ASP.NET Core Blazor authentication and authorization
Note
This isn't the latest version of this article. For the current release, see the .NET 9 version of this article.
Warning
This version of ASP.NET Core is no longer supported. For more information, see the .NET and .NET Core Support Policy. For the current release, see the .NET 9 version of this article.
Important
This information relates to a pre-release product that may be substantially modified before it's commercially released. Microsoft makes no warranties, express or implied, with respect to the information provided here.
For the current release, see the .NET 9 version of this article.
This article describes ASP.NET Core's support for the configuration and management of security in Blazor apps.
Security scenarios differ between authorization code running server-side and client-side in Blazor apps. For authorization code that runs on the server, authorization checks are able to enforce access rules for areas of the app and components. Because client-side code execution can be tampered with, authorization code executing on the client can't be trusted to absolutely enforce access rules or control the display of client-side content.
If authorization rule enforcement must be guaranteed, don't implement authorization checks in client-side code. Build a Blazor Web App that only relies on server-side rendering (SSR) for authorization checks and rule enforcement.
If authorization rule enforcement and the security of data and code must be guaranteed, don't develop a client-side app. Build a Blazor Server app.
Razor Pages authorization conventions don't apply to routable Razor components. If a non-routable Razor component is embedded in a page of a Razor Pages app, the page's authorization conventions indirectly affect the Razor component along with the rest of the page's content.
ASP.NET Core Identity is designed to work in the context of HTTP request and response communication, which generally isn't the Blazor app client-server communication model. ASP.NET Core apps that use ASP.NET Core Identity for user management should use Razor Pages instead of Razor components for Identity-related UI, such as user registration, login, logout, and other user management tasks. Building Razor components that directly handle Identity tasks is possible for several scenarios but isn't recommended or supported by Microsoft.
ASP.NET Core abstractions, such as SignInManager<TUser> and UserManager<TUser>, aren't supported in Razor components. For more information on using ASP.NET Core Identity with Blazor, see Scaffold ASP.NET Core Identity into a server-side Blazor app.
Note
The code examples in this article adopt nullable reference types (NRTs) and .NET compiler null-state static analysis, which are supported in ASP.NET Core in .NET 6 or later. When targeting ASP.NET Core 5.0 or earlier, remove the null type designation (?
) from examples in this article.
Securely maintain sensitive data and credentials
Don't store app secrets, connection strings, credentials, passwords, personal identification numbers (PINs), private .NET/C# code, or private keys/tokens in client-side code, which is always insecure. Client-side Blazor code should access secure services and databases through a secure web API that you control.
In test/staging and production environments, server-side Blazor code and web APIs should use secure authentication flows that avoid maintaining credentials within project code or configuration files. Outside of local development testing, we recommend avoiding the use of environment variables to store sensitive data, as environment variables aren't the most secure approach. For local development testing, the Secret Manager tool is recommended for securing sensitive data. For more information, see the following resources:
- Secure authentication flows (ASP.NET Core documentation)
- Managed identities for Microsoft Azure services (this article)
For client-side and server-side local development and testing, use the Secret Manager tool to secure sensitive credentials.
Managed identities for Microsoft Azure services
For Microsoft Azure services, we recommend using managed identities. Managed identities securely authenticate to Azure services without storing credentials in app code. For more information, see the following resources:
- What are managed identities for Azure resources? (Microsoft Entra documentation)
- Azure services documentation
Antiforgery support
The Blazor template:
- Adds antiforgery services automatically when AddRazorComponents is called in the
Program
file. - Adds Antiforgery Middleware by calling UseAntiforgery in its request processing pipeline in the
Program
file and requires endpoint antiforgery protection to mitigate the threats of Cross-Site Request Forgery (CSRF/XSRF). UseAntiforgery is called after UseHttpsRedirection. A call to UseAntiforgery must be placed after calls, if present, to UseAuthentication and UseAuthorization.
The AntiforgeryToken component renders an antiforgery token as a hidden field, and this component is automatically added to form (EditForm) instances. For more information, see ASP.NET Core Blazor forms overview.
