一、前言

回顧：基于.NetCore3.1系列 —— 認證授權方案之授權揭秘 (上篇)

在上一篇中，主要講解了授權在配置方面的原始碼，從添加授權配置開始，我們引入了需要的授權配置選項，而不同的授權要求構建不同的策略方式，從而實作一種自己滿意的授權需求配置要求，

在這一節中，繼續上一篇的內容往下深入了解授權內部機制的奧秘以及是如何實作執行授權流程的，

二、說明

在上一篇中，我們通過定義授權策略，查看原始碼發現，在對授權配置AuthorizationOptions之后，授權系統通過DI的方式注冊了幾個核心的默認實作，

之前我們進行對步驟一的授權有了大概了解，所以下面我們將對步驟二進行的注冊物件進行說明，

三、開始

3.1 IAuthorizationService

授權服務介面，用來確定授權是否成功的主要服務，介面的定義為

    public interface IAuthorizationService
    {
            Task<AuthorizationResult> AuthorizeAsync(ClaimsPrincipal user, object resource, IEnumerable<IAuthorizationRequirement> requirements);
            Task<AuthorizationResult> AuthorizeAsync(ClaimsPrincipal user, object resource, string policyName);
    }

兩個介面的引數不同之處在于IAuthorizationRequirement和policyName,分別是指定資源的一組特定要求和指定的授權名稱，

同時asp.net core還為IAuthorizationService 介面拓展了幾個方法：

    public static class AuthorizationServiceExtensions
    {
        public static Task<AuthorizationResult> AuthorizeAsync(this IAuthorizationService service, ClaimsPrincipal user, object resource, IAuthorizationRequirement requirement)
        {
            if (service == null)
            {
                throw new ArgumentNullException(nameof(service));
            }

            if (requirement == null)
            {
                throw new ArgumentNullException(nameof(requirement));
            }

            return service.AuthorizeAsync(user, resource, new IAuthorizationRequirement[] { requirement });
        }
        public static Task<AuthorizationResult> AuthorizeAsync(this IAuthorizationService service, ClaimsPrincipal user, object resource, AuthorizationPolicy policy)
        {
            if (service == null)
            {
                throw new ArgumentNullException(nameof(service));
            }

            if (policy == null)
            {
                throw new ArgumentNullException(nameof(policy));
            }

            return service.AuthorizeAsync(user, resource, policy.Requirements);
        }
        public static Task<AuthorizationResult> AuthorizeAsync(this IAuthorizationService service, ClaimsPrincipal user, AuthorizationPolicy policy)
        {
            if (service == null)
            {
                throw new ArgumentNullException(nameof(service));
            }

            if (policy == null)
            {
                throw new ArgumentNullException(nameof(policy));
            }

            return service.AuthorizeAsync(user, resource: null, policy: policy);
        }
        public static Task<AuthorizationResult> AuthorizeAsync(this IAuthorizationService service, ClaimsPrincipal user, string policyName)
        {
            if (service == null)
            {
                throw new ArgumentNullException(nameof(service));
            }

            if (policyName == null)
            {
                throw new ArgumentNullException(nameof(policyName));
            }

            return service.AuthorizeAsync(user, resource: null, policyName: policyName);
        }
    }

介面的默認實作為DefaultAuthorizationService

DefaultAuthorizationService的實作主要是用來對 IAuthorizationRequirement物件的授權檢驗，

public class DefaultAuthorizationService : IAuthorizationService
{
    private readonly AuthorizationOptions _options;
    private readonly IAuthorizationHandlerContextFactory _contextFactory;
    private readonly IAuthorizationHandlerProvider _handlers;
    private readonly IAuthorizationEvaluator _evaluator;
    private readonly IAuthorizationPolicyProvider _policyProvider;
    private readonly ILogger _logger;
    
    public DefaultAuthorizationService(IAuthorizationPolicyProvider policyProvider, IAuthorizationHandlerProvider handlers, ILogger<DefaultAuthorizationService> logger, IAuthorizationHandlerContextFactory contextFactory, IAuthorizationEvaluator evaluator, IOptions<AuthorizationOptions> options)
    {
        if (options == null)
        {
            throw new ArgumentNullException(nameof(options));
        }
        if (policyProvider == null)
        {
            throw new ArgumentNullException(nameof(policyProvider));
        }
        if (handlers == null)
        {
            throw new ArgumentNullException(nameof(handlers));
        }
        if (logger == null)
        {
            throw new ArgumentNullException(nameof(logger));
        }
        if (contextFactory == null)
        {
            throw new ArgumentNullException(nameof(contextFactory));
        }
        if (evaluator == null)
        {
            throw new ArgumentNullException(nameof(evaluator));
        }

