【ASP.NET Core】运行原理(4):授权
本系列将分析ASP.NET Core运行原理
- 【ASP.NET Core】运行原理(1):创建WebHost
- 【ASP.NET Core】运行原理(2):启动WebHost
- 【ASP.NET Core】运行原理(3):认证
- 【ASP.NET Core】运行原理(4):授权
在认证阶段通过用户令牌获取到用户的Claims，而授权就是对这些Claims的验证。
目录
- 授权核心
- AuthorizationOptions
- AuthorizationPolicy
- AuthorizationPolicyBuilder
- 执行授权
- AuthorizeFilter
- IPolicyEvaluator
- IAuthorizationService
- 总结
授权核心
services.AddAuthorization(opt => opt.AddPolicy("isAdmin", builder => builder.RequireUserName("admin")));
通过上面的代码，可以添加一个isAdmin的授权。
对于第一个参数opt：
public class AuthorizationOptions
{
private IDictionary<string, AuthorizationPolicy> PolicyMap { get; } = new Dictionary<string, AuthorizationPolicy>();
public void AddPolicy(string name, AuthorizationPolicy policy)
{
PolicyMap[name] = policy;
}
public void AddPolicy(string name, Action<AuthorizationPolicyBuilder> configurePolicy)
{
var policyBuilder = new AuthorizationPolicyBuilder();
configurePolicy(policyBuilder);
AddPolicy(name,policyBuilder.Build());
}
public AuthorizationPolicy GetPolicy(string name)
{
return PolicyMap.ContainsKey(name) ? PolicyMap[name] : null;
}
}
实际上，AuthorizationOptions相当于AuthorizationPolicy的集合
而AuthorizationPolicy则是一个具体的授权策略对象
public class AuthorizationPolicy
{
public IReadOnlyList<IAuthorizationRequirement> Requirements { get; }
public IReadOnlyList<string> AuthenticationSchemes { get; }
}
而AuthorizationPolicyBuilder通过Build方法可以构建一个AuthorizationPolicy，其内部有很多常用的添加IAuthorizationRequirement的方法：
public AuthorizationPolicy Build()
{
return new AuthorizationPolicy(this.Requirements, this.AuthenticationSchemes);
}
public AuthorizationPolicyBuilder RequireUserName(string userName)
{
this.Requirements.Add(new NameAuthorizationRequirement(userName));
}
... Require() ...
IAuthorizationRequirement是授权策略AuthorizationPolicy的一个授权条件,策略下的所有授权条件满足，则授权成功。
public interface IAuthorizationRequirement
{
}
public class NameAuthorizationRequirement : IAuthorizationRequirement
{
public string RequiredName { get; }
}
IAuthorizationHandler是授权条件IAuthorizationRequirement的具体处理器，授权条件下的任意1个处理器授权成功，则授权成功。(默认情况下：AuthorizationOptions的InvokeHandlersAfterFailure = true)
public interface IAuthorizationHandler
{
Task HandleAsync(AuthorizationHandlerContext context);
}
public abstract class AuthorizationHandler<TRequirement> : IAuthorizationHandler where TRequirement : IAuthorizationRequirement
{
public virtual async Task HandleAsync(AuthorizationHandlerContext context)
{
foreach (TRequirement requirement in context.Requirements)
await HandleRequirementAsync(context, requirement);
}
protected abstract Task HandleRequirementAsync(AuthorizationHandlerContext context, TRequirement requirement);
}
public class NameAuthorizationRequirement : AuthorizationHandler<NameAuthorizationRequirement>
{
protected override Task HandleRequirementAsync(AuthorizationHandlerContext context, NameAuthorizationRequirement requirement)
{
if (context.User?.Identities.Any(identity => identity.Name == requirement.RequiredName))
context.Succeed((IAuthorizationRequirement) requirement);
return Task.CompletedTask;
}
}
授权的最终实现代码在IAuthorizationHandler
执行授权
解释了授权策略的原理，再谈谈授权策略的触发。通常我们在MVC中使用授权功能，而触发授权也是在注册MVC代码中，一并注册了。
public static IMvcBuilder AddMvc(this IServiceCollection services)
{
IMvcCoreBuilder builder = services.AddMvcCore();
builder.AddAuthorization();
}
internal static void AddAuthorizationServices(IServiceCollection services)
{
services.AddAuthenticationCore();
services.AddAuthorization();
services.AddAuthorizationPolicyEvaluator();
services.TryAddEnumerable(ServiceDescriptor.Transient<IApplicationModelProvider, AuthorizationApplicationModelProvider>());
}
在MVC中，ApplicationModel用来描述MVC中的模型，而IApplicationModelProvider则是初始化MVC的模型:
public class ApplicationModel
{
public IList<ControllerModel> Controllers { get; }
public IList<IFilterMetadata> Filters { get; }
}
public interface IApplicationModelProvider
{
