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         "github.com/go-playground/validator/v10"
   9         "go.uber.org/zap"
  10         "io"
  11         "io/fs"
  12         "io/ioutil"
  13         "math/big"
  14         "math/rand"
  15         "net"
  16         "os"
  17         "path"
  18         "path/filepath"
  19         "runtime/debug"
  20         "sort"
  21         "strings"
  22         "sync"
  23         "time"
  24
  25         "gopkg.in/yaml.v3"
  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 [4]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.handleFileTransfer(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.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, conn.RemoteAddr().String()); 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         }
 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                                         UserCount:   server.userCount(),
 249                                         PassID:      server.TrackerPassID[:],
 250                                         Name:        server.Config.Name,
 251                                         Description: server.Config.Description,
 252                                 }
 253                                 binary.BigEndian.PutUint16(tr.Port[:], uint16(server.Port))
 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, remoteAddr string) *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                 RemoteAddr: remoteAddr,
 338         }
 339         *s.NextGuestID++
 340         ID := *s.NextGuestID
 341
 342         binary.BigEndian.PutUint16(*clientConn.ID, ID)
 343         s.Clients[ID] = clientConn
 344
 345         return clientConn
 346 }
 347
 348 // NewUser creates a new user account entry in the server map and config file
 349 func (s *Server) NewUser(login, name, password string, access []byte) error {
 350         s.mux.Lock()
 351         defer s.mux.Unlock()
 352
 353         account := Account{
 354                 Login:    login,
 355                 Name:     name,
 356                 Password: hashAndSalt([]byte(password)),
 357                 Access:   &access,
 358         }
 359         out, err := yaml.Marshal(&account)
 360         if err != nil {
 361                 return err
 362         }
 363         s.Accounts[login] = &account
 364
 365         return FS.WriteFile(s.ConfigDir+"Users/"+login+".yaml", out, 0666)
 366 }
 367
 368 func (s *Server) UpdateUser(login, newLogin, name, password string, access []byte) error {
 369         s.mux.Lock()
 370         defer s.mux.Unlock()
 371
 372         fmt.Printf("login: %v, newLogin: %v: ", login, newLogin)
 373
 374         // update renames the user login
 375         if login != newLogin {
 376                 err := os.Rename(s.ConfigDir+"Users/"+login+".yaml", s.ConfigDir+"Users/"+newLogin+".yaml")
 377                 if err != nil {
 378                         return err
 379                 }
 380                 s.Accounts[newLogin] = s.Accounts[login]
 381                 delete(s.Accounts, login)
 382         }
 383
 384         account := s.Accounts[newLogin]
 385         account.Access = &access
 386         account.Name = name
 387         account.Password = password
 388
 389         out, err := yaml.Marshal(&account)
 390         if err != nil {
 391                 return err
 392         }
 393         if err := os.WriteFile(s.ConfigDir+"Users/"+newLogin+".yaml", out, 0666); err != nil {
 394                 return err
 395         }
 396
 397         return nil
 398 }
 399
 400 // DeleteUser deletes the user account
 401 func (s *Server) DeleteUser(login string) error {
 402         s.mux.Lock()
 403         defer s.mux.Unlock()
 404
 405         delete(s.Accounts, login)
 406
 407         return FS.Remove(s.ConfigDir + "Users/" + login + ".yaml")
 408 }
 409
 410 func (s *Server) connectedUsers() []Field {
 411         s.mux.Lock()
 412         defer s.mux.Unlock()
 413
 414         var connectedUsers []Field
 415         for _, c := range sortedClients(s.Clients) {
 416                 if !c.Agreed {
 417                         continue
 418                 }
 419                 user := User{
 420                         ID:    *c.ID,
