如何在 Asp.Net Core 3.0 WebAPI 中启用 CORS

Question

我想通过 Asp.Net Core 3.0 API 项目启用 CORS。这是生成的基本 Asp.Net Core Api 模板。模板中的所有内容都是默认设置，除了我从文档中添加了 CORS 设置

public class Startup
 {
    public Startup(IConfiguration configuration)
    {
        Configuration = configuration;
    }

    public IConfiguration Configuration { get; }

    // This method gets called by the runtime. Use this method to add services to the container.
    public void ConfigureServices(IServiceCollection services)
    {
        services.AddControllers();
        services.AddCors(opt =>
        {
            var origins = Configuration
                .GetSection("AllowedHosts")
                .Get<string[]>();

            opt.AddPolicy("CorsPolicy", builder => builder
                    .WithOrigins(origins)
                    .AllowAnyMethod()
                    .AllowAnyHeader()
                    .Build());
        });
    }

    // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
    public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
    {
        if (env.IsDevelopment())
        {
            app.UseDeveloperExceptionPage();
        }

        app.UseHttpsRedirection();

        app.UseRouting();

        app.UseCors("CorsPolicy");
        app.UseAuthorization();

        app.UseEndpoints(endpoints =>
        {
            endpoints.MapControllers();
        });
    }
}

我应该如何设置才能在 .net core web api 中获取正确的 CORS？ 允许的主机是：

Answer 1

Cors 的优先顺序应该在添加控制器之前。应按照官方文档中的定义添加：https://docs.microsoft.com/en-us/aspnet/core/security/cors?view=aspnetcore-3.1

按照此代码：

public class Startup
 {
    public Startup(IConfiguration configuration)
    {
        Configuration = configuration;
    }

    public IConfiguration Configuration { get; }

    // This method gets called by the runtime. Use this method to add services to the container.
    public void ConfigureServices(IServiceCollection services)
    {            
        services.AddCors(options =>
        {
            options.AddPolicy("CorsPolicy",
                builder => builder.WithOrigins("http://localhost:4200", "http://localhost:44349")
                .AllowAnyMethod()
                .AllowAnyHeader();
                //.AllowCredentials());
        });

      services.AddControllers();
    }

    // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
    public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
    {
        if (env.IsDevelopment())
        {
            app.UseDeveloperExceptionPage();
        }

        app.UseHttpsRedirection();    
        app.UseRouting(); 

        app.UseCors("CorsPolicy");   
        app.UseAuthorization();

        app.UseEndpoints(endpoints =>
        {
            endpoints.MapControllers();
        });
    }
}

根据official documentation，必须注意的是：

指定 AllowAnyOrigin 和 AllowCredentials 是不安全的 配置，并可能导致跨站点请求伪造。 CORS 配置应用时服务返回无效的 CORS 响应 两种方法都可以。