networking/tftp.c

   1 /* vi: set sw=4 ts=4: */
   2 /*
   3  * A simple tftp client/server for busybox.
   4  * Tries to follow RFC1350.
   5  * Only "octet" mode supported.
   6  * Optional blocksize negotiation (RFC2347 + RFC2348)
   7  *
   8  * Copyright (C) 2001 Magnus Damm <damm@opensource.se>
   9  *
  10  * Parts of the code based on:
  11  *
  12  * atftp:  Copyright (C) 2000 Jean-Pierre Lefebvre <helix@step.polymtl.ca>
  13  *                        and Remi Lefebvre <remi@debian.org>
  14  *
  15  * utftp:  Copyright (C) 1999 Uwe Ohse <uwe@ohse.de>
  16  *
  17  * tftpd added by Denys Vlasenko & Vladimir Dronnikov
  18  *
  19  * Licensed under GPLv2 or later, see file LICENSE in this source tree.
  20  */
  21
  22 //usage:#define tftp_trivial_usage
  23 //usage:       "[OPTIONS] HOST [PORT]"
  24 //usage:#define tftp_full_usage "\n\n"
  25 //usage:       "Transfer a file from/to tftp server\n"
  26 //usage:     "\n        -l FILE Local FILE"
  27 //usage:     "\n        -r FILE Remote FILE"
  28 //usage:        IF_FEATURE_TFTP_GET(
  29 //usage:     "\n        -g      Get file"
  30 //usage:        )
  31 //usage:        IF_FEATURE_TFTP_PUT(
  32 //usage:     "\n        -p      Put file"
  33 //usage:        )
  34 //usage:        IF_FEATURE_TFTP_BLOCKSIZE(
  35 //usage:     "\n        -b SIZE Transfer blocks of SIZE octets"
  36 //usage:        )
  37 //usage:
  38 //usage:#define tftpd_trivial_usage
  39 //usage:       "[-cr] [-u USER] [DIR]"
  40 //usage:#define tftpd_full_usage "\n\n"
  41 //usage:       "Transfer a file on tftp client's request\n"
  42 //usage:       "\n"
  43 //usage:       "tftpd should be used as an inetd service.\n"
  44 //usage:       "tftpd's line for inetd.conf:\n"
  45 //usage:       "        69 dgram udp nowait root tftpd tftpd -l /files/to/serve\n"
  46 //usage:       "It also can be ran from udpsvd:\n"
  47 //usage:       "        udpsvd -vE 0.0.0.0 69 tftpd /files/to/serve\n"
  48 //usage:     "\n        -r      Prohibit upload"
  49 //usage:     "\n        -c      Allow file creation via upload"
  50 //usage:     "\n        -u      Access files as USER"
  51 //usage:     "\n        -l      Log to syslog (inetd mode requires this)"
  52
  53 #include "libbb.h"
  54 #include "common_bufsiz.h"
  55 #include <syslog.h>
  56
  57 #if ENABLE_FEATURE_TFTP_GET || ENABLE_FEATURE_TFTP_PUT
  58
  59 #define TFTP_BLKSIZE_DEFAULT       512  /* according to RFC 1350, don't change */
  60 #define TFTP_BLKSIZE_DEFAULT_STR "512"
  61 /* Was 50 ms but users asked to bump it up a bit */
  62 #define TFTP_TIMEOUT_MS            100
  63 #define TFTP_MAXTIMEOUT_MS        2000
  64 #define TFTP_NUM_RETRIES            12  /* number of backed-off retries */
  65
  66 /* opcodes we support */
  67 #define TFTP_RRQ   1
  68 #define TFTP_WRQ   2
  69 #define TFTP_DATA  3
  70 #define TFTP_ACK   4
  71 #define TFTP_ERROR 5
  72 #define TFTP_OACK  6
  73
  74 /* error codes sent over network (we use only 0, 1, 3 and 8) */
  75 /* generic (error message is included in the packet) */
  76 #define ERR_UNSPEC   0
  77 #define ERR_NOFILE   1
  78 #define ERR_ACCESS   2
  79 /* disk full or allocation exceeded */
  80 #define ERR_WRITE    3
  81 #define ERR_OP       4
  82 #define ERR_BAD_ID   5
  83 #define ERR_EXIST    6
  84 #define ERR_BAD_USER 7
  85 #define ERR_BAD_OPT  8
  86
  87 /* masks coming from getopt32 */
  88 enum {
  89         TFTP_OPT_GET = (1 << 0),
  90         TFTP_OPT_PUT = (1 << 1),
  91         /* pseudo option: if set, it's tftpd */
  92         TFTPD_OPT = (1 << 7) * ENABLE_TFTPD,
  93         TFTPD_OPT_r = (1 << 8) * ENABLE_TFTPD,
  94         TFTPD_OPT_c = (1 << 9) * ENABLE_TFTPD,
  95         TFTPD_OPT_u = (1 << 10) * ENABLE_TFTPD,
  96         TFTPD_OPT_l = (1 << 11) * ENABLE_TFTPD,
  97 };
  98
  99 #if ENABLE_FEATURE_TFTP_GET && !ENABLE_FEATURE_TFTP_PUT
 100 #define IF_GETPUT(...)
