Remotely/Server/Services/OtpProvider.cs

using Immense.RemoteControl.Shared.Helpers;
using Microsoft.Extensions.Caching.Memory;
using Remotely.Shared.Utilities;
using System;

namespace Remotely.Server.Services
{
    public interface IOtpProvider
    {
        bool Exists(string otp);
        string GetOtp(string deviceId);
        bool OtpMatchesDevice(string otp, string deviceId);
    }

    public class OtpProvider : IOtpProvider
    {
        private static readonly MemoryCache _otpCache = new(new MemoryCacheOptions());

        public bool Exists(string otp)
        {
            return _otpCache.TryGetValue(otp, out _);
        }

        public string GetOtp(string deviceId)
        {
            var otp = RandomGenerator.GenerateString(16);
            _otpCache.Set(otp, deviceId, TimeSpan.FromMinutes(1));
            return otp;
        }

        public bool OtpMatchesDevice(string otp, string deviceId)
        {
            if (_otpCache.TryGetValue(otp, out string cachedDevice) &&
                cachedDevice == deviceId)
            {
                return true;
            }
            return false;
        }
    }
}