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

   1 package hotline
   2
   3 import (
   4         "context"
   5         "encoding/binary"
   6         "errors"
   7         "fmt"
   8         "go.uber.org/zap"
   9         "io"
  10         "io/fs"
  11         "io/ioutil"
  12         "math/big"
  13         "math/rand"
  14         "net"
  15         "os"
  16         "path"
  17         "path/filepath"
  18         "runtime/debug"
  19         "sort"
  20         "strings"
  21         "sync"
  22         "time"
  23
  24         "gopkg.in/yaml.v3"
  25 )
  26
  27 const (
  28         userIdleSeconds        = 300 // time in seconds before an inactive user is marked idle
  29         idleCheckInterval      = 10  // time in seconds to check for idle users
  30         trackerUpdateFrequency = 300 // time in seconds between tracker re-registration
  31 )
  32
  33 type Server struct {
  34         Port          int
  35         Accounts      map[string]*Account
  36         Agreement     []byte
  37         Clients       map[uint16]*ClientConn
  38         FlatNews      []byte
  39         ThreadedNews  *ThreadedNews
  40         FileTransfers map[uint32]*FileTransfer
  41         Config        *Config
  42         ConfigDir     string
  43         Logger        *zap.SugaredLogger
  44         PrivateChats  map[uint32]*PrivateChat
  45         NextGuestID   *uint16
  46         TrackerPassID []byte
  47         Stats         *Stats
  48
  49         APIListener  net.Listener
  50         FileListener net.Listener
  51
  52         // newsReader io.Reader
  53         // newsWriter io.WriteCloser
  54
  55         outbox chan Transaction
  56
  57         mux         sync.Mutex
  58         flatNewsMux sync.Mutex
  59 }
  60
  61 type PrivateChat struct {
  62         Subject    string
  63         ClientConn map[uint16]*ClientConn
  64 }
  65
  66 func (s *Server) ListenAndServe(ctx context.Context, cancelRoot context.CancelFunc) error {
  67         s.Logger.Infow("Hotline server started", "version", VERSION)
  68         var wg sync.WaitGroup
  69
  70         wg.Add(1)
  71         go func() { s.Logger.Fatal(s.Serve(ctx, cancelRoot, s.APIListener)) }()
  72
  73         wg.Add(1)
  74         go func() { s.Logger.Fatal(s.ServeFileTransfers(s.FileListener)) }()
  75
  76         wg.Wait()
  77
  78         return nil
  79 }
  80
  81 func (s *Server) APIPort() int {
  82         return s.APIListener.Addr().(*net.TCPAddr).Port
  83 }
  84
  85 func (s *Server) ServeFileTransfers(ln net.Listener) error {
  86         s.Logger.Infow("Hotline file transfer server started", "Addr", fmt.Sprintf(":%v", s.Port+1))
  87
  88         for {
  89                 conn, err := ln.Accept()
  90                 if err != nil {
  91                         return err
  92                 }
  93
  94                 go func() {
  95                         if err := s.handleFileTransfer(conn); err != nil {
  96                                 s.Logger.Errorw("file transfer error", "reason", err)
  97                         }
  98                 }()
  99         }
 100 }
 101
 102 func (s *Server) sendTransaction(t Transaction) error {
 103         requestNum := binary.BigEndian.Uint16(t.Type)
 104         clientID, err := byteToInt(*t.clientID)
 105         if err != nil {
 106                 return err
 107         }
 108
 109         s.mux.Lock()
 110         client := s.Clients[uint16(clientID)]
 111         s.mux.Unlock()
 112         if client == nil {
 113                 return fmt.Errorf("invalid client id %v", *t.clientID)
 114         }
 115         userName := string(client.UserName)
 116         login := client.Account.Login
 117
 118         handler := TransactionHandlers[requestNum]
 119
 120         b, err := t.MarshalBinary()
 121         if err != nil {
 122                 return err
 123         }
 124         var n int
 125         if n, err = client.Connection.Write(b); err != nil {
 126                 return err
 127         }
 128         s.Logger.Debugw("Sent Transaction",
 129                 "name", userName,
 130                 "login", login,
 131                 "IsReply", t.IsReply,
 132                 "type", handler.Name,
 133                 "sentBytes", n,
 134                 "remoteAddr", client.Connection.RemoteAddr(),
 135         )
 136         return nil
 137 }
 138
 139 func (s *Server) Serve(ctx context.Context, cancelRoot context.CancelFunc, ln net.Listener) error {
 140         s.Logger.Infow("Hotline server started", "Addr", fmt.Sprintf(":%v", s.Port))
 141
 142         for {
 143                 conn, err := ln.Accept()
 144                 if err != nil {
 145                         s.Logger.Errorw("error accepting connection", "err", err)
 146                 }
 147
 148                 go func() {
 149                         for {
 150                                 t := <-s.outbox
 151                                 go func() {
 152                                         if err := s.sendTransaction(t); err != nil {
 153                                                 s.Logger.Errorw("error sending transaction", "err", err)
 154                                         }
 155                                 }()
 156                         }
 157                 }()
 158                 go func() {
 159                         if err := s.handleNewConnection(conn); err != nil {
 160                                 if err == io.EOF {
