Need

Enforce proper type assignment in the source code

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 net/http for building HTTP servers in a Node.js application

Description

Non compliant code

        package main

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

func main() {
	r := gin.Default()
	r.GET("/example", func(c *gin.Context) {
		var data = c.MustGet("data")
		c.JSON(http.StatusOK, gin.H{
			"data": data,
		})
	})
	r.Run()
}
        
        

In the above code, the variable data is declared without a specific type. This is done using the var keyword followed by the variable name data and then assigning the value using the = operator. The value is retrieved from the context c of the gin framework using the MustGet function with the key "data".

This is a vulnerability because the data type of data is not explicitly defined, and it will be inferred from the value returned by c.MustGet("data"). This can lead to unexpected behavior if the value associated with the key "data" in the context c is not of the type that the rest of the code expects.

For example, if the rest of the code expects data to be a string and tries to perform string operations on it, but the value associated with the key "data" in the context c is actually an integer, a runtime error will occur.

Moreover, this code is inefficient because every time data is used, the Go runtime has to determine its data type dynamically. This can slow down the execution of the program, especially if data is used frequently.

Steps

• Identify the specific type of data that is being stored in the 'data' variable
• Declare the 'data' variable with the appropriate type
• Assign the value from 'c.MustGet('data')' to the 'data' variable with the correct type
• Update the JSON response to use the 'data' variable with the correct type

Compliant code

        package main

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

func main() {
	r := gin.Default()
	r.GET("/example", func(c *gin.Context) {
		data, exists := c.Get("data")
		if !exists {
			c.JSON(http.StatusBadRequest, gin.H{"error": "No data provided"})
			return
		}
		strData, ok := data.(string) // assuming the data is of type string
		if !ok {
			c.JSON(http.StatusBadRequest, gin.H{"error": "Invalid data type"})
			return
		}
		c.JSON(http.StatusOK, gin.H{
			"data": strData,
		})
	})
	r.Run()
}
        
        

The original code had a vulnerability due to improper type assignation. The variable data was declared without a specific type, which can be inefficient and potentially unsafe.

The fixed code first checks if the data exists in the context using c.Get("data"). If it doesn't exist, it returns a 400 Bad Request status with an error message.

Next, it tries to assert the type of data to string (assuming the data is expected to be a string). If the type assertion fails (i.e., the data is not a string), it returns a 400 Bad Request status with an error message.

Finally, if the data exists and is of the correct type, it returns a 200 OK status with the data.

This way, the code is safer and more efficient because it doesn't need to identify and cast the variable's data type every time it's used.

References

• 113. Improper type assignation