The AntiforgeryStateProvider service provides access to an antiforgery token associated with the current session. Inject the service and call its GetAntiforgeryToken() method to obtain the current AntiforgeryRequestToken. For more information, see Call a web API from an ASP.NET Core Blazor app.
Blazor stores request tokens in component state, which guarantees that antiforgery tokens are available to interactive components, even when they don't have access to the request.
Note
Antiforgery mitigation is only required when submitting form data to the server encoded as application/x-www-form-urlencoded
, multipart/form-data
, or text/plain
since these are the only valid form enctypes.
For more information, see the following resources:
- Prevent Cross-Site Request Forgery (XSRF/CSRF) attacks in ASP.NET Core: This article is the primary ASP.NET Core article on the subject, which applies to server-side Blazor Server, the server project of Blazor Web Apps, and Blazor integration with MVC/Razor Pages.
- ASP.NET Core Blazor forms overview: The Antiforgery support section of the article pertains to Blazor forms antiforgery support.
Authentication
Blazor uses the existing ASP.NET Core authentication mechanisms to establish the user's identity. The exact mechanism depends on how the Blazor app is hosted, server-side or client-side.
Server-side Blazor authentication
Interactively-rendered server-side Blazor operates over a SignalR connection with the client. Authentication in SignalR-based apps is handled when the connection is established. Authentication can be based on a cookie or some other bearer token, but authentication is managed via the SignalR hub and entirely within the circuit.
The built-in or custom AuthenticationStateProvider service obtains authentication state data from ASP.NET Core's HttpContext.User. This is how authentication state integrates with existing ASP.NET Core authentication mechanisms.
For more information on server-side authentication, see Secure ASP.NET Core server-side Blazor apps.
IHttpContextAccessor
/HttpContext
in Razor components
IHttpContextAccessor must be avoided with interactive rendering because there isn't a valid HttpContext
available.
IHttpContextAccessor can be used for components that are statically rendered on the server. However, we recommend avoiding it if possible.
HttpContext can be used as a cascading parameter only in statically-rendered root components for general tasks, such as inspecting and modifying headers or other properties in the App
component (Components/App.razor
). The value is always null
for interactive rendering.
[CascadingParameter]
public HttpContext? HttpContext { get; set; }
For scenarios where the HttpContext is required in interactive components, we recommend flowing the data via persistent component state from the server. For more information, see Server-side ASP.NET Core Blazor additional security scenarios.
Don't use IHttpContextAccessor/HttpContext directly or indirectly in the Razor components of server-side Blazor apps. Blazor apps run outside of the ASP.NET Core pipeline context. The HttpContext isn't guaranteed to be available within the IHttpContextAccessor, and HttpContext isn't guaranteed to hold the context that started the Blazor app.
The recommended approach for passing request state to the Blazor app is through root component parameters during the app's initial rendering. Alternatively, the app can copy the data into a scoped service in the root component's initialization lifecycle event for use across the app. For more information, see Server-side ASP.NET Core Blazor additional security scenarios.
A critical aspect of server-side Blazor security is that the user attached to a given circuit might become updated at some point after Blazor's SignalR circuit is established but the IHttpContextAccessor isn't updated. For more information on addressing this situation with custom services, see Server-side ASP.NET Core Blazor additional security scenarios.
Shared state
Server-side Blazor apps live in server memory, and multiple app sessions are hosted within the same process. For each app session, Blazor starts a circuit with its own dependency injection container scope, thus scoped services are unique per Blazor session.
Warning
We don't recommend apps on the same server share state using singleton services unless extreme care is taken, as this can introduce security vulnerabilities, such as leaking user state across circuits.
You can use stateful singleton services in Blazor apps if they're specifically designed for it. For example, use of a singleton memory cache is acceptable because a memory cache requires a key to access a given entry. Assuming users don't have control over the cache keys that are used with the cache, state stored in the cache doesn't leak across circuits.
For general guidance on state management, see ASP.NET Core Blazor state management.
Client-side Blazor authentication
In client-side Blazor apps, client-side authentication checks can be bypassed because all client-side code can be modified by users. The same is true for all client-side app technologies, including JavaScript SPA frameworks and native apps for any operating system.