 421                         Icon:  *c.Icon,
 422                         Flags: *c.Flags,
 423                         Name:  string(c.UserName),
 424                 }
 425                 connectedUsers = append(connectedUsers, NewField(fieldUsernameWithInfo, user.Payload()))
 426         }
 427         return connectedUsers
 428 }
 429
 430 // loadThreadedNews loads the threaded news data from disk
 431 func (s *Server) loadThreadedNews(threadedNewsPath string) error {
 432         fh, err := os.Open(threadedNewsPath)
 433         if err != nil {
 434                 return err
 435         }
 436         decoder := yaml.NewDecoder(fh)
 437
 438         return decoder.Decode(s.ThreadedNews)
 439 }
 440
 441 // loadAccounts loads account data from disk
 442 func (s *Server) loadAccounts(userDir string) error {
 443         matches, err := filepath.Glob(path.Join(userDir, "*.yaml"))
 444         if err != nil {
 445                 return err
 446         }
 447
 448         if len(matches) == 0 {
 449                 return errors.New("no user accounts found in " + userDir)
 450         }
 451
 452         for _, file := range matches {
 453                 fh, err := FS.Open(file)
 454                 if err != nil {
 455                         return err
 456                 }
 457
 458                 account := Account{}
 459                 decoder := yaml.NewDecoder(fh)
 460                 if err := decoder.Decode(&account); err != nil {
 461                         return err
 462                 }
 463
 464                 s.Accounts[account.Login] = &account
 465         }
 466         return nil
 467 }
 468
 469 func (s *Server) loadConfig(path string) error {
 470         fh, err := FS.Open(path)
 471         if err != nil {
 472                 return err
 473         }
 474
 475         decoder := yaml.NewDecoder(fh)
 476         err = decoder.Decode(s.Config)
 477         if err != nil {
 478                 return err
 479         }
 480
 481         validate := validator.New()
 482         err = validate.Struct(s.Config)
 483         if err != nil {
 484                 return err
 485         }
 486         return nil
 487 }
 488
 489 const (
 490         minTransactionLen = 22 // minimum length of any transaction
 491 )
 492
 493 // dontPanic recovers and logs panics instead of crashing
 494 // TODO: remove this after known issues are fixed
 495 func dontPanic(logger *zap.SugaredLogger) {
 496         if r := recover(); r != nil {
 497                 fmt.Println("stacktrace from panic: \n" + string(debug.Stack()))
 498                 logger.Errorw("PANIC", "err", r, "trace", string(debug.Stack()))
 499         }
 500 }
 501
 502 // handleNewConnection takes a new net.Conn and performs the initial login sequence
 503 func (s *Server) handleNewConnection(conn net.Conn, remoteAddr string) error {
 504         defer dontPanic(s.Logger)
 505
 506         if err := Handshake(conn); err != nil {
 507                 return err
 508         }
 509
 510         buf := make([]byte, 1024)
 511         // TODO: fix potential short read with io.ReadFull
 512         readLen, err := conn.Read(buf)
 513         if readLen < minTransactionLen {
 514                 return err
 515         }
 516         if err != nil {
 517                 return err
 518         }
 519
 520         clientLogin, _, err := ReadTransaction(buf[:readLen])
 521         if err != nil {
 522                 return err
 523         }
 524
 525         c := s.NewClientConn(conn, remoteAddr)
 526         defer c.Disconnect()
 527
 528         encodedLogin := clientLogin.GetField(fieldUserLogin).Data
 529         encodedPassword := clientLogin.GetField(fieldUserPassword).Data
 530         *c.Version = clientLogin.GetField(fieldVersion).Data
 531
 532         var login string
 533         for _, char := range encodedLogin {
 534                 login += string(rune(255 - uint(char)))
 535         }
 536         if login == "" {
 537                 login = GuestAccount
 538         }
 539
 540         // If authentication fails, send error reply and close connection
 541         if !c.Authenticate(login, encodedPassword) {
 542                 t := c.NewErrReply(clientLogin, "Incorrect login.")