 101 #define CMD_GET(cmd) 1
 102 #define CMD_PUT(cmd) 0
 103 #elif !ENABLE_FEATURE_TFTP_GET && ENABLE_FEATURE_TFTP_PUT
 104 #define IF_GETPUT(...)
 105 #define CMD_GET(cmd) 0
 106 #define CMD_PUT(cmd) 1
 107 #else
 108 #define IF_GETPUT(...) __VA_ARGS__
 109 #define CMD_GET(cmd) ((cmd) & TFTP_OPT_GET)
 110 #define CMD_PUT(cmd) ((cmd) & TFTP_OPT_PUT)
 111 #endif
 112 /* NB: in the code below
 113  * CMD_GET(cmd) and CMD_PUT(cmd) are mutually exclusive
 114  */
 115
 116
 117 struct globals {
 118         /* u16 TFTP_ERROR; u16 reason; both network-endian, then error text: */
 119         uint8_t error_pkt[4 + 32];
 120         struct passwd *pw;
 121         /* Used in tftpd_main() for initial packet */
 122         /* Some HP PA-RISC firmware always sends fixed 516-byte requests */
 123         char block_buf[516];
 124         char block_buf_tail[1];
 125 #if ENABLE_FEATURE_TFTP_PROGRESS_BAR
 126         off_t pos;
 127         off_t size;
 128         const char *file;
 129         bb_progress_t pmt;
 130 #endif
 131 } FIX_ALIASING;
 132 #define G (*(struct globals*)bb_common_bufsiz1)
 133 #define INIT_G() do { \
 134         BUILD_BUG_ON(sizeof(G) > COMMON_BUFSIZE); \
 135 } while (0)
 136
 137 #define G_error_pkt_reason (G.error_pkt[3])
 138 #define G_error_pkt_str    ((char*)(G.error_pkt + 4))
 139
 140 #if ENABLE_FEATURE_TFTP_PROGRESS_BAR
 141 static void tftp_progress_update(void)
 142 {
 143         bb_progress_update(&G.pmt, 0, G.pos, G.size);
 144 }
 145 static void tftp_progress_init(void)
 146 {
 147         bb_progress_init(&G.pmt, G.file);
 148         tftp_progress_update();
 149 }
 150 static void tftp_progress_done(void)
 151 {
 152         if (is_bb_progress_inited(&G.pmt)) {
 153                 tftp_progress_update();
 154                 bb_putchar_stderr('\n');
 155                 bb_progress_free(&G.pmt);
 156         }
 157 }
 158 #else
 159 # define tftp_progress_init() ((void)0)
 160 # define tftp_progress_done() ((void)0)
 161 #endif
 162
 163 #if ENABLE_FEATURE_TFTP_BLOCKSIZE
 164
 165 static int tftp_blksize_check(const char *blksize_str, int maxsize)
 166 {
 167         /* Check if the blksize is valid:
 168          * RFC2348 says between 8 and 65464,
 169          * but our implementation makes it impossible
 170          * to use blksizes smaller than 22 octets. */
 171         unsigned blksize = bb_strtou(blksize_str, NULL, 10);
 172         if (errno
 173          || (blksize < 24) || (blksize > maxsize)
 174         ) {
 175                 bb_error_msg("bad blocksize '%s'", blksize_str);
 176                 return -1;
 177         }
 178 # if ENABLE_TFTP_DEBUG
 179         bb_error_msg("using blksize %u", blksize);
 180 # endif
 181         return blksize;
 182 }
 183
 184 static char *tftp_get_option(const char *option, char *buf, int len)
 185 {
 186         int opt_val = 0;
 187         int opt_found = 0;
 188         int k;
 189
 190         /* buf points to:
 191          * "opt_name<NUL>opt_val<NUL>opt_name2<NUL>opt_val2<NUL>..." */
 192
 193         while (len > 0) {
 194                 /* Make sure options are terminated correctly */
 195                 for (k = 0; k < len; k++) {
 196                         if (buf[k] == '\0') {
 197                                 goto nul_found;
 198                         }
 199                 }
 200                 return NULL;
 201  nul_found:
 202                 if (opt_val == 0) { /* it's "name" part */
 203                         if (strcasecmp(buf, option) == 0) {
 204                                 opt_found = 1;
 205                         }
 206                 } else if (opt_found) {
 207                         return buf;
 208                 }
 209
 210                 k++;
 211                 buf += k;
 212                 len -= k;
 213                 opt_val ^= 1;
 214         }
 215
 216         return NULL;
 217 }
 218
 219 #endif
 220
 221 static int tftp_protocol(
 222                 /* NULL if tftp, !NULL if tftpd: */
 223                 len_and_sockaddr *our_lsa,
 224                 len_and_sockaddr *peer_lsa,
 225                 const char *local_file
 226                 IF_TFTP(, const char *remote_file)
 227 #if !ENABLE_TFTP
 228 # define remote_file NULL
 229 #endif
 230                 /* 1 for tftp; 1/0 for tftpd depending whether client asked about it: */
 231                 IF_FEATURE_TFTP_BLOCKSIZE(, int want_transfer_size)
 232                 IF_FEATURE_TFTP_BLOCKSIZE(, int blksize))
 233 {
 234 #if !ENABLE_FEATURE_TFTP_BLOCKSIZE
 235         enum { blksize = TFTP_BLKSIZE_DEFAULT };
 236 #endif
 237
 238         struct pollfd pfd[1];
 239 #define socket_fd (pfd[0].fd)
 240         int len;
 241         int send_len;
 242         IF_FEATURE_TFTP_BLOCKSIZE(smallint expect_OACK = 0;)
 243         smallint finished = 0;
 244         uint16_t opcode;
 245         uint16_t block_nr;
 246         uint16_t recv_blk;
 247         int open_mode, local_fd;
 248         int retries, waittime_ms;
 249         int io_bufsize = blksize + 4;
 250         char *cp;
 251         /* Can't use RESERVE_CONFIG_BUFFER here since the allocation
 252          * size varies meaning BUFFERS_GO_ON_STACK would fail.
