Business information leak - Token

Need

Protection of user information in session tokens

Context

• Usage of Go 1.16 for developing high-performance and efficient applications
• Usage of Gin framework for building web applications 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"
)

type User struct {
	Username string `json:"username"`
	FullName string `json:"fullname"`
	Email    string `json:"email"`
}

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

	r.POST("/login", func(c *gin.Context) {
		var user User
		if err := c.ShouldBindJSON(&user); err != nil {
			c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
			return
		}

		// Assume user authentication is successful
		// For simplicity, we are not checking the user credentials here
		token := user.Username + ":" + user.Email + ":" + user.FullName

		c.JSON(200, gin.H{
			"message": "User logged in successfully",
			"token":   token,
		})
	})

	r.Run()
}

In the above code, we are handling a POST request to the "/login" endpoint. The user sends their login details (username, fullname, and email) in the request body. After the user is authenticated, we generate a session token for the user.

The vulnerability lies in the token generation part. We are concatenating the username, email, and fullname to generate the token. This means that the token contains sensitive user information. Anyone who has access to this token can extract the username, email, and fullname of the user. This is a serious security issue as it leads to a business information leak.

In a real-world scenario, the token should not contain any sensitive user information. It should be a random string that can be used to identify the user session. The token should also be stored securely on the server side and should be sent to the user over a secure connection (HTTPS).

Steps

• Do not include sensitive information in the session token.
• Separate the session token from the user information.
• Store the user information securely on the server-side.
• Generate a unique session token for each user upon successful authentication.
• Use a secure token generation algorithm to prevent token guessing or brute-force attacks.
• Encrypt the session token to protect it from unauthorized access.
• Implement proper access controls to restrict access to sensitive user information.

Compliant code

package main

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

type User struct {
	Username string `json:"username"`
	FullName string `json:"fullname"`
	Email    string `json:"email"`
}

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

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

	r.POST("/login", func(c *gin.Context) {
		var user User
		if err := c.ShouldBindJSON(&user); err != nil {
			c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
			return
		}

		// Assume user authentication is successful
		// For simplicity, we are not checking the user credentials here
		token, err := generateToken()
		if err != nil {
			c.JSON(http.StatusInternalServerError, gin.H{"error": "Error generating token"})
			return
		}

		c.JSON(200, gin.H{
			"message": "User logged in successfully",
			"token":   token,
		})
	})

	r.Run()
}

The original code was vulnerable because it included sensitive user information (username, email, and full name) in the session token. This could lead to a business information leak if the token was intercepted or otherwise accessed by an unauthorized party.

The fixed code addresses this vulnerability by generating a unique, random session token for each user upon successful authentication. This token does not contain any user information. The generateToken function uses the crypto/rand package to generate a random 32-byte value, which is then base64-encoded to create the token. This approach helps to prevent token guessing or brute-force attacks.

The user information is now stored securely on the server-side (not shown in this code snippet). Proper access controls should be implemented to restrict access to this sensitive information.

In addition, the fixed code includes error handling for the token generation process. If an error occurs while generating the token, the server responds with a 500 Internal Server Error status code and an appropriate error message. This helps to ensure that the user is not logged in with an invalid or missing token.

References

• 220.Business information leak - Token