Importing a bit of code from Katana on CodePlex

SystemWebCookieManager.cs

 //stick this in public void ConfigureAuth(IAppBuilder app)
      app.UseCookieAuthentication(new CookieAuthenticationOptions
                {
                    // ...
                    CookieManager = new SystemWebCookieManager()
                });
    
    //And create this class elsewhere:
    public class SystemWebCookieManager : ICookieManager
        {
            public string GetRequestCookie(IOwinContext context, string key)
            {
                if (context == null)
                {
                    throw new ArgumentNullException("context");
                }
    
                var webContext = context.Get<HttpContextBase>(typeof(HttpContextBase).FullName);
                var cookie = webContext.Request.Cookies[key];
                return cookie == null ? null : cookie.Value;
            }
    
            public void AppendResponseCookie(IOwinContext context, string key, string value, CookieOptions options)
            {
                if (context == null)
                {
                    throw new ArgumentNullException("context");
                }
                if (options == null)
                {
                    throw new ArgumentNullException("options");
                }
    
                var webContext = context.Get<HttpContextBase>(typeof(HttpContextBase).FullName);
    
                bool domainHasValue = !string.IsNullOrEmpty(options.Domain);
                bool pathHasValue = !string.IsNullOrEmpty(options.Path);
                bool expiresHasValue = options.Expires.HasValue;
                
                var cookie = new HttpCookie(key, value);
                if (domainHasValue)
                {
                    cookie.Domain = options.Domain;
                }
                if (pathHasValue)
                {
                    cookie.Path = options.Path;
                }
                if (expiresHasValue)
                {
                    cookie.Expires = options.Expires.Value;
                }
                if (options.Secure)
                {
                    cookie.Secure = true;
                }
                if (options.HttpOnly)
                {
                    cookie.HttpOnly = true;
                }
    
                webContext.Response.AppendCookie(cookie);
            }
    
            public void DeleteCookie(IOwinContext context, string key, CookieOptions options)
            {
                if (context == null)
                {
                    throw new ArgumentNullException("context");
                }
                if (options == null)
                {
                    throw new ArgumentNullException("options");
                }
                
                AppendResponseCookie(
                    context,
                    key,
                    string.Empty,
                    new CookieOptions
                    {
                        Path = options.Path,
                        Domain = options.Domain,
                        Expires = new DateTime(1970, 1, 1, 0, 0, 0, DateTimeKind.Utc),
                    });
            }
        }