 253          *
 254          * We must keep the transmit and receive buffers separate
 255          * in case we rcv a garbage pkt - we need to rexmit the last pkt.
 256          */
 257         char *xbuf = xmalloc(io_bufsize);
 258         char *rbuf = xmalloc(io_bufsize);
 259
 260         socket_fd = xsocket(peer_lsa->u.sa.sa_family, SOCK_DGRAM, 0);
 261         setsockopt_reuseaddr(socket_fd);
 262
 263         if (!ENABLE_TFTP || our_lsa) { /* tftpd */
 264                 /* Create a socket which is:
 265                  * 1. bound to IP:port peer sent 1st datagram to,
 266                  * 2. connected to peer's IP:port
 267                  * This way we will answer from the IP:port peer
 268                  * expects, will not get any other packets on
 269                  * the socket, and also plain read/write will work. */
 270                 xbind(socket_fd, &our_lsa->u.sa, our_lsa->len);
 271                 xconnect(socket_fd, &peer_lsa->u.sa, peer_lsa->len);
 272
 273                 /* Is there an error already? Send pkt and bail out */
 274                 if (G_error_pkt_reason || G_error_pkt_str[0])
 275                         goto send_err_pkt;
 276
 277                 if (G.pw) {
 278                         change_identity(G.pw); /* initgroups, setgid, setuid */
 279                 }
 280         }
 281
 282         /* Prepare open mode */
 283         if (CMD_PUT(option_mask32)) {
 284                 open_mode = O_RDONLY;
 285         } else {
 286                 open_mode = O_WRONLY | O_TRUNC | O_CREAT;
 287 #if ENABLE_TFTPD
 288                 if ((option_mask32 & (TFTPD_OPT+TFTPD_OPT_c)) == TFTPD_OPT) {
 289                         /* tftpd without -c */
 290                         open_mode = O_WRONLY | O_TRUNC;
 291                 }
 292 #endif
 293         }
 294
 295         /* Examples of network traffic.
 296          * Note two cases when ACKs with block# of 0 are sent.
 297          *
 298          * Download without options:
 299          * tftp -> "\0\1FILENAME\0octet\0"
 300          *         "\0\3\0\1FILEDATA..." <- tftpd
 301          * tftp -> "\0\4\0\1"
 302          * ...
 303          * Download with option of blksize 16384:
 304          * tftp -> "\0\1FILENAME\0octet\0blksize\00016384\0"
 305          *         "\0\6blksize\00016384\0" <- tftpd
 306          * tftp -> "\0\4\0\0"
 307          *         "\0\3\0\1FILEDATA..." <- tftpd
 308          * tftp -> "\0\4\0\1"
 309          * ...
 310          * Upload without options:
 311          * tftp -> "\0\2FILENAME\0octet\0"
 312          *         "\0\4\0\0" <- tftpd
 313          * tftp -> "\0\3\0\1FILEDATA..."
 314          *         "\0\4\0\1" <- tftpd
 315          * ...
 316          * Upload with option of blksize 16384:
 317          * tftp -> "\0\2FILENAME\0octet\0blksize\00016384\0"
 318          *         "\0\6blksize\00016384\0" <- tftpd
 319          * tftp -> "\0\3\0\1FILEDATA..."
 320          *         "\0\4\0\1" <- tftpd
 321          * ...
