git.r.bdr.sh - rbdr/mobius/blob - hotline/server.go

   1 package hotline
   2
   3 import (
   4         "bufio"
   5         "bytes"
   6         "context"
   7         "crypto/rand"
   8         "encoding/binary"
   9         "errors"
  10         "fmt"
  11         "golang.org/x/text/encoding/charmap"
  12         "golang.org/x/time/rate"
  13         "io"
  14         "log"
  15         "log/slog"
  16         "net"
  17         "os"
  18         "strings"
  19         "sync"
  20         "time"
  21 )
  22
  23 type contextKey string
  24
  25 var contextKeyReq = contextKey("req")
  26
  27 type requestCtx struct {
  28         remoteAddr string
  29 }
  30
  31 // Converts bytes from Mac Roman encoding to UTF-8
  32 var txtDecoder = charmap.Macintosh.NewDecoder()
  33
  34 // Converts bytes from UTF-8 to Mac Roman encoding
  35 var txtEncoder = charmap.Macintosh.NewEncoder()
  36
  37 type Server struct {
  38         NetInterface string
  39         Port         int
  40
  41         rateLimiters map[string]*rate.Limiter
  42
  43         handlers map[TranType]HandlerFunc
  44
  45         Config Config
  46         Logger *slog.Logger
  47
  48         TrackerPassID [4]byte
  49
  50         Stats Counter
  51
  52         FS FileStore // Storage backend to use for File storage
  53
  54         outbox chan Transaction
  55
  56         Agreement io.ReadSeeker
  57         Banner    []byte
  58
  59         FileTransferMgr FileTransferMgr
  60         ChatMgr         ChatManager
  61         ClientMgr       ClientManager
  62         AccountManager  AccountManager
  63         ThreadedNewsMgr ThreadedNewsMgr
  64         BanList         BanMgr
  65
  66         MessageBoard io.ReadWriteSeeker
  67 }
  68
  69 type Option = func(s *Server)
  70
  71 func WithConfig(config Config) func(s *Server) {
  72         return func(s *Server) {
  73                 s.Config = config
  74         }
  75 }
  76
  77 func WithLogger(logger *slog.Logger) func(s *Server) {
  78         return func(s *Server) {
  79                 s.Logger = logger
  80         }
  81 }
  82
  83 // WithPort optionally overrides the default TCP port.
  84 func WithPort(port int) func(s *Server) {
  85         return func(s *Server) {
  86                 s.Port = port
  87         }
  88 }
  89
  90 // WithInterface optionally sets a specific interface to listen on.
  91 func WithInterface(netInterface string) func(s *Server) {
  92         return func(s *Server) {
  93                 s.NetInterface = netInterface
  94         }
  95 }
  96
  97 type ServerConfig struct {
  98 }
  99
 100 func NewServer(options ...Option) (*Server, error) {
 101         server := Server{
 102                 handlers:        make(map[TranType]HandlerFunc),
 103                 outbox:          make(chan Transaction),
 104                 rateLimiters:    make(map[string]*rate.Limiter),
 105                 FS:              &OSFileStore{},
 106                 ChatMgr:         NewMemChatManager(),
 107                 ClientMgr:       NewMemClientMgr(),
 108                 FileTransferMgr: NewMemFileTransferMgr(),
 109                 Stats:           NewStats(),
 110         }
 111
 112         for _, opt := range options {
 113                 opt(&server)
 114         }
 115
 116         // generate a new random passID for tracker registration
 117         _, err := rand.Read(server.TrackerPassID[:])
 118         if err != nil {
 119                 return nil, err
 120         }
 121
 122         return &server, nil
 123 }
 124
 125 func (s *Server) CurrentStats() map[string]interface{} {
 126         return s.Stats.Values()
 127 }
 128
 129 func (s *Server) ListenAndServe(ctx context.Context) error {
 130         go s.registerWithTrackers(ctx)
 131         go s.keepaliveHandler(ctx)
 132         go s.processOutbox()
 133
 134         var wg sync.WaitGroup
 135
 136         wg.Add(1)
 137         go func() {
 138                 ln, err := net.Listen("tcp", fmt.Sprintf("%s:%v", s.NetInterface, s.Port))
 139                 if err != nil {
 140                         log.Fatal(err)
 141                 }
 142
 143                 log.Fatal(s.Serve(ctx, ln))
 144         }()
 145
 146         wg.Add(1)
 147         go func() {
 148                 ln, err := net.Listen("tcp", fmt.Sprintf("%s:%v", s.NetInterface, s.Port+1))
 149                 if err != nil {
 150                         log.Fatal(err)
 151                 }
 152
 153                 log.Fatal(s.ServeFileTransfers(ctx, ln))
 154         }()
 155
 156         wg.Wait()
 157
 158         return nil
 159 }
 160
 161 func (s *Server) ServeFileTransfers(ctx context.Context, ln net.Listener) error {
