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/ioutil"
  11         "math/big"
  12         "math/rand"
  13         "net"
  14         "os"
  15         "path"
  16         "path/filepath"
  17         "runtime/debug"
  18         "sort"
  19         "strings"
  20         "sync"
  21         "time"
  22
  23         "gopkg.in/yaml.v2"
  24 )
  25
  26 const (
  27         userIdleSeconds        = 300 // time in seconds before an inactive user is marked idle
  28         idleCheckInterval      = 10  // time in seconds to check for idle users
  29         trackerUpdateFrequency = 300 // time in seconds between tracker re-registration
  30 )
  31
  32 type Server struct {
  33         Port          int
  34         Accounts      map[string]*Account
  35         Agreement     []byte
  36         Clients       map[uint16]*ClientConn
  37         FlatNews      []byte
  38         ThreadedNews  *ThreadedNews
  39         FileTransfers map[uint32]*FileTransfer
  40         Config        *Config
  41         ConfigDir     string
  42         Logger        *zap.SugaredLogger
  43         PrivateChats  map[uint32]*PrivateChat
  44         NextGuestID   *uint16
  45         TrackerPassID []byte
  46         Stats         *Stats
  47
  48         APIListener  net.Listener
  49         FileListener net.Listener
  50
  51         // newsReader io.Reader
  52         // newsWriter io.WriteCloser
  53
  54         outbox chan Transaction
  55
  56         mux         sync.Mutex
  57         flatNewsMux sync.Mutex
  58 }
  59
  60 type PrivateChat struct {
  61         Subject    string
  62         ClientConn map[uint16]*ClientConn
  63 }
  64
  65 func (s *Server) ListenAndServe(ctx context.Context, cancelRoot context.CancelFunc) error {
  66         s.Logger.Infow("Hotline server started", "version", VERSION)
  67         var wg sync.WaitGroup
  68
  69         wg.Add(1)
  70         go func() { s.Logger.Fatal(s.Serve(ctx, cancelRoot, s.APIListener)) }()
  71
  72         wg.Add(1)
  73         go func() { s.Logger.Fatal(s.ServeFileTransfers(s.FileListener)) }()
  74
  75         wg.Wait()
  76
  77         return nil
  78 }
  79
  80 func (s *Server) APIPort() int {
  81         return s.APIListener.Addr().(*net.TCPAddr).Port
  82 }
  83
  84 func (s *Server) ServeFileTransfers(ln net.Listener) error {
  85         s.Logger.Infow("Hotline file transfer server started", "Addr", fmt.Sprintf(":%v", s.Port+1))
  86
  87         for {
  88                 conn, err := ln.Accept()
  89                 if err != nil {
  90                         return err
  91                 }
  92
  93                 go func() {
  94                         if err := s.TransferFile(conn); err != nil {
  95                                 s.Logger.Errorw("file transfer error", "reason", err)
  96                         }
  97                 }()
  98         }
  99 }
 100
 101 func (s *Server) sendTransaction(t Transaction) error {
 102         requestNum := binary.BigEndian.Uint16(t.Type)
 103         clientID, err := byteToInt(*t.clientID)
 104         if err != nil {
 105                 return err
 106         }
 107
 108         s.mux.Lock()
 109         client := s.Clients[uint16(clientID)]
 110         s.mux.Unlock()
 111         if client == nil {
 112                 return fmt.Errorf("invalid client id %v", *t.clientID)
 113         }
 114         userName := string(client.UserName)
 115         login := client.Account.Login
 116
 117         handler := TransactionHandlers[requestNum]
 118
 119         b, err := t.MarshalBinary()
 120         if err != nil {
 121                 return err
 122         }
 123         var n int
 124         if n, err = client.Connection.Write(b); err != nil {
 125                 return err
 126         }
 127         s.Logger.Debugw("Sent Transaction",
 128                 "name", userName,
 129                 "login", login,
 130                 "IsReply", t.IsReply,
 131                 "type", handler.Name,
 132                 "sentBytes", n,
 133                 "remoteAddr", client.Connection.RemoteAddr(),
 134         )
 135         return nil
 136 }
 137
 138 func (s *Server) Serve(ctx context.Context, cancelRoot context.CancelFunc, ln net.Listener) error {
 139         s.Logger.Infow("Hotline server started", "Addr", fmt.Sprintf(":%v", s.Port))
 140
 141         for {
 142                 conn, err := ln.Accept()
 143                 if err != nil {
 144                         s.Logger.Errorw("error accepting connection", "err", err)
 145                 }
 146
 147                 go func() {
 148                         for {
 149                                 t := <-s.outbox
 150                                 go func() {
 151                                         if err := s.sendTransaction(t); err != nil {
 152                                                 s.Logger.Errorw("error sending transaction", "err", err)
