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IAuthenticationModule Interface

Provides the base authentication interface for Web client authentication modules.

Namespace:  System.Net
Assembly:  System (in System.dll)

Public Interface IAuthenticationModule

The IAuthenticationModule type exposes the following members.

Public propertyAuthenticationTypeGets the authentication type provided by this authentication module.
Public propertyCanPreAuthenticateGets a value indicating whether the authentication module supports preauthentication.

Public methodAuthenticateReturns an instance of the Authorization class in respose to an authentication challenge from a server.
Public methodPreAuthenticateReturns an instance of the Authorization class for an authentication request to a server.

The IAuthenticationModule interface defines the properties and methods that custom authentication modules must use.

Authentication modules conduct the entire authentication process with a server, responding to an authentication challenge as appropriate. This process may consist of requests to an authentication server separate from the resource server, as well as any other activities required to properly authenticate a request for a URI.

Custom authentication modules should implement the IAuthenticationModule interface and then register with the AuthenticationManager.Register method. Authentication modules are also registered at program initialization by reading the configuration file.

The following example creates creates a customized authentication class by implementing the IAuthenticationModule interface. For a complete example refer to the AuthenticationManager class.

' The CustomBasic class creates a custom Basic authentication by implementing the
' IAuthenticationModule interface. It performs the following
' tasks:
' 1) Defines and initializes the required properties.
' 2) Implements the Authenticate and PreAuthenticate methods.

Public Class CustomBasic
  Implements IAuthenticationModule

  Private m_authenticationType As String
  Private m_canPreAuthenticate As Boolean

  ' The CustomBasic constructor initializes the properties of the customized 
  ' authentication.
  Public Sub New()
    m_authenticationType = "Basic"
    m_canPreAuthenticate = False
  End Sub 'New

  ' Define the authentication type. This type is then used to identify this
  ' custom authentication module. The default is set to Basic.

  Public ReadOnly Property AuthenticationType() As String _
   Implements IAuthenticationModule.AuthenticationType

      Return m_authenticationType
    End Get
  End Property

  ' Define the pre-authentication capabilities for the module. The default is set
  ' to false.

  Public ReadOnly Property CanPreAuthenticate() As Boolean _
   Implements IAuthenticationModule.CanPreAuthenticate

      Return m_canPreAuthenticate
    End Get
  End Property

' The checkChallenge method checks whether the challenge sent by the HttpWebRequest 
' contains the correct type (Basic) and the correct domain name. 
' Note: The challenge is in the form BASIC REALM="DOMAINNAME"; 
' the Internet Web site must reside on a server whose
' domain name is equal to DOMAINNAME.
  Public Function checkChallenge(ByVal Challenge As String, ByVal domain As String) As Boolean
    Dim challengePasses As Boolean = False

    Dim tempChallenge As [String] = Challenge.ToUpper()

    ' Verify that this is a Basic authorization request and that the requested domain
    ' is correct.
    ' Note: When the domain is an empty string, the following code only checks 
    ' whether the authorization type is Basic.
    If tempChallenge.IndexOf("BASIC") <> -1 Then
      If domain <> [String].Empty Then
        If tempChallenge.IndexOf(domain.ToUpper()) <> -1 Then
          challengePasses = True
          ' The domain is not allowed and the authorization type is Basic.
          challengePasses = False
        End If
        ' The domain is a blank string and the authorization type is Basic.
        challengePasses = True
      End If
    End If
    Return challengePasses
  End Function 'checkChallenge

  ' The PreAuthenticate method specifies whether the authentication implemented 
  ' by this class allows pre-authentication. 
  ' Even if you do not use it, this method must be implemented to obey to the rules 
  ' of interface implementation.
  ' In this case it always returns null. 
  Public Function PreAuthenticate(ByVal request As WebRequest, ByVal credentials As ICredentials) As Authorization _
      Implements IAuthenticationModule.PreAuthenticate

    Return Nothing
  End Function 'PreAuthenticate

  ' 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.")
      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 'CustomBasic 

.NET Framework

Supported in: 4, 3.5, 3.0, 2.0, 1.1, 1.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows XP SP2 x64 Edition, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.