 162         for {
 163                 conn, err := ln.Accept()
 164                 if err != nil {
 165                         return err
 166                 }
 167
 168                 go func() {
 169                         defer func() { _ = conn.Close() }()
 170
 171                         err = s.handleFileTransfer(
 172                                 context.WithValue(ctx, contextKeyReq, requestCtx{remoteAddr: conn.RemoteAddr().String()}),
 173                                 conn,
 174                         )
 175
 176                         if err != nil {
 177                                 s.Logger.Error("file transfer error", "err", err)
 178                         }
 179                 }()
 180         }
 181 }
 182
 183 func (s *Server) sendTransaction(t Transaction) error {
 184         client := s.ClientMgr.Get(t.ClientID)
 185
 186         if client == nil {
 187                 return nil
 188         }
 189
 190         _, err := io.Copy(client.Connection, &t)
 191         if err != nil {
 192                 return fmt.Errorf("failed to send transaction to client %v: %v", t.ClientID, err)
 193         }
 194
 195         return nil
 196 }
 197
 198 func (s *Server) processOutbox() {
 199         for {
 200                 t := <-s.outbox
 201                 go func() {
 202                         if err := s.sendTransaction(t); err != nil {
 203                                 s.Logger.Error("error sending transaction", "err", err)
 204                         }
 205                 }()
 206         }
 207 }
 208
 209 // perIPRateLimit controls how frequently an IP address can connect before being throttled.
 210 // 0.5 = 1 connection every 2 seconds
 211 const perIPRateLimit = rate.Limit(0.5)
 212
 213 func (s *Server) Serve(ctx context.Context, ln net.Listener) error {
 214         for {
 215                 select {
 216                 case <-ctx.Done():
 217                         s.Logger.Info("Server shutting down")
 218                         return ctx.Err()
 219                 default:
 220                         conn, err := ln.Accept()
 221                         if err != nil {
 222                                 s.Logger.Error("Error accepting connection", "err", err)
 223                                 continue
 224                         }
 225
 226                         go func() {
 227                                 ipAddr := strings.Split(conn.RemoteAddr().(*net.TCPAddr).String(), ":")[0]
 228
 229                                 connCtx := context.WithValue(ctx, contextKeyReq, requestCtx{
 230                                         remoteAddr: conn.RemoteAddr().String(),
 231                                 })
 232
 233                                 s.Logger.Info("Connection established", "ip", ipAddr)
 234                                 defer conn.Close()
 235
 236                                 // Check if we have an existing rate limit for the IP and create one if we do not.
 237                                 rl, ok := s.rateLimiters[ipAddr]
 238                                 if !ok {
 239                                         rl = rate.NewLimiter(perIPRateLimit, 1)
 240                                         s.rateLimiters[ipAddr] = rl
 241                                 }
 242
 243                                 // Check if the rate limit is exceeded and close the connection if so.
 244                                 if !rl.Allow() {
 245                                         s.Logger.Info("Rate limit exceeded", "RemoteAddr", conn.RemoteAddr())
 246                                         conn.Close()
 247                                         return
 248                                 }
 249
 250                                 if err := s.handleNewConnection(connCtx, conn, conn.RemoteAddr().String()); err != nil {
 251                                         if err == io.EOF {
 252                                                 s.Logger.Info("Client disconnected", "RemoteAddr", conn.RemoteAddr())
 253                                         } else {
 254                                                 s.Logger.Error("Error serving request", "RemoteAddr", conn.RemoteAddr(), "err", err)
 255                                         }
 256                                 }
 257                         }()
 258                 }
 259         }
 260 }
 261
 262 // time in seconds between tracker re-registration
 263 const trackerUpdateFrequency = 300
 264
 265 // registerWithTrackers runs every trackerUpdateFrequency seconds to update the server's tracker entry on all configured
 266 // trackers.
