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

   1 package hotline
   2
   3 import (
   4         "context"
   5         "encoding/binary"
   6         "errors"
   7         "fmt"
   8         "go.uber.org/zap"
   9         "io"
  10         "io/fs"
  11         "io/ioutil"
  12         "math/big"
  13         "math/rand"
  14         "net"
  15         "os"
  16         "path"
  17         "path/filepath"
  18         "runtime/debug"
  19         "sort"
  20         "strings"
  21         "sync"
  22         "time"
  23
  24         "gopkg.in/yaml.v3"
  25 )
  26
  27 const (
  28         userIdleSeconds        = 300 // time in seconds before an inactive user is marked idle
  29         idleCheckInterval      = 10  // time in seconds to check for idle users
  30         trackerUpdateFrequency = 300 // time in seconds between tracker re-registration
  31 )
  32
  33 type Server struct {
  34         Port          int
  35         Accounts      map[string]*Account
  36         Agreement     []byte
  37         Clients       map[uint16]*ClientConn
  38         FlatNews      []byte
  39         ThreadedNews  *ThreadedNews
  40         FileTransfers map[uint32]*FileTransfer
  41         Config        *Config
  42         ConfigDir     string
  43         Logger        *zap.SugaredLogger
  44         PrivateChats  map[uint32]*PrivateChat
  45         NextGuestID   *uint16
  46         TrackerPassID []byte
  47         Stats         *Stats
  48
  49         APIListener  net.Listener
  50         FileListener net.Listener
  51
  52         // newsReader io.Reader
  53         // newsWriter io.WriteCloser
  54
  55         outbox chan Transaction
  56
  57         mux         sync.Mutex
  58         flatNewsMux sync.Mutex
  59 }
  60
  61 type PrivateChat struct {
  62         Subject    string
  63         ClientConn map[uint16]*ClientConn
  64 }
  65
  66 func (s *Server) ListenAndServe(ctx context.Context, cancelRoot context.CancelFunc) error {
  67         s.Logger.Infow("Hotline server started", "version", VERSION)
  68         var wg sync.WaitGroup
  69
  70         wg.Add(1)
  71         go func() { s.Logger.Fatal(s.Serve(ctx, cancelRoot, s.APIListener)) }()
  72
  73         wg.Add(1)
  74         go func() { s.Logger.Fatal(s.ServeFileTransfers(s.FileListener)) }()
  75
  76         wg.Wait()
  77
  78         return nil
  79 }
  80
  81 func (s *Server) APIPort() int {
  82         return s.APIListener.Addr().(*net.TCPAddr).Port
  83 }
  84
  85 func (s *Server) ServeFileTransfers(ln net.Listener) error {
  86         s.Logger.Infow("Hotline file transfer server started", "Addr", fmt.Sprintf(":%v", s.Port+1))
  87
  88         for {
  89                 conn, err := ln.Accept()
  90                 if err != nil {
  91                         return err
  92                 }
  93
  94                 go func() {
  95                         if err := s.handleFileTransfer(conn); err != nil {
  96                                 s.Logger.Errorw("file transfer error", "reason", err)
  97                         }
  98                 }()
  99         }
 100 }
 101
 102 func (s *Server) sendTransaction(t Transaction) error {
 103         requestNum := binary.BigEndian.Uint16(t.Type)
 104         clientID, err := byteToInt(*t.clientID)
 105         if err != nil {
 106                 return err
 107         }
 108
 109         s.mux.Lock()
 110         client := s.Clients[uint16(clientID)]
 111         s.mux.Unlock()
 112         if client == nil {
 113                 return fmt.Errorf("invalid client id %v", *t.clientID)
 114         }
 115         userName := string(client.UserName)
 116         login := client.Account.Login
 117
 118         handler := TransactionHandlers[requestNum]
 119
 120         b, err := t.MarshalBinary()
 121         if err != nil {
 122                 return err
 123         }
 124         var n int
 125         if n, err = client.Connection.Write(b); err != nil {
 126                 return err
 127         }
 128         s.Logger.Debugw("Sent Transaction",
 129                 "name", userName,
 130                 "login", login,
 131                 "IsReply", t.IsReply,
 132                 "type", handler.Name,
 133                 "sentBytes", n,
 134                 "remoteAddr", client.RemoteAddr,
 135         )
 136         return nil
 137 }
 138
 139 func (s *Server) Serve(ctx context.Context, cancelRoot context.CancelFunc, ln net.Listener) error {
 140         s.Logger.Infow("Hotline server started", "Addr", fmt.Sprintf(":%v", s.Port))
 141
 142         for {
 143                 conn, err := ln.Accept()
 144                 if err != nil {
 145                         s.Logger.Errorw("error accepting connection", "err", err)
 146                 }
 147
 148                 go func() {
 149                         for {
 150                                 t := <-s.outbox
 151                                 go func() {
 152                                         if err := s.sendTransaction(t); err != nil {
 153                                                 s.Logger.Errorw("error sending transaction", "err", err)
 154                                         }
 155                                 }()
 156                         }
 157                 }()
 158                 go func() {
 159                         if err := s.handleNewConnection(conn, conn.RemoteAddr().String()); err != nil {
 160                                 if err == io.EOF {