        _options = options.Value;
        _handlers = handlers;
        _policyProvider = policyProvider;
        _logger = logger;
        _evaluator = evaluator;
        _contextFactory = contextFactory;
    }

    public async Task<AuthorizationResult> AuthorizeAsync(ClaimsPrincipal user, object resource, IEnumerable<IAuthorizationRequirement> requirements)
    {
        if (requirements == null)
        {
            throw new ArgumentNullException(nameof(requirements));
        }

        var authContext = _contextFactory.CreateContext(requirements, user, resource);
        var handlers = await _handlers.GetHandlersAsync(authContext);
        foreach (var handler in handlers)
        {
            await handler.HandleAsync(authContext);
            if (!_options.InvokeHandlersAfterFailure && authContext.HasFailed)
            {
                break;
            }
        }

        var result = _evaluator.Evaluate(authContext);
        if (result.Succeeded)
        {
            _logger.UserAuthorizationSucceeded();
        }
        else
        {
            _logger.UserAuthorizationFailed();
        }
        return result;
    }

    public async Task<AuthorizationResult> AuthorizeAsync(ClaimsPrincipal user, object resource, string policyName)
    {
        if (policyName == null)
        {
            throw new ArgumentNullException(nameof(policyName));
        }

        var policy = await _policyProvider.GetPolicyAsync(policyName);
        if (policy == null)
        {
            throw new InvalidOperationException($"No policy found: {policyName}.");
        }
        return await this.AuthorizeAsync(user, resource, policy);
    }
}

通過上面的代碼可以發現，在物件實體中，通過建構式的方式分別注入了IAuthorizationPolicyProvider、IAuthorizationHandlerProvider、IAuthorizationEvaluator、IAuthorizationHandlerContextFactory這幾個核心服務，以及配置選項的AuthorizationOptions物件，再通過實作的方法AuthorizeAsync可以看出，在方法中呼叫GetPolicyAsync來獲取Requirements，具體的可以看一下上一節的AuthorizationPolicy，而后在根據授權背景關系來判斷，

這里就用到了注入的幾個核心物件來實作完成授權的，下面會分別介紹到的，

3.2 IAuthorizationPolicyProvider

由上面的IAuthorizationServer介面的默認實作可以發現，在進行授權檢驗的時候，DefaultAuthorizationService會利用注入的IAuthorizationPolicyProvider服務來提供注冊的授權策略，所以我們查看原始碼發現，介面提供了默認的授權策略GetDefaultPolicyAsync和指定名稱的授權策略·GetPolicyAsync(string policyName)的方法，

public interface IAuthorizationPolicyProvider
{
    Task<AuthorizationPolicy> GetPolicyAsync(string policyName);
    Task<AuthorizationPolicy> GetDefaultPolicyAsync();
    Task<AuthorizationPolicy> GetFallbackPolicyAsync();
}

再加上在使用[Authorize]進行策略授權的時候，會根據提供的介面方法來獲取指定的授權策略，

IAuthorizationPolicyProvider來根據名稱獲取到策略物件，默認實作為DefaultAuthorizationPolicyProvider：

DefaultAuthorizationPolicyProvider

    public class DefaultAuthorizationPolicyProvider : IAuthorizationPolicyProvider
    {
        private readonly AuthorizationOptions _options;
        private Task<AuthorizationPolicy> _cachedDefaultPolicy;
        private Task<AuthorizationPolicy> _cachedFallbackPolicy;

        public DefaultAuthorizationPolicyProvider(IOptions<AuthorizationOptions> options)
        {
            if (options == null)
            {
                throw new ArgumentNullException(nameof(options));
            }

