详解ASP.NET Core Token认证

浏览: 81 发布日期: 2016-12-16 分类: asp.net

令牌认证(Token Authentication)已经成为单页应用(SPA)和移动应用事实上的标准。即使是传统的B/S应用也能利用其优点。优点很明白:极少的服务端数据管理、可扩展性、可以使用单独的认证服务器和应用服务器分离。

如果你对令牌(token)不是太了解,可以看这篇文章( overview of token authentication and JWTs)

令牌认证在asp.net core中集成。其中包括保护Bearer Jwt的路由功能,但是移除了生成token和验证token的部分,这些可以自定义或者使用第三方库来实现,得益于此,MVC和Web api项目可以使用令牌认证,而且很简单。下面将一步一步实现,代码可以在( 源码)下载。

ASP.NET Core令牌验证

首先,背景知识:认证令牌,例如JWTs,是通过http 认证头传递的,例如:

GET /foo
Authorization: Bearer [token]

令牌可以通过浏览器cookies。传递方式是header或者cookies取决于应用和实际情况,对于移动app,使用headers,对于web,推荐在html5 storage中使用cookies,来防止xss攻击。

asp.net core对jwts令牌的验证很简单,特别是你通过header传递。

1、生成 SecurityKey,这个例子,我生成对称密钥验证jwts通过HMAC-SHA256加密方式,在startup.cs中:

// secretKey contains a secret passphrase only your server knows
var secretKey = "mysupersecret_secretkey!123";
var signingKey = new SymmetricSecurityKey(Encoding.ASCII.GetBytes(secretKey));

验证 header中传递的JWTs

在 Startup.cs中,使用Microsoft.AspNetCore.Authentication.JwtBearer中的UseJwtBearerAuthentication 方法获取受保护的api或者mvc路由有效的jwt。

var tokenValidationParameters = new TokenValidationParameters
{
  // The signing key must match!
  ValidateIssuerSigningKey = true,
  IssuerSigningKey = signingKey,

  // Validate the JWT Issuer (iss) claim
  ValidateIssuer = true,
  ValidIssuer = "ExampleIssuer",

  // Validate the JWT Audience (aud) claim
  ValidateAudience = true,
  ValidAudience = "ExampleAudience",

  // Validate the token expiry
  ValidateLifetime = true,

  // If you want to allow a certain amount of clock drift, set that here:
  ClockSkew = TimeSpan.Zero
};

app.UseJwtBearerAuthentication(new JwtBearerOptions
{
  AutomaticAuthenticate = true,
  AutomaticChallenge = true,
  TokenValidationParameters = tokenValidationParameters
});

通过这个中间件,任何[Authorize]的请求都需要有效的jwt:

签名有效;

过期时间;

有效时间;

Issuer 声明等于“ExampleIssuer”

订阅者声明等于 “ExampleAudience”

如果不是合法的JWT,请求终止,issuer声明和订阅者声明不是必须的,它们用来标识应用和客户端。

在cookies中验证JWTs

ASP.NET Core中的cookies 认证不支持传递jwt。需要自定义实现 ISecureDataFormat接口的类。现在,你只是验证token,不是生成它们,只需要实现Unprotect方法,其他的交给System.IdentityModel.Tokens.Jwt.JwtSecurityTokenHandler这个类处理。

using System;
using System.IdentityModel.Tokens.Jwt;
using System.Security.Claims;
using Microsoft.AspNetCore.Authentication;
using Microsoft.AspNetCore.Http.Authentication;
using Microsoft.IdentityModel.Tokens;
 
namespace SimpleTokenProvider
{
  public class CustomJwtDataFormat : ISecureDataFormat<AuthenticationTicket>
  {
    private readonly string algorithm;
    private readonly TokenValidationParameters validationParameters;
 
    public CustomJwtDataFormat(string algorithm, TokenValidationParameters validationParameters)
    {
      this.algorithm = algorithm;
      this.validationParameters = validationParameters;
    }
 
    public AuthenticationTicket Unprotect(string protectedText)
      => Unprotect(protectedText, null);
 
    public AuthenticationTicket Unprotect(string protectedText, string purpose)
    {
      var handler = new JwtSecurityTokenHandler();
      ClaimsPrincipal principal = null;
      SecurityToken validToken = null;
 
      try
      {
        principal = handler.ValidateToken(protectedText, this.validationParameters, out validToken);
 
        var validJwt = validToken as JwtSecurityToken;
 
        if (validJwt == null)
        {
          throw new ArgumentException("Invalid JWT");
        }
 
        if (!validJwt.Header.Alg.Equals(algorithm, StringComparison.Ordinal))
        {
          throw new ArgumentException($"Algorithm must be '{algorithm}'");
        }
 
