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ASP.NET Core WebAPI中使用JWT Bearer认证和授权

nanyue 2024-09-11 05:25:57 技术文章 5 ℃

为什么是 JWT Bearer
什么是 JWT
JWT 的优缺点
在 WebAPI 中使用 JWT 认证
刷新 Token
使用授权
简单授权
基于固定角色的授权
基于策略的授权
自定义策略授权
基于资源的授权

为什么是 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,

Cookie 认证是一种比较常用本地认证方式, 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 通常用于运程认证, 创建一个统一的认证中心, 来统一配置和处理对于其他资源和服务的用户认证及授权.
JwtBearer 认证中, 客户端通常将 JWT(一种Token) 通过 HTTP 的 Authorization header 发送给服务端, 服务端进行验证. 可以方便的用于 WebAPI 框架下的本地认证.
当然, 也可以完全自己实现一个WebAPI下基于Token的本地认证, 比如自定义Token的格式, 自己写颁发和验证Token的代码等. 这样的话通用性并不好, 而且也需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）。

作为一个开放的标准（RFC 7519），定义了一种简洁的、自包含的方法，从而使通信双方实现以JSON对象的形式安全的传递信息。

JWT通常由三部分组成: 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：

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

消息体包含了JWT的意图：

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），签名则通过私有的key计算而成：

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（同样使用"."分隔）就是JWT了：

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

JWT常常被用作保护服务端的资源，客户端通常将JWT通过HTTP的Authorization header发送给服务端，服务端使用自己保存的key计算、验证签名以判断该JWT是否可信。

Authorization: Bearer <token>

JWT 的优缺点

相比于传统的 cookie-session 认证机制，优点有：

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、授权列表等都保存在服务端的session中。如果把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。
适用于多客户端（特别是移动端）的前后端解决方案
移动端使用的往往不是网页技术，使用Cookie验证并不是一个好主意，因为你得和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 由于Payload里面包含了附件信息，占用空间往往比SESSION ID大，在HTTP传输中会造成性能影响。所以在设计时候需要注意不要在JWT中存储太多的claim,以避免发生巨大的,过度膨胀的请求。
无法作废已颁布的令牌
所有的认证信息都在JWT中，由于在服务端没有状态，即使你知道了某个JWT被盗取了，你也没有办法将其作废。在JWT过期之前（你绝对应该设置过期时间），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"
 });
});

创建一个控制器 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}));
 }
}

为需要保护的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 如下:

{
 "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

因为JWT在服务端是没有状态的, 无论用户注销, 修改密码还是Token被盗取, 你都无法将其作废. 所以给JWT设置有效期并且尽量短是很有必要的. 但我们不可能让用户每次Token过期后都重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情况下完成Token刷新. 所以这里引入了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 一起返回.

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 需要保存在数据库或者缓存里. 这里方便演示放入了 MemoryCache 里面. 缓存的过期时间要比JWT Token的过期时间稍微长一点.

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, 然后检查 refresh_token 的有效性, 如果有效生成一个新的 auth_token 和 refresh_token 并返回. 同时需要删除掉原来 refresh_token 的缓存.
这里只是简单的利用缓存的过期时间和auth_token的过期时间相近从而默认 refresh_token 是有效的, 精确期间需要把对应的 auth_token过期时间一起放入缓存, 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}"

使用授权

在认证阶段我们通过用户令牌获取到了用户的Claims，而授权便是对这些Claims进行验证, 比如是否拥有某种角色，年龄是否大于18岁(如果Claims里有年龄信息)等。

简单授权

ASP.NET Core中使用Authorize特性授权, 使用AllowAnonymous特性跳过授权.

//所有用户都可以Login, 但只有授权的用户才可以Logout.
public class AccountController : Controller
{
 [AllowAnonymous]
 public ActionResult Login()
 {
 }
 
 [Authorize]
 public ActionResult Logout()
 {
 }
}

基于固定角色的授权

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

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

基于策略的授权

在ASP.NET Core中，重新设计了一种更加灵活的授权方式：基于策略的授权, 它是授权的核心.

在使用基于策略的授权时，首先要定义授权策略，而授权策略本质上就是对Claims的一系列断言。

基于角色的授权和基于Scheme的授权，只是一种语法上的便捷，最终都会生成授权策略。

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" };
}

自定义策略授权

基于策略的授权中有一个很重要的概念是Requirements，每一个Requirement都代表一个授权条件。

Requirement需要继承接口IAuthorizationRequirement。

在 ASP.NET Core 中已经内置了一些常用的实现：

AssertionRequirement ：使用最原始的断言形式来声明授权策略。
DenyAnonymousAuthorizationRequirement ：用于表示禁止匿名用户访问的授权策略，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的授权策略。
RolesAuthorizationRequirement ：用于表示使用ClaimsPrincipal.IsInRole来判断是否包含预期的Role的授权策略。
NameAuthorizationRequirement：用于表示使用ClaimsPrincipal.Identities.Name来判断是否包含预期的Name的授权策略。
OperationAuthorizationRequirement：用于表示基于操作的授权策略。

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

当内置的Requirement不能满足需求时，可以定义自己的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, 实际使用当中肯定是从数据库取数据, 同时也应该有类似于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; }
}

创建类 UserService 用于获取用户已授权的功能列表.

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;
 }
}

创建 PermissionRequirement

public class PermissionRequirement : IAuthorizationRequirement
{
}

创建 PermissionHandler
获取当前的URL, 并去当前用户已授权的URL List里查看. 如果匹配就验证成功.

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需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" };
 }
}

使用我们的模拟数据, 用户 Paul 两个Action GetAdminValue 和 GetGuestValue 都可以访问; Young 只有权限访问 GetGuestValue; 而 Roy 只可以访问 GetAdminValue.

基于资源的授权

有些时候, 授权需要依赖于要访问的资源, 比如:只允许作者自己编辑和删除所写的博客.

这种场景是无法通过Authorize特性来指定授权的, 因为授权过滤器会在MVC的模型绑定之前执行，无法确定所访问的资源。此时，我们需要使用基于资源的授权。

在基于资源的授权中, 我们要判断的是用户是否具有针对该资源的某项操作, 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; }
}

定义一些常用操作, 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" };
}

我们是根据资源的创建者来判断用户是否具有操作权限，因此，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
允许任何人创建或查看资源, 有只有资源的创建者才可以修改和删除资源.

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, 可以通过EF Core拦截或AOP来实现授权验证与业务代码的分离。

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