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.Connection.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); 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                 go func() {
 240                         for {
 241                                 tr := TrackerRegistration{
 242                                         Port:        []byte{0x15, 0x7c},
 243                                         UserCount:   server.userCount(),
 244                                         PassID:      server.TrackerPassID,
 245                                         Name:        server.Config.Name,
 246                                         Description: server.Config.Description,
 247                                 }
 248                                 for _, t := range server.Config.Trackers {
 249                                         server.Logger.Infof("Registering with tracker %v", t)
 250
 251                                         if err := register(t, tr); err != nil {
 252                                                 server.Logger.Errorw("unable to register with tracker %v", "error", err)
 253                                         }
 254                                 }
 255
 256                                 time.Sleep(trackerUpdateFrequency * time.Second)
 257                         }
 258                 }()
 259         }
 260
 261         // Start Client Keepalive go routine
 262         go server.keepaliveHandler()
 263
 264         return &server, nil
 265 }
 266
 267 func (s *Server) userCount() int {
 268         s.mux.Lock()
 269         defer s.mux.Unlock()
 270
 271         return len(s.Clients)
 272 }
 273
 274 func (s *Server) keepaliveHandler() {
 275         for {
 276                 time.Sleep(idleCheckInterval * time.Second)
 277                 s.mux.Lock()
 278
 279                 for _, c := range s.Clients {
 280                         c.IdleTime += idleCheckInterval
 281                         if c.IdleTime > userIdleSeconds && !c.Idle {
 282                                 c.Idle = true
 283
 284                                 flagBitmap := big.NewInt(int64(binary.BigEndian.Uint16(*c.Flags)))
 285                                 flagBitmap.SetBit(flagBitmap, userFlagAway, 1)
 286                                 binary.BigEndian.PutUint16(*c.Flags, uint16(flagBitmap.Int64()))
 287
 288                                 c.sendAll(
 289                                         tranNotifyChangeUser,
 290                                         NewField(fieldUserID, *c.ID),
 291                                         NewField(fieldUserFlags, *c.Flags),
 292                                         NewField(fieldUserName, c.UserName),
 293                                         NewField(fieldUserIconID, *c.Icon),
 294                                 )
 295                         }
 296                 }
 297                 s.mux.Unlock()
 298         }
 299 }
 300
 301 func (s *Server) writeThreadedNews() error {
 302         s.mux.Lock()
 303         defer s.mux.Unlock()
 304
 305         out, err := yaml.Marshal(s.ThreadedNews)
 306         if err != nil {
 307                 return err
 308         }
 309         err = ioutil.WriteFile(
 310                 s.ConfigDir+"ThreadedNews.yaml",
 311                 out,
 312                 0666,
 313         )
 314         return err
 315 }
 316
 317 func (s *Server) NewClientConn(conn net.Conn) *ClientConn {
 318         s.mux.Lock()
 319         defer s.mux.Unlock()
 320
 321         clientConn := &ClientConn{
 322                 ID:         &[]byte{0, 0},
 323                 Icon:       &[]byte{0, 0},
 324                 Flags:      &[]byte{0, 0},
 325                 UserName:   []byte{},
 326                 Connection: conn,
 327                 Server:     s,
 328                 Version:    &[]byte{},
 329                 AutoReply:  []byte{},
 330                 Transfers:  make(map[int][]*FileTransfer),
 331                 Agreed:     false,
 332         }
 333         *s.NextGuestID++
 334         ID := *s.NextGuestID
 335
 336         binary.BigEndian.PutUint16(*clientConn.ID, ID)
 337         s.Clients[ID] = clientConn
 338
 339         return clientConn
 340 }
 341
 342 // NewUser creates a new user account entry in the server map and config file
 343 func (s *Server) NewUser(login, name, password string, access []byte) error {
 344         s.mux.Lock()
 345         defer s.mux.Unlock()
 346
 347         account := Account{
 348                 Login:    login,
 349                 Name:     name,
 350                 Password: hashAndSalt([]byte(password)),
 351                 Access:   &access,
 352         }
 353         out, err := yaml.Marshal(&account)
 354         if err != nil {
 355                 return err
 356         }
 357         s.Accounts[login] = &account
