Fix Mass Assignment in Echo
Mass Assignment (Overposting) in Echo is a critical vulnerability where an attacker manipulates the request payload to overwrite sensitive fields in your database models. By binding the request body directly to a struct that represents a database entity, you grant the user control over every field mapped in that struct, including internal flags like 'is_admin' or 'balance'.
The Vulnerable Pattern
type User struct { ID uint `json:"id"` Username string `json:"username"` IsAdmin bool `json:"is_admin"` }
func UpdateProfile(c echo.Context) error { u := new(User) // VULNERABLE: Directly binding request to the DB model. // An attacker sends {“is_admin”: true} to escalate privileges. if err := c.Bind(u); err != nil { return err } return db.Save(u).Error }
The Secure Implementation
The vulnerability stems from the blind trust of user input via Echo's c.Bind(). To fix this, you must decouple your API contract from your database schema. Use a Data Transfer Object (DTO) struct that only contains fields a user is permitted to modify. This creates an implicit allow-list. By binding to the DTO and then manually mapping those values to your model, you ensure that internal fields like 'IsAdmin' or 'ID' remain immutable through the API.
type UpdateUserDTO struct { Username string `json:"username"` Email string `json:"email"` // Sensitive fields like IsAdmin are omitted here }func UpdateProfile(c echo.Context) error { dto := new(UpdateUserDTO) if err := c.Bind(dto); err != nil { return err }
var user User id := c.Param("id") if err := db.First(&user, id).Error; err != nil { return err } // SECURE: Explicitly map only the allowed fields from the DTO user.Username = dto.Username user.Email = dto.Email return db.Save(&user).Error
}
Your Echo API
might be exposed to Mass Assignment
74% of Echo apps fail this check. Hackers use automated scanners to find this specific flaw. Check your codebase before they do.
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