HTTP认证之基本认证——Basic（二）
导航
在HTTP认证之基本认证——Basic（一）中介绍了Basic认证的工作原理和流程，接下来就赶紧通过代码来实践一下，以下教程基于
ASP.NET Core WebApi框架。如有兴趣，可查看源码
一、准备工作
在开始之前，先把最基本的用户名密码校验逻辑准备好，只有一个认证方法：
public class UserService
{
public static User Authenticate(string userName, string password)
{
//用户名、密码不为空且相等时认证成功
if (!string.IsNullOrEmpty(userName)
&& !string.IsNullOrEmpty(password)
&& userName == password)
{
return new User()
{
UserName = userName,
Password = password
};
}
return null;
}
}
public class User
{
public string UserName { get; set; }
public string Password { get; set; }
}
二、编码
1.首先，先确定使用的认证方案为Basic，并提供默认的的Realm，
public const string AuthenticationScheme = "Basic";
public const string AuthenticationRealm = "Test Realm";
2.然后，解析HTTP Request获取到Authorization标头
private string GetCredentials(HttpRequest request)
{
string credentials = null;
string authorization = request.Headers[HeaderNames.Authorization];
//请求中存在 Authorization 标头且认证方式为 Basic
if (authorization?.StartsWith(AuthenticationScheme, StringComparison.OrdinalIgnoreCase) == true)
{
credentials = authorization.Substring(AuthenticationScheme.Length).Trim();
}
return credentials;
}
3.接着通过Base64逆向解码，得到要认证的用户名和密码。如果认证失败，则返回401 Unauthorized（不推荐返回403 Forbidden，因为这会导致用户在不刷新页面的情况下无法重新尝试认证）；如果认证成功，继续处理请求。
public class AuthorizationFilterAttribute : Attribute, IAuthorizationFilter
{
public void OnAuthorization(AuthorizationFilterContext context)
{
//请求允许匿名访问
if (context.Filters.Any(item => item is IAllowAnonymousFilter)) return;
var credentials = GetCredentials(context.HttpContext.Request);
//已获取到凭证
if(credentials != null)
{
try
{
//Base64逆向解码得到用户名和密码
credentials = Encoding.UTF8.GetString(Convert.FromBase64String(credentials));
var data = credentials.Split(':');
if (data.Length == 2)
{
var userName = data[0];
var password = data[1];
var user = UserService.Authenticate(userName, password);
//认证成功
if (user != null) return;
}
}
catch { }
}
//认证失败返回401
context.Result = new UnauthorizedResult();
//添加质询
AddChallenge(context.HttpContext.Response);
}
private void AddChallenge(HttpResponse response)
=> response.Headers.Append(HeaderNames.WWWAuthenticate, $"{ AuthenticationScheme } realm=\"{ AuthenticationRealm }\"");
}
4.最后，在需要认证的Action上加上过滤器[AuthorizationFilter]，大功告成！自己测试一下吧
三、封装为中间件
ASP.NET Core相比ASP.NET最大的突破大概就是插件配置化了——通过将各个功能封装成中间件，应用AOP的设计思想配置到应用程序中。以下封装采用Jwt Bearer封装规范（.Net Core 2.2 类库）。
Nuget: Microsoft.AspNetCore.Authentication
- 首先封装常量
public static class BasicDefaults
{
public const string AuthenticationScheme = "Basic";
}
2.然后封装Basic认证的Options，包括Realm和事件，继承自Microsoft.AspNetCore.Authentication.AuthenticationSchemeOptions。在事件内部，我们定义了认证行为和质询行为，分别用来校验认证是否通过和在HTTP Response中添加质询信息。我们将认证逻辑封装成一个委托，与认证行为独立开来，方便用户使用委托自定义认证规则。
public class BasicOptions : AuthenticationSchemeOptions
{
public string Realm { get; set; }
public new BasicEvents Events
{
get => (BasicEvents)base.Events;
set => base.Events = value;
}
}
public class BasicEvents
{
public Func<ValidateCredentialsContext, Task> OnValidateCredentials { get; set; } = context => Task.CompletedTask;
public Func<BasicChallengeContext, Task> OnChallenge { get; set; } = context => Task.CompletedTask;
public virtual Task ValidateCredentials(ValidateCredentialsContext context) => OnValidateCredentials(context);
public virtual Task Challenge(BasicChallengeContext context) => OnChallenge(context);
}
/// <summary>
/// 封装认证参数信息上下文
/// </summary>
public class ValidateCredentialsContext : ResultContext<BasicAuthenticationOptions>
{
public ValidateCredentialsContext(HttpContext context, AuthenticationScheme scheme, BasicAuthenticationOptions options) : base(context, scheme, options)
{
}
public string UserName { get; set; }
public string Password { get; set; }
}
public class BasicChallengeContext : PropertiesContext<BasicOptions>
{
public BasicChallengeContext(
HttpContext context,
AuthenticationScheme scheme,
BasicOptions options,
AuthenticationProperties properties)
: base(context, scheme, options, properties)
{
}
/// <summary>
/// 在认证期间出现的异常
/// </summary>
public Exception AuthenticateFailure { get; set; }
/// <summary>
/// 指定是否已被处理，如果已处理，则跳过默认认证逻辑
/// </summary>
public bool Handled { get; private set; }
/// <summary>
/// 跳过默认认证逻辑
/// </summary>
public void HandleResponse() => Handled = true;
}
3.接下来，就是对认证过程处理的封装了，需要继承自Microsoft.AspNetCore.Authentication.AuthenticationHandler
public class BasicHandler : AuthenticationHandler<BasicOptions>
{
