Enforce email uniqueness verification during the registration process
package main
import (
"github.com/gin-gonic/gin"
)
type User struct {
Email string `json:"email" binding:"required"`
Password string `json:"password" binding:"required"`
}
func main() {
r := gin.Default()
r.POST("/register", func(c *gin.Context) {
var user User
if err := c.ShouldBindJSON(&user); err != nil {
c.JSON(400, gin.H{"error": err.Error()})
return
}
// TODO: Add email uniqueness verification here
c.JSON(200, gin.H{"message": "Registration successful"})
})
r.Run()
}
This is a simple Go application using the Gin framework. It has a POST
/register endpoint that accepts a JSON payload with
email and
password fields to create a new user.
The
User struct is used to bind the incoming JSON payload. It has two fields,
Email and
Password, both are required.
The problem with this code is that it does not properly verify the uniqueness of the email. It allows the plus character in the email registration process. An attacker could abuse this feature to create several accounts pointing to the same email. For example, an attacker could register with
attacker+1@gmail.com,
attacker+2@gmail.com,
attacker+3@gmail.com, etc., and all these emails will point to the same
attacker@gmail.com email address.
To fix this vulnerability, you need to add a function that checks the uniqueness of the email address before creating a new user. This function should remove any characters after the plus sign in the local part of the email address before checking for uniqueness.
package main
import (
"github.com/gin-gonic/gin"
"database/sql"
_ "github.com/go-sql-driver/mysql"
)
type User struct {
Email string `json:"email" binding:"required"`
Password string `json:"password" binding:"required"`
}
var db *sql.DB
func main() {
var err error
db, err = sql.Open("mysql", "user:password@/dbname")
if err != nil {
panic(err)
}
r := gin.Default()
r.POST("/register", func(c *gin.Context) {
var user User
if err := c.ShouldBindJSON(&user); err != nil {
c.JSON(400, gin.H{"error": err.Error()})
return
}
// Check if email already exists
var existingEmail string
err := db.QueryRow("SELECT email FROM users WHERE email = ?", user.Email).Scan(&existingEmail)
if err != nil && err != sql.ErrNoRows {
c.JSON(500, gin.H{"error": "Database error"})
return
}
if existingEmail != "" {
c.JSON(400, gin.H{"error": "Email already registered"})
return
}
// TODO: Add user registration code here
c.JSON(200, gin.H{"message": "Registration successful"})
})
r.Run()
}
The code above is a fixed version of the original vulnerable code. The vulnerability was that the system allowed the same email to be registered multiple times. This could be exploited by an attacker to create multiple accounts with the same email.
The fix involves adding a database query to check if the email already exists in the system before registering a new user. This is done using the
QueryRow function of the
sql package, which executes a query that is expected to return at most one row.
If the email already exists in the database, the
existingEmail variable will be assigned the existing email, and the system will return an error response indicating that the email is already registered. If the email does not exist in the database, the
existingEmail variable will remain an empty string, and the system will proceed with the user registration process.
Note that the database connection is established at the beginning of the
main function, and the
db variable is declared as a global variable so it can be accessed from the route handler function. The database connection string is a placeholder and should be replaced with your actual database connection string.
Also, the user registration code is not included in this example. You should replace the
TODO comment with your actual user registration code.