jellyfin/Emby.Server.Implementations/QuickConnect/QuickConnectManager.cs

using System;
using System.Collections.Concurrent;
using System.Collections.Generic;
using System.Globalization;
using System.Linq;
using System.Security.Cryptography;
using MediaBrowser.Controller;
using MediaBrowser.Controller.Configuration;
using MediaBrowser.Controller.Net;
using MediaBrowser.Controller.QuickConnect;
using MediaBrowser.Controller.Security;
using MediaBrowser.Model.QuickConnect;
using MediaBrowser.Model.Services;
using MediaBrowser.Common;
using Microsoft.Extensions.Logging;
using MediaBrowser.Common.Extensions;

namespace Emby.Server.Implementations.QuickConnect
{
    /// <summary>
    /// Quick connect implementation.
    /// </summary>
    public class QuickConnectManager : IQuickConnect, IDisposable
    {
        private readonly RNGCryptoServiceProvider _rng = new RNGCryptoServiceProvider();
        private readonly ConcurrentDictionary<string, QuickConnectResult> _currentRequests = new ConcurrentDictionary<string, QuickConnectResult>();

        private readonly IServerConfigurationManager _config;
        private readonly ILogger<QuickConnectManager> _logger;
        private readonly IAuthenticationRepository _authenticationRepository;
        private readonly IAuthorizationContext _authContext;
        private readonly IServerApplicationHost _appHost;

        /// <summary>
        /// Initializes a new instance of the <see cref="QuickConnectManager"/> class.
        /// Should only be called at server startup when a singleton is created.
        /// </summary>
        /// <param name="config">Configuration.</param>
        /// <param name="logger">Logger.</param>
        /// <param name="appHost">Application host.</param>
        /// <param name="authContext">Authentication context.</param>
        /// <param name="authenticationRepository">Authentication repository.</param>
        public QuickConnectManager(
            IServerConfigurationManager config,
            ILogger<QuickConnectManager> logger,
            IServerApplicationHost appHost,
            IAuthorizationContext authContext,
            IAuthenticationRepository authenticationRepository)
        {
            _config = config;
            _logger = logger;
            _appHost = appHost;
            _authContext = authContext;
            _authenticationRepository = authenticationRepository;

            ReloadConfiguration();
        }

        /// <inheritdoc/>
        public int CodeLength { get; set; } = 6;

        /// <inheritdoc/>
        public string TokenNamePrefix { get; set; } = "QuickConnect-";

        /// <inheritdoc/>
        public QuickConnectState State { get; private set; } = QuickConnectState.Unavailable;

        /// <inheritdoc/>
        public int Timeout { get; set; } = 5;

        private DateTime DateActivated { get; set; }

        /// <inheritdoc/>
        public void AssertActive()
        {
            if (State != QuickConnectState.Active)
            {
                throw new InvalidOperationException("Quick connect is not active on this server");
            }
        }

        /// <inheritdoc/>
        public QuickConnectResult Activate()
        {
            SetEnabled(QuickConnectState.Active);

            DateActivated = DateTime.Now;

            return new QuickConnectResult();
        }

        /// <inheritdoc/>
        public void SetEnabled(QuickConnectState newState)
        {
            _logger.LogDebug("Changed quick connect state from {0} to {1}", State, newState);

            ExpireRequests(true);

            State = newState;
            _config.Configuration.QuickConnectAvailable = newState == QuickConnectState.Available || newState == QuickConnectState.Active;
            _config.SaveConfiguration();

            _logger.LogDebug("Configuration saved");
        }

        /// <inheritdoc/>
        public QuickConnectResult TryConnect(string friendlyName)
        {
            ExpireRequests();

            if (State != QuickConnectState.Active)
            {
                _logger.LogDebug("Refusing quick connect initiation request, current state is {0}", State);

                return new QuickConnectResult()
                {
                    Error = "Quick connect is not active on this server"
                };
            }

            _logger.LogDebug("Got new quick connect request from {friendlyName}", friendlyName);

            var code = GenerateCode();
            var result = new QuickConnectResult()
            {
                Secret = GenerateSecureRandom(),
                FriendlyName = friendlyName,
                DateAdded = DateTime.Now,
                Code = code
            };

            _currentRequests[code] = result;
            return result;
        }

        /// <inheritdoc/>
        public QuickConnectResult CheckRequestStatus(string secret)
        {
            ExpireRequests();
            AssertActive();

            string code = _currentRequests.Where(x => x.Value.Secret == secret).Select(x => x.Value.Code).DefaultIfEmpty(string.Empty).First();

            if (!_currentRequests.TryGetValue(code, out QuickConnectResult result))
            {
                throw new ResourceNotFoundException("Unable to find request with provided secret");
            }

            return result;
        }

        public List<QuickConnectResultDto> GetCurrentRequests()
        {
            return GetCurrentRequestsInternal().Select(x => (QuickConnectResultDto)x).ToList();
        }