 161                                         s.Logger.Infow("Client disconnected", "RemoteAddr", conn.RemoteAddr())
 162                                 } else {
 163                                         s.Logger.Errorw("error serving request", "RemoteAddr", conn.RemoteAddr(), "err", err)
 164                                 }
 165                         }
 166                 }()
 167         }
 168 }
 169
 170 const (
 171         agreementFile = "Agreement.txt"
 172 )
 173
 174 // NewServer constructs a new Server from a config dir
 175 func NewServer(configDir, netInterface string, netPort int, logger *zap.SugaredLogger) (*Server, error) {
 176         server := Server{
 177                 Port:          netPort,
 178                 Accounts:      make(map[string]*Account),
 179                 Config:        new(Config),
 180                 Clients:       make(map[uint16]*ClientConn),
 181                 FileTransfers: make(map[uint32]*FileTransfer),
 182                 PrivateChats:  make(map[uint32]*PrivateChat),
 183                 ConfigDir:     configDir,
 184                 Logger:        logger,
 185                 NextGuestID:   new(uint16),
 186                 outbox:        make(chan Transaction),
 187                 Stats:         &Stats{StartTime: time.Now()},
 188                 ThreadedNews:  &ThreadedNews{},
 189                 TrackerPassID: make([]byte, 4),
 190         }
 191
 192         ln, err := net.Listen("tcp", fmt.Sprintf("%s:%v", netInterface, netPort))
 193         if err != nil {
 194                 return nil, err
 195         }
 196         server.APIListener = ln
 197
 198         if netPort != 0 {
 199                 netPort += 1
 200         }
 201
 202         ln2, err := net.Listen("tcp", fmt.Sprintf("%s:%v", netInterface, netPort))
 203         server.FileListener = ln2
 204         if err != nil {
 205                 return nil, err
 206         }
 207
 208         // generate a new random passID for tracker registration
 209         if _, err := rand.Read(server.TrackerPassID); err != nil {
 210                 return nil, err
 211         }
 212
 213         server.Logger.Debugw("Loading Agreement", "path", configDir+agreementFile)
 214         if server.Agreement, err = os.ReadFile(configDir + agreementFile); err != nil {
 215                 return nil, err
 216         }
 217
 218         if server.FlatNews, err = os.ReadFile(configDir + "MessageBoard.txt"); err != nil {
 219                 return nil, err
 220         }
 221
 222         if err := server.loadThreadedNews(configDir + "ThreadedNews.yaml"); err != nil {
 223                 return nil, err
 224         }
 225
 226         if err := server.loadConfig(configDir + "config.yaml"); err != nil {
 227                 return nil, err
 228         }
 229
 230         if err := server.loadAccounts(configDir + "Users/"); err != nil {
 231                 return nil, err
 232         }
 233
 234         server.Config.FileRoot = configDir + "Files/"
 235
 236         *server.NextGuestID = 1
 237
 238         if server.Config.EnableTrackerRegistration {
 239                 server.Logger.Infow(
 240                         "Tracker registration enabled",
 241                         "frequency", fmt.Sprintf("%vs", trackerUpdateFrequency),
 242                         "trackers", server.Config.Trackers,
 243                 )
 244
 245                 go func() {
 246                         for {
 247                                 tr := &TrackerRegistration{
 248                                         Port:        []byte{0x15, 0x7c},
 249                                         UserCount:   server.userCount(),
 250                                         PassID:      server.TrackerPassID,
 251                                         Name:        server.Config.Name,
 252                                         Description: server.Config.Description,
 253                                 }
 254                                 for _, t := range server.Config.Trackers {
 255                                         if err := register(t, tr); err != nil {
 256                                                 server.Logger.Errorw("unable to register with tracker %v", "error", err)
 257                                         }
 258                                         server.Logger.Infow("Sent Tracker registration", "data", tr)
 259                                 }
 260
 261                                 time.Sleep(trackerUpdateFrequency * time.Second)
 262                         }
 263                 }()
 264         }
 265
 266         // Start Client Keepalive go routine
 267         go server.keepaliveHandler()
 268
 269         return &server, nil
 270 }
 271
 272 func (s *Server) userCount() int {
 273         s.mux.Lock()
 274         defer s.mux.Unlock()
 275
 276         return len(s.Clients)
 277 }
 278
 279 func (s *Server) keepaliveHandler() {
 280         for {
 281                 time.Sleep(idleCheckInterval * time.Second)
 282                 s.mux.Lock()
 283
 284                 for _, c := range s.Clients {
 285                         c.IdleTime += idleCheckInterval
 286                         if c.IdleTime > userIdleSeconds && !c.Idle {
 287                                 c.Idle = true
 288
 289                                 flagBitmap := big.NewInt(int64(binary.BigEndian.Uint16(*c.Flags)))
 290                                 flagBitmap.SetBit(flagBitmap, userFlagAway, 1)
 291                                 binary.BigEndian.PutUint16(*c.Flags, uint16(flagBitmap.Int64()))
