HMAC is not what it should be

[MiesSuomesta]

Describe the bug

The bug is that the SHA provided is not got when running the example?

Steps to Reproduce Run following code:

package main
import( 
"crypto/hmac"
"crypto/sha256"
"encoding/hex"
"sort"
"fmt"
)

var PaytrailOfficialRequestSignature = "3708f6497ae7cc55a2e6009fc90aa10c3ad0ef125260ee91b19168750f6d74f6"

func headersToBytesSorted(headers map[string]string) (sortedHeaders []byte) {
    var keys []string
    for key := range headers {
            if key[:9] == "checkout-" {
                keys = append(keys, key)
            }
    }
    sort.Strings(keys)
    for _, key := range keys {
                    sortedHeaders = append(sortedHeaders, []byte(key+":"+headers[key]+"\n")...)
    }
    return sortedHeaders
}

func CalculateHmac(secret, body []byte, headers map[string]string) string {

    payload := headersToBytesSorted(headers)
    payload = append(payload, body...)
    hash := hmac.New(sha256.New, secret)
    hash.Write(payload)
    return hex.EncodeToString(hash.Sum(nil))
}

var PaytrailOfficialRequestHeaders = map[string]string{
    "checkout-account":   "375917",
    "checkout-algorithm": "sha256",
    "checkout-method":    "POST",
    "checkout-nonce":     "564635208570151",
    "checkout-timestamp": "2018-07-06T10:01:31.904Z",
}

var PaytrailOfficialRequestBody = []byte(`{
    "stamp": "unique-identifier-for-merchant",
    "reference": "3759170",
    "amount": 1525,
    "currency": "EUR",
    "language": "FI",
    "items": [
      {
        "unitPrice": 1525,
        "units": 1,
        "vatPercentage": 24,
        "productCode": "#1234",
        "deliveryDate": "2018-09-01"
      }
    ],
    "customer": {
      "email": ["test.customer@example.com"]
    },
    "redirectUrls": {
      "success": ["https://ecom.example.com/cart/success"],
      "cancel": ["https://ecom.example.com/cart/cancel"]
    }
  }`)

func main() {
    signatureStrOut := CalculateHmac([]byte("SAIPPUAKAUPPIAS"),  PaytrailOfficialRequestBody, PaytrailOfficialRequestHeaders)
    fmt.Println("Const :", PaytrailOfficialRequestSignature)
    fmt.Println("Got   :", signatureStrOut)
}

Expected behaviour

Output should be the hash from the example:: 3708f6497ae7cc55a2e6009fc90aa10c3ad0ef125260ee91b19168750f6d74f6 but what I got was : c7340510147ab5fe988fcf27f755b374f370aba2c612484f0fe3878936f961d6

Actual behaviour

Somehow it calculates wrong...

[MiesSuomesta]

hmm the formatting mailto and links are not in my code then :D EDIT: haa i got it nice :)

[MiesSuomesta]

Now i got it runnning :D sorry for trouble :D

[MiesSuomesta]

The problem was to use compact & buffer :D Thanks!

Working code:

package main
import( 
"bytes"
"crypto/hmac"
"crypto/sha256"
"encoding/hex"
"encoding/json"
"sort"
"fmt"
)

var PaytrailOfficialRequestSignature = "3708f6497ae7cc55a2e6009fc90aa10c3ad0ef125260ee91b19168750f6d74f6"

func headersToBytesSorted(headers map[string]string) (sortedHeaders []byte) {
    var keys []string
    for key := range headers {
        if key[:9] == "checkout-" {
            keys = append(keys, key)
        }
    }
    sort.Strings(keys)
    for _, key := range keys {
                    sortedHeaders = append(sortedHeaders, []byte(key+":"+headers[key]+"\n")...)
    }
    return sortedHeaders
}

func CalculateHmac(secret, body []byte, headers map[string]string) string {

    payload := headersToBytesSorted(headers)
    payload = append(payload, body...)
    hash := hmac.New(sha256.New, secret)
    hash.Write(payload)
    return hex.EncodeToString(hash.Sum(nil))
}

var PaytrailOfficialRequestHeaders = map[string]string{
    "checkout-account":   "375917",
    "checkout-algorithm": "sha256",
    "checkout-method":    "POST",
    "checkout-nonce":     "564635208570151",
    "checkout-timestamp": "2018-07-06T10:01:31.904Z",
}

var PaytrailOfficialRequestBody = []byte(`{
    "stamp": "unique-identifier-for-merchant",
    "reference": "3759170",
    "amount": 1525,
    "currency": "EUR",
    "language": "FI",
    "items": [
      {
        "unitPrice": 1525,
        "units": 1,
        "vatPercentage": 24,
        "productCode": "#1234",
        "deliveryDate": "2018-09-01"
      }
    ],
    "customer": {
      "email": "test.customer@example.com"
    },
    "redirectUrls": {
      "success": "https://ecom.example.com/cart/success",
      "cancel": "https://ecom.example.com/cart/cancel"
    }
  }`)

func main() {
    buf := new(bytes.Buffer)
    json.Compact(buf, PaytrailOfficialRequestBody)
    signatureStrOut := CalculateHmac([]byte("SAIPPUAKAUPPIAS"),  buf.Bytes(), PaytrailOfficialRequestHeaders)
    fmt.Println("Const :", PaytrailOfficialRequestSignature)
    fmt.Println("Got   :", signatureStrOut)
}