Add the following:
A package reference for the
Microsoft.AspNetCore.Components.Authorization
NuGet package.Note
For guidance on adding packages to .NET apps, see the articles under Install and manage packages at Package consumption workflow (NuGet documentation). Confirm correct package versions at NuGet.org.
The Microsoft.AspNetCore.Components.Authorization namespace to the app's
_Imports.razor
file.
To handle authentication, use the built-in or custom AuthenticationStateProvider service.
For more information on client-side authentication, see Secure ASP.NET Core Blazor WebAssembly.
AuthenticationStateProvider
service
AuthenticationStateProvider is the underlying service used by the AuthorizeView component and cascading authentication services to obtain the authentication state for a user.
AuthenticationStateProvider is the underlying service used by the AuthorizeView component and CascadingAuthenticationState component to obtain the authentication state for a user.
You don't typically use AuthenticationStateProvider directly. Use the AuthorizeView
component or Task<AuthenticationState>
approaches described later in this article. The main drawback to using AuthenticationStateProvider directly is that the component isn't notified automatically if the underlying authentication state data changes.
To implement a custom AuthenticationStateProvider, see ASP.NET Core Blazor authentication state, which includes guidance on implementing user authentication state change notifications.
Obtain a user's claims principal data
The AuthenticationStateProvider service can provide the current user's ClaimsPrincipal data, as shown in the following example.
ClaimsPrincipalData.razor
:
@page "/claims-principal-data"
@using System.Security.Claims
@inject AuthenticationStateProvider AuthenticationStateProvider
<h1>ClaimsPrincipal Data</h1>
<button @onclick="GetClaimsPrincipalData">Get ClaimsPrincipal Data</button>
<p>@authMessage</p>
@if (claims.Any())
{
<ul>
@foreach (var claim in claims)
{
<li>@claim.Type: @claim.Value</li>
}
</ul>
}
<p>@surname</p>
@code {
private string? authMessage;
private string? surname;
private IEnumerable<Claim> claims = Enumerable.Empty<Claim>();
private async Task GetClaimsPrincipalData()
{
var authState = await AuthenticationStateProvider
.GetAuthenticationStateAsync();
var user = authState.User;
if (user.Identity is not null && user.Identity.IsAuthenticated)
{
authMessage = $"{user.Identity.Name} is authenticated.";
claims = user.Claims;
surname = user.FindFirst(c => c.Type == ClaimTypes.Surname)?.Value;
}
else
{
authMessage = "The user is NOT authenticated.";
}
}
}
In the preceding example:
- ClaimsPrincipal.Claims returns the user's claims (
claims
) for display in the UI. - The line that obtains the user's surname (
surname
) calls ClaimsPrincipal.FindAll with a predicate to filter the user's claims.
@page "/claims-principal-data"
@using System.Security.Claims
@inject AuthenticationStateProvider AuthenticationStateProvider
<h1>ClaimsPrincipal Data</h1>
<button @onclick="GetClaimsPrincipalData">Get ClaimsPrincipal Data</button>
<p>@authMessage</p>
@if (claims.Any())
{
<ul>
@foreach (var claim in claims)
{
<li>@claim.Type: @claim.Value</li>
}
</ul>
}
<p>@surname</p>
@code {
private string? authMessage;
private string? surname;
private IEnumerable<Claim> claims = Enumerable.Empty<Claim>();
private async Task GetClaimsPrincipalData()
{
var authState = await AuthenticationStateProvider
.GetAuthenticationStateAsync();
var user = authState.User;
if (user.Identity is not null && user.Identity.IsAuthenticated)
{
authMessage = $"{user.Identity.Name} is authenticated.";
claims = user.Claims;
surname = user.FindFirst(c => c.Type == ClaimTypes.Surname)?.Value;
}
else
{
authMessage = "The user is NOT authenticated.";
}
}
}
If user.Identity.IsAuthenticated
is true
and because the user is a ClaimsPrincipal, claims can be enumerated and membership in roles evaluated.
For more information on dependency injection (DI) and services, see ASP.NET Core Blazor dependency injection and Dependency injection in ASP.NET Core. For information on how to implement a custom AuthenticationStateProvider, see ASP.NET Core Blazor authentication state.
