Asp.Net Core5 之 JWT

通用JWT工作流

1. 用户发送凭证给网站登录.
2. 网站后端验证凭证, 声明合适的声明然后生成JWT并返回给用户.
3. 用户获取JWT直到过期, 在后继的请求中奖JWT发送给网站.
4. 网站验证JWT后决定资源是是否可访问.

配置

1. .NET Core提供了NuGet 包可以直接安装, 省去很多工作. Microsoft.AspNetCore.Authentication.JwtBearer
2. 两种使用方法:

1. app.UseJwtBearerAuthentication()
2. services.AddJwtBearer()

3. 在Startup.cs中进行注册服务和使用.

public void ConfigureServices(IServiceCollection services)
{
    var jwtTokenConfig = Configuration.GetSection("jwtTokenConfig").Get<JwtTokenConfig>();
    services.AddSingleton(jwtTokenConfig);
    services.AddAuthentication(x =>
    {
        x.DefaultAuthenticateScheme = JwtBearerDefaults.AuthenticationScheme;
        x.DefaultChallengeScheme = JwtBearerDefaults.AuthenticationScheme;
    }).AddJwtBearer(x =>
    {
        x.RequireHttpsMetadata = true;// default is true 为metadata或者authority验证请求https
        x.SaveToken = true;// default is true, 将JWT保存到当前的HttpContext, 以至于可以获取它通过await HttpContext.GetTokenAsync("Bearer","access_token"); 如果想设置为false, 将token保存在claim中, 然后获取通过User.FindFirst("access_token")?.value.
        x.TokenValidationParameters = new TokenValidationParameters
        {// 设置参数用于验证身份token
            ValidateIssuer = true,
            ValidIssuer = jwtTokenConfig.Issuer,
            ValidateIssuerSigningKey = true,
            IssuerSigningKey = new SymmetricSecurityKey(Encoding.ASCII.GetBytes(jwtTokenConfig.Secret)),
            ValidAudience = jwtTokenConfig.Audience,
            ValidateAudience = true,
            ValidateLifetime = true,
            ClockSkew = TimeSpan.FromMinutes(1)//对token过期时间验证的允许时间
        };
    });
    // ...
}

4. JWTHelper

public class JwtAuthManager : IJwtAuthManager
{
    public IImmutableDictionary<string, RefreshToken> UsersRefreshTokensReadOnlyDictionary => _usersRefreshTokens.ToImmutableDictionary();
    private readonly ConcurrentDictionary<string, RefreshToken> _usersRefreshTokens;  // can store in a database or a distributed cache
    private readonly JwtTokenConfig _jwtTokenConfig;
    private readonly byte[] _secret;

    public JwtAuthManager(JwtTokenConfig jwtTokenConfig)
    {
        _jwtTokenConfig = jwtTokenConfig;
        _usersRefreshTokens = new ConcurrentDictionary<string, RefreshToken>();
        _secret = Encoding.ASCII.GetBytes(jwtTokenConfig.Secret);
    }

    public JwtAuthResult GenerateTokens(string username, Claim[] claims, DateTime now)
    {
        var shouldAddAudienceClaim = string.IsNullOrWhiteSpace(claims?.FirstOrDefault(x => x.Type == JwtRegisteredClaimNames.Aud)?.Value);
        var jwtToken = new JwtSecurityToken(
            _jwtTokenConfig.Issuer,
            shouldAddAudienceClaim ? _jwtTokenConfig.Audience : string.Empty,
            claims,
            expires: now.AddMinutes(_jwtTokenConfig.AccessTokenExpiration),
            signingCredentials: new SigningCredentials(new SymmetricSecurityKey(_secret), SecurityAlgorithms.HmacSha256Signature));
        var accessToken = new JwtSecurityTokenHandler().WriteToken(jwtToken);

        var refreshToken = new RefreshToken
        {
            UserName = username,
            TokenString = GenerateRefreshTokenString(),
            ExpireAt = now.AddMinutes(_jwtTokenConfig.RefreshTokenExpiration)
        };
        _usersRefreshTokens.AddOrUpdate(refreshToken.TokenString, refreshToken, (s, t) => refreshToken);

        return new JwtAuthResult
        {
            AccessToken = accessToken,
            RefreshToken = refreshToken
        };
    }

    private static string GenerateRefreshTokenString()
    {
        var randomNumber = new byte[32];
        using var randomNumberGenerator = RandomNumberGenerator.Create();
        randomNumberGenerator.GetBytes(randomNumber);
        return Convert.ToBase64String(randomNumber);
    }
}

5. 如果想要通过HttpContext.User.FindFirstValue(""), 需要在容器中注册services.AddSingleton<IHttpContextAccessor, HttpContextAccessor>();

6. 通过写一个静态的扩展方法进行获取服务:

namespace SuperCosmos.Core.Utilities
{
    public static class HttpContext
    {
        private static IHttpContextAccessor _accessor;

 
        public static Microsoft.AspNetCore.Http.HttpContext Current => _accessor.HttpContext;


        internal static void Configure(IHttpContextAccessor accessor)
        {
            _accessor = accessor;
        }
    }
}


public static IApplicationBuilder UseStaticHttpContext(this IApplicationBuilder app)
        {
            var httpContextAccessor = app.ApplicationServices.GetRequiredService<IHttpContextAccessor>();
           Utilities.HttpContext.Configure(httpContextAccessor);
            return app;
        }

6. 验证通过后通过这种方式获取JWT的信息:

Context.User.FindFirstValue(JwtRegisteredClaimNames.Jti)
                     ?? Context.User.FindFirstValue(ClaimTypes.NameIdentifier);

7. 需要注意:
   1. 在控制器上需要添加[Authorize]的Attribute, 否则不生效.
   2. 前端请求服务是header需要添加Bearer: header["Authorization"]="Bearer "+token, 注意: Bearer后面有一个空格.

8. 在Startup.cs中需要使用:

  public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
{
      ...
   app.UseAuthentication();
   app.UseAuthorization();
      ...
}

9. 不建议通过token传递敏感信息, key加密.
10. 为了开发, 减少冗余, 可将JWT的属性进行封装, 将一些参数放在appsetting.json中, 通过Option方式动态获取, 使得项目更为灵活.