 267 func (s *Server) registerWithTrackers(ctx context.Context) {
 268         if s.Config.EnableTrackerRegistration {
 269                 s.Logger.Info("Tracker registration enabled", "trackers", s.Config.Trackers)
 270         }
 271
 272         for {
 273                 if s.Config.EnableTrackerRegistration {
 274                         for _, t := range s.Config.Trackers {
 275                                 tr := &TrackerRegistration{
 276                                         UserCount:   len(s.ClientMgr.List()),
 277                                         PassID:      s.TrackerPassID,
 278                                         Name:        s.Config.Name,
 279                                         Description: s.Config.Description,
 280                                 }
 281                                 binary.BigEndian.PutUint16(tr.Port[:], uint16(s.Port))
 282
 283                                 // Check the tracker string for a password.  This is janky but avoids a breaking change to the Config
 284                                 // Trackers field.
 285                                 splitAddr := strings.Split(":", t)
 286                                 if len(splitAddr) == 3 {
 287                                         tr.Password = splitAddr[2]
 288                                 }
 289
 290                                 if err := register(&RealDialer{}, t, tr); err != nil {
 291                                         s.Logger.Error(fmt.Sprintf("Unable to register with tracker %v", t), "error", err)
 292                                 }
 293                         }
 294                 }
 295                 // Using time.Ticker with for/select would be more idiomatic, but it's super annoying that it doesn't tick on
 296                 // first pass.  Revist, maybe.
 297                 // https://github.com/golang/go/issues/17601
 298                 time.Sleep(trackerUpdateFrequency * time.Second)
 299         }
 300 }
 301
 302 const (
 303         userIdleSeconds   = 300 // time in seconds before an inactive user is marked idle
 304         idleCheckInterval = 10  // time in seconds to check for idle users
 305 )
 306
 307 // keepaliveHandler runs every idleCheckInterval seconds and increments a user's idle time by idleCheckInterval seconds.
 308 // If the updated idle time exceeds userIdleSeconds and the user was not previously idle, we notify all connected clients
 309 // that the user has gone idle.  For most clients, this turns the user grey in the user list.
 310 func (s *Server) keepaliveHandler(ctx context.Context) {
 311         ticker := time.NewTicker(idleCheckInterval * time.Second)
 312         defer ticker.Stop()
 313
 314         for {
 315                 select {
 316                 case <-ctx.Done():
 317                         return
 318                 case <-ticker.C:
 319                         for _, c := range s.ClientMgr.List() {
 320                                 c.mu.Lock()
 321                                 c.IdleTime += idleCheckInterval
 322
 323                                 // Check if the user
 324                                 if c.IdleTime > userIdleSeconds && !c.Flags.IsSet(UserFlagAway) {
 325                                         c.Flags.Set(UserFlagAway, 1)
 326
 327                                         c.SendAll(
 328                                                 TranNotifyChangeUser,
 329                                                 NewField(FieldUserID, c.ID[:]),
 330                                                 NewField(FieldUserFlags, c.Flags[:]),
 331                                                 NewField(FieldUserName, c.UserName),
 332                                                 NewField(FieldUserIconID, c.Icon),
 333                                         )
 334                                 }
 335                                 c.mu.Unlock()
 336                         }
 337                 }
 338         }
 339 }
 340
 341 func (s *Server) NewClientConn(conn io.ReadWriteCloser, remoteAddr string) *ClientConn {
 342         clientConn := &ClientConn{
 343                 Icon:       []byte{0, 0}, // TODO: make array type
 344                 Connection: conn,
 345                 Server:     s,
 346                 RemoteAddr: remoteAddr,
 347
 348                 ClientFileTransferMgr: NewClientFileTransferMgr(),
 349         }
 350
 351         s.ClientMgr.Add(clientConn)
 352
 353         return clientConn
 354 }
 355
 356 func sendBanMessage(rwc io.Writer, message string) {
 357         t := NewTransaction(
 358                 TranServerMsg,
 359                 [2]byte{0, 0},
 360                 NewField(FieldData, []byte(message)),
