Adding Claims to Identity from my WebApi - asp.net-web-api

Question

I am currently developing a Web Application that contains a Angular4 UI working with IdentitServer4 and a WebApi dotnetcore application.
We have the application authentication mechanism working with IDS but we now want to limit parts of our Angular application based on what permissions a user has granted them. This information is stored behind our WebApi. These permissions would also be used to secure our WebApi from stopping users doing particular actions if they aren't allowed i.e. EditUsers.
the problem I am facing is that ideally after being authentication by IdentityServer I would like the Angular application to fetch the list of allowed
permissions and from there they send those up to the WebApi as part of their claims. The reason for this is that I don't want to have to query the database
on each Api Call if I can help it just to see if a particular user has access to a particular Controller action.
Is there anyway that I can set these claims so that subsequent calls to the API contains these and from there I can just check the claim information on the User Claim Identity
to verify access to a resource?

Answer 1

You can add scope to your WebApi (official docs) for example
app.UseIdentityServerAuthentication(new IdentityServerAuthenticationOptions
{
Authority = "https://demo.identityserver.io",
ApiName = "api1",
AllowedScopes = { "api1.read", "api1.write" }
AutomaticAuthenticate = true,
AutomaticChallenge = true
});
And you can add claims to the client application as:
var mvcClient = new Client
{
ClientId = "mvc",
ClientName = "MVC Client",
ClientUri = "http://identityserver.io",
AllowedGrantTypes = GrantTypes.Hybrid,
AllowOfflineAccess = true,
ClientSecrets = { new Secret("secret".Sha256()) },
RedirectUris = { "http://localhost:5002/signin-oidc" },
PostLogoutRedirectUris = { "http://localhost:5002/" },
LogoutUri = "http://localhost:5002/signout-oidc",
AllowedScopes =
{
IdentityServerConstants.StandardScopes.OpenId,
IdentityServerConstants.StandardScopes.Profile,
IdentityServerConstants.StandardScopes.Email,
"api1", "api2.read"
},
};
This is application base, for assigning permissions per user, you can define roles in your scopes for the user and can then decorate your controller or methods with that Role for ex:
For admin: new Claim("role","Admin")
For guestuser: new Claim("role","guest")
[HttpGet]
[Authorize(Roles = "Admin")]
public IActionResult Edit()
{
//whatever
}
[Authorize(Roles = "Guest")]
[HttpGet]
public IActionResult View()
{
//whatever
}