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         "log"
  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         "golang.org/x/crypto/bcrypt"
  25         "gopkg.in/yaml.v2"
  26 )
  27
  28 const (
  29         userIdleSeconds        = 300 // time in seconds before an inactive user is marked idle
  30         idleCheckInterval      = 10  // time in seconds to check for idle users
  31         trackerUpdateFrequency = 300 // time in seconds between tracker re-registration
  32 )
  33
  34 type Server struct {
  35         Port          int
  36         Accounts      map[string]*Account
  37         Agreement     []byte
  38         Clients       map[uint16]*ClientConn
  39         FlatNews      []byte
  40         ThreadedNews  *ThreadedNews
  41         FileTransfers map[uint32]*FileTransfer
  42         Config        *Config
  43         ConfigDir     string
  44         Logger        *zap.SugaredLogger
  45         PrivateChats  map[uint32]*PrivateChat
  46         NextGuestID   *uint16
  47         TrackerPassID []byte
  48         Stats         *Stats
  49
  50         APIListener  net.Listener
  51         FileListener net.Listener
  52
  53         newsReader io.Reader
  54         newsWriter io.WriteCloser
  55
  56         outbox chan Transaction
  57
  58         mux         sync.Mutex
  59         flatNewsMux sync.Mutex
  60 }
  61
  62 type PrivateChat struct {
  63         Subject    string
  64         ClientConn map[uint16]*ClientConn
  65 }
  66
  67 func (s *Server) ListenAndServe(ctx context.Context, cancelRoot context.CancelFunc) error {
  68         s.Logger.Infow("Hotline server started", "version", VERSION)
  69         var wg sync.WaitGroup
  70
  71         wg.Add(1)
  72         go func() { s.Logger.Fatal(s.Serve(ctx, cancelRoot, s.APIListener)) }()
  73
  74         wg.Add(1)
  75         go func() { s.Logger.Fatal(s.ServeFileTransfers(s.FileListener)) }()
  76
  77         wg.Wait()
  78
  79         return nil
  80 }
  81
  82 func (s *Server) APIPort() int {
  83         return s.APIListener.Addr().(*net.TCPAddr).Port
  84 }
  85
  86 func (s *Server) ServeFileTransfers(ln net.Listener) error {
  87         s.Logger.Infow("Hotline file transfer server started", "Addr", fmt.Sprintf(":%v", s.Port+1))
  88
  89         for {
  90                 conn, err := ln.Accept()
  91                 if err != nil {
  92                         return err
  93                 }
  94
  95                 go func() {
  96                         if err := s.TransferFile(conn); err != nil {
  97                                 s.Logger.Errorw("file transfer error", "reason", err)
  98                         }
  99                 }()
 100         }
 101 }
 102
 103 func (s *Server) sendTransaction(t Transaction) error {
 104         requestNum := binary.BigEndian.Uint16(t.Type)
 105         clientID, err := byteToInt(*t.clientID)
 106         if err != nil {
 107                 return err
 108         }
 109
 110         s.mux.Lock()
 111         client := s.Clients[uint16(clientID)]
 112         s.mux.Unlock()
 113         if client == nil {
 114                 return fmt.Errorf("invalid client id %v", *t.clientID)
 115         }
 116         userName := string(client.UserName)
 117         login := client.Account.Login
 118
 119         handler := TransactionHandlers[requestNum]
 120
 121         b, err := t.MarshalBinary()
 122         if err != nil {
 123                 return err
 124         }
 125         var n int
 126         if n, err = client.Connection.Write(b); err != nil {
 127                 return err
 128         }
 129         s.Logger.Debugw("Sent Transaction",
 130                 "name", userName,
 131                 "login", login,
 132                 "IsReply", t.IsReply,
 133                 "type", handler.Name,
 134                 "sentBytes", n,
 135                 "remoteAddr", client.Connection.RemoteAddr(),
 136         )
 137         return nil
 138 }
 139
 140 func (s *Server) Serve(ctx context.Context, cancelRoot context.CancelFunc, ln net.Listener) error {
 141         s.Logger.Infow("Hotline server started", "Addr", fmt.Sprintf(":%v", s.Port))
 142
 143         for {
 144                 conn, err := ln.Accept()
 145                 if err != nil {
 146                         s.Logger.Errorw("error accepting connection", "err", err)
 147                 }
 148
 149                 go func() {
 150                         for {
 151                                 t := <-s.outbox
 152                                 go func() {
 153                                         if err := s.sendTransaction(t); err != nil {
 154                                                 s.Logger.Errorw("error sending transaction", "err", err)
 155                                         }
 156                                 }()
 157                         }
 158                 }()
 159                 go func() {
 160                         if err := s.handleNewConnection(conn); err != nil {
