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");}catchreturn 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Middlewarepublic 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.NET 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

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实例解读Docker Swarm 
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