 322          */
 323         block_nr = 1;
 324         cp = xbuf + 2;
 325
 326         if (!ENABLE_TFTP || our_lsa) { /* tftpd */
 327                 /* Open file (must be after changing user) */
 328                 local_fd = open(local_file, open_mode, 0666);
 329                 if (local_fd < 0) {
 330                         G_error_pkt_reason = ERR_NOFILE;
 331                         strcpy(G_error_pkt_str, "can't open file");
 332                         goto send_err_pkt;
 333                 }
 334 /* gcc 4.3.1 would NOT optimize it out as it should! */
 335 #if ENABLE_FEATURE_TFTP_BLOCKSIZE
 336                 if (blksize != TFTP_BLKSIZE_DEFAULT || want_transfer_size) {
 337                         /* Create and send OACK packet. */
 338                         /* For the download case, block_nr is still 1 -
 339                          * we expect 1st ACK from peer to be for (block_nr-1),
 340                          * that is, for "block 0" which is our OACK pkt */
 341                         opcode = TFTP_OACK;
 342                         goto add_blksize_opt;
 343                 }
 344 #endif
 345                 if (CMD_GET(option_mask32)) {
 346                         /* It's upload and we don't send OACK.
 347                          * We must ACK 1st packet (with filename)
 348                          * as if it is "block 0" */
 349                         block_nr = 0;
 350                 }
 351         } else { /* tftp */
 352                 /* Open file (must be after changing user) */
 353                 local_fd = CMD_GET(option_mask32) ? STDOUT_FILENO : STDIN_FILENO;
 354                 if (NOT_LONE_DASH(local_file))
 355                         local_fd = xopen(local_file, open_mode);
 356 /* Removing #if, or using if() statement instead of #if may lead to
 357  * "warning: null argument where non-null required": */
 358 #if ENABLE_TFTP
 359                 /* tftp */
 360
 361                 /* We can't (and don't really need to) bind the socket:
 362                  * we don't know from which local IP datagrams will be sent,
 363                  * but kernel will pick the same IP every time (unless routing
 364                  * table is changed), thus peer will see dgrams consistently
 365                  * coming from the same IP.
 366                  * We would like to connect the socket, but since peer's
 367                  * UDP code can be less perfect than ours, _peer's_ IP:port
 368                  * in replies may differ from IP:port we used to send
 369                  * our first packet. We can connect() only when we get
 370                  * first reply. */
 371
 372                 /* build opcode */
 373                 opcode = TFTP_WRQ;
 374                 if (CMD_GET(option_mask32)) {
 375                         opcode = TFTP_RRQ;
 376                 }
 377                 /* add filename and mode */
 378                 /* fill in packet if the filename fits into xbuf */
 379                 len = strlen(remote_file) + 1;
 380                 if (2 + len + sizeof("octet") >= io_bufsize) {
 381                         bb_error_msg("remote filename is too long");
 382                         goto ret;
 383                 }
 384                 strcpy(cp, remote_file);
 385                 cp += len;
 386                 /* add "mode" part of the packet */
 387                 strcpy(cp, "octet");
 388                 cp += sizeof("octet");
 389
 390 # if ENABLE_FEATURE_TFTP_BLOCKSIZE
 391                 if (blksize == TFTP_BLKSIZE_DEFAULT && !want_transfer_size)
 392                         goto send_pkt;
 393
 394                 /* Need to add option to pkt */
 395                 if ((&xbuf[io_bufsize - 1] - cp) < sizeof("blksize NNNNN tsize ") + sizeof(off_t)*3) {
 396                         bb_error_msg("remote filename is too long");
 397                         goto ret;
 398                 }
 399                 expect_OACK = 1;
 400 # endif
 401 #endif /* ENABLE_TFTP */
 402
 403 #if ENABLE_FEATURE_TFTP_BLOCKSIZE
 404  add_blksize_opt:
 405                 if (blksize != TFTP_BLKSIZE_DEFAULT) {
 406                         /* add "blksize", <nul>, blksize, <nul> */
 407                         strcpy(cp, "blksize");
 408                         cp += sizeof("blksize");
 409                         cp += snprintf(cp, 6, "%d", blksize) + 1;
 410                 }
 411                 if (want_transfer_size) {
 412                         /* add "tsize", <nul>, size, <nul> (see RFC2349) */
 413                         /* if tftp and downloading, we send "0" (since we opened local_fd with O_TRUNC)
 414                          * and this makes server to send "tsize" option with the size */
 415                         /* if tftp and uploading, we send file size (maybe dont, to not confuse old servers???) */
 416                         /* if tftpd and downloading, we are answering to client's request */
 417                         /* if tftpd and uploading: !want_transfer_size, this code is not executed */
