ToDataSourceResultAsync(...) and impersonation

3 posts, 1 answers
  1. Heiko
    Heiko avatar
    153 posts
    Member since:
    Oct 2012

    Posted 29 Aug 2018 Link to this post


    in my MVC-App I use <authentication mode="Windows" /> and <identity impersonate="true"/> inside web.config which means the current WindowsIdentity is delivered through IIS to SQL-Server. Normally I use the async/await pattern in my code and thus use ToDataSourceResultAsync(...) to get my filtered/sorted/paged results async. When doing so I run into an error. The call from App -> IIS -> SQL-Server is now under the normal "IIS APPPOOL\DefaultAppPool" account which is not a valid SQL-Server user and so the connection is refused. When using the normal ToDataSourceResult(...) call everything works perfect.

    The reason for this is the usage of "Task.Factory.StartNew(...)" inside QueryableExtensions.cs. Whenever you use "Task.Factory.StartNew(...)" the impersonation is reset to the default value and is NOT using the identity used inside the MVC-App. Here is a little example (just place the code inside a normal Controller Action):

    1.Debug.WriteLine("App is running as: {0}", WindowsIdentity.GetCurrent().Name);
    2.await Task.Factory.StartNew(
    3.    () =>
    4.    Debug.WriteLine("New Task is running as: {0}", WindowsIdentity.GetCurrent().Name),
    5.    CancellationToken.None,
    6.    TaskCreationOptions.None,
    7.    TaskScheduler.Default);


    As a result you get:
    Line 1: "App is running as: myDomain\myUser"
    Line 4: "New Task is running as: IIS APPPOOL\DefaultAppPool"

    At least you should warn in your documentation that this could happen or think about a better solution for implementing "ToDataSourceResultAsync(...)". In my opinion my scenario is not so seldom in the enterprise world so giving a warning should be a good idea.




  2. Answer
    Martin avatar
    833 posts

    Posted 31 Aug 2018 Link to this post


    Indeed you are correct about this behavior of ASP.NET. I have contacted our documentation team and they are going to add a line in our docs about it.
    According to the method implementation - I have logged an issue so that our developers can research whether better implementation of the method is possible.

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  3. Heiko
    Heiko avatar
    153 posts
    Member since:
    Oct 2012

    Posted 31 Aug 2018 in reply to Martin Link to this post

    Thanks a lot! 
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