 161                                 if err == io.EOF {
 162                                         s.Logger.Infow("Client disconnected", "RemoteAddr", conn.RemoteAddr())
 163                                 } else {
 164                                         s.Logger.Errorw("error serving request", "RemoteAddr", conn.RemoteAddr(), "err", err)
 165                                 }
 166                         }
 167                 }()
 168         }
 169 }
 170
 171 const (
 172         agreementFile = "Agreement.txt"
 173 )
 174
 175 // NewServer constructs a new Server from a config dir
 176 func NewServer(configDir, netInterface string, netPort int, logger *zap.SugaredLogger) (*Server, error) {
 177         server := Server{
 178                 Port:          netPort,
 179                 Accounts:      make(map[string]*Account),
 180                 Config:        new(Config),
 181                 Clients:       make(map[uint16]*ClientConn),
 182                 FileTransfers: make(map[uint32]*FileTransfer),
 183                 PrivateChats:  make(map[uint32]*PrivateChat),
 184                 ConfigDir:     configDir,
 185                 Logger:        logger,
 186                 NextGuestID:   new(uint16),
 187                 outbox:        make(chan Transaction),
 188                 Stats:         &Stats{StartTime: time.Now()},
 189                 ThreadedNews:  &ThreadedNews{},
 190                 TrackerPassID: make([]byte, 4),
 191         }
 192
 193         ln, err := net.Listen("tcp", fmt.Sprintf("%s:%v", netInterface, netPort))
 194         if err != nil {
 195                 return nil, err
 196         }
 197         server.APIListener = ln
 198
 199         if netPort != 0 {
 200                 netPort += 1
 201         }
 202
 203         ln2, err := net.Listen("tcp", fmt.Sprintf("%s:%v", netInterface, netPort))
 204         server.FileListener = ln2
 205         if err != nil {
 206                 return nil, err
 207         }
 208
 209         // generate a new random passID for tracker registration
 210         if _, err := rand.Read(server.TrackerPassID); err != nil {
 211                 return nil, err
 212         }
 213
 214         server.Logger.Debugw("Loading Agreement", "path", configDir+agreementFile)
 215         if server.Agreement, err = os.ReadFile(configDir + agreementFile); err != nil {
 216                 return nil, err
 217         }
 218
 219         if server.FlatNews, err = os.ReadFile(configDir + "MessageBoard.txt"); err != nil {
 220                 return nil, err
 221         }
 222
 223         if err := server.loadThreadedNews(configDir + "ThreadedNews.yaml"); err != nil {
 224                 return nil, err
 225         }
 226
 227         if err := server.loadConfig(configDir + "config.yaml"); err != nil {
 228                 return nil, err
 229         }
 230
 231         if err := server.loadAccounts(configDir + "Users/"); err != nil {
 232                 return nil, err
 233         }
 234
 235         server.Config.FileRoot = configDir + "Files/"
 236
 237         *server.NextGuestID = 1
 238
 239         if server.Config.EnableTrackerRegistration {
 240                 go func() {
 241                         for {
 242                                 tr := TrackerRegistration{
 243                                         Port:        []byte{0x15, 0x7c},
 244                                         UserCount:   server.userCount(),
 245                                         PassID:      server.TrackerPassID,
 246                                         Name:        server.Config.Name,
 247                                         Description: server.Config.Description,
 248                                 }
 249                                 for _, t := range server.Config.Trackers {
 250                                         server.Logger.Infof("Registering with tracker %v", t)
 251
 252                                         if err := register(t, tr); err != nil {
 253                                                 server.Logger.Errorw("unable to register with tracker %v", "error", err)
 254                                         }
 255                                 }
 256
 257                                 time.Sleep(trackerUpdateFrequency * time.Second)
 258                         }
 259                 }()
 260         }
 261
 262         // Start Client Keepalive go routine
 263         go server.keepaliveHandler()
 264
 265         return &server, nil
 266 }
 267
 268 func (s *Server) userCount() int {
 269         s.mux.Lock()
 270         defer s.mux.Unlock()
 271
 272         return len(s.Clients)
 273 }
 274
 275 func (s *Server) keepaliveHandler() {
 276         for {
 277                 time.Sleep(idleCheckInterval * time.Second)
 278                 s.mux.Lock()
 279
 280                 for _, c := range s.Clients {
 281                         *c.IdleTime += idleCheckInterval