public BasicHandler(IOptionsMonitor<BasicOptions> options, ILoggerFactory logger, UrlEncoder encoder, ISystemClock clock) : base(options, logger, encoder, clock)
{
}
protected new BasicEvents Events
{
get => (BasicEvents)base.Events;
set => base.Events = value;
}
/// <summary>
/// 确保创建的 Event 类型是 BasicEvents
/// </summary>
/// <returns></returns>
protected override Task<object> CreateEventsAsync() => Task.FromResult<object>(new BasicEvents());
protected override async Task<AuthenticateResult> HandleAuthenticateAsync()
{
var credentials = GetCredentials(Request);
if(credentials == null)
{
return AuthenticateResult.NoResult();
}
try
{
credentials = Encoding.UTF8.GetString(Convert.FromBase64String(credentials));
var data = credentials.Split(':');
if(data.Length != 2)
{
return AuthenticateResult.Fail("Invalid credentials, error format.");
}
var validateCredentialsContext = new ValidateCredentialsContext(Context, Scheme, Options)
{
UserName = data[0],
Password = data[1]
};
await Events.ValidateCredentials(validateCredentialsContext);
//认证通过
if(validateCredentialsContext.Result?.Succeeded == true)
{
var ticket = new AuthenticationTicket(validateCredentialsContext.Principal, Scheme.Name);
return AuthenticateResult.Success(ticket);
}
return AuthenticateResult.NoResult();
}
catch(FormatException)
{
return AuthenticateResult.Fail("Invalid credentials, error format.");
}
catch(Exception ex)
{
return AuthenticateResult.Fail(ex.Message);
}
}
protected override async Task HandleChallengeAsync(AuthenticationProperties properties)
{
var authResult = await HandleAuthenticateOnceSafeAsync();
var challengeContext = new BasicChallengeContext(Context, Scheme, Options, properties)
{
AuthenticateFailure = authResult?.Failure
};
await Events.Challenge(challengeContext);
//质询已处理
if (challengeContext.Handled) return;
var challengeValue = $"{ BasicDefaults.AuthenticationScheme } realm=\"{ Options.Realm }\"";
var error = challengeContext.AuthenticateFailure?.Message;
if(!string.IsNullOrWhiteSpace(error))
{
//将错误信息封装到内部
challengeValue += $" error=\"{ error }\"";
}
Response.StatusCode = (int)HttpStatusCode.Unauthorized;
Response.Headers.Append(HeaderNames.WWWAuthenticate, challengeValue);
}
private string GetCredentials(HttpRequest request)
{
string credentials = null;
string authorization = request.Headers[HeaderNames.Authorization];
//存在 Authorization 标头
if (authorization != null)
{
var scheme = BasicDefaults.AuthenticationScheme;
if (authorization.StartsWith(scheme, StringComparison.OrdinalIgnoreCase))
{
credentials = authorization.Substring(scheme.Length).Trim();
}
}
return credentials;
}
}
4.最后，就是要把封装的接口暴露给用户了，这里使用扩展方法的形式，虽然有4个方法，但实际上都是重载，是同一种行为。
public static class BasicExtensions
{
public static AuthenticationBuilder AddBasic(this AuthenticationBuilder builder)
=> builder.AddBasic(BasicDefaults.AuthenticationScheme, _ => { });
public static AuthenticationBuilder AddBasic(this AuthenticationBuilder builder, Action<BasicOptions> configureOptions)
=> builder.AddBasic(BasicDefaults.AuthenticationScheme, configureOptions);
public static AuthenticationBuilder AddBasic(this AuthenticationBuilder builder, string authenticationScheme, Action<BasicOptions> configureOptions)
=> builder.AddBasic(authenticationScheme, displayName: null, configureOptions: configureOptions);
public static AuthenticationBuilder AddBasic(this AuthenticationBuilder builder, string authenticationScheme, string displayName, Action<BasicOptions> configureOptions)
=> builder.AddScheme<BasicOptions, BasicHandler>(authenticationScheme, displayName, configureOptions);
}
5.Basic认证库已经封装好了，我们创建一个ASP.NET Core WebApi程序来测试一下吧。
//在 ConfigureServices 中配置认证中间件
public void ConfigureServices(IServiceCollection services)
{
services.AddAuthentication(BasicDefaults.AuthenticationScheme)
.AddBasic(options =>
{
options.Realm = "Test Realm";
options.Events = new BasicEvents
{
OnValidateCredentials = context =>
{
var user = UserService.Authenticate(context.UserName, context.Password);
if (user != null)
{
//将用户信息封装到HttpContext
var claim = new Claim(ClaimTypes.Name, context.UserName);
var identity = new ClaimsIdentity(BasicDefaults.AuthenticationScheme);
identity.AddClaim(claim);
context.Principal = new ClaimsPrincipal(identity);
context.Success();
}
return Task.CompletedTask;
}
};
});
}
//在 Configure 中启用认证中间件
public void Configure(IApplicationBuilder app, IHostingEnvironment env)
{
app.UseAuthentication();
}
对了，一定要记得为需要认证的Action添加[Authorize]特性，否则前面做的一切都是徒劳+_+
