ASP.NET Core WebAPI中使用JWT Bearer认证和受权

时间 2019-12-08

标签 asp.net asp core webapi 使用 jwt bearer 认证受权栏目 ASP 繁體版

原文原文链接

目录html

为何是 JWT Bearer

ASP.NET Core 在 Microsoft.AspNetCore.Authentication 下实现了一系列认证, 包含 Cookie, JwtBearer, OAuth, OpenIdConnect 等,git

Cookie 认证是一种比较经常使用本地认证方式, 它由浏览器自动保存并在发送请求时自动附加到请求头中, 更适用于 MVC 等纯网页系统的本地认证.
OAuth & OpenID Connect 一般用于运程认证, 建立一个统一的认证中心, 来统一配置和处理对于其余资源和服务的用户认证及受权.
JwtBearer 认证中, 客户端一般将 JWT(一种Token) 经过 HTTP 的 Authorization header 发送给服务端, 服务端进行验证. 能够方便的用于 WebAPI 框架下的本地认证.
固然, 也能够彻底本身实现一个WebAPI下基于Token的本地认证, 好比自定义Token的格式, 本身写颁发和验证Token的代码等. 这样的话通用性并很差, 并且也须要花费更多精力来封装代码以及处理细节.

什么是 JWT

JWT (JSON Web Token) 是一种基于JSON的、用于在网络上声明某种主张的令牌（token）。
做为一个开放的标准（RFC 7519），定义了一种简洁的、自包含的方法，从而使通讯双方实现以JSON对象的形式安全的传递信息。github

JWT一般由三部分组成: 头信息（header）, 消息体（payload）和签名（signature）。
头信息指定了该JWT使用的签名算法：web

header = {"alg": "HS256", "typ": "JWT"}

消息体包含了JWT的意图：算法

payload = {"sub": "1234567890", "name": "John Doe", "iat": 1516239022}

未签名的令牌由base64url编码的头信息和消息体拼接而成（使用"."分隔），签名则经过私有的key计算而成：数据库

key = "secretkey" 
unsignedToken = encodeBase64(header) + '.' + encodeBase64(payload)  
signature = HMAC-SHA256(key, unsignedToken)

最后在尾部拼接上base64url编码的签名（一样使用"."分隔）就是JWT了：json

token = encodeBase64(header) + '.' + encodeBase64(payload) + '.' + encodeBase64(signature)

JWT经常被用做保护服务端的资源，客户端一般将JWT经过HTTP的Authorization header发送给服务端，服务端使用本身保存的key计算、验证签名以判断该JWT是否可信。后端

Authorization: Bearer <token>

JWT 的优缺点

相比于传统的 cookie-session 认证机制，优势有：api

更适用分布式和水平扩展
在cookie-session方案中，cookie内仅包含一个session标识符，而诸如用户信息、受权列表等都保存在服务端的session中。若是把session中的认证信息都保存在JWT中，在服务端就没有session存在的必要了。当服务端水平扩展的时候，就不用处理session复制（session replication）/ session黏连（sticky session）或是引入外部session存储了。浏览器
适用于多客户端（特别是移动端）的先后端解决方案
移动端使用的每每不是网页技术，使用Cookie验证并非一个好主意，由于你得和Cookie容器打交道，而使用Bearer验证则简单的多。
无状态化
JWT 是无状态化的，更适用于 RESTful 风格的接口验证。

它的缺点也很明显：

更多的空间占用
JWT 因为Payload里面包含了附件信息，占用空间每每比SESSION ID大，在HTTP传输中会形成性能影响。因此在设计时候须要注意不要在JWT中存储太多的claim,以免发生巨大的,过分膨胀的请求。
没法做废已颁布的令牌
全部的认证信息都在JWT中，因为在服务端没有状态，即便你知道了某个JWT被盗取了，你也没有办法将其做废。在JWT过时以前（你绝对应该设置过时时间），你无能为力。

