ASP.NET Core中如何利用Csp標(biāo)頭對(duì)抗Xss攻擊

app.Use(async (ctx, next) =>
 {
 ctx.Response.Headers.Add("Content-Security-Policy",
 "default-src 'self'; report-uri /cspreport");
 await next();
 });

public class CspOptions
 {
 public List<string> Defaults { get; set; } = new List<string>();
 public List<string> Scripts { get; set; } = new List<string>();
 public List<string> Styles { get; set; } = new List<string>();
 public List<string> Images { get; set; } = new List<string>();
 public List<string> Fonts { get; set; } = new List<string>();
 public List<string> Media { get; set; } = new List<string>();
 }

public sealed class CspOptionsBuilder 
 { 
 private readonly CspOptions options = new CspOptions(); 
 
 internal CspOptionsBuilder() { } 
 
 public CspDirectiveBuilder Defaults { get; set; } = new CspDirectiveBuilder(); 
 public CspDirectiveBuilder Scripts { get; set; } = new CspDirectiveBuilder(); 
 public CspDirectiveBuilder Styles { get; set; } = new CspDirectiveBuilder(); 
 public CspDirectiveBuilder Images { get; set; } = new CspDirectiveBuilder(); 
 public CspDirectiveBuilder Fonts { get; set; } = new CspDirectiveBuilder(); 
 public CspDirectiveBuilder Media { get; set; } = new CspDirectiveBuilder(); 
 
 internal CspOptions Build() 
 { 
 this.options.Defaults = this.Defaults.Sources; 
 this.options.Scripts = this.Scripts.Sources; 
 this.options.Styles = this.Styles.Sources; 
 this.options.Images = this.Images.Sources; 
 this.options.Fonts = this.Fonts.Sources; 
 this.options.Media = this.Media.Sources; 
 return this.options; 
 } 
 } 
 
 public sealed class CspDirectiveBuilder 
 { 
 internal CspDirectiveBuilder() { } 
 
 internal List<string> Sources { get; set; } = new List<string>(); 
 
 public CspDirectiveBuilder AllowSelf() => Allow("'self'"); 
 public CspDirectiveBuilder AllowNone() => Allow("none"); 
 public CspDirectiveBuilder AllowAny() => Allow("*"); 
 
 public CspDirectiveBuilder Allow(string source) 
 { 
 this.Sources.Add(source); 
 return this; 
 } 
 }

namespace XSSDefenses.XSSDefenses.MiddlerWare
{
 public sealed class CspOptionMiddlerWare
 {
 private const string HEADER = "Content-Security-Policy";
 private readonly RequestDelegate next;
 private readonly CspOptions options;

 public CspOptionMiddlerWare(
 RequestDelegate next, CspOptions options)
 {
 this.next = next;
 this.options = options;
 }

 public async Task Invoke(HttpContext context)
 {
 context.Response.Headers.Add(HEADER, GetHeaderValue());
 await this.next(context);
 }

 private string GetHeaderValue()
 {
 var value = "";
 value += GetDirective("default-src", this.options.Defaults);
 value += GetDirective("script-src", this.options.Scripts);
 value += GetDirective("style-src", this.options.Styles);
 value += GetDirective("img-src", this.options.Images);
 value += GetDirective("font-src", this.options.Fonts);
 value += GetDirective("media-src", this.options.Media);
 return value;
 }
 private string GetDirective(string directive, List<string> sources)
 => sources.Count > 0 ? $"{directive} {string.Join(" ", sources)}; " : "";
 }
}

namespace XSSDefenses.XSSDefenses.Extensions
{
 public static class CspMiddlewareExtensions
 {
 public static IApplicationBuilder UseCsp(
 this IApplicationBuilder app, Action<CspOptionsBuilder> builder)
 {
 var newBuilder = new CspOptionsBuilder();
 builder(newBuilder);
 
 var options = newBuilder.Build();
 return app.UseMiddleware<CspOptionMiddlerWare>(options);
 }
 }
}

app.UseCsp(builder =>
 {
 builder.Styles.AllowSelf()
 .Allow(@"https://ajax.aspnetcdn.com/");
 });