(VB.NET) ING Open Banking OAuth2 Client Credentials

Demonstrates how to get an access token for the ING Open Banking APIs using client credentials.

For more information, see https://developer.ing.com/openbanking/get-started/openbanking

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' This example requires the Chilkat API to have been previously unlocked.
' See Global Unlock Sample for sample code.


Dim cert As New Chilkat.Cert
Dim success As Boolean = cert.LoadFromFile("qa_data/certs_and_keys/ING/example_client_tls.cer")
If (success = False) Then
    Debug.WriteLine(cert.LastErrorText)
    Exit Sub
End If


Dim bdPrivKey As New Chilkat.BinData
success = bdPrivKey.LoadFile("qa_data/certs_and_keys/ING/example_client_tls.key")
If (success = False) Then
    Debug.WriteLine("Failed to load example_client_tls.key")
    Exit Sub
End If


' The OAuth 2.0 client_id for these certificates is e77d776b-90af-4684-bebc-521e5b2614dd. 
' Please note down this client_id since you will need it in the next steps to call the API.

Dim privKey As New Chilkat.PrivateKey
success = privKey.LoadAnyFormat(bdPrivKey,"")
If (success = False) Then
    Debug.WriteLine(privKey.LastErrorText)
    Exit Sub
End If


' Associate the private key with the certificate.
success = cert.SetPrivateKey(privKey)
If (success = False) Then
    Debug.WriteLine(cert.LastErrorText)
    Exit Sub
End If


Dim http As New Chilkat.Http

success = http.SetSslClientCert(cert)
If (success = False) Then
    Debug.WriteLine(http.LastErrorText)
    Exit Sub
End If



' Calculate the Digest and add the "Digest" header.  Do the equivalent of this:
' payload="grant_type=client_credentials"
' payloadDigest=`echo -n "$payload" | openssl dgst -binary -sha256 | openssl base64`
' digest=SHA-256=$payloadDigest
Dim crypt As New Chilkat.Crypt2
crypt.HashAlgorithm = "SHA256"
crypt.EncodingMode = "base64"
Dim payload As String = "grant_type=client_credentials"
Dim payloadDigest As String = crypt.HashStringENC(payload)

' Calculate the current date/time and add the Date header.  
' reqDate=$(LC_TIME=en_US.UTF-8 date -u "+%a, %d %b %Y %H:%M:%S GMT")  
Dim dt As New Chilkat.CkDateTime
dt.SetFromCurrentSystemTime()
' The desire date/time format is the "RFC822" format.
http.SetRequestHeader("Date",dt.GetAsRfc822(False))


' Calculate signature for signing your request
' Duplicate the following code:

' 	httpMethod="post"
' 	reqPath="/oauth2/token"
' 	signingString="(request-target): $httpMethod $reqPath
' 	date: $reqDate
' 	digest: $digest"
' 	signature=`printf "$signingString" | openssl dgst -sha256 -sign "${certPath}example_client_signing.key" -passin "pass:changeit" | openssl base64 -A`

Dim httpMethod As String = "POST"
Dim reqPath As String = "/oauth2/token"

Dim sbStringToSign As New Chilkat.StringBuilder
sbStringToSign.Append("(request-target): ")
sbStringToSign.Append(httpMethod)
sbStringToSign.ToLowercase()
sbStringToSign.Append(" ")
sbStringToSign.AppendLine(reqPath,False)

sbStringToSign.Append("date: ")
sbStringToSign.AppendLine(dt.GetAsRfc822(False),False)

sbStringToSign.Append("digest: SHA-256=")
sbStringToSign.Append(payloadDigest)

Dim signingPrivKey As New Chilkat.PrivateKey
success = signingPrivKey.LoadPemFile("qa_data/certs_and_keys/ING/example_client_signing.key")
If (success = False) Then
    Debug.WriteLine(signingPrivKey.LastErrorText)
    Exit Sub
End If


Dim rsa As New Chilkat.Rsa
success = rsa.ImportPrivateKeyObj(signingPrivKey)
If (success = False) Then
    Debug.WriteLine(rsa.LastErrorText)
    Exit Sub
End If


rsa.EncodingMode = "base64"
Dim b64Signature As String = rsa.SignStringENC(sbStringToSign.GetAsString(),"SHA256")