在 WebAPI 中使用 JWT 认证

定义配置类 JwtIssuerOptions.cs

public class JwtIssuerOptions
{
    /// <summary>
    /// 4.1.1.  "iss" (Issuer) Claim - The "iss" (issuer) claim identifies the principal that issued the JWT.
    /// </summary>
    public string Issuer { get; set; }

    /// <summary>
    /// 4.1.2.  "sub" (Subject) Claim - The "sub" (subject) claim identifies the principal that is the subject of the JWT.
    /// </summary>
    public string Subject { get; set; }

    /// <summary>
    /// 4.1.3.  "aud" (Audience) Claim - The "aud" (audience) claim identifies the recipients that the JWT is intended for.
    /// </summary>
    public string Audience { get; set; }

    /// <summary>
    /// 4.1.4.  "exp" (Expiration Time) Claim - The "exp" (expiration time) claim identifies the expiration time on or after which the JWT MUST NOT be accepted for processing.
    /// </summary>
    public DateTime Expiration => IssuedAt.Add(ValidFor);

    /// <summary>
    /// 4.1.5.  "nbf" (Not Before) Claim - The "nbf" (not before) claim identifies the time before which the JWT MUST NOT be accepted for processing.
    /// </summary>
    public DateTime NotBefore => DateTime.UtcNow;

    /// <summary>
    /// 4.1.6.  "iat" (Issued At) Claim - The "iat" (issued at) claim identifies the time at which the JWT was issued.
    /// </summary>
    public DateTime IssuedAt => DateTime.UtcNow;

    /// <summary>
    /// Set the timespan the token will be valid for (default is 120 min)
    /// </summary>
    public TimeSpan ValidFor { get; set; } = TimeSpan.FromMinutes(120);


    /// <summary>
    /// "jti" (JWT ID) Claim (default ID is a GUID)
    /// </summary>
    public Func<Task<string>> JtiGenerator =>
      () => Task.FromResult(Guid.NewGuid().ToString());

    /// <summary>
    /// The signing key to use when generating tokens.
    /// </summary>
    public SigningCredentials SigningCredentials { get; set; }
}

定义的帮助类 JwtFactory.cs, 主要是用于生成Token

public interface IJwtFactory
{
    Task<string> GenerateEncodedToken(string userName, ClaimsIdentity identity);
    ClaimsIdentity GenerateClaimsIdentity(User user);
}

public class JwtFactory : IJwtFactory
{
    private readonly JwtIssuerOptions _jwtOptions;

    public JwtFactory(IOptions<JwtIssuerOptions> jwtOptions)
    {
        _jwtOptions = jwtOptions.Value;
        ThrowIfInvalidOptions(_jwtOptions);
    }

    public async Task<string> GenerateEncodedToken(string userName, ClaimsIdentity identity)
    {
        var claims = new List<Claim>
        {
            new Claim(JwtRegisteredClaimNames.Sub, userName),
            new Claim(JwtRegisteredClaimNames.Jti, await _jwtOptions.JtiGenerator()),
            new Claim(JwtRegisteredClaimNames.Iat, ToUnixEpochDate(_jwtOptions.IssuedAt).ToString(), ClaimValueTypes.Integer64),
            identity.FindFirst(ClaimTypes.Name),
            identity.FindFirst("id")
        };
        claims.AddRange(identity.FindAll(ClaimTypes.Role));

        // Create the JWT security token and encode it.
        var jwt = new JwtSecurityToken(
            issuer: _jwtOptions.Issuer,
            audience: _jwtOptions.Audience,
            claims: claims,
            notBefore: _jwtOptions.NotBefore,
            expires: _jwtOptions.Expiration,
            signingCredentials: _jwtOptions.SigningCredentials);

        var encodedJwt = new JwtSecurityTokenHandler().WriteToken(jwt);

        var response = new
        {
            auth_token = encodedJwt,
            expires_in = (int)_jwtOptions.ValidFor.TotalSeconds,
            token_type = "Bearer"
        };

        return JsonConvert.SerializeObject(response, new JsonSerializerSettings { Formatting = Formatting.Indented });
    }

    public ClaimsIdentity GenerateClaimsIdentity(User user)
    {
        var claimsIdentity  = new ClaimsIdentity(new GenericIdentity(user.UserName, "Token"));
        claimsIdentity.AddClaim(new Claim("id", user.Id.ToString()));
        claimsIdentity.AddClaim(new Claim(ClaimTypes.Name, user.UserName));
        foreach (var role in user.Roles)
        {
            claimsIdentity.AddClaim(new Claim(ClaimTypes.Role, role));
        }
        return claimsIdentity;
    }