 161                                         s.Logger.Infow("Client disconnected", "RemoteAddr", conn.RemoteAddr())
 162                                 } else {
 163                                         s.Logger.Errorw("error serving request", "RemoteAddr", conn.RemoteAddr(), "err", err)
 164                                 }
 165                         }
 166                 }()
 167         }
 168 }
 169
 170 const (
 171         agreementFile = "Agreement.txt"
 172 )
 173
 174 // NewServer constructs a new Server from a config dir
 175 func NewServer(configDir, netInterface string, netPort int, logger *zap.SugaredLogger) (*Server, error) {
 176         server := Server{
 177                 Port:          netPort,
 178                 Accounts:      make(map[string]*Account),
 179                 Config:        new(Config),
 180                 Clients:       make(map[uint16]*ClientConn),
 181                 FileTransfers: make(map[uint32]*FileTransfer),
 182                 PrivateChats:  make(map[uint32]*PrivateChat),
 183                 ConfigDir:     configDir,
 184                 Logger:        logger,
 185                 NextGuestID:   new(uint16),
 186                 outbox:        make(chan Transaction),
 187                 Stats:         &Stats{StartTime: time.Now()},
 188                 ThreadedNews:  &ThreadedNews{},
 189                 TrackerPassID: make([]byte, 4),
 190         }
 191
 192         ln, err := net.Listen("tcp", fmt.Sprintf("%s:%v", netInterface, netPort))
 193         if err != nil {
 194                 return nil, err
 195         }
 196         server.APIListener = ln
 197
 198         if netPort != 0 {
 199                 netPort += 1
 200         }
 201
 202         ln2, err := net.Listen("tcp", fmt.Sprintf("%s:%v", netInterface, netPort))
 203         server.FileListener = ln2
 204         if err != nil {
 205                 return nil, err
 206         }
 207
 208         // generate a new random passID for tracker registration
 209         if _, err := rand.Read(server.TrackerPassID); err != nil {
 210                 return nil, err
 211         }
 212
 213         server.Logger.Debugw("Loading Agreement", "path", configDir+agreementFile)
 214         if server.Agreement, err = os.ReadFile(configDir + agreementFile); err != nil {
 215                 return nil, err
 216         }
 217
 218         if server.FlatNews, err = os.ReadFile(configDir + "MessageBoard.txt"); err != nil {
 219                 return nil, err
 220         }
 221
 222         if err := server.loadThreadedNews(configDir + "ThreadedNews.yaml"); err != nil {
 223                 return nil, err
 224         }
 225
 226         if err := server.loadConfig(configDir + "config.yaml"); err != nil {
 227                 return nil, err
 228         }
 229
 230         if err := server.loadAccounts(configDir + "Users/"); err != nil {
 231                 return nil, err
 232         }
 233
 234         server.Config.FileRoot = configDir + "Files/"
 235
 236         *server.NextGuestID = 1
 237
 238         if server.Config.EnableTrackerRegistration {
 239                 server.Logger.Infow(
 240                         "Tracker registration enabled",
 241                         "frequency", fmt.Sprintf("%vs", trackerUpdateFrequency),
 242                         "trackers", server.Config.Trackers,
 243                 )
 244
 245                 go func() {
 246                         for {
 247                                 tr := &TrackerRegistration{
 248                                         Port:        []byte{0x15, 0x7c},
 249                                         UserCount:   server.userCount(),
 250                                         PassID:      server.TrackerPassID,
 251                                         Name:        server.Config.Name,
 252                                         Description: server.Config.Description,
 253                                 }
 254                                 for _, t := range server.Config.Trackers {
 255                                         if err := register(t, tr); err != nil {
 256                                                 server.Logger.Errorw("unable to register with tracker %v", "error", err)
 257                                         }
 258                                         server.Logger.Infow("Sent Tracker registration", "data", tr)
 259                                 }
 260
 261                                 time.Sleep(trackerUpdateFrequency * time.Second)
 262                         }
 263                 }()
 264         }
 265
 266         // Start Client Keepalive go routine
 267         go server.keepaliveHandler()
 268
 269         return &server, nil
 270 }
 271
 272 func (s *Server) userCount() int {
 273         s.mux.Lock()
 274         defer s.mux.Unlock()
 275
 276         return len(s.Clients)
 277 }
 278
 279 func (s *Server) keepaliveHandler() {
 280         for {
 281                 time.Sleep(idleCheckInterval * time.Second)
 282                 s.mux.Lock()
 283
 284                 for _, c := range s.Clients {
 285                         c.IdleTime += idleCheckInterval
 286                         if c.IdleTime > userIdleSeconds && !c.Idle {
 287                                 c.Idle = true
 288
 289                                 flagBitmap := big.NewInt(int64(binary.BigEndian.Uint16(*c.Flags)))
 290                                 flagBitmap.SetBit(flagBitmap, userFlagAway, 1)
