What is a good way to pass additional information to the http response when issuing access token with Owin middleware in Asp Net Web Api? - asp.net-web-api

Question

I am using Owin middleware to implement token-based security for my application. When issuing the access token to the client I would also like to pass User Id along with the token, so that, the client application will know the User Id and will be able to call GetUserById (one of the methods inside UserController) in order to show the user his starting page. The best solution I could come up with so far is just adding User Id to the response header. Take a look at my OAuthAuthorizationServerProvider class, in GrantResourceOwnerCredentialsmethod I am adding User Id to the header, using context.Response.Headers.Add("User-Id", new string[] { "1" })
Here is the implementation of my OAuthAuthorizationServerProviderclass
public class AuthorizationServerProvider : OAuthAuthorizationServerProvider
{
public override async Task ValidateClientAuthentication(OAuthValidateClientAuthenticationContext context)
{
context.Validated();
}
public override async Task GrantResourceOwnerCredentials(OAuthGrantResourceOwnerCredentialsContext context)
{
var identity = new ClaimsIdentity(context.Options.AuthenticationType);
//The actual credential check will be added later
if (context.UserName=="user" && context.Password=="user")
{
identity.AddClaim(new Claim("Id", "1"));
context.Validated(identity);
//Here I am adding User Id to the response header
context.Response.Headers.Add("User-Id", new string[] { "1" });
}
else
{
context.SetError("invalid_grant","The credentials provided are not valid");
return;
}
}
}
Basically the client then will have to read User-Id from the header. Is this a good solution I came up with or there is a better one? Also what if I want to pass the whole User object with all its properties to the response is it possible and how to do this?

Answer 1

Since you store the ID already in the claims, why don't you just decode your token on the client and read out the user id like that? Passing it through the headers could allow tampering with it (security).
Have a look on how you could achieve to decode your token and read the claims. This is a c# example https://contos.io/peeking-inside-your-jwt-tokens-using-c-bf6a729d06c8 but this could also be done even through javascript.
This, assuming you use the JWT-format as token (was not specified in your initial question).

Answer 2

Bad way to store UserID as a response header back to client side. This is a huge security concern.
The best way would be to store it as a Claims.
It is very easy to achieve this and get back the claims in the client side.
In your controller, call this and remember to reference
using Microsoft.AspNet.Identity;
var userId = User.Identity.GetUserId();