 418                         struct stat st;
 419                         strcpy(cp, "tsize");
 420                         cp += sizeof("tsize");
 421                         st.st_size = 0;
 422                         fstat(local_fd, &st);
 423                         cp += sprintf(cp, "%"OFF_FMT"u", (off_t)st.st_size) + 1;
 424 # if ENABLE_FEATURE_TFTP_PROGRESS_BAR
 425                         /* Save for progress bar. If 0 (tftp downloading),
 426                          * we look at server's reply later */
 427                         G.size = st.st_size;
 428                         if (remote_file && st.st_size)
 429                                 tftp_progress_init();
 430 # endif
 431                 }
 432 #endif
 433                 /* First packet is built, so skip packet generation */
 434                 goto send_pkt;
 435         }
 436
 437         /* Using mostly goto's - continue/break will be less clear
 438          * in where we actually jump to */
 439         while (1) {
 440                 /* Build ACK or DATA */
 441                 cp = xbuf + 2;
 442                 *((uint16_t*)cp) = htons(block_nr);
 443                 cp += 2;
 444                 block_nr++;
 445                 opcode = TFTP_ACK;
 446                 if (CMD_PUT(option_mask32)) {
 447                         opcode = TFTP_DATA;
 448                         len = full_read(local_fd, cp, blksize);
 449                         if (len < 0) {
 450                                 goto send_read_err_pkt;
 451                         }
 452                         if (len != blksize) {
 453                                 finished = 1;
 454                         }
 455                         cp += len;
 456                         IF_FEATURE_TFTP_PROGRESS_BAR(G.pos += len;)
 457                 }
 458  send_pkt:
 459                 /* Send packet */
 460                 *((uint16_t*)xbuf) = htons(opcode); /* fill in opcode part */
 461                 send_len = cp - xbuf;
 462                 /* NB: send_len value is preserved in code below
 463                  * for potential resend */
 464
 465                 retries = TFTP_NUM_RETRIES;  /* re-initialize */
 466                 waittime_ms = TFTP_TIMEOUT_MS;
 467
 468  send_again:
 469 #if ENABLE_TFTP_DEBUG
 470                 fprintf(stderr, "sending %u bytes\n", send_len);
 471                 for (cp = xbuf; cp < &xbuf[send_len]; cp++)
 472                         fprintf(stderr, "%02x ", (unsigned char) *cp);
 473                 fprintf(stderr, "\n");
 474 #endif
 475                 xsendto(socket_fd, xbuf, send_len, &peer_lsa->u.sa, peer_lsa->len);
 476
 477 #if ENABLE_FEATURE_TFTP_PROGRESS_BAR
 478                 if (is_bb_progress_inited(&G.pmt))
 479                         tftp_progress_update();
 480 #endif
 481                 /* Was it final ACK? then exit */
 482                 if (finished && (opcode == TFTP_ACK))
 483                         goto ret;
 484
 485  recv_again:
 486                 /* Receive packet */
 487                 /*pfd[0].fd = socket_fd;*/
 488                 pfd[0].events = POLLIN;
 489                 switch (safe_poll(pfd, 1, waittime_ms)) {
 490                 default:
 491                         /*bb_perror_msg("poll"); - done in safe_poll */
 492                         goto ret;
 493                 case 0:
 494                         retries--;
 495                         if (retries == 0) {
 496                                 tftp_progress_done();
 497                                 bb_error_msg("timeout");
 498                                 goto ret; /* no err packet sent */
 499                         }
 500
 501                         /* exponential backoff with limit */
 502                         waittime_ms += waittime_ms/2;
 503                         if (waittime_ms > TFTP_MAXTIMEOUT_MS) {
 504                                 waittime_ms = TFTP_MAXTIMEOUT_MS;
 505                         }
 506
 507                         goto send_again; /* resend last sent pkt */
 508                 case 1:
 509                         if (!our_lsa) {
 510                                 /* tftp (not tftpd!) receiving 1st packet */
 511                                 our_lsa = ((void*)(ptrdiff_t)-1); /* not NULL */
 512                                 len = recvfrom(socket_fd, rbuf, io_bufsize, 0,
 513                                                 &peer_lsa->u.sa, &peer_lsa->len);
 514                                 /* Our first dgram went to port 69
 515                                  * but reply may come from different one.
 516                                  * Remember and use this new port (and IP) */
 517                                 if (len >= 0)
 518                                         xconnect(socket_fd, &peer_lsa->u.sa, peer_lsa->len);
 519                         } else {
 520                                 /* tftpd, or not the very first packet:
 521                                  * socket is connect()ed, can just read from it. */
 522                                 /* Don't full_read()!