 291                                 binary.BigEndian.PutUint16(*c.Flags, uint16(flagBitmap.Int64()))
 292
 293                                 c.sendAll(
 294                                         tranNotifyChangeUser,
 295                                         NewField(fieldUserID, *c.ID),
 296                                         NewField(fieldUserFlags, *c.Flags),
 297                                         NewField(fieldUserName, c.UserName),
 298                                         NewField(fieldUserIconID, *c.Icon),
 299                                 )
 300                         }
 301                 }
 302                 s.mux.Unlock()
 303         }
 304 }
 305
 306 func (s *Server) writeThreadedNews() error {
 307         s.mux.Lock()
 308         defer s.mux.Unlock()
 309
 310         out, err := yaml.Marshal(s.ThreadedNews)
 311         if err != nil {
 312                 return err
 313         }
 314         err = ioutil.WriteFile(
 315                 s.ConfigDir+"ThreadedNews.yaml",
 316                 out,
 317                 0666,
 318         )
 319         return err
 320 }
 321
 322 func (s *Server) NewClientConn(conn net.Conn, remoteAddr string) *ClientConn {
 323         s.mux.Lock()
 324         defer s.mux.Unlock()
 325
 326         clientConn := &ClientConn{
 327                 ID:         &[]byte{0, 0},
 328                 Icon:       &[]byte{0, 0},
 329                 Flags:      &[]byte{0, 0},
 330                 UserName:   []byte{},
 331                 Connection: conn,
 332                 Server:     s,
 333                 Version:    &[]byte{},
 334                 AutoReply:  []byte{},
 335                 Transfers:  make(map[int][]*FileTransfer),
 336                 Agreed:     false,
 337                 RemoteAddr: remoteAddr,
 338         }
 339         *s.NextGuestID++
 340         ID := *s.NextGuestID
 341
 342         binary.BigEndian.PutUint16(*clientConn.ID, ID)
 343         s.Clients[ID] = clientConn
 344
 345         return clientConn
 346 }
 347
 348 // NewUser creates a new user account entry in the server map and config file
 349 func (s *Server) NewUser(login, name, password string, access []byte) error {
 350         s.mux.Lock()
 351         defer s.mux.Unlock()
 352
 353         account := Account{
 354                 Login:    login,
 355                 Name:     name,
 356                 Password: hashAndSalt([]byte(password)),
 357                 Access:   &access,
 358         }
 359         out, err := yaml.Marshal(&account)
 360         if err != nil {
 361                 return err
 362         }
 363         s.Accounts[login] = &account
 364
 365         return FS.WriteFile(s.ConfigDir+"Users/"+login+".yaml", out, 0666)
 366 }
 367
 368 func (s *Server) UpdateUser(login, newLogin, name, password string, access []byte) error {
 369         s.mux.Lock()
 370         defer s.mux.Unlock()
 371
 372         fmt.Printf("login: %v, newLogin: %v: ", login, newLogin)
 373
 374         // update renames the user login
 375         if login != newLogin {
 376                 err := os.Rename(s.ConfigDir+"Users/"+login+".yaml", s.ConfigDir+"Users/"+newLogin+".yaml")
 377                 if err != nil {
 378                         return err
 379                 }
 380                 s.Accounts[newLogin] = s.Accounts[login]
 381                 delete(s.Accounts, login)
 382         }
 383
 384         account := s.Accounts[newLogin]
 385         account.Access = &access
 386         account.Name = name
 387         account.Password = password
 388
 389         out, err := yaml.Marshal(&account)
 390         if err != nil {
 391                 return err
 392         }
 393         if err := os.WriteFile(s.ConfigDir+"Users/"+newLogin+".yaml", out, 0666); err != nil {
 394                 return err
 395         }
 396
 397         return nil
 398 }
 399
 400 // DeleteUser deletes the user account
 401 func (s *Server) DeleteUser(login string) error {
 402         s.mux.Lock()
 403         defer s.mux.Unlock()
 404
 405         delete(s.Accounts, login)
 406
 407         return FS.Remove(s.ConfigDir + "Users/" + login + ".yaml")
 408 }
 409
 410 func (s *Server) connectedUsers() []Field {
 411         s.mux.Lock()
 412         defer s.mux.Unlock()
 413
 414         var connectedUsers []Field
 415         for _, c := range sortedClients(s.Clients) {
 416                 if !c.Agreed {
 417                         continue
 418                 }
 419                 user := User{
 420                         ID:    *c.ID,
 421                         Icon:  *c.Icon,
 422                         Flags: *c.Flags,
 423                         Name:  string(c.UserName),
 424                 }
 425                 connectedUsers = append(connectedUsers, NewField(fieldUsernameWithInfo, user.Payload()))
 426         }
 427         return connectedUsers
 428 }
 429
 430 // loadThreadedNews loads the threaded news data from disk
 431 func (s *Server) loadThreadedNews(threadedNewsPath string) error {
 432         fh, err := os.Open(threadedNewsPath)
 433         if err != nil {
 434                 return err
 435         }
 436         decoder := yaml.NewDecoder(fh)
 437
 438         return decoder.Decode(s.ThreadedNews)
 439 }
 440
 441 // loadAccounts loads account data from disk
 442 func (s *Server) loadAccounts(userDir string) error {
 443         matches, err := filepath.Glob(path.Join(userDir, "*.yaml"))
 444         if err != nil {
 445                 return err
