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How to: Perform Custom Authentication Using SOAP Headers

This topic is specific to a legacy technology. XML Web services and XML Web service clients should now be created using Windows Communication Foundation .

The following custom solution is built using ASP.NET to provide an authentication mechanism using SOAP headers. The solution involves a custom IHttpModule on the Web server that executes the following steps:

  1. The HTTP Module parses HTTP messages to check whether they are SOAP messages.

  2. If the HTTP Module detects a SOAP message, it reads the SOAP headers.

  3. If the SOAP message has the SOAP header with authentication credentials, HTTP Module raises a custom global.asax event.

In the sample provided, the HTTP Module authenticates the user and sets Context properties that a Web service can use to decide whether the client is authorized access to the Web service.

9z52by6a.note(en-us,VS.100).gifNote:
In this sample, the text is sent over the network in clearly readable text (it is not encrypted). If clear text is not secure enough for your application, add an encryption algorithm.

Example

The following code example is an HTTP Module that parses HTTP messages for SOAP requests. If the HTTP message is a SOAP message, the custom WebServiceAuthenticationEvent is raised.

Public NotInheritable Class WebServiceAuthenticationModule
        Implements IHttpModule

        Public Delegate Sub WebServiceAuthenticationEventHandler(ByVal sender As [Object], ByVal e As WebServiceAuthenticationEvent)
        Private _eventHandler As WebServiceAuthenticationEventHandler = Nothing

        Public Custom Event Authenticate As 
                      WebServiceAuthenticationEventHandler
            AddHandler(ByVal value As 
                           WebServiceAuthenticationEventHandler)
                _eventHandler = value
            End AddHandler
            RemoveHandler(ByVal value As 
                       WebServiceAuthenticationEventHandler)
                _eventHandler = value
            End RemoveHandler
            RaiseEvent(ByVal sender As Object, 
                    ByVal e As WebServiceAuthenticationEvent)
            End RaiseEvent
        End Event

        Public Sub Dispose() Implements System.Web.IHttpModule.Dispose

        End Sub 'Dispose


        Public Sub Init(ByVal app As HttpApplication) Implements System.Web.IHttpModule.Init
            AddHandler app.AuthenticateRequest, AddressOf Me.OnEnter

        End Sub 'Init


        Private Sub OnAuthenticate(ByVal e As WebServiceAuthenticationEvent)
            If _eventHandler Is Nothing Then
                Return
            End If
            _eventHandler(Me, e)
            If Not (e.User Is Nothing) Then
                e.Context.User = e.Principal
            End If

        End Sub 'OnAuthenticate 

        Public ReadOnly Property ModuleName() As String
            Get
                Return "WebServiceAuthentication"
            End Get
        End Property

        Sub OnEnter(ByVal [source] As [Object], ByVal eventArgs As EventArgs)
            Dim app As HttpApplication = CType([source], HttpApplication)
            Dim context As HttpContext = app.Context
            Dim HttpStream As Stream = context.Request.InputStream

            ' Save the current position of stream.
            Dim posStream As Long = HttpStream.Position

            ' If the request contains an HTTP_SOAPACTION 
            ' header, look at this message.
            If context.Request.ServerVariables("HTTP_SOAPACTION") Is Nothing Then
                Return
            End If
            ' Load the body of the HTTP message
            ' into an XML document.
            Dim dom As New XmlDocument()
            Dim soapUser As String
            Dim soapPassword As String

            Try
                dom.Load(HttpStream)

                ' Reset the stream position.
                HttpStream.Position = posStream

                ' Bind to the Authentication header.
                soapUser = dom.GetElementsByTagName("User").Item(0).InnerText
                soapPassword = dom.GetElementsByTagName("Password").Item(0).InnerText
            Catch e As Exception
                ' Reset the position of stream.
                HttpStream.Position = posStream

                ' Throw a SOAP exception.
                Dim name As New XmlQualifiedName("Load")
                Dim soapException As New SoapException("Unable to read SOAP request", name, e)
                Throw soapException
            End Try

            ' Raise the custom global.asax event.
            OnAuthenticate(New WebServiceAuthenticationEvent(context, soapUser, soapPassword))
            Return

        End Sub 'OnEnter
    End Class 'WebServiceAuthenticationModule

The following code example is the custom authentication event that is raised by the HTTP Module, if a SOAP request is received.