        /// <inheritdoc/>
        public List<QuickConnectResult> GetCurrentRequestsInternal()
        {
            ExpireRequests();
            AssertActive();
            return _currentRequests.Values.ToList();
        }

        /// <inheritdoc/>
        public string GenerateCode()
        {
            int min = (int)Math.Pow(10, CodeLength - 1);
            int max = (int)Math.Pow(10, CodeLength);

            uint scale = uint.MaxValue;
            while (scale == uint.MaxValue)
            {
                byte[] raw = new byte[4];
                _rng.GetBytes(raw);
                scale = BitConverter.ToUInt32(raw, 0);
            }

            int code = (int)(min + ((max - min) * (scale / (double)uint.MaxValue)));
            return code.ToString(CultureInfo.InvariantCulture);
        }

        /// <inheritdoc/>
        public bool AuthorizeRequest(IRequest request, string code)
        {
            ExpireRequests();
            AssertActive();

            var auth = _authContext.GetAuthorizationInfo(request);

            if (!_currentRequests.TryGetValue(code, out QuickConnectResult result))
            {
                throw new ResourceNotFoundException("Unable to find request");
            }

            if (result.Authenticated)
            {
                throw new InvalidOperationException("Request is already authorized");
            }

            result.Authentication = Guid.NewGuid().ToString("N", CultureInfo.InvariantCulture);

            // Change the time on the request so it expires one minute into the future. It can't expire immediately as otherwise some clients wouldn't ever see that they have been authenticated.
            var added = result.DateAdded ?? DateTime.Now.Subtract(new TimeSpan(0, Timeout, 0));
            result.DateAdded = added.Subtract(new TimeSpan(0, Timeout - 1, 0));

            _authenticationRepository.Create(new AuthenticationInfo
            {
                AppName = TokenNamePrefix + result.FriendlyName,
                AccessToken = result.Authentication,
                DateCreated = DateTime.UtcNow,
                DeviceId = _appHost.SystemId,
                DeviceName = _appHost.FriendlyName,
                AppVersion = _appHost.ApplicationVersionString,
                UserId = auth.UserId
            });

            _logger.LogInformation("Allowing device {0} to login as user {1} with quick connect code {2}", result.FriendlyName, auth.User.Name, result.Code);

            return true;
        }

        /// <inheritdoc/>
        public int DeleteAllDevices(Guid user)
        {
            var raw = _authenticationRepository.Get(new AuthenticationInfoQuery()
            {
                DeviceId = _appHost.SystemId,
                UserId = user
            });

            var tokens = raw.Items.Where(x => x.AppName.StartsWith(TokenNamePrefix, StringComparison.CurrentCulture));

            foreach (var token in tokens)
            {
                _authenticationRepository.Delete(token);
                _logger.LogDebug("Deleted token {0}", token.AccessToken);
            }

            return tokens.Count();
        }

        /// <summary>
        /// Dispose.
        /// </summary>
        public void Dispose()
        {
            Dispose(true);
            GC.SuppressFinalize(this);
        }

        /// <summary>
        /// Dispose.
        /// </summary>
        /// <param name="disposing">Dispose unmanaged resources.</param>
        protected virtual void Dispose(bool disposing)
        {
            if (disposing)
            {
                _rng?.Dispose();
            }
        }

        private string GenerateSecureRandom(int length = 32)
        {
            var bytes = new byte[length];
            _rng.GetBytes(bytes);

            return Hex.Encode(bytes);
        }

        /// <summary>
        /// Expire quick connect requests that are over the time limit. If <paramref name="expireAll"/> is true, all requests are unconditionally expired.
        /// </summary>
        /// <param name="expireAll">If true, all requests will be expired.</param>
        private void ExpireRequests(bool expireAll = false)
        {
            // Check if quick connect should be deactivated
            if (State == QuickConnectState.Active && DateTime.Now > DateActivated.AddMinutes(Timeout) && !expireAll)
            {
                _logger.LogDebug("Quick connect time expired, deactivating");
                SetEnabled(QuickConnectState.Available);
                expireAll = true;
            }

            // Expire stale connection requests
            var delete = new List<string>();
            var values = _currentRequests.Values.ToList();

            for (int i = 0; i < values.Count; i++)
            {
                var added = values[i].DateAdded ?? DateTime.UnixEpoch;
                if (DateTime.Now > added.AddMinutes(Timeout) || expireAll)
                {
                    delete.Add(values[i].Code);
                }
            }

            foreach (var code in delete)
            {
                _logger.LogDebug("Removing expired request {code}", code);

                if (!_currentRequests.TryRemove(code, out _))
                {
                    _logger.LogWarning("Request {code} already expired", code);
                }
            }
        }

        private void ReloadConfiguration()
        {
            var available = _config.Configuration.QuickConnectAvailable;

            State = available ? QuickConnectState.Available : QuickConnectState.Unavailable;
        }
    }
}