Dim sbAuthHdrVal As New Chilkat.StringBuilder
sbAuthHdrVal.Append("Signature keyId=""e77d776b-90af-4684-bebc-521e5b2614dd"",")
sbAuthHdrVal.Append("algorithm=""rsa-sha256"",")
sbAuthHdrVal.Append("headers=""(request-target) date digest"",")
sbAuthHdrVal.Append("signature=""")
sbAuthHdrVal.Append(b64Signature)
sbAuthHdrVal.Append("""")

Dim sbDigestHdrVal As New Chilkat.StringBuilder
sbDigestHdrVal.Append("SHA-256=")
sbDigestHdrVal.Append(payloadDigest)

' Do the following CURL statement:

' 	curl -i -X POST "${httpHost}${reqPath}" \
' 	-H 'Accept: application/json' \
' 	-H 'Content-Type: application/x-www-form-urlencoded' \
' 	-H "Digest: ${digest}" \
' 	-H "Date: ${reqDate}" \
' 	-H "authorization: Signature keyId=\"$keyId\",algorithm=\"rsa-sha256\",headers=\"(request-target) date digest\",signature=\"$signature\"" \
' 	-d "${payload}" \
' 	--cert "${certPath}tlsCert.crt" \
' 	--key "${certPath}tlsCert.key"

Dim req As New Chilkat.HttpRequest
req.AddParam("grant_type","client_credentials")
req.AddHeader("Accept","application/json")
req.AddHeader("Date",dt.GetAsRfc822(False))
req.AddHeader("Digest",sbDigestHdrVal.GetAsString())
req.AddHeader("Authorization",sbAuthHdrVal.GetAsString())
Dim resp As Chilkat.HttpResponse = http.PostUrlEncoded("https://api.sandbox.ing.com/oauth2/token",req)
If (http.LastMethodSuccess = False) Then
    Debug.WriteLine(http.LastErrorText)
    Exit Sub
End If


' If successful, the status code = 200
Debug.WriteLine("Response Status Code: " & resp.StatusCode)
Debug.WriteLine(resp.BodyStr)

Dim json As New Chilkat.JsonObject
json.Load(resp.BodyStr)



json.EmitCompact = False
Debug.WriteLine(json.Emit())

' A successful response contains an access token such as:
' {
'   "access_token": "eyJhbGc ... bxI_SoPOBH9xmoM",
'   "expires_in": 905,
'   "scope": "payment-requests:view payment-requests:create payment-requests:close greetings:view virtual-ledger-accounts:fund-reservation:create virtual-ledger-accounts:fund-reservation:delete virtual-ledger-accounts:balance:view",
'   "token_type": "Bearer",
'   "keys": [
'     {
'       "kty": "RSA",
'       "n": "3l3rdz4...04VPkdV",
'       "e": "AQAB",
'       "use": "sig",
'       "alg": "RS256",
'       "x5t": "3c396700fc8cd709cf9cb5452a22bcde76985851"
'     }
'   ],
'   "client_id": "e77d776b-90af-4684-bebc-521e5b2614dd"
' }

' Use this online tool to generate parsing code from sample JSON: 
' Generate Parsing Code from JSON

Dim kty As String
Dim n As String
Dim e As String
Dim use As String
Dim alg As String
Dim x5t As String

Dim access_token As String = json.StringOf("access_token")
Dim expires_in As Integer = json.IntOf("expires_in")
Dim scope As String = json.StringOf("scope")
Dim token_type As String = json.StringOf("token_type")
Dim client_id As String = json.StringOf("client_id")
Dim i As Integer = 0
Dim count_i As Integer = json.SizeOfArray("keys")
While i < count_i
    json.I = i
    kty = json.StringOf("keys[i].kty")
    n = json.StringOf("keys[i].n")
    e = json.StringOf("keys[i].e")
    use = json.StringOf("keys[i].use")
    alg = json.StringOf("keys[i].alg")
    x5t = json.StringOf("keys[i].x5t")
    i = i + 1
End While

' This example will save the JSON containing the access key to a file so that
' a subsequent example can load it and then use the access key for a request, such as to create a payment request.
json.WriteFile("qa_data/tokens/ing_access_token.json")