 358
 359         return FS.WriteFile(s.ConfigDir+"Users/"+login+".yaml", out, 0666)
 360 }
 361
 362 // DeleteUser deletes the user account
 363 func (s *Server) DeleteUser(login string) error {
 364         s.mux.Lock()
 365         defer s.mux.Unlock()
 366
 367         delete(s.Accounts, login)
 368
 369         return FS.Remove(s.ConfigDir + "Users/" + login + ".yaml")
 370 }
 371
 372 func (s *Server) connectedUsers() []Field {
 373         s.mux.Lock()
 374         defer s.mux.Unlock()
 375
 376         var connectedUsers []Field
 377         for _, c := range sortedClients(s.Clients) {
 378                 if !c.Agreed {
 379                         continue
 380                 }
 381                 user := User{
 382                         ID:    *c.ID,
 383                         Icon:  *c.Icon,
 384                         Flags: *c.Flags,
 385                         Name:  string(c.UserName),
 386                 }
 387                 connectedUsers = append(connectedUsers, NewField(fieldUsernameWithInfo, user.Payload()))
 388         }
 389         return connectedUsers
 390 }
 391
 392 // loadThreadedNews loads the threaded news data from disk
 393 func (s *Server) loadThreadedNews(threadedNewsPath string) error {
 394         fh, err := os.Open(threadedNewsPath)
 395         if err != nil {
 396                 return err
 397         }
 398         decoder := yaml.NewDecoder(fh)
 399
 400         return decoder.Decode(s.ThreadedNews)
 401 }
 402
 403 // loadAccounts loads account data from disk
 404 func (s *Server) loadAccounts(userDir string) error {
 405         matches, err := filepath.Glob(path.Join(userDir, "*.yaml"))
 406         if err != nil {
 407                 return err
 408         }
 409
 410         if len(matches) == 0 {
 411                 return errors.New("no user accounts found in " + userDir)
 412         }
 413
 414         for _, file := range matches {
 415                 fh, err := FS.Open(file)
 416                 if err != nil {
 417                         return err
 418                 }
 419
 420                 account := Account{}
 421                 decoder := yaml.NewDecoder(fh)
 422                 if err := decoder.Decode(&account); err != nil {
 423                         return err
 424                 }
 425
 426                 s.Accounts[account.Login] = &account
 427         }
 428         return nil
 429 }
 430
 431 func (s *Server) loadConfig(path string) error {
 432         fh, err := FS.Open(path)
 433         if err != nil {
 434                 return err
 435         }
 436
 437         decoder := yaml.NewDecoder(fh)
 438         err = decoder.Decode(s.Config)
 439         if err != nil {
 440                 return err
 441         }
 442         return nil
 443 }
 444
 445 const (
 446         minTransactionLen = 22 // minimum length of any transaction
 447 )
 448
 449 // handleNewConnection takes a new net.Conn and performs the initial login sequence
 450 func (s *Server) handleNewConnection(conn net.Conn) error {
 451         handshakeBuf := make([]byte, 12) // handshakes are always 12 bytes in length
 452         if _, err := conn.Read(handshakeBuf); err != nil {
 453                 return err
 454         }
 455         if err := Handshake(conn, handshakeBuf[:12]); err != nil {
 456                 return err
 457         }
 458
 459         buf := make([]byte, 1024)
 460         readLen, err := conn.Read(buf)
 461         if readLen < minTransactionLen {
 462                 return err
 463         }
 464         if err != nil {
 465                 return err
 466         }
 467
 468         clientLogin, _, err := ReadTransaction(buf[:readLen])
 469         if err != nil {
 470                 return err
 471         }
 472
 473         c := s.NewClientConn(conn)
 474         defer c.Disconnect()
 475         defer func() {
 476                 if r := recover(); r != nil {
 477                         fmt.Println("stacktrace from panic: \n" + string(debug.Stack()))
 478                         c.Server.Logger.Errorw("PANIC", "err", r, "trace", string(debug.Stack()))
 479                         c.Disconnect()
 480                 }
 481         }()
 482
 483         encodedLogin := clientLogin.GetField(fieldUserLogin).Data
 484         encodedPassword := clientLogin.GetField(fieldUserPassword).Data
 485         *c.Version = clientLogin.GetField(fieldVersion).Data
 486
 487         var login string
 488         for _, char := range encodedLogin {
 489                 login += string(rune(255 - uint(char)))
 490         }
 491         if login == "" {
 492                 login = GuestAccount
 493         }
 494
 495         // If authentication fails, send error reply and close connection
 496         if !c.Authenticate(login, encodedPassword) {
 497                 t := c.NewErrReply(clientLogin, "Incorrect login.")
