How do I use Identity Policy in my Blazor app?

Question

How do I use Identity Policy in my Blazor app?

David Thielen 3,211

Hi all;

Ok, I'm diving in to using the authorization part of the Identity library. I have the Identity library scaffolded in, authentication is working, and I have created pages to CRUD claims. (And I have read this multiple times.)

I want to do two things with authorization. First is I want to create three policies. One of the policies IsAdmin(). This will be true if any claim of the user has a type that starts with "Admin". I'll use this for page access:

@attribute [Authorize(Policy = "IsAdmin")]

How do I access the Task<AuthenticationState> (or get all the user's claims some other way) in the policy.RequireAssertion()?
Where/how do I add an options.AddPolicy() to the system globally?

Then within a page I will be determining what rows of data to pass in to listboxes and what controls to enable/disable (i.e. a user may be allowed to read but not update or delete) based on the claims the user has.

I need the specific (type,value) for each because that will be things like ("Manager:CO-03", "read") which tells me they can view the data in "CO-03" and they have read rights to it.

Can I use AuthenticationState.User.Claims to get the claims?
1. Or do I need to call UserManager.GetClaimsAsync(user)?
2. In the second case, how can I get the IdentityUser.Id from AuthenticationState (the solutions I've seen for this strike me as hacks)?
Do I then just work with that as any other IList<Claim>?

And if any of the above strikes you as a sub-optimal way to approach this, please let me know.

thanks - dave

Xiaotian Yang-MSFT 85 Reputation points

2023-06-20T06:56:54.58+00:00
It's possible to use AuthenticationState to get claims.

First inject @inject AuthenticationStateProvider AuthenticationStateProviderto your component.

Then in the code-behind file of your component, you can get the user's claims from the authentication state:

var authenticationState = await AuthenticationStateProvider.GetAuthenticationStateAsync(); var user = authenticationState.User; var claims = user.Claims;

Now you can iterate through them and access the specific claim types and values you need:

foreach (var claim in claims) { var type = claim.Type; var value = claim.Value; // Use the type and value as needed }

2 answers

Your answer

Xiaotian Yang-MSFT 85 Reputation points

2023-06-20T06:56:54.58+00:00

It's possible to use AuthenticationState to get claims.

First inject @inject AuthenticationStateProvider AuthenticationStateProviderto your component.

Then in the code-behind file of your component, you can get the user's claims from the authentication state:

var authenticationState = await AuthenticationStateProvider.GetAuthenticationStateAsync(); var user = authenticationState.User; var claims = user.Claims;

Now you can iterate through them and access the specific claim types and values you need:

foreach (var claim in claims) { var type = claim.Type; var value = claim.Value; // Use the type and value as needed }

Answer 1

Helga Stroman 0

Identity Policy is a feature of ASP.NET Core Identity that allows you to define access control policies in your application based on claims and roles. These policies can be used to restrict access to certain parts of your Blazor app based on the user's identity.

Here's how you can use Identity Policy in your Blazor app:

Install the necessary packages: In your Blazor app, install the following packages if they are not already installed: Microsoft.AspNetCore.Authorization and Microsoft.AspNetCore.Components.Authorization.
Configure services: Open the Startup.cs file and add the following lines of code inside the ConfigureServices method:


services.AddAuthorization(options =>

{

    options.AddPolicy("RequireAdminRole",

        policy => policy.RequireRole("admin"));

});

This code adds a policy called "RequireAdminRole" which requires users to have a role of "admin" in order to access resources protected by this policy.

Authorize components or routes: To protect certain components or routes with this policy, annotate them using the [Authorize] attribute with the desired policy name:


[Authorize(Policy = "RequireAdminRole")]

public class AdminPage : ComponentBase ...

Alternatively, you can annotate an entire page in Blazor with a @attribute [Authorize] directive.

Check for authorization status: You can determine whether a user is authorized to access a resource by injecting an instance of AuthorizationService in your component and calling its methods like await AuthorizationService.AuthorizeAsync(User,"RequireAdminRole").

That's it! With these steps, you have set up Identity Policy in your Blazor app.

David Thielen 3,211 Reputation points

2023-06-19T18:08:50.4433333+00:00
Hi;

Thank you, a couple of follow-on questions:

How do I add a policy that requires a claim (your example is a role)?

The [Authorize] attribute, isn't that for MVC razor and not Blazor pages? Or is that the way to set this in the AdminPage.razor.cs file?

How do I check against all claims for a user in my code? I need to get all the claims to then determine what data to show them.

thanks - dave
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Bruce (SqlWork.com) 77,926 Volunteer Moderator

to use a claim for policy in program.cs:

builder.Services.AddAuthorization(options =>
{
    options.AddPolicy("RequireAdminRole", policy => policy.RequireClaim("http://schemas.xmlsoap.org/ws/2005/05/identity/claims/name"));
});

sample page to list claims:

@page "/claims"
@attribute [Authorize(Policy = "RequireAdminRole")]

<PageTitle>List Claims</PageTitle>
<h1>List Claims for @userName</h1>
<p>This component demonstrates listing user claims</p>
<table class="table">
    <thead>
        <tr><th>Claim</th><th>Value</th></tr>
    </thead>
    <tbody>
        @foreach (var claim in claims)
        {
            <tr><td>@claim.Type</td><td>@claim.Value</td></tr>
        }
    </tbody>
</table>

@code
{
    [CascadingParameter]
    private Task<AuthenticationState>? authenticationState { get; set; }
    private List<System.Security.Claims.Claim> claims = new List<System.Security.Claims.Claim>();
    private string userName = "unknown";

    protected override async Task OnInitializedAsync()
    {
        if (authenticationState is not null)
        {
            var authState = await authenticationState;
            var user = authState?.User;
            if (user != null)
            {
                userName = user.Identity?.Name ?? userName;
                claims = user.Claims.ToList();
            }
        }
    }
}

Answer 2

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How do I use Identity Policy in my Blazor app?

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