Audacia.SecureHeadersMiddleware is a wrapper around the NetEscapades.AspNetCore.SecurityHeaders library. It uses middleware to add security-related headers, such as a Content Security Policy.

There are two IApplicationBuilder extension methods to add the recommended security headers; the one to use depends on the type of project:

• UseApiSecurityHeaders for API projects
• UseIdentitySecurityHeaders for MVC projects that implement an authentication provider such as IdentityServer or OpenIddict

Both methods return a HeaderPolicyCollection, which can be used to customize the headers. For example, suppose you want to use the default API headers, and also add a bespoke header called My-Security-Header, this can be achieved as follows:

app.UseApiSecurityHeaders().AddCustomHeader("My-Security-Header", "header value");

ASP.NET Core includes a [ResponseCache] attribute that configures caching headers at the controller or action level. This will not be respected when using app.UseApiSecurityHeaders().

To make the middleware respect this attribute, the UseApiSecurityHeaders middleware can be conditionally applied with app.UseWhen().

• UseApiSecurityHeaders can be used for endpoints without a [ResponseCache] attribute
• AddDefaultSecurityHeaders from NetEscapades.AspNetCore.SecurityHeaders can be used for endpoints with a [ResponseCache] attribute

/// <summary>
/// Use middleware to add security headers with custom support for the <see cref="ResponseCacheAttribute"/>.
/// </summary>
internal static IApplicationBuilder UseCustomSecurityHeaders(this IApplicationBuilder app)
{
    // When the endpoint has a ResponseCacheAttribute, only apply the default headers
    app.UseWhen(
        ctx => ctx.IsResponseCachedEndpoint(),
        builder =>
        {
            var headerPolicyCollection = new HeaderPolicyCollection().AddDefaultSecurityHeaders();
            builder.UseSecurityHeaders(headerPolicyCollection);
        });

    // For all other endpoints, apply the Audacia API headers which include cache prevention
    app.UseWhen(
        ctx => !ctx.IsResponseCachedEndpoint(),
        builder => builder.UseApiSecurityHeaders());

    return app;
}

/// <summary>
/// Checks if the endpoint in the context has the <see cref="ResponseCacheAttribute"/>.
/// </summary>
private static bool IsResponseCachedEndpoint(this HttpContext context)
{
    var endpoint = context.GetEndpoint();

    var filter = endpoint?.Metadata.GetMetadata<ResponseCacheAttribute>();

    return filter is not null;
}

...

// Must call this after app.UseRouting()
app.UseCustomSecurityHeaders();

The Audacia.SecureHeadersMiddleware repository change history can be found in this changelog:

We welcome contributions! Please feel free to check our Contribution Guidlines for feature requests, issue reporting and guidelines.