 361                 NewField(FieldChatOptions, []byte{0, 0}),
 362         )
 363         _, _ = io.Copy(rwc, &t)
 364         time.Sleep(1 * time.Second)
 365 }
 366
 367 // handleNewConnection takes a new net.Conn and performs the initial login sequence
 368 func (s *Server) handleNewConnection(ctx context.Context, rwc io.ReadWriteCloser, remoteAddr string) error {
 369         defer dontPanic(s.Logger)
 370
 371         if err := performHandshake(rwc); err != nil {
 372                 return fmt.Errorf("perform handshake: %w", err)
 373         }
 374
 375         // Check if remoteAddr is present in the ban list
 376         ipAddr := strings.Split(remoteAddr, ":")[0]
 377         if isBanned, banUntil := s.BanList.IsBanned(ipAddr); isBanned {
 378                 // permaban
 379                 if banUntil == nil {
 380                         sendBanMessage(rwc, "You are permanently banned on this server")
 381                         s.Logger.Debug("Disconnecting permanently banned IP", "remoteAddr", ipAddr)
 382                         return nil
 383                 }
 384
 385                 // temporary ban
 386                 if time.Now().Before(*banUntil) {
 387                         sendBanMessage(rwc, "You are temporarily banned on this server")
 388                         s.Logger.Debug("Disconnecting temporarily banned IP", "remoteAddr", ipAddr)
 389                         return nil
 390                 }
 391         }
 392
 393         // Create a new scanner for parsing incoming bytes into transaction tokens
 394         scanner := bufio.NewScanner(rwc)
 395         scanner.Split(transactionScanner)
 396
 397         scanner.Scan()
 398
 399         // Make a new []byte slice and copy the scanner bytes to it.  This is critical to avoid a data race as the
 400         // scanner re-uses the buffer for subsequent scans.
 401         buf := make([]byte, len(scanner.Bytes()))
 402         copy(buf, scanner.Bytes())
 403
 404         var clientLogin Transaction
 405         if _, err := clientLogin.Write(buf); err != nil {
 406                 return fmt.Errorf("error writing login transaction: %w", err)
 407         }
 408
 409         c := s.NewClientConn(rwc, remoteAddr)
 410         defer c.Disconnect()
 411
 412         encodedPassword := clientLogin.GetField(FieldUserPassword).Data
 413         c.Version = clientLogin.GetField(FieldVersion).Data
 414
 415         login := clientLogin.GetField(FieldUserLogin).DecodeObfuscatedString()
 416         if login == "" {
 417                 login = GuestAccount
 418         }
 419
 420         c.Logger = s.Logger.With("ip", ipAddr, "login", login)
 421
 422         // If authentication fails, send error reply and close connection
 423         if !c.Authenticate(login, encodedPassword) {
 424                 t := c.NewErrReply(&clientLogin, "Incorrect login.")[0]
 425
 426                 _, err := io.Copy(rwc, &t)
 427                 if err != nil {
 428                         return err
 429                 }
 430
 431                 c.Logger.Info("Incorrect login")
 432
 433                 return nil
 434         }
 435
 436         if clientLogin.GetField(FieldUserIconID).Data != nil {
 437                 c.Icon = clientLogin.GetField(FieldUserIconID).Data
 438         }
 439
 440         c.Account = c.Server.AccountManager.Get(login)
 441         if c.Account == nil {
 442                 return nil
 443         }
 444
 445         if clientLogin.GetField(FieldUserName).Data != nil {
 446                 if c.Authorize(AccessAnyName) {
 447                         c.UserName = clientLogin.GetField(FieldUserName).Data
 448                 } else {
 449                         c.UserName = []byte(c.Account.Name)
 450                 }
 451         }
 452
 453         if c.Authorize(AccessDisconUser) {
 454                 c.Flags.Set(UserFlagAdmin, 1)
 455         }
 456
 457         s.outbox <- c.NewReply(&clientLogin,
 458                 NewField(FieldVersion, []byte{0x00, 0xbe}),
 459                 NewField(FieldCommunityBannerID, []byte{0, 0}),
 460                 NewField(FieldServerName, []byte(s.Config.Name)),
 461         )
 462
 463         // Send user access privs so client UI knows how to behave
 464         c.Server.outbox <- NewTransaction(TranUserAccess, c.ID, NewField(FieldUserAccess, c.Account.Access[:]))
 465
 466         // Accounts with AccessNoAgreement do not receive the server agreement on login.  The behavior is different between
 467         // client versions.  For 1.2.3 client, we do not send TranShowAgreement.  For other client versions, we send
 468         // TranShowAgreement but with the NoServerAgreement field set to 1.