    /// <returns>Date converted to seconds since Unix epoch (Jan 1, 1970, midnight UTC).</returns>
    private static long ToUnixEpochDate(DateTime date)
      => (long)Math.Round((date.ToUniversalTime() -
                           new DateTimeOffset(1970, 1, 1, 0, 0, 0, TimeSpan.Zero))
                          .TotalSeconds);

    private static void ThrowIfInvalidOptions(JwtIssuerOptions options)
    {
        if (options == null) throw new ArgumentNullException(nameof(options));

        if (options.ValidFor <= TimeSpan.Zero)
        {
            throw new ArgumentException("Must be a non-zero TimeSpan.", nameof(JwtIssuerOptions.ValidFor));
        }

        if (options.SigningCredentials == null)
        {
            throw new ArgumentNullException(nameof(JwtIssuerOptions.SigningCredentials));
        }

        if (options.JtiGenerator == null)
        {
            throw new ArgumentNullException(nameof(JwtIssuerOptions.JtiGenerator));
        }
    }
}

在 Startup.cs 里面添加相关代码:

读取配置:

var jwtAppSettingOptions = Configuration.GetSection(nameof(JwtIssuerOptions));
services.Configure<JwtIssuerOptions>(options =>
{
    options.Issuer = jwtAppSettingOptions[nameof(JwtIssuerOptions.Issuer)];
    options.Audience = jwtAppSettingOptions[nameof(JwtIssuerOptions.Audience)];
    options.SigningCredentials = new SigningCredentials(_signingKey, SecurityAlgorithms.HmacSha256);
});

JwtBearer验证:

public class Startup
{
    private const string SecretKey = "iNivDmHLpUA223sqsfhqGbMRdRj1PVkH"; // todo: get this from somewhere secure
    private readonly SymmetricSecurityKey _signingKey = new SymmetricSecurityKey(System.Text.Encoding.UTF8.GetBytes(SecretKey));

    public void ConfigureServices(IServiceCollection services)
    {
        services.AddSingleton<IJwtFactory, JwtFactory>();

        services.AddAuthentication(options =>
        {
            options.DefaultAuthenticateScheme = JwtBearerDefaults.AuthenticationScheme;
            options.DefaultChallengeScheme = JwtBearerDefaults.AuthenticationScheme;

        }).AddJwtBearer(configureOptions =>
        {
            configureOptions.ClaimsIssuer = jwtAppSettingOptions[nameof(JwtIssuerOptions.Issuer)];
            configureOptions.TokenValidationParameters = new TokenValidationParameters
            {
                ValidateIssuer = true,
                ValidIssuer = jwtAppSettingOptions[nameof(JwtIssuerOptions.Issuer)],
                ValidateAudience = true,
                ValidAudience = jwtAppSettingOptions[nameof(JwtIssuerOptions.Audience)],
                ValidateIssuerSigningKey = true,
                IssuerSigningKey = _signingKey,
                RequireExpirationTime = false,
                ValidateLifetime = true,
                ClockSkew = TimeSpan.Zero
            };
            configureOptions.SaveToken = true;
        });
    }

    public void Configure(IApplicationBuilder app, IHostingEnvironment env)
    {
        app.UseAuthentication();
        app.UseMvc();
    }
}

Swagger相关:

services.AddSwaggerGen(options =>
{
    var security = new Dictionary<string, IEnumerable<string>> { { "Bearer", new string[] { } }, };
    options.AddSecurityRequirement(security);
    options.AddSecurityDefinition("Bearer", new Swashbuckle.AspNetCore.Swagger.ApiKeyScheme
    {
        Description = "Format: Bearer {auth_token}",
        Name = "Authorization",
        In = "header"
    });
});

