server/src/Core/IdentityServer/DistributedCacheCookieManager.cs

using System;
using System.Text;
using Microsoft.AspNetCore.Authentication.Cookies;
using Microsoft.AspNetCore.Http;
using Microsoft.Extensions.Caching.Distributed;
using Microsoft.Extensions.DependencyInjection;

namespace Bit.Core.IdentityServer
{
    public class DistributedCacheCookieManager : ICookieManager
    {
        private readonly ChunkingCookieManager _cookieManager;

        public DistributedCacheCookieManager()
        {
            _cookieManager = new ChunkingCookieManager();
        }

        private string CacheKeyPrefix => "cookie-data";

        public void AppendResponseCookie(HttpContext context, string key, string value, CookieOptions options)
        {
            var id = Guid.NewGuid().ToString();
            var cacheKey = GetKey(key, id);
            
            var expiresUtc = options.Expires ?? DateTimeOffset.UtcNow.AddMinutes(15);
            var cacheOptions = new DistributedCacheEntryOptions()
                .SetAbsoluteExpiration(expiresUtc);

            var data = Encoding.UTF8.GetBytes(value);

            var cache = GetCache(context);
            cache.Set(cacheKey, data, cacheOptions);

            // Write the cookie with the identifier as the body
            _cookieManager.AppendResponseCookie(context, key, id, options);
        }

        public void DeleteCookie(HttpContext context, string key, CookieOptions options)
        {
            _cookieManager.DeleteCookie(context, key, options);
            var id = GetId(context, key);
            if (!string.IsNullOrWhiteSpace(id))
            {
                var cacheKey = GetKey(key, id);
                GetCache(context).Remove(cacheKey);
            }
        }

        public string GetRequestCookie(HttpContext context, string key)
        {
            var id = GetId(context, key);
            if (string.IsNullOrWhiteSpace(id))
            {
                return null;
            }
            var cacheKey = GetKey(key, id);
            return GetCache(context).GetString(cacheKey);
        }

        private IDistributedCache GetCache(HttpContext context) =>
            context.RequestServices.GetRequiredService<IDistributedCache>();

        private string GetKey(string key, string id) => $"{CacheKeyPrefix}-{key}-{id}";

        private string GetId(HttpContext context, string key) =>
            context.Request.Cookies.ContainsKey(key) ?
            context.Request.Cookies[key] : null;
    }
}