 153                                         }
 154                                 }()
 155                         }
 156                 }()
 157                 go func() {
 158                         if err := s.handleNewConnection(conn); err != nil {
 159                                 if err == io.EOF {
 160                                         s.Logger.Infow("Client disconnected", "RemoteAddr", conn.RemoteAddr())
 161                                 } else {
 162                                         s.Logger.Errorw("error serving request", "RemoteAddr", conn.RemoteAddr(), "err", err)
 163                                 }
 164                         }
 165                 }()
 166         }
 167 }
 168
 169 const (
 170         agreementFile = "Agreement.txt"
 171 )
 172
 173 // NewServer constructs a new Server from a config dir
 174 func NewServer(configDir, netInterface string, netPort int, logger *zap.SugaredLogger) (*Server, error) {
 175         server := Server{
 176                 Port:          netPort,
 177                 Accounts:      make(map[string]*Account),
 178                 Config:        new(Config),
 179                 Clients:       make(map[uint16]*ClientConn),
 180                 FileTransfers: make(map[uint32]*FileTransfer),
 181                 PrivateChats:  make(map[uint32]*PrivateChat),
 182                 ConfigDir:     configDir,
 183                 Logger:        logger,
 184                 NextGuestID:   new(uint16),
 185                 outbox:        make(chan Transaction),
 186                 Stats:         &Stats{StartTime: time.Now()},
 187                 ThreadedNews:  &ThreadedNews{},
 188                 TrackerPassID: make([]byte, 4),
 189         }
 190
 191         ln, err := net.Listen("tcp", fmt.Sprintf("%s:%v", netInterface, netPort))
 192         if err != nil {
 193                 return nil, err
 194         }
 195         server.APIListener = ln
 196
 197         if netPort != 0 {
 198                 netPort += 1
 199         }
 200
 201         ln2, err := net.Listen("tcp", fmt.Sprintf("%s:%v", netInterface, netPort))
 202         server.FileListener = ln2
 203         if err != nil {
 204                 return nil, err
 205         }
 206
 207         // generate a new random passID for tracker registration
 208         if _, err := rand.Read(server.TrackerPassID); err != nil {
 209                 return nil, err
 210         }
 211
 212         server.Logger.Debugw("Loading Agreement", "path", configDir+agreementFile)
 213         if server.Agreement, err = os.ReadFile(configDir + agreementFile); err != nil {
 214                 return nil, err
 215         }
 216
 217         if server.FlatNews, err = os.ReadFile(configDir + "MessageBoard.txt"); err != nil {
 218                 return nil, err
 219         }
 220
 221         if err := server.loadThreadedNews(configDir + "ThreadedNews.yaml"); err != nil {
 222                 return nil, err
 223         }
 224
 225         if err := server.loadConfig(configDir + "config.yaml"); err != nil {
 226                 return nil, err
 227         }
 228
 229         if err := server.loadAccounts(configDir + "Users/"); err != nil {
 230                 return nil, err
 231         }
 232
 233         server.Config.FileRoot = configDir + "Files/"
 234
 235         *server.NextGuestID = 1
 236
 237         if server.Config.EnableTrackerRegistration {
 238                 go func() {
 239                         for {
 240                                 tr := TrackerRegistration{
 241                                         Port:        []byte{0x15, 0x7c},
 242                                         UserCount:   server.userCount(),
 243                                         PassID:      server.TrackerPassID,
 244                                         Name:        server.Config.Name,
 245                                         Description: server.Config.Description,
 246                                 }
 247                                 for _, t := range server.Config.Trackers {
 248                                         server.Logger.Infof("Registering with tracker %v", t)
 249
 250                                         if err := register(t, tr); err != nil {
 251                                                 server.Logger.Errorw("unable to register with tracker %v", "error", err)
 252                                         }
 253                                 }
 254
 255                                 time.Sleep(trackerUpdateFrequency * time.Second)
 256                         }
 257                 }()
 258         }
 259
 260         // Start Client Keepalive go routine
 261         go server.keepaliveHandler()
 262
 263         return &server, nil
 264 }
 265
 266 func (s *Server) userCount() int {
 267         s.mux.Lock()
 268         defer s.mux.Unlock()
 269
 270         return len(s.Clients)
 271 }
 272