            _options = options.Value;
        }

        public Task<AuthorizationPolicy> GetDefaultPolicyAsync()
        {
            return GetCachedPolicy(ref _cachedDefaultPolicy, _options.DefaultPolicy);
        }

        public Task<AuthorizationPolicy> GetFallbackPolicyAsync()
        {
            return GetCachedPolicy(ref _cachedFallbackPolicy, _options.FallbackPolicy);
        }

        private Task<AuthorizationPolicy> GetCachedPolicy(ref Task<AuthorizationPolicy> cachedPolicy, AuthorizationPolicy currentPolicy)
        {
            var local = cachedPolicy;
            if (local == null || local.Result != currentPolicy)
            {
                cachedPolicy = local = Task.FromResult(currentPolicy);
            }
            return local;
        }

        public virtual Task<AuthorizationPolicy> GetPolicyAsync(string policyName)
        {
            return Task.FromResult(_options.GetPolicy(policyName));
        }
    }

由上面的代碼可以看出，在實作DefaultAuthorizationPolicyProvider物件進行建構式的方式注入了IOptions<AuthorizationOptions> options服務來提供配置選項AuthorizationOptions(不懂的可以查看上一篇的AuthorizationOptions)，再通過實作的方法可以看出是如何獲取到注冊的授權策略的了，附加一個圖片

在上一章中介紹過，我們定義的策略都保存在AuthorizationOptions的中PolicyMap字典中，由上代碼可以發現這字典的用處，

3.3 IAuthorizationHandlerContextFactory

先看看這個介面的源代碼

public interface IAuthorizationHandlerContextFactory
{
    AuthorizationHandlerContext CreateContext(IEnumerable<IAuthorizationRequirement> requirements, ClaimsPrincipal user, object resource);
}

介面定義了一個唯一的方法CreateContext,作用在于創建授權背景關系AuthorizationHandlerContext物件，介面默認實作方式

    public class DefaultAuthorizationHandlerContextFactory : IAuthorizationHandlerContextFactory
    {
        public virtual AuthorizationHandlerContext CreateContext(IEnumerable<IAuthorizationRequirement> requirements, ClaimsPrincipal user, object resource)
        {
            return new AuthorizationHandlerContext(requirements, user, resource);
        }
    }

再來看看AuthorizationHandlerContext授權背景關系物件，可以看出，背景關系中主要包括用戶的Claims和授權策略的要求Requirements

public class AuthorizationHandlerContext
{
        private HashSet<IAuthorizationRequirement> _pendingRequirements;
        private bool _failCalled;
        private bool _succeedCalled;
    public AuthorizationHandlerContext(
        IEnumerable<IAuthorizationRequirement> requirements,
        ClaimsPrincipal user,
        object resource)
    {
        if (requirements == null)
        {
            throw new ArgumentNullException(nameof(requirements));
        }

        Requirements = requirements;
        User = user;
        Resource = resource;
        _pendingRequirements = new HashSet<IAuthorizationRequirement>(requirements);
    }

    public virtual IEnumerable<IAuthorizationRequirement> Requirements { get; }

    public virtual ClaimsPrincipal User { get; }

    public virtual object Resource { get; }

    public virtual IEnumerable<IAuthorizationRequirement> PendingRequirements { get { return _pendingRequirements; } }

    public virtual bool HasFailed { get { return _failCalled; } }

    public virtual bool HasSucceeded
    {
        get
        {
            return !_failCalled && _succeedCalled && !PendingRequirements.Any();
        }
    }

    public virtual void Fail()
    {
        _failCalled = true;
    }
    public virtual void Succeed(IAuthorizationRequirement requirement)
    {
        _succeedCalled = true;
        _pendingRequirements.Remove(requirement);
    }
}

因此，在下面我們剛好會提到了IAuthorizationHandlerProvider 中的方法，可以根據授權背景關系獲取到請求呼叫的處理程式，

3.4 IAuthorizationHandlerProvider

這個是介面的方法，作用是獲取所有的授權Handler

public interface IAuthorizationHandlerProvider
{
    Task<IEnumerable<IAuthorizationHandler>> GetHandlersAsync(AuthorizationHandlerContext context);
}

根據之前提到的授權背景關系作為GetHandlersAsync方法引數物件來提取IAuthorizationHandler物件，

默認介面的實作為DefaultAuthorizationHandlerProvider, 處理程式的默認實作，為授權請求提供IAuthorizationHandler

    public class DefaultAuthorizationHandlerProvider : IAuthorizationHandlerProvider
    {
        private readonly IEnumerable<IAuthorizationHandler> _handlers;

        public DefaultAuthorizationHandlerProvider(IEnumerable<IAuthorizationHandler> handlers)
        {
            if (handlers == null)
            {
                throw new ArgumentNullException(nameof(handlers));
            }