 282                         if *c.IdleTime > userIdleSeconds && !c.Idle {
 283                                 c.Idle = true
 284
 285                                 flagBitmap := big.NewInt(int64(binary.BigEndian.Uint16(*c.Flags)))
 286                                 flagBitmap.SetBit(flagBitmap, userFlagAway, 1)
 287                                 binary.BigEndian.PutUint16(*c.Flags, uint16(flagBitmap.Int64()))
 288
 289                                 c.sendAll(
 290                                         tranNotifyChangeUser,
 291                                         NewField(fieldUserID, *c.ID),
 292                                         NewField(fieldUserFlags, *c.Flags),
 293                                         NewField(fieldUserName, c.UserName),
 294                                         NewField(fieldUserIconID, *c.Icon),
 295                                 )
 296                         }
 297                 }
 298                 s.mux.Unlock()
 299         }
 300 }
 301
 302 func (s *Server) writeThreadedNews() error {
 303         s.mux.Lock()
 304         defer s.mux.Unlock()
 305
 306         out, err := yaml.Marshal(s.ThreadedNews)
 307         if err != nil {
 308                 return err
 309         }
 310         err = ioutil.WriteFile(
 311                 s.ConfigDir+"ThreadedNews.yaml",
 312                 out,
 313                 0666,
 314         )
 315         return err
 316 }
 317
 318 func (s *Server) NewClientConn(conn net.Conn) *ClientConn {
 319         s.mux.Lock()
 320         defer s.mux.Unlock()
 321
 322         clientConn := &ClientConn{
 323                 ID:         &[]byte{0, 0},
 324                 Icon:       &[]byte{0, 0},
 325                 Flags:      &[]byte{0, 0},
 326                 UserName:   []byte{},
 327                 Connection: conn,
 328                 Server:     s,
 329                 Version:    &[]byte{},
 330                 IdleTime:   new(int),
 331                 AutoReply:  &[]byte{},
 332                 Transfers:  make(map[int][]*FileTransfer),
 333                 Agreed:     false,
 334         }
 335         *s.NextGuestID++
 336         ID := *s.NextGuestID
 337
 338         *clientConn.IdleTime = 0
 339
 340         binary.BigEndian.PutUint16(*clientConn.ID, ID)
 341         s.Clients[ID] = clientConn
 342
 343         return clientConn
 344 }
 345
 346 // NewUser creates a new user account entry in the server map and config file
 347 func (s *Server) NewUser(login, name, password string, access []byte) error {
 348         s.mux.Lock()
 349         defer s.mux.Unlock()
 350
 351         account := Account{
 352                 Login:    login,
 353                 Name:     name,
 354                 Password: hashAndSalt([]byte(password)),
 355                 Access:   &access,
 356         }
 357         out, err := yaml.Marshal(&account)
 358         if err != nil {
 359                 return err
 360         }
 361         s.Accounts[login] = &account
 362
 363         return ioutil.WriteFile(s.ConfigDir+"Users/"+login+".yaml", out, 0666)
 364 }
 365
 366 // DeleteUser deletes the user account
 367 func (s *Server) DeleteUser(login string) error {
 368         s.mux.Lock()
 369         defer s.mux.Unlock()
 370
 371         delete(s.Accounts, login)
 372
 373         return os.Remove(s.ConfigDir + "Users/" + login + ".yaml")
 374 }
 375
 376 func (s *Server) connectedUsers() []Field {
 377         s.mux.Lock()
 378         defer s.mux.Unlock()
 379
 380         var connectedUsers []Field
 381         for _, c := range sortedClients(s.Clients) {
 382                 if c.Agreed == false {
 383                         continue
 384                 }
 385                 user := User{
 386                         ID:    *c.ID,
 387                         Icon:  *c.Icon,
 388                         Flags: *c.Flags,
 389                         Name:  string(c.UserName),
 390                 }
 391                 connectedUsers = append(connectedUsers, NewField(fieldUsernameWithInfo, user.Payload()))
 392         }
 393         return connectedUsers
 394 }
 395
 396 // loadThreadedNews loads the threaded news data from disk
 397 func (s *Server) loadThreadedNews(threadedNewsPath string) error {
 398         fh, err := os.Open(threadedNewsPath)
 399         if err != nil {
 400                 return err
 401         }
 402         decoder := yaml.NewDecoder(fh)
 403         decoder.SetStrict(true)
 404
 405         return decoder.Decode(s.ThreadedNews)
 406 }
 407
 408 // loadAccounts loads account data from disk
 409 func (s *Server) loadAccounts(userDir string) error {
 410         matches, err := filepath.Glob(path.Join(userDir, "*.yaml"))
 411         if err != nil {
 412                 return err
 413         }
 414
 415         if len(matches) == 0 {
 416                 return errors.New("no user accounts found in " + userDir)
 417         }
 418
 419         for _, file := range matches {
 420                 fh, err := FS.Open(file)
