How to run GoLang Sample Code for MLE

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How to run GoLang Sample Code for MLE

In this “How-to” guide, we will show you how to test MLE (Message Level Encryption) enabled APIs using GoLang.

 

Important Links:

 

Enable MLE for the API(s) you are interested in.

 

Login to your Visa Developer Dashboard and go to your project, you should see something like this:

 

2020-11-11_09-45-12.png

 

Enable the APIs for which MLE needs to be active in VDP by toggling the API for which MLE needs to be enforced.

 

In this example, we will enable MLE for Funds Transfer API And Query API as below:

 

2020-11-11_09-46-41.png

 

 

How to get credentials

 

You can obtain your project credentials by browsing the left side navigation menu of your project and click on “Credentials”.

 

2020-11-11_11-25-10.png

 

Next step we will create a Key-ID by clicking on the Generate Key-ID button.

 

2020-11-11_11-29-02.png

 

After you have clicked the button, you will get Key-ID. Copy the Key-ID for your reference.

The Key-ID will look like this: 41d9f2a1-xxxx-4xxx-b40c-a0480c2xxxxx

 

2020-11-11_11-30-49.png

 

The next step is to add a CSR (Certificate Signing Request). Click on the link "Add CSR" .   

 

You will be prompt to submit a Certificate Signing Request. 

 

2020-11-11_11-32-46.png

 

We have option to Generate a CSR for me (default) or submit your own. In this example we will use the Generate a CSR for me (default) and Click Confirm button.

 

After submitting the request, you will be prompt to download the Certificate/Copy Private Key. 

 

2020-11-11_11-34-26.png

 

After you have downloaded the private key, check the box "I confirm that I've downloaded my certificate key" and click continue. You will see the Status change to "Active".

 

 

Expand the Key-ID and you will see the Server Encryption Certificate and Client Encryption Certificate.

Download both certificates and save it.

 

2020-11-11_11-36-33.png

To be able to make an API call with MLE, you need to have the following

  • Server Encryption Certificate
  • Key-ID
  • Certificate Private Key

 

How to run GoLang Sample Code for MLE

 

 

Step 1 - Create a new project on GoLand

 

  • Launch GoLand, on the GoLand Welcome Screen, click Create New Project

  • In the New Project wizard, select Go from the list on the left, provide the project Location, Go SDK and click Create.
  • Create a new Go file as Simple Application and named it “mle_oct

 

Step 2 - Copy the below sample code to the “mle_oct.go” file

 

  • Install all the required dependencies when prompt.
  • Set the below parameters:

 

username = "<YOUR USER ID>"
password = "<YOUR PASSWORD>"

 

clientCertificateFile = "<YOUR MUTUAL SSL CLIENT CERTIFICATE PATH>"
clientCertificateKeyFile = "<YOUR MUTUAL SSL PRIVATE KEY PATH>"
caCertificateFile = "<YOUR MUTUAL SSL CA PATH>"

 

mleClientPrivateKeyPath = "<YOUR MLE CLIENT PRIVATE KEY PATH>"
mleServerPublicCertificatePath = "<YOUR MLE SERVER CERTIFICATE PATH>"
keyId = "<YOUR KEY ID>"

 

 

