' Authenticate is the core method for this custom authentication.
  ' When an Internet resource requests authentication, the WebRequest.GetResponse 
  ' method calls the AuthenticationManager.Authenticate method. This method, in 
  ' turn, calls the Authenticate method on each of the registered authentication
  ' modules, in the order in which they were registered. When the authentication is 
  ' complete an Authorization object is returned to the WebRequest.
  Public Function Authenticate(ByVal challenge As String, ByVal request As WebRequest, ByVal credentials As ICredentials) As Authorization _
      Implements IAuthenticationModule.Authenticate


    Dim ASCII As Encoding = Encoding.ASCII

    ' Get the username and password from the credentials
    Dim MyCreds As NetworkCredential = credentials.GetCredential(request.RequestUri, "Basic")

    If PreAuthenticate(request, credentials) Is Nothing Then
      Console.WriteLine(ControlChars.Lf + " Pre-authentication is not allowed.")
    Else
      Console.WriteLine(ControlChars.Lf + " Pre-authentication is allowed.")
    End If
    ' Verify that the challenge satisfies the authorization requirements.
    Dim challengeOk As Boolean = checkChallenge(challenge, MyCreds.Domain)

    If Not challengeOk Then
      Return Nothing
    End If

    ' Create the encrypted string according to the Basic authentication format as
    ' follows:
    ' a)Concatenate the username and password separated by colon;
    ' b)Apply ASCII encoding to obtain a stream of bytes;
    ' c)Apply Base64 encoding to this array of bytes to obtain the encoded 
    ' authorization.
    Dim BasicEncrypt As String = MyCreds.UserName + ":" + MyCreds.Password

    Dim BasicToken As String = "Basic " + Convert.ToBase64String(ASCII.GetBytes(BasicEncrypt))

    ' Create an Authorization object using the encoded authorization above.
    Dim resourceAuthorization As New Authorization(BasicToken)

    ' Get the Message property, which contains the authorization string that the 
    ' client returns to the server when accessing protected resources.
    Console.WriteLine(ControlChars.Lf + " Authorization Message:{0}", resourceAuthorization.Message)

    ' Get the Complete property, which is set to true when the authentication process 
    ' between the client and the server is finished.
    Console.WriteLine(ControlChars.Lf + " Authorization Complete:{0}", resourceAuthorization.Complete)

    Console.WriteLine(ControlChars.Lf + " Authorization ConnectionGroupId:{0}", resourceAuthorization.ConnectionGroupId)


    Return resourceAuthorization
  End Function 'Authenticate
End Class

Function Authenticate(ByVal challenge As String, ByVal request As WebRequest, ByVal credentials As ICredentials) As Authorization Implements IAuthenticationModule.Authenticate
    Try
        Dim message As String
        ' Check if Challenge string was raised by a site which requires 'CloneBasic' authentication.
        If challenge Is Nothing Or Not challenge.StartsWith("CloneBasic") Then
            Return Nothing
        End If
        Dim myCredentials As NetworkCredential
        If TypeOf credentials Is CredentialCache Then
            myCredentials = credentials.GetCredential(request.RequestUri, "CloneBasic")
            If myCredentials Is Nothing Then
                Return Nothing
            End If
        Else
            myCredentials = CType(credentials, NetworkCredential)
        End If
        ' Message encryption scheme : 
        ' a)Concatenate username and password seperated by space
        ' b)Apply ASCII encoding to obtain a stream of bytes
        ' c)Apply Base64 Encoding to this array of bytes to obtain our encoded authorization message
        message = myCredentials.UserName + " " + myCredentials.Password
        ' Apply AsciiEncoding to 'message' string to obtain it as an array of bytes.
        Dim ascii As Encoding = Encoding.ASCII
        Dim byteArray(ascii.GetByteCount(message)) As Byte
        byteArray = ascii.GetBytes(message)

        ' Performing Base64 transformation.
        message = Convert.ToBase64String(byteArray)
        Dim myAuthorization As New Authorization("CloneBasic " + message, True)
        Dim protectionRealm() As String = {request.RequestUri.AbsolutePath}
        myAuthorization.ProtectionRealm = protectionRealm

        Return myAuthorization
    Catch e As Exception
        Console.WriteLine("The following exception was raised in Authenticate method:{0}", e.Message)
        Return Nothing
    End Try
End Function 'Authenticate

Public Function Authenticate(challenge As String, request As WebRequest, credentials As ICredentials) As Authorization Implements IAuthenticationModule.Authenticate
    Try
        Dim message As String
        ' Check if Challenge string was raised by a site which requires CloneBasic authentication.
        If challenge Is Nothing Or Not challenge.StartsWith("CloneBasic") Then
            Return Nothing
        End If
        Dim myCredentials As NetworkCredential
        If TypeOf credentials Is CredentialCache Then
            myCredentials = credentials.GetCredential(request.RequestUri, "CloneBasic")
            If myCredentials Is Nothing Then
                Return Nothing
            End If
        Else
            myCredentials = CType(credentials, NetworkCredential)
        End If 'Message encryption scheme : 
        '        a)Concatenate username and password seperated by space
        '        b)Apply ASCII encoding to obtain a stream of bytes
        '        c)Apply Base64 Encoding to this array of bytes to obtain our encoded authorization message

        message = myCredentials.UserName + " " + myCredentials.Password
        'Apply AsciiEncoding to our user name and password to obtain it as an array of bytes
        Dim asciiEncoding As Encoding = Encoding.ASCII
        Dim byteArray(asciiEncoding.GetByteCount(message)) As Byte
        byteArray = asciiEncoding.GetBytes(message)

        'Perform Base64 transform
        message = Convert.ToBase64String(byteArray)
        'The following overloaded contructor sets the 'Message' property of authorization to the base64 string
        '         *that  we just formed and it also sets the 'Complete' property to true and the connection group id
        '         *to the domain of the NetworkCredential object
        Dim myAuthorization As New Authorization("CloneBasic " + message, True, request.ConnectionGroupName)
        Return myAuthorization
    Catch e As Exception
        Console.WriteLine(("Exception Raised ...:" + e.Message))
        Return Nothing
    End Try
End Function 'Authenticate