public class CspOptions
{
public List Defaults { get; set; } = new List();
public List Scripts { get; set; } = new List();
public List Styles { get; set; } = new List();
public List Images { get; set; } = new List();
public List Fonts { get; set; } = new List();
public List Media { get; set; } = new List();
}
开发一个中间件一定是需要一个构造器的，这将用于.net core 的注入到运行环境中。
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 Sources { get; set; } = new List();
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;
}
}
好了，我们创建一个中间件。
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 sources)
=> sources.Count > 0 ? $"{directive} {string.Join(" ", sources)}; " : "";
}
}
以及设置它的扩展方法。
namespace XSSDefenses.XSSDefenses.Extensions
{
public static class CspMiddlewareExtensions
{
public static IApplicationBuilder UseCsp(
this IApplicationBuilder app, Action builder)
{
var newBuilder = new CspOptionsBuilder();
builder(newBuilder);
var options = newBuilder.Build();
return app.UseMiddleware(options);
}
}
}
