There is a bug in Microsoft's Owin implementation for System.Web. The one that is being used when running Owin applications on IIS. Which is what probably 99% of us do, if we're using the new Owin-based authentication handling with ASP.NET MVC5.
The makes cookies set by Owin mysteriously disappear on some occasions. There is some documentation from Microsoft on workarounds, but this middleware offers another solution.
This middleware is a fix for that bug. Simple add it before any cookie handling middleware and it will preserve the authentication cookies.
app.UseKentorOwinCookieSaver();
app.UseCookieAuthentication(new CookieAuthenticationOptions());
In some cases, a pipeline stage specification might be needed. Using SignalR without other middleware containing a stage marker is such a case.
app.UseKentorOwinCookieSaver(PipelineStage.Authenticate);
The middleware is available as a nuget package, Kentor.OwinCookieSaver.
Due to how the cookies are handled, this middleware is only able to save cookies that are added by middleware; such as the authentication cookie. It won't save cookies handled by normal MVC Actions. In that case, the workaround of adding a dummy session value is recommended (if the application uses session, which is the most likely reason to be affected by this bug).
I've discussed contributing the functionality of this library directly to Katana to make this middleware redundant. However Microsoft do not want this behaviour added as it can affect cookie behaviour. In some cases it will loose newer flags on cookies. As ASP.NET Core is the clearly the route forward, there will be no more substantial development on this library.