 543                 b, err := t.MarshalBinary()
 544                 if err != nil {
 545                         return err
 546                 }
 547                 if _, err := conn.Write(b); err != nil {
 548                         return err
 549                 }
 550                 return fmt.Errorf("incorrect login")
 551         }
 552
 553         if clientLogin.GetField(fieldUserName).Data != nil {
 554                 c.UserName = clientLogin.GetField(fieldUserName).Data
 555         }
 556
 557         if clientLogin.GetField(fieldUserIconID).Data != nil {
 558                 *c.Icon = clientLogin.GetField(fieldUserIconID).Data
 559         }
 560
 561         c.Account = c.Server.Accounts[login]
 562
 563         if c.Authorize(accessDisconUser) {
 564                 *c.Flags = []byte{0, 2}
 565         }
 566
 567         s.Logger.Infow("Client connection received", "login", login, "version", *c.Version, "RemoteAddr", remoteAddr)
 568
 569         s.outbox <- c.NewReply(clientLogin,
 570                 NewField(fieldVersion, []byte{0x00, 0xbe}),
 571                 NewField(fieldCommunityBannerID, []byte{0x00, 0x01}),
 572                 NewField(fieldServerName, []byte(s.Config.Name)),
 573         )
 574
 575         // Send user access privs so client UI knows how to behave
 576         c.Server.outbox <- *NewTransaction(tranUserAccess, c.ID, NewField(fieldUserAccess, *c.Account.Access))
 577
 578         // Show agreement to client
 579         c.Server.outbox <- *NewTransaction(tranShowAgreement, c.ID, NewField(fieldData, s.Agreement))
 580
 581         // assume simplified hotline v1.2.3 login flow that does not require agreement
 582         if *c.Version == nil {
 583                 c.Agreed = true
 584
 585                 c.notifyOthers(
 586                         *NewTransaction(
 587                                 tranNotifyChangeUser, nil,
 588                                 NewField(fieldUserName, c.UserName),
 589                                 NewField(fieldUserID, *c.ID),
 590                                 NewField(fieldUserIconID, *c.Icon),
 591                                 NewField(fieldUserFlags, *c.Flags),
 592                         ),
 593                 )
 594         }
 595
 596         c.Server.Stats.LoginCount += 1
 597
 598         const readBuffSize = 1024000 // 1KB - TODO: what should this be?
 599         tranBuff := make([]byte, 0)
 600         tReadlen := 0
 601         // Infinite loop where take action on incoming client requests until the connection is closed
 602         for {
 603                 buf = make([]byte, readBuffSize)
 604                 tranBuff = tranBuff[tReadlen:]
 605
 606                 readLen, err := c.Connection.Read(buf)
 607                 if err != nil {
 608                         return err
 609                 }
 610                 tranBuff = append(tranBuff, buf[:readLen]...)
