Fix BFLA (Broken Function Level Authorization) in Go Fiber

BFLA (Broken Function Level Authorization) is the classic 'oops, I forgot to check roles' vulnerability. In Go Fiber, developers often assume that because a user is authenticated (JWT is valid), they are authorized to hit any endpoint. Attackers exploit this by guessing administrative endpoints or manipulating HTTP methods to perform actions they shouldn't, like deleting users or changing system configs. If you aren't verifying 'User.Role == Admin' on sensitive routes, you're pwned.

The Vulnerable Pattern

app.Delete("/api/v1/users/:id", func(c *fiber.Ctx) error {
    // VULNERABILITY: This endpoint verifies the user is logged in via global JWT middleware,
    // but it never checks if the user has the 'admin' role. 
    // Any low-privilege user can delete any other user account.
    userId := c.Params("id")
    db.DeleteUser(userId)
    return c.Status(200).JSON(fiber.Map{"status": "deleted"})
})

The Secure Implementation

Fixing BFLA requires a shift from 'Authentication' (who are you?) to 'Authorization' (what can you do?). In the secure snippet, we implement a closure-based middleware `RequireRole`. This middleware extracts the user's role from the context (populated by your JWT/Session handler) and compares it against the required permission before the handler is even reached. Always default to 'Deny All' and explicitly whitelist roles for sensitive HTTP verbs (POST, PUT, DELETE). For complex systems, consider Casbin or OPA for more granular RBAC/ABAC logic.

func RequireRole(role string) fiber.Handler {
    return func(c *fiber.Ctx) error {
        user := c.Locals("user").(*UserClaims)
        if user.Role != role {
            return c.Status(fiber.StatusForbidden).JSON(fiber.Map{"error": "Access Denied: Insufficient Permissions"})
        }
        return c.Next()
    }
}
// SECURE: Implementing a middleware layer specifically for authorization
app.Delete(“/api/v1/users/:id”, RequireRole(“admin”), func(c *fiber.Ctx) error {
userId := c.Params(“id”)
db.DeleteUser(userId)
return c.Status(200).JSON(fiber.Map{“status”: “deleted”})
})