 446         }
 447
 448         if len(matches) == 0 {
 449                 return errors.New("no user accounts found in " + userDir)
 450         }
 451
 452         for _, file := range matches {
 453                 fh, err := FS.Open(file)
 454                 if err != nil {
 455                         return err
 456                 }
 457
 458                 account := Account{}
 459                 decoder := yaml.NewDecoder(fh)
 460                 if err := decoder.Decode(&account); err != nil {
 461                         return err
 462                 }
 463
 464                 s.Accounts[account.Login] = &account
 465         }
 466         return nil
 467 }
 468
 469 func (s *Server) loadConfig(path string) error {
 470         fh, err := FS.Open(path)
 471         if err != nil {
 472                 return err
 473         }
 474
 475         decoder := yaml.NewDecoder(fh)
 476         err = decoder.Decode(s.Config)
 477         if err != nil {
 478                 return err
 479         }
 480         return nil
 481 }
 482
 483 const (
 484         minTransactionLen = 22 // minimum length of any transaction
 485 )
 486
 487 // dontPanic recovers and logs panics instead of crashing
 488 // TODO: remove this after known issues are fixed
 489 func dontPanic(logger *zap.SugaredLogger) {
 490         if r := recover(); r != nil {
 491                 fmt.Println("stacktrace from panic: \n" + string(debug.Stack()))
 492                 logger.Errorw("PANIC", "err", r, "trace", string(debug.Stack()))
 493         }
 494 }
 495
 496 // handleNewConnection takes a new net.Conn and performs the initial login sequence
 497 func (s *Server) handleNewConnection(conn net.Conn, remoteAddr string) error {
 498         defer dontPanic(s.Logger)
 499
 500         if err := Handshake(conn); err != nil {
 501                 return err
 502         }
 503
 504         buf := make([]byte, 1024)
 505         // TODO: fix potential short read with io.ReadFull
 506         readLen, err := conn.Read(buf)
 507         if readLen < minTransactionLen {
 508                 return err
 509         }
 510         if err != nil {
 511                 return err
 512         }
 513
 514         clientLogin, _, err := ReadTransaction(buf[:readLen])
 515         if err != nil {
 516                 return err
 517         }
 518
 519         c := s.NewClientConn(conn, remoteAddr)
 520         defer c.Disconnect()
 521
 522         encodedLogin := clientLogin.GetField(fieldUserLogin).Data
 523         encodedPassword := clientLogin.GetField(fieldUserPassword).Data
 524         *c.Version = clientLogin.GetField(fieldVersion).Data
 525
 526         var login string
 527         for _, char := range encodedLogin {
 528                 login += string(rune(255 - uint(char)))
 529         }
 530         if login == "" {
 531                 login = GuestAccount
 532         }
 533
 534         // If authentication fails, send error reply and close connection
 535         if !c.Authenticate(login, encodedPassword) {
 536                 t := c.NewErrReply(clientLogin, "Incorrect login.")
 537                 b, err := t.MarshalBinary()
 538                 if err != nil {
 539                         return err
 540                 }
 541                 if _, err := conn.Write(b); err != nil {
 542                         return err
 543                 }
 544                 return fmt.Errorf("incorrect login")
 545         }
 546
 547         if clientLogin.GetField(fieldUserName).Data != nil {
 548                 c.UserName = clientLogin.GetField(fieldUserName).Data
 549         }
 550
 551         if clientLogin.GetField(fieldUserIconID).Data != nil {
 552                 *c.Icon = clientLogin.GetField(fieldUserIconID).Data
 553         }
 554
 555         c.Account = c.Server.Accounts[login]
 556
 557         if c.Authorize(accessDisconUser) {
 558                 *c.Flags = []byte{0, 2}
 559         }
 560
 561         s.Logger.Infow("Client connection received", "login", login, "version", *c.Version, "RemoteAddr", remoteAddr)
 562
 563         s.outbox <- c.NewReply(clientLogin,
 564                 NewField(fieldVersion, []byte{0x00, 0xbe}),
 565                 NewField(fieldCommunityBannerID, []byte{0x00, 0x01}),
 566                 NewField(fieldServerName, []byte(s.Config.Name)),
 567         )
 568
 569         // Send user access privs so client UI knows how to behave
 570         c.Server.outbox <- *NewTransaction(tranUserAccess, c.ID, NewField(fieldUserAccess, *c.Account.Access))
 571
 572         // Show agreement to client
 573         c.Server.outbox <- *NewTransaction(tranShowAgreement, c.ID, NewField(fieldData, s.Agreement))
 574
 575         // assume simplified hotline v1.2.3 login flow that does not require agreement
 576         if *c.Version == nil {
 577                 c.Agreed = true
 578
 579                 c.notifyOthers(
 580                         *NewTransaction(
 581                                 tranNotifyChangeUser, nil,
 582                                 NewField(fieldUserName, c.UserName),
 583                                 NewField(fieldUserID, *c.ID),
 584                                 NewField(fieldUserIconID, *c.Icon),
 585                                 NewField(fieldUserFlags, *c.Flags),
 586                         ),
 587                 )
 588         }
 589
 590         c.Server.Stats.LoginCount += 1
 591
 592         const readBuffSize = 1024000 // 1KB - TODO: what should this be?