 611
 612                 // We may have read multiple requests worth of bytes from Connection.Read.  readTransactions splits them
 613                 // into a slice of transactions
 614                 var transactions []Transaction
 615                 if transactions, tReadlen, err = readTransactions(tranBuff); err != nil {
 616                         c.Server.Logger.Errorw("Error handling transaction", "err", err)
 617                 }
 618
 619                 // iterate over all of the transactions that were parsed from the byte slice and handle them
 620                 for _, t := range transactions {
 621                         if err := c.handleTransaction(&t); err != nil {
 622                                 c.Server.Logger.Errorw("Error handling transaction", "err", err)
 623                         }
 624                 }
 625         }
 626 }
 627
 628 // NewTransactionRef generates a random ID for the file transfer.  The Hotline client includes this ID
 629 // in the file transfer request payload, and the file transfer server will use it to map the request
 630 // to a transfer
 631 func (s *Server) NewTransactionRef() []byte {
 632         transactionRef := make([]byte, 4)
 633         rand.Read(transactionRef)
 634
 635         return transactionRef
 636 }
 637
 638 func (s *Server) NewPrivateChat(cc *ClientConn) []byte {
 639         s.mux.Lock()
 640         defer s.mux.Unlock()
 641
 642         randID := make([]byte, 4)
 643         rand.Read(randID)
 644         data := binary.BigEndian.Uint32(randID[:])
 645
 646         s.PrivateChats[data] = &PrivateChat{
 647                 Subject:    "",
 648                 ClientConn: make(map[uint16]*ClientConn),
 649         }
 650         s.PrivateChats[data].ClientConn[cc.uint16ID()] = cc
 651
 652         return randID
 653 }
 654
 655 const dlFldrActionSendFile = 1
 656 const dlFldrActionResumeFile = 2
 657 const dlFldrActionNextFile = 3
 658
 659 // handleFileTransfer receives a client net.Conn from the file transfer server, performs the requested transfer type, then closes the connection
 660 func (s *Server) handleFileTransfer(conn io.ReadWriteCloser) error {
 661         defer func() {
 662
 663                 if err := conn.Close(); err != nil {
 664                         s.Logger.Errorw("error closing connection", "error", err)
 665                 }
 666         }()
 667
 668         defer dontPanic(s.Logger)
 669
 670         txBuf := make([]byte, 16)
 671         if _, err := io.ReadFull(conn, txBuf); err != nil {
 672                 return err
 673         }
 674
 675         var t transfer
 676         if _, err := t.Write(txBuf); err != nil {
 677                 return err
 678         }
 679
 680         transferRefNum := binary.BigEndian.Uint32(t.ReferenceNumber[:])
 681         defer func() {
 682                 s.mux.Lock()
 683                 delete(s.FileTransfers, transferRefNum)
 684                 s.mux.Unlock()
 685         }()
 686
 687         s.mux.Lock()
 688         fileTransfer, ok := s.FileTransfers[transferRefNum]
 689         s.mux.Unlock()
 690         if !ok {
 691                 return errors.New("invalid transaction ID")
 692         }
 693
 694         switch fileTransfer.Type {
 695         case FileDownload:
 696                 fullFilePath, err := readPath(s.Config.FileRoot, fileTransfer.FilePath, fileTransfer.FileName)
 697                 if err != nil {
 698                         return err
 699                 }
 700
 701                 var dataOffset int64
 702                 if fileTransfer.fileResumeData != nil {
 703                         dataOffset = int64(binary.BigEndian.Uint32(fileTransfer.fileResumeData.ForkInfoList[0].DataSize[:]))
 704                 }
 705
 706                 ffo, err := NewFlattenedFileObject(s.Config.FileRoot, fileTransfer.FilePath, fileTransfer.FileName, dataOffset)
 707                 if err != nil {
 708                         return err
 709                 }
 710
 711                 s.Logger.Infow("File download started", "filePath", fullFilePath, "transactionRef", fileTransfer.ReferenceNumber)
 712
 713                 if fileTransfer.options == nil {
 714                         // Start by sending flat file object to client
 715                         if _, err := conn.Write(ffo.BinaryMarshal()); err != nil {
 716                                 return err
 717                         }
 718                 }
 719
 720                 file, err := FS.Open(fullFilePath)
 721                 if err != nil {
 722                         return err
 723                 }
 724
 725                 sendBuffer := make([]byte, 1048576)
 726                 var totalSent int64
 727                 for {
 728                         var bytesRead int
 729                         if bytesRead, err = file.ReadAt(sendBuffer, dataOffset+totalSent); err == io.EOF {
 730                                 if _, err := conn.Write(sendBuffer[:bytesRead]); err != nil {
 731                                         return err
 732                                 }
 733                                 break
 734                         }
 735                         if err != nil {
 736                                 return err
 737                         }
 738                         totalSent += int64(bytesRead)
 739
 740                         fileTransfer.BytesSent += bytesRead
 741
