asp.net core策略授權

在《asp.net core認證與授權》中講解了固定和自定義角色授權系統權限，其實我們還可以通過其他方式來授權，比如可以通過角色組，用戶名，生日等，但這些主要取決于ClaimTypes，其實我們也可以自定義鍵值來授權，這些統一叫策略授權，其中更強大的是，我們可以自定義授權Handler來達到靈活授權，下面一一展開。

注意：下面的代碼只是部分代碼，完整代碼參照：https://github.com/axzxs2001/Asp.NetCoreExperiment/tree/master/Asp.NetCoreExperiment/%E6%9D%83%E9%99%90%E7%AE%A1%E7%90%86/PolicyPrivilegeManagement

首先看基于角色組，或用戶名，或基于ClaimType或自定義鍵值等授權策略，這些都是通過Services.AddAuthorization添加，并且是AuthorizationOptions來AddPolicy，這里策略的名稱統一用RequireClaim來命名，不同的請求的策略名稱各不相同，如用戶名時就用policy.RequireUserName()，同時，在登錄時，驗證成功后，要添加相應的Claim到ClaimsIdentity中：

Startup.cs

       public void ConfigureServices(IServiceCollection services)
        {
            services.AddMvc();
            services.AddAuthorization(options =>
            {
                //基于角色的策略
                 options.AddPolicy("RequireClaim", policy => policy.RequireRole("admin", "system"));
                //基于用戶名
                //options.AddPolicy("RequireClaim", policy => policy.RequireUserName("桂素偉"));
                //基于Claim
                //options.AddPolicy("RequireClaim", policy => policy.RequireClaim(ClaimTypes.Country,"中國"));
                //自定義值
                // options.AddPolicy("RequireClaim", policy => policy.RequireClaim("date","2017-09-02"));

            }).AddAuthentication(CookieAuthenticationDefaults.AuthenticationScheme).AddCookie(options =>{
                options.LoginPath = new PathString("/login");
                options.AccessDeniedPath = new PathString("/denied");
            });          
        }

HomeController.cs

using System.Collections.Generic;
using System.Diagnostics;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Mvc;
using PolicyPrivilegeManagement.Models;
using Microsoft.AspNetCore.Authorization;
using Microsoft.AspNetCore.Authentication;
using Microsoft.AspNetCore.Authentication.Cookies;
using System.Security.Claims;
namespace PolicyPrivilegeManagement.Controllers
{
    [Authorize(Policy = "RequireClaim")]
    public class HomeController : Controller
    {
        PermissionHandler _permissionHandler;
        public HomeController(IAuthorizationHandler permissionHandler)
        {
            _permissionHandler = permissionHandler as PermissionHandler;
        }
        public IActionResult Index()
        {
            return View();
        }
        public IActionResult PermissionAdd()
        {           
            return View();
        }

        public IActionResult Contact()
        {
            ViewData["Message"] = "Your contact page.";
            return View();
        }
        public IActionResult Error()
        {
            return View(new ErrorViewModel { RequestId = Activity.Current?.Id ?? HttpContext.TraceIdentifier });
        }
        [AllowAnonymous]
        [HttpGet("login")]
        public IActionResult Login(string returnUrl = null)
        {
            TempData["returnUrl"] = returnUrl;
            return View();
        }
        [AllowAnonymous]
        [HttpPost("login")]
        public async Task<IActionResult> Login(string userName, string password, string returnUrl = null)
        {
            var list = new List<dynamic> {
                new { UserName = "gsw", Password = "111111", Role = "admin",Name="桂素偉",Country="中國",Date="2017-09-02",BirthDay="1979-06-22"},
                new { UserName = "aaa", Password = "222222", Role = "system",Name="測試A" ,Country="美國",Date="2017-09-03",BirthDay="1999-06-22"}
            };
            var user = list.SingleOrDefault(s => s.UserName == userName && s.Password == password);
            if (user != null)
            {
                //用戶標識
                var identity = new ClaimsIdentity(CookieAuthenticationDefaults.AuthenticationScheme);
                identity.AddClaim(new Claim(ClaimTypes.Sid, userName));
                identity.AddClaim(new Claim(ClaimTypes.Name, user.Name));
                identity.AddClaim(new Claim(ClaimTypes.Role, user.Role));
                identity.AddClaim(new Claim(ClaimTypes.Country, user.Country));
                identity.AddClaim(new Claim("date", user.Date));
                await HttpContext.SignInAsync(CookieAuthenticationDefaults.AuthenticationScheme, new ClaimsPrincipal(identity));
                if (returnUrl == null)
                {
                    returnUrl = TempData["returnUrl"]?.ToString();
                }
                if (returnUrl != null)
                {
                    return Redirect(returnUrl);
                }
                else
                {
                    return RedirectToAction(nameof(HomeController.Index), "Home");
                }
            }
            else
            {
                const string badUserNameOrPasswordMessage = "用戶名或密碼錯誤！";
                return BadRequest(badUserNameOrPasswordMessage);
            }
        }
        [HttpGet("logout")]
        public async Task<IActionResult> Logout()
        {
            await HttpContext.SignOutAsync(CookieAuthenticationDefaults.AuthenticationScheme);
            return RedirectToAction("Index", "Home");
        }
        [AllowAnonymous]
        [HttpGet("denied")]
        public IActionResult Denied()
        {
            return View();
        }
    }
}