/**
 * (c) Copyright 2018 - 2020 Visa. All Rights Reserved.**
 *
 * NOTICE: The software and accompanying information and documentation (together, the “Software”) remain the property of and are proprietary to Visa and its suppliers and affiliates. The Software remains protected by intellectual property rights and may be covered by U.S. and foreign patents or patent applications. The Software is licensed and not sold.*
 *
 *  By accessing the Software you are agreeing to Visa's terms of use (developer.visa.com/terms) and privacy policy (developer.visa.com/privacy).In addition, all permissible uses of the Software must be in support of Visa products, programs and services provided through the Visa Developer Program (VDP) platform only (developer.visa.com). **THE SOFTWARE AND ANY ASSOCIATED INFORMATION OR DOCUMENTATION IS PROVIDED ON AN “AS IS,” “AS AVAILABLE,” “WITH ALL FAULTS” BASIS WITHOUT WARRANTY OR  CONDITION OF ANY KIND. YOUR USE IS AT YOUR OWN RISK.** All brand names are the property of their respective owners, used for identification purposes only, and do not imply product endorsement or affiliation with Visa. Any links to third party sites are for your information only and equally  do not constitute a Visa endorsement. Visa has no insight into and control over third party content and code and disclaims all liability for any such components, including continued availability and functionality. Benefits depend on implementation details and business factors and coding steps shown are exemplary only and do not reflect all necessary elements for the described capabilities. Capabilities and features are subject to Visa’s terms and conditions and may require development,implementation and resources by you based on your business and operational details. Please refer to the specific API documentation for details on the requirements, eligibility and geographic availability.*
 *
 * This Software includes programs, concepts and details under continuing development by Visa. Any Visa features,functionality, implementation, branding, and schedules may be amended, updated or canceled at Visa’s discretion.The timing of widespread availability of programs and functionality is also subject to a number of factors outside Visa’s control,including but not limited to deployment of necessary infrastructure by issuers, acquirers, merchants and mobile device manufacturers.*
 *
 */

package main

import (
   "bytes"
   "crypto/rsa"
   "crypto/tls"
   "crypto/x509"
   "encoding/json"
   "encoding/pem"
   "errors"
   "fmt"
   "gopkg.in/square/go-jose.v2"
   "io/ioutil"
   "log"
   "net/http"
   "time"
)

var (
   baseUrl = "https://sandbox.api.visa.com"

   // THIS IS EXAMPLE ONLY how will user_id and password look like
   // userId = "1WM2TT4IHPXC8DQ5I3CH21n1rEBGK-Eyv_oLdzE2VZpDqRn_U";
   // password = "19JRVdej9";
   username = "<YOUR USER ID>"
   password = "<YOUR PASSWORD>"

   // THIS IS EXAMPLE ONLY how will cert and key look like
   // clientCertificateFile = 'cert.pem'
   // clientCertificateKeyFile = 'key_83d11ea6-a22d-4e52-b310-e0558816727d.pem'
   // caCertificateFile = 'ca_bundle.pem'

   clientCertificateFile    = "<YOUR MUTUAL SSL CLIENT CERTIFICATE PATH>"
   clientCertificateKeyFile = "<YOUR MUTUAL SSL PRIVATE KEY PATH>"
   caCertificateFile        = "<YOUR MUTUAL SSL CA PATH>"

   // MLE KEY
   //#########
   //# THIS IS EXAMPLE ONLY how will myKey_ID, server_cert and private_key look like
   //# mleClientPrivateKeyPath = 'key_7f591161-6b5f-4136-80b8-2ae8a44ad9eb.pem'
   //# mleServerPublicCertificatePath = 'server_cert_7f591161-6b5f-4136-80b8-2ae8a44ad9eb.pem'
   //# keyId = '7f591161-6b5f-4136-80b8-2ae8a44ad9eb'

   mleClientPrivateKeyPath        = "<YOUR MLE CLIENT PRIVATE KEY PATH>"
   mleServerPublicCertificatePath = "<YOUR MLE SERVER CERTIFICATE PATH>"
   keyId                          = "<YOUR KEY ID>"
)

func main() {

   log.Println("####################################################################################")
   log.Println("######################## START PUSH (OCT)  Transaction #############################")
   log.Println("####################################################################################")

   pushFundEndPoint := "/visadirect/fundstransfer/v1/pushfundstransactions"
   acquiringBin := "408999"

   t := time.Now()
   localTransactionDateTime := fmt.Sprintf("%d-%02d-%02dT%02d:%02d:%02d",
      t.Year(), t.Month(), t.Day(),
      t.Hour(), t.Minute(), t.Second())