 742                         if _, err := conn.Write(sendBuffer[:bytesRead]); err != nil {
 743                                 return err
 744                         }
 745                 }
 746         case FileUpload:
 747                 destinationFile := s.Config.FileRoot + ReadFilePath(fileTransfer.FilePath) + "/" + string(fileTransfer.FileName)
 748
 749                 var file *os.File
 750
 751                 // A file upload has three possible cases:
 752                 // 1) Upload a new file
 753                 // 2) Resume a partially transferred file
 754                 // 3) Replace a fully uploaded file
 755                 // Unfortunately we have to infer which case applies by inspecting what is already on the file system
 756
 757                 // 1) Check for existing file:
 758                 _, err := os.Stat(destinationFile)
 759                 if err == nil {
 760                         // If found, that means this upload is intended to replace the file
 761                         if err = os.Remove(destinationFile); err != nil {
 762                                 return err
 763                         }
 764                         file, err = os.Create(destinationFile + incompleteFileSuffix)
 765                 }
 766                 if errors.Is(err, fs.ErrNotExist) {
 767                         // If not found, open or create a new incomplete file
 768                         file, err = os.OpenFile(destinationFile+incompleteFileSuffix, os.O_CREATE|os.O_APPEND|os.O_WRONLY, 0644)
 769                         if err != nil {
 770                                 return err
 771                         }
 772                 }
 773
 774                 defer func() { _ = file.Close() }()
 775
 776                 s.Logger.Infow("File upload started", "transactionRef", fileTransfer.ReferenceNumber, "dstFile", destinationFile)
 777
 778                 // TODO: replace io.Discard with a real file when ready to implement storing of resource fork data
 779                 if err := receiveFile(conn, file, io.Discard); err != nil {
 780                         return err
 781                 }
 782
 783                 if err := os.Rename(destinationFile+".incomplete", destinationFile); err != nil {
 784                         return err
 785                 }
 786
 787                 s.Logger.Infow("File upload complete", "transactionRef", fileTransfer.ReferenceNumber, "dstFile", destinationFile)
 788         case FolderDownload:
 789                 // Folder Download flow:
 790                 // 1. Get filePath from the transfer
 791                 // 2. Iterate over files
 792                 // 3. For each file:
 793                 //       Send file header to client
 794                 // The client can reply in 3 ways:
 795                 //
 796                 // 1. If type is an odd number (unknown type?), or file download for the current file is completed:
 797                 //              client sends []byte{0x00, 0x03} to tell the server to continue to the next file
 798                 //
 799                 // 2. If download of a file is to be resumed:
 800                 //              client sends:
 801                 //                      []byte{0x00, 0x02} // download folder action
 802                 //                      [2]byte // Resume data size
 803                 //                      []byte file resume data (see myField_FileResumeData)
 804                 //
 805                 // 3. Otherwise, download of the file is requested and client sends []byte{0x00, 0x01}
 806                 //
 807                 // When download is requested (case 2 or 3), server replies with:
 808                 //                      [4]byte - file size
 809                 //                      []byte  - Flattened File Object
 810                 //
 811                 // After every file download, client could request next file with:
 812                 //                      []byte{0x00, 0x03}
 813                 //
 814                 // This notifies the server to send the next item header
 815
 816                 fullFilePath, err := readPath(s.Config.FileRoot, fileTransfer.FilePath, fileTransfer.FileName)
 817                 if err != nil {
 818                         return err
 819                 }
 820
 821                 basePathLen := len(fullFilePath)
 822
 823                 s.Logger.Infow("Start folder download", "path", fullFilePath, "ReferenceNumber", fileTransfer.ReferenceNumber)
 824
 825                 nextAction := make([]byte, 2)
 826                 if _, err := io.ReadFull(conn, nextAction); err != nil {
 827                         return err
 828                 }
 829
 830                 i := 0
 831                 err = filepath.Walk(fullFilePath+"/", func(path string, info os.FileInfo, err error) error {
 832                         if err != nil {
 833                                 return err
 834                         }
 835                         i += 1
 836                         subPath := path[basePathLen+1:]
 837                         s.Logger.Infow("Sending fileheader", "i", i, "path", path, "fullFilePath", fullFilePath, "subPath", subPath, "IsDir", info.IsDir())
 838
 839                         if i == 1 {
 840                                 return nil
 841                         }
 842
 843                         fileHeader := NewFileHeader(subPath, info.IsDir())
