Authorization

Authorization is used to check if a user is allowed to perform some specific operations in the application.

ABP extends ASP.NET Core Authorization by adding permissions as auto policies and allowing authorization system to be usable in the application services too.

So, all the ASP.NET Core authorization features and the documentation are valid in an ABP based application. This document focuses on the features that added on top of ASP.NET Core authorization features.

Authorize Attribute

ASP.NET Core defines the Authorize attribute that can be used for an action, a controller or a page. ABP allows you to use the same attribute for an application service too.

Example:

using System;
using System.Collections.Generic;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Authorization;
using Volo.Abp.Application.Services;

namespace Acme.BookStore
{
    [Authorize]
    public class AuthorAppService : ApplicationService, IAuthorAppService
    {
        public Task<List<AuthorDto>> GetListAsync()
        {
            ...
        }

        [AllowAnonymous]
        public Task<AuthorDto> GetAsync(Guid id)
        {
            ...
        }

        [Authorize("BookStore_Author_Create")]
        public Task CreateAsync(CreateAuthorDto input)
        {
            ...
        }
    }
}

• Authorize attribute forces the user to login into the application in order to use the AuthorAppService methods. So, GetListAsync method is only available to the authenticated users.
• AllowAnonymous suppresses the authentication. So, GetAsync method is available to everyone including unauthorized users.
• [Authorize("BookStore_Author_Create")] defines a policy (see policy based authorization) that is checked to authorize the current user.

"BookStore_Author_Create" is an arbitrary policy name. If you declare an attribute like that, ASP.NET Core authorization system expects a policy to be defined before.

You can, of course, implement your policies as stated in the ASP.NET Core documentation. But for simple true/false conditions like a policy was granted to a user or not, ABP defines the permission system which will be explained in the next section.

Permission System

A permission is a simple policy that is granted or prohibited for a particular user, role or client.

Defining Permissions

To define permissions, create a class inheriting from the PermissionDefinitionProvider as shown below:

using Volo.Abp.Authorization.Permissions;

namespace Acme.BookStore.Permissions
{
    public class BookStorePermissionDefinitionProvider : PermissionDefinitionProvider
    {
        public override void Define(IPermissionDefinitionContext context)
        {
            var myGroup = context.AddGroup("BookStore");

            myGroup.AddPermission("BookStore_Author_Create");
        }
    }
}

ABP automatically discovers this class. No additional configuration required!

You typically define this class inside the Application.Contracts project of your application. The startup template already comes with an empty class named YourProjectNamePermissionDefinitionProvider that you can start with.

In the Define method, you first need to add a permission group or get an existing group then add permissions to this group.

When you define a permission, it becomes usable in the ASP.NET Core authorization system as a policy name. It also becomes visible in the UI. See permissions dialog for a role:

• The "BookStore" group is shown as a new tab on the left side.
• "BookStore_Author_Create" on the right side is the permission name. You can grant or prohibit it for the role.

When you save the dialog, it is saved to the database and used in the authorization system.

The screen above is available when you have installed the identity module, which is basically used for user and role management. Startup templates come with the identity module pre-installed.

Localizing the Permission Name

"BookStore_Author_Create" is not a good permission name for the UI. Fortunately, AddPermission and AddGroup methods can take LocalizableString as second parameters:

var myGroup = context.AddGroup(
    "BookStore",
    LocalizableString.Create<BookStoreResource>("BookStore")
);

myGroup.AddPermission(
    "BookStore_Author_Create",
    LocalizableString.Create<BookStoreResource>("Permission:BookStore_Author_Create")
);

Then you can define texts for "BookStore" and "Permission:BookStore_Author_Create" keys in the localization file:

"BookStore": "Book Store",
"Permission:BookStore_Author_Create": "Creating a new author"

For more information, see the localization document on the localization system.

The localized UI will be as seen below:

Multi-Tenancy

ABP supports multi-tenancy as a first class citizen. You can define multi-tenancy side option while defining a new permission. It gets one of the three values defined below:

• Host: The permission is available only for the host side.
• Tenant: The permission is available only for the tenant side.
• Both (default): The permission is available both for tenant and host sides.

If your application is not multi-tenant, you can ignore this option.