 421                 if err != nil {
 422                         return err
 423                 }
 424
 425                 account := Account{}
 426                 decoder := yaml.NewDecoder(fh)
 427                 decoder.SetStrict(true)
 428                 if err := decoder.Decode(&account); err != nil {
 429                         return err
 430                 }
 431
 432                 s.Accounts[account.Login] = &account
 433         }
 434         return nil
 435 }
 436
 437 func (s *Server) loadConfig(path string) error {
 438         fh, err := FS.Open(path)
 439         if err != nil {
 440                 return err
 441         }
 442
 443         decoder := yaml.NewDecoder(fh)
 444         decoder.SetStrict(true)
 445         err = decoder.Decode(s.Config)
 446         if err != nil {
 447                 return err
 448         }
 449         return nil
 450 }
 451
 452 const (
 453         minTransactionLen = 22 // minimum length of any transaction
 454 )
 455
 456 // handleNewConnection takes a new net.Conn and performs the initial login sequence
 457 func (s *Server) handleNewConnection(conn net.Conn) error {
 458         handshakeBuf := make([]byte, 12) // handshakes are always 12 bytes in length
 459         if _, err := conn.Read(handshakeBuf); err != nil {
 460                 return err
 461         }
 462         if err := Handshake(conn, handshakeBuf[:12]); err != nil {
 463                 return err
 464         }
 465
 466         buf := make([]byte, 1024)
 467         readLen, err := conn.Read(buf)
 468         if readLen < minTransactionLen {
 469                 return err
 470         }
 471         if err != nil {
 472                 return err
 473         }
 474
 475         clientLogin, _, err := ReadTransaction(buf[:readLen])
 476         if err != nil {
 477                 return err
 478         }
 479
 480         c := s.NewClientConn(conn)
 481         defer c.Disconnect()
 482         defer func() {
 483                 if r := recover(); r != nil {
 484                         fmt.Println("stacktrace from panic: \n" + string(debug.Stack()))
 485                         c.Server.Logger.Errorw("PANIC", "err", r, "trace", string(debug.Stack()))
 486                         c.Disconnect()
 487                 }
 488         }()
 489
 490         encodedLogin := clientLogin.GetField(fieldUserLogin).Data
 491         encodedPassword := clientLogin.GetField(fieldUserPassword).Data
 492         *c.Version = clientLogin.GetField(fieldVersion).Data
 493
 494         var login string
 495         for _, char := range encodedLogin {
 496                 login += string(rune(255 - uint(char)))
 497         }
 498         if login == "" {
 499                 login = GuestAccount
 500         }
 501
 502         // If authentication fails, send error reply and close connection
 503         if !c.Authenticate(login, encodedPassword) {
 504                 t := c.NewErrReply(clientLogin, "Incorrect login.")
 505                 b, err := t.MarshalBinary()
 506                 if err != nil {
 507                         return err
 508                 }
 509                 if _, err := conn.Write(b); err != nil {
 510                         return err
 511                 }
 512                 return fmt.Errorf("incorrect login")
 513         }
 514
 515         if clientLogin.GetField(fieldUserName).Data != nil {
 516                 c.UserName = clientLogin.GetField(fieldUserName).Data
 517         }
 518
 519         if clientLogin.GetField(fieldUserIconID).Data != nil {
 520                 *c.Icon = clientLogin.GetField(fieldUserIconID).Data
 521         }
 522
 523         c.Account = c.Server.Accounts[login]
 524
 525         if c.Authorize(accessDisconUser) {
 526                 *c.Flags = []byte{0, 2}
 527         }
 528
 529         s.Logger.Infow("Client connection received", "login", login, "version", *c.Version, "RemoteAddr", conn.RemoteAddr().String())
 530
 531         s.outbox <- c.NewReply(clientLogin,
 532                 NewField(fieldVersion, []byte{0x00, 0xbe}),
 533                 NewField(fieldCommunityBannerID, []byte{0x00, 0x01}),
 534                 NewField(fieldServerName, []byte(s.Config.Name)),
 535         )
 536
 537         // Send user access privs so client UI knows how to behave
 538         c.Server.outbox <- *NewTransaction(tranUserAccess, c.ID, NewField(fieldUserAccess, *c.Account.Access))
 539
 540         // Show agreement to client
 541         c.Server.outbox <- *NewTransaction(tranShowAgreement, c.ID, NewField(fieldData, s.Agreement))
 542
 543         // assume simplified hotline v1.2.3 login flow that does not require agreement
 544         if *c.Version == nil {
 545                 c.Agreed = true
 546                 if _, err := c.notifyNewUserHasJoined(); err != nil {
 547                         return err
 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 func hashAndSalt(pwd []byte) string {
 584         // Use GenerateFromPassword to hash & salt pwd.