建立一个控制器 AuthController.cs，用来提供签发 Token 的 API

[Route("api/[controller]")]
[ApiController]
public class AuthController : ControllerBase
{
    private readonly IJwtFactory _jwtFactory;
    private readonly JwtIssuerOptions _jwtOptions;

    public AuthController(IJwtFactory jwtFactory, IOptions<JwtIssuerOptions> jwtOptions)
    {
        _jwtFactory = jwtFactory;
        _jwtOptions = jwtOptions.Value;
    }

    /// <summary>
    /// Log in
    /// </summary>
    /// <param name="request"></param>
    /// <returns></returns>
    [HttpPost("[action]")]
    public async Task<IActionResult> Login([FromBody]LoginRequest request)
    {
        var users = TestUsers.Users.Where(r => r.UserName.Equals(request.UserName));
        if (users.Count() <= 0)
        {
            ModelState.AddModelError("login_failure", "Invalid username.");
            return BadRequest(ModelState);
        }
        var user = users.First();
        if (!request.Password.Equals(user.Password))
        {
            ModelState.AddModelError("login_failure", "Invalid password.");
            return BadRequest(ModelState);
        }

        var claimsIdentity = _jwtFactory.GenerateClaimsIdentity(user.UserName, user.Id.ToString());
        var token = await _jwtFactory.GenerateEncodedToken(user.UserName, claimsIdentity);
        return new OkObjectResult(token);
    }

    /// <summary>
    /// Get User Info
    /// </summary>
    /// <returns></returns>
    [HttpGet("[action]")]
    [Authorize]
    public IActionResult GetUserInfo()
    {
        var claimsIdentity = User.Identity as ClaimsIdentity;
        return Ok(claimsIdentity.Claims.ToList().Select(r=> new { r.Type, r.Value}));
    }
}

为须要保护的API添加 [Authorize] 特性

[Route("api/[controller]")]
[ApiController]
[Authorize]
public class ValuesController : ControllerBase
{
    // GET api/values
    [HttpGet]
    public ActionResult<IEnumerable<string>> Get()
    {
        return new string[] { "value1", "value2" };
    }
}

使用 Swagger UI 或者 PostMan 等工具测试

获取Token:

curl -X POST "http://localhost:5000/api/Auth/Login" -H "accept: application/json" -H "Content-Type: application/json-patch+json" -d "{ \"userName\": \"Paul\", \"password\": \"Paul123\"}"

返回值:

"{\r\n  \"auth_token\": \"eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.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.UAWLYQ5lA6xWofWIjGsPGWtAMHEtqZSfrfVaBui2mKI\",\r\n  \"expires_in\": 7200,\r\n  \"token_type\": \"Bearer\"\r\n}"

在 https://jwt.io/ 上解析 Token 以下:

{
  "sub": "Paul",
  "jti": "3b5c1233-e25a-4ee9-bd66-cf4656ac33d3",
  "iat": 1544589869,
  "http://schemas.xmlsoap.org/ws/2005/05/identity/claims/name": "Paul",
  "id": "d37f27ce-8780-4425-9135-b688a76c4c0f",
  "http://schemas.microsoft.com/ws/2008/06/identity/claims/role": ["administrator","api_access"],
  "nbf": 1544589868,
  "exp": 1544597068,
  "iss": "SecurityDemo.Authentication.JWT",
  "aud": "http://localhost:5000/"
}

使用 Token 访问受保护的 API

curl -X GET "http://localhost:5000/api/Values" -H "accept: text/plain" -H "Authorization: Bearer eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.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.UAWLYQ5lA6xWofWIjGsPGWtAMHEtqZSfrfVaBui2mKI"

刷新 Token

由于JWT在服务端是没有状态的, 不管用户注销, 修改密码仍是Token被盗取, 你都没法将其做废. 因此给JWT设置有效期而且尽可能短是颇有必要的. 但咱们不可能让用户每次Token过时后都从新输入一次用户名和密码为了生成新的Token. 最好是有种方式在用户无感知的状况下完成Token刷新. 因此这里引入了Refresh Token.