 498                 b, err := t.MarshalBinary()
 499                 if err != nil {
 500                         return err
 501                 }
 502                 if _, err := conn.Write(b); err != nil {
 503                         return err
 504                 }
 505                 return fmt.Errorf("incorrect login")
 506         }
 507
 508         if clientLogin.GetField(fieldUserName).Data != nil {
 509                 c.UserName = clientLogin.GetField(fieldUserName).Data
 510         }
 511
 512         if clientLogin.GetField(fieldUserIconID).Data != nil {
 513                 *c.Icon = clientLogin.GetField(fieldUserIconID).Data
 514         }
 515
 516         c.Account = c.Server.Accounts[login]
 517
 518         if c.Authorize(accessDisconUser) {
 519                 *c.Flags = []byte{0, 2}
 520         }
 521
 522         s.Logger.Infow("Client connection received", "login", login, "version", *c.Version, "RemoteAddr", conn.RemoteAddr().String())
 523
 524         s.outbox <- c.NewReply(clientLogin,
 525                 NewField(fieldVersion, []byte{0x00, 0xbe}),
 526                 NewField(fieldCommunityBannerID, []byte{0x00, 0x01}),
 527                 NewField(fieldServerName, []byte(s.Config.Name)),
 528         )
 529
 530         // Send user access privs so client UI knows how to behave
 531         c.Server.outbox <- *NewTransaction(tranUserAccess, c.ID, NewField(fieldUserAccess, *c.Account.Access))
 532
 533         // Show agreement to client
 534         c.Server.outbox <- *NewTransaction(tranShowAgreement, c.ID, NewField(fieldData, s.Agreement))
 535
 536         // assume simplified hotline v1.2.3 login flow that does not require agreement
 537         if *c.Version == nil {
 538                 c.Agreed = true
 539
 540                 c.notifyOthers(
 541                         *NewTransaction(
 542                                 tranNotifyChangeUser, nil,
 543                                 NewField(fieldUserName, c.UserName),
 544                                 NewField(fieldUserID, *c.ID),
 545                                 NewField(fieldUserIconID, *c.Icon),
 546                                 NewField(fieldUserFlags, *c.Flags),
 547                         ),
 548                 )
 549         }
 550
 551         c.Server.Stats.LoginCount += 1
 552
 553         const readBuffSize = 1024000 // 1KB - TODO: what should this be?
 554         tranBuff := make([]byte, 0)
 555         tReadlen := 0
 556         // Infinite loop where take action on incoming client requests until the connection is closed
 557         for {
 558                 buf = make([]byte, readBuffSize)
 559                 tranBuff = tranBuff[tReadlen:]
 560
 561                 readLen, err := c.Connection.Read(buf)
 562                 if err != nil {
 563                         return err
 564                 }
 565                 tranBuff = append(tranBuff, buf[:readLen]...)