 585         // MinCost is just an integer constant provided by the bcrypt
 586         // package along with DefaultCost & MaxCost.
 587         // The cost can be any value you want provided it isn't lower
 588         // than the MinCost (4)
 589         hash, err := bcrypt.GenerateFromPassword(pwd, bcrypt.MinCost)
 590         if err != nil {
 591                 log.Println(err)
 592         }
 593         // GenerateFromPassword returns a byte slice so we need to
 594         // convert the bytes to a string and return it
 595         return string(hash)
 596 }
 597
 598 // NewTransactionRef generates a random ID for the file transfer.  The Hotline client includes this ID
 599 // in the file transfer request payload, and the file transfer server will use it to map the request
 600 // to a transfer
 601 func (s *Server) NewTransactionRef() []byte {
 602         transactionRef := make([]byte, 4)
 603         rand.Read(transactionRef)
 604
 605         return transactionRef
 606 }
 607
 608 func (s *Server) NewPrivateChat(cc *ClientConn) []byte {
 609         s.mux.Lock()
 610         defer s.mux.Unlock()
 611
 612         randID := make([]byte, 4)
 613         rand.Read(randID)
 614         data := binary.BigEndian.Uint32(randID[:])
 615
 616         s.PrivateChats[data] = &PrivateChat{
 617                 Subject:    "",
 618                 ClientConn: make(map[uint16]*ClientConn),
 619         }
 620         s.PrivateChats[data].ClientConn[cc.uint16ID()] = cc
 621
 622         return randID
 623 }
 624
 625 const dlFldrActionSendFile = 1
 626 const dlFldrActionResumeFile = 2
 627 const dlFldrActionNextFile = 3
 628
 629 func (s *Server) TransferFile(conn net.Conn) error {
 630         defer func() { _ = conn.Close() }()
 631
 632         buf := make([]byte, 1024)
 633         if _, err := conn.Read(buf); err != nil {
 634                 return err
 635         }
 636
 637         var t transfer
 638         _, err := t.Write(buf[:16])
 639         if err != nil {
 640                 return err
 641         }
 642
 643         transferRefNum := binary.BigEndian.Uint32(t.ReferenceNumber[:])
 644         fileTransfer := s.FileTransfers[transferRefNum]
 645
 646         switch fileTransfer.Type {
 647         case FileDownload:
 648                 fullFilePath, err := readPath(s.Config.FileRoot, fileTransfer.FilePath, fileTransfer.FileName)
 649                 if err != nil {
 650                         return err
 651                 }
 652
 653                 ffo, err := NewFlattenedFileObject(
 654                         s.Config.FileRoot,
 655                         fileTransfer.FilePath,
 656                         fileTransfer.FileName,
 657                 )
 658                 if err != nil {
 659                         return err
 660                 }
 661
 662                 s.Logger.Infow("File download started", "filePath", fullFilePath, "transactionRef", fileTransfer.ReferenceNumber, "RemoteAddr", conn.RemoteAddr().String())
 663
 664                 // Start by sending flat file object to client
 665                 if _, err := conn.Write(ffo.BinaryMarshal()); err != nil {
 666                         return err
 667                 }
 668
 669                 file, err := FS.Open(fullFilePath)
 670                 if err != nil {
 671                         return err
 672                 }
 673
 674                 sendBuffer := make([]byte, 1048576)
 675                 for {
 676                         var bytesRead int
 677                         if bytesRead, err = file.Read(sendBuffer); err == io.EOF {
 678                                 break
 679                         }
 680
 681                         fileTransfer.BytesSent += bytesRead
 682
 683                         delete(s.FileTransfers, transferRefNum)
 684
 685                         if _, err := conn.Write(sendBuffer[:bytesRead]); err != nil {
 686                                 return err
 687                         }
 688                 }
 689         case FileUpload:
 690                 if _, err := conn.Read(buf); err != nil {
 691                         return err
 692                 }
 693
 694                 ffo := ReadFlattenedFileObject(buf)
 695                 payloadLen := len(ffo.BinaryMarshal())
 696                 fileSize := int(binary.BigEndian.Uint32(ffo.FlatFileDataForkHeader.DataSize))
 697
 698                 destinationFile := s.Config.FileRoot + ReadFilePath(fileTransfer.FilePath) + "/" + string(fileTransfer.FileName)
 699                 s.Logger.Infow(
 700                         "File upload started",
 701                         "transactionRef", fileTransfer.ReferenceNumber,