 593         tranBuff := make([]byte, 0)
 594         tReadlen := 0
 595         // Infinite loop where take action on incoming client requests until the connection is closed
 596         for {
 597                 buf = make([]byte, readBuffSize)
 598                 tranBuff = tranBuff[tReadlen:]
 599
 600                 readLen, err := c.Connection.Read(buf)
 601                 if err != nil {
 602                         return err
 603                 }
 604                 tranBuff = append(tranBuff, buf[:readLen]...)
 605
 606                 // We may have read multiple requests worth of bytes from Connection.Read.  readTransactions splits them
 607                 // into a slice of transactions
 608                 var transactions []Transaction
 609                 if transactions, tReadlen, err = readTransactions(tranBuff); err != nil {
 610                         c.Server.Logger.Errorw("Error handling transaction", "err", err)
 611                 }
 612
 613                 // iterate over all of the transactions that were parsed from the byte slice and handle them
 614                 for _, t := range transactions {
 615                         if err := c.handleTransaction(&t); err != nil {
 616                                 c.Server.Logger.Errorw("Error handling transaction", "err", err)
 617                         }
 618                 }
 619         }
 620 }
 621
 622 // NewTransactionRef generates a random ID for the file transfer.  The Hotline client includes this ID
 623 // in the file transfer request payload, and the file transfer server will use it to map the request
 624 // to a transfer
 625 func (s *Server) NewTransactionRef() []byte {
 626         transactionRef := make([]byte, 4)
 627         rand.Read(transactionRef)
 628
 629         return transactionRef
 630 }
 631
 632 func (s *Server) NewPrivateChat(cc *ClientConn) []byte {
 633         s.mux.Lock()
 634         defer s.mux.Unlock()
 635
 636         randID := make([]byte, 4)
 637         rand.Read(randID)
 638         data := binary.BigEndian.Uint32(randID[:])
 639
 640         s.PrivateChats[data] = &PrivateChat{
 641                 Subject:    "",
 642                 ClientConn: make(map[uint16]*ClientConn),
 643         }
 644         s.PrivateChats[data].ClientConn[cc.uint16ID()] = cc
 645
 646         return randID
 647 }
 648
 649 const dlFldrActionSendFile = 1
 650 const dlFldrActionResumeFile = 2
 651 const dlFldrActionNextFile = 3
 652
 653 // handleFileTransfer receives a client net.Conn from the file transfer server, performs the requested transfer type, then closes the connection
 654 func (s *Server) handleFileTransfer(conn io.ReadWriteCloser) error {
 655         defer func() {
 656
 657                 if err := conn.Close(); err != nil {
 658                         s.Logger.Errorw("error closing connection", "error", err)
 659                 }
 660         }()
 661
 662         defer dontPanic(s.Logger)
 663
 664         txBuf := make([]byte, 16)
 665         if _, err := io.ReadFull(conn, txBuf); err != nil {
 666                 return err
 667         }
 668
 669         var t transfer
 670         if _, err := t.Write(txBuf); err != nil {
 671                 return err
 672         }
 673
 674         transferRefNum := binary.BigEndian.Uint32(t.ReferenceNumber[:])
 675         defer func() {
 676                 s.mux.Lock()
 677                 delete(s.FileTransfers, transferRefNum)
 678                 s.mux.Unlock()
 679         }()
 680
 681         s.mux.Lock()
 682         fileTransfer, ok := s.FileTransfers[transferRefNum]
 683         s.mux.Unlock()
 684         if !ok {
 685                 return errors.New("invalid transaction ID")
 686         }
 687
 688         switch fileTransfer.Type {
 689         case FileDownload:
 690                 fullFilePath, err := readPath(s.Config.FileRoot, fileTransfer.FilePath, fileTransfer.FileName)
 691                 if err != nil {
 692                         return err
 693                 }
 694
 695                 var dataOffset int64
 696                 if fileTransfer.fileResumeData != nil {
 697                         dataOffset = int64(binary.BigEndian.Uint32(fileTransfer.fileResumeData.ForkInfoList[0].DataSize[:]))
 698                 }
 699
 700                 ffo, err := NewFlattenedFileObject(s.Config.FileRoot, fileTransfer.FilePath, fileTransfer.FileName, dataOffset)
 701                 if err != nil {
 702                         return err
 703                 }
 704
 705                 s.Logger.Infow("File download started", "filePath", fullFilePath, "transactionRef", fileTransfer.ReferenceNumber)
 706
 707                 if fileTransfer.options == nil {
 708                         // Start by sending flat file object to client
 709                         if _, err := conn.Write(ffo.BinaryMarshal()); err != nil {
 710                                 return err
 711                         }
 712                 }
 713
 714                 file, err := FS.Open(fullFilePath)
 715                 if err != nil {
 716                         return err
 717                 }
 718
 719                 sendBuffer := make([]byte, 1048576)
 720                 var totalSent int64
 721                 for {
 722                         var bytesRead int
 723                         if bytesRead, err = file.ReadAt(sendBuffer, dataOffset+totalSent); err == io.EOF {
 724                                 if _, err := conn.Write(sendBuffer[:bytesRead]); err != nil {
 725                                         return err
 726                                 }
 727                                 break
 728                         }
 729                         if err != nil {
 730                                 return err
 731                         }
 732                         totalSent += int64(bytesRead)
 733
 734                         fileTransfer.BytesSent += bytesRead
 735
 736                         if _, err := conn.Write(sendBuffer[:bytesRead]); err != nil {
 737                                 return err
 738                         }
 739                 }
 740         case FileUpload:
 741                 destinationFile := s.Config.FileRoot + ReadFilePath(fileTransfer.FilePath) + "/" + string(fileTransfer.FileName)
 742
 743                 var file *os.File
 744
 745                 // A file upload has three possible cases:
 746                 // 1) Upload a new file
 747                 // 2) Resume a partially transferred file
 748                 // 3) Replace a fully uploaded file
 749                 // Unfortunately we have to infer which case applies by inspecting what is already on the file system
 750
 751                 // 1) Check for existing file:
 752                 _, err := os.Stat(destinationFile)
 753                 if err == nil {
 754                         // If found, that means this upload is intended to replace the file
 755                         if err = os.Remove(destinationFile); err != nil {
 756                                 return err
 757                         }
 758                         file, err = os.Create(destinationFile + incompleteFileSuffix)
 759                 }
 760                 if errors.Is(err, fs.ErrNotExist) {
 761                         // If not found, open or create a new incomplete file
 762                         file, err = os.OpenFile(destinationFile+incompleteFileSuffix, os.O_CREATE|os.O_APPEND|os.O_WRONLY, 0644)
 763                         if err != nil {
 764                                 return err
 765                         }
 766                 }
 767
 768                 defer func() { _ = file.Close() }()
 769
 770                 s.Logger.Infow("File upload started", "transactionRef", fileTransfer.ReferenceNumber, "dstFile", destinationFile)
 771
 772                 // TODO: replace io.Discard with a real file when ready to implement storing of resource fork data
 773                 if err := receiveFile(conn, file, io.Discard); err != nil {
 774                         return err
 775                 }
 776
 777                 if err := os.Rename(destinationFile+".incomplete", destinationFile); err != nil {
 778                         return err
 779                 }
 780
 781                 s.Logger.Infow("File upload complete", "transactionRef", fileTransfer.ReferenceNumber, "dstFile", destinationFile)
 782         case FolderDownload:
 783                 // Folder Download flow:
 784                 // 1. Get filePath from the transfer
 785                 // 2. Iterate over files
 786                 // 3. For each file:
 787                 //       Send file header to client
 788                 // The client can reply in 3 ways:
 789                 //
 790                 // 1. If type is an odd number (unknown type?), or file download for the current file is completed:
 791                 //              client sends []byte{0x00, 0x03} to tell the server to continue to the next file
 792                 //
 793                 // 2. If download of a file is to be resumed:
 794                 //              client sends:
 795                 //                      []byte{0x00, 0x02} // download folder action
 796                 //                      [2]byte // Resume data size
 797                 //                      []byte file resume data (see myField_FileResumeData)
 798                 //
 799                 // 3. Otherwise, download of the file is requested and client sends []byte{0x00, 0x01}
 800                 //
 801                 // When download is requested (case 2 or 3), server replies with:
 802                 //                      [4]byte - file size
 803                 //                      []byte  - Flattened File Object
 804                 //
 805                 // After every file download, client could request next file with:
 806                 //                      []byte{0x00, 0x03}
 807                 //
 808                 // This notifies the server to send the next item header
 809
 810                 fullFilePath, err := readPath(s.Config.FileRoot, fileTransfer.FilePath, fileTransfer.FileName)
 811                 if err != nil {
 812                         return err
 813                 }
 814
 815                 basePathLen := len(fullFilePath)
 816
 817                 s.Logger.Infow("Start folder download", "path", fullFilePath, "ReferenceNumber", fileTransfer.ReferenceNumber)
 818
 819                 nextAction := make([]byte, 2)
 820                 if _, err := io.ReadFull(conn, nextAction); err != nil {
 821                         return err
 822                 }
 823
 824                 i := 0
 825                 err = filepath.Walk(fullFilePath+"/", func(path string, info os.FileInfo, err error) error {
 826                         if err != nil {
 827                                 return err
 828                         }
 829                         i += 1
 830                         subPath := path[basePathLen+1:]
 831                         s.Logger.Infow("Sending fileheader", "i", i, "path", path, "fullFilePath", fullFilePath, "subPath", subPath, "IsDir", info.IsDir())
 832
 833                         if i == 1 {
 834                                 return nil
 835                         }
 836
 837                         fileHeader := NewFileHeader(subPath, info.IsDir())
 838
 839                         // Send the file header to client
 840                         if _, err := conn.Write(fileHeader.Payload()); err != nil {
 841                                 s.Logger.Errorf("error sending file header: %v", err)
 842                                 return err
 843                         }
 844
 845                         // Read the client's Next Action request
 846                         if _, err := io.ReadFull(conn, nextAction); err != nil {
 847                                 return err
 848                         }
 849
 850                         s.Logger.Infow("Client folder download action", "action", fmt.Sprintf("%X", nextAction[0:2]))
 851
 852                         var dataOffset int64
 853
 854                         switch nextAction[1] {
 855                         case dlFldrActionResumeFile:
 856                                 // client asked to resume this file
 857                                 var frd FileResumeData
 858                                 // get size of resumeData
 859                                 if _, err := io.ReadFull(conn, nextAction); err != nil {
 860                                         return err
 861                                 }
 862
 863                                 resumeDataLen := binary.BigEndian.Uint16(nextAction)
 864                                 resumeDataBytes := make([]byte, resumeDataLen)
 865                                 if _, err := io.ReadFull(conn, resumeDataBytes); err != nil {
 866                                         return err
 867                                 }
 868
 869                                 if err := frd.UnmarshalBinary(resumeDataBytes); err != nil {
 870                                         return err
 871                                 }
 872                                 dataOffset = int64(binary.BigEndian.Uint32(frd.ForkInfoList[0].DataSize[:]))
 873                         case dlFldrActionNextFile:
 874                                 // client asked to skip this file
 875                                 return nil
 876                         }
