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