 292
 293                                 c.sendAll(
 294                                         tranNotifyChangeUser,
 295                                         NewField(fieldUserID, *c.ID),
 296                                         NewField(fieldUserFlags, *c.Flags),
 297                                         NewField(fieldUserName, c.UserName),
 298                                         NewField(fieldUserIconID, *c.Icon),
 299                                 )
 300                         }
 301                 }
 302                 s.mux.Unlock()
 303         }
 304 }
 305
 306 func (s *Server) writeThreadedNews() error {
 307         s.mux.Lock()
 308         defer s.mux.Unlock()
 309
 310         out, err := yaml.Marshal(s.ThreadedNews)
 311         if err != nil {
 312                 return err
 313         }
 314         err = ioutil.WriteFile(
 315                 s.ConfigDir+"ThreadedNews.yaml",
 316                 out,
 317                 0666,
 318         )
 319         return err
 320 }
 321
 322 func (s *Server) NewClientConn(conn net.Conn) *ClientConn {
 323         s.mux.Lock()
 324         defer s.mux.Unlock()
 325
 326         clientConn := &ClientConn{
 327                 ID:         &[]byte{0, 0},
 328                 Icon:       &[]byte{0, 0},
 329                 Flags:      &[]byte{0, 0},
 330                 UserName:   []byte{},
 331                 Connection: conn,
 332                 Server:     s,
 333                 Version:    &[]byte{},
 334                 AutoReply:  []byte{},
 335                 Transfers:  make(map[int][]*FileTransfer),
 336                 Agreed:     false,
 337         }
 338         *s.NextGuestID++
 339         ID := *s.NextGuestID
 340
 341         binary.BigEndian.PutUint16(*clientConn.ID, ID)
 342         s.Clients[ID] = clientConn
 343
 344         return clientConn
 345 }
 346
 347 // NewUser creates a new user account entry in the server map and config file
 348 func (s *Server) NewUser(login, name, password string, access []byte) error {
 349         s.mux.Lock()
 350         defer s.mux.Unlock()
 351
 352         account := Account{
 353                 Login:    login,
 354                 Name:     name,
 355                 Password: hashAndSalt([]byte(password)),
 356                 Access:   &access,
 357         }
 358         out, err := yaml.Marshal(&account)
 359         if err != nil {
 360                 return err
 361         }
 362         s.Accounts[login] = &account
 363
 364         return FS.WriteFile(s.ConfigDir+"Users/"+login+".yaml", out, 0666)
 365 }
 366
 367 func (s *Server) UpdateUser(login, newLogin, name, password string, access []byte) error {
 368         s.mux.Lock()
 369         defer s.mux.Unlock()
 370
 371         fmt.Printf("login: %v, newLogin: %v: ", login, newLogin)
 372
 373         // update renames the user login
 374         if login != newLogin {
 375                 err := os.Rename(s.ConfigDir+"Users/"+login+".yaml", s.ConfigDir+"Users/"+newLogin+".yaml")
 376                 if err != nil {
 377                         return err
 378                 }
 379                 s.Accounts[newLogin] = s.Accounts[login]
 380                 delete(s.Accounts, login)
 381         }
 382
 383         account := s.Accounts[newLogin]
 384         account.Access = &access
 385         account.Name = name
 386         account.Password = password
 387
 388         out, err := yaml.Marshal(&account)
 389         if err != nil {
 390                 return err
 391         }
 392         if err := os.WriteFile(s.ConfigDir+"Users/"+newLogin+".yaml", out, 0666); err != nil {
 393                 return err
 394         }
 395
 396         return nil
 397 }
 398
 399 // DeleteUser deletes the user account
 400 func (s *Server) DeleteUser(login string) error {
 401         s.mux.Lock()
 402         defer s.mux.Unlock()
 403
 404         delete(s.Accounts, login)
 405
 406         return FS.Remove(s.ConfigDir + "Users/" + login + ".yaml")
 407 }
 408
 409 func (s *Server) connectedUsers() []Field {
 410         s.mux.Lock()
 411         defer s.mux.Unlock()
 412
 413         var connectedUsers []Field
 414         for _, c := range sortedClients(s.Clients) {
 415                 if !c.Agreed {
 416                         continue
 417                 }
 418                 user := User{
 419                         ID:    *c.ID,
 420                         Icon:  *c.Icon,
 421                         Flags: *c.Flags,
 422                         Name:  string(c.UserName),
 423                 }
 424                 connectedUsers = append(connectedUsers, NewField(fieldUsernameWithInfo, user.Payload()))
 425         }
 426         return connectedUsers
 427 }
 428
 429 // loadThreadedNews loads the threaded news data from disk
 430 func (s *Server) loadThreadedNews(threadedNewsPath string) error {
 431         fh, err := os.Open(threadedNewsPath)
 432         if err != nil {
 433                 return err
 434         }
 435         decoder := yaml.NewDecoder(fh)
 436
 437         return decoder.Decode(s.ThreadedNews)
 438 }
 439
 440 // loadAccounts loads account data from disk
 441 func (s *Server) loadAccounts(userDir string) error {
 442         matches, err := filepath.Glob(path.Join(userDir, "*.yaml"))
 443         if err != nil {
 444                 return err
 445         }
 446
 447         if len(matches) == 0 {
 448                 return errors.New("no user accounts found in " + userDir)
 449         }