            _handlers = handlers;
        }

        public Task<IEnumerable<IAuthorizationHandler>> GetHandlersAsync(AuthorizationHandlerContext context)
            => Task.FromResult(_handlers);
    }

從默認實作的方式可以看出，利用建構式的方式注入默認的IAuthorizationHandler的物件，但是我們再看看介面的實作方法可以發現，GetHandlersAsync回傳的IAuthorizationHandler物件并不是從給定的AuthorizationHandlerContext背景關系中獲取的，而是直接通過建構式的方式注入得到的，

這個時候，你可能會問，那么IAuthorizationHandler是在哪里注入的呢？

對應下面的 IAuthorizationHandler

3.5 IAuthorizationEvaluator

由DefaultAuthorizationService中的授權方法程序呼叫了

   var result = _evaluator.Evaluate(authContext);

IAuthorizationEvaluator介面，來確定授權結果是否成功，

    public interface IAuthorizationEvaluator
    {
        AuthorizationResult Evaluate(AuthorizationHandlerContext context);
    }

IAuthorizationEvaluator的唯一方法Evaluate,該方法會根據之前提供的授權背景關系回傳一個表示授權成功的AuthorizationResult物件，默認實作為DefaultAuthorizationEvaluator

public class DefaultAuthorizationEvaluator : IAuthorizationEvaluator
{
    public AuthorizationResult Evaluate(AuthorizationHandlerContext context)
        => context.HasSucceeded
            ? AuthorizationResult.Success()
            : AuthorizationResult.Failed(context.HasFailed
                ? AuthorizationFailure.ExplicitFail()
                : AuthorizationFailure.Failed(context.PendingRequirements));
}

由默認實作可以看出，AuthorizationHandlerContext物件的HasSucceeded屬性決定了授權是否成功，當驗證通過時，授權背景關系中的HasSucceeded才會為True，

其中的AuthorizationResult和AuthorizationFailure分別為

public class AuthorizationResult
{
     private AuthorizationResult() { }
    public bool Succeeded { get; private set; }
    public AuthorizationFailure Failure { get; private set; }
    public static AuthorizationResult Success() => new AuthorizationResult { Succeeded = true };

    public static AuthorizationResult Failed(AuthorizationFailure failure) => new AuthorizationResult { Failure = failure };

    public static AuthorizationResult Failed() => new AuthorizationResult { Failure = AuthorizationFailure.ExplicitFail() };

}

public class AuthorizationFailure
{
    private AuthorizationFailure() { }

    public bool FailCalled { get; private set; }

    public IEnumerable<IAuthorizationRequirement> FailedRequirements { get;private set; }
    
    public static AuthorizationFailure ExplicitFail()
        => new AuthorizationFailure
    {
        FailCalled = true,
        FailedRequirements = new IAuthorizationRequirement[0]
    };

    public static AuthorizationFailure Failed(IEnumerable<IAuthorizationRequirement> failed)
        => new AuthorizationFailure { FailedRequirements = failed };
}

這里的兩個授權結果正是IAuthorizationService 進行實作授權AuthorizeAsync來完成校驗回傳的結果，

3.6 IAuthorizationHandler

介面方式實作，判斷是否授權，實作此介面的類

public interface IAuthorizationHandler
{
    Task HandleAsync(AuthorizationHandlerContext context);
}

如果允許授權，可通過此介面的方法來決定是否允許授權，

之前我們還介紹到，我們定義的Requirement，可以直接實作IAuthorizationHandler介面，也可以單獨定義Handler，但是需要注冊到DI系統中去，

在默認的AuthorizationHandlerProvider中，會從DI系統中獲取到我們注冊的所有Handler，最終呼叫其HandleAsync方法，

我們在實作IAuthorizationHandler介面時，通常是繼承自AuthorizationHandler來實作，它有如下定義：
public abstract class AuthorizationHandler<TRequirement> : IAuthorizationHandler where TRequirement : IAuthorizationRequirement
{
public virtual async Task HandleAsync(AuthorizationHandlerContext context)
{
foreach (var req in context.Requirements.OfType<TRequirement>())
{
   await HandleRequirementAsync(context, req);
}
}

protected abstract Task HandleRequirementAsync(AuthorizationHandlerContext context, TRequirement requirement);
}
如上，首先會在HandleAsync過濾出與Requirement對匹配的Handler，然后再呼叫其HandleRequirementAsync方法，

