目錄 "AspNetCore3.1_Secutiry源碼解析_1_目錄" "AspNetCore3.1_Secutiry源碼解析_2_Authentication_核心流程" "AspNetCore3.1_Secutiry源碼解析_3_Authentication_Cookies" "AspNetC ...

簡介

開篇提到過，認證主要解決的是who are you，授權解決的是 are you allowed的問題。各種認證架構可以幫我們知道用戶身份（claims），oauth等架構的scope欄位能夠控制api服務級別的訪問許可權，但是更加細化和多變的功能授權不是它們的處理範圍。

微軟的Authorization項目提供了基於策略的靈活的授權框架。

推薦看下麵博客瞭解，我主要學習和梳理源碼。

https://www.cnblogs.com/RainingNight/p/authorization-in-asp-net-core.html

依賴註入

註入了以下介面，提供了預設實現

IAuthorizationService ：授權服務，主幹服務
IAuthorizationPolicyProvider ：策略提供類
IAuthorizationHandlerProvider：處理器提供類
IAuthorizationEvaluator：校驗類
IAuthorizationHandlerContextFactory：授權上下文工廠
IAuthorizationHandler：授權處理器，這個是註入的集合，一個策略可以有多個授權處理器，依次執行
配置類：AuthorizationOptions

微軟的命名風格還是比較一致的
Service：服務
Provider：某類的提供者
Evaluator：校驗預處理類
Factory：工廠
Handler：處理器
Context：上下文

看源碼的過程，不僅可以學習框架背後原理，還可以學習編碼風格和設計模式，還是挺有用處的。

/// <summary>
/// Adds authorization services to the specified <see cref="IServiceCollection" />. 
/// </summary>
/// <param name="services">The <see cref="IServiceCollection" /> to add services to.</param>
/// <returns>The <see cref="IServiceCollection"/> so that additional calls can be chained.</returns>
public static IServiceCollection AddAuthorizationCore(this IServiceCollection services)
{
    if (services == null)
    {
        throw new ArgumentNullException(nameof(services));
    }
    
    services.TryAdd(ServiceDescriptor.Transient<IAuthorizationService, DefaultAuthorizationService>());
    services.TryAdd(ServiceDescriptor.Transient<IAuthorizationPolicyProvider, DefaultAuthorizationPolicyProvider>());
    services.TryAdd(ServiceDescriptor.Transient<IAuthorizationHandlerProvider, DefaultAuthorizationHandlerProvider>());
    services.TryAdd(ServiceDescriptor.Transient<IAuthorizationEvaluator, DefaultAuthorizationEvaluator>());
    services.TryAdd(ServiceDescriptor.Transient<IAuthorizationHandlerContextFactory, DefaultAuthorizationHandlerContextFactory>());
    services.TryAddEnumerable(ServiceDescriptor.Transient<IAuthorizationHandler, PassThroughAuthorizationHandler>());
    return services;
}

/// <summary>
/// Adds authorization services to the specified <see cref="IServiceCollection" />. 
/// </summary>
/// <param name="services">The <see cref="IServiceCollection" /> to add services to.</param>
/// <param name="configure">An action delegate to configure the provided <see cref="AuthorizationOptions"/>.</param>
/// <returns>The <see cref="IServiceCollection"/> so that additional calls can be chained.</returns>
public static IServiceCollection AddAuthorizationCore(this IServiceCollection services, Action<AuthorizationOptions> configure)
{
    if (services == null)
    {
        throw new ArgumentNullException(nameof(services));
    }

    if (configure != null)
    {
        services.Configure(configure);
    }

    return services.AddAuthorizationCore();
}

配置類 - AuthorizationOptions

PolicyMap：策略名稱&策略的字典數據
InvokeHandlersAfterFailure：授權處理器失敗後是否觸發下一個處理器，預設true
DefaultPolicy：預設策略，構造了一個RequireAuthenticatedUser策略，即需要認證用戶，不允許匿名訪問。現在有點線索了，為什麼api一加上[Authorize]，就會校驗授權。
FallbackPolicy：保底策略。沒有任何策略的時候會使用保底策略。感覺有點多此一舉，不是給了個預設策略嗎？
AddPolicy：添加策略
GetPolicy：獲取策略

/// <summary>
/// Provides programmatic configuration used by <see cref="IAuthorizationService"/> and <see cref="IAuthorizationPolicyProvider"/>.
/// </summary>
public class AuthorizationOptions
{
    private IDictionary<string, AuthorizationPolicy> PolicyMap { get; } = new Dictionary<string, AuthorizationPolicy>(StringComparer.OrdinalIgnoreCase);