 566
 567                 // We may have read multiple requests worth of bytes from Connection.Read.  readTransactions splits them
 568                 // into a slice of transactions
 569                 var transactions []Transaction
 570                 if transactions, tReadlen, err = readTransactions(tranBuff); err != nil {
 571                         c.Server.Logger.Errorw("Error handling transaction", "err", err)
 572                 }
 573
 574                 // iterate over all of the transactions that were parsed from the byte slice and handle them
 575                 for _, t := range transactions {
 576                         if err := c.handleTransaction(&t); err != nil {
 577                                 c.Server.Logger.Errorw("Error handling transaction", "err", err)
 578                         }
 579                 }
 580         }
 581 }
 582
 583 // NewTransactionRef generates a random ID for the file transfer.  The Hotline client includes this ID
 584 // in the file transfer request payload, and the file transfer server will use it to map the request
 585 // to a transfer
 586 func (s *Server) NewTransactionRef() []byte {
 587         transactionRef := make([]byte, 4)
 588         rand.Read(transactionRef)
 589
 590         return transactionRef
 591 }
 592
 593 func (s *Server) NewPrivateChat(cc *ClientConn) []byte {
 594         s.mux.Lock()
 595         defer s.mux.Unlock()
 596
 597         randID := make([]byte, 4)
 598         rand.Read(randID)
 599         data := binary.BigEndian.Uint32(randID[:])
 600
 601         s.PrivateChats[data] = &PrivateChat{
 602                 Subject:    "",
 603                 ClientConn: make(map[uint16]*ClientConn),
 604         }
 605         s.PrivateChats[data].ClientConn[cc.uint16ID()] = cc
 606
 607         return randID
 608 }
 609
 610 const dlFldrActionSendFile = 1
 611 const dlFldrActionResumeFile = 2
 612 const dlFldrActionNextFile = 3
 613
 614 // handleFileTransfer receives a client net.Conn from the file transfer server, performs the requested transfer type, then closes the connection
 615 func (s *Server) handleFileTransfer(conn io.ReadWriteCloser) error {
 616         defer func() {
 617                 if err := conn.Close(); err != nil {
 618                         s.Logger.Errorw("error closing connection", "error", err)
 619                 }
 620         }()
 621
 622         txBuf := make([]byte, 16)
 623         _, err := conn.Read(txBuf)
 624         if err != nil {
 625                 return err
 626         }
 627
 628         var t transfer
 629         _, err = t.Write(txBuf)
 630         if err != nil {
 631                 return err
 632         }
 633
 634         transferRefNum := binary.BigEndian.Uint32(t.ReferenceNumber[:])
 635         fileTransfer := s.FileTransfers[transferRefNum]
 636
 637         // delete single use transferRefNum
 638         delete(s.FileTransfers, transferRefNum)
 639
 640         switch fileTransfer.Type {
 641         case FileDownload:
 642                 fullFilePath, err := readPath(s.Config.FileRoot, fileTransfer.FilePath, fileTransfer.FileName)
 643                 if err != nil {
 644                         return err
 645                 }
 646
 647                 var dataOffset int64
 648                 if fileTransfer.fileResumeData != nil {
 649                         dataOffset = int64(binary.BigEndian.Uint32(fileTransfer.fileResumeData.ForkInfoList[0].DataSize[:]))
 650                 }
 651
 652                 ffo, err := NewFlattenedFileObject(s.Config.FileRoot, fileTransfer.FilePath, fileTransfer.FileName, dataOffset)
 653                 if err != nil {
 654                         return err
 655                 }
 656
 657                 s.Logger.Infow("File download started", "filePath", fullFilePath, "transactionRef", fileTransfer.ReferenceNumber)
 658
 659                 // Start by sending flat file object to client
 660                 if _, err := conn.Write(ffo.BinaryMarshal()); err != nil {
 661                         return err
 662                 }
 663
 664                 file, err := FS.Open(fullFilePath)
 665                 if err != nil {
 666                         return err
 667                 }
 668
 669                 sendBuffer := make([]byte, 1048576)
 670                 var totalSent int64
 671                 for {
 672                         var bytesRead int
 673                         if bytesRead, err = file.ReadAt(sendBuffer, dataOffset+totalSent); err == io.EOF {
 674                                 if _, err := conn.Write(sendBuffer[:bytesRead]); err != nil {
 675                                         return err
 676                                 }
 677                                 break
 678                         }
 679                         if err != nil {
 680                                 return err
 681                         }
 682                         totalSent += int64(bytesRead)
 683