Expose the authentication state as a cascading parameter
If authentication state data is required for procedural logic, such as when performing an action triggered by the user, obtain the authentication state data by defining a cascading parameter of type Task<
AuthenticationState>
, as the following example demonstrates.
CascadeAuthState.razor
:
@page "/cascade-auth-state"
<h1>Cascade Auth State</h1>
<p>@authMessage</p>
@code {
private string authMessage = "The user is NOT authenticated.";
[CascadingParameter]
private Task<AuthenticationState>? authenticationState { get; set; }
protected override async Task OnInitializedAsync()
{
if (authenticationState is not null)
{
var authState = await authenticationState;
var user = authState?.User;
if (user?.Identity is not null && user.Identity.IsAuthenticated)
{
authMessage = $"{user.Identity.Name} is authenticated.";
}
}
}
}
@page "/cascade-auth-state"
<h1>Cascade Auth State</h1>
<p>@authMessage</p>
@code {
private string authMessage = "The user is NOT authenticated.";
[CascadingParameter]
private Task<AuthenticationState>? authenticationState { get; set; }
protected override async Task OnInitializedAsync()
{
if (authenticationState is not null)
{
var authState = await authenticationState;
var user = authState?.User;
if (user?.Identity is not null && user.Identity.IsAuthenticated)
{
authMessage = $"{user.Identity.Name} is authenticated.";
}
}
}
}
If user.Identity.IsAuthenticated
is true
, claims can be enumerated and membership in roles evaluated.
Set up the Task<
AuthenticationState>
cascading parameter using the AuthorizeRouteView and cascading authentication state services.
When you create a Blazor app from one of the Blazor project templates with authentication enabled, the app includes the AuthorizeRouteView and the call to AddCascadingAuthenticationState shown in the following example. A client-side Blazor app includes the required service registrations as well. Additional information is presented in the Customize unauthorized content with the Router
component section.
<Router ...>
<Found ...>
<AuthorizeRouteView RouteData="routeData"
DefaultLayout="typeof(Layout.MainLayout)" />
...
</Found>
</Router>
In the Program
file, register cascading authentication state services:
builder.Services.AddCascadingAuthenticationState();
Set up the Task<
AuthenticationState>
cascading parameter using the AuthorizeRouteView and CascadingAuthenticationState components.
When you create a Blazor app from one of the Blazor project templates with authentication enabled, the app includes the AuthorizeRouteView and CascadingAuthenticationState components shown in the following example. A client-side Blazor app includes the required service registrations as well. Additional information is presented in the Customize unauthorized content with the Router
component section.
<CascadingAuthenticationState>
<Router ...>
<Found ...>
<AuthorizeRouteView RouteData="routeData"
DefaultLayout="typeof(MainLayout)" />
...
</Found>
</Router>
</CascadingAuthenticationState>
Note
With the release of ASP.NET Core 5.0.1 and for any additional 5.x releases, the Router
component includes the PreferExactMatches
parameter set to @true
. For more information, see Migrate from ASP.NET Core 3.1 to 5.0.
In a client-side Blazor app, add authorization services to the Program
file:
builder.Services.AddAuthorizationCore();
In a client-side Blazor app, add options and authorization services to the Program
file:
builder.Services.AddOptions();
builder.Services.AddAuthorizationCore();
In a server-side Blazor app, services for options and authorization are already present, so no further steps are required.
Authorization
After a user is authenticated, authorization rules are applied to control what the user can do.
Access is typically granted or denied based on whether:
- A user is authenticated (signed in).
- A user is in a role.
- A user has a claim.
- A policy is satisfied.
Each of these concepts is the same as in an ASP.NET Core MVC or Razor Pages app. For more information on ASP.NET Core security, see the articles under ASP.NET Core Security and Identity.
AuthorizeView
component
The AuthorizeView component selectively displays UI content depending on whether the user is authorized. This approach is useful when you only need to display data for the user and don't need to use the user's identity in procedural logic.