 273 func (s *Server) keepaliveHandler() {
 274         for {
 275                 time.Sleep(idleCheckInterval * time.Second)
 276                 s.mux.Lock()
 277
 278                 for _, c := range s.Clients {
 279                         c.IdleTime += idleCheckInterval
 280                         if c.IdleTime > userIdleSeconds && !c.Idle {
 281                                 c.Idle = true
 282
 283                                 flagBitmap := big.NewInt(int64(binary.BigEndian.Uint16(*c.Flags)))
 284                                 flagBitmap.SetBit(flagBitmap, userFlagAway, 1)
 285                                 binary.BigEndian.PutUint16(*c.Flags, uint16(flagBitmap.Int64()))
 286
 287                                 c.sendAll(
 288                                         tranNotifyChangeUser,
 289                                         NewField(fieldUserID, *c.ID),
 290                                         NewField(fieldUserFlags, *c.Flags),
 291                                         NewField(fieldUserName, c.UserName),
 292                                         NewField(fieldUserIconID, *c.Icon),
 293                                 )
 294                         }
 295                 }
 296                 s.mux.Unlock()
 297         }
 298 }
 299
 300 func (s *Server) writeThreadedNews() error {
 301         s.mux.Lock()
 302         defer s.mux.Unlock()
 303
 304         out, err := yaml.Marshal(s.ThreadedNews)
 305         if err != nil {
 306                 return err
 307         }
 308         err = ioutil.WriteFile(
 309                 s.ConfigDir+"ThreadedNews.yaml",
 310                 out,
 311                 0666,
 312         )
 313         return err
 314 }
 315
 316 func (s *Server) NewClientConn(conn net.Conn) *ClientConn {
 317         s.mux.Lock()
 318         defer s.mux.Unlock()
 319
 320         clientConn := &ClientConn{
 321                 ID:         &[]byte{0, 0},
 322                 Icon:       &[]byte{0, 0},
 323                 Flags:      &[]byte{0, 0},
 324                 UserName:   []byte{},
 325                 Connection: conn,
 326                 Server:     s,
 327                 Version:    &[]byte{},
 328                 AutoReply:  []byte{},
 329                 Transfers:  make(map[int][]*FileTransfer),
 330                 Agreed:     false,
 331         }
 332         *s.NextGuestID++
 333         ID := *s.NextGuestID
 334
 335         binary.BigEndian.PutUint16(*clientConn.ID, ID)
 336         s.Clients[ID] = clientConn
 337
 338         return clientConn
 339 }
 340
 341 // NewUser creates a new user account entry in the server map and config file
 342 func (s *Server) NewUser(login, name, password string, access []byte) error {
 343         s.mux.Lock()
 344         defer s.mux.Unlock()
 345
 346         account := Account{
 347                 Login:    login,
 348                 Name:     name,
 349                 Password: hashAndSalt([]byte(password)),
 350                 Access:   &access,
 351         }
 352         out, err := yaml.Marshal(&account)
 353         if err != nil {
 354                 return err
 355         }
 356         s.Accounts[login] = &account
 357
 358         return ioutil.WriteFile(s.ConfigDir+"Users/"+login+".yaml", out, 0666)
 359 }
 360
 361 // DeleteUser deletes the user account
 362 func (s *Server) DeleteUser(login string) error {
 363         s.mux.Lock()
 364         defer s.mux.Unlock()
 365
 366         delete(s.Accounts, login)
 367
 368         return FS.Remove(s.ConfigDir + "Users/" + login + ".yaml")
 369 }
 370
 371 func (s *Server) connectedUsers() []Field {
 372         s.mux.Lock()
 373         defer s.mux.Unlock()
 374
 375         var connectedUsers []Field
 376         for _, c := range sortedClients(s.Clients) {
 377                 if !c.Agreed {
 378                         continue
 379                 }
 380                 user := User{
 381                         ID:    *c.ID,
 382                         Icon:  *c.Icon,
 383                         Flags: *c.Flags,
 384                         Name:  string(c.UserName),
 385                 }
 386                 connectedUsers = append(connectedUsers, NewField(fieldUsernameWithInfo, user.Payload()))
 387         }
 388         return connectedUsers
 389 }
 390
 391 // loadThreadedNews loads the threaded news data from disk
 392 func (s *Server) loadThreadedNews(threadedNewsPath string) error {
 393         fh, err := os.Open(threadedNewsPath)
 394         if err != nil {
 395                 return err
 396         }
 397         decoder := yaml.NewDecoder(fh)
 398         decoder.SetStrict(true)
 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                 decoder.SetStrict(true)
 423                 if err := decoder.Decode(&account); err != nil {
 424                         return err
 425                 }
 426
 427                 s.Accounts[account.Login] = &account
 428         }
