(.NET) Access Token Generation (JWT)

iFormBuilder-API-AccessToken(.NET).cs

Imports System.Net

Imports System.Web

Imports System.IO

Imports Newtonsoft.Json

Imports Newtonsoft.Json.Linq

Imports System.Security.Cryptography

PublicClassiFormAPIMethods

    'iFormBuilder API info

    Private API_ClientKey AsString = "XXXXXXXXXXXXXXXXXXXXXXXXXXXXX"

    Private API_ClientSecret AsString = "XXXXXXXXXXXXXXXXXXXXXXXXXXX"

    Private BaseURL AsString = "CompanyName.iformbuilder.com"

    Private FullURL AsString = "https://" & BaseURL & "/exzact/api/oauth/token"

 

    'Quotation Mark Character for substitution

    Private q As Char = Chr(34)

 

    'JWT Claim Set Parameters

    Property iss As String = API_ClientKey

    Property aud As String = FullURL

 

    Property AccessToken As String

 

    PublicSubNew()

 

    EndSub

 

    Public Sub GetAccessToken()

 

        'Build web request

        Dim uriAddress As New Uri(FullURL)

        Dim wRequest As HttpWebRequest = DirectCast(HttpWebRequest.Create(uriAddress), HttpWebRequest)

 

        Dim strPostData As String = ""

        Dim bytPostData As Byte()

        Dim stJWT As String

 

        'Get JWT

        stJWT = CreateJWT()

 

        'Post Data ---

        strPostData = "grant_type=urn%3Aietf%3Aparams%3Aoauth%3Agrant-type%3Ajwt-bearer" & _

                  "&assertion=" & stJWT

 

        'Post Data --- to byte()

        bytPostData = System.Text.Encoding.UTF8.GetBytes(strPostData)

 

        'Set Web Request Properties

        With wRequest

            .Method = "POST"

            .ContentType = "application/x-www-form-urlencoded"

            .ContentLength = bytPostData.Length

        End With

 

        'Post Request and Get Response

        Using postStream As Stream = wRequest.GetRequestStream()

 

            postStream.Write(bytPostData, 0, bytPostData.Length)

 

            Dim rawResponseFromServer = ""

 

            Try

                Using response As HttpWebResponse = wRequest.GetResponse()

                    Dim reader As New StreamReader(response.GetResponseStream())

                    rawResponseFromServer = reader.ReadToEnd()

                    Dim o As JObject = JObject.Parse(rawResponseFromServer)

                    Me.AccessToken = o.Item("access_token").Value(Of String)()

                End Using

            Catch wex As WebException

                If Not wex.Response Is Nothing Then

                    MsgBox(wex.Message)

                    Debug.WriteLine("Resulting Error --- " & wex.Message & vbNewLine & wex.StackTrace)

                End If

            End Try

 

        End Using

 

 

    EndSub

 

#Region"HelperFunctions"

    PrivateFunction CreateJWT() AsString

 

        Dim JWT As String

        Dim EncodedJWT As Byte()

 

        'Build Header and Claim Set String

        Dim strHeader As String = Strings.Replace("{'alg':'HS256','typ':'JWT'}", "'", q)

        Dim strClaimSet As String = Strings.Replace("{'iss':'" & iss & "', 'aud':'" & aud & "', 'exp':" & exp(600) & ", 'iat':" & iat() & "}", "'", q)

 

        'Build JWT String

        JWT = ToBase64URL(strHeader) & "." & ToBase64URL(strClaimSet)

 

        'Convert Client Secret to UTF8 Byte()

        Dim bytKey As Byte() = System.Text.Encoding.UTF8.GetBytes(API_ClientSecret)

 

        'Encode JWT String

        Dim hmac_encode As HMACSHA256 = New HMACSHA256(bytKey)

        EncodedJWT = hmac_encode.ComputeHash(System.Text.Encoding.UTF8.GetBytes(JWT))

 

        'Sign and return JWT

        Dim signature As String = ToBase64URL(EncodedJWT)

 

        Return JWT & "." & signature

 

    EndFunction

 

    PrivateFunction ToBase64URL(text AsString) AsString

 

        Dim b As Byte() = System.Text.Encoding.UTF8.GetBytes(text)

        Return ToBase64URL(b)

 

    EndFunction

 

    PrivateFunction ToBase64URL(byt AsByte()) AsString

        Dim result As String

 

        'Convert to base 64 string

        result = Convert.ToBase64String(byt)

 

        'Make URL Friendly

        result = result.Replace("+", "-").Replace("/", "_")

 

        Do While result.Chars(result.Length - 1) = "="

            result = Strings.Left(result, result.Length - 1)

        Loop

 

        Return result

    EndFunction

 

    ReadOnly Property exp(ExpirationSeconds As Integer) As Long

        Get

            Return iat() + ExpirationSeconds

        End Get

    EndProperty

 

    ReadOnlyProperty iat() AsLong

        Get

            Dim StartDate As Date = CDate("1/1/1970")

            Dim EndDate As Date = Now.ToUniversalTime

            Dim val As Long = DateDiff(DateInterval.Second, StartDate, EndDate)

 

            Return val

        End Get

    EndProperty

#EndRegion

EndClass

Sample code for this example:
https://iformbuilder.zendesk.com/hc/en-us/articles/201989314--NET-Access-Token-generation-JWT-

My awesome comment!@#!@#!@#!@#

Perhaps I'm missing something, but this file has a .cs extension yet appears to contain VB. Also, there are random spaces missing all over... e.g PublicClassiFormAPIMethods, EndProperty, #EndRegion, EndClass etc. It might be worth re-uploading