修改 JwtFactory 中的 GenerateEncodedToken 方法, 新加一个参数 refreshToken, 并在包含在 response 里和 auth_token 一块儿返回.

public async Task<string> GenerateEncodedToken(string userName, string refreshToken, ClaimsIdentity identity)
{
    var response = new
    {
        auth_token = encodedJwt,
        refresh_token = refreshToken,
        expires_in = (int)_jwtOptions.ValidFor.TotalSeconds,
        token_type = "Bearer"
    };

    return JsonConvert.SerializeObject(response, new JsonSerializerSettings { Formatting = Formatting.Indented });
}

修改 AuthController 中的 Login Action, 在每次客户端请求 JWT Token 的时候, 同时生成一个 GUID 的 refreshToken. 这个 refreshToken 须要保存在数据库或者缓存里. 这里方便演示放入了 MemoryCache 里面. 缓存的过时时间要比JWT Token的过时时间稍微长一点.

string refreshToken = Guid.NewGuid().ToString();
var claimsIdentity = _jwtFactory.GenerateClaimsIdentity(user);

_cache.Set(refreshToken, user.UserName, TimeSpan.FromMinutes(11));

var token = await _jwtFactory.GenerateEncodedToken(user.UserName, refreshToken, claimsIdentity);
return new OkObjectResult(token);

添加一个RefreshToken的接口, 接收参数 refresh_token, 而后检查 refresh_token 的有效性, 若是有效生成一个新的 auth_token 和 refresh_token 并返回. 同时须要删除掉原来 refresh_token 的缓存.
这里只是简单的利用缓存的过时时间和auth_token的过时时间相近从而默认 refresh_token 是有效的, 精确期间须要把对应的 auth_token过时时间一块儿放入缓存, 在刷新Token的时候验证这个时间.

/// <summary>
/// RefreshToken
/// </summary>
/// <param name="request"></param>
/// <returns></returns>
[HttpPost("[action]")]
public async Task<IActionResult> RefreshToken([FromBody]RefreshTokenRequest request)
{
    string userName;
    if (!_cache.TryGetValue(request.RefreshToken, out userName))
    {
        ModelState.AddModelError("refreshtoken_failure", "Invalid refreshtoken.");
        return BadRequest(ModelState);
    }
    if (!request.UserName.Equals(userName))
    {
        ModelState.AddModelError("refreshtoken_failure", "Invalid userName.");
        return BadRequest(ModelState);
    }

    var user = _userService.GetUserByName(request.UserName);
    string newRefreshToken = Guid.NewGuid().ToString();
    var claimsIdentity = _jwtFactory.GenerateClaimsIdentity(user);

    _cache.Remove(request.RefreshToken);
    _cache.Set(newRefreshToken, user.UserName, TimeSpan.FromMinutes(11));

    var token = await _jwtFactory.GenerateEncodedToken(user.UserName, newRefreshToken, claimsIdentity);
    return new OkObjectResult(token);
}

测试

获取Token:

curl -X POST "http://localhost:5000/api/Auth/Login" -H "accept: application/json" -H "Content-Type: application/json-patch+json" -d "{ \"userName\": \"Paul\", \"password\": \"Paul123\"}"

返回值:

"{\r\n  \"auth_token\": \"eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.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.tEJ-EuaI-BalW4lJEL8aeJzdryKfE440EC4cAVOW1PY\",\r\n  \"refresh_token\": \"3093f839-fd3c-47a3-97a9-c0324e4e6b7e\",\r\n  \"expires_in\": 600,\r\n  \"token_type\": \"Bearer\"\r\n}"

请求RefreshToken:

curl -X POST "http://localhost:5000/api/Auth/RefreshToken" -H "accept: application/json" -H "Content-Type: application/json-patch+json" -d "{ \"userName\": \"Paul\", \"refreshToken\": \"3093f839-fd3c-47a3-97a9-c0324e4e6b7e\"}"