 702                         "RemoteAddr", conn.RemoteAddr().String(),
 703                         "size", fileSize,
 704                         "dstFile", destinationFile,
 705                 )
 706
 707                 newFile, err := os.Create(destinationFile)
 708                 if err != nil {
 709                         return err
 710                 }
 711
 712                 defer func() { _ = newFile.Close() }()
 713
 714                 const buffSize = 1024
 715
 716                 if _, err := newFile.Write(buf[payloadLen:]); err != nil {
 717                         return err
 718                 }
 719                 receivedBytes := buffSize - payloadLen
 720
 721                 for {
 722                         if (fileSize - receivedBytes) < buffSize {
 723                                 s.Logger.Infow(
 724                                         "File upload complete",
 725                                         "transactionRef", fileTransfer.ReferenceNumber,
 726                                         "RemoteAddr", conn.RemoteAddr().String(),
 727                                         "size", fileSize,
 728                                         "dstFile", destinationFile,
 729                                 )
 730
 731                                 if _, err := io.CopyN(newFile, conn, int64(fileSize-receivedBytes)); err != nil {
 732                                         return fmt.Errorf("file transfer failed: %s", err)
 733                                 }
 734                                 return nil
 735                         }
 736
 737                         // Copy N bytes from conn to upload file
 738                         n, err := io.CopyN(newFile, conn, buffSize)
 739                         if err != nil {
 740                                 return err
 741                         }
 742                         receivedBytes += int(n)
 743                 }
 744         case FolderDownload:
 745                 // Folder Download flow:
 746                 // 1. Get filePath from the transfer
 747                 // 2. Iterate over files
 748                 // 3. For each file:
 749                 //       Send file header to client
 750                 // The client can reply in 3 ways:
 751                 //
 752                 // 1. If type is an odd number (unknown type?), or file download for the current file is completed:
 753                 //              client sends []byte{0x00, 0x03} to tell the server to continue to the next file
 754                 //
 755                 // 2. If download of a file is to be resumed:
 756                 //              client sends:
 757                 //                      []byte{0x00, 0x02} // download folder action
 758                 //                      [2]byte // Resume data size
 759                 //                      []byte file resume data (see myField_FileResumeData)
 760                 //
 761                 // 3. Otherwise download of the file is requested and client sends []byte{0x00, 0x01}
 762                 //
 763                 // When download is requested (case 2 or 3), server replies with:
 764                 //                      [4]byte - file size
 765                 //                      []byte  - Flattened File Object
 766                 //
 767                 // After every file download, client could request next file with:
 768                 //                      []byte{0x00, 0x03}
 769                 //
 770                 // This notifies the server to send the next item header
 771
 772                 fullFilePath, err := readPath(s.Config.FileRoot, fileTransfer.FilePath, fileTransfer.FileName)
 773                 if err != nil {
 774                         return err
 775                 }
 776
 777                 basePathLen := len(fullFilePath)
 778
 779                 readBuffer := make([]byte, 1024)
 780
 781                 s.Logger.Infow("Start folder download", "path", fullFilePath, "ReferenceNumber", fileTransfer.ReferenceNumber, "RemoteAddr", conn.RemoteAddr())
 782
 783                 i := 0
 784                 _ = filepath.Walk(fullFilePath+"/", func(path string, info os.FileInfo, _ error) error {
 785                         i += 1
 786                         subPath := path[basePathLen:]
 787                         s.Logger.Infow("Sending fileheader", "i", i, "path", path, "fullFilePath", fullFilePath, "subPath", subPath, "IsDir", info.IsDir())
 788
 789                         fileHeader := NewFileHeader(subPath, info.IsDir())
 790
 791                         if i == 1 {
 792                                 return nil
 793                         }
 794