 450
 451         for _, file := range matches {
 452                 fh, err := FS.Open(file)
 453                 if err != nil {
 454                         return err
 455                 }
 456
 457                 account := Account{}
 458                 decoder := yaml.NewDecoder(fh)
 459                 if err := decoder.Decode(&account); err != nil {
 460                         return err
 461                 }
 462
 463                 s.Accounts[account.Login] = &account
 464         }
 465         return nil
 466 }
 467
 468 func (s *Server) loadConfig(path string) error {
 469         fh, err := FS.Open(path)
 470         if err != nil {
 471                 return err
 472         }
 473
 474         decoder := yaml.NewDecoder(fh)
 475         err = decoder.Decode(s.Config)
 476         if err != nil {
 477                 return err
 478         }
 479         return nil
 480 }
 481
 482 const (
 483         minTransactionLen = 22 // minimum length of any transaction
 484 )
 485
 486 // dontPanic recovers and logs panics instead of crashing
 487 // TODO: remove this after known issues are fixed
 488 func dontPanic(logger *zap.SugaredLogger) {
 489         if r := recover(); r != nil {
 490                 fmt.Println("stacktrace from panic: \n" + string(debug.Stack()))
 491                 logger.Errorw("PANIC", "err", r, "trace", string(debug.Stack()))
 492         }
 493 }
 494
 495 // handleNewConnection takes a new net.Conn and performs the initial login sequence
 496 func (s *Server) handleNewConnection(conn net.Conn) error {
 497         defer dontPanic(s.Logger)
 498
 499         handshakeBuf := make([]byte, 12)
 500         if _, err := io.ReadFull(conn, handshakeBuf); err != nil {
 501                 return err
 502         }
 503         if err := Handshake(conn, handshakeBuf); err != nil {
 504                 return err
 505         }
 506
 507         buf := make([]byte, 1024)
 508         // TODO: fix potential short read with io.ReadFull
 509         readLen, err := conn.Read(buf)
 510         if readLen < minTransactionLen {
 511                 return err
 512         }
 513         if err != nil {
 514                 return err
 515         }
 516
 517         clientLogin, _, err := ReadTransaction(buf[:readLen])
 518         if err != nil {
 519                 return err
 520         }
 521
 522         c := s.NewClientConn(conn)
 523         defer c.Disconnect()
 524
 525         encodedLogin := clientLogin.GetField(fieldUserLogin).Data
 526         encodedPassword := clientLogin.GetField(fieldUserPassword).Data
 527         *c.Version = clientLogin.GetField(fieldVersion).Data
 528
 529         var login string
 530         for _, char := range encodedLogin {
 531                 login += string(rune(255 - uint(char)))
 532         }
 533         if login == "" {
 534                 login = GuestAccount
 535         }
 536
 537         // If authentication fails, send error reply and close connection
 538         if !c.Authenticate(login, encodedPassword) {
 539                 t := c.NewErrReply(clientLogin, "Incorrect login.")
 540                 b, err := t.MarshalBinary()
 541                 if err != nil {
 542                         return err
 543                 }
 544                 if _, err := conn.Write(b); err != nil {
 545                         return err
 546                 }
 547                 return fmt.Errorf("incorrect login")
 548         }
 549
 550         if clientLogin.GetField(fieldUserName).Data != nil {
 551                 c.UserName = clientLogin.GetField(fieldUserName).Data
 552         }
 553
 554         if clientLogin.GetField(fieldUserIconID).Data != nil {
 555                 *c.Icon = clientLogin.GetField(fieldUserIconID).Data
 556         }
 557
 558         c.Account = c.Server.Accounts[login]
 559
 560         if c.Authorize(accessDisconUser) {
 561                 *c.Flags = []byte{0, 2}
 562         }
 563
 564         s.Logger.Infow("Client connection received", "login", login, "version", *c.Version, "RemoteAddr", conn.RemoteAddr().String())
 565
 566         s.outbox <- c.NewReply(clientLogin,
 567                 NewField(fieldVersion, []byte{0x00, 0xbe}),
 568                 NewField(fieldCommunityBannerID, []byte{0x00, 0x01}),
 569                 NewField(fieldServerName, []byte(s.Config.Name)),
 570         )
 571
 572         // Send user access privs so client UI knows how to behave
 573         c.Server.outbox <- *NewTransaction(tranUserAccess, c.ID, NewField(fieldUserAccess, *c.Account.Access))
 574
 575         // Show agreement to client
 576         c.Server.outbox <- *NewTransaction(tranShowAgreement, c.ID, NewField(fieldData, s.Agreement))
 577
 578         // assume simplified hotline v1.2.3 login flow that does not require agreement
 579         if *c.Version == nil {
 580                 c.Agreed = true
 581
 582                 c.notifyOthers(
 583                         *NewTransaction(
 584                                 tranNotifyChangeUser, nil,
 585                                 NewField(fieldUserName, c.UserName),
 586                                 NewField(fieldUserID, *c.ID),
 587                                 NewField(fieldUserIconID, *c.Icon),
 588                                 NewField(fieldUserFlags, *c.Flags),
 589                         ),
 590                 )
 591         }
 592
 593         c.Server.Stats.LoginCount += 1
 594
 595         const readBuffSize = 1024000 // 1KB - TODO: what should this be?