返回新的 auth_token 和 refresh_token

"{\r\n  \"auth_token\": \"eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.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.A1hXNVmkqD80GqfF69LwvarpNf5QedPvKFDcB5xA4Z0\",\r\n  \"refresh_token\": \"b33de8ff-5213-4d37-be0b-7b561553e0f7\",\r\n  \"expires_in\": 600,\r\n  \"token_type\": \"Bearer\"\r\n}"

使用受权

在认证阶段咱们经过用户令牌获取到了用户的Claims，而受权即是对这些Claims进行验证, 好比是否拥有某种角色，年龄是否大于18岁(若是Claims里有年龄信息)等。

简单受权

ASP.NET Core中使用Authorize特性受权, 使用AllowAnonymous特性跳过受权.

//全部用户均可以Login, 但只有受权的用户才能够Logout.
public class AccountController : Controller
{
    [AllowAnonymous]
    public ActionResult Login()
    {
    }
    
    [Authorize]
    public ActionResult Logout()
    {
    }
}

基于固定角色的受权

适用于系统中的角色是固定的，每种角色能够访问的Controller和Action也是固定的情景.

//能够指定多个角色, 以逗号分隔
[Authorize(Roles = "Administrator")]
public class AdministrationController : Controller
{
}

基于策略的受权

在ASP.NET Core中，从新设计了一种更加灵活的受权方式：基于策略的受权, 它是受权的核心.
在使用基于策略的受权时，首先要定义受权策略，而受权策略本质上就是对Claims的一系列断言。
基于角色的受权和基于Scheme的受权，只是一种语法上的便捷，最终都会生成受权策略。

public void ConfigureServices(IServiceCollection services)
{
    services.AddMvc();

    services.AddAuthorization(options =>
    {
        //options.AddPolicy("Administrator", policy => policy.RequireRole("administrator"));
        options.AddPolicy("Administrator", policy => policy.RequireClaim(ClaimTypes.Role, "administrator"));
        
        //options.AddPolicy("Founders", policy => policy.RequireClaim("EmployeeNumber", "1", "2", "3", "4", "5"));
    });
}

[Authorize(Policy = "Administrator")]
public ActionResult<IEnumerable<string>> GetValueByAdminPolicy()
{
    return new string[] { "GetValueByAdminPolicy" };
}

自定义策略受权

基于策略的受权中有一个很重要的概念是Requirements，每个Requirement都表明一个受权条件。
Requirement须要继承接口IAuthorizationRequirement。
在 ASP.NET Core 中已经内置了一些经常使用的实现：

AssertionRequirement ：使用最原始的断言形式来声明受权策略。
DenyAnonymousAuthorizationRequirement ：用于表示禁止匿名用户访问的受权策略，并在AuthorizationOptions中将其设置为默认策略。
ClaimsAuthorizationRequirement ：用于表示判断Cliams中是否包含预期的Claims的受权策略。
RolesAuthorizationRequirement ：用于表示使用ClaimsPrincipal.IsInRole来判断是否包含预期的Role的受权策略。
NameAuthorizationRequirement：用于表示使用ClaimsPrincipal.Identities.Name来判断是否包含预期的Name的受权策略。
OperationAuthorizationRequirement：用于表示基于操做的受权策略。

除了OperationAuthorizationRequirement外，都有对应的快捷添加方法，好比RequireClaim，RequireRole，RequireUserName等。

当内置的Requirement不能知足需求时，能够定义本身的Requirement. 下面基于图中所示的用户-角色-功能权限设计来实现一个自定义的验证策略。

添加一个静态类 TestUsers 用于模拟用户数据
这里只是模拟, 实际使用当中确定是从数据库取数据, 同时也应该有相似于User, Role, Function, UserRole, RoleFunction等几张表保存这些数据.