        // Additional custom validation of JWT claims here (if any)
      }
      catch (SecurityTokenValidationException)
      {
        return null;
      }
      catch (ArgumentException)
      {
        return null;
      }
 
      // Validation passed. Return a valid AuthenticationTicket:
      return new AuthenticationTicket(principal, new AuthenticationProperties(), "Cookie");
    }
 
    // This ISecureDataFormat implementation is decode-only
    public string Protect(AuthenticationTicket data)
    {
      throw new NotImplementedException();
    }
 
    public string Protect(AuthenticationTicket data, string purpose)
    {
      throw new NotImplementedException();
    }
  }
}

在startup.cs中调用

var tokenValidationParameters = new TokenValidationParameters
{
  // The signing key must match!
  ValidateIssuerSigningKey = true,
  IssuerSigningKey = signingKey,
 
  // Validate the JWT Issuer (iss) claim
  ValidateIssuer = true,
  ValidIssuer = "ExampleIssuer",
 
  // Validate the JWT Audience (aud) claim
  ValidateAudience = true,
  ValidAudience = "ExampleAudience",
 
  // Validate the token expiry
  ValidateLifetime = true,
 
  // If you want to allow a certain amount of clock drift, set that here:
  ClockSkew = TimeSpan.Zero
};
 
app.UseCookieAuthentication(new CookieAuthenticationOptions
{
  AutomaticAuthenticate = true,
  AutomaticChallenge = true,
  AuthenticationScheme = "Cookie",
  CookieName = "access_token",
  TicketDataFormat = new CustomJwtDataFormat(
    SecurityAlgorithms.HmacSha256,
    tokenValidationParameters)
});

如果请求中包含名为access_token的cookie验证为合法的JWT,这个请求就能返回正确的结果,如果需要,你可以加上额外的jwt chaims,或者复制jwt chaims到ClaimsPrincipal在CustomJwtDataFormat.Unprotect方法中,上面是验证token,下面将在asp.net core中生成token。

ASP.NET Core生成Tokens

在asp.net 4.5中,这个UseOAuthAuthorizationServer中间件可以轻松的生成tokens,但是在asp.net core取消了,下面写一个简单的token生成中间件,最后,有几个现成解决方案的链接,供你选择。

简单的token生成节点

首先,生成 POCO保存中间件的选项. 生成类:TokenProviderOptions.cs

using System;
using Microsoft.IdentityModel.Tokens;
 
namespace SimpleTokenProvider
{
  public class TokenProviderOptions
  {
    public string Path { get; set; } = "/token";
 
    public string Issuer { get; set; }
 
    public string Audience { get; set; }
 
    public TimeSpan Expiration { get; set; } = TimeSpan.FromMinutes(5);
 
    public SigningCredentials SigningCredentials { get; set; }
  }
}

现在自己添加一个中间件,asp.net core 的中间件类一般是这样的:

using System.IdentityModel.Tokens.Jwt;
using System.Security.Claims;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Http;
using Microsoft.Extensions.Options;
using Newtonsoft.Json;

namespace SimpleTokenProvider
{
  public class TokenProviderMiddleware
  {
    private readonly RequestDelegate _next;
    private readonly TokenProviderOptions _options;

    public TokenProviderMiddleware(
      RequestDelegate next,
      IOptions<TokenProviderOptions> options)
    {
      _next = next;
      _options = options.Value;
    }

    public Task Invoke(HttpContext context)
    {
      // If the request path doesn't match, skip
      if (!context.Request.Path.Equals(_options.Path, StringComparison.Ordinal))
      {
        return _next(context);
      }

      // Request must be POST with Content-Type: application/x-www-form-urlencoded
      if (!context.Request.Method.Equals("POST")
        || !context.Request.HasFormContentType)
      {
        context.Response.StatusCode = 400;
        return context.Response.WriteAsync("Bad request.");
      }

      return GenerateToken(context);
    }
  }
}

这个中间件类接受TokenProviderOptions作为参数,当有请求且请求路径是设置的路径(token或者api/token),Invoke方法执行,token节点只对 POST请求而且包括form-urlencoded内容类型(Content-Type: application/x-www-form-urlencoded),因此调用之前需要检查下内容类型。

最重要的是GenerateToken,这个方法需要验证用户的身份,生成jwt,传回jwt:

private async Task GenerateToken(HttpContext context)
{
  var username = context.Request.Form["username"];
  var password = context.Request.Form["password"];
 
  var identity = await GetIdentity(username, password);
  if (identity == null)
  {
    context.Response.StatusCode = 400;
    await context.Response.WriteAsync("Invalid username or password.");
    return;
  }
 
  var now = DateTime.UtcNow;
 