 684                         fileTransfer.BytesSent += bytesRead
 685
 686                         if _, err := conn.Write(sendBuffer[:bytesRead]); err != nil {
 687                                 return err
 688                         }
 689                 }
 690         case FileUpload:
 691                 destinationFile := s.Config.FileRoot + ReadFilePath(fileTransfer.FilePath) + "/" + string(fileTransfer.FileName)
 692                 tmpFile := destinationFile + ".incomplete"
 693
 694                 file, err := effectiveFile(destinationFile)
 695                 if errors.Is(err, fs.ErrNotExist) {
 696                         file, err = FS.Create(tmpFile)
 697                         if err != nil {
 698                                 return err
 699                         }
 700                 }
 701
 702                 defer func() { _ = file.Close() }()
 703
 704                 s.Logger.Infow("File upload started", "transactionRef", fileTransfer.ReferenceNumber, "dstFile", destinationFile)
 705
 706                 // TODO: replace io.Discard with a real file when ready to implement storing of resource fork data
 707                 if err := receiveFile(conn, file, io.Discard); err != nil {
 708                         return err
 709                 }
 710
 711                 if err := os.Rename(destinationFile+".incomplete", destinationFile); err != nil {
 712                         return err
 713                 }
 714
 715                 s.Logger.Infow("File upload complete", "transactionRef", fileTransfer.ReferenceNumber, "dstFile", destinationFile)
 716         case FolderDownload:
 717                 // Folder Download flow:
 718                 // 1. Get filePath from the transfer
 719                 // 2. Iterate over files
 720                 // 3. For each file:
 721                 //       Send file header to client
 722                 // The client can reply in 3 ways:
 723                 //
 724                 // 1. If type is an odd number (unknown type?), or file download for the current file is completed:
 725                 //              client sends []byte{0x00, 0x03} to tell the server to continue to the next file
 726                 //
 727                 // 2. If download of a file is to be resumed:
 728                 //              client sends:
 729                 //                      []byte{0x00, 0x02} // download folder action
 730                 //                      [2]byte // Resume data size
 731                 //                      []byte file resume data (see myField_FileResumeData)
 732                 //
 733                 // 3. Otherwise, download of the file is requested and client sends []byte{0x00, 0x01}
 734                 //
 735                 // When download is requested (case 2 or 3), server replies with:
 736                 //                      [4]byte - file size
 737                 //                      []byte  - Flattened File Object
 738                 //
 739                 // After every file download, client could request next file with:
 740                 //                      []byte{0x00, 0x03}
 741                 //
 742                 // This notifies the server to send the next item header
 743
 744                 fullFilePath, err := readPath(s.Config.FileRoot, fileTransfer.FilePath, fileTransfer.FileName)
 745                 if err != nil {
 746                         return err
 747                 }
 748
 749                 basePathLen := len(fullFilePath)
 750
 751                 s.Logger.Infow("Start folder download", "path", fullFilePath, "ReferenceNumber", fileTransfer.ReferenceNumber)
 752
 753                 nextAction := make([]byte, 2)
 754                 if _, err := conn.Read(nextAction); err != nil {
 755                         return err
 756                 }
 757
 758                 i := 0
 759                 err = filepath.Walk(fullFilePath+"/", func(path string, info os.FileInfo, err error) error {
 760                         if err != nil {
 761                                 return err
 762                         }
 763                         i += 1
 764                         subPath := path[basePathLen+1:]
 765                         s.Logger.Infow("Sending fileheader", "i", i, "path", path, "fullFilePath", fullFilePath, "subPath", subPath, "IsDir", info.IsDir())
 766
 767                         if i == 1 {
 768                                 return nil
 769                         }
 770
 771                         fileHeader := NewFileHeader(subPath, info.IsDir())
 772
 773                         // Send the file header to client
 774                         if _, err := conn.Write(fileHeader.Payload()); err != nil {
 775                                 s.Logger.Errorf("error sending file header: %v", err)
 776                                 return err
 777                         }
 778
 779                         // Read the client's Next Action request