 795                         // Send the file header to client
 796                         if _, err := conn.Write(fileHeader.Payload()); err != nil {
 797                                 s.Logger.Errorf("error sending file header: %v", err)
 798                                 return err
 799                         }
 800
 801                         // Read the client's Next Action request
 802                         //TODO: Remove hardcoded behavior and switch behaviors based on the next action send
 803                         if _, err := conn.Read(readBuffer); err != nil {
 804                                 return err
 805                         }
 806
 807                         s.Logger.Infow("Client folder download action", "action", fmt.Sprintf("%X", readBuffer[0:2]))
 808
 809                         if info.IsDir() {
 810                                 return nil
 811                         }
 812
 813                         splitPath := strings.Split(path, "/")
 814
 815                         ffo, err := NewFlattenedFileObject(
 816                                 strings.Join(splitPath[:len(splitPath)-1], "/"),
 817                                 nil,
 818                                 []byte(info.Name()),
 819                         )
 820                         if err != nil {
 821                                 return err
 822                         }
 823                         s.Logger.Infow("File download started",
 824                                 "fileName", info.Name(),
 825                                 "transactionRef", fileTransfer.ReferenceNumber,
 826                                 "RemoteAddr", conn.RemoteAddr().String(),
 827                                 "TransferSize", fmt.Sprintf("%x", ffo.TransferSize()),
 828                         )
 829
 830                         // Send file size to client
 831                         if _, err := conn.Write(ffo.TransferSize()); err != nil {
 832                                 s.Logger.Error(err)
 833                                 return err
 834                         }
 835
 836                         // Send file bytes to client
 837                         if _, err := conn.Write(ffo.BinaryMarshal()); err != nil {
 838                                 s.Logger.Error(err)
 839                                 return err
 840                         }
 841
 842                         file, err := FS.Open(path)
 843                         if err != nil {
 844                                 return err
 845                         }
 846
 847                         sendBuffer := make([]byte, 1048576)
 848                         totalBytesSent := len(ffo.BinaryMarshal())
 849
 850                         for {
 851                                 bytesRead, err := file.Read(sendBuffer)
 852                                 if err == io.EOF {
 853                                         // Read the client's Next Action request
 854                                         //TODO: Remove hardcoded behavior and switch behaviors based on the next action send
 855                                         if _, err := conn.Read(readBuffer); err != nil {
 856                                                 s.Logger.Errorf("error reading next action: %v", err)
 857                                                 return err
 858                                         }
 859                                         break
 860                                 }
 861
 862                                 sentBytes, readErr := conn.Write(sendBuffer[:bytesRead])
 863                                 totalBytesSent += sentBytes
 864                                 if readErr != nil {
 865                                         return err
 866                                 }
 867                         }
 868                         return nil
 869                 })
 870
 871         case FolderUpload:
 872                 dstPath, err := readPath(s.Config.FileRoot, fileTransfer.FilePath, fileTransfer.FileName)
 873                 if err != nil {
 874                         return err
 875                 }
 876                 s.Logger.Infow(
 877                         "Folder upload started",
 878                         "transactionRef", fileTransfer.ReferenceNumber,
 879                         "RemoteAddr", conn.RemoteAddr().String(),
 880                         "dstPath", dstPath,
 881                         "TransferSize", fmt.Sprintf("%x", fileTransfer.TransferSize),
 882                         "FolderItemCount", fileTransfer.FolderItemCount,
 883                 )
 884
 885                 // Check if the target folder exists.  If not, create it.
