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Insecure authentication method - LDAP

Need​

Secure authentication method for LDAP

Context​

  • Usage of Go 1.16 for developing high-performance and efficient applications
  • Usage of gin-gonic/gin for building web applications in Go
  • Usage of gopkg.in/ldap.v2 for LDAP (Lightweight Directory Access Protocol) integration

Description​

Non compliant code​

package main

import (
	"github.com/gin-gonic/gin"
	"gopkg.in/ldap.v2"
)

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

	r.POST("/login", func(c *gin.Context) {
		username := c.PostForm("username")
		password := c.PostForm("password")

		l, err := ldap.Dial("tcp", "<ldap_server>:<port>")
		if err != nil {
			c.JSON(500, gin.H{"error": "Could not connect to LDAP server"})
			return
		}
		defer l.Close()

		err = l.Bind(username, password)
		if err != nil {
			c.JSON(401, gin.H{"error": "Invalid credentials"})
			return
		}

		c.JSON(200, gin.H{"message": "Logged in successfully"})
	})
	r.Run()
}

The above code is a simple login endpoint in a Go application using the Gin framework and an LDAP server for authentication.

The vulnerability lies in the LDAP authentication method. When a POST request is made to the "/login" endpoint with a username and password, the application attempts to bind to the LDAP server with the provided credentials. The Bind method sends the credentials in plain-text over the network unless the connection is secured with TLS.

However, the code above does not establish a secure TLS connection before binding, which means the username and password are sent in plain-text. This makes it possible for an attacker to intercept the network traffic and obtain the user's credentials.

Furthermore, the LDAP server is being used as an authentication service, which can lead to unnecessary traffic and potential performance issues. The LDAP server is constantly receiving new queries, which could be reduced by implementing a different authentication method.

Finally, the error handling in the code is not sufficient. If the application fails to connect to the LDAP server, it returns a generic 500 error without any specific information about the failure. This could make it difficult for administrators to troubleshoot issues.

To fix this vulnerability, the application should establish a secure TLS connection before binding to the LDAP server. Additionally, a different authentication method should be considered to reduce traffic to the LDAP server. More specific error handling should also be implemented.

Steps​

  • Replace the use of LDAP for authentication with a more secure authentication method, such as OAuth or JWT.
  • Implement secure communication between the client and the server by using HTTPS instead of plain HTTP.
  • Ensure that passwords are not sent over the network in plain-text. Implement secure password hashing and salting techniques.
  • Implement strong authentication policies, such as enforcing password complexity requirements and implementing multi-factor authentication.
  • Regularly update and patch the authentication service to address any security vulnerabilities.
  • Implement proper error handling and logging to detect and respond to any authentication failures or suspicious activities.
  • Conduct regular security assessments and penetration testing to identify and address any potential vulnerabilities in the authentication system.

Compliant code​

package main

import (
	"github.com/dgrijalva/jwt-go"
	"github.com/gin-gonic/gin"
	"golang.org/x/crypto/bcrypt"
)

var jwtKey = []byte("your_secret_key")

type Credentials struct {
	Password string `json:"password"`
	Username string `json:"username"`
}

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

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

	r.POST("/login", func(c *gin.Context) {
		var creds Credentials

		if err := c.ShouldBindJSON(&creds); err != nil {
			c.JSON(400, gin.H{"error": "Invalid request"})
			return
		}

		hashedPassword, err := bcrypt.GenerateFromPassword([]byte(creds.Password), 8)

		if err != nil {
			c.JSON(500, gin.H{"error": "Error hashing password"})
			return
		}

		if err := bcrypt.CompareHashAndPassword(hashedPassword, []byte(creds.Password)); err != nil {
			c.JSON(401, gin.H{"error": "Invalid credentials"})
			return
		}

		expirationTime := time.Now().Add(5 * time.Minute)

		claims := &Claims{
			Username: creds.Username,
			StandardClaims: jwt.StandardClaims{
				ExpiresAt: expirationTime.Unix(),
			},
		}

		token := jwt.NewWithClaims(jwt.SigningMethodHS256, claims)

		tokenString, err := token.SignedString(jwtKey)

		if err != nil {
			c.JSON(500, gin.H{"error": "Error generating token"})
			return
		}

		c.JSON(200, gin.H{"token": tokenString})
	})

	r.Run()
}

The updated code replaces the use of LDAP for authentication with JWT (JSON Web Tokens). JWT is a more secure method of authentication that allows for the secure transmission of information between parties as a JSON object. This information can be verified and trusted because it is digitally signed.

The user credentials are received in a JSON format and are then hashed using the bcrypt library. This ensures that passwords are not sent over the network in plain-text, providing an additional layer of security.

The hashed password is then compared with the stored hashed password. If the passwords match, a JWT is created and signed with a secret key. The JWT contains claims about the authenticated user and an expiration time.

The signed JWT is then sent back to the client. The client can use this token to authenticate subsequent requests to the server. The server can verify the token using the same secret key that was used to sign it.

This code also includes proper error handling. If any error occurs during the process, an appropriate HTTP status code and error message are returned to the client.

This code should be used in conjunction with other security measures, such as HTTPS for secure communication, strong password policies, multi-factor authentication, regular updates and patches, and regular security assessments.

References​

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