 596         tranBuff := make([]byte, 0)
 597         tReadlen := 0
 598         // Infinite loop where take action on incoming client requests until the connection is closed
 599         for {
 600                 buf = make([]byte, readBuffSize)
 601                 tranBuff = tranBuff[tReadlen:]
 602
 603                 readLen, err := c.Connection.Read(buf)
 604                 if err != nil {
 605                         return err
 606                 }
 607                 tranBuff = append(tranBuff, buf[:readLen]...)
 608
 609                 // We may have read multiple requests worth of bytes from Connection.Read.  readTransactions splits them
 610                 // into a slice of transactions
 611                 var transactions []Transaction
 612                 if transactions, tReadlen, err = readTransactions(tranBuff); err != nil {
 613                         c.Server.Logger.Errorw("Error handling transaction", "err", err)
 614                 }
 615
 616                 // iterate over all of the transactions that were parsed from the byte slice and handle them
 617                 for _, t := range transactions {
 618                         if err := c.handleTransaction(&t); err != nil {
 619                                 c.Server.Logger.Errorw("Error handling transaction", "err", err)
 620                         }
 621                 }
 622         }
 623 }
 624
 625 // NewTransactionRef generates a random ID for the file transfer.  The Hotline client includes this ID
 626 // in the file transfer request payload, and the file transfer server will use it to map the request
 627 // to a transfer
 628 func (s *Server) NewTransactionRef() []byte {
 629         transactionRef := make([]byte, 4)
 630         rand.Read(transactionRef)
 631
 632         return transactionRef
 633 }
 634
 635 func (s *Server) NewPrivateChat(cc *ClientConn) []byte {
 636         s.mux.Lock()
 637         defer s.mux.Unlock()
 638
 639         randID := make([]byte, 4)
 640         rand.Read(randID)
 641         data := binary.BigEndian.Uint32(randID[:])
 642
 643         s.PrivateChats[data] = &PrivateChat{
 644                 Subject:    "",
 645                 ClientConn: make(map[uint16]*ClientConn),
 646         }
 647         s.PrivateChats[data].ClientConn[cc.uint16ID()] = cc
 648
 649         return randID
 650 }
 651
 652 const dlFldrActionSendFile = 1
 653 const dlFldrActionResumeFile = 2
 654 const dlFldrActionNextFile = 3
 655
 656 // handleFileTransfer receives a client net.Conn from the file transfer server, performs the requested transfer type, then closes the connection
 657 func (s *Server) handleFileTransfer(conn io.ReadWriteCloser) error {
 658         defer func() {
 659
 660                 if err := conn.Close(); err != nil {
 661                         s.Logger.Errorw("error closing connection", "error", err)
 662                 }
 663         }()
 664
 665         defer dontPanic(s.Logger)
 666
 667         txBuf := make([]byte, 16)
 668         if _, err := io.ReadFull(conn, txBuf); err != nil {
 669                 return err
 670         }
 671
 672         var t transfer
 673         if _, err := t.Write(txBuf); err != nil {
 674                 return err
 675         }
 676
 677         transferRefNum := binary.BigEndian.Uint32(t.ReferenceNumber[:])
 678         defer func() {
 679                 s.mux.Lock()
 680                 delete(s.FileTransfers, transferRefNum)
 681                 s.mux.Unlock()
 682         }()
 683
 684         s.mux.Lock()
 685         fileTransfer, ok := s.FileTransfers[transferRefNum]
 686         s.mux.Unlock()
 687         if !ok {
 688                 return errors.New("invalid transaction ID")
 689         }
 690
 691         switch fileTransfer.Type {
 692         case FileDownload:
 693                 fullFilePath, err := readPath(s.Config.FileRoot, fileTransfer.FilePath, fileTransfer.FileName)
 694                 if err != nil {
 695                         return err
 696                 }
 697
 698                 var dataOffset int64
 699                 if fileTransfer.fileResumeData != nil {
 700                         dataOffset = int64(binary.BigEndian.Uint32(fileTransfer.fileResumeData.ForkInfoList[0].DataSize[:]))
 701                 }
 702
 703                 ffo, err := NewFlattenedFileObject(s.Config.FileRoot, fileTransfer.FilePath, fileTransfer.FileName, dataOffset)
 704                 if err != nil {
 705                         return err
 706                 }
 707
 708                 s.Logger.Infow("File download started", "filePath", fullFilePath, "transactionRef", fileTransfer.ReferenceNumber)
 709
 710                 if fileTransfer.options == nil {
 711                         // Start by sending flat file object to client
 712                         if _, err := conn.Write(ffo.BinaryMarshal()); err != nil {
 713                                 return err
 714                         }
 715                 }
 716
 717                 file, err := FS.Open(fullFilePath)
 718                 if err != nil {
 719                         return err
 720                 }
 721
 722                 sendBuffer := make([]byte, 1048576)
 723                 var totalSent int64
 724                 for {
 725                         var bytesRead int
 726                         if bytesRead, err = file.ReadAt(sendBuffer, dataOffset+totalSent); err == io.EOF {
 727                                 if _, err := conn.Write(sendBuffer[:bytesRead]); err != nil {
 728                                         return err
 729                                 }
 730                                 break
 731                         }
 732                         if err != nil {
 733                                 return err
 734                         }
 735                         totalSent += int64(bytesRead)
 736
 737                         fileTransfer.BytesSent += bytesRead
 738
 739                         if _, err := conn.Write(sendBuffer[:bytesRead]); err != nil {
 740                                 return err
 741                         }
 742                 }
 743         case FileUpload:
 744                 destinationFile := s.Config.FileRoot + ReadFilePath(fileTransfer.FilePath) + "/" + string(fileTransfer.FileName)
 745
 746                 var file *os.File
 747
 748                 // A file upload has three possible cases:
 749                 // 1) Upload a new file
 750                 // 2) Resume a partially transferred file
 751                 // 3) Replace a fully uploaded file
 752                 // Unfortunately we have to infer which case applies by inspecting what is already on the file system
 753
 754                 // 1) Check for existing file:
 755                 _, err := os.Stat(destinationFile)
 756                 if err == nil {
 757                         // If found, that means this upload is intended to replace the file
 758                         if err = os.Remove(destinationFile); err != nil {
 759                                 return err
 760                         }
 761                         file, err = os.Create(destinationFile + incompleteFileSuffix)
 762                 }
 763                 if errors.Is(err, fs.ErrNotExist) {
 764                         // If not found, open or create a new incomplete file
 765                         file, err = os.OpenFile(destinationFile+incompleteFileSuffix, os.O_CREATE|os.O_APPEND|os.O_WRONLY, 0644)
 766                         if err != nil {
 767                                 return err
 768                         }
 769                 }
 770
 771                 defer func() { _ = file.Close() }()
 772
 773                 s.Logger.Infow("File upload started", "transactionRef", fileTransfer.ReferenceNumber, "dstFile", destinationFile)
 774
 775                 // TODO: replace io.Discard with a real file when ready to implement storing of resource fork data
 776                 if err := receiveFile(conn, file, io.Discard); err != nil {
 777                         return err
 778                 }
 779
 780                 if err := os.Rename(destinationFile+".incomplete", destinationFile); err != nil {
 781                         return err
 782                 }
 783
 784                 s.Logger.Infow("File upload complete", "transactionRef", fileTransfer.ReferenceNumber, "dstFile", destinationFile)
 785         case FolderDownload:
 786                 // Folder Download flow:
 787                 // 1. Get filePath from the transfer
 788                 // 2. Iterate over files
 789                 // 3. For each file:
 790                 //       Send file header to client
 791                 // The client can reply in 3 ways:
 792                 //
 793                 // 1. If type is an odd number (unknown type?), or file download for the current file is completed:
 794                 //              client sends []byte{0x00, 0x03} to tell the server to continue to the next file
 795                 //
 796                 // 2. If download of a file is to be resumed:
 797                 //              client sends:
 798                 //                      []byte{0x00, 0x02} // download folder action
 799                 //                      [2]byte // Resume data size
 800                 //                      []byte file resume data (see myField_FileResumeData)
 801                 //
 802                 // 3. Otherwise, download of the file is requested and client sends []byte{0x00, 0x01}
 803                 //
 804                 // When download is requested (case 2 or 3), server replies with:
 805                 //                      [4]byte - file size
 806                 //                      []byte  - Flattened File Object
 807                 //
 808                 // After every file download, client could request next file with:
 809                 //                      []byte{0x00, 0x03}
 810                 //
 811                 // This notifies the server to send the next item header
 812
 813                 fullFilePath, err := readPath(s.Config.FileRoot, fileTransfer.FilePath, fileTransfer.FileName)
 814                 if err != nil {
 815                         return err
 816                 }
 817
 818                 basePathLen := len(fullFilePath)
 819
 820                 s.Logger.Infow("Start folder download", "path", fullFilePath, "ReferenceNumber", fileTransfer.ReferenceNumber)
 821
 822                 nextAction := make([]byte, 2)
 823                 if _, err := io.ReadFull(conn, nextAction); err != nil {
 824                         return err
 825                 }
 826
 827                 i := 0
 828                 err = filepath.Walk(fullFilePath+"/", func(path string, info os.FileInfo, err error) error {
 829                         if err != nil {
 830                                 return err
 831                         }
 832                         i += 1
 833                         subPath := path[basePathLen+1:]
 834                         s.Logger.Infow("Sending fileheader", "i", i, "path", path, "fullFilePath", fullFilePath, "subPath", subPath, "IsDir", info.IsDir())
 835
 836                         if i == 1 {
 837                                 return nil
 838                         }
 839
 840                         fileHeader := NewFileHeader(subPath, info.IsDir())
 841
 842                         // Send the file header to client
 843                         if _, err := conn.Write(fileHeader.Payload()); err != nil {
 844                                 s.Logger.Errorf("error sending file header: %v", err)
 845                                 return err
 846                         }
 847
 848                         // Read the client's Next Action request
 849                         if _, err := io.ReadFull(conn, nextAction); err != nil {
 850                                 return err
 851                         }
 852
 853                         s.Logger.Infow("Client folder download action", "action", fmt.Sprintf("%X", nextAction[0:2]))
 854
 855                         var dataOffset int64
 856
 857                         switch nextAction[1] {
 858                         case dlFldrActionResumeFile:
 859                                 // client asked to resume this file
 860                                 var frd FileResumeData
 861                                 // get size of resumeData
 862                                 if _, err := io.ReadFull(conn, nextAction); err != nil {
 863                                         return err
 864                                 }
 865
 866                                 resumeDataLen := binary.BigEndian.Uint16(nextAction)
 867                                 resumeDataBytes := make([]byte, resumeDataLen)
 868                                 if _, err := io.ReadFull(conn, resumeDataBytes); err != nil {
 869                                         return err
 870                                 }
 871
 872                                 if err := frd.UnmarshalBinary(resumeDataBytes); err != nil {
 873                                         return err
 874                                 }
 875                                 dataOffset = int64(binary.BigEndian.Uint32(frd.ForkInfoList[0].DataSize[:]))
 876                         case dlFldrActionNextFile:
 877                                 // client asked to skip this file
 878                                 return nil
 879                         }
