Prevention of unauthorized access to files and functionalities
package main
import (
"github.com/gin-gonic/gin"
"net/http"
)
func main() {
r := gin.Default()
r.PUT("/user/:name", func(c *gin.Context) {
name := c.Param("name")
userData := c.PostForm("data")
// Vulnerable part: no validation or sanitization of user input
err := updateUserData(name, userData)
if err != nil {
c.JSON(http.StatusInternalServerError, gin.H{"error": err.Error()})
return
}
c.JSON(http.StatusOK, gin.H{"status": "ok"})
})
r.Run() // listen and serve on 0.0.0.0:8080
}
func updateUserData(name string, data string) error {
// Update user data in Sharepoint
// This function is vulnerable as it directly uses user-provided data
return nil
}
The vulnerability lies in the
updateUserData function in the above code. This function takes two parameters:
name and
data. These parameters are directly obtained from the user input without any form of validation or sanitization, which makes the function susceptible to malicious input.
The
name parameter is obtained from the URL parameter
:name and the
data parameter is obtained from the form data
data. Both of these inputs are directly used in the
updateUserData function without any checks or sanitization, which can lead to unauthorized access to files and functionalities.
A malicious user can inject potentially dangerous characters into these parameters that can lead to inappropriate behavior in the application. For instance, they can manipulate the
data parameter to access and modify files in the Sharepoint without authorization.
To fix this vulnerability, the application should implement input validation and sanitization to ensure that the user-provided data does not contain any malicious characters or sequences. This can be done using regular expressions or by using a library that provides these functionalities. Moreover, the application should also implement proper access controls to ensure that a user can only access the files and functionalities that they are authorized to access.
package main
import (
"github.com/gin-gonic/gin"
"github.com/go-playground/validator/v10"
"net/http"
"regexp"
)
type UserInput struct {
Name string `validate:"required,alpha"`
Data string `validate:"required"`
}
var validate *validator.Validate
func main() {
r := gin.Default()
validate = validator.New()
r.PUT("/user/:name", func(c *gin.Context) {
name := c.Param("name")
userData := c.PostForm("data")
input := &UserInput{
Name: name,
Data: userData,
}
err := validate.Struct(input)
if err != nil {
c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
return
}
// Sanitize user input
sanitizedData := sanitizeData(userData)
err = updateUserData(name, sanitizedData)
if err != nil {
c.JSON(http.StatusInternalServerError, gin.H{"error": err.Error()})
return
}
c.JSON(http.StatusOK, gin.H{"status": "ok"})
})
r.Run() // listen and serve on 0.0.0.0:8080
}
func sanitizeData(data string) string {
// Use a simple regex to remove any non-alphanumeric characters
reg, _ := regexp.Compile("[^a-zA-Z0-9]+")
sanitizedData := reg.ReplaceAllString(data, "")
return sanitizedData
}
func updateUserData(name string, data string) error {
// Update user data in Sharepoint
// This function is now safe as it uses sanitized user-provided data
return nil
}
The updated code now includes input validation and sanitization to prevent injection of potentially dangerous characters.
The
UserInput struct is used to define the expected format of the user input. The
validate tags are used to specify the validation rules for each field. In this case, the
Name field is required and must only contain alphabetic characters, and the
Data field is required.
The
validate.Struct(input) function is used to validate the user input against the defined struct. If the validation fails, an error is returned and the function exits.
The
sanitizeData function is used to sanitize the user data. It uses a regular expression to remove any non-alphanumeric characters from the data. This is a simple example of sanitization, and more complex sanitization may be required depending on the specific requirements of your application.
The
updateUserData function now uses the sanitized user data, which prevents injection of potentially dangerous characters.
In addition to these changes, it's important to implement proper access control mechanisms, use authentication and authorization mechanisms, regularly update and patch the application and its dependencies, and perform security testing to ensure the security of your application.