The component exposes a context
variable of type AuthenticationState (@context
in Razor syntax), which you can use to access information about the signed-in user:
<AuthorizeView>
<p>Hello, @context.User.Identity?.Name!</p>
</AuthorizeView>
You can also supply different content for display if the user isn't authorized with a combination of the Authorized and NotAuthorized parameters:
<AuthorizeView>
<Authorized>
<p>Hello, @context.User.Identity?.Name!</p>
<p><button @onclick="HandleClick">Authorized Only Button</button></p>
</Authorized>
<NotAuthorized>
<p>You're not authorized.</p>
</NotAuthorized>
</AuthorizeView>
@code {
private void HandleClick() { ... }
}
Although the AuthorizeView component controls the visibility of elements based on the user’s authorization status, it doesn't enforce security on the event handler itself. In the preceding example, the HandleClick
method is only associated with a button visible to authorized users, but nothing prevents invoking this method from other places. To ensure method-level security, implement additional authorization logic within the handler itself or in the relevant API.
Razor components of Blazor Web Apps never display <NotAuthorized>
content when authorization fails server-side during static server-side rendering (static SSR). The server-side ASP.NET Core pipeline processes authorization on the server. Use server-side techniques to handle unauthorized requests. For more information, see ASP.NET Core Blazor render modes.
Warning
Client-side markup and methods associated with an AuthorizeView are only protected from view and execution in the rendered UI in client-side Blazor apps. In order to protect authorized content and secure methods in client-side Blazor, the content is usually supplied by a secure, authorized web API call to a server API and never stored in the app. For more information, see Call a web API from an ASP.NET Core Blazor app and ASP.NET Core Blazor WebAssembly additional security scenarios.
The content of Authorized and NotAuthorized can include arbitrary items, such as other interactive components.
Authorization conditions, such as roles or policies that control UI options or access, are covered in the Authorization section.
If authorization conditions aren't specified, AuthorizeView uses a default policy:
- Authenticated (signed-in) users are authorized.
- Unauthenticated (signed-out) users are unauthorized.
The AuthorizeView component can be used in the NavMenu
component (Shared/NavMenu.razor
) to display a NavLink
component (NavLink), but note that this approach only removes the list item from the rendered output. It doesn't prevent the user from navigating to the component. Implement authorization separately in the destination component.
Role-based and policy-based authorization
The AuthorizeView component supports role-based or policy-based authorization.
For role-based authorization, use the Roles parameter. In the following example, the user must have a role claim for either the Admin
or Superuser
roles:
<AuthorizeView Roles="Admin, Superuser">
<p>You have an 'Admin' or 'Superuser' role claim.</p>
</AuthorizeView>
To require a user have both Admin
and Superuser
role claims, nest AuthorizeView components:
<AuthorizeView Roles="Admin">
<p>User: @context.User</p>
<p>You have the 'Admin' role claim.</p>
<AuthorizeView Roles="Superuser" Context="innerContext">
<p>User: @innerContext.User</p>
<p>You have both 'Admin' and 'Superuser' role claims.</p>
</AuthorizeView>
</AuthorizeView>
The preceding code establishes a Context
for the inner AuthorizeView component to prevent an AuthenticationState context collision. The AuthenticationState context is accessed in the outer AuthorizeView with the standard approach for accessing the context (@context.User
). The context is accessed in the inner AuthorizeView with the named innerContext
context (@innerContext.User
).
For more information, including configuration guidance, see Role-based authorization in ASP.NET Core.
For policy-based authorization, use the Policy parameter with a single policy name:
<AuthorizeView Policy="Over21">
<p>You satisfy the 'Over21' policy.</p>
</AuthorizeView>
To handle the case where the user should satisfy one of several policies, create a policy that confirms that the user satisfies other policies.
To handle the case where the user must satisfy several policies simultaneously, take either of the following approaches:
Create a policy for AuthorizeView that confirms that the user satisfies several other policies.
Nest the policies in multiple AuthorizeView components:
<AuthorizeView Policy="Over21"> <AuthorizeView Policy="LivesInCalifornia"> <p>You satisfy the 'Over21' and 'LivesInCalifornia' policies.</p> </AuthorizeView> </AuthorizeView>
Claims-based authorization is a special case of policy-based authorization. For example, you can define a policy that requires users to have a certain claim. For more information, see Policy-based authorization in ASP.NET Core.