 780                         if _, err := conn.Read(nextAction); err != nil {
 781                                 return err
 782                         }
 783
 784                         s.Logger.Infow("Client folder download action", "action", fmt.Sprintf("%X", nextAction[0:2]))
 785
 786                         var dataOffset int64
 787
 788                         switch nextAction[1] {
 789                         case dlFldrActionResumeFile:
 790                                 // client asked to resume this file
 791                                 var frd FileResumeData
 792                                 // get size of resumeData
 793                                 if _, err := conn.Read(nextAction); err != nil {
 794                                         return err
 795                                 }
 796
 797                                 resumeDataLen := binary.BigEndian.Uint16(nextAction)
 798                                 resumeDataBytes := make([]byte, resumeDataLen)
 799                                 if _, err := conn.Read(resumeDataBytes); err != nil {
 800                                         return err
 801                                 }
 802
 803                                 if err := frd.UnmarshalBinary(resumeDataBytes); err != nil {
 804                                         return err
 805                                 }
 806                                 dataOffset = int64(binary.BigEndian.Uint32(frd.ForkInfoList[0].DataSize[:]))
 807                         case dlFldrActionNextFile:
 808                                 // client asked to skip this file
 809                                 return nil
 810                         }
 811
 812                         if info.IsDir() {
 813                                 return nil
 814                         }
 815
 816                         splitPath := strings.Split(path, "/")
 817
 818                         ffo, err := NewFlattenedFileObject(strings.Join(splitPath[:len(splitPath)-1], "/"), nil, []byte(info.Name()), dataOffset)
 819                         if err != nil {
 820                                 return err
 821                         }
 822                         s.Logger.Infow("File download started",
 823                                 "fileName", info.Name(),
 824                                 "transactionRef", fileTransfer.ReferenceNumber,
 825                                 "TransferSize", fmt.Sprintf("%x", ffo.TransferSize()),
 826                         )
 827
 828                         // Send file size to client
 829                         if _, err := conn.Write(ffo.TransferSize()); err != nil {
 830                                 s.Logger.Error(err)
 831                                 return err
 832                         }
 833
 834                         // Send ffo bytes to client
 835                         if _, err := conn.Write(ffo.BinaryMarshal()); err != nil {
 836                                 s.Logger.Error(err)
 837                                 return err
 838                         }
 839
 840                         file, err := FS.Open(path)
 841                         if err != nil {
 842                                 return err
 843                         }
 844
 845                         // // Copy N bytes from file to connection
 846                         // _, err = io.CopyN(conn, file, int64(binary.BigEndian.Uint32(ffo.FlatFileDataForkHeader.DataSize[:])))
 847                         // if err != nil {
 848                         //      return err
 849                         // }
 850                         // file.Close()
 851                         sendBuffer := make([]byte, 1048576)
 852                         var totalSent int64
 853                         for {
 854                                 var bytesRead int
 855                                 if bytesRead, err = file.ReadAt(sendBuffer, dataOffset+totalSent); err == io.EOF {
 856                                         if _, err := conn.Write(sendBuffer[:bytesRead]); err != nil {
 857                                                 return err
 858                                         }
 859                                         break
 860                                 }
 861                                 if err != nil {
 862                                         panic(err)
 863                                 }
 864                                 totalSent += int64(bytesRead)
 865
 866                                 fileTransfer.BytesSent += bytesRead
 867
 868                                 if _, err := conn.Write(sendBuffer[:bytesRead]); err != nil {
 869                                         return err
 870                                 }
 871                         }
 872
 873                         // TODO: optionally send resource fork header and resource fork data
 874
 875                         // Read the client's Next Action request.  This is always 3, I think?
