User set to nothing in ASP.NET WebForms HTTP Module - webforms

Question

I have the below custom module in an asp.net web application. The module works from chrome on my PC but when I try to access a video from Android I get an error because the userid (_context.User) is not set. This all occurs after I have logged into the application. Therefore _context.User should be set.
I would have thought because at this level you are dealing with HTTP Requests and Responses that the module would work for any device.
I have two questions.
Is there a way to make this work?
What is the difference between the requests sent by the Android tablet and PC to cause this issue?
Public Class VideoSecurityModule
Implements IHttpModule
Implements IRequiresSessionState
Private WithEvents _context As HttpApplication
Public Sub Dispose() Implements IHttpModule.Dispose
End Sub
Dim myUserManager As UserManager
Public Sub Init(ByVal context As HttpApplication) Implements IHttpModule.Init
_context = context
myUserManager = New UserManager
End Sub
Public Sub Log(value As String, ParamArray args As Object())
Dim message As String = String.Format(value, args)
Dim messagePrefix As String = String.Format("{0},{1},{2},{3}", UserAgent, Url, SessionId, message)
LogManager.WriteMessage(messagePrefix, "")
End Sub
Private ReadOnly Property UserAgent() As String
Get
Try
Return _context.Request.UserAgent
Catch ex As Exception
Return "No User Agent"
End Try
End Get
End Property
Private ReadOnly Property Url() As String
Get
Try
Return _context.Request.Url.PathAndQuery
Catch ex As Exception
Return "No URL"
End Try
End Get
End Property
Private ReadOnly Property SessionId() As String
Get
Try
Return __context.Session.SessionID
Catch ex As Exception
Return "No URL"
End Try
End Get
End Property
Public ReadOnly Property IsReusable() As Boolean
' IsReusable must be set to false since class has a member!
Get
Return True
End Get
End Property
Public Sub OnAuthorizeRequest(ByVal source As Object, ByVal e As EventArgs) Handles _context.AuthorizeRequest
If IsVideoUrl() Then
Dim userId As Integer = GetLoggedInUsersId()
Log("UserRequiresAuthorization({0}): {1}", userId, UserRequiresAuthorization(userId))
Log("UserIsAssignedToCourseContainingVideo({0}): {1}", userId, UserIsAssignedToCourseContainingVideo(userId))
' if user is not assigned to a course that utilizes the video or the user is not in role super user or system admin
If (UserRequiresAuthorization(userId) AndAlso Not UserIsAssignedToCourseContainingVideo(userId)) Then
SendAuthenticationRequiredResponse()
End If
End If
End Sub
Private Function GetLoggedInUsersId() As Integer
Dim userId As Integer = 0
If (Not _context.User Is Nothing) Then
userId = myUserManager.GetUserIdByUserName(_context.User.Identity.Name)
End If
Log("userId:{0}", userId)
Return userId
End Function
Private Sub SendAuthenticationRequiredResponse()
Const networkAuthenticationRequiredStatusCode As Integer = 511
_context.Response.StatusCode = networkAuthenticationRequiredStatusCode
_context.Response.ClearContent()
_context.Response.Write("UnAuthorized User")
Log("UnAuthorized User: {0}", "")
_context.Response.End()
End Sub
Private Function IsVideoUrl() As Boolean
Dim fileLocation As String = System.Configuration.ConfigurationManager.AppSettings("VideoLocation")
Log("url:{0}", _context.Request.Url)
Log("IsVideoUrl:{0}", _context.Request.FilePath.ToLower().Contains(fileLocation.ToLower()))
Return _context.Request.FilePath.ToLower().Contains(fileLocation.ToLower())
End Function
Private Function UserDoesNotRequireAuthorization(userId As Integer) As Boolean
Return myUserManager.IsSysAdmin(userId) OrElse myUserManager.IsSuperUser(userId)
End Function
Private Function UserRequiresAuthorization(userId As Integer) As Boolean
Dim result As Boolean = Not UserDoesNotRequireAuthorization(userId)
Return result
End Function
''' <summary>
''' Returns true if the in-putted user (logged in user) has been allocated to a course that utilize video specified in this request
''' </summary>
Private Function UserIsAssignedToCourseContainingVideo(userId As Integer) As Boolean
' ... code removed for clarity
End Function
End Class

Answer 1

This is a known issue with a number versions of android. My limited research suggests that video requests are passed to a separate component in android called stagefright. Stagefright can not handle cookies and therefore no authentication cookie is passed to the web application resulting in the _context.User property not being set.
The following links provide more in depth details.
Do Mobile Browsers send httpOnly cookies via the HTML5 Audio-Tag?
https://code.google.com/p/android/issues/detail?id=17553