EarlyData

The Early Data middleware for Fiber adds support for TLS 1.3's early data ("0-RTT") feature. Citing RFC 8446, when a client and server share a PSK, TLS 1.3 allows clients to send data on the first flight ("early data") to speed up the request, effectively reducing the regular 1-RTT request to a 0-RTT request.

Make sure to enable fiber's TrustProxy config option before using this middleware in order to not trust bogus HTTP request headers of the client.

Also be aware that enabling support for early data in your reverse proxy (e.g. nginx, as done with a simple ssl_early_data on;) makes requests replayable. Refer to the following documents before continuing:

• datatracker
• trailofbits

By default, this middleware allows early data requests on safe HTTP request methods only and rejects the request otherwise, i.e. aborts the request before executing your handler. This behavior can be controlled by the AllowEarlyData config option. Safe HTTP methods — GET, HEAD, OPTIONS and TRACE — should not modify a state on the server.

Signatures

func New(config ...Config) fiber.Handler
func IsEarlyData(c fiber.Ctx) bool

Examples

Import the middleware package that is part of the Fiber web framework

import (
    "github.com/gofiber/fiber/v3"
    "github.com/gofiber/fiber/v3/middleware/earlydata"
)

After you initiate your Fiber app, you can use the following possibilities:

// Initialize default config
app.Use(earlydata.New())

// Or extend your config for customization
app.Use(earlydata.New(earlydata.Config{
    Error: fiber.ErrTooEarly,
    // ...
}))

Config

Property	Type	Description	Default
Next	func(fiber.Ctx) bool	Next defines a function to skip this middleware when returned true.	nil
IsEarlyData	func(fiber.Ctx) bool	IsEarlyData returns whether the request is an early-data request.	Function checking if "Early-Data" header equals "1"
AllowEarlyData	func(fiber.Ctx) bool	AllowEarlyData returns whether the early-data request should be allowed or rejected.	Function rejecting on unsafe and allowing safe methods
Error	error	Error is returned in case an early-data request is rejected.	fiber.ErrTooEarly

Default Config

var ConfigDefault = Config{
    IsEarlyData: func(c fiber.Ctx) bool {
        return c.Get(DefaultHeaderName) == DefaultHeaderTrueValue
    },
    AllowEarlyData: func(c fiber.Ctx) bool {
        return fiber.IsMethodSafe(c.Method())
    },
    Error: fiber.ErrTooEarly,
}

Constants

const (
    DefaultHeaderName      = "Early-Data"
    DefaultHeaderTrueValue = "1"
)