 429         return nil
 430 }
 431
 432 func (s *Server) loadConfig(path string) error {
 433         fh, err := FS.Open(path)
 434         if err != nil {
 435                 return err
 436         }
 437
 438         decoder := yaml.NewDecoder(fh)
 439         decoder.SetStrict(true)
 440         err = decoder.Decode(s.Config)
 441         if err != nil {
 442                 return err
 443         }
 444         return nil
 445 }
 446
 447 const (
 448         minTransactionLen = 22 // minimum length of any transaction
 449 )
 450
 451 // handleNewConnection takes a new net.Conn and performs the initial login sequence
 452 func (s *Server) handleNewConnection(conn net.Conn) error {
 453         handshakeBuf := make([]byte, 12) // handshakes are always 12 bytes in length
 454         if _, err := conn.Read(handshakeBuf); err != nil {
 455                 return err
 456         }
 457         if err := Handshake(conn, handshakeBuf[:12]); err != nil {
 458                 return err
 459         }
 460
 461         buf := make([]byte, 1024)
 462         readLen, err := conn.Read(buf)
 463         if readLen < minTransactionLen {
 464                 return err
 465         }
 466         if err != nil {
 467                 return err
 468         }
 469
 470         clientLogin, _, err := ReadTransaction(buf[:readLen])
 471         if err != nil {
 472                 return err
 473         }
 474
 475         c := s.NewClientConn(conn)
 476         defer c.Disconnect()
 477         defer func() {
 478                 if r := recover(); r != nil {
 479                         fmt.Println("stacktrace from panic: \n" + string(debug.Stack()))
 480                         c.Server.Logger.Errorw("PANIC", "err", r, "trace", string(debug.Stack()))
 481                         c.Disconnect()
 482                 }
 483         }()
 484
 485         encodedLogin := clientLogin.GetField(fieldUserLogin).Data
 486         encodedPassword := clientLogin.GetField(fieldUserPassword).Data
 487         *c.Version = clientLogin.GetField(fieldVersion).Data
 488
 489         var login string
 490         for _, char := range encodedLogin {
 491                 login += string(rune(255 - uint(char)))
 492         }
 493         if login == "" {
 494                 login = GuestAccount
 495         }
 496
 497         // If authentication fails, send error reply and close connection
 498         if !c.Authenticate(login, encodedPassword) {
 499                 t := c.NewErrReply(clientLogin, "Incorrect login.")
 500                 b, err := t.MarshalBinary()
 501                 if err != nil {
 502                         return err
 503                 }
 504                 if _, err := conn.Write(b); err != nil {
 505                         return err
 506                 }
 507                 return fmt.Errorf("incorrect login")
 508         }
 509
 510         if clientLogin.GetField(fieldUserName).Data != nil {
 511                 c.UserName = clientLogin.GetField(fieldUserName).Data
 512         }
 513
 514         if clientLogin.GetField(fieldUserIconID).Data != nil {
 515                 *c.Icon = clientLogin.GetField(fieldUserIconID).Data
 516         }
 517
 518         c.Account = c.Server.Accounts[login]
 519
 520         if c.Authorize(accessDisconUser) {
 521                 *c.Flags = []byte{0, 2}
 522         }
 523
 524         s.Logger.Infow("Client connection received", "login", login, "version", *c.Version, "RemoteAddr", conn.RemoteAddr().String())
 525
 526         s.outbox <- c.NewReply(clientLogin,
 527                 NewField(fieldVersion, []byte{0x00, 0xbe}),
 528                 NewField(fieldCommunityBannerID, []byte{0x00, 0x01}),
 529                 NewField(fieldServerName, []byte(s.Config.Name)),
 530         )
 531
 532         // Send user access privs so client UI knows how to behave
 533         c.Server.outbox <- *NewTransaction(tranUserAccess, c.ID, NewField(fieldUserAccess, *c.Account.Access))
 534
 535         // Show agreement to client
 536         c.Server.outbox <- *NewTransaction(tranShowAgreement, c.ID, NewField(fieldData, s.Agreement))
 537
 538         // assume simplified hotline v1.2.3 login flow that does not require agreement
 539         if *c.Version == nil {
 540                 c.Agreed = true
 541
 542                 c.notifyOthers(
 543                         *NewTransaction(
 544                                 tranNotifyChangeUser, nil,
 545                                 NewField(fieldUserName, c.UserName),
 546                                 NewField(fieldUserID, *c.ID),
 547                                 NewField(fieldUserIconID, *c.Icon),
 548                                 NewField(fieldUserFlags, *c.Flags),
 549                         ),
 550                 )
 551         }
 552
 553         c.Server.Stats.LoginCount += 1
 554
 555         const readBuffSize = 1024000 // 1KB - TODO: what should this be?