 469         if c.Authorize(AccessNoAgreement) {
 470                 // If client version is nil, then the client uses the 1.2.3 login behavior
 471                 if c.Version != nil {
 472                         c.Server.outbox <- NewTransaction(TranShowAgreement, c.ID, NewField(FieldNoServerAgreement, []byte{1}))
 473                 }
 474         } else {
 475                 _, _ = c.Server.Agreement.Seek(0, 0)
 476                 data, _ := io.ReadAll(c.Server.Agreement)
 477
 478                 c.Server.outbox <- NewTransaction(TranShowAgreement, c.ID, NewField(FieldData, data))
 479         }
 480
 481         // If the client has provided a username as part of the login, we can infer that it is using the 1.2.3 login
 482         // flow and not the 1.5+ flow.
 483         if len(c.UserName) != 0 {
 484                 // Add the client username to the logger.  For 1.5+ clients, we don't have this information yet as it comes as
 485                 // part of TranAgreed
 486                 c.Logger = c.Logger.With("name", string(c.UserName))
 487                 c.Logger.Info("Login successful")
 488
 489                 // Notify other clients on the server that the new user has logged in.  For 1.5+ clients we don't have this
 490                 // information yet, so we do it in TranAgreed instead
 491                 for _, t := range c.NotifyOthers(
 492                         NewTransaction(
 493                                 TranNotifyChangeUser, [2]byte{0, 0},
 494                                 NewField(FieldUserName, c.UserName),
 495                                 NewField(FieldUserID, c.ID[:]),
 496                                 NewField(FieldUserIconID, c.Icon),
 497                                 NewField(FieldUserFlags, c.Flags[:]),
 498                         ),
 499                 ) {
 500                         c.Server.outbox <- t
 501                 }
 502         }
 503
 504         c.Server.Stats.Increment(StatConnectionCounter, StatCurrentlyConnected)
 505         defer c.Server.Stats.Decrement(StatCurrentlyConnected)
 506
 507         if len(s.ClientMgr.List()) > c.Server.Stats.Get(StatConnectionPeak) {
 508                 c.Server.Stats.Set(StatConnectionPeak, len(s.ClientMgr.List()))
 509         }
 510
 511         // Scan for new transactions and handle them as they come in.
 512         for scanner.Scan() {
 513                 // Copy the scanner bytes to a new slice to it to avoid a data race when the scanner re-uses the buffer.
 514                 tmpBuf := make([]byte, len(scanner.Bytes()))
 515                 copy(tmpBuf, scanner.Bytes())
 516
 517                 var t Transaction
 518                 if _, err := t.Write(tmpBuf); err != nil {
 519                         return err
 520                 }
 521
 522                 c.handleTransaction(t)
 523         }
 524         return nil
 525 }
 526
 527 // handleFileTransfer receives a client net.Conn from the file transfer server, performs the requested transfer type, then closes the connection
 528 func (s *Server) handleFileTransfer(ctx context.Context, rwc io.ReadWriter) error {
 529         defer dontPanic(s.Logger)
 530
 531         // The first 16 bytes contain the file transfer.
 532         var t transfer
 533         if _, err := io.CopyN(&t, rwc, 16); err != nil {
 534                 return fmt.Errorf("error reading file transfer: %w", err)
 535         }
 536
 537         fileTransfer := s.FileTransferMgr.Get(t.ReferenceNumber)
 538         if fileTransfer == nil {
 539                 return errors.New("invalid transaction ID")
 540         }
 541
 542         defer func() {
 543                 s.FileTransferMgr.Delete(t.ReferenceNumber)
 544
 545                 // Wait a few seconds before closing the connection: this is a workaround for problems
 546                 // observed with Windows clients where the client must initiate close of the TCP connection before
 547                 // the server does.  This is gross and seems unnecessary.  TODO: Revisit?