那我們定義的直接實作IAuthorizationHandler了介面的Requirement又是如何執行的呢？

我們可以發現，IAuthorizationHandler在AddAuthorization拓展方法中可以看到默認注冊了一個PassThroughAuthorizationHandler默認實作為：

public class PassThroughAuthorizationHandler : IAuthorizationHandler
{
    public async Task HandleAsync(AuthorizationHandlerContext context)
    {
        foreach (var handler in context.Requirements.OfType<IAuthorizationHandler>())
        {
            await handler.HandleAsync(context);
        }
    }
}

它負責呼叫該策略中所有實作了IAuthorizationHandler介面的Requirement，通過介面實作的方法可以看出，當PassThroughAuthorizationHandler物件的HandleAsync方法被執行的時候，它會從AuthroizationHanderContext的Requirements屬性中提取所有的IAuthoizationHandler物件，并逐個呼叫它們的HandleAsync方法來實施授權檢驗，

所以可以看到的出，PassThroughAuthorizationHandler是一個特殊并且重要的授權處理器型別，其特殊之處在于它并沒有實作針對某個具體規則的授權檢驗，但是AuthorizationHandlerContext背景關系所有的IAuthorizationHandler都是通過該物件驅動執行的，

3.7 IPolicyEvaluator

介面的方式實作，為特定需求型別呼叫的授權處理程式的基類

    public interface IPolicyEvaluator
    {
        Task<AuthenticateResult> AuthenticateAsync(AuthorizationPolicy policy, HttpContext context);
        Task<PolicyAuthorizationResult> AuthorizeAsync(AuthorizationPolicy policy, AuthenticateResult authenticationResult, HttpContext context, object resource);
    }

定義了兩個方法AuthenticateAsync和AuthorizeAsync方法

IPolicyEvaluator的默認實作為PolicyEvaluator

    public class PolicyEvaluator : IPolicyEvaluator
    {
        private readonly IAuthorizationService _authorization;
        
        public PolicyEvaluator(IAuthorizationService authorization)
        {
            _authorization = authorization;
        }

        public virtual async Task<AuthenticateResult> AuthenticateAsync(AuthorizationPolicy policy, HttpContext context)
        {
            if (policy.AuthenticationSchemes != null && policy.AuthenticationSchemes.Count > 0)
            {
                ClaimsPrincipal newPrincipal = null;
                foreach (var scheme in policy.AuthenticationSchemes)
                {
                    var result = await context.AuthenticateAsync(scheme);
                    if (result != null && result.Succeeded)
                    {
                        newPrincipal = SecurityHelper.MergeUserPrincipal(newPrincipal, result.Principal);
                    }
                }

                if (newPrincipal != null)
                {
                    context.User = newPrincipal;
                    return AuthenticateResult.Success(new AuthenticationTicket(newPrincipal, string.Join(";", policy.AuthenticationSchemes)));
                }
                else
                {
                    context.User = new ClaimsPrincipal(new ClaimsIdentity());
                    return AuthenticateResult.NoResult();
                }
            }

            return (context.User?.Identity?.IsAuthenticated ?? false) 
                ? AuthenticateResult.Success(new AuthenticationTicket(context.User, "context.User"))
                : AuthenticateResult.NoResult();
        }

        public virtual async Task<PolicyAuthorizationResult> AuthorizeAsync(AuthorizationPolicy policy, AuthenticateResult authenticationResult, HttpContext context, object resource)
        {
            if (policy == null)
            {
                throw new ArgumentNullException(nameof(policy));
            }

            var result = await _authorization.AuthorizeAsync(context.User, resource, policy);
            if (result.Succeeded)
            {
                return PolicyAuthorizationResult.Success();
            }

            // If authentication was successful, return forbidden, otherwise challenge
            return (authenticationResult.Succeeded) 
                ? PolicyAuthorizationResult.Forbid() 
                : PolicyAuthorizationResult.Challenge();
        }
    }

授權中間件委托它來實作身份驗證和授權處理，它內部會呼叫AuthorizationService，進而執行所有授權處理器AuthorizationHandler, （在后面會提到授權中間件用到這兩個方法）