 523                                  * This is not TCP, one read == one pkt! */
 524                                 len = safe_read(socket_fd, rbuf, io_bufsize);
 525                         }
 526                         if (len < 0) {
 527                                 goto send_read_err_pkt;
 528                         }
 529                         if (len < 4) { /* too small? */
 530                                 goto recv_again;
 531                         }
 532                 }
 533
 534                 /* Process recv'ed packet */
 535                 opcode = ntohs( ((uint16_t*)rbuf)[0] );
 536                 recv_blk = ntohs( ((uint16_t*)rbuf)[1] );
 537 #if ENABLE_TFTP_DEBUG
 538                 fprintf(stderr, "received %d bytes: %04x %04x\n", len, opcode, recv_blk);
 539 #endif
 540                 if (opcode == TFTP_ERROR) {
 541                         static const char errcode_str[] ALIGN1 =
 542                                 "\0"
 543                                 "file not found\0"
 544                                 "access violation\0"
 545                                 "disk full\0"
 546                                 "bad operation\0"
 547                                 "unknown transfer id\0"
 548                                 "file already exists\0"
 549                                 "no such user\0"
 550                                 "bad option";
 551
 552                         const char *msg = "";
 553
 554                         if (len > 4 && rbuf[4] != '\0') {
 555                                 msg = &rbuf[4];
 556                                 rbuf[io_bufsize - 1] = '\0'; /* paranoia */
 557                         } else if (recv_blk <= 8) {
 558                                 msg = nth_string(errcode_str, recv_blk);
 559                         }
 560                         bb_error_msg("server error: (%u) %s", recv_blk, msg);
 561                         goto ret;
 562                 }
 563
 564 #if ENABLE_FEATURE_TFTP_BLOCKSIZE
 565                 if (expect_OACK) {
 566                         expect_OACK = 0;
 567                         if (opcode == TFTP_OACK) {
 568                                 /* server seems to support options */
 569                                 char *res;
 570
 571                                 res = tftp_get_option("blksize", &rbuf[2], len - 2);
 572                                 if (res) {
 573                                         blksize = tftp_blksize_check(res, blksize);
 574                                         if (blksize < 0) {
 575                                                 G_error_pkt_reason = ERR_BAD_OPT;
 576                                                 goto send_err_pkt;
 577                                         }
 578                                         io_bufsize = blksize + 4;
 579                                 }
 580 # if ENABLE_FEATURE_TFTP_PROGRESS_BAR
 581                                 if (remote_file && G.size == 0) { /* if we don't know it yet */
 582                                         res = tftp_get_option("tsize", &rbuf[2], len - 2);
 583                                         if (res) {
 584                                                 G.size = bb_strtoull(res, NULL, 10);
 585                                                 if (G.size)
 586                                                         tftp_progress_init();
 587                                         }
 588                                 }
 589 # endif
 590                                 if (CMD_GET(option_mask32)) {
 591                                         /* We'll send ACK for OACK,
 592                                          * such ACK has "block no" of 0 */
 593                                         block_nr = 0;
 594                                 }
 595                                 continue;
 596                         }
 597                         /* rfc2347:
 598                          * "An option not acknowledged by the server
 599                          * must be ignored by the client and server
 600                          * as if it were never requested." */
 601                         if (blksize != TFTP_BLKSIZE_DEFAULT)
 602                                 bb_error_msg("falling back to blocksize "TFTP_BLKSIZE_DEFAULT_STR);
 603                         blksize = TFTP_BLKSIZE_DEFAULT;
 604                         io_bufsize = TFTP_BLKSIZE_DEFAULT + 4;
 605                 }
 606 #endif
 607                 /* block_nr is already advanced to next block# we expect
 608                  * to get / block# we are about to send next time */
 609
 610                 if (CMD_GET(option_mask32) && (opcode == TFTP_DATA)) {
 611                         if (recv_blk == block_nr) {
 612                                 int sz = full_write(local_fd, &rbuf[4], len - 4);
 613                                 if (sz != len - 4) {
 614                                         strcpy(G_error_pkt_str, bb_msg_write_error);
 615                                         G_error_pkt_reason = ERR_WRITE;
 616                                         goto send_err_pkt;
 617                                 }
 618                                 if (sz != blksize) {
 619                                         finished = 1;
 620                                 }
 621                                 IF_FEATURE_TFTP_PROGRESS_BAR(G.pos += sz;)
 622                                 continue; /* send ACK */
 623                         }
 624 /* Disabled to cope with servers with Sorcerer's Apprentice Syndrome */
 625 #if 0
 626                         if (recv_blk == (block_nr - 1)) {
 627                                 /* Server lost our TFTP_ACK.  Resend it */
 628                                 block_nr = recv_blk;
 629                                 continue;
 630                         }
 631 #endif
 632                 }
 633
 634                 if (CMD_PUT(option_mask32) && (opcode == TFTP_ACK)) {
 635                         /* did peer ACK our last DATA pkt? */
 636                         if (recv_blk == (uint16_t) (block_nr - 1)) {
 637                                 if (finished)
 638                                         goto ret;
 639                                 continue; /* send next block */
 640                         }
 641                 }
 642                 /* Awww... recv'd packet is not recognized! */
 643                 goto recv_again;
 644                 /* why recv_again? - rfc1123 says:
 645                  * "The sender (i.e., the side originating the DATA packets)
 646                  *  must never resend the current DATA packet on receipt
 647                  *  of a duplicate ACK".
 648                  * DATA pkts are resent ONLY on timeout.
 649                  * Thus "goto send_again" will ba a bad mistake above.
