ASP.NETCore编程实现基本认证

HTTP基本认证

在HTTP中，HTTP基本认证（Basic Authentication）是一种允许浏览器或其他客户端程序使用（用户名，口令）请求资源的身份验证方式，不要求cookie,session identifier、login page等标记或载体。   

• 所有浏览器据支持HTTP基本认证协议

• 基本身证原理不保证传输凭证的安全性，仅被based64编码，并没有encrypted或者hashed，一般部署在互信的内网，在公网上应用BA协议通常与https结合。

BA标准协议

BA协议的实施主要依靠约定的请求头/响应头， 典型的浏览器和服务器的BA认证流程：

① 浏览器请求应用了BA的网站，服务端响应一个401认证失败响应码，并写入 WWW-Authenticate 响应头，指示服务端支持BA协议。

HTTP/1.1 401 Unauthorized
WWW-Authenticate: Basic realm="our site"

或在初次请求时发送正确 Authorization 标头，从而避免被质询

② 客户端以based64(用户名:口令) 作为 Authorization 标头值，重新发送请求：

Authorization : Basic userid:password

认证的范围与realm相关，准确的realm由服务端定义，因为服务端可能有多个不同的realm.

> 浏览器客户端，对于 WWW- Authenticate 响应头弹出了口令输入窗。

BA编程实践

ASP.NET Core网站利用FileServerMiddleware将部分路径映射到文件资源，对该资源访问路径应用Http基本认证。

服务端实现BA认证

①  实现基本认证Handler：认证、无口令质询、质询失败逻辑

# ......
namespace EqidManager.Services
{
    public static class BasicAuthenticationScheme
    {
        public const string DefaultScheme = "Basic";
    }
    public class BasicAuthenticationOption:AuthenticationSchemeOptions
    {
        public string Realm { get; set; }
        public string UserName { get; set; }
        public string UserPwd { get; set; }
    }

    public class BasicAuthenticationHandler : AuthenticationHandler<BasicAuthenticationOption>
    {
        private readonly BasicAuthenticationOption authOptions;
        public BasicAuthenticationHandler(
            IOptionsMonitor<BasicAuthenticationOption> options,
            ILoggerFactory logger,
            UrlEncoder encoder,
            ISystemClock clock)
            : base(options, logger, encoder, clock)
        {
            authOptions = options.CurrentValue;
        }

        /// <summary>
        /// 认证逻辑
        /// </summary>
        protected override async Task<AuthenticateResult> HandleAuthenticateAsync()
        {
            if (!Request.Headers.ContainsKey("Authorization"))
                return AuthenticateResult.Fail("Missing Authorization Header");
            string username, password;
            try
            {
                var authHeader = AuthenticationHeaderValue.Parse(Request.Headers["Authorization"]);
                var credentialBytes = Convert.FromBase64String(authHeader.Parameter);
                var credentials = Encoding.UTF8.GetString(credentialBytes).Split(':');
                 username = credentials[0];
                 password = credentials[1];
                 var isValidUser= IsAuthorized(username,password);
                if(isValidUser== false)
                    return AuthenticateResult.Fail("Invalid username or password");
            }
            catch
                return AuthenticateResult.Fail("Invalid Authorization Header");
            var claims = new[] {
                new Claim(ClaimTypes.NameIdentifier,username),
                new Claim(ClaimTypes.Name,username),
            };
            var identity = new ClaimsIdentity(claims, Scheme.Name);
            var principal = new ClaimsPrincipal(identity);
            var ticket = new AuthenticationTicket(principal, Scheme.Name);
            return await Task.FromResult(AuthenticateResult.Success(ticket));
        }

        /// <summary>
        /// 质询
        /// </summary>
        protected override async Task HandleChallengeAsync(AuthenticationProperties properties)
        {
            Response.Headers["WWW-Authenticate"] = $"Basic realm=\"{Options.Realm}\"";
            await base.HandleChallengeAsync(properties);
        }

        /// <summary>
        /// 认证失败
        /// </summary>
        protected override async Task HandleForbiddenAsync(AuthenticationProperties properties)
        {
           await base.HandleForbiddenAsync(properties); 
        }
        private bool IsAuthorized(string username, string password)
        {
            return username.Equals(authOptions.UserName, StringComparison.InvariantCultureIgnoreCase)
                   && password.Equals(authOptions.UserPwd);
        }
    }
}

②  实现BasicAuthenticationMiddleware: 要求对HttpContext应用BA Scheme。

// HTTP基本认证Middleware
 public static class BasicAuthentication
 {
        public static void UseBasicAuthentication(this IApplicationBuilder app)
        {
            app.UseMiddleware<BasicAuthenticationMiddleware>();
        }
 }
public class BasicAuthenticationMiddleware
{
     private readonly RequestDelegate _next;
     private readonly ILogger _logger;
     public BasicAuthenticationMiddleware(RequestDelegate next, ILoggerFactory LoggerFactory)
     {
        _next = next;
        _logger = LoggerFactory.CreateLogger<BasicAuthenticationMiddleware>();
     }
     public async Task Invoke(HttpContext httpContext, IAuthenticationService authenticationService)
     {
       var authenticated = await authenticationService.AuthenticateAsync(httpContext, BasicAuthenticationScheme.DefaultScheme);
       _logger.LogInformation("Access Status：" + authenticated.Succeeded);
       if (!authenticated.Succeeded)
       {
           await authenticationService.ChallengeAsync(httpContext, BasicAuthenticationScheme.DefaultScheme, new AuthenticationProperties { });
           return;
       }
       await _next(httpContext);
     }
}

③ ASP. N ET  Core 添加BA Scheme , 为 待 认 证资源路径 启 用BA 中间件，注意这里使用UseWhen插入中间件。

services.AddAuthentication(BasicAuthenticationScheme.DefaultScheme)
                .AddScheme<BasicAuthenticationOption, BasicAuthenticationHandler>(BasicAuthenticationScheme.DefaultScheme,null);
app.UseWhen(
            predicate:x => x.Request.Path.StartsWithSegments(new PathString(_protectedResourceOption.Path)),
            configuration:appBuilder => { appBuilder.UseBasicAuthentication()；}
    );

现可在浏览器测试：

进一步思考？

以上是浏览器在 BA协议中的行为 ：可尝试 程序自动向服务端发起BA请求，需要的同学看博客园源码。

That's All .  BA认证是常见的基础认证协议，文章期待以清晰的方式传递协议原理和编程实现，要的同学阅读原文。

往期精选