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Insufficient data authenticity validation

Need​

Enhanced data authenticity validation and verification

Context​

  • Usage of Go 1.16 for developing scalable and efficient applications
  • Usage of gin-gonic/gin for building web applications and APIs in Go
  • Usage of net/http for creating a web server in a Node.js application

Description​

Non compliant code​

package main

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

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

func main() {
    r := gin.Default()
    r.POST("/update", func(c *gin.Context) {
        var user User
        if err := c.ShouldBindJSON(&user); err != nil {
            c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
            return
        }
        // Update user info without validation
        // ...
        c.JSON(http.StatusOK, gin.H{"status": "User updated"})
    })
    r.Run()
}

This Go code snippet represents a simple web server using the gin framework. The server has a single endpoint, /update, which accepts POST requests. The request body is expected to be a JSON object representing a User object, which has a single field, Name.

The vulnerability in this code lies in the lack of validation for the incoming data. When a POST request is made to the /update endpoint, the server blindly accepts the JSON payload and attempts to bind it to a User struct. If the JSON payload is malformed or if it contains fields that are not present in the User struct, the ShouldBindJSON method will return an error, and the server will respond with a 400 Bad Request status. However, if the JSON payload is well-formed and contains a Name field, the server will accept it without any further validation.

This means that an attacker could potentially send a POST request with a Name field that contains invalid data, such as a non-existing name. The server would accept this data and potentially use it to update a user's information, leading to data corruption or other unexpected behavior.

Steps​

  • Implement server-side validation to ensure the authenticity and integrity of the data being received.
  • Verify the user's permissions and authorization before allowing any modifications to the data.
  • Use a whitelist or allowlist approach to validate the data against a predefined set of acceptable values.
  • Implement input validation checks to ensure that the data being received is valid and meets the required criteria.
  • Sanitize the input data to prevent any potential injection attacks or malicious input.
  • Consider implementing a data validation framework or library to simplify the validation process.
  • Regularly update and maintain the validation logic to adapt to changing requirements and potential new vulnerabilities.

Compliant code​

package main

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

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

// List of valid names
var validNames = []string{"John", "Jane", "Bob", "Alice"}

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

        // Validate user name
        if !isValidName(user.Name) {
            c.JSON(http.StatusBadRequest, gin.H{"error": "Invalid user name"})
            return
        }

        // Check user permissions and update user info
        // ...

        c.JSON(http.StatusOK, gin.H{"status": "User updated"})
    })
    r.Run()
}

// Function to validate user name
func isValidName(name string) bool {
    for _, validName := range validNames {
        if name == validName {
            return true
        }
    }
    return false
}

The updated code now includes server-side validation to ensure the authenticity and integrity of the data being received.

The isValidName function is used to validate the user's name against a predefined list of valid names. This is an example of a whitelist or allowlist approach to data validation. If the user's name is not in the list of valid names, the server responds with a 400 Bad Request status and an error message.

Before updating the user's information, the server should also check the user's permissions and authorization. This part is not included in the code, as it depends on the specific authentication and authorization mechanism used by the application.

This approach helps to prevent unauthorized modifications to the data and ensures that the data being received is valid and meets the required criteria. It also helps to prevent potential injection attacks or malicious input.

Remember to regularly update and maintain the validation logic to adapt to changing requirements and potential new vulnerabilities. Consider implementing a data validation framework or library to simplify the validation process.

References​

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