 876                         if _, err := conn.Read(nextAction); err != nil {
 877                                 return err
 878                         }
 879
 880                         return nil
 881                 })
 882
 883         case FolderUpload:
 884                 dstPath, err := readPath(s.Config.FileRoot, fileTransfer.FilePath, fileTransfer.FileName)
 885                 if err != nil {
 886                         return err
 887                 }
 888                 s.Logger.Infow(
 889                         "Folder upload started",
 890                         "transactionRef", fileTransfer.ReferenceNumber,
 891                         "dstPath", dstPath,
 892                         "TransferSize", fmt.Sprintf("%x", fileTransfer.TransferSize),
 893                         "FolderItemCount", fileTransfer.FolderItemCount,
 894                 )
 895
 896                 // Check if the target folder exists.  If not, create it.
 897                 if _, err := FS.Stat(dstPath); os.IsNotExist(err) {
 898                         if err := FS.Mkdir(dstPath, 0777); err != nil {
 899                                 return err
 900                         }
 901                 }
 902
 903                 // Begin the folder upload flow by sending the "next file action" to client
 904                 if _, err := conn.Write([]byte{0, dlFldrActionNextFile}); err != nil {
 905                         return err
 906                 }
 907
 908                 fileSize := make([]byte, 4)
 909                 readBuffer := make([]byte, 1024)
 910
 911                 for i := 0; i < fileTransfer.ItemCount(); i++ {
 912
 913                         _, err := conn.Read(readBuffer)
 914                         if err != nil {
 915                                 return err
 916                         }
 917                         fu := readFolderUpload(readBuffer)
 918
 919                         s.Logger.Infow(
 920                                 "Folder upload continued",
 921                                 "transactionRef", fmt.Sprintf("%x", fileTransfer.ReferenceNumber),
 922                                 "FormattedPath", fu.FormattedPath(),
 923                                 "IsFolder", fmt.Sprintf("%x", fu.IsFolder),
 924                                 "PathItemCount", binary.BigEndian.Uint16(fu.PathItemCount[:]),
 925                         )
 926
 927                         if fu.IsFolder == [2]byte{0, 1} {
 928                                 if _, err := os.Stat(dstPath + "/" + fu.FormattedPath()); os.IsNotExist(err) {
 929                                         if err := os.Mkdir(dstPath+"/"+fu.FormattedPath(), 0777); err != nil {
 930                                                 return err
 931                                         }
 932                                 }
 933
 934                                 // Tell client to send next file
 935                                 if _, err := conn.Write([]byte{0, dlFldrActionNextFile}); err != nil {
 936                                         return err
 937                                 }
 938                         } else {
 939                                 nextAction := dlFldrActionSendFile
 940
 941                                 // Check if we have the full file already.  If so, send dlFldrAction_NextFile to client to skip.
 942                                 _, err := os.Stat(dstPath + "/" + fu.FormattedPath())
 943                                 if err != nil && !errors.Is(err, fs.ErrNotExist) {
 944                                         return err
 945                                 }
 946                                 if err == nil {
 947                                         nextAction = dlFldrActionNextFile
 948                                 }
 949
 950                                 //  Check if we have a partial file already.  If so, send dlFldrAction_ResumeFile to client to resume upload.