3.7.1、AuthenticateAsync

當授權策略沒有設定AuthenticationSchemes，則只判斷下當前請求是否已做身份驗證，若做了就回傳成功
當授權策略設定了AuthenticationSchemes，則遍歷身份驗證方案逐個進行身份驗證處理，

其中context.User就是使用context.AuthenticateAsync(DefaultAuthenticateScheme)來賦值的，將所有得到的用戶標識重組成一個復合的用戶標識，

當我們希望使用非默認的Scheme，或者是想合并多個認證Scheme的Claims時，就需要使用基于Scheme的授權來重置Claims了，

它的實作也很簡單，直接使用我們在授權策略中指定的Schemes來依次呼叫認證服務的AuthenticateAsync方法，并將生成的Claims合并，最后回傳我們熟悉的AuthenticateResult認證結果，

3.7.2、AuthorizeAsync

該方法會根據Requirements來完成授權，具體的實作是通過呼叫IAuthorizationService呼叫AuthorizeAsync來實作的，

最侄訓傳的是一個PolicyAuthorizationResult物件，并在授權失敗時，根據認證結果來回傳Forbid(未授權)或Challenge(未登錄)，

以上匯總

授權服務IAuthorizationService，介面的默認實作為DefaultAuthorizationService，進行授權驗證，

在會根據授權策略提供器IAuthorizationPolicyProvider來獲取指定名稱的授權，

通過授權處理器背景關系物件工廠IAuthorizationHandlerContextFactory授權處理器AuthorizationHandler在授權時需要傳入AuthorizationHandlerContext（上面說了授權完成后的結果也存盤在里面），所以在執行授權處理器之前需要構建這個背景關系物件，就是通過這個工廠構建的，主要的資料來源就是當前或者 指定的 授權策略AuthorizationPolicy，

所以這個時候會授權處理提供其 IAuthorizationHandlerProvider，來獲取系統中所有授權處理器，

授權評估器IAuthorizationEvaluator來確定授權結果是否成功，在授權處理器AuthorizationHandler在執行完授權后，結果是存盤在AuthorizationHandlerContext中的，這里的評估器只是根據AuthorizationHandlerContext創建一個授權結果AuthorizationResult，

上面所說的授權處理器就是IAuthorizationHandler,處理器中包含主要的授權邏輯，在處理的程序中會將所有的授權處理器一一驗證，

所以在授權中間件中會利用IPolicyEvaluator中實作的身份認證和授權處理方法來呼叫AuthorizationService來執行所有的處理器，

四、中間件

在Configure中注冊管道：運行使用呼叫方法來配置Http請求管道

    public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
    {    app.UseRouting();
        //開啟認證授權
         app.UseAuthentication();
        app.UseAuthorization();

    }

在這里使用了授權中間件來檢查授權，來看看中間件的原始碼AuthorizationMiddleware

public class AuthorizationMiddleware
{
    // Property key is used by Endpoint routing to determine if Authorization has run
    private const string AuthorizationMiddlewareInvokedWithEndpointKey = "__AuthorizationMiddlewareWithEndpointInvoked";
    private static readonly object AuthorizationMiddlewareWithEndpointInvokedValue = https://www.cnblogs.com/i3yuan/p/new object();

    private readonly RequestDelegate _next;
    private readonly IAuthorizationPolicyProvider _policyProvider;

    public AuthorizationMiddleware(RequestDelegate next, IAuthorizationPolicyProvider policyProvider)
    {
        _next = next ?? throw new ArgumentNullException(nameof(next));
        _policyProvider = policyProvider ?? throw new ArgumentNullException(nameof(policyProvider));
    }

    public async Task Invoke(HttpContext context)
    {
        if (context == null)
        {
            throw new ArgumentNullException(nameof(context));
        }
        var endpoint = context.GetEndpoint();

        if (endpoint != null)
        {
            context.Items[AuthorizationMiddlewareInvokedWithEndpointKey] = AuthorizationMiddlewareWithEndpointInvokedValue;
        }

        var authorizeData = endpoint?.Metadata.GetOrderedMetadata() ?? Array.Empty();
        var policy = await AuthorizationPolicy.CombineAsync(_policyProvider, authorizeData);
        if (policy == null)
        {
            await _next(context);
            return;
        }
        var policyEvaluator = context.RequestServices.GetRequiredService();