   octPayload := `{
     "acquirerCountryCode": "840",
      "acquiringBin": "` + acquiringBin + `",
     "amount": "124.05",
     "businessApplicationId": "AA",
     "cardAcceptor": {
      "address": {
        "country": "USA",
        "county": "SanMateo",
        "state": "CA",
        "zipCode": "94404"
      },
      "idCode": "CA-IDCode-77765",
      "name": "VisaInc.USA-FosterCity",
      "terminalId": "TID-9999"
     },
     "localTransactionDateTime": "` + localTransactionDateTime + `",
     "merchantCategoryCode": "6012",
     "pointOfServiceData": {
      "motoECIIndicator": "0",
      "panEntryMode": "90",
      "posConditionCode": "00"
     },
     "recipientName": "rohan",
     "recipientPrimaryAccountNumber": "4957030420210496",
     "retrievalReferenceNumber": "412770451018",
     "senderAccountNumber": "4653459515756154",
     "senderAddress": "901MetroCenterBlvd",
     "senderCity": "FosterCity",
     "senderCountryCode": "124",
     "senderName": "MohammedQasim",
     "senderReference": "",
     "senderStateCode": "CA",
     "sourceOfFundsCode": "05",
     "systemsTraceAuditNumber": "451018",
     "transactionCurrencyCode": "USD",
     "settlementServiceIndicator": "9",
     "colombiaNationalServiceData": {
      "countryCodeNationalService": "170",
      "nationalReimbursementFee": "20.00",
      "nationalNetMiscAmountType": "A",
      "nationalNetReimbursementFeeBaseAmount": "20.00",
      "nationalNetMiscAmount": "10.00",
      "addValueTaxReturn": "10.00",
      "taxAmountConsumption": "10.00",
      "addValueTaxAmount": "10.00",
      "costTransactionIndicator": "0",
      "emvTransactionIndicator": "1",
      "nationalChargebackReason": "11"
     }
   }`

   encData := map[string]string{"encData": createJWE(octPayload, keyId, mleServerPublicCertificatePath)}
   encryptedPayload, _ := json.Marshal(encData)
   responsePayload := invokeAPI(pushFundEndPoint, http.MethodPost, string(encryptedPayload))
   log.Println("OCT Response Data: ", responsePayload)

   log.Println("####################################################################################")
   log.Println("######################## END PUSH (OCT)  Transaction ###############################")
   log.Println("####################################################################################")

   log.Println("####################################################################################")
   log.Println("######################## START QUERY API ###########################################")
   log.Println("####################################################################################")

   var responseMap map[string]json.RawMessage
   _ = json.Unmarshal([]byte(responsePayload), &responseMap)

   queryString := "?acquiringBIN=" + acquiringBin + "&transactionIdentifier=" + string(responseMap["transactionIdentifier"])
   transactionQueryEndPoint := "/visadirect/v1/transactionquery" + queryString

   responsePayload = invokeAPI(transactionQueryEndPoint, http.MethodGet, "")
   log.Println("Query Response Data: ", responsePayload)

   log.Println("####################################################################################")
   log.Println("######################## END QUERY API #############################################")
   log.Println("####################################################################################")

}

func invokeAPI(resourcePath string, httpMethod string, payload string) string {
   //Load CA Cert
   clientCACert, err := ioutil.ReadFile(caCertificateFile)
   if err != nil {
      panic(err)
   }

   //Load Client Key Pair
   clientKeyPair, err := tls.LoadX509KeyPair(clientCertificateFile, clientCertificateKeyFile)

   clientCertPool, _ := x509.SystemCertPool()
   if clientCertPool == nil {
      clientCertPool = x509.NewCertPool()
   }

   clientCertPool.AppendCertsFromPEM(clientCACert)

   tlsConfig := &tls.Config{
      Certificates: []tls.Certificate{clientKeyPair},
      RootCAs:      clientCertPool,
   }

   transport := &http.Transport{
      TLSClientConfig: tlsConfig,
   }

   client := &http.Client{Transport: transport}

   apiUrl := baseUrl + resourcePath
   var request *http.Request = nil
   if payload != "" {
      log.Println("Request Payload: ", payload)
      request, err = http.NewRequest(httpMethod, apiUrl, bytes.NewBuffer([]byte(payload)))
   } else {
      request, err = http.NewRequest(httpMethod, apiUrl, nil)
   }

   if err != nil {
      panic(err)
   }
   request.SetBasicAuth(username, password)
   request.Header.Set("keyId", keyId)
   request.Header.Set("Accept", "application/json")
   request.Header.Set("Content-Type", "application/json")