To set the multi-tenancy side option, pass to the third parameter of the AddPermission method:

myGroup.AddPermission(
    "BookStore_Author_Create",
    LocalizableString.Create<BookStoreResource>("Permission:BookStore_Author_Create"),
    multiTenancySide: MultiTenancySides.Tenant //set multi-tenancy side!
);

Enable/Disable Permissions

A permission is enabled by default. It is possible to disable a permission. A disabled permission will be prohibited for everyone. You can still check for the permission, but it will always return prohibited.

Example definition:

myGroup.AddPermission("Author_Management", isEnabled: false);

You normally don't need to define a disabled permission (unless you temporary want disable a feature of your application). However, you may want to disable a permission defined in a depended module. In this way you can disable the related application functionality. See the "Changing Permission Definitions of a Depended Module" section below for an example usage.

Note: Checking an undefined permission will throw an exception while a disabled permission check simply returns prohibited (false).

Child Permissions

A permission may have child permissions. It is especially useful when you want to create a hierarchical permission tree where a permission may have additional sub permissions which are available only if the parent permission has been granted.

Example definition:

var authorManagement = myGroup.AddPermission("Author_Management");
authorManagement.AddChild("Author_Management_Create_Books");
authorManagement.AddChild("Author_Management_Edit_Books");
authorManagement.AddChild("Author_Management_Delete_Books");

The result on the UI is shown below (you probably want to localize permissions for your application):

For the example code, it is assumed that a role/user with "Author_Management" permission granted may have additional permissions. Then a typical application service that checks permissions can be defined as shown below:

[Authorize("Author_Management")]
public class AuthorAppService : ApplicationService, IAuthorAppService
{
    public Task<List<AuthorDto>> GetListAsync()
    {
        ...
    }

    public Task<AuthorDto> GetAsync(Guid id)
    {
        ...
    }

    [Authorize("Author_Management_Create_Books")]
    public Task CreateAsync(CreateAuthorDto input)
    {
        ...
    }

    [Authorize("Author_Management_Edit_Books")]
    public Task UpdateAsync(CreateAuthorDto input)
    {
        ...
    }

    [Authorize("Author_Management_Delete_Books")]
    public Task DeleteAsync(CreateAuthorDto input)
    {
        ...
    }
}

• GetListAsync and GetAsync will be available to users if they have Author_Management permission is granted.
• Other methods require additional permissions.

Overriding a Permission by a Custom Policy

If you define and register a policy to the ASP.NET Core authorization system with the same name of a permission, your policy will override the existing permission. This is a powerful way to extend the authorization for a pre-built module that you are using in your application.

See policy based authorization document to learn how to define a custom policy.

Changing Permission Definitions of a Depended Module

A class deriving from the PermissionDefinitionProvider (just like the example above) can also get existing permission definitions (defined by the depended modules) and change their definitions.

Example:

context
    .GetPermissionOrNull(IdentityPermissions.Roles.Delete)
    .IsEnabled = false;

When you write this code inside your permission definition provider, it finds the "role deletion" permission of the Identity Module and disabled the permission, so no one can delete a role on the application.

Tip: It is better to check the value returned by the GetPermissionOrNull method since it may return null if the given permission was not defined.

IAuthorizationService

ASP.NET Core provides the IAuthorizationService that can be used to check for authorization. Once you inject, you can use it in your code to conditionally control the authorization.

Example:

public async Task CreateAsync(CreateAuthorDto input)
{
    var result = await AuthorizationService
        .AuthorizeAsync("Author_Management_Create_Books");
    if (result.Succeeded == false)
    {
        //throw exception
        throw new AbpAuthorizationException("...");
    }

    //continue to the normal flow...
}

AuthorizationService is available as a property when you derive from ABP's ApplicationService base class. Since it is widely used in application services, ApplicationService pre-injects it for you. Otherwise, you can directly inject it into your class.

Since this is a typical code block, ABP provides extension methods to simplify it.

Example:

public async Task CreateAsync(CreateAuthorDto input)
{
    await AuthorizationService.CheckAsync("Author_Management_Create_Books");

    //continue to the normal flow...
}

CheckAsync extension method throws AbpAuthorizationException if the current user/client is not granted for the given permission. There is also IsGrantedAsync extension method that returns true or false.

IAuthorizationService has some overloads for the AuthorizeAsync method. These are explained in the ASP.NET Core authorization documentation.