 880
 881                         if info.IsDir() {
 882                                 return nil
 883                         }
 884
 885                         splitPath := strings.Split(path, "/")
 886
 887                         ffo, err := NewFlattenedFileObject(strings.Join(splitPath[:len(splitPath)-1], "/"), nil, []byte(info.Name()), dataOffset)
 888                         if err != nil {
 889                                 return err
 890                         }
 891                         s.Logger.Infow("File download started",
 892                                 "fileName", info.Name(),
 893                                 "transactionRef", fileTransfer.ReferenceNumber,
 894                                 "TransferSize", fmt.Sprintf("%x", ffo.TransferSize()),
 895                         )
 896
 897                         // Send file size to client
 898                         if _, err := conn.Write(ffo.TransferSize()); err != nil {
 899                                 s.Logger.Error(err)
 900                                 return err
 901                         }
 902
 903                         // Send ffo bytes to client
 904                         if _, err := conn.Write(ffo.BinaryMarshal()); err != nil {
 905                                 s.Logger.Error(err)
 906                                 return err
 907                         }
 908
 909                         file, err := FS.Open(path)
 910                         if err != nil {
 911                                 return err
 912                         }
 913
 914                         // // Copy N bytes from file to connection
 915                         // _, err = io.CopyN(conn, file, int64(binary.BigEndian.Uint32(ffo.FlatFileDataForkHeader.DataSize[:])))
 916                         // if err != nil {
 917                         //      return err
 918                         // }
 919                         // file.Close()
 920                         sendBuffer := make([]byte, 1048576)
 921                         var totalSent int64
 922                         for {
 923                                 var bytesRead int
 924                                 if bytesRead, err = file.ReadAt(sendBuffer, dataOffset+totalSent); err == io.EOF {
 925                                         if _, err := conn.Write(sendBuffer[:bytesRead]); err != nil {
 926                                                 return err
 927                                         }
 928                                         break
 929                                 }
 930                                 if err != nil {
 931                                         panic(err)
 932                                 }
 933                                 totalSent += int64(bytesRead)
 934
 935                                 fileTransfer.BytesSent += bytesRead
 936
 937                                 if _, err := conn.Write(sendBuffer[:bytesRead]); err != nil {
 938                                         return err
 939                                 }
 940                         }
 941
 942                         // TODO: optionally send resource fork header and resource fork data
 943
 944                         // Read the client's Next Action request.  This is always 3, I think?
 945                         if _, err := io.ReadFull(conn, nextAction); err != nil {
 946                                 return err
 947                         }
 948
 949                         return nil
 950                 })
 951
 952         case FolderUpload:
 953                 dstPath, err := readPath(s.Config.FileRoot, fileTransfer.FilePath, fileTransfer.FileName)
 954                 if err != nil {
 955                         return err
 956                 }
 957                 s.Logger.Infow(
 958                         "Folder upload started",
 959                         "transactionRef", fileTransfer.ReferenceNumber,
 960                         "dstPath", dstPath,
 961                         "TransferSize", fmt.Sprintf("%x", fileTransfer.TransferSize),
 962                         "FolderItemCount", fileTransfer.FolderItemCount,
 963                 )
 964
 965                 // Check if the target folder exists.  If not, create it.
 966                 if _, err := FS.Stat(dstPath); os.IsNotExist(err) {
 967                         if err := FS.Mkdir(dstPath, 0777); err != nil {
 968                                 return err
 969                         }
 970                 }
 971
 972                 // Begin the folder upload flow by sending the "next file action" to client
 973                 if _, err := conn.Write([]byte{0, dlFldrActionNextFile}); err != nil {
 974                         return err
 975                 }
 976
 977                 fileSize := make([]byte, 4)
 978                 readBuffer := make([]byte, 1024)
 979
 980                 for i := 0; i < fileTransfer.ItemCount(); i++ {
 981                         // TODO: fix potential short read with io.ReadFull
 982                         _, err := conn.Read(readBuffer)
 983                         if err != nil {
 984                                 return err
 985                         }
 986                         fu := readFolderUpload(readBuffer)
 987
 988                         s.Logger.Infow(
 989                                 "Folder upload continued",
 990                                 "transactionRef", fmt.Sprintf("%x", fileTransfer.ReferenceNumber),
 991                                 "FormattedPath", fu.FormattedPath(),
 992                                 "IsFolder", fmt.Sprintf("%x", fu.IsFolder),
 993                                 "PathItemCount", binary.BigEndian.Uint16(fu.PathItemCount[:]),
 994                         )
 995
 996                         if fu.IsFolder == [2]byte{0, 1} {
 997                                 if _, err := os.Stat(dstPath + "/" + fu.FormattedPath()); os.IsNotExist(err) {
 998                                         if err := os.Mkdir(dstPath+"/"+fu.FormattedPath(), 0777); err != nil {
 999                                                 return err
1000                                         }
1001                                 }
1002
1003                                 // Tell client to send next file
1004                                 if _, err := conn.Write([]byte{0, dlFldrActionNextFile}); err != nil {
1005                                         return err
1006                                 }
1007                         } else {
1008                                 nextAction := dlFldrActionSendFile
1009
1010                                 // Check if we have the full file already.  If so, send dlFldrAction_NextFile to client to skip.