 556         tranBuff := make([]byte, 0)
 557         tReadlen := 0
 558         // Infinite loop where take action on incoming client requests until the connection is closed
 559         for {
 560                 buf = make([]byte, readBuffSize)
 561                 tranBuff = tranBuff[tReadlen:]
 562
 563                 readLen, err := c.Connection.Read(buf)
 564                 if err != nil {
 565                         return err
 566                 }
 567                 tranBuff = append(tranBuff, buf[:readLen]...)
 568
 569                 // We may have read multiple requests worth of bytes from Connection.Read.  readTransactions splits them
 570                 // into a slice of transactions
 571                 var transactions []Transaction
 572                 if transactions, tReadlen, err = readTransactions(tranBuff); err != nil {
 573                         c.Server.Logger.Errorw("Error handling transaction", "err", err)
 574                 }
 575
 576                 // iterate over all of the transactions that were parsed from the byte slice and handle them
 577                 for _, t := range transactions {
 578                         if err := c.handleTransaction(&t); err != nil {
 579                                 c.Server.Logger.Errorw("Error handling transaction", "err", err)
 580                         }
 581                 }
 582         }
 583 }
 584
 585 // NewTransactionRef generates a random ID for the file transfer.  The Hotline client includes this ID
 586 // in the file transfer request payload, and the file transfer server will use it to map the request
 587 // to a transfer
 588 func (s *Server) NewTransactionRef() []byte {
 589         transactionRef := make([]byte, 4)
 590         rand.Read(transactionRef)
 591
 592         return transactionRef
 593 }
 594
 595 func (s *Server) NewPrivateChat(cc *ClientConn) []byte {
 596         s.mux.Lock()
 597         defer s.mux.Unlock()
 598
 599         randID := make([]byte, 4)
 600         rand.Read(randID)
 601         data := binary.BigEndian.Uint32(randID[:])
 602
 603         s.PrivateChats[data] = &PrivateChat{
 604                 Subject:    "",
 605                 ClientConn: make(map[uint16]*ClientConn),
 606         }
 607         s.PrivateChats[data].ClientConn[cc.uint16ID()] = cc
 608
 609         return randID
 610 }
 611
 612 const dlFldrActionSendFile = 1
 613 const dlFldrActionResumeFile = 2
 614 const dlFldrActionNextFile = 3
 615
 616 func (s *Server) TransferFile(conn net.Conn) error {
 617         defer func() { _ = conn.Close() }()
 618
 619         txBuf := make([]byte, 16)
 620         _, err := conn.Read(txBuf)
 621         if err != nil {
 622                 return err
 623         }
 624
 625         var t transfer
 626         _, err = t.Write(txBuf)
 627         if err != nil {
 628                 return err
 629         }
 630
 631         transferRefNum := binary.BigEndian.Uint32(t.ReferenceNumber[:])
 632         fileTransfer := s.FileTransfers[transferRefNum]
 633
 634         switch fileTransfer.Type {
 635         case FileDownload:
 636                 fullFilePath, err := readPath(s.Config.FileRoot, fileTransfer.FilePath, fileTransfer.FileName)
 637                 if err != nil {
 638                         return err
 639                 }
 640
 641                 ffo, err := NewFlattenedFileObject(
 642                         s.Config.FileRoot,
 643                         fileTransfer.FilePath,
 644                         fileTransfer.FileName,
 645                 )
 646                 if err != nil {
 647                         return err
 648                 }
 649
 650                 s.Logger.Infow("File download started", "filePath", fullFilePath, "transactionRef", fileTransfer.ReferenceNumber, "RemoteAddr", conn.RemoteAddr().String())
 651
 652                 // Start by sending flat file object to client
 653                 if _, err := conn.Write(ffo.BinaryMarshal()); err != nil {
 654                         return err
 655                 }
 656
 657                 file, err := FS.Open(fullFilePath)
 658                 if err != nil {
 659                         return err
 660                 }
 661
 662                 sendBuffer := make([]byte, 1048576)
 663                 for {
 664                         var bytesRead int
 665                         if bytesRead, err = file.Read(sendBuffer); err == io.EOF {
 666                                 break
 667                         }
 668
 669                         fileTransfer.BytesSent += bytesRead
 670
 671                         delete(s.FileTransfers, transferRefNum)
 672
 673                         if _, err := conn.Write(sendBuffer[:bytesRead]); err != nil {
 674                                 return err
 675                         }
 676                 }
 677         case FileUpload:
 678                 const buffSize = 1460
 679
 680                 uploadBuf := make([]byte, buffSize)
 681
 682                 _, err := conn.Read(uploadBuf)
