TTLabs/EvaporateJS

// You need to import the following:
import (
    "crypto/hmac"
    "crypto/sha256"
    "fmt"
    "log"
    "net/http"
    "strings"
)

var (
    date        string
    regionName  string
    serviceName string
    requestName string
)

// this example is using Martini
m.Get("/sign_auth", func(w http.ResponseWriter, r *http.Request) {
    // Todo: Authenticate the request    log.Println("signing")
    qs := req.URL.Query()

    strs := strings.Split(qs.Get("to_sign"), "\n")
    data := strings.Split(strs[2], "/")
    date, regionName, serviceName, requestName = data[0], data[1], data[2], data[3]

    signedKey := signature(date, qs.Get("to_sign"))

    w.Write([]byte(signedKey))
}

func signature(t, sts string) string {
    h := HMAC(derivedKey(t), []byte(sts))
    return fmt.Sprintf("%x", h)
}

func derivedKey(t string) []byte {
    h := HMAC([]byte("AWS4"+"AWS_SECRET"), []byte(t))
    h = HMAC(h, []byte(regionName))
    h = HMAC(h, []byte(serviceName))
    h = HMAC(h, []byte(requestName))
    return h
}

func HMAC(key, data []byte) []byte {
    h := hmac.New(sha256.New, key)
    h.Write(data)
    return h.Sum(nil)
}