Insecure deserialization

Need

Secure deserialization process

Context

• Usage of Go 1.15 for building high-performance and scalable applications
• Usage of Gin framework for building web applications in Go
• Usage of encoding/json for encoding and decoding JSON data

Description

Non compliant code

package main

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

type User struct {
	Name  string `json:"name"`
	Email string `json:"email"`
}

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

	r.POST("/user", func(c *gin.Context) {
		var user User
		err := json.NewDecoder(c.Request.Body).Decode(&user)
		if err != nil {
			c.JSON(400, gin.H{
				"error": "Invalid request",
			})
			return
		}

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

	r.Run()
}

The above Go code is a simple server using the Gin framework that accepts a POST request to the /user endpoint. The request body is expected to be a JSON representation of a User object, which is then deserialized into the User struct.

The vulnerability lies in the fact that the code does not validate the content of the deserialized object nor does it cast the object to a specific type before deserializing it. This means that an attacker could potentially send a malicious JSON object that, when deserialized, could lead to unexpected behavior or even remote code execution.

This is a classic example of an Insecure Deserialization vulnerability because the application blindly trusts the incoming data and does not enforce any type of validation or type checking. As a result, an attacker could exploit this vulnerability to compromise the application or to gain unauthorized access to sensitive data.

Steps

• Validate the deserialized object before using it.
• Cast the deserialized object to a specific type to ensure its integrity.
• Implement a whitelist or blacklist approach to restrict the types of objects that can be deserialized.
• Use a secure serialization library that provides built-in protection against insecure deserialization.
• Ensure that the deserialization process is performed in a secure and controlled environment.
• Regularly update and patch the serialization library to benefit from the latest security enhancements.

Compliant code

package main

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

type User struct {
	Name  string `json:"name"`
	Email string `json:"email"`
}

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

	r.POST("/user", func(c *gin.Context) {
		var user User
		err := json.NewDecoder(c.Request.Body).Decode(&user)
		if err != nil {
			c.JSON(http.StatusBadRequest, gin.H{
				"error": "Invalid request",
			})
			return
		}

		// Validate the deserialized object
		if user.Name == "" || user.Email == "" {
			c.JSON(http.StatusBadRequest, gin.H{
				"error": "Invalid user data",
			})
			return
		}

		c.JSON(http.StatusOK, gin.H{
			"message": "User created successfully",
		})
	})

	r.Run()
}

The original code was vulnerable to insecure deserialization as it did not validate the deserialized object before using it. This could potentially allow an attacker to inject malicious data into the deserialized object, leading to various security issues such as remote code execution, denial of service, or data tampering.

The fixed code mitigates this vulnerability by validating the deserialized User object before using it. Specifically, it checks if the Name and Email fields are not empty. If either of these fields is empty, the code returns a 400 Bad Request response, indicating that the provided user data is invalid.

This validation ensures that the deserialized object is of the expected type and structure, thereby preventing insecure deserialization. However, it's important to note that this is a basic validation and depending on the complexity of the application, more robust validation logic may be required.

In addition to this, it's recommended to use a secure serialization library that provides built-in protection against insecure deserialization, restrict the types of objects that can be deserialized using a whitelist or blacklist approach, perform the deserialization process in a secure and controlled environment, and regularly update and patch the serialization library to benefit from the latest security enhancements.

References

• 096.Insecure deserialization