If neither Roles nor Policy is specified, AuthorizeView uses the default policy:
- Authenticated (signed-in) users are authorized.
- Unauthenticated (signed-out) users are unauthorized.
Because .NET string comparisons are case-sensitive, matching role and policy names is also case-sensitive. For example, Admin
(uppercase A
) is not treated as the same role as admin
(lowercase a
).
Pascal case is typically used for role and policy names (for example, BillingAdministrator
), but the use of Pascal case isn't a strict requirement. Different casing schemes, such as camel case, kebab case, and snake case, are permitted. Using spaces in role and policy names is unusual but permitted by the framework. For example, billing administrator
is an unusual role or policy name format in .NET apps, but it's a valid role or policy name.
Content displayed during asynchronous authentication
Blazor allows for authentication state to be determined asynchronously. The primary scenario for this approach is in client-side Blazor apps that make a request to an external endpoint for authentication.
While authentication is in progress, AuthorizeView displays no content. To display content while authentication occurs, assign content to the Authorizing parameter:
<AuthorizeView>
<Authorized>
<p>Hello, @context.User.Identity?.Name!</p>
</Authorized>
<Authorizing>
<p>You can only see this content while authentication is in progress.</p>
</Authorizing>
</AuthorizeView>
This approach isn't normally applicable to server-side Blazor apps. Server-side Blazor apps know the authentication state as soon as the state is established. Authorizing content can be provided in an app's AuthorizeView component, but the content is never displayed.
[Authorize]
attribute
The [Authorize]
attribute is available in Razor components:
@page "/"
@attribute [Authorize]
You can only see this if you're signed in.
Important
Only use [Authorize]
on @page
components reached via the Blazor router. Authorization is only performed as an aspect of routing and not for child components rendered within a page. To authorize the display of specific parts within a page, use AuthorizeView instead.
The [Authorize]
attribute also supports role-based or policy-based authorization. For role-based authorization, use the Roles parameter:
@page "/"
@attribute [Authorize(Roles = "Admin, Superuser")]
<p>You can only see this if you're in the 'Admin' or 'Superuser' role.</p>
For policy-based authorization, use the Policy parameter:
@page "/"
@attribute [Authorize(Policy = "Over21")]
<p>You can only see this if you satisfy the 'Over21' policy.</p>
If neither Roles nor Policy is specified, [Authorize]
uses the default policy:
- Authenticated (signed-in) users are authorized.
- Unauthenticated (signed-out) users are unauthorized.
When the user isn't authorized and if the app doesn't customize unauthorized content with the Router
component, the framework automatically displays the following fallback message:
Not authorized.
Resource authorization
To authorize users for resources, pass the request's route data to the Resource parameter of AuthorizeRouteView.
In the Router.Found content for a requested route:
<AuthorizeRouteView Resource="routeData" RouteData="routeData"
DefaultLayout="typeof(MainLayout)" />
For more information on how authorization state data is passed and used in procedural logic, see the Expose the authentication state as a cascading parameter section.
When the AuthorizeRouteView receives the route data for the resource, authorization policies have access to RouteData.PageType and RouteData.RouteValues that permit custom logic to make authorization decisions.
In the following example, an EditUser
policy is created in AuthorizationOptions for the app's authorization service configuration (AddAuthorizationCore) with the following logic:
- Determine if a route value exists with a key of
id
. If the key exists, the route value is stored invalue
. - In a variable named
id
, storevalue
as a string or set an empty string value (string.Empty
). - If
id
isn't an empty string, assert that the policy is satisfied (returntrue
) if the string's value starts withEMP
. Otherwise, assert that the policy fails (returnfalse
).