public static class TestUsers
{
    public static List<User> Users = new List<User>
    {
        new User{ Id = Guid.NewGuid(), UserName = "Paul", Password = "Paul123", Roles = new List<string>{ "administrator", "api_access" }, Urls = new List<string>{ "/api/values/getadminvalue", "/api/values/getguestvalue" }},
        new User{ Id = Guid.NewGuid(), UserName = "Young", Password = "Young123", Roles = new List<string>{ "api_access" }, Urls = new List<string>{ "/api/values/getguestvalue" }},
        new User{ Id = Guid.NewGuid(), UserName = "Roy", Password = "Roy123", Roles = new List<string>{ "administrator" }, Urls = new List<string>{ "/api/values/getadminvalue" }},
    };
}

public class User
{
    public Guid Id { get; set; }
    public string UserName { get; set; }
    public string Password { get; set; }
    public List<string> Roles { get; set; }
    public List<string> Urls { get; set; }
}

建立类 UserService 用于获取用户已受权的功能列表.

public interface IUserService
{
    List<string> GetFunctionsByUserId(Guid id);
}

public class UserService : IUserService
{
    public List<string> GetFunctionsByUserId(Guid id)
    {
        var user = TestUsers.Users.SingleOrDefault(r => r.Id.Equals(id));
        return user?.Urls;
    }
}

建立 PermissionRequirement

public class PermissionRequirement : IAuthorizationRequirement
{
}

建立 PermissionHandler
获取当前的URL, 并去当前用户已受权的URL List里查看. 若是匹配就验证成功.

public class PermissionHandler : AuthorizationHandler<PermissionRequirement>
{
    private readonly IUserService _userService;

    public PermissionHandler(IUserService userService)
    {
        _userService = userService;
    }

    protected override Task HandleRequirementAsync(AuthorizationHandlerContext context, PermissionRequirement requirement)
    {
        var httpContext = (context.Resource as Microsoft.AspNetCore.Mvc.Filters.AuthorizationFilterContext).HttpContext;

        var isAuthenticated = httpContext.User.Identity.IsAuthenticated;
        if (isAuthenticated)
        {
            Guid userId;
            if (!Guid.TryParse(httpContext.User.Claims.SingleOrDefault(s => s.Type == "id").Value, out userId))
            {
                return Task.CompletedTask;
            }
            var functions = _userService.GetFunctionsByUserId(userId);
            var requestUrl = httpContext.Request.Path.Value.ToLower();
            if (functions != null && functions.Count > 0 && functions.Contains(requestUrl))
            {
                context.Succeed(requirement);
            }
        }
        return Task.CompletedTask;
    }
}

在Startup.cs 的 ConfigureServices 里面注册 PermissionHandler 并添加 Policy.

services.AddAuthorization(options =>
{
    options.AddPolicy("Permission", policy => policy.Requirements.Add(new PermissionRequirement()));
});
services.AddSingleton<IAuthorizationHandler, PermissionHandler>();

添加测试代码并测试
注意这里Controller, Action须要和用户功能表里的URL一致

[Route("api/[controller]")]
[ApiController]
public class ValuesController : ControllerBase
{
    [HttpGet("[action]")]
    [Authorize(Policy = "Permission")]
    public ActionResult<IEnumerable<string>> GetAdminValue()
    {
        return new string[] { "use Policy = Permission" };
    }

    [HttpGet("[action]")]
    [Authorize(Policy = "Permission")]
    public ActionResult<IEnumerable<string>> GetGuestValue()
    {
        return new string[] { "use Policy = Permission" };
    }
}

使用咱们的模拟数据, 用户 Paul 两个Action GetAdminValue 和 GetGuestValue 均可以访问; Young 只有权限访问 GetGuestValue; 而 Roy 只能够访问 GetAdminValue.

基于资源的受权

有些时候, 受权须要依赖于要访问的资源, 好比:只容许做者本身编辑和删除所写的博客.
这种场景是没法经过Authorize特性来指定受权的, 由于受权过滤器会在MVC的模型绑定以前执行，没法肯定所访问的资源。此时，咱们须要使用基于资源的受权。
在基于资源的受权中, 咱们要判断的是用户是否具备针对该资源的某项操做, 而系统预置的OperationAuthorizationRequirement就是用于这种场景中的.

public class OperationAuthorizationRequirement : IAuthorizationRequirement
{
    public string Name { get; set; }
}

定义一些经常使用操做, 方便业务调用.