  // Specifically add the jti (random nonce), iat (issued timestamp), and sub (subject/user) claims.
  // You can add other claims here, if you want:
  var claims = new Claim[]
  {
    new Claim(JwtRegisteredClaimNames.Sub, username),
    new Claim(JwtRegisteredClaimNames.Jti, Guid.NewGuid().ToString()),
    new Claim(JwtRegisteredClaimNames.Iat, ToUnixEpochDate(now).ToString(), ClaimValueTypes.Integer64)
  };
 
  // Create the JWT and write it to a string
  var jwt = new JwtSecurityToken(
    issuer: _options.Issuer,
    audience: _options.Audience,
    claims: claims,
    notBefore: now,
    expires: now.Add(_options.Expiration),
    signingCredentials: _options.SigningCredentials);
  var encodedJwt = new JwtSecurityTokenHandler().WriteToken(jwt);
 
  var response = new
  {
    access_token = encodedJwt,
    expires_in = (int)_options.Expiration.TotalSeconds
  };
 
  // Serialize and return the response
  context.Response.ContentType = "application/json";
  await context.Response.WriteAsync(JsonConvert.SerializeObject(response, new JsonSerializerSettings { Formatting = Formatting.Indented }));
}

大部分代码都很官方,JwtSecurityToken 类生成jwt,JwtSecurityTokenHandler将jwt编码,你可以在claims中添加任何chaims。验证用户身份只是简单的验证,实际情况肯定不是这样的,你可以集成 identity framework或者其他的,对于这个实例只是简单的硬编码:

private Task<ClaimsIdentity> GetIdentity(string username, string password)
{
  // DON'T do this in production, obviously!
  if (username == "TEST" && password == "TEST123")
  {
    return Task.FromResult(new ClaimsIdentity(new System.Security.Principal.GenericIdentity(username, "Token"), new Claim[] { }));
  }
 
  // Credentials are invalid, or account doesn't exist
  return Task.FromResult<ClaimsIdentity>(null);
}

添加一个将DateTime生成timestamp的方法:

public static long ToUnixEpochDate(DateTime date)
  => (long)Math.Round((date.ToUniversalTime() - new DateTimeOffset(1970, 1, 1, 0, 0, 0, TimeSpan.Zero)).TotalSeconds);

现在,你可以将这个中间件添加到startup.cs中了:

using System.Text;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Logging;
using Microsoft.Extensions.Options;
using Microsoft.IdentityModel.Tokens;
 
namespace SimpleTokenProvider
{
  public partial class Startup
  {
    public Startup(IHostingEnvironment env)
    {
      var builder = new ConfigurationBuilder()
        .AddJsonFile("appsettings.json", optional: true);
      Configuration = builder.Build();
    }
 
    public IConfigurationRoot Configuration { get; set; }
 
    public void ConfigureServices(IServiceCollection services)
    {
      services.AddMvc();
    }
 
    // The secret key every token will be signed with.
    // In production, you should store this securely in environment variables
    // or a key management tool. Don't hardcode this into your application!
    private static readonly string secretKey = "mysupersecret_secretkey!123";
 
    public void Configure(IApplicationBuilder app, IHostingEnvironment env, ILoggerFactory loggerFactory)
    {
      loggerFactory.AddConsole(LogLevel.Debug);
      loggerFactory.AddDebug();
 
      app.UseStaticFiles();
 
      // Add JWT generation endpoint:
      var signingKey = new SymmetricSecurityKey(Encoding.ASCII.GetBytes(secretKey));
      var options = new TokenProviderOptions
      {
        Audience = "ExampleAudience",
        Issuer = "ExampleIssuer",
        SigningCredentials = new SigningCredentials(signingKey, SecurityAlgorithms.HmacSha256),
      };
 
      app.UseMiddleware<TokenProviderMiddleware>(Options.Create(options));
 
      app.UseMvc();
    }
  }
}

测试一下,推荐使用chrome 的postman:

POST /token
Content-Type: application/x-www-form-urlencoded
username=TEST&password=TEST123

结果:
OK

Content-Type: application/json
 
{
  "access_token": "eyJhb...",
  "expires_in": 300
}

你可以使用jwt工具查看生成的jwt内容。如果开发的是移动应用或者单页应用,你可以在后续请求的header中存储jwt,如果你需要在cookies中存储的话,你需要对代码修改一下,需要将返回的jwt字符串添加到cookie中。
测试下:

其他方案

下面是比较成熟的项目,可以在实际项目中使用:

  • AspNet.Security.OpenIdConnect.Server C ASP.NET 4.x的验证中间件。
  • OpenIddict C 在identity上添加OpenId验证。
  • IdentityServer4 C .NET Core认证中间件(现在测试版本)。

下面的文章可以让你更加的了解认证:

  • Overview of Token Authentication Features
  • How Token Authentication Works in Stormpath
  • Use JWTs the Right Way!

以上就是本文的全部内容,希望对大家的学习有所帮助,也希望大家多多支持脚本之家。

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