1011                                 _, err := os.Stat(dstPath + "/" + fu.FormattedPath())
1012                                 if err != nil && !errors.Is(err, fs.ErrNotExist) {
1013                                         return err
1014                                 }
1015                                 if err == nil {
1016                                         nextAction = dlFldrActionNextFile
1017                                 }
1018
1019                                 //  Check if we have a partial file already.  If so, send dlFldrAction_ResumeFile to client to resume upload.
1020                                 inccompleteFile, err := os.Stat(dstPath + "/" + fu.FormattedPath() + incompleteFileSuffix)
1021                                 if err != nil && !errors.Is(err, fs.ErrNotExist) {
1022                                         return err
1023                                 }
1024                                 if err == nil {
1025                                         nextAction = dlFldrActionResumeFile
1026                                 }
1027
1028                                 fmt.Printf("Next Action: %v\n", nextAction)
1029
1030                                 if _, err := conn.Write([]byte{0, uint8(nextAction)}); err != nil {
1031                                         return err
1032                                 }
1033
1034                                 switch nextAction {
1035                                 case dlFldrActionNextFile:
1036                                         continue
1037                                 case dlFldrActionResumeFile:
1038                                         offset := make([]byte, 4)
1039                                         binary.BigEndian.PutUint32(offset, uint32(inccompleteFile.Size()))
1040
1041                                         file, err := os.OpenFile(dstPath+"/"+fu.FormattedPath()+incompleteFileSuffix, os.O_APPEND|os.O_CREATE|os.O_WRONLY, 0644)
1042                                         if err != nil {
1043                                                 return err
1044                                         }
1045
1046                                         fileResumeData := NewFileResumeData([]ForkInfoList{
1047                                                 *NewForkInfoList(offset),
1048                                         })
1049
1050                                         b, _ := fileResumeData.BinaryMarshal()
1051
1052                                         bs := make([]byte, 2)
1053                                         binary.BigEndian.PutUint16(bs, uint16(len(b)))
1054
1055                                         if _, err := conn.Write(append(bs, b...)); err != nil {
1056                                                 return err
1057                                         }
1058
1059                                         if _, err := io.ReadFull(conn, fileSize); err != nil {
1060                                                 return err
1061                                         }
1062
1063                                         if err := receiveFile(conn, file, ioutil.Discard); err != nil {
1064                                                 s.Logger.Error(err)
1065                                         }
1066
1067                                         err = os.Rename(dstPath+"/"+fu.FormattedPath()+".incomplete", dstPath+"/"+fu.FormattedPath())
1068                                         if err != nil {
1069                                                 return err
1070                                         }
1071
1072                                 case dlFldrActionSendFile:
1073                                         if _, err := conn.Read(fileSize); err != nil {
1074                                                 return err
1075                                         }
1076
1077                                         filePath := dstPath + "/" + fu.FormattedPath()
1078                                         s.Logger.Infow("Starting file transfer", "path", filePath, "fileNum", i+1, "totalFiles", "zz", "fileSize", binary.BigEndian.Uint32(fileSize))
1079
1080                                         newFile, err := FS.Create(filePath + ".incomplete")
1081                                         if err != nil {
1082                                                 return err
1083                                         }
1084
1085                                         if err := receiveFile(conn, newFile, ioutil.Discard); err != nil {
1086                                                 s.Logger.Error(err)
1087                                         }
1088                                         _ = newFile.Close()
1089                                         if err := os.Rename(filePath+".incomplete", filePath); err != nil {
1090                                                 return err
1091                                         }
1092                                 }
1093
1094                                 // Tell client to send next file
1095                                 if _, err := conn.Write([]byte{0, dlFldrActionNextFile}); err != nil {
1096                                         return err
1097                                 }
1098                         }
1099                 }
1100                 s.Logger.Infof("Folder upload complete")
1101         }
1102
1103         return nil
1104 }
1105
1106 // sortedClients is a utility function that takes a map of *ClientConn and returns a sorted slice of the values.
1107 // The purpose of this is to ensure that the ordering of client connections is deterministic so that test assertions work.
1108 func sortedClients(unsortedClients map[uint16]*ClientConn) (clients []*ClientConn) {
1109         for _, c := range unsortedClients {
1110                 clients = append(clients, c)
1111         }
1112         sort.Sort(byClientID(clients))
1113         return clients
1114 }