public static class ResourceOperations
{
    public static OperationAuthorizationRequirement Create = new OperationAuthorizationRequirement { Name = "Create" };
    public static OperationAuthorizationRequirement Read = new OperationAuthorizationRequirement { Name = "Read" };
    public static OperationAuthorizationRequirement Update = new OperationAuthorizationRequirement { Name = "Update" };
    public static OperationAuthorizationRequirement Delete = new OperationAuthorizationRequirement { Name = "Delete" };
}

咱们是根据资源的建立者来判断用户是否具备操做权限，所以，定义一个资源实体的接口, 包含一个字段 Creator
```
public interface IResourceWithCreator
{
    string Creator { get; set; }
}
```

定义测试数据用于模拟

public static class TestBlogs
{
    public static List<Blog> Blogs = new List<Blog>
    {
        new Blog{ Id = Guid.Parse("CA4A3FC9-42CA-47F4-B651-36A863023E75"), Name = "Paul_Blog_1", BlogUrl = "blogs/paul/1", Creator = "Paul" },
        new Blog{ Id = Guid.Parse("9C03EDA8-FBCD-4C33-B5C8-E4DFC40258D7"), Name = "Paul_Blog_2", BlogUrl = "blogs/paul/2", Creator = "Paul" },
        new Blog{ Id = Guid.Parse("E05E3625-1885-49A5-87D0-54F7EAF90C88"), Name = "Young_Blog_1", BlogUrl = "blogs/young/1", Creator = "Young" },
        new Blog{ Id = Guid.Parse("E97D5DF4-AE50-4258-84F8-0B3052EB2CB8"), Name = "Roy_Blog_1", BlogUrl = "blogs/roy/1", Creator = "Roy" },
    };
}

public class Blog : IResourceWithCreator
{
    public Guid Id { get; set; }
    public string Name { get; set; }
    public string BlogUrl { get; set; }

    public string Creator { get; set; }
}

定义 ResourceAuthorizationHandler
容许任何人建立或查看资源, 有只有资源的建立者才能够修改和删除资源.

public class ResourceAuthorizationHandler : AuthorizationHandler<OperationAuthorizationRequirement, IResourceWithCreator>
{
    protected override Task HandleRequirementAsync(AuthorizationHandlerContext context, OperationAuthorizationRequirement requirement, IResourceWithCreator resource)
    {
        if (requirement == ResourceOperations.Create || requirement == ResourceOperations.Read)
        {
            context.Succeed(requirement);
        }
        else
        {
            if (context.User.Identity.Name == resource.Creator)
            {
                context.Succeed(requirement);
            }
        }
        return Task.CompletedTask;
    }
}

在ConfigureServices里注册Handler.

services.AddSingleton<IAuthorizationHandler, ResourceAuthorizationHandler>();

添加控制器并引入IAuthorizationService进行验证

[Authorize]
public class BlogsController : ControllerBase
{
    private readonly IAuthorizationService _authorizationService;
    private readonly IBlogService _blogService;

    public BlogsController(IAuthorizationService authorizationService, IBlogService blogService)
    {
        _authorizationService = authorizationService;
        _blogService = blogService;
    }

    [HttpGet("{id}", Name = "Get")]
    public async Task<ActionResult<Blog>> Get(Guid id)
    {
        var blog = _blogService.GetBlogById(id);
        if ((await _authorizationService.AuthorizeAsync(User, blog, ResourceOperations.Read)).Succeeded)
        {
            return Ok(blog);
        }
        else
        {
            return Forbid();
        }
    }

    [HttpPut("{id}")]
    public async Task<ActionResult> Put(Guid id, [FromBody] Blog newBlog)
    {
        var blog = _blogService.GetBlogById(id);
        if ((await _authorizationService.AuthorizeAsync(User, blog, ResourceOperations.Update)).Succeeded)
        {
            bool result = _blogService.Update(newBlog);
            return Ok(result);
        }
        else
        {
            return Forbid();
        }
    }
}

在实际使用当中, 能够经过EF Core拦截或AOP来实现受权验证与业务代码的分离。

源代码

github