 844
 845                         // Send the file header to client
 846                         if _, err := conn.Write(fileHeader.Payload()); err != nil {
 847                                 s.Logger.Errorf("error sending file header: %v", err)
 848                                 return err
 849                         }
 850
 851                         // Read the client's Next Action request
 852                         if _, err := io.ReadFull(conn, nextAction); err != nil {
 853                                 return err
 854                         }
 855
 856                         s.Logger.Infow("Client folder download action", "action", fmt.Sprintf("%X", nextAction[0:2]))
 857
 858                         var dataOffset int64
 859
 860                         switch nextAction[1] {
 861                         case dlFldrActionResumeFile:
 862                                 // client asked to resume this file
 863                                 var frd FileResumeData
 864                                 // get size of resumeData
 865                                 if _, err := io.ReadFull(conn, nextAction); err != nil {
 866                                         return err
 867                                 }
 868
 869                                 resumeDataLen := binary.BigEndian.Uint16(nextAction)
 870                                 resumeDataBytes := make([]byte, resumeDataLen)
 871                                 if _, err := io.ReadFull(conn, resumeDataBytes); err != nil {
 872                                         return err
 873                                 }
 874
 875                                 if err := frd.UnmarshalBinary(resumeDataBytes); err != nil {
 876                                         return err
 877                                 }
 878                                 dataOffset = int64(binary.BigEndian.Uint32(frd.ForkInfoList[0].DataSize[:]))
 879                         case dlFldrActionNextFile:
 880                                 // client asked to skip this file
 881                                 return nil
 882                         }
 883
 884                         if info.IsDir() {
 885                                 return nil
 886                         }
 887
 888                         splitPath := strings.Split(path, "/")
 889
 890                         ffo, err := NewFlattenedFileObject(strings.Join(splitPath[:len(splitPath)-1], "/"), nil, []byte(info.Name()), dataOffset)
 891                         if err != nil {
 892                                 return err
 893                         }
 894                         s.Logger.Infow("File download started",
 895                                 "fileName", info.Name(),
 896                                 "transactionRef", fileTransfer.ReferenceNumber,
 897                                 "TransferSize", fmt.Sprintf("%x", ffo.TransferSize()),
 898                         )
 899
 900                         // Send file size to client
 901                         if _, err := conn.Write(ffo.TransferSize()); err != nil {
 902                                 s.Logger.Error(err)
 903                                 return err
 904                         }
 905
 906                         // Send ffo bytes to client
 907                         if _, err := conn.Write(ffo.BinaryMarshal()); err != nil {
 908                                 s.Logger.Error(err)
 909                                 return err
 910                         }
 911
 912                         file, err := FS.Open(path)
 913                         if err != nil {
 914                                 return err
 915                         }
 916
 917                         // // Copy N bytes from file to connection
 918                         // _, err = io.CopyN(conn, file, int64(binary.BigEndian.Uint32(ffo.FlatFileDataForkHeader.DataSize[:])))
 919                         // if err != nil {
 920                         //      return err
 921                         // }
 922                         // file.Close()
 923                         sendBuffer := make([]byte, 1048576)
 924                         var totalSent int64
 925                         for {
 926                                 var bytesRead int
 927                                 if bytesRead, err = file.ReadAt(sendBuffer, dataOffset+totalSent); err == io.EOF {
 928                                         if _, err := conn.Write(sendBuffer[:bytesRead]); err != nil {
 929                                                 return err
 930                                         }
 931                                         break
 932                                 }
 933                                 if err != nil {
 934                                         panic(err)
 935                                 }
 936                                 totalSent += int64(bytesRead)
 937
 938                                 fileTransfer.BytesSent += bytesRead
 939
 940                                 if _, err := conn.Write(sendBuffer[:bytesRead]); err != nil {
 941                                         return err
 942                                 }
 943                         }
 944
 945                         // TODO: optionally send resource fork header and resource fork data
 946
 947                         // Read the client's Next Action request.  This is always 3, I think?