Imports System
Imports System.Web
Imports System.Security.Principal

Public Class WebServiceAuthenticationEvent
    Inherits EventArgs
    Private _IPrincipalUser As Iprincipal
    Private _Context As HttpContext
    Private _User As String
    Private _Password As String
    
    
    Public Sub New(ByVal context As HttpContext) 
        _Context = context
    
    End Sub 'New
    
    
    Public Sub New(ByVal context As HttpContext, ByVal user As String, ByVal password As String) 
        _Context = context
        _User = user
        _Password = password
    
    End Sub 'New
    
    Public ReadOnly Property Context() As HttpContext 
        Get
            Return _Context
        End Get
    End Property
    
    Public Property Principal() As IPrincipal 
        Get
            Return _IPrincipalUser
        End Get
        Set
            _IPrincipalUser = value
        End Set
    End Property
    
    Overloads Public Sub Authenticate() 
        Dim i As New GenericIdentity(User)
        Me.Principal = New GenericPrincipal(i, New String(-1) {})
    
    End Sub 'Authenticate
    
    Overloads Public Sub Authenticate(ByVal roles() As String) 
        Dim i As New GenericIdentity(User)
        Me.Principal = New GenericPrincipal(i, roles)
    
    End Sub 'Authenticate
    
    Public Property User() As String 
        Get
            Return _User
        End Get
        Set
            _User = value
        End Set
    End Property
    
    Public Property Password() As String 
        Get
            Return _Password
        End Get
        Set
            _Password = value
        End Set
    End Property
    
    Public ReadOnly Property HasCredentials() As Boolean 
        Get
            If _User Is Nothing OrElse _Password Is Nothing Then
                Return False
            End If
            Return True
        End Get
    End Property
End Class 'WebServiceAuthenticationEvent

The following code example is the delegate for the custom WebServiceAuthenticationEvent event.

Imports System
Public Delegate Sub WebServiceAuthenticationEventHandler(ByVal sender As [Object], ByVal e As WebServiceAuthenticationEvent)

The following code example is a Web service that defines the Authentication SOAP header that a client must pass. The Web service does not have to do the authentication. Rather, it can inspect the User.Identity.IsAuthenticated property to determine if the HTTP Module has authenticated the user.

<%@ WebService Language="VB" Class="SecureWebService" %>

Imports System 
Imports System.Web.Services
Imports System.Web.Services.Protocols

Public Class Authentication
    Inherits SoapHeader
    Public User As String
    Public Password As String
End Class 'Authentication

Public Class SecureWebService
    Inherits WebService
    Public authentication As Authentication
    
    
    <WebMethod(), SoapHeader("authentication")>  _
    Public Function ValidUser() As String 
        If User.IsInRole("Customer") Then
            Return "User is in role customer"
        End If 
        If User.Identity.IsAuthenticated Then
            Return "User is a valid user"
        End If
        Return "not authenticated"
    
    End Function 'ValidUser
End Class 'SecureWebService

The following code example is a Web service client that passes the necessary credentials for a custom SOAP header authentication mechanism within an Authentication SOAP header.

' Create a new instance of a Web service proxy class.
Dim s As New SecureWebService()

' Create the Authentication SOAP header and set values.
Dim a As New Authentication()
a.User = user.Value
a.Password = password.Value

Assign the Header.
s.AuthenticationValue = a

Dim result As String = s.ValidUser()
span1.InnerHtml = result

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