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。