AspNet Identity and Owin. Who is who.

Recently I have found an excellent question on Stackoverflow. The OP asks why does claim added to Idenetity after calling AuthenticationManager.SignIn still persist to the cookie.

The sample code was like this:

ClaimsIdentity identity = UserManager.CreateIdentity(user, DefaultAuthenticationTypes.ApplicationCookie );

var claim1 = new Claim(ClaimTypes.Country, "Arctica");

AuthenticationManager.SignIn(new AuthenticationProperties { IsPersistent = true }, identity );

var claim2 = new Claim(ClaimTypes.Country, "Antartica");

Yeah, why does claim2 is available after cookie is already set.

After much digging I have discovered that AspNet Identity framework does not set the cookie. OWIN does. And OWIN is part of Katana Project which has open source code. Having the source code available is always nice – you can find out yourself why things work or don’t work the way you expect.

In this case I have spent a few minutes navigating Katana project and how AuthenticationManager works. Turned out that SingIn method does not set a cookie. It saves Identity objects into memory until time comes to set response cookies. And then claims are converted to a cookie and everything magically works -)

This sparked another question. At the moment Identity does not have open source, but what is the role of OWIN in Identity and how Claims work here?

Turns out that Identity framework deals only with user persistence, password hashing, validating if the password is correct, sending out email tokens for password reset, etc. But Identity does not actually authenticate users or create cookies. Cookies are handled by OWIN.

Take a look on this code for signing in:

public async Task SignInAsync(Microsoft.Owin.Security.IAuthenticationManager authenticationManager, ApplicationUser applicationUser, bool isPersistent)

    ClaimsIdentity identity = await UserManager.CreateIdentityAsync(applicationUser, DefaultAuthenticationTypes.ApplicationCookie);

    authenticationManager.SignIn(new Microsoft.Owin.Security.AuthenticationProperties() { IsPersistent = isPersistent }, identity);

Identity only creates ClaimsIdentity which you can study on ReferenceSource site. And ClaimsIdentity is part of .Net framework, not some nuget-package from the interwebz. Then this claimsIdentity is passed to OWIN AuthenticationManager where a callback is set to assign cookies on when time comes to write headers on the response.

So far, so good, we have 3 parts here: Identity framework creating a ClaimsIdentity, OWIN creating a cookie from this ClaimsIdentity. And .Net framework which holds the class for ClaimsIdentity.

When in your classes you access ClaimsPrincipal.Current, you only use .Net framework, no other libraries are used. And this is very handy!

Default Claims

Identity framework does a nice thing for you. By default it adds a number of claims to a principal when user is logged in. Here is the list:

  • User.Id is added as claim type “” or by ClaimTypes.NameIdentifier
  • Username is added as claim type “” or by ClaimTypes.Name
  • “ASP.NET Identity” is saved as claim type ““. This is useful if you are using OpenId to do the authentication. Not much use if you are using only users stored in our database. See this page for more details.
  • Guid containing User’s Security Stamp is persisted in claim with type “AspNet.Identity.SecurityStamp“. Security Stamp is basically a snapshot of user state. If password/method of authentication, email, etc. is changed, Security Stamp is changed. This allows to “logout everywhere” on credentials change. Read more about what is security stamp in Hao Kung’s answer.
  • The most useful claims added by default are role. All roles assigned to the user are saved as ClaimTypes.Role or by ““. So next time you need to check current user’s roles, check the claims. This does not hit the database and is very quick. And in fact, if you call .IsInRole("RoleName") on ClaimsPrincipal, the framework goes into claims and checks if Role claims with this value is assigned.

You can find the list of framework claim types on .Net Reference site. However, this list is not complete. You can make up your own claim types as you are pleased – this is just a string.

If you want to add your own claim types, I recommend to use your own notation for the claim types. Something like “MyAppplication:GroupId” and keep all the claim types in one class as constants:

public class MyApplicationClaimTypes
    public string const GroupId = "MyAppplication:GroupId";
    public string const PersonId = "MyAppplication:PersonId";
    // other claim types

This way you can always find where the claims are used and will not clash with the framework claim types. Unless the claim you use matches framework claim types exactly, like ClaimTypes.Email.

Adding default claims

I always add user’s email to the list of claims. I do that on user sign-in, same way the first code snippet adds claim1 and claim2:

public async Task SignInAsync(IAuthenticationManager authenticationManager, ApplicationUser applicationUser, bool isPersistent)

    var identity = await this.CreateIdentityAsync(applicationUser, DefaultAuthenticationTypes.ApplicationCookie);

    // using default claim type from the framework
    identity.AddClaim(new Claim(ClaimTypes.Email, applicationUser.Email));

    authenticationManager.SignIn(new AuthenticationProperties() { IsPersistent = isPersistent }, identity);

You can add your default claims to all users here as well. But there is IClaimsIdentityFactory class that is assigned in UserManager. There is only one method there:

public interface IClaimsIdentityFactory<TUser, TKey> where TUser : class, IUser<TKey> where TKey : IEquatable<TKey>
    /// <summary>
    /// Create a ClaimsIdentity from an user using a UserManager
    /// </summary>
    Task<ClaimsIdentity> CreateAsync(UserManager<TUser, TKey> manager, TUser user, string authenticationType);

Default AspNet Identity implementation creates ClaimsIdentity, adds the default claims described above, adds claims stored in the database for the user: IdentityUserClaims. You can override this implementation and slip-in your own logic/claims:

public class MyClaimsIdentityFactory : ClaimsIdentityFactory<ApplicationUser, string>
    public override async Task<ClaimsIdentity> CreateAsync(UserManager<ApplicationUser, string> userManager, ApplicationUser user, string authenticationType)
        var claimsIdentity = await base.CreateAsync(userManager, user, authenticationType);

        claimsIdentity.AddClaim(new Claim("MyApplication:GroupId", "42"));

        return claimsIdentity;

and assign it in UserManager:

public UserManager(MyDbContext dbContext)
    : base(new UserStore<ApplicationUser>(dbContext))
    // other configurations

    // Alternatively you can have DI container to provide this class for better application flexebility
    this.ClaimsIdentityFactory = new MyClaimsIdentityFactory();