In the Program
file:
Add namespaces for Microsoft.AspNetCore.Components and System.Linq:
using Microsoft.AspNetCore.Components; using System.Linq;
Add the policy:
options.AddPolicy("EditUser", policy => policy.RequireAssertion(context => { if (context.Resource is RouteData rd) { var routeValue = rd.RouteValues.TryGetValue("id", out var value); var id = Convert.ToString(value, System.Globalization.CultureInfo.InvariantCulture) ?? string.Empty; if (!string.IsNullOrEmpty(id)) { return id.StartsWith("EMP", StringComparison.InvariantCulture); } } return false; }) );
The preceding example is an oversimplified authorization policy, merely used to demonstrate the concept with a working example. For more information on creating and configuring authorization policies, see Policy-based authorization in ASP.NET Core.
In the following EditUser
component, the resource at /users/{id}/edit
has a route parameter for the user's identifier ({id}
). The component uses the preceding EditUser
authorization policy to determine if the route value for id
starts with EMP
. If id
starts with EMP
, the policy succeeds and access to the component is authorized. If id
starts with a value other than EMP
or if id
is an empty string, the policy fails, and the component doesn't load.
EditUser.razor
:
@page "/users/{id}/edit"
@using Microsoft.AspNetCore.Authorization
@attribute [Authorize(Policy = "EditUser")]
<h1>Edit User</h1>
<p>The "EditUser" policy is satisfied! <code>Id</code> starts with 'EMP'.</p>
@code {
[Parameter]
public string? Id { get; set; }
}
@page "/users/{id}/edit"
@using Microsoft.AspNetCore.Authorization
@attribute [Authorize(Policy = "EditUser")]
<h1>Edit User</h1>
<p>The "EditUser" policy is satisfied! <code>Id</code> starts with 'EMP'.</p>
@code {
[Parameter]
public string? Id { get; set; }
}
Customize unauthorized content with the Router
component
The Router component, in conjunction with the AuthorizeRouteView component, allows the app to specify custom content if:
- The user fails an
[Authorize]
condition applied to the component. The markup of the<NotAuthorized>
element is displayed. The[Authorize]
attribute is covered in the[Authorize]
attribute section. - Asynchronous authorization is in progress, which usually means that the process of authenticating the user is in progress. The markup of the
<Authorizing>
element is displayed.
Important
Blazor router features that display <NotAuthorized>
and <NotFound>
content aren't operational during static server-side rendering (static SSR) because request processing is entirely handled by ASP.NET Core middleware pipeline request processing and Razor components aren't rendered at all for unauthorized or bad requests. Use server-side techniques to handle unauthorized and bad requests during static SSR. For more information, see ASP.NET Core Blazor render modes.
<Router ...>
<Found ...>
<AuthorizeRouteView ...>
<NotAuthorized>
...
</NotAuthorized>
<Authorizing>
...
</Authorizing>
</AuthorizeRouteView>
</Found>
</Router>
The content of Authorized and NotAuthorized can include arbitrary items, such as other interactive components.
Note
The preceding requires cascading authentication state services registration in the app's Program
file:
builder.Services.AddCascadingAuthenticationState();
<CascadingAuthenticationState>
<Router ...>
<Found ...>
<AuthorizeRouteView ...>
<NotAuthorized>
...
</NotAuthorized>
<Authorizing>
...
</Authorizing>
</AuthorizeRouteView>
</Found>
</Router>
</CascadingAuthenticationState>
The content of NotFound, Authorized, and NotAuthorized can include arbitrary items, such as other interactive components.
If NotAuthorized content isn't specified, the AuthorizeRouteView uses the following fallback message:
Not authorized.
An app created from the Blazor WebAssembly project template with authentication enabled includes a RedirectToLogin
component, which is positioned in the <NotAuthorized>
content of the Router component. When a user isn't authenticated (context.User.Identity?.IsAuthenticated != true
), the RedirectToLogin
component redirects the browser to the authentication/login
endpoint for authentication. The user is returned to the requested URL after authenticating with the identity provider.
Procedural logic
If the app is required to check authorization rules as part of procedural logic, use a cascaded parameter of type Task<
AuthenticationState>
to obtain the user's ClaimsPrincipal. Task<
AuthenticationState>
can be combined with other services, such as IAuthorizationService
, to evaluate policies.
In the following example:
- The
user.Identity.IsAuthenticated
executes code for authenticated (signed-in) users. - The
user.IsInRole("admin")
executes code for users in the 'Admin' role. - The
(await AuthorizationService.AuthorizeAsync(user, "content-editor")).Succeeded
executes code for users satisfying the 'content-editor' policy.
