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Insecure authentication method - NTLM

Need​

Implementation of a secure authentication method

Context​

  • Usage of Go 1.16 for building high-performance and concurrent applications
  • Usage of Gin for building web applications in Go
  • Usage of go-ntlm/ntlm for NTLM authentication in Go programming language
  • 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"
	"github.com/thekidinme/go-ntlm/ntlm"
	"net/http"
)

func main() {
	r := gin.Default()
	r.Use(NTLMMiddleware)
	r.GET("/", func(c *gin.Context) {
		c.String(http.StatusOK, "Hello, World!")
	})
	r.Run()
}

func NTLMMiddleware(c *gin.Context) {
	ntlm := ntlm.New("DOMAIN", "USERNAME", "PASSWORD")
	req, _ := http.NewRequest("GET", "http://example.com", nil)
	ntlm.Do(req)
	c.Next()
}

In the above Go code, we are using the Gin framework to build a web application. The NTLM (New Technology LAN Manager) authentication is implemented as a middleware function (NTLMMiddleware) which is used to authenticate every request.

The NTLM authentication is done using the ntlm.New("DOMAIN", "USERNAME", "PASSWORD") function which takes in the domain, username, and password as arguments. This function is provided by the github.com/thekidinme/go-ntlm/ntlm package.

This approach to authentication is insecure because NTLM is a legacy protocol with several known vulnerabilities. Some of the security flaws associated with NTLM include:

  1. Relay Attacks: An attacker can intercept the NTLM messages during the authentication process and use them to impersonate the user's session to other servers.

  2. Man in the Middle Attacks: An attacker can intercept and alter the communication between two parties without their knowledge. This can lead to unauthorized access or data leaks.

  3. Brute Force Attacks: NTLM uses weak encryption that can be cracked by brute force attacks to obtain valid challenge responses.

Therefore, it is recommended to replace NTLM with a more secure authentication method such as Kerberos or OAuth.

Steps​

  • Replace the use of NTLM authentication with a more secure authentication method, such as OAuth or JWT.
  • Implement strong password policies and enforce the use of complex passwords.
  • Enable multi-factor authentication to add an extra layer of security.
  • Regularly update and patch the application and its dependencies to ensure that any security vulnerabilities are addressed.
  • Implement secure communication protocols, such as HTTPS, to protect sensitive data during transmission.
  • Implement rate limiting and account lockout mechanisms to prevent brute force attacks.
  • Educate users about the importance of strong passwords and the risks associated with insecure authentication methods.

Compliant code​

package main

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

var jwtKey = []byte("your_secret_key")

type Claims struct {
	Username string `json:"username"`
	jwt.StandardClaims
}

func main() {
	r := gin.Default()
	r.Use(AuthMiddleware)
	r.GET("/", func(c *gin.Context) {
		c.String(http.StatusOK, "Hello, World!")
	})
	r.Run()
}

func AuthMiddleware(c *gin.Context) {
	tokenString := c.GetHeader("Authorization")
	claims := &Claims{}

	token, err := jwt.ParseWithClaims(tokenString, claims, func(token *jwt.Token) (interface{}, error) {
		return jwtKey, nil
	})

	if err != nil {
		c.JSON(http.StatusUnauthorized, "Unauthorized")
		return
	}

	if !token.Valid {
		c.JSON(http.StatusUnauthorized, "Unauthorized")
		return
	}

	c.Next()
}

The above code replaces the insecure NTLM authentication with JWT (JSON Web Tokens) which is a more secure method of authentication.

In the main function, we use the AuthMiddleware function as a middleware that will be executed before the main handler function. This middleware function is responsible for validating the JWT token that should be sent in the Authorization header of the request.

The AuthMiddleware function retrieves the token from the Authorization header and then uses the jwt.ParseWithClaims function to validate it. If the token is not valid or if an error occurs during the validation process, the function responds with a 401 Unauthorized status code. If the token is valid, the function calls c.Next() to pass the request to the next handler function.

Please note that you should replace "your_secret_key" with your own secret key. This key is used to sign the JWT tokens and should be kept secret.

This code does not include the implementation of the login route that should handle the generation of the JWT tokens when the user provides valid credentials. You should implement this route and ensure that the user's password is securely hashed before it is stored in your database.

Remember to enforce strong password policies and enable multi-factor authentication to add an extra layer of security. Regularly update and patch your application and its dependencies to address any security vulnerabilities. Implement secure communication protocols, such as HTTPS, to protect sensitive data during transmission. Implement rate limiting and account lockout mechanisms to prevent brute force attacks. Educate your users about the importance of strong passwords and the risks associated with insecure authentication methods.

References​

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