    /// <summary>
    /// Determines whether authentication handlers should be invoked after a failure.
    /// Defaults to true.
    /// </summary>
    public bool InvokeHandlersAfterFailure { get; set; } = true;

    /// <summary>
    /// Gets or sets the default authorization policy. Defaults to require authenticated users.
    /// </summary>
    /// <remarks>
    /// The default policy used when evaluating <see cref="IAuthorizeData"/> with no policy name specified.
    /// </remarks>
    public AuthorizationPolicy DefaultPolicy { get; set; } = new AuthorizationPolicyBuilder().RequireAuthenticatedUser().Build();

    /// <summary>
    /// Gets or sets the fallback authorization policy used by <see cref="AuthorizationPolicy.CombineAsync(IAuthorizationPolicyProvider, IEnumerable{IAuthorizeData})"/>
    /// when no IAuthorizeData have been provided. As a result, the AuthorizationMiddleware uses the fallback policy
    /// if there are no <see cref="IAuthorizeData"/> instances for a resource. If a resource has any <see cref="IAuthorizeData"/>
    /// then they are evaluated instead of the fallback policy. By default the fallback policy is null, and usually will have no 
    /// effect unless you have the AuthorizationMiddleware in your pipeline. It is not used in any way by the 
    /// default <see cref="IAuthorizationService"/>.
    /// </summary>
    public AuthorizationPolicy FallbackPolicy { get; set; }

    /// <summary>
    /// Add an authorization policy with the provided name.
    /// </summary>
    /// <param name="name">The name of the policy.</param>
    /// <param name="policy">The authorization policy.</param>
    public void AddPolicy(string name, AuthorizationPolicy policy)
    {
        if (name == null)
        {
            throw new ArgumentNullException(nameof(name));
        }

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

        PolicyMap[name] = policy;
    }

    /// <summary>
    /// Add a policy that is built from a delegate with the provided name.
    /// </summary>
    /// <param name="name">The name of the policy.</param>
    /// <param name="configurePolicy">The delegate that will be used to build the policy.</param>
    public void AddPolicy(string name, Action<AuthorizationPolicyBuilder> configurePolicy)
    {
        if (name == null)
        {
            throw new ArgumentNullException(nameof(name));
        }

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

        var policyBuilder = new AuthorizationPolicyBuilder();
        configurePolicy(policyBuilder);
        PolicyMap[name] = policyBuilder.Build();
    }

    /// <summary>
    /// Returns the policy for the specified name, or null if a policy with the name does not exist.
    /// </summary>
    /// <param name="name">The name of the policy to return.</param>
    /// <returns>The policy for the specified name, or null if a policy with the name does not exist.</returns>
    public AuthorizationPolicy GetPolicy(string name)
    {
        if (name == null)
        {
            throw new ArgumentNullException(nameof(name));
        }

        return PolicyMap.ContainsKey(name) ? PolicyMap[name] : null;
    }
}

IAuthorizationService - 授權服務 - 主幹邏輯

介面定義了授權方法，有兩個重載，一個是基於requirements校驗，一個是基於policyName校驗。

Task<AuthorizationResult> AuthorizeAsync(ClaimsPrincipal user, object resource, IEnumerable<IAuthorizationRequirement> requirements);

Task<AuthorizationResult> AuthorizeAsync(ClaimsPrincipal user, object resource, string policyName);

看下預設實現DefaultAuthorizationService的處理,邏輯還是比較簡單

獲取策略
獲取策略的授權條件
獲取授權上下文
獲取處理器集合
處理器依次執行，結果存入上下文
校驗器驗證上下文
返回授權結果類

 /// <summary>
/// The default implementation of an <see cref="IAuthorizationService"/>.
/// </summary>
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;

    /// <summary>
    /// Creates a new instance of <see cref="DefaultAuthorizationService"/>.
    /// </summary>
    /// <param name="policyProvider">The <see cref="IAuthorizationPolicyProvider"/> used to provide policies.</param>
    /// <param name="handlers">The handlers used to fulfill <see cref="IAuthorizationRequirement"/>s.</param>
    /// <param name="logger">The logger used to log messages, warnings and errors.</param>  
    /// <param name="contextFactory">The <see cref="IAuthorizationHandlerContextFactory"/> used to create the context to handle the authorization.</param>  
    /// <param name="evaluator">The <see cref="IAuthorizationEvaluator"/> used to determine if authorization was successful.</param>  
    /// <param name="options">The <see cref="AuthorizationOptions"/> used.</param>  
    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;
    }

