the code, it is recommended to ensure that OTPs are securely stored and transmitted. This could involve encrypting the OTPs in the store and using secure communication protocols (e.g., HTTPS) to transmit them.

5. Regular Review and Update: While not part of the code itself, it is important to regularly review and update the validation logic to adapt to new security threats. This could involve updating the regular expression used for validation, adjusting the rate limit, or changing the OTP expiration time.

References

• 341.Lack of data validation - OTP