   log.Println("Invoking API:", httpMethod, resourcePath)
   resp, err := client.Do(request)

   if err != nil {
      panic(err)
   }

   defer resp.Body.Close()
   body, err := ioutil.ReadAll(resp.Body)
   if err != nil {
      panic(err)
   }
   log.Println("Http Status :", resp.Status)
   log.Println("Response Headers:", resp.Header)

   encryptedResponsePayload := string(body)
   log.Println("Response Payload: ", encryptedResponsePayload)

   if !(resp.StatusCode >= 200 && resp.StatusCode <= 299) {
      decryptedData := decryptJWE(encryptedResponsePayload, mleClientPrivateKeyPath)
      panic(errors.New("error when invoking visa api. " + decryptedData))
   }

   log.Println("Response Body:", encryptedResponsePayload)
   decryptedData := decryptJWE(encryptedResponsePayload, mleClientPrivateKeyPath)
   return decryptedData
}

func createJWE(payload string, keyId string, mleServerPublicCertificatePath string) string {
   // Instantiate an encrypter using RSA-OAEP-256 with AES128-GCM. An error would
   // indicate that the selected algorithm(s) are not currently supported.
   publicKey := loadPublicKey(mleServerPublicCertificatePath)
   opts := new(jose.EncrypterOptions)

   iat := currentMillis()

   opts.WithHeader("kid", keyId)
   opts.WithHeader("iat", iat)
   encrypter, err := jose.NewEncrypter(jose.A128GCM, jose.Recipient{Algorithm: jose.RSA_OAEP_256, Key: publicKey}, opts)
   if err != nil {
      panic(err)
   }

   // Encrypt a sample plaintext. Calling the encrypter returns an encrypted
   // JWE object, which can then be serialized for output afterwards. An error
   // would indicate a problem in an underlying cryptographic primitive.
   object, err := encrypter.Encrypt([]byte(payload))
   if err != nil {
      panic(err)
   }

   // Serialize the encrypted object using the compact serialization format.
   serialized, err := object.CompactSerialize()
   if err != nil {
      panic(err)
   }
   return serialized
}

func currentMillis() int64 {
   return time.Now().UnixNano() / int64(time.Millisecond)
}

func loadPublicKey(certFilePath string) *rsa.PublicKey {
   certificate, err := ioutil.ReadFile(certFilePath)
   if err != nil {
      panic(err)
   }
   block, _ := pem.Decode(certificate)
   var cert *x509.Certificate
   cert, _ = x509.ParseCertificate(block.Bytes)
   return cert.PublicKey.(*rsa.PublicKey)
}

func parseEncryptedResponse(encryptedPayload string) EncryptedResponse {
   var encryptedResponse EncryptedResponse
   err := json.Unmarshal([]byte(encryptedPayload), &encryptedResponse)

   if err != nil {
      panic(err)
   }
   return encryptedResponse
}

func decryptJWE(encryptedPayload string, mleClientPrivateKeyPath string) string {

   encryptedData := parseEncryptedResponse(encryptedPayload)

   // Parse the serialized, encrypted JWE object. An error would indicate that
   // the given input did not represent a valid message.
   object, err := jose.ParseEncrypted(encryptedData.EncData)
   if err != nil {
      panic(err)
   }

   // Now we can decrypt and get back our original plaintext. An error here
   // would indicate the the message failed to decrypt, e.g. because the auth
   // tag was broken or the message was tampered with.
   privateKey := loadPrivateKey(mleClientPrivateKeyPath)
   decrypted, err := object.Decrypt(privateKey)
   if err != nil {
      panic(err)
   }

   return string(decrypted)
}

//Load Private Key from file
func loadPrivateKey(keyFilePath string) *rsa.PrivateKey {
   keyPem, err := ioutil.ReadFile(keyFilePath)
   if err != nil {
      panic(err)
   }

   block, _ := pem.Decode(keyPem)
   priv, err := x509.ParsePKCS1PrivateKey(block.Bytes)
   if err != nil {
      panic(err)
   }
   return priv
}

type EncryptedResponse struct {
   EncData string
}

 

 

Step 4 - Compile Your Code 

 

  • Simply right click and run “go build mle_oct….”

 

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