 548                 time.Sleep(3 * time.Second)
 549         }()
 550
 551         rLogger := s.Logger.With(
 552                 "remoteAddr", ctx.Value(contextKeyReq).(requestCtx).remoteAddr,
 553                 "login", fileTransfer.ClientConn.Account.Login,
 554                 "Name", string(fileTransfer.ClientConn.UserName),
 555         )
 556
 557         fullPath, err := ReadPath(fileTransfer.FileRoot, fileTransfer.FilePath, fileTransfer.FileName)
 558         if err != nil {
 559                 return err
 560         }
 561
 562         switch fileTransfer.Type {
 563         case BannerDownload:
 564                 if _, err := io.Copy(rwc, bytes.NewBuffer(s.Banner)); err != nil {
 565                         return fmt.Errorf("banner download: %w", err)
 566                 }
 567         case FileDownload:
 568                 s.Stats.Increment(StatDownloadCounter, StatDownloadsInProgress)
 569                 defer func() {
 570                         s.Stats.Decrement(StatDownloadsInProgress)
 571                 }()
 572
 573                 err = DownloadHandler(rwc, fullPath, fileTransfer, s.FS, rLogger, true)
 574                 if err != nil {
 575                         return fmt.Errorf("file download: %w", err)
 576                 }
 577
 578         case FileUpload:
 579                 s.Stats.Increment(StatUploadCounter, StatUploadsInProgress)
 580                 defer func() {
 581                         s.Stats.Decrement(StatUploadsInProgress)
 582                 }()
 583
 584                 err = UploadHandler(rwc, fullPath, fileTransfer, s.FS, rLogger, s.Config.PreserveResourceForks)
 585                 if err != nil {
 586                         return fmt.Errorf("file upload: %w", err)
 587                 }
 588
 589         case FolderDownload:
 590                 s.Stats.Increment(StatDownloadCounter, StatDownloadsInProgress)
 591                 defer func() {
 592                         s.Stats.Decrement(StatDownloadsInProgress)
 593                 }()
 594
 595                 err = DownloadFolderHandler(rwc, fullPath, fileTransfer, s.FS, rLogger, s.Config.PreserveResourceForks)
 596                 if err != nil {
 597                         return fmt.Errorf("folder download: %w", err)
 598                 }
 599
 600         case FolderUpload:
 601                 s.Stats.Increment(StatUploadCounter, StatUploadsInProgress)
 602                 defer func() {
 603                         s.Stats.Decrement(StatUploadsInProgress)
 604                 }()
 605
 606                 var transferSizeValue uint32
 607                 switch len(fileTransfer.TransferSize) {
 608                         case 2: // 16-bit
 609                                 transferSizeValue = uint32(binary.BigEndian.Uint16(fileTransfer.TransferSize))
 610                         case 4: // 32-bit
 611                                 transferSizeValue = binary.BigEndian.Uint32(fileTransfer.TransferSize)
 612                         default:
 613                                 rLogger.Warn("Unexpected TransferSize length: %d bytes", len(fileTransfer.TransferSize))
 614                 }
 615
 616                 rLogger.Info(
 617                         "Folder upload started",
 618                         "dstPath", fullPath,
 619                         "TransferSize", transferSizeValue,
 620                         "FolderItemCount", fileTransfer.FolderItemCount,
 621                 )
 622
 623                 err = UploadFolderHandler(rwc, fullPath, fileTransfer, s.FS, rLogger, s.Config.PreserveResourceForks)
 624                 if err != nil {
 625                         return fmt.Errorf("folder upload: %w", err)
 626                 }
 627         }
 628         return nil
 629 }
 630
 631 func (s *Server) SendAll(t TranType, fields ...Field) {
 632         for _, c := range s.ClientMgr.List() {
 633                 s.outbox <- NewTransaction(t, c.ID, fields...)
 634         }
 635 }
 636
 637 func (s *Server) Shutdown(msg []byte) {
 638         s.Logger.Info("Shutdown signal received")
 639         s.SendAll(TranDisconnectMsg, NewField(FieldData, msg))
 640
 641         time.Sleep(3 * time.Second)
 642
 643         os.Exit(0)
 644 }