Lack of data validation - Responses - Go

Need

Implementation of robust data validation for response data

Context

1. Usage of Go 1.16 for building efficient and scalable applications
2. Usage of Gin framework for building web applications in Go

Description

Insecure Code Example

package main

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

type User struct {
	ID   string `json:"id"`
	Name string `json:"name"`
}

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

	r.GET("/user/:id", func(c *gin.Context) {
		userID := c.Param("id")
		// assume we get the user data from database
		user := User{ID: userID, Name: "John Doe"}
		c.JSON(200, gin.H{
			"user": user,
		})
	})

	r.POST("/updateUser", func(c *gin.Context) {
		var user User
		if err := c.ShouldBindJSON(&user); err != nil {
			c.JSON(400, gin.H{"error": err.Error()})
			return
		}
		// assume we update the user data in database
		c.JSON(200, gin.H{
			"message": "User updated successfully",
		})
	})

	r.Run()
}

The above Go code represents a simple backend application using the Gin framework. It has two endpoints. The first endpoint `/user/:id` is a GET method that retrieves the user's information based on the user id passed in the URL. The second endpoint `/updateUser` is a POST method that updates the user's information based on the JSON data sent in the request body. The vulnerability here lies in the `/updateUser` endpoint. The endpoint takes the user's information from the request without validating the data. This means that if a response from the `/user/:id` endpoint is manipulated and sent as a request to the `/updateUser` endpoint, the application will accept the manipulated data without any validation. For example, if a malicious actor changes the user's ID in the response from the `/user/:id` endpoint to an invalid ID and sends it as a request to the `/updateUser` endpoint, the application will update the user's information with the invalid ID without any validation. This can lead to various issues such as data inconsistency or even data corruption.

Steps

1. Implement data validation on the server-side to ensure the integrity and validity of the received data.
2. Validate the data received in the POST `/updateUser` endpoint before updating the user data in the database.
3. Use appropriate validation techniques such as input sanitization, data type validation, length validation, and format validation.
4. Handle validation errors properly and return meaningful error messages to the client.
5. Consider using a validation library or framework to simplify the validation process.
6. Avoid relying solely on client-side validation as it can be bypassed.
7. Regularly review and update the validation logic to adapt to changing requirements and potential new vulnerabilities.

Secure Code Example

package main

import (
	"github.com/gin-gonic/gin"
	"github.com/go-playground/validator/v10"
)

type User struct {
	ID   string `json:"id" validate:"required,uuid"`
	Name string `json:"name" validate:"required"`
}

var validate *validator.Validate

func main() {
	r := gin.Default()
	validate = validator.New()

	r.GET("/user/:id", func(c *gin.Context) {
		userID := c.Param("id")
		// assume we get the user data from database
		user := User{ID: userID, Name: "John Doe"}
		c.JSON(200, gin.H{
			"user": user,
		})
	})

	r.POST("/updateUser", func(c *gin.Context) {
		var user User
		if err := c.ShouldBindJSON(&user); err != nil {
			c.JSON(400, gin.H{"error": err.Error()})
			return
		}

		// Validate the data
		err := validate.Struct(user)
		if err != nil {
			c.JSON(400, gin.H{"error": err.Error()})
			return
		}

		// assume we update the user data in database
		c.JSON(200, gin.H{
			"message": "User updated successfully",
		})
	})

	r.Run()
}

The updated code now includes data validation for the `User` struct using the `validator` package. The `User` struct now includes `validate` tags that specify the validation rules for each field. The `ID` field is required and must be a valid UUID, and the `Name` field is required. In the `main` function, a new `validator.Validate` instance is created and assigned to the global `validate` variable. This instance is used to validate the `User` data in the `POST /updateUser` endpoint. In the `POST /updateUser` endpoint, after binding the JSON request body to the `User` struct, the `User` data is validated using the `validate.Struct` method. If the validation fails, an error message is returned to the client with a 400 status code, and the function returns immediately. If the validation succeeds, the user data is updated in the database. This update ensures that only valid `User` data is accepted and processed by the server, preventing potential issues caused by invalid data.

References

Last updated

2023/09/18