 948                         if _, err := io.ReadFull(conn, nextAction); err != nil {
 949                                 return err
 950                         }
 951
 952                         return nil
 953                 })
 954
 955         case FolderUpload:
 956                 dstPath, err := readPath(s.Config.FileRoot, fileTransfer.FilePath, fileTransfer.FileName)
 957                 if err != nil {
 958                         return err
 959                 }
 960                 s.Logger.Infow(
 961                         "Folder upload started",
 962                         "transactionRef", fileTransfer.ReferenceNumber,
 963                         "dstPath", dstPath,
 964                         "TransferSize", fmt.Sprintf("%x", fileTransfer.TransferSize),
 965                         "FolderItemCount", fileTransfer.FolderItemCount,
 966                 )
 967
 968                 // Check if the target folder exists.  If not, create it.
 969                 if _, err := FS.Stat(dstPath); os.IsNotExist(err) {
 970                         if err := FS.Mkdir(dstPath, 0777); err != nil {
 971                                 return err
 972                         }
 973                 }
 974
 975                 // Begin the folder upload flow by sending the "next file action" to client
 976                 if _, err := conn.Write([]byte{0, dlFldrActionNextFile}); err != nil {
 977                         return err
 978                 }
 979
 980                 fileSize := make([]byte, 4)
 981                 readBuffer := make([]byte, 1024)
 982
 983                 for i := 0; i < fileTransfer.ItemCount(); i++ {
 984                         // TODO: fix potential short read with io.ReadFull
 985                         _, err := conn.Read(readBuffer)
 986                         if err != nil {
 987                                 return err
 988                         }
 989                         fu := readFolderUpload(readBuffer)
 990
 991                         s.Logger.Infow(
 992                                 "Folder upload continued",
 993                                 "transactionRef", fmt.Sprintf("%x", fileTransfer.ReferenceNumber),
 994                                 "FormattedPath", fu.FormattedPath(),
 995                                 "IsFolder", fmt.Sprintf("%x", fu.IsFolder),
 996                                 "PathItemCount", binary.BigEndian.Uint16(fu.PathItemCount[:]),
 997                         )
 998
 999                         if fu.IsFolder == [2]byte{0, 1} {
1000                                 if _, err := os.Stat(dstPath + "/" + fu.FormattedPath()); os.IsNotExist(err) {
1001                                         if err := os.Mkdir(dstPath+"/"+fu.FormattedPath(), 0777); err != nil {
1002                                                 return err
1003                                         }
1004                                 }
1005
1006                                 // Tell client to send next file
1007                                 if _, err := conn.Write([]byte{0, dlFldrActionNextFile}); err != nil {
1008                                         return err
1009                                 }
1010                         } else {
1011                                 nextAction := dlFldrActionSendFile
1012
1013                                 // Check if we have the full file already.  If so, send dlFldrAction_NextFile to client to skip.
1014                                 _, err := os.Stat(dstPath + "/" + fu.FormattedPath())
1015                                 if err != nil && !errors.Is(err, fs.ErrNotExist) {
1016                                         return err
1017                                 }
1018                                 if err == nil {
1019                                         nextAction = dlFldrActionNextFile
1020                                 }
1021
1022                                 //  Check if we have a partial file already.  If so, send dlFldrAction_ResumeFile to client to resume upload.