        var authenticateResult = await policyEvaluator.AuthenticateAsync(policy, context);
        // Allow Anonymous skips all authorization
        if (endpoint?.Metadata.GetMetadata() != null)
        {
            await _next(context);
            return;
        }
        // Note that the resource will be null if there is no matched endpoint
        var authorizeResult = await policyEvaluator.AuthorizeAsync(policy, authenticateResult, context, resource: endpoint);

        if (authorizeResult.Challenged)
        {
            if (policy.AuthenticationSchemes.Any())
            {
                foreach (var scheme in policy.AuthenticationSchemes)
                {
                    await context.ChallengeAsync(scheme);
                }
            }
            else
            {
                await context.ChallengeAsync();
            }

            return;
        }
        else if (authorizeResult.Forbidden)
        {
            if (policy.AuthenticationSchemes.Any())
            {
                foreach (var scheme in policy.AuthenticationSchemes)
                {
                    await context.ForbidAsync(scheme);
                }
            }
            else
            {
                await context.ForbidAsync();
            }

            return;
        }
        await _next(context);
    }
}

進行代碼分解：

拿到當前請求的的終結點

  var endpoint = context.GetEndpoint();

在當前請求拿到終結點endpoint的時候，會通過終結點拿到關聯的IAuthorizeData集合

var authorizeData = https://www.cnblogs.com/i3yuan/p/endpoint?.Metadata.GetOrderedMetadata() ?? Array.Empty();

將根據IAuthorizeData集合呼叫AuthorizationPolicy.CombineAsync()來創建組合策略（具體了可以看一下上一章）（用例： [Authorize(Policy = "BaseRole")] ）

var policy = await AuthorizationPolicy.CombineAsync(_policyProvider, authorizeData);

IPolicyEvaluator獲取策略評估器對得到的組合策略進行身份驗證，多種身份驗證得到的用戶證件資訊會合并進HttpContext.User

 var policyEvaluator = context.RequestServices.GetRequiredService<IPolicyEvaluator>();

  var authenticateResult = await policyEvaluator.AuthenticateAsync(policy, context);

當使用[AllowAnonymous]的時候，則直接跳過授權檢驗，

 if (endpoint?.Metadata.GetMetadata<IAllowAnonymous>() != null)
 {
     await _next(context);
     return;
 }

將IPolicyEvaluator提供的AuthorizeAsync授權檢查方法，進行策略授權檢查，

 var authorizeResult = await policyEvaluator.AuthorizeAsync(policy, authenticateResult, context, resource: endpoint);

當進行授權時，遍歷策略所有的身份驗證方案，進行質詢，若策略里木有身份驗證方案則使用默認身份驗證方案進行質詢，

當授權評估拒絕就直接呼叫身份驗證方案進行拒絕，

 if (authorizeResult.Challenged)
 {
     if (policy.AuthenticationSchemes.Any())
     {
         foreach (var scheme in policy.AuthenticationSchemes)
         {
             await context.ChallengeAsync(scheme);
         }
     }
     else
     {
         await context.ChallengeAsync();
     }
     return;
 }
else if (authorizeResult.Forbidden)
{
    if (policy.AuthenticationSchemes.Any())
    {
        foreach (var scheme in policy.AuthenticationSchemes)
        {
            await context.ForbidAsync(scheme);
        }
    }
    else
    {
        await context.ForbidAsync();
    }

    return;
}

整個程序中，授權中間件會呼叫授權服務IAuthorizationService來進行授權處理

五、總結

通過對上述的處理流程的分析，可以看出授權主要是通過IAuthorizationService來實作的，而我們進行使用只需要提供授權策略的Requirement，非常方便靈活的使用，
從原始碼權限設計來看，系統注冊了各種服務，實作多種默認服務，加上默認的處理方式也滿足了大部分應用需求，所以可以看出這一塊的功能還是很強大的，就算我們想通過自定義的方式來實作，也可以通過某些介面來實作拓展，
其中有很多核心原始碼怕說的不夠清楚，所以在平時的開發專案中，再去看官方檔案或原始碼這樣理解應該更容易，
如果有不對的或不理解的地方，希望大家可以多多指正，提出問題，一起討論,不斷學習,共同進步，
參考的檔案和官方原始碼

轉載請註明出處，本文鏈接：https://www.uj5u.com/net/3522.html

標籤：.NET Core

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