在.NET Core中使用Jwt對API進行認證

　　在.NET Core中想給API進行安全認證，最簡單的無非就是Jwt，悠然記得一年前寫的Jwt Demo，現在拿回來改成.NET Core的，但是在編碼上的改變並不大，因為Jwt已經足夠強大了。在項目中分為 DotNetCore_Jwt_Server 以及 DotNetCore_Jwt_Client ，從名字就可以看出來是啥意思，博客園高手雲集，我就不多訴說，這篇博客就當是一篇記錄。

　　當然本案例是Server&Client雙項目，如果你要合成自己發證的形式，那你就自己改下代碼玩。

　　在Server層都會有分發Token的服務，在其中做了用戶密碼判斷，隨後根據 Claim 生成 jwtToken 的操作。

　　其生成Token的服務代碼：

namespace DotNetCore_Jwt_Server.Services
{
    public interface ITokenService
    {
        string GetToken(User user);
    }
    public class TokenService : ITokenService
    {
        private readonly JwtSetting _jwtSetting;
        public TokenService(IOptions<JwtSetting> option)
        {
            _jwtSetting = option.Value;
        }
        public string GetToken(User user)
        {
            //創建用戶身份標識，可按需要添加更多信息
            var claims = new Claim[]
            {
                new Claim(JwtRegisteredClaimNames.Jti, Guid.NewGuid().ToString()),
                new Claim("id", user.Id.ToString(), ClaimValueTypes.Integer32),
                new Claim("name", user.Name),
                new Claim("admin", user.IsAdmin.ToString(),ClaimValueTypes.Boolean)
            };

            //創建令牌
            var token = new JwtSecurityToken(
                    issuer: _jwtSetting.Issuer,
                    audience: _jwtSetting.Audience,
                    signingCredentials: _jwtSetting.Credentials,
                    claims: claims,
                    notBefore: DateTime.Now,
                    expires: DateTime.Now.AddSeconds(_jwtSetting.ExpireSeconds)
                );
            string jwtToken = new JwtSecurityTokenHandler().WriteToken(token);
            return jwtToken;
        }
    }
}

在獲取Token中我們依賴註入服務到控制器中，隨後依賴它進行認證並且分發Token，

public class ValuesController : ControllerBase
    {
        private readonly IUserService _userService;
        private readonly ITokenService _tokenService;

        public ValuesController(IUserService userService,
            ITokenService tokenService)
        {
            _userService = userService;
            _tokenService = tokenService;
        }
        [HttpGet]
        public async Task<string> Get()
        {
            await Task.CompletedTask;
            return "Welcome the Json Web Token Solucation!";
        }
        [HttpGet("getToken")]
        public async Task<string> GetTokenAsync(string name, string password)
        {
            var user = await _userService.LoginAsync(name, password);
            if (user == null)
                return "Login Failed";

            var token = _tokenService.GetToken(user);
            var response = new
            {
                Status = true,
                Token = token,
                Type = "Bearer"
            };
            return JsonConvert.SerializeObject(response);
        }
    }

 　　隨後，我們又在項目配置文件中填寫了幾個欄位，相關備註已註釋，但值得說明的是有位朋友問我，伺服器端生成的Token不需要保存嗎，比如Redis或者是Session，其實Jwt Token是無狀態的，他們之間的對比第一個是你的token解密出來的信息正確與否，第二部則是看看你 SecurityKey 是否正確，就這樣他們的認證才會得出結果。

"JwtSetting": {
    "SecurityKey": "d0ecd23c-dfdb-4005-a2ea-0fea210c858a", // 密鑰
    "Issuer": "jwtIssuertest", // 頒發者
    "Audience": "jwtAudiencetest", // 接收者
    "ExpireSeconds": 20000 // 過期時間
  }

　　隨後我們需要DI兩個介面以及初始化設置相關欄位。

public void ConfigureServices(IServiceCollection services)
        {
            services.Configure<JwtSetting>(Configuration.GetSection("JwtSetting")); 
            services.AddScoped<IUserService, UserService>();
            services.AddScoped<ITokenService, TokenService>();
            services.AddControllers();
        }

 　　在Client中，我一般會創建一個中間件用於接受認證結果，AspNetCore Jwt 源碼中給我們提供了中間件，我們在進一步擴展，其源碼定義如下：

/// <summary>
    /// Extension methods to expose Authentication on HttpContext.
    /// </summary>
    public static class AuthenticationHttpContextExtensions
    {/// <summary>
        /// Extension method for authenticate.
        /// </summary>
        /// <param name="context">The <see cref="HttpContext"/> context.</param>
        /// <param name="scheme">The name of the authentication scheme.</param>
        /// <returns>The <see cref="AuthenticateResult"/>.</returns>
        public static Task<AuthenticateResult> AuthenticateAsync(this HttpContext context, string scheme) =>
            context.RequestServices.GetRequiredService<IAuthenticationService>().AuthenticateAsync(context, scheme);
　　}