1023                                 inccompleteFile, err := os.Stat(dstPath + "/" + fu.FormattedPath() + incompleteFileSuffix)
1024                                 if err != nil && !errors.Is(err, fs.ErrNotExist) {
1025                                         return err
1026                                 }
1027                                 if err == nil {
1028                                         nextAction = dlFldrActionResumeFile
1029                                 }
1030
1031                                 fmt.Printf("Next Action: %v\n", nextAction)
1032
1033                                 if _, err := conn.Write([]byte{0, uint8(nextAction)}); err != nil {
1034                                         return err
1035                                 }
1036
1037                                 switch nextAction {
1038                                 case dlFldrActionNextFile:
1039                                         continue
1040                                 case dlFldrActionResumeFile:
1041                                         offset := make([]byte, 4)
1042                                         binary.BigEndian.PutUint32(offset, uint32(inccompleteFile.Size()))
1043
1044                                         file, err := os.OpenFile(dstPath+"/"+fu.FormattedPath()+incompleteFileSuffix, os.O_APPEND|os.O_CREATE|os.O_WRONLY, 0644)
1045                                         if err != nil {
1046                                                 return err
1047                                         }
1048
1049                                         fileResumeData := NewFileResumeData([]ForkInfoList{
1050                                                 *NewForkInfoList(offset),
1051                                         })
1052
1053                                         b, _ := fileResumeData.BinaryMarshal()
1054
1055                                         bs := make([]byte, 2)
1056                                         binary.BigEndian.PutUint16(bs, uint16(len(b)))
1057
1058                                         if _, err := conn.Write(append(bs, b...)); err != nil {
1059                                                 return err
1060                                         }
1061
1062                                         if _, err := io.ReadFull(conn, fileSize); err != nil {
1063                                                 return err
1064                                         }
1065
1066                                         if err := receiveFile(conn, file, ioutil.Discard); err != nil {
1067                                                 s.Logger.Error(err)
1068                                         }
1069
1070                                         err = os.Rename(dstPath+"/"+fu.FormattedPath()+".incomplete", dstPath+"/"+fu.FormattedPath())
1071                                         if err != nil {
1072                                                 return err
1073                                         }
1074
1075                                 case dlFldrActionSendFile:
1076                                         if _, err := conn.Read(fileSize); err != nil {
1077                                                 return err
1078                                         }
1079
1080                                         filePath := dstPath + "/" + fu.FormattedPath()
1081                                         s.Logger.Infow("Starting file transfer", "path", filePath, "fileNum", i+1, "totalFiles", "zz", "fileSize", binary.BigEndian.Uint32(fileSize))
1082
1083                                         newFile, err := FS.Create(filePath + ".incomplete")
1084                                         if err != nil {
1085                                                 return err
1086                                         }
1087
1088                                         if err := receiveFile(conn, newFile, ioutil.Discard); err != nil {
1089                                                 s.Logger.Error(err)
1090                                         }
1091                                         _ = newFile.Close()
1092                                         if err := os.Rename(filePath+".incomplete", filePath); err != nil {
1093                                                 return err
1094                                         }
1095                                 }
1096
1097                                 // Tell client to send next file
1098                                 if _, err := conn.Write([]byte{0, dlFldrActionNextFile}); err != nil {
1099                                         return err
1100                                 }
1101                         }
1102                 }
1103                 s.Logger.Infof("Folder upload complete")
1104         }
1105
1106         return nil
1107 }
1108
1109 // sortedClients is a utility function that takes a map of *ClientConn and returns a sorted slice of the values.
1110 // The purpose of this is to ensure that the ordering of client connections is deterministic so that test assertions work.
1111 func sortedClients(unsortedClients map[uint16]*ClientConn) (clients []*ClientConn) {
1112         for _, c := range unsortedClients {
1113                 clients = append(clients, c)
1114         }
1115         sort.Sort(byClientID(clients))
1116         return clients
1117 }