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