 650                  * See:
 651                  * http://en.wikipedia.org/wiki/Sorcerer's_Apprentice_Syndrome
 652                  */
 653         } /* end of "while (1)" */
 654  ret:
 655         if (ENABLE_FEATURE_CLEAN_UP) {
 656                 close(local_fd);
 657                 close(socket_fd);
 658                 free(xbuf);
 659                 free(rbuf);
 660         }
 661         return finished == 0; /* returns 1 on failure */
 662
 663  send_read_err_pkt:
 664         strcpy(G_error_pkt_str, bb_msg_read_error);
 665  send_err_pkt:
 666         if (G_error_pkt_str[0])
 667                 bb_error_msg("%s", G_error_pkt_str);
 668         G.error_pkt[1] = TFTP_ERROR;
 669         xsendto(socket_fd, G.error_pkt, 4 + 1 + strlen(G_error_pkt_str),
 670                         &peer_lsa->u.sa, peer_lsa->len);
 671         return EXIT_FAILURE;
 672 #undef remote_file
 673 }
 674
 675 #if ENABLE_TFTP
 676
 677 int tftp_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
 678 int tftp_main(int argc UNUSED_PARAM, char **argv)
 679 {
 680         len_and_sockaddr *peer_lsa;
 681         const char *local_file = NULL;
 682         const char *remote_file = NULL;
 683 # if ENABLE_FEATURE_TFTP_BLOCKSIZE
 684         const char *blksize_str = TFTP_BLKSIZE_DEFAULT_STR;
 685         int blksize;
 686 # endif
 687         int result;
 688         int port;
 689         IF_GETPUT(int opt;)
 690
 691         INIT_G();
 692
 693         /* -p or -g is mandatory, and they are mutually exclusive */
 694         opt_complementary = "" IF_FEATURE_TFTP_GET("g:") IF_FEATURE_TFTP_PUT("p:")
 695                         IF_GETPUT("g--p:p--g:");
 696
 697         IF_GETPUT(opt =) getopt32(argv,
 698                         IF_FEATURE_TFTP_GET("g") IF_FEATURE_TFTP_PUT("p")
 699                                 "l:r:" IF_FEATURE_TFTP_BLOCKSIZE("b:"),
 700                         &local_file, &remote_file
 701                         IF_FEATURE_TFTP_BLOCKSIZE(, &blksize_str));
 702         argv += optind;
 703
 704 # if ENABLE_FEATURE_TFTP_BLOCKSIZE
 705         /* Check if the blksize is valid:
 706          * RFC2348 says between 8 and 65464 */
 707         blksize = tftp_blksize_check(blksize_str, 65564);
 708         if (blksize < 0) {
 709                 //bb_error_msg("bad block size");
 710                 return EXIT_FAILURE;
 711         }
 712 # endif
 713
 714         if (remote_file) {
 715                 if (!local_file) {
 716                         const char *slash = strrchr(remote_file, '/');
 717                         local_file = slash ? slash + 1 : remote_file;
 718                 }
 719         } else {
 720                 remote_file = local_file;
 721         }
 722
 723         /* Error if filename or host is not known */
 724         if (!remote_file || !argv[0])
 725                 bb_show_usage();
 726
 727         port = bb_lookup_port(argv[1], "udp", 69);
 728         peer_lsa = xhost2sockaddr(argv[0], port);
 729
 730 # if ENABLE_TFTP_DEBUG
 731         fprintf(stderr, "using server '%s', remote_file '%s', local_file '%s'\n",
 732                         xmalloc_sockaddr2dotted(&peer_lsa->u.sa),
 733                         remote_file, local_file);
 734 # endif
 735
 736 # if ENABLE_FEATURE_TFTP_PROGRESS_BAR
 737         G.file = remote_file;
 738 # endif
 739         result = tftp_protocol(
 740                 NULL /*our_lsa*/, peer_lsa,
 741                 local_file, remote_file
 742                 IF_FEATURE_TFTP_BLOCKSIZE(, 1 /* want_transfer_size */)
 743                 IF_FEATURE_TFTP_BLOCKSIZE(, blksize)
 744         );
 745         tftp_progress_done();
 746
 747         if (result != EXIT_SUCCESS && NOT_LONE_DASH(local_file) && CMD_GET(opt)) {
 748                 unlink(local_file);
 749         }
 750         return result;
 751 }
 752
 753 #endif /* ENABLE_TFTP */
 754
 755 #if ENABLE_TFTPD
 756 int tftpd_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
 757 int tftpd_main(int argc UNUSED_PARAM, char **argv)
 758 {
 759         len_and_sockaddr *our_lsa;
 760         len_and_sockaddr *peer_lsa;
 761         char *mode, *user_opt;
 762         char *local_file = local_file;
 763         const char *error_msg;
 764         int opt, result, opcode;
 765         IF_FEATURE_TFTP_BLOCKSIZE(int blksize = TFTP_BLKSIZE_DEFAULT;)
 766         IF_FEATURE_TFTP_BLOCKSIZE(int want_transfer_size = 0;)
 767
 768         INIT_G();
 769
 770         our_lsa = get_sock_lsa(STDIN_FILENO);
 771         if (!our_lsa) {
 772                 /* This is confusing:
 773                  *bb_error_msg_and_die("stdin is not a socket");
 774                  * Better: */
 775                 bb_show_usage();
 776                 /* Help text says that tftpd must be used as inetd service,
 777                  * which is by far the most usual cause of get_sock_lsa
 778                  * failure */
 779         }