Tip: Prefer to use the Authorize attribute wherever possible, since it is declarative & simple. Use IAuthorizationService if you need to conditionally check a permission and run a business code based on the permission check.

Check a Permission in JavaScript

See the following documents to learn how to re-use the authorization system on the client side:

• ASP.NET Core MVC / Razor Pages UI: Authorization
• Angular UI Authorization
• Blazor UI Authorization

Permission Management

Permission management is normally done by an admin user using the permission management modal:

If you need to manage permissions by code, inject the IPermissionManager and use as shown below:

public class MyService : ITransientDependency
{
    private readonly IPermissionManager _permissionManager;

    public MyService(IPermissionManager permissionManager)
    {
        _permissionManager = permissionManager;
    }

    public async Task GrantPermissionForUserAsync(Guid userId, string permissionName)
    {
        await _permissionManager.SetForUserAsync(userId, permissionName, true);
    }

    public async Task ProhibitPermissionForUserAsync(Guid userId, string permissionName)
    {
        await _permissionManager.SetForUserAsync(userId, permissionName, false);
    }
}

SetForUserAsync sets the value (true/false) for a permission of a user. There are more extension methods like SetForRoleAsync and SetForClientAsync.

IPermissionManager is defined by the permission management module. See the permission management module documentation for more information.

Advanced Topics

Permission Value Providers

Permission checking system is extensible. Any class derived from PermissionValueProvider (or implements IPermissionValueProvider) can contribute to the permission check. There are three pre-defined value providers:

• UserPermissionValueProvider checks if the current user is granted for the given permission. It gets user id from the current claims. User claim name is defined with the AbpClaimTypes.UserId static property.
• RolePermissionValueProvider checks if any of the roles of the current user is granted for the given permission. It gets role names from the current claims. Role claims name is defined with the AbpClaimTypes.Role static property.
• ClientPermissionValueProvider checks if the current client is granted for the given permission. This is especially useful on a machine to machine interaction where there is no current user. It gets the client id from the current claims. Client claim name is defined with the AbpClaimTypes.ClientId static property.

You can extend the permission checking system by defining your own permission value provider.

Example:

public class SystemAdminPermissionValueProvider : PermissionValueProvider
{
    public SystemAdminPermissionValueProvider(IPermissionStore permissionStore)
        : base(permissionStore)
    {
    }

    public override string Name => "SystemAdmin";

    public async override Task<PermissionGrantResult>
           CheckAsync(PermissionValueCheckContext context)
    {
        if (context.Principal?.FindFirst("User_Type")?.Value == "SystemAdmin")
        {
            return PermissionGrantResult.Granted;
        }

        return PermissionGrantResult.Undefined;
    }
}

This provider allows for all permissions to a user with a User_Type claim that has SystemAdmin value. It is common to use current claims and IPermissionStore in a permission value provider.

A permission value provider should return one of the following values from the CheckAsync method:

• PermissionGrantResult.Granted is returned to grant the user for the permission. If any of the providers return Granted, the result will be Granted, if no other provider returns Prohibited.
• PermissionGrantResult.Prohibited is returned to prohibit the user for the permission. If any of the providers return Prohibited, the result will always be Prohibited. Doesn't matter what other providers return.
• PermissionGrantResult.Undefined is returned if this value provider could not decide about the permission value. Return this to let other providers check the permission.

Once a provider is defined, it should be added to the AbpPermissionOptions as shown below:

Configure<AbpPermissionOptions>(options =>
{
    options.ValueProviders.Add<SystemAdminPermissionValueProvider>();
});

Permission Store

IPermissionStore is the only interface that needs to be implemented to read the value of permissions from a persistence source, generally a database system. The Permission Management module implements it and pre-installed in the application startup template. See the permission management module documentation for more information

AlwaysAllowAuthorizationService

AlwaysAllowAuthorizationService is a class that is used to bypass the authorization service. It is generally used in integration tests where you may want to disable the authorization system.

Use IServiceCollection.AddAlwaysAllowAuthorization() extension method to register the AlwaysAllowAuthorizationService to the dependency injection system:

public override void ConfigureServices(ServiceConfigurationContext context)
{
    context.Services.AddAlwaysAllowAuthorization();
}

This is already done for the startup template integration tests.

See Also

• Permission Management Module
• ASP.NET Core MVC / Razor Pages JavaScript Auth API
• Permission Management in Angular UI