int Order { get; }
void OnProvidersExecuting(ApplicationModelProviderContext context);
void OnProvidersExecuted(ApplicationModelProviderContext context);
}
其中AuthorizationApplicationModelProvider会初始化ApplicationModel的授权部分，注册到Filters属性上（AuthorizeFilter 和 AllowAnonymousFilter）。
public interface IAsyncAuthorizationFilter : IFilterMetadata
{
Task OnAuthorizationAsync(AuthorizationFilterContext context);
}
public class AuthorizeFilter : IAsyncAuthorizationFilter
{
public virtual async Task OnAuthorizationAsync(AuthorizationFilterContext context)
{
var policyEvaluator = GetRequiredService<IPolicyEvaluator>();
var authenticationResult = await policyEvaluator.AuthenticateAsync(effectivePolicy, context.HttpContext);
var authorizationResult = await policyEvaluator.AuthorizeAsync(effectivePolicy, authenticationResult, context.HttpContext, context);
if (authorizationResult.Challenged)
{
context.Result = (IActionResult) new ChallengeResult((IList<string>) effectivePolicy.AuthenticationSchemes.ToArray<string>());
}
else if (authorizationResult.Forbidden)
{
context.Result = (IActionResult) new ForbidResult((IList<string>) effectivePolicy.AuthenticationSchemes.ToArray<string>());
}
}
}
AuthorizeFilter的OnAuthorizationAsync方法会在Action执行前触发，内部调用IPolicyEvaluator执行
public interface IPolicyEvaluator
{
Task<AuthenticateResult> AuthenticateAsync(AuthorizationPolicy policy, HttpContext context);
Task<PolicyAuthorizationResult> AuthorizeAsync(AuthorizationPolicy policy, AuthenticateResult authenticationResult, HttpContext context, object resource);
}
public class PolicyEvaluator : IPolicyEvaluator
{
private readonly IAuthorizationService _authorization;
public virtual async Task<AuthenticateResult> AuthenticateAsync(AuthorizationPolicy policy, HttpContext context)
{
}
public virtual async Task<PolicyAuthorizationResult> AuthorizeAsync(AuthorizationPolicy policy, AuthenticateResult authenticationResult, HttpContext context, object resource)
{
var result = await _authorization.AuthorizeAsync(context.User, resource, policy);
if (result.Succeeded) return PolicyAuthorizationResult.Success();
return (authenticationResult.Succeeded) ? PolicyAuthorizationResult.Forbid() : PolicyAuthorizationResult.Challenge();
}
}
在AuthenticateAsync方法中，将合并policy的所有scheme认证结果。
在AuthorizeAsync方法中，将调用IAuthorizationService来实现授权。
public interface IAuthorizationService
{
Task<AuthorizationResult> AuthorizeAsync(ClaimsPrincipal user, object resource, IEnumerable<IAuthorizationRequirement> requirements);
Task<AuthorizationResult> AuthorizeAsync(ClaimsPrincipal user, object resource, string policyName);
}
public class DefaultAuthorizationService : IAuthorizationService
{
public async Task<AuthorizationResult> AuthorizeAsync(ClaimsPrincipal user, object resource, string policyName)
{
var policy = await _policyProvider.GetPolicyAsync(policyName);
return await this.AuthorizeAsync(user, resource, policy);
}
public async Task<AuthorizationResult> AuthorizeAsync(ClaimsPrincipal user, object resource, IEnumerable<IAuthorizationRequirement> 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;
}
return _evaluator.Evaluate(authContext);
}
}
在IAuthorizationService类中，将调用policy的所有Requirement的Handle处理
总结
授权核心：AuthorizationOptions、AuthorizationPolicy、AuthorizationPolicyBuilder
AuthorizationOptions 用于保存 AuthorizationPolicy
AuthorizationPolicyBuilder 用于创建 AuthorizationPolicy
AuthorizationPolicy 包含 IAuthorizationRequirement 和 AuthenticationSchemes
IAuthorizationRequirement 包含授权逻辑 IAuthorizationHandler
执行授权：AuthorizeFilter、IPolicyEvaluator、IAuthorizationService
AuthorizeFilter的OnAuthorizationAsync方法会在Action执行前触发，内部调用IPolicyEvaluator执行
IPolicyEvaluator 先根据 Schemes 获取Claims，然后调用 IAuthorizationService 的授权方法
IAuthorizationService 调用 Requirement 对应的Handle授权逻辑
个人觉得源码的一个待优化的地方：在DefaultAuthorizationHandlerProvider的GetHandlersAsync方法按需返回IAuthorizationHandler更合适。