 683                 if err != nil {
 684                         return err
 685                 }
 686
 687                 ffo := ReadFlattenedFileObject(uploadBuf)
 688                 payloadLen := len(ffo.BinaryMarshal())
 689                 fileSize := int(binary.BigEndian.Uint32(ffo.FlatFileDataForkHeader.DataSize))
 690
 691                 destinationFile := s.Config.FileRoot + ReadFilePath(fileTransfer.FilePath) + "/" + string(fileTransfer.FileName)
 692                 s.Logger.Infow(
 693                         "File upload started",
 694                         "transactionRef", fileTransfer.ReferenceNumber,
 695                         "RemoteAddr", conn.RemoteAddr().String(),
 696                         "size", fileSize,
 697                         "dstFile", destinationFile,
 698                 )
 699
 700                 newFile, err := os.Create(destinationFile)
 701                 if err != nil {
 702                         return err
 703                 }
 704
 705                 defer func() { _ = newFile.Close() }()
 706
 707                 if _, err := newFile.Write(uploadBuf[payloadLen:]); err != nil {
 708                         return err
 709                 }
 710                 receivedBytes := buffSize - payloadLen
 711
 712                 for {
 713                         if (fileSize - receivedBytes) < buffSize {
 714                                 s.Logger.Infow(
 715                                         "File upload complete",
 716                                         "transactionRef", fileTransfer.ReferenceNumber,
 717                                         "RemoteAddr", conn.RemoteAddr().String(),
 718                                         "size", fileSize,
 719                                         "dstFile", destinationFile,
 720                                 )
 721
 722                                 if _, err := io.CopyN(newFile, conn, int64(fileSize-receivedBytes)); err != nil {
 723                                         return fmt.Errorf("file transfer failed: %s", err)
 724                                 }
 725                                 return nil
 726                         }
 727
 728                         // Copy N bytes from conn to upload file
 729                         n, err := io.CopyN(newFile, conn, buffSize)
 730                         if err != nil {
 731                                 return err
 732                         }
 733                         receivedBytes += int(n)
 734                 }
 735         case FolderDownload:
 736                 // Folder Download flow:
 737                 // 1. Get filePath from the transfer
 738                 // 2. Iterate over files
 739                 // 3. For each file:
 740                 //       Send file header to client
 741                 // The client can reply in 3 ways:
 742                 //
 743                 // 1. If type is an odd number (unknown type?), or file download for the current file is completed:
 744                 //              client sends []byte{0x00, 0x03} to tell the server to continue to the next file
 745                 //
 746                 // 2. If download of a file is to be resumed:
 747                 //              client sends:
 748                 //                      []byte{0x00, 0x02} // download folder action
 749                 //                      [2]byte // Resume data size
 750                 //                      []byte file resume data (see myField_FileResumeData)
 751                 //
 752                 // 3. Otherwise download of the file is requested and client sends []byte{0x00, 0x01}
 753                 //
 754                 // When download is requested (case 2 or 3), server replies with:
 755                 //                      [4]byte - file size
 756                 //                      []byte  - Flattened File Object
 757                 //
 758                 // After every file download, client could request next file with:
 759                 //                      []byte{0x00, 0x03}
 760                 //
 761                 // This notifies the server to send the next item header
 762
 763                 fullFilePath, err := readPath(s.Config.FileRoot, fileTransfer.FilePath, fileTransfer.FileName)
 764                 if err != nil {
 765                         return err
 766                 }
 767
 768                 basePathLen := len(fullFilePath)
 769
 770                 readBuffer := make([]byte, 1024)
 771
 772                 s.Logger.Infow("Start folder download", "path", fullFilePath, "ReferenceNumber", fileTransfer.ReferenceNumber, "RemoteAddr", conn.RemoteAddr())
 773
 774                 i := 0
 775                 _ = filepath.Walk(fullFilePath+"/", func(path string, info os.FileInfo, _ error) error {
 776                         i += 1
 777                         subPath := path[basePathLen:]
