Asp.Net 5 Authentication cookie is reset after every rebuild - How can I truly persist it?

Question

I have a problem with an Asp.Net 5 application I'm currently developing. Essentially it's an anonymous page with user-attached data, so I'm very much dependant on having a persistent and reliable cookie to identify a calling user. Therefore, I have also checked how I need to configure cookies, and put them on a very long expiration timespan, and made them persistent.

Here is my code:

In my Startup.cs:

services.AddAuthentication(CookieAuthenticationDefaults.AuthenticationScheme)
        .AddCookie(options =>
        {
            options.Events.OnRedirectToLogin = context =>
            {
                context.Response.StatusCode = 401;
                return Task.CompletedTask;
            };

            options.ExpireTimeSpan = TimeSpan.FromDays(100 * 365);
            options.Cookie.HttpOnly = true;
            options.Cookie.SecurePolicy = CookieSecurePolicy.Always;
            options.Cookie.MaxAge = TimeSpan.FromDays(100 * 365);
            options.Cookie.SameSite = _webHostEnvironment.IsDevelopment() ? SameSiteMode.None : SameSiteMode.Strict;
            options.Cookie.Name = Configuration["IdentificationCookieName"];
        });

Obviously I also included the required calls in the Configure method:

app.UseAuthentication();
app.UseAuthorization();

In the controller for setting the cookie, I'm using the following code:

var identity = new ClaimsIdentity(CookieAuthenticationDefaults.AuthenticationScheme);
identity.AddClaim(new Claim(ClaimTypes.Name, callerId.ToString()));

var principal = new ClaimsPrincipal(identity);

await HttpContext.SignInAsync(
    CookieAuthenticationDefaults.AuthenticationScheme,
    principal,
    new AuthenticationProperties()
    {
          IsPersistent = true,
          ExpiresUtc = DateTime.UtcNow.AddYears(100),
          AllowRefresh = true,
    }
);

Where am I going wrong here? This seems to occur after every rebuild.

Answer 1

Thanks to Roar S.'s comment which pointed me in the right direction, I was able to figure out the problem:

The key point - my application is running in a container, which is restarted on rebuild. The culprit is indeed the data protection section - All cookie encryption keys stored on the machine are also regenerated when the container restarts.

Therefore it is required to setup the.AddDataProtection section to either use a cloud-based storage, or a simple file mount for local development.

This is what I ended up using:

In my docker-compose file, I added a mount:

volumes:
  - ./Keys/Storage:/keys/storage

And in my startup script:

if (IsDevelopmentEnvironment())
{
     services.AddDataProtection()
         .PersistKeysToFileSystem(new DirectoryInfo("/keys/storage"));
}

Now the cookies are stable.