上面的授權策略都相對簡單，單一，使用場景也很有限，就和固定角色授權如出一轍，其實可以用更好的來例用授權，那就是自定義授權Handler，我們在《asp.net core認證與授權》一文中，是通過中間件來達到自定義解色的，現在我們換個思路，通過自定義授權Handler來實現。

首先定義一個UserPermission，即用戶權限實體類

    /// <summary>
    /// 用戶權限
    /// </summary>
    public class UserPermission
    {
        /// <summary>
        /// 用戶名
        /// </summary>
        public string UserName
        { get; set; }
        /// <summary>
        /// 請求Url
        /// </summary>
        public string Url
        { get; set; }
    }

接下來定義一個PermissionRequirement，為請求條件實體類

    /// <summary>
    /// 必要參數類
    /// </summary>
    public class PermissionRequirement : IAuthorizationRequirement
    {
        /// <summary>
        /// 用戶權限集合
        /// </summary>
        public  List<UserPermission> UserPermissions { get;private set; }
        /// <summary>
        /// 無權限action
        /// </summary>
        public string DeniedAction { get; set; }
        /// <summary>
        /// 構造
        /// </summary>
        /// <param name="deniedAction">無權限action</param>
        /// <param name="userPermissions">用戶權限集合</param>
        public PermissionRequirement(string deniedAction, List<UserPermission> userPermissions)
        {
            DeniedAction = deniedAction;
            UserPermissions = userPermissions;
        }
    }

再定義自定義授權Hanlder，我們命名為PermissionHandler，此類必需繼承AuthorizationHandler<T>，只用實現public virtualTask HandleAsync(AuthorizationHandlerContext context)，些方法是用戶請求時驗證是否授權的主方法，所以實現與自定義角色中間件的Invoke很相似。

using Microsoft.AspNetCore.Authorization;
using System.Collections.Generic;
using System.Linq;
using System.Security.Claims;
using System.Threading.Tasks;
namespace PolicyPrivilegeManagement.Models
{
    /// <summary>
    /// 權限授權Handler
    /// </summary>
    public class PermissionHandler : AuthorizationHandler<PermissionRequirement>
    {
        /// <summary>
        /// 用戶權限
        /// </summary>
        public List<UserPermission> UserPermissions { get; set; }
        protected override Task HandleRequirementAsync(AuthorizationHandlerContext context, PermissionRequirement requirement)
        {
            //賦值用戶權限
            UserPermissions = requirement.UserPermissions;
            //從AuthorizationHandlerContext轉成HttpContext，以便取出表求信息
            var httpContext = (context.Resource as Microsoft.AspNetCore.Mvc.Filters.AuthorizationFilterContext).HttpContext;
            //請求Url
            var questUrl = httpContext.Request.Path.Value.ToLower();
            //是否經過驗證
            var isAuthenticated = httpContext.User.Identity.IsAuthenticated;
            if (isAuthenticated)
            {
                if (UserPermissions.GroupBy(g => g.Url).Where(w => w.Key.ToLower() == questUrl).Count() > 0)
                {
                    //用戶名
                    var userName = httpContext.User.Claims.SingleOrDefault(s => s.Type == ClaimTypes.Sid).Value;
                    if (UserPermissions.Where(w => w.UserName == userName && w.Url.ToLower() == questUrl).Count() > 0)
                    {
                        context.Succeed(requirement);
                    }
                    else
                    {
                        //無權限跳轉到拒絕頁面
                        httpContext.Response.Redirect(requirement.DeniedAction);
                    }
                }
                else
                {
                    context.Succeed(requirement);
                }
            }
            return Task.CompletedTask;
        }
    }
}

此次的Startup.cs的ConfigureServices發生了變化，如下

       public void ConfigureServices(IServiceCollection services)
        {
            services.AddMvc();
            services.AddAuthorization(options =>
            {               
                //自定義Requirement,userPermission可從數據庫中獲得
                var userPermission = new List<UserPermission> {
                              new UserPermission {  Url="/", UserName="gsw"},
                              new UserPermission {  Url="/home/permissionadd", UserName="gsw"},
                              new UserPermission {  Url="/", UserName="aaa"},
                              new UserPermission {  Url="/home/contact", UserName="aaa"}
                          };
                options.AddPolicy("Permission",
                          policy => policy.Requirements.Add(new PermissionRequirement("/denied", userPermission)));
            }).AddAuthentication(CookieAuthenticationDefaults.AuthenticationScheme).AddCookie(options =>{
                options.LoginPath = new PathString("/login");
                options.AccessDeniedPath = new PathString("/denied");
            });
            //注入授權Handler
            services.AddSingleton<IAuthorizationHandler, PermissionHandler>();
        }

