在.NET Core中使用Jwt对API进行认证

　　在.NET Core中想给API进行安全认证，最简单的无非就是Jwt，悠然记得一年前写的Jwt Demo，现在拿回来改成.NET Core的，但是在编码上的改变并不大，因为Jwt已经足够强大了。在项目中分为 DotNetCore_Jwt_Server 以及 DotNetCore_Jwt_Client ，从名字就可以看出来是啥意思，博客园高手云集，我就不多诉说，这篇博客就当是一篇记录。

　　当然本案例是Server&Client双项目，如果你要合成自己发证的形式，那你就自己改下代码玩。

　　在Server层都会有分发Token的服务，在其中做了用户密码判断，随后根据 Claim 生成 jwtToken 的操作。

　　其生成Token的服务代码：

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)
        {
            //创建用户身份标识，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)
            };

            //创建令牌
            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;
        }
    }
}

在获取Token中我们依赖注入服务到控制器中，随后依赖它进行认证并且分发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);
        }
    }

 　　随后，我们又在项目配置文件中填写了几个字段，相关备注已注释，但值得说明的是有位朋友问我，服务器端生成的Token不需要保存吗，比如Redis或者是Session，其实Jwt Token是无状态的，他们之间的对比第一个是你的token解密出来的信息正确与否，第二部则是看看你 SecurityKey 是否正确，就这样他们的认证才会得出结果。

"JwtSetting": {
    "SecurityKey": "d0ecd23c-dfdb-4005-a2ea-0fea210c858a", // 密钥
    "Issuer": "jwtIssuertest", // 颁发者
    "Audience": "jwtAudiencetest", // 接收者
    "ExpireSeconds": 20000 // 过期时间
  }

　　随后我们需要DI两个接口以及初始化设置相关字段。

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

 　　在Client中，我一般会创建一个中间件用于接受认证结果，AspNetCore Jwt 源码中给我们提供了中间件，我们在进一步扩展，其源码定义如下：

/// <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);
　　}

 　　其该扩展会返回一个 AuthenticateResult 类型的结果，其定义部分是这样的，我们就可以将计就计，给他来个连环套。

 连环套直接接受 httpContext.AuthenticateAsync(JwtBearerDefaults.AuthenticationScheme)  返回回来的值，随后进行判断返回相应的Http响应码。

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);
            }
        }
    }

 　　当然你也得在Client中添加认证的一些设置，它和Server端的 IssuerSigningKey 一定要对应，否则认证失败。

        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() //允许任何来源的主机访问
                    .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)),
                       默认 300s
                       ClockSkew = TimeSpan.Zero
                   };
               });
            services.AddControllers();
        }

 　　随后，你就可以编写带需认证才可以访问的API了，如果认证失败则会返回401的错误响应。

　　[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，我们可以根据 IHttpContextAccessor 以来注入到我们的Service或者Api中，它是一个当前请求的认证信息上下文，这将有利于你获取用户信息去做该做的事情。

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;
        }
    }

　　在源码中该类的定义如下，实际上我们可以看到只不过是判断了当前的http上下文吧，所以我们得出，如果认证失败，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;
        }
    }

　　如果要通过js来测试代码，您可以添加请求头来进行认证，beforeSend是在请求之前的事件。

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

　好了，今天就说到这,代码地址在https://github.com/zaranetCore/DotNetCore_Jwt 中。