 877
 878                         if info.IsDir() {
 879                                 return nil
 880                         }
 881
 882                         splitPath := strings.Split(path, "/")
 883
 884                         ffo, err := NewFlattenedFileObject(strings.Join(splitPath[:len(splitPath)-1], "/"), nil, []byte(info.Name()), dataOffset)
 885                         if err != nil {
 886                                 return err
 887                         }
 888                         s.Logger.Infow("File download started",
 889                                 "fileName", info.Name(),
 890                                 "transactionRef", fileTransfer.ReferenceNumber,
 891                                 "TransferSize", fmt.Sprintf("%x", ffo.TransferSize()),
 892                         )
 893
 894                         // Send file size to client
 895                         if _, err := conn.Write(ffo.TransferSize()); err != nil {
 896                                 s.Logger.Error(err)
 897                                 return err
 898                         }
 899
 900                         // Send ffo bytes to client
 901                         if _, err := conn.Write(ffo.BinaryMarshal()); err != nil {
 902                                 s.Logger.Error(err)
 903                                 return err
 904                         }
 905
 906                         file, err := FS.Open(path)
 907                         if err != nil {
 908                                 return err
 909                         }
 910
 911                         // // Copy N bytes from file to connection
 912                         // _, err = io.CopyN(conn, file, int64(binary.BigEndian.Uint32(ffo.FlatFileDataForkHeader.DataSize[:])))
 913                         // if err != nil {
 914                         //      return err
 915                         // }
 916                         // file.Close()
 917                         sendBuffer := make([]byte, 1048576)
 918                         var totalSent int64
 919                         for {
 920                                 var bytesRead int
 921                                 if bytesRead, err = file.ReadAt(sendBuffer, dataOffset+totalSent); err == io.EOF {
 922                                         if _, err := conn.Write(sendBuffer[:bytesRead]); err != nil {
 923                                                 return err
 924                                         }
 925                                         break
 926                                 }
 927                                 if err != nil {
 928                                         panic(err)
 929                                 }
 930                                 totalSent += int64(bytesRead)
 931
 932                                 fileTransfer.BytesSent += bytesRead
 933
 934                                 if _, err := conn.Write(sendBuffer[:bytesRead]); err != nil {
 935                                         return err
 936                                 }
 937                         }
 938
 939                         // TODO: optionally send resource fork header and resource fork data
 940
 941                         // Read the client's Next Action request.  This is always 3, I think?
 942                         if _, err := io.ReadFull(conn, nextAction); err != nil {
 943                                 return err
 944                         }
 945
 946                         return nil
 947                 })
 948
 949         case FolderUpload:
 950                 dstPath, err := readPath(s.Config.FileRoot, fileTransfer.FilePath, fileTransfer.FileName)
 951                 if err != nil {
 952                         return err
 953                 }
 954                 s.Logger.Infow(
 955                         "Folder upload started",
 956                         "transactionRef", fileTransfer.ReferenceNumber,
 957                         "dstPath", dstPath,
 958                         "TransferSize", fmt.Sprintf("%x", fileTransfer.TransferSize),
 959                         "FolderItemCount", fileTransfer.FolderItemCount,
 960                 )
 961
 962                 // Check if the target folder exists.  If not, create it.
 963                 if _, err := FS.Stat(dstPath); os.IsNotExist(err) {
 964                         if err := FS.Mkdir(dstPath, 0777); err != nil {
 965                                 return err
 966                         }
 967                 }
 968
 969                 // Begin the folder upload flow by sending the "next file action" to client
 970                 if _, err := conn.Write([]byte{0, dlFldrActionNextFile}); err != nil {
 971                         return err
 972                 }
 973
 974                 fileSize := make([]byte, 4)
 975                 readBuffer := make([]byte, 1024)
 976
 977                 for i := 0; i < fileTransfer.ItemCount(); i++ {
 978                         // TODO: fix potential short read with io.ReadFull
 979                         _, err := conn.Read(readBuffer)
 980                         if err != nil {
 981                                 return err
 982                         }
 983                         fu := readFolderUpload(readBuffer)
 984
 985                         s.Logger.Infow(
 986                                 "Folder upload continued",
 987                                 "transactionRef", fmt.Sprintf("%x", fileTransfer.ReferenceNumber),
 988                                 "FormattedPath", fu.FormattedPath(),
 989                                 "IsFolder", fmt.Sprintf("%x", fu.IsFolder),
 990                                 "PathItemCount", binary.BigEndian.Uint16(fu.PathItemCount[:]),
 991                         )
 992
 993                         if fu.IsFolder == [2]byte{0, 1} {
 994                                 if _, err := os.Stat(dstPath + "/" + fu.FormattedPath()); os.IsNotExist(err) {
 995                                         if err := os.Mkdir(dstPath+"/"+fu.FormattedPath(), 0777); err != nil {
 996                                                 return err
 997                                         }
 998                                 }
 999
1000                                 // Tell client to send next file
1001                                 if _, err := conn.Write([]byte{0, dlFldrActionNextFile}); err != nil {
1002                                         return err
1003                                 }
1004                         } else {
1005                                 nextAction := dlFldrActionSendFile
1006
1007                                 // Check if we have the full file already.  If so, send dlFldrAction_NextFile to client to skip.