HomeController中代碼如下：

using System.Collections.Generic;
using System.Diagnostics;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Mvc;
using PolicyPrivilegeManagement.Models;
using Microsoft.AspNetCore.Authorization;
using Microsoft.AspNetCore.Authentication;
using Microsoft.AspNetCore.Authentication.Cookies;
using System.Security.Claims;
namespace PolicyPrivilegeManagement.Controllers
{
    [Authorize(Policy = "Permission")]
    public class HomeController : Controller
    {
        PermissionHandler _permissionHandler;
        public HomeController(IAuthorizationHandler permissionHandler)
        {
            _permissionHandler = permissionHandler as PermissionHandler;
        }
        public IActionResult Index()
        {
            return View();
        }
        public IActionResult PermissionAdd()
        {           
            return View();
        }
        [HttpPost("addpermission")]
        public IActionResult AddPermission(string url,string userName)
        {       
            //添加權限
            _permissionHandler.UserPermissions.Add(new UserPermission { Url = url, UserName = userName });
            return Content("添加成功");
        }
        
        public IActionResult Contact()
        {
            ViewData["Message"] = "Your contact page.";
            return View();
        }
        public IActionResult Error()
        {
            return View(new ErrorViewModel { RequestId = Activity.Current?.Id ?? HttpContext.TraceIdentifier });
        }
        [AllowAnonymous]
        [HttpGet("login")]
        public IActionResult Login(string returnUrl = null)
        {
            TempData["returnUrl"] = returnUrl;
            return View();
        }
        [AllowAnonymous]
        [HttpPost("login")]
        public async Task<IActionResult> Login(string userName, string password, string returnUrl = null)
        {
            var list = new List<dynamic> {
                new { UserName = "gsw", Password = "111111", Role = "admin",Name="桂素偉",Country="中國",Date="2017-09-02",BirthDay="1979-06-22"},
                new { UserName = "aaa", Password = "222222", Role = "system",Name="測試A" ,Country="美國",Date="2017-09-03",BirthDay="1999-06-22"}
            };
            var user = list.SingleOrDefault(s => s.UserName == userName && s.Password == password);
            if (user != null)
            {
                //用戶標識
                var identity = new ClaimsIdentity(CookieAuthenticationDefaults.AuthenticationScheme);
                identity.AddClaim(new Claim(ClaimTypes.Sid, userName));
                identity.AddClaim(new Claim(ClaimTypes.Name, user.Name));
                identity.AddClaim(new Claim(ClaimTypes.Role, user.Role));
                identity.AddClaim(new Claim(ClaimTypes.Country, user.Country));
                identity.AddClaim(new Claim("date", user.Date));
                await HttpContext.SignInAsync(CookieAuthenticationDefaults.AuthenticationScheme, new ClaimsPrincipal(identity));
                if (returnUrl == null)
                {
                    returnUrl = TempData["returnUrl"]?.ToString();
                }
                if (returnUrl != null)
                {
                    return Redirect(returnUrl);
                }
                else
                {
                    return RedirectToAction(nameof(HomeController.Index), "Home");
                }
            }
            else
            {
                const string badUserNameOrPasswordMessage = "用戶名或密碼錯誤！";
                return BadRequest(badUserNameOrPasswordMessage);
            }
        }
        [HttpGet("logout")]
        public async Task<IActionResult> Logout()
        {
            await HttpContext.SignOutAsync(CookieAuthenticationDefaults.AuthenticationScheme);
            return RedirectToAction("Index", "Home");
        }
        [AllowAnonymous]
        [HttpGet("denied")]
        public IActionResult Denied()
        {
            return View();
        }
    }
}

本例設計是當用戶gsw密碼111111登錄時，是不能訪問/home/contact的，剛登錄時訪該action是不成功的，這里我們在/home/addpermission中添加一個Action名稱:/home/contact，用戶名:gsw的信息，此時再訪問/home/contact，會發現是可以訪問的，這是因為我們熱更新了PermissionHandler中的用戶權限集合，用戶的權限得到了擴展和變化。

其實用中間件能達到靈活權限的設置，用自定義授權Handler也可以，接下來比較一下兩種做法的優劣：

最后，把授權策略做了個NuGet的包，大家可在asp.net core 2.0的項目中查詢 AuthorizePolicy引用使用這個包，包對應的github地址：https://github.com/axzxs2001/AuthorizePolicy，歡迎大家提出建議，來共同完善這個授權策略。