Owin cookie身份验证偶尔会抛出NullReferenceException

我在一个设置为ASP.NET MVC和WebApi应用程序的项目中使用OWIN cookie身份验证中间件(即我添加了OWIN).

偶尔,当我做了一些更改并开始调试时,我得到一个异常,这个异常发生在每个请求上好一分钟左右,直到网站突然工作,没有任何问题.我在我的本地IIS中托管应用程序.

System.NullReferenceException: Object reference not set to an instance of an object.
   at FooWeb.Startup.<>c.b__0_3(CookieExceptionContext context) in C:\ws\Foo\Main\Main\FooWeb\Startup.cs:line 138
   at Microsoft.Owin.Security.Cookies.CookieAuthenticationHandler.d__f.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Microsoft.Owin.Security.Infrastructure.AuthenticationHandler.d__b.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Microsoft.Owin.Security.Infrastructure.AuthenticationHandler.d__8.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Microsoft.Owin.Security.Infrastructure.AuthenticationHandler.d__5.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Microsoft.Owin.Security.Infrastructure.AuthenticationMiddleware`1.d__0.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Microsoft.Owin.Host.SystemWeb.IntegratedPipeline.IntegratedPipelineContextStage.d__5.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Microsoft.Owin.Host.SystemWeb.IntegratedPipeline.IntegratedPipelineContext.d__2.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at Microsoft.Owin.Host.SystemWeb.IntegratedPipeline.StageAsyncResult.End(IAsyncResult ar)
   at System.Web.HttpApplication.AsyncEventExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute()
   at System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously);

我像这样设置中间件:

app.UseCookieAuthentication(new CookieAuthenticationOptions
{
    AuthenticationType = "Cookies",
    LoginPath = new PathString("/Account/Login"),
    LogoutPath = new PathString("/Account/Logoff"),
    CookieName = "FooWebCookieAuth",
    SlidingExpiration = true,
    ExpireTimeSpan = TimeSpan.FromMinutes(10),
    CookieSecure = CookieSecureOption.Always,

    Provider = new CookieAuthenticationProvider()
    {
        OnValidateIdentity = async context =>
        {
            // Validate access token
            if (context == null)
            {
                return;
            }

            if (context.Identity == null || !context.Identity.IsAuthenticated)
            {
                return;
            }

            if (context.Identity.Claims == null)
            {
                context.RejectIdentity();
            }

            var accessTokenClaim = context.Identity.Claims.FirstOrDefault(x => x.Type == FooClaimTypes.Token);
            var accessToken = (accessTokenClaim == null) ? null : accessTokenClaim.Value;
            if (accessToken == null)
            {
                context.RejectIdentity();
            }
            else
            {
                var client = new IntrospectionClient(
                    SecurityTokenServiceEndpoints.Introspection,
                    "FooScope", 
                    "FooSecret");
                var validationResult = await client.SendAsync(new IntrospectionRequest()
                {
                    Token = accessToken
                });

                if (validationResult.IsError || !validationResult.IsActive)
                {
                    context.RejectIdentity();
                }
            }
        },
        OnException = context =>
        {
            // exception is thrown here (so that debugging stops). Without this it just faults
            throw context.Exception;
        },
    },
});

更新这似乎与cookie或至少与浏览器有关 - 因为我在浏览器中有一个会话,它会一直抛出该异常,而其他浏览器(以前也登录过)也可以正常访问它.