WEBAPI AuthenticateAttribute 基于Basic 验证

如果验证失败，会返回 401 Unauthorized  

并且通过 response.Headers.WwwAuthenticate 头信息 获取  AuthenticationHeaderValue ，从而获取 验证规则，以及服务器传的值

比如 在程序中 给头信息赋值 credential，client.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Basic", Convert.ToBase64String(credential)); 

在验证 AuthenticateAsync 中通过 string credential = Encoding.Default.GetString(Convert.FromBase64String(headerValue.Parameter)); 来取值，进行判断

验证过后，过滤器会调用 ChallengeAsync 方法 ，获取验证的Principal，如果不为空且 验证有效，则不返回401 权限不通过提示

//IPrincipal user = context.ActionContext.ControllerContext.RequestContext.Principal;
IPrincipal user = Thread.CurrentPrincipal;

using System;
using System.Linq;
using System.Net;
using System.Net.Http;
using System.Net.Http.Headers;
using System.Text;

namespace Client
{
    class Program
    {
        static void Main(string[] args)
        {
            Console.OutputEncoding = Encoding.UTF8;
            HttpClient client = new HttpClient();
            HttpResponseMessage response = client.GetAsync("http://localhost:3721/api/demo").Result;
            if (response.StatusCode == HttpStatusCode.Unauthorized)
            {
                Console.WriteLine("认证失败");
                AuthenticationHeaderValue challenge = response.Headers.WwwAuthenticate.FirstOrDefault();
                if (challenge != null && challenge.Scheme == "Basic")
                {
                    Console.Write("输入用户名：");
                    string userName = Console.ReadLine().Trim();
                    Console.Write("输入密码：");
                    string password = Console.ReadLine().Trim();
                    byte[] credential = Encoding.Default.GetBytes(string.Format("{0}:{1}", userName, password));
                    client.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Basic", Convert.ToBase64String(credential));
                    response = client.GetAsync("http://localhost:3721/api/demo").Result;
                    string result = response.Content.ReadAsAsync().Result;
                    Console.WriteLine(result);
                }
            }
            Console.ReadLine();
        }
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Net.Http.Headers;
using System.Security.Principal;
using System.Text;
using System.Threading;
using System.Threading.Tasks;
using System.Web;
using System.Web.Http;
using System.Web.Http.Filters;
using System.Web.Http.Results;

namespace WebApi
{
    [AttributeUsage(AttributeTargets.Class | AttributeTargets.Method)]
    public class AuthenticateAttribute : FilterAttribute, IAuthenticationFilter
    {
        private static Dictionary userAccounters;
        static AuthenticateAttribute()
        {
            userAccounters = new Dictionary(StringComparer.OrdinalIgnoreCase);
            userAccounters.Add("Foo", "Password");
            userAccounters.Add("Bar", "Password");
            userAccounters.Add("Baz", "Password");
        }
        public Task AuthenticateAsync(HttpAuthenticationContext context, CancellationToken cancellationToken)
        {
            IPrincipal user = null;
            AuthenticationHeaderValue headerValue = context.Request.Headers.Authorization;
            if (null != headerValue && headerValue.Scheme == "Basic")
            {
                string credential = Encoding.Default.GetString(Convert.FromBase64String(headerValue.Parameter));
                string[] split = credential.Split(':');
                if (split.Length == 2)
                {
                    string userName = split[0];
                    string password;
                    if (userAccounters.TryGetValue(userName, out password))
                    {
                        if (password == split[1])
                        {
                            GenericIdentity identity = new GenericIdentity(userName);
                            user = new GenericPrincipal(identity, new string[0]);
                        }
                    }
                }
            }
            context.Principal = user;
            return Task.FromResult