A server-side Blazor app includes the appropriate namespaces when created from the project template. In a client-side Blazor app, confirm the presence of the Microsoft.AspNetCore.Authorization and Microsoft.AspNetCore.Components.Authorization namespaces either in the component or in the app's _Imports.razor
file:
@using Microsoft.AspNetCore.Authorization
@using Microsoft.AspNetCore.Components.Authorization
ProceduralLogic.razor
:
@page "/procedural-logic"
@inject IAuthorizationService AuthorizationService
<h1>Procedural Logic Example</h1>
<button @onclick="@DoSomething">Do something important</button>
@code {
[CascadingParameter]
private Task<AuthenticationState>? authenticationState { get; set; }
private async Task DoSomething()
{
if (authenticationState is not null)
{
var authState = await authenticationState;
var user = authState?.User;
if (user is not null)
{
if (user.Identity is not null && user.Identity.IsAuthenticated)
{
// ...
}
if (user.IsInRole("Admin"))
{
// ...
}
if ((await AuthorizationService.AuthorizeAsync(user, "content-editor"))
.Succeeded)
{
// ...
}
}
}
}
}
@page "/procedural-logic"
@inject IAuthorizationService AuthorizationService
<h1>Procedural Logic Example</h1>
<button @onclick="@DoSomething">Do something important</button>
@code {
[CascadingParameter]
private Task<AuthenticationState>? authenticationState { get; set; }
private async Task DoSomething()
{
if (authenticationState is not null)
{
var authState = await authenticationState;
var user = authState?.User;
if (user is not null)
{
if (user.Identity is not null && user.Identity.IsAuthenticated)
{
// ...
}
if (user.IsInRole("Admin"))
{
// ...
}
if ((await AuthorizationService.AuthorizeAsync(user, "content-editor"))
.Succeeded)
{
// ...
}
}
}
}
}
Troubleshoot errors
Common errors:
Authorization requires a cascading parameter of type
Task<AuthenticationState>
. Consider usingCascadingAuthenticationState
to supply this.null
value is received forauthenticationStateTask
It's likely that the project wasn't created using a server-side Blazor template with authentication enabled.
In .NET 7 or earlier, wrap a <CascadingAuthenticationState>
around some part of the UI tree, for example around the Blazor router:
<CascadingAuthenticationState>
<Router ...>
...
</Router>
</CascadingAuthenticationState>
In .NET 8 or later, don't use the CascadingAuthenticationState component:
- <CascadingAuthenticationState>
<Router ...>
...
</Router>
- </CascadingAuthenticationState>
Instead, add cascading authentication state services to the service collection in the Program
file:
builder.Services.AddCascadingAuthenticationState();
The CascadingAuthenticationState component (.NET 7 or earlier) or services provided by AddCascadingAuthenticationState (.NET 8 or later) supplies the Task<
AuthenticationState>
cascading parameter, which in turn it receives from the underlying AuthenticationStateProvider dependency injection service.
Personally Identifiable Information (PII)
Microsoft uses the GDPR definition for 'personal data' (GDPR 4.1) when documentation discusses Personally Identifiable Information (PII).
PII refers any information relating to an identified or identifiable natural person. An identifiable natural person is one who can be identified, directly or indirectly, with any of the following:
- Name
- Identification number
- Location coordinates
- Online identifier
- Other specific factors
- Physical
- Physiological
- Genetic
- Mental (psychological)
- Economic
- Cultural
- Social identity
Additional resources
- Microsoft identity platform documentation
- ASP.NET Core security topics
- Configure Windows Authentication in ASP.NET Core
- Build a custom version of the Authentication.MSAL JavaScript library
- Awesome Blazor: Authentication community sample links
- ASP.NET Core Blazor Hybrid authentication and authorization
- Microsoft identity platform documentation
- ASP.NET Core security topics
- Configure Windows Authentication in ASP.NET Core
- Build a custom version of the Authentication.MSAL JavaScript library
- Awesome Blazor: Authentication community sample links
ASP.NET Core