Fix Improper Error Handling in Go Fiber
Leaking stack traces, file paths, or database schemas via raw error messages is a classic reconnaissance gift to attackers. In Go Fiber, failing to implement a centralized error handler often results in developers returning 'err.Error()' directly to the client. This guide demonstrates how to intercept and sanitize these leaks to ensure internal system details stay internal.
The Vulnerable Pattern
app.Get("/api/data", func(c *fiber.Ctx) error {
data, err := db.QueryInternalData()
if err != nil {
// VULNERABLE: Directly returning the raw error string to the client
// This could leak SQL syntax, connection strings, or table names.
return c.Status(500).SendString(err.Error())
}
return c.JSON(data)
})The Secure Implementation
The vulnerable code pattern uses 'c.SendString(err.Error())', which pipes raw backend failures directly to the HTTP response body. This allows an attacker to trigger edge cases and map your infrastructure based on verbose error messages. The secure implementation leverages Fiber's 'Config.ErrorHandler' to create a bottleneck. This handler catches every error returned from routes, logs the sensitive details to a secure log stream, and returns a sanitized, structured JSON response to the client. By using 'fiber.NewError()', you can control the specific message sent to the client without ever exposing the underlying system state.
func main() { app := fiber.New(fiber.Config{ // SECURE: Centralized Error Handler ErrorHandler: func(c *fiber.Ctx, err error) error { code := fiber.StatusInternalServerError message := "An unexpected error occurred"if e, ok := err.(*fiber.Error); ok { code = e.Code message = e.Message } // Log the actual error internally for debugging log.Printf("[ERROR] %d: %v", code, err) // Return a sanitized, generic message to the user return c.Status(code).JSON(fiber.Map{ "status": "error", "message": message, }) }, }) app.Get("/api/data", func(c *fiber.Ctx) error { data, err := db.QueryInternalData() if err != nil { // Return a generic Fiber error; the handler takes care of the rest return fiber.NewError(fiber.StatusInternalServerError, "Data retrieval failed") } return c.JSON(data) })
}
Your Go Fiber API
might be exposed to Improper Error Handling
74% of Go Fiber apps fail this check. Hackers use automated scanners to find this specific flaw. Check your codebase before they do.
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