1008                                 _, err := os.Stat(dstPath + "/" + fu.FormattedPath())
1009                                 if err != nil && !errors.Is(err, fs.ErrNotExist) {
1010                                         return err
1011                                 }
1012                                 if err == nil {
1013                                         nextAction = dlFldrActionNextFile
1014                                 }
1015
1016                                 //  Check if we have a partial file already.  If so, send dlFldrAction_ResumeFile to client to resume upload.
1017                                 inccompleteFile, err := os.Stat(dstPath + "/" + fu.FormattedPath() + incompleteFileSuffix)
1018                                 if err != nil && !errors.Is(err, fs.ErrNotExist) {
1019                                         return err
1020                                 }
1021                                 if err == nil {
1022                                         nextAction = dlFldrActionResumeFile
1023                                 }
1024
1025                                 fmt.Printf("Next Action: %v\n", nextAction)
1026
1027                                 if _, err := conn.Write([]byte{0, uint8(nextAction)}); err != nil {
1028                                         return err
1029                                 }
1030
1031                                 switch nextAction {
1032                                 case dlFldrActionNextFile:
1033                                         continue
1034                                 case dlFldrActionResumeFile:
1035                                         offset := make([]byte, 4)
1036                                         binary.BigEndian.PutUint32(offset, uint32(inccompleteFile.Size()))
1037
1038                                         file, err := os.OpenFile(dstPath+"/"+fu.FormattedPath()+incompleteFileSuffix, os.O_APPEND|os.O_CREATE|os.O_WRONLY, 0644)
1039                                         if err != nil {
1040                                                 return err
1041                                         }
1042
1043                                         fileResumeData := NewFileResumeData([]ForkInfoList{
1044                                                 *NewForkInfoList(offset),
1045                                         })
1046
1047                                         b, _ := fileResumeData.BinaryMarshal()
1048
1049                                         bs := make([]byte, 2)
1050                                         binary.BigEndian.PutUint16(bs, uint16(len(b)))
1051
1052                                         if _, err := conn.Write(append(bs, b...)); err != nil {
1053                                                 return err
1054                                         }
1055
1056                                         if _, err := io.ReadFull(conn, fileSize); err != nil {
1057                                                 return err
1058                                         }
1059
1060                                         if err := receiveFile(conn, file, ioutil.Discard); err != nil {
1061                                                 s.Logger.Error(err)
1062                                         }
1063
1064                                         err = os.Rename(dstPath+"/"+fu.FormattedPath()+".incomplete", dstPath+"/"+fu.FormattedPath())
1065                                         if err != nil {
1066                                                 return err
1067                                         }
1068
1069                                 case dlFldrActionSendFile:
1070                                         if _, err := conn.Read(fileSize); err != nil {
1071                                                 return err
1072                                         }
1073
1074                                         filePath := dstPath + "/" + fu.FormattedPath()
1075                                         s.Logger.Infow("Starting file transfer", "path", filePath, "fileNum", i+1, "totalFiles", "zz", "fileSize", binary.BigEndian.Uint32(fileSize))
1076
1077                                         newFile, err := FS.Create(filePath + ".incomplete")
1078                                         if err != nil {
1079                                                 return err
1080                                         }
1081
1082                                         if err := receiveFile(conn, newFile, ioutil.Discard); err != nil {
1083                                                 s.Logger.Error(err)
1084                                         }
1085                                         _ = newFile.Close()
1086                                         if err := os.Rename(filePath+".incomplete", filePath); err != nil {
1087                                                 return err
1088                                         }
1089                                 }
1090
1091                                 // Tell client to send next file
1092                                 if _, err := conn.Write([]byte{0, dlFldrActionNextFile}); err != nil {
1093                                         return err
1094                                 }
1095                         }
1096                 }
1097                 s.Logger.Infof("Folder upload complete")
1098         }
1099
1100         return nil
1101 }
1102
1103 // sortedClients is a utility function that takes a map of *ClientConn and returns a sorted slice of the values.
1104 // The purpose of this is to ensure that the ordering of client connections is deterministic so that test assertions work.
1105 func sortedClients(unsortedClients map[uint16]*ClientConn) (clients []*ClientConn) {
1106         for _, c := range unsortedClients {
1107                 clients = append(clients, c)
1108         }
1109         sort.Sort(byClientID(clients))
1110         return clients
1111 }