 780         peer_lsa = xzalloc(LSA_LEN_SIZE + our_lsa->len);
 781         peer_lsa->len = our_lsa->len;
 782
 783         /* Shifting to not collide with TFTP_OPTs */
 784         opt = option_mask32 = TFTPD_OPT | (getopt32(argv, "rcu:l", &user_opt) << 8);
 785         argv += optind;
 786         if (opt & TFTPD_OPT_l) {
 787                 openlog(applet_name, LOG_PID, LOG_DAEMON);
 788                 logmode = LOGMODE_SYSLOG;
 789         }
 790         if (opt & TFTPD_OPT_u) {
 791                 /* Must be before xchroot */
 792                 G.pw = xgetpwnam(user_opt);
 793         }
 794         if (argv[0]) {
 795                 xchroot(argv[0]);
 796         }
 797
 798         result = recv_from_to(STDIN_FILENO,
 799                         G.block_buf, sizeof(G.block_buf) + 1,
 800                         /* ^^^ sizeof+1 to reliably detect oversized input */
 801                         0 /* flags */,
 802                         &peer_lsa->u.sa, &our_lsa->u.sa, our_lsa->len);
 803
 804         error_msg = "malformed packet";
 805         opcode = ntohs(*(uint16_t*)G.block_buf);
 806         if (result < 4 || result > sizeof(G.block_buf)
 807         /*|| G.block_buf[result-1] != '\0' - bug compatibility, see below */
 808          || (IF_FEATURE_TFTP_PUT(opcode != TFTP_RRQ) /* not download */
 809              IF_GETPUT(&&)
 810              IF_FEATURE_TFTP_GET(opcode != TFTP_WRQ) /* not upload */
 811             )
 812         ) {
 813                 goto err;
 814         }
 815         /* Some HP PA-RISC firmware always sends fixed 516-byte requests,
 816          * with trailing garbage.
 817          * Support that by not requiring NUL to be the last byte (see above).
 818          * To make strXYZ() ops safe, force NUL termination:
 819          */
 820         G.block_buf_tail[0] = '\0';
 821
 822         local_file = G.block_buf + 2;
 823         if (local_file[0] == '.' || strstr(local_file, "/.")) {
 824                 error_msg = "dot in file name";
 825                 goto err;
 826         }
 827         mode = local_file + strlen(local_file) + 1;
 828         /* RFC 1350 says mode string is case independent */
 829         if (mode >= G.block_buf + result || strcasecmp(mode, "octet") != 0) {
 830                 goto err;
 831         }
 832 # if ENABLE_FEATURE_TFTP_BLOCKSIZE
 833         {
 834                 char *res;
 835                 char *opt_str = mode + sizeof("octet");
 836                 int opt_len = G.block_buf + result - opt_str;
 837                 if (opt_len > 0) {
 838                         res = tftp_get_option("blksize", opt_str, opt_len);
 839                         if (res) {
 840                                 blksize = tftp_blksize_check(res, 65564);
 841                                 if (blksize < 0) {
 842                                         G_error_pkt_reason = ERR_BAD_OPT;
 843                                         /* will just send error pkt */
 844                                         goto do_proto;
 845                                 }
 846                         }
 847                         if (opcode != TFTP_WRQ /* download? */
 848                         /* did client ask us about file size? */
 849                          && tftp_get_option("tsize", opt_str, opt_len)
 850                         ) {
 851                                 want_transfer_size = 1;
 852                         }
 853                 }
 854         }
 855 # endif
 856
 857         if (!ENABLE_FEATURE_TFTP_PUT || opcode == TFTP_WRQ) {
 858                 if (opt & TFTPD_OPT_r) {
 859                         /* This would mean "disk full" - not true */
 860                         /*G_error_pkt_reason = ERR_WRITE;*/
 861                         error_msg = bb_msg_write_error;
 862                         goto err;
 863                 }
 864                 IF_GETPUT(option_mask32 |= TFTP_OPT_GET;) /* will receive file's data */
 865         } else {
 866                 IF_GETPUT(option_mask32 |= TFTP_OPT_PUT;) /* will send file's data */
 867         }
 868
 869         /* NB: if G_error_pkt_str or G_error_pkt_reason is set up,
 870          * tftp_protocol() just sends one error pkt and returns */
 871
 872  do_proto:
 873         close(STDIN_FILENO); /* close old, possibly wildcard socket */
 874         /* tftp_protocol() will create new one, bound to particular local IP */
 875         result = tftp_protocol(
 876                 our_lsa, peer_lsa,
 877                 local_file IF_TFTP(, NULL /*remote_file*/)
 878                 IF_FEATURE_TFTP_BLOCKSIZE(, want_transfer_size)
 879                 IF_FEATURE_TFTP_BLOCKSIZE(, blksize)
 880         );
 881
 882         return result;
 883  err:
 884         strcpy(G_error_pkt_str, error_msg);
 885         goto do_proto;
 886 }
 887
 888 #endif /* ENABLE_TFTPD */
 889
 890 #endif /* ENABLE_FEATURE_TFTP_GET || ENABLE_FEATURE_TFTP_PUT */