 951                                 inccompleteFile, err := os.Stat(dstPath + "/" + fu.FormattedPath() + incompleteFileSuffix)
 952                                 if err != nil && !errors.Is(err, fs.ErrNotExist) {
 953                                         return err
 954                                 }
 955                                 if err == nil {
 956                                         nextAction = dlFldrActionResumeFile
 957                                 }
 958
 959                                 fmt.Printf("Next Action: %v\n", nextAction)
 960
 961                                 if _, err := conn.Write([]byte{0, uint8(nextAction)}); err != nil {
 962                                         return err
 963                                 }
 964
 965                                 switch nextAction {
 966                                 case dlFldrActionNextFile:
 967                                         continue
 968                                 case dlFldrActionResumeFile:
 969                                         offset := make([]byte, 4)
 970                                         binary.BigEndian.PutUint32(offset, uint32(inccompleteFile.Size()))
 971
 972                                         file, err := os.OpenFile(dstPath+"/"+fu.FormattedPath()+incompleteFileSuffix, os.O_APPEND|os.O_CREATE|os.O_WRONLY, 0644)
 973                                         if err != nil {
 974                                                 return err
 975                                         }
 976
 977                                         fileResumeData := NewFileResumeData([]ForkInfoList{
 978                                                 *NewForkInfoList(offset),
 979                                         })
 980
 981                                         b, _ := fileResumeData.BinaryMarshal()
 982
 983                                         bs := make([]byte, 2)
 984                                         binary.BigEndian.PutUint16(bs, uint16(len(b)))
 985
 986                                         if _, err := conn.Write(append(bs, b...)); err != nil {
 987                                                 return err
 988                                         }
 989
 990                                         if _, err := conn.Read(fileSize); err != nil {
 991                                                 return err
 992                                         }
 993
 994                                         if err := receiveFile(conn, file, ioutil.Discard); err != nil {
 995                                                 s.Logger.Error(err)
 996                                         }
 997
 998                                         err = os.Rename(dstPath+"/"+fu.FormattedPath()+".incomplete", dstPath+"/"+fu.FormattedPath())
 999                                         if err != nil {
1000                                                 return err
1001                                         }
1002
1003                                 case dlFldrActionSendFile:
1004                                         if _, err := conn.Read(fileSize); err != nil {
1005                                                 return err
1006                                         }
1007
1008                                         filePath := dstPath + "/" + fu.FormattedPath()
1009                                         s.Logger.Infow("Starting file transfer", "path", filePath, "fileNum", i+1, "totalFiles", "zz", "fileSize", binary.BigEndian.Uint32(fileSize))
1010
1011                                         newFile, err := FS.Create(filePath + ".incomplete")
1012                                         if err != nil {
1013                                                 return err
1014                                         }
1015
1016                                         if err := receiveFile(conn, newFile, ioutil.Discard); err != nil {
1017                                                 s.Logger.Error(err)
1018                                         }
1019                                         _ = newFile.Close()
1020                                         if err := os.Rename(filePath+".incomplete", filePath); err != nil {
1021                                                 return err
1022                                         }
1023                                 }
1024
1025                                 // Tell client to send next file
1026                                 if _, err := conn.Write([]byte{0, dlFldrActionNextFile}); err != nil {
1027                                         return err
1028                                 }
1029                         }
1030                 }
1031                 s.Logger.Infof("Folder upload complete")
1032         }
1033
1034         return nil
1035 }
1036
1037 // sortedClients is a utility function that takes a map of *ClientConn and returns a sorted slice of the values.
1038 // The purpose of this is to ensure that the ordering of client connections is deterministic so that test assertions work.
1039 func sortedClients(unsortedClients map[uint16]*ClientConn) (clients []*ClientConn) {
1040         for _, c := range unsortedClients {
1041                 clients = append(clients, c)
1042         }
1043         sort.Sort(byClientID(clients))
1044         return clients
1045 }