 　　其該擴展會返回一個 AuthenticateResult 類型的結果，其定義部分是這樣的，我們就可以將計就計，給他來個連環套。

 連環套直接接受 httpContext.AuthenticateAsync(JwtBearerDefaults.AuthenticationScheme)  返回回來的值，隨後進行判斷返回相應的Http響應碼。

public class AuthMiddleware
    {
        private readonly RequestDelegate _next;

        public AuthMiddleware(RequestDelegate next)
        {
            _next = next;
        }
        public async Task Invoke(HttpContext httpContext)
        {
            var result = await httpContext.AuthenticateAsync(JwtBearerDefaults.AuthenticationScheme);
            if (!result.Succeeded)
            {
                httpContext.Response.StatusCode = (int)HttpStatusCode.Unauthorized;
                await httpContext.Response.WriteAsync("Authorize error");
            }
            else
            {
                httpContext.User = result.Principal;
                await _next.Invoke(httpContext);
            }
        }
    }

 　　當然你也得在Client中添加認證的一些設置，它和Server端的 IssuerSigningKey 一定要對應，否則認證失敗。

        public void ConfigureServices(IServiceCollection services)
        {
            services.AddHttpContextAccessor();
            services.AddScoped<IIdentityService, IdentityService>();
            var jwtSetting = new JwtSetting();
            Configuration.Bind("JwtSetting", jwtSetting);

            services.AddCors(options =>
            {
                options.AddPolicy("any", builder =>
                {
                    builder.AllowAnyOrigin() //允許任何來源的主機訪問
                    .AllowAnyMethod()
                    .AllowAnyHeader();

                });
            });

            services.AddAuthentication(JwtBearerDefaults.AuthenticationScheme)
               .AddJwtBearer(options =>
               {
                   options.TokenValidationParameters = new TokenValidationParameters
                   {
                       ValidIssuer = jwtSetting.Issuer,
                       ValidAudience = jwtSetting.Audience,
                       IssuerSigningKey = new SymmetricSecurityKey(Encoding.UTF8.GetBytes(jwtSetting.SecurityKey)),
                       預設 300s
                       ClockSkew = TimeSpan.Zero
                   };
               });
            services.AddControllers();
        }

 　　隨後，你就可以編寫帶需認證才可以訪問的API了，如果認證失敗則會返回401的錯誤響應。

　　[Route("api/[controller]")]
    [ApiController]
    public class ValuesController : ControllerBase
    {
        private readonly IIdentityService _identityService;
        public ValuesController(IIdentityService identityService)
        {
            _identityService = identityService;
        }
        [HttpGet]
        [Authorize]
        public async Task<string> Get()
        {
            await Task.CompletedTask;
            return $"{_identityService.GetUserId()}:{_identityService.GetUserName()}";
        }

　　值得一提的是，我們可以根據 IHttpContextAccessor 以來註入到我們的Service或者Api中，它是一個當前請求的認證信息上下文，這將有利於你獲取用戶信息去做該做的事情。

public class IdentityService : IIdentityService
    {
        private readonly IHttpContextAccessor _context;
        public IdentityService(IHttpContextAccessor context)
        {
            _context = context;
        }
        public int GetUserId()
        {
            var nameId = _context.HttpContext.User.FindFirst("id");

            return nameId != null ? Convert.ToInt32(nameId.Value) : 0;
        }
        public string GetUserName()
        {
            return _context.HttpContext.User.FindFirst("name")?.Value;
        }
    }

　　在源碼中該類的定義如下，實際上我們可以看到只不過是判斷了當前的http上下文吧，所以我們得出，如果認證失敗，上下本信息也是空的。

public class HttpContextAccessor : IHttpContextAccessor
    {
        private static AsyncLocal<HttpContextHolder> _httpContextCurrent = new AsyncLocal<HttpContextHolder>();

        public HttpContext HttpContext
        {
            get
            {
                return  _httpContextCurrent.Value?.Context;
            }
            set
            {
                var holder = _httpContextCurrent.Value;
                if (holder != null)
                {
                    // Clear current HttpContext trapped in the AsyncLocals, as its done.
                    holder.Context = null;
                }

                if (value != null)
                {
                    // Use an object indirection to hold the HttpContext in the AsyncLocal,
                    // so it can be cleared in all ExecutionContexts when its cleared.
                    _httpContextCurrent.Value = new HttpContextHolder { Context = value };
                }
            }
        }

        private class HttpContextHolder
        {
            public HttpContext Context;
        }
    }

　　如果要通過js來測試代碼，您可以添加請求頭來進行認證，beforeSend是在請求之前的事件。

beforeSend : function(request) {
　　request.setRequestHeader("Authorization", sessionStorage.getItem("Authorization"));
}

　好了，今天就說到這,代碼地址在https://github.com/zaranetCore/DotNetCore_Jwt 中。