 886                 if _, err := FS.Stat(dstPath); os.IsNotExist(err) {
 887                         s.Logger.Infow("Creating target path", "dstPath", dstPath)
 888                         if err := FS.Mkdir(dstPath, 0777); err != nil {
 889                                 s.Logger.Error(err)
 890                         }
 891                 }
 892
 893                 readBuffer := make([]byte, 1024)
 894
 895                 // Begin the folder upload flow by sending the "next file action" to client
 896                 if _, err := conn.Write([]byte{0, dlFldrActionNextFile}); err != nil {
 897                         return err
 898                 }
 899
 900                 fileSize := make([]byte, 4)
 901                 itemCount := binary.BigEndian.Uint16(fileTransfer.FolderItemCount)
 902
 903                 for i := uint16(0); i < itemCount; i++ {
 904                         if _, err := conn.Read(readBuffer); err != nil {
 905                                 return err
 906                         }
 907                         fu := readFolderUpload(readBuffer)
 908
 909                         s.Logger.Infow(
 910                                 "Folder upload continued",
 911                                 "transactionRef", fmt.Sprintf("%x", fileTransfer.ReferenceNumber),
 912                                 "RemoteAddr", conn.RemoteAddr().String(),
 913                                 "FormattedPath", fu.FormattedPath(),
 914                                 "IsFolder", fmt.Sprintf("%x", fu.IsFolder),
 915                                 "PathItemCount", binary.BigEndian.Uint16(fu.PathItemCount[:]),
 916                         )
 917
 918                         if fu.IsFolder == [2]byte{0, 1} {
 919                                 if _, err := os.Stat(dstPath + "/" + fu.FormattedPath()); os.IsNotExist(err) {
 920                                         s.Logger.Infow("Target path does not exist; Creating...", "dstPath", dstPath)
 921                                         if err := os.Mkdir(dstPath+"/"+fu.FormattedPath(), 0777); err != nil {
 922                                                 s.Logger.Error(err)
 923                                         }
 924                                 }
 925
 926                                 // Tell client to send next file
 927                                 if _, err := conn.Write([]byte{0, dlFldrActionNextFile}); err != nil {
 928                                         s.Logger.Error(err)
 929                                         return err
 930                                 }
 931                         } else {
 932                                 // TODO: Check if we have the full file already.  If so, send dlFldrAction_NextFile to client to skip.
 933                                 // TODO: Check if we have a partial file already.  If so, send dlFldrAction_ResumeFile to client to resume upload.
 934                                 // Send dlFldrAction_SendFile to client to begin transfer
 935                                 if _, err := conn.Write([]byte{0, dlFldrActionSendFile}); err != nil {
 936                                         return err
 937                                 }
 938
 939                                 if _, err := conn.Read(fileSize); err != nil {
 940                                         fmt.Println("Error reading:", err.Error()) // TODO: handle
 941                                 }
 942
 943                                 s.Logger.Infow("Starting file transfer", "fileNum", i+1, "totalFiles", itemCount, "fileSize", fileSize)
 944
 945                                 if err := transferFile(conn, dstPath+"/"+fu.FormattedPath()); err != nil {
 946                                         s.Logger.Error(err)
 947                                 }
 948
 949                                 // Tell client to send next file
 950                                 if _, err := conn.Write([]byte{0, dlFldrActionNextFile}); err != nil {
 951                                         s.Logger.Error(err)
 952                                         return err
 953                                 }
 954
 955                                 // Client sends "MACR" after the file.  Read and discard.
 956                                 // TODO: This doesn't seem to be documented.  What is this?  Maybe resource fork?
 957                                 if _, err := conn.Read(readBuffer); err != nil {
 958                                         return err
 959                                 }
 960                         }
 961                 }
 962                 s.Logger.Infof("Folder upload complete")
 963         }
 964
 965         return nil
 966 }
 967
 968 func transferFile(conn net.Conn, dst string) error {
 969         const buffSize = 1024
 970         buf := make([]byte, buffSize)
 971
 972         // Read first chunk of bytes from conn; this will be the Flat File Object and initial chunk of file bytes
 973         if _, err := conn.Read(buf); err != nil {
 974                 return err
 975         }
 976         ffo := ReadFlattenedFileObject(buf)
 977         payloadLen := len(ffo.BinaryMarshal())
 978         fileSize := int(binary.BigEndian.Uint32(ffo.FlatFileDataForkHeader.DataSize))
 979
 980         newFile, err := os.Create(dst)
 981         if err != nil {
 982                 return err
 983         }
 984         defer func() { _ = newFile.Close() }()
 985         if _, err := newFile.Write(buf[payloadLen:]); err != nil {
 986                 return err
 987         }
 988         receivedBytes := buffSize - payloadLen
 989
 990         for {
 991                 if (fileSize - receivedBytes) < buffSize {
 992                         _, err := io.CopyN(newFile, conn, int64(fileSize-receivedBytes))
 993                         return err
 994                 }
 995
 996                 // Copy N bytes from conn to upload file
 997                 n, err := io.CopyN(newFile, conn, buffSize)
 998                 if err != nil {
 999                         return err
1000                 }
1001                 receivedBytes += int(n)
1002         }
1003 }
1004
1005 // sortedClients is a utility function that takes a map of *ClientConn and returns a sorted slice of the values.
1006 // The purpose of this is to ensure that the ordering of client connections is deterministic so that test assertions work.
1007 func sortedClients(unsortedClients map[uint16]*ClientConn) (clients []*ClientConn) {
1008         for _, c := range unsortedClients {
1009                 clients = append(clients, c)
1010         }
1011         sort.Sort(byClientID(clients))
1012         return clients
1013 }