Add HMAC support to Swagger

SwaggerExtensions.cs

using Microsoft.OpenApi.Models;
using Swashbuckle.AspNetCore.SwaggerGen;
using Swashbuckle.AspNetCore.SwaggerUI;

public static void AddSwaggerHMACSupport(this IServiceCollection services)
{
    const string HmacSecretHeaderName = "X-HMAC-Secret";

    services.Configure<SwaggerUIOptions>(opts =>
    {
        // Pull in crypto-js to handle request hashing
        opts.InjectJavascript("https://cdnjs.cloudflare.com/ajax/libs/crypto-js/4.1.1/crypto-js.min.js");
        // Request handler to
        // - pull the secret out of the specified header and remove that header from the request
        // - Set the request timestamp in a header
        // - Sign the request using HMAC
        opts.UseRequestInterceptor(
            @"(req) => { if(req.url.endsWith('swagger.json')) return req; var now = Date.now(); req.headers['X-Request-Timestamp'] = now; var secret = req.headers['"+ HmacSecretHeaderName+"']; delete req.headers['"+ HmacSecretHeaderName+"']; var payload=req.method.toUpperCase()+req.url+now+req.body; var hmac = CryptoJS.algo.HMAC.create(CryptoJS.algo.SHA256, secret); hmac.update(payload); req.headers['X-Request-Signature'] = CryptoJS.enc.Base64.stringify(hmac.finalize()); return req; }");
    });

    services.Configure<SwaggerGenOptions>(options =>
    {
        options.AddSecurityDefinition("HMAC",
            new OpenApiSecurityScheme
            {
                Description = "HMAC request signing",
                Type = SecuritySchemeType.ApiKey,
                Name = HmacSecretHeaderName, // this header is removed by the request interceptor.
                In = ParameterLocation.Header
            });
        options.AddSecurityRequirement(new OpenApiSecurityRequirement
        {
            {
                new OpenApiSecurityScheme
                {
                    Reference = new OpenApiReference { Type = ReferenceType.SecurityScheme, Id = "HMAC" }
                },
                new string[] { }
            }
        });
    });
}