    /// <summary>
    /// Checks if a user meets a specific set of requirements for the specified resource.
    /// </summary>
    /// <param name="user">The user to evaluate the requirements against.</param>
    /// <param name="resource">The resource to evaluate the requirements against.</param>
    /// <param name="requirements">The requirements to evaluate.</param>
    /// <returns>
    /// A flag indicating whether authorization has succeeded.
    /// This value is <value>true</value> when the user fulfills the policy otherwise <value>false</value>.
    /// </returns>
    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;
    }

    /// <summary>
    /// Checks if a user meets a specific authorization policy.
    /// </summary>
    /// <param name="user">The user to check the policy against.</param>
    /// <param name="resource">The resource the policy should be checked with.</param>
    /// <param name="policyName">The name of the policy to check against a specific context.</param>
    /// <returns>
    /// A flag indicating whether authorization has succeeded.
    /// This value is <value>true</value> when the user fulfills the policy otherwise <value>false</value>.
    /// </returns>
    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);
    }
}

預設策略 - 需要認證用戶

預設策略添加了校驗條件DenyAnonymousAuthorizationRequirement

public AuthorizationPolicyBuilder RequireAuthenticatedUser()
{
    Requirements.Add(new DenyAnonymousAuthorizationRequirement());
    return this;
}

校驗上下文中是否存在認證用戶信息，驗證通過則在上下文中將校驗條件標記為成功。

protected override Task HandleRequirementAsync(AuthorizationHandlerContext context, DenyAnonymousAuthorizationRequirement requirement)
    {
        var user = context.User;
        var userIsAnonymous =
            user?.Identity == null ||
            !user.Identities.Any(i => i.IsAuthenticated);
        if (!userIsAnonymous)
        {
            context.Succeed(requirement);
        }
        return Task.CompletedTask;
    }

授權時序圖

授權項目還是比較好理解的，微軟提供了一個基於策略的授權模型，大部門的具體的業務代碼還是需要自己去實現的。

classDiagram class AuthorizationPolicy{ Requirements } class Requirement{ } class AuthorizationHandler{ } class IAuthorizationHandler{ +HandleAsync(AuthorizationHandlerContext context) } class IAuthorizationRequirement{ } Requirement-->AuthorizationHandler AuthorizationHandler-->IAuthorizationHandler Requirement-->IAuthorizationHandler Requirement-->IAuthorizationRequirement

中間件去哪了？

開發不需要編寫UseAuthorization類似代碼，項目中也沒發現中間件，甚至找不到使用AuthorizeAttribute的地方。那麼問題來了，框架怎麼知道某個方法標記了[Authorize]特性，然後執行校驗的呢？

答案是Mvc框架處理的，它讀取了節點的[Authorize]和[AllowAnonymous]特性，並觸發相應的邏輯。關於Mvc的就不細說了，感興趣可以翻看源碼。
AspNetCore\src\Mvc\Mvc.Core\src\ApplicationModels\AuthorizationApplicationModelProvider.cs。

public void OnProvidersExecuting(ApplicationModelProviderContext context)
{
    if (context == null)
    {
        throw new ArgumentNullException(nameof(context));
    }

    if (_mvcOptions.EnableEndpointRouting)
    {
        // When using endpoint routing, the AuthorizationMiddleware does the work that Auth filters would otherwise perform.
        // Consequently we do not need to convert authorization attributes to filters.
        return;
    }

    foreach (var controllerModel in context.Result.Controllers)
    {
        var controllerModelAuthData = controllerModel.Attributes.OfType<IAuthorizeData>().ToArray();
        if (controllerModelAuthData.Length > 0)
        {
            controllerModel.Filters.Add(GetFilter(_policyProvider, controllerModelAuthData));
        }
        foreach (var attribute in controllerModel.Attributes.OfType<IAllowAnonymous>())
        {
            controllerModel.Filters.Add(new AllowAnonymousFilter());
        }

        foreach (var actionModel in controllerModel.Actions)
        {
            var actionModelAuthData = actionModel.Attributes.OfType<IAuthorizeData>().ToArray();
            if (actionModelAuthData.Length > 0)
            {
                actionModel.Filters.Add(GetFilter(_policyProvider, actionModelAuthData));
            }

            foreach (var attribute in actionModel.Attributes.OfType<IAllowAnonymous>())
            {
                actionModel.Filters.Add(new AllowAnonymousFilter());
            }
        }
    }
}

AspNetCore3.1_Secutiry源碼解析_8_Authorization_授權框架

目錄

簡介