File Path for PersistKeysToFileSystem on shared server

Question

I'm trying to make my keys persist for users that log in. As I'm currently using shared hosting for the website, I've decided to use the file system to store the keyring. So the code looks like this:

services.AddDataProtection()
.PersistKeysToFileSystem(new DirectoryInfo(""))
.SetApplicationName("MyWebsite")
.SetDefaultKeyLifetime(TimeSpan.FromDays(90))
.ProtectKeysWithCertificate(cert);

However, what I'm not really understanding is where I should hold these keys, and what would be the path I pass in in order for them to be there. Since this is an MVC Core Application I am a little confused, in an MVC 5 I would put it in App_Data folder, but here there is no App_Data folder and I want to make sure it stays secure and cannot be accessed via the browser.

The other thing is do I pass it a relative path or a direct path? If it is relative, where is my starting point? Is it bin, root directory or something else?

Answer 1

The simplest way is probably to create a folder inside the app folder. For example, create a folder called Keys, and use the IHostingEnvironment object to get the app folder. Something like this:

public class Startup
{
    private readonly IHostingEnvironment _environment;

    public Startup(IHostingEnvironment environment)
    {
        _environment = environment;
    }

    public void ConfigureServices(IServiceCollection services)
    {
        var keysFolder = Path.Combine(_environment.ContentRootPath, "Keys");

        services.AddDataProtection()
            .PersistKeysToFileSystem(new DirectoryInfo(keysFolder))
            .SetApplicationName("MyWebsite")
            .SetDefaultKeyLifetime(TimeSpan.FromDays(90))
            .ProtectKeysWithCertificate(cert);
    }

    // snip
}