 778                         s.Logger.Infow("Sending fileheader", "i", i, "path", path, "fullFilePath", fullFilePath, "subPath", subPath, "IsDir", info.IsDir())
 779
 780                         fileHeader := NewFileHeader(subPath, info.IsDir())
 781
 782                         if i == 1 {
 783                                 return nil
 784                         }
 785
 786                         // Send the file header to client
 787                         if _, err := conn.Write(fileHeader.Payload()); err != nil {
 788                                 s.Logger.Errorf("error sending file header: %v", err)
 789                                 return err
 790                         }
 791
 792                         // Read the client's Next Action request
 793                         // TODO: Remove hardcoded behavior and switch behaviors based on the next action send
 794                         if _, err := conn.Read(readBuffer); err != nil {
 795                                 return err
 796                         }
 797
 798                         s.Logger.Infow("Client folder download action", "action", fmt.Sprintf("%X", readBuffer[0:2]))
 799
 800                         if info.IsDir() {
 801                                 return nil
 802                         }
 803
 804                         splitPath := strings.Split(path, "/")
 805
 806                         ffo, err := NewFlattenedFileObject(
 807                                 strings.Join(splitPath[:len(splitPath)-1], "/"),
 808                                 nil,
 809                                 []byte(info.Name()),
 810                         )
 811                         if err != nil {
 812                                 return err
 813                         }
 814                         s.Logger.Infow("File download started",
 815                                 "fileName", info.Name(),
 816                                 "transactionRef", fileTransfer.ReferenceNumber,
 817                                 "RemoteAddr", conn.RemoteAddr().String(),
 818                                 "TransferSize", fmt.Sprintf("%x", ffo.TransferSize()),
 819                         )
 820
 821                         // Send file size to client
 822                         if _, err := conn.Write(ffo.TransferSize()); err != nil {
 823                                 s.Logger.Error(err)
 824                                 return err
 825                         }
 826
 827                         // Send file bytes to client
 828                         if _, err := conn.Write(ffo.BinaryMarshal()); err != nil {
 829                                 s.Logger.Error(err)
 830                                 return err
 831                         }
 832
 833                         file, err := FS.Open(path)
 834                         if err != nil {
 835                                 return err
 836                         }
 837
 838                         sendBuffer := make([]byte, 1048576)
 839                         totalBytesSent := len(ffo.BinaryMarshal())
 840
 841                         for {
 842                                 bytesRead, err := file.Read(sendBuffer)
 843                                 if err == io.EOF {
 844                                         // Read the client's Next Action request
 845                                         // TODO: Remove hardcoded behavior and switch behaviors based on the next action send
 846                                         if _, err := conn.Read(readBuffer); err != nil {
 847                                                 s.Logger.Errorf("error reading next action: %v", err)
 848                                                 return err
 849                                         }
 850                                         break
 851                                 }
 852
 853                                 sentBytes, readErr := conn.Write(sendBuffer[:bytesRead])
 854                                 totalBytesSent += sentBytes
 855                                 if readErr != nil {
 856                                         return err
 857                                 }
 858                         }
 859                         return nil
 860                 })
 861
 862         case FolderUpload:
 863                 dstPath, err := readPath(s.Config.FileRoot, fileTransfer.FilePath, fileTransfer.FileName)
 864                 if err != nil {
 865                         return err
 866                 }
 867                 s.Logger.Infow(
 868                         "Folder upload started",
 869                         "transactionRef", fileTransfer.ReferenceNumber,
 870                         "RemoteAddr", conn.RemoteAddr().String(),
 871                         "dstPath", dstPath,
 872                         "TransferSize", fmt.Sprintf("%x", fileTransfer.TransferSize),
 873                         "FolderItemCount", fileTransfer.FolderItemCount,
 874                 )
 875
 876                 // Check if the target folder exists.  If not, create it.
 877                 if _, err := FS.Stat(dstPath); os.IsNotExist(err) {
 878                         s.Logger.Infow("Creating target path", "dstPath", dstPath)
 879                         if err := FS.Mkdir(dstPath, 0777); err != nil {
 880                                 s.Logger.Error(err)
 881                         }
 882                 }
 883
 884                 readBuffer := make([]byte, 1024)
 885
 886                 // Begin the folder upload flow by sending the "next file action" to client
 887                 if _, err := conn.Write([]byte{0, dlFldrActionNextFile}); err != nil {
 888                         return err
 889                 }
 890
 891                 fileSize := make([]byte, 4)
 892                 itemCount := binary.BigEndian.Uint16(fileTransfer.FolderItemCount)
 893
 894                 for i := uint16(0); i < itemCount; i++ {
 895                         if _, err := conn.Read(readBuffer); err != nil {
 896                                 return err
 897                         }
 898                         fu := readFolderUpload(readBuffer)
 899
 900                         s.Logger.Infow(
 901                                 "Folder upload continued",
 902                                 "transactionRef", fmt.Sprintf("%x", fileTransfer.ReferenceNumber),
 903                                 "RemoteAddr", conn.RemoteAddr().String(),
 904                                 "FormattedPath", fu.FormattedPath(),
 905                                 "IsFolder", fmt.Sprintf("%x", fu.IsFolder),
 906                                 "PathItemCount", binary.BigEndian.Uint16(fu.PathItemCount[:]),
 907                         )
 908
 909                         if fu.IsFolder == [2]byte{0, 1} {
 910                                 if _, err := os.Stat(dstPath + "/" + fu.FormattedPath()); os.IsNotExist(err) {
 911                                         s.Logger.Infow("Target path does not exist; Creating...", "dstPath", dstPath)
 912                                         if err := os.Mkdir(dstPath+"/"+fu.FormattedPath(), 0777); err != nil {
 913                                                 s.Logger.Error(err)
 914                                         }
 915                                 }
 916
 917                                 // Tell client to send next file
 918                                 if _, err := conn.Write([]byte{0, dlFldrActionNextFile}); err != nil {
 919                                         s.Logger.Error(err)
 920                                         return err
 921                                 }
 922                         } else {
 923                                 // TODO: Check if we have the full file already.  If so, send dlFldrAction_NextFile to client to skip.
 924                                 // TODO: Check if we have a partial file already.  If so, send dlFldrAction_ResumeFile to client to resume upload.
 925                                 // Send dlFldrAction_SendFile to client to begin transfer
 926                                 if _, err := conn.Write([]byte{0, dlFldrActionSendFile}); err != nil {
 927                                         return err
 928                                 }
 929
 930                                 if _, err := conn.Read(fileSize); err != nil {
 931                                         fmt.Println("Error reading:", err.Error()) // TODO: handle
 932                                 }
 933
 934                                 s.Logger.Infow("Starting file transfer", "fileNum", i+1, "totalFiles", itemCount, "fileSize", fileSize)
 935
 936                                 if err := transferFile(conn, dstPath+"/"+fu.FormattedPath()); err != nil {
 937                                         s.Logger.Error(err)
 938                                 }
 939
 940                                 // Tell client to send next file
 941                                 if _, err := conn.Write([]byte{0, dlFldrActionNextFile}); err != nil {
 942                                         s.Logger.Error(err)
 943                                         return err
 944                                 }
 945
 946                                 // Client sends "MACR" after the file.  Read and discard.
 947                                 // TODO: This doesn't seem to be documented.  What is this?  Maybe resource fork?
 948                                 if _, err := conn.Read(readBuffer); err != nil {
 949                                         return err
 950                                 }
 951                         }
 952                 }
 953                 s.Logger.Infof("Folder upload complete")
 954         }
 955
 956         return nil
 957 }
 958
 959 func transferFile(conn net.Conn, dst string) error {
 960         const buffSize = 1024
 961         buf := make([]byte, buffSize)
 962
 963         // Read first chunk of bytes from conn; this will be the Flat File Object and initial chunk of file bytes
 964         if _, err := conn.Read(buf); err != nil {
 965                 return err
 966         }
 967         ffo := ReadFlattenedFileObject(buf)
 968         payloadLen := len(ffo.BinaryMarshal())
 969         fileSize := int(binary.BigEndian.Uint32(ffo.FlatFileDataForkHeader.DataSize))
 970
 971         newFile, err := os.Create(dst)
 972         if err != nil {
 973                 return err
 974         }
 975         defer func() { _ = newFile.Close() }()
 976         if _, err := newFile.Write(buf[payloadLen:]); err != nil {
 977                 return err
 978         }
 979         receivedBytes := buffSize - payloadLen
 980
 981         for {
 982                 if (fileSize - receivedBytes) < buffSize {
 983                         _, err := io.CopyN(newFile, conn, int64(fileSize-receivedBytes))
 984                         return err
 985                 }
 986
 987                 // Copy N bytes from conn to upload file
 988                 n, err := io.CopyN(newFile, conn, buffSize)
 989                 if err != nil {
 990                         return err
 991                 }
 992                 receivedBytes += int(n)
 993         }
 994 }
 995
 996 // sortedClients is a utility function that takes a map of *ClientConn and returns a sorted slice of the values.
 997 // The purpose of this is to ensure that the ordering of client connections is deterministic so that test assertions work.
 998 func sortedClients(unsortedClients map[uint16]*ClientConn) (clients []*ClientConn) {
 999         for _, c := range unsortedClients {
1000                 clients = append(clients, c)
1001         }
1002         sort.Sort(byClientID(clients))
1003         return clients
1004 }