networking/tftp.c

   1 /* vi: set sw=4 ts=4: */
   2 /* -------------------------------------------------------------------------
   3  * tftp.c
   4  *
   5  * A simple tftp client for busybox.
   6  * Tries to follow RFC1350.
   7  * Only "octet" mode supported.
   8  * Optional blocksize negotiation (RFC2347 + RFC2348)
   9  *
  10  * Copyright (C) 2001 Magnus Damm <damm@opensource.se>
  11  *
  12  * Parts of the code based on:
  13  *
  14  * atftp:  Copyright (C) 2000 Jean-Pierre Lefebvre <helix@step.polymtl.ca>
  15  *                        and Remi Lefebvre <remi@debian.org>
  16  *
  17  * utftp:  Copyright (C) 1999 Uwe Ohse <uwe@ohse.de>
  18  *
  19  * Licensed under GPLv2 or later, see file LICENSE in this tarball for details.
  20  * ------------------------------------------------------------------------- */
  21
  22 #include "libbb.h"
  23
  24
  25 #if ENABLE_FEATURE_TFTP_GET || ENABLE_FEATURE_TFTP_PUT
  26
  27 #define TFTP_BLOCKSIZE_DEFAULT 512      /* according to RFC 1350, don't change */
  28 #define TFTP_TIMEOUT 5  /* seconds */
  29 #define TFTP_NUM_RETRIES 5 /* number of retries */
  30
  31 /* opcodes we support */
  32 #define TFTP_RRQ   1
  33 #define TFTP_WRQ   2
  34 #define TFTP_DATA  3
  35 #define TFTP_ACK   4
  36 #define TFTP_ERROR 5
  37 #define TFTP_OACK  6
  38
  39 #if ENABLE_FEATURE_TFTP_GET && !ENABLE_FEATURE_TFTP_PUT
  40 #define USE_GETPUT(...)
  41 #define CMD_GET(cmd) 1
  42 #define CMD_PUT(cmd) 0
  43 #elif !ENABLE_FEATURE_TFTP_GET && ENABLE_FEATURE_TFTP_PUT
  44 #define USE_GETPUT(...)
  45 #define CMD_GET(cmd) 0
  46 #define CMD_PUT(cmd) 1
  47 #else
  48 #define USE_GETPUT(...) __VA_ARGS__
  49 /* masks coming from getpot32 */
  50 #define CMD_GET(cmd) ((cmd) & 1)
  51 #define CMD_PUT(cmd) ((cmd) & 2)
  52 #endif
  53 /* NB: in the code below
  54  * CMD_GET(cmd) and CMD_PUT(cmd) are mutually exclusive
  55  */
  56
  57
  58 #if ENABLE_FEATURE_TFTP_BLOCKSIZE
  59
  60 static int tftp_blocksize_check(int blocksize, int bufsize)
  61 {
  62         /* Check if the blocksize is valid:
  63          * RFC2348 says between 8 and 65464,
  64          * but our implementation makes it impossible
  65          * to use blocksizes smaller than 22 octets.
  66          */
  67
  68         if ((bufsize && (blocksize > bufsize))
  69          || (blocksize < 8) || (blocksize > 65564)
  70         ) {
  71                 bb_error_msg("bad blocksize");
  72                 return 0;
  73         }
  74
  75         return blocksize;
  76 }
  77
  78 static char *tftp_option_get(char *buf, int len, const char *option)
  79 {
  80         int opt_val = 0;
  81         int opt_found = 0;
  82         int k;
  83
  84         while (len > 0) {
  85                 /* Make sure the options are terminated correctly */
  86                 for (k = 0; k < len; k++) {
  87                         if (buf[k] == '\0') {
  88                                 goto nul_found;
  89                         }
  90                 }
  91                 return NULL;
  92  nul_found:
  93                 if (opt_val == 0) {
  94                         if (strcasecmp(buf, option) == 0) {
  95                                 opt_found = 1;
  96                         }
  97                 } else if (opt_found) {
  98                         return buf;
  99                 }
 100
 101                 k++;
 102                 buf += k;
 103                 len -= k;
 104                 opt_val ^= 1;
 105         }
 106
 107         return NULL;
 108 }
 109
 110 #endif
 111
 112 static int tftp( USE_GETPUT(const int cmd,)
 113                 len_and_sockaddr *peer_lsa,
 114                 const char *remotefile, const int localfd,
 115                 unsigned port, int tftp_bufsize)
 116 {
 117         struct timeval tv;
 118         fd_set rfds;
 119         int socketfd;
 120         int len;
 121         int send_len;
 122         USE_FEATURE_TFTP_BLOCKSIZE(smallint want_option_ack = 0;)
 123         smallint finished = 0;
 124         uint16_t opcode;
 125         uint16_t block_nr = 1;
 126         uint16_t recv_blk;
 127         int timeout = TFTP_NUM_RETRIES;
 128         char *cp;
 129
 130         unsigned org_port;
 131         len_and_sockaddr *const from = alloca(offsetof(len_and_sockaddr, sa) + peer_lsa->len);
 132
 133         /* Can't use RESERVE_CONFIG_BUFFER here since the allocation
 134          * size varies meaning BUFFERS_GO_ON_STACK would fail */
 135         /* We must keep the transmit and receive buffers seperate */
 136         /* In case we rcv a garbage pkt and we need to rexmit the last pkt */
 137         char *xbuf = xmalloc(tftp_bufsize += 4);
 138         char *rbuf = xmalloc(tftp_bufsize);
 139
 140         port = org_port = htons(port);
 141
 142         socketfd = xsocket(peer_lsa->sa.sa_family, SOCK_DGRAM, 0);
 143
 144         /* build opcode */
 145         opcode = TFTP_WRQ;
 146         if (CMD_GET(cmd)) {
 147                 opcode = TFTP_RRQ;
 148         }
 149         cp = xbuf + 2;
 150         /* add filename and mode */
 151         /* fill in packet if the filename fits into xbuf */
 152         len = strlen(remotefile) + 1;
 153         if (2 + len + sizeof("octet") >= tftp_bufsize) {
 154                 bb_error_msg("remote filename is too long");
 155                 goto ret;
 156         }
 157         strcpy(cp, remotefile);
 158         cp += len;
 159         /* add "mode" part of the package */
 160         strcpy(cp, "octet");
 161         cp += sizeof("octet");
 162
 163 #if ENABLE_FEATURE_TFTP_BLOCKSIZE
 164         len = tftp_bufsize - 4; /* data block size */
 165         if (len != TFTP_BLOCKSIZE_DEFAULT) {
 166                 /* rfc2348 says that 65464 is a max allowed value */
 167                 if ((&xbuf[tftp_bufsize - 1] - cp) < sizeof("blksize NNNNN")) {
 168                         bb_error_msg("remote filename is too long");
 169                         goto ret;
 170                 }
 171                 /* add "blksize", <nul>, blocksize */
 172                 strcpy(cp, "blksize");
 173                 cp += sizeof("blksize");
 174                 cp += snprintf(cp, 6, "%d", len) + 1;
 175                 want_option_ack = 1;
 176         }
 177 #endif
 178         /* First packet is built, so skip packet generation */
 179         goto send_pkt;
 180
 181         /* Using mostly goto's - continue/break will be less clear
 182          * in where we actually jump to */
 183
 184         while (1) {
 185                 /* Build ACK or DATA */
 186                 cp = xbuf + 2;
 187                 *((uint16_t*)cp) = htons(block_nr);
 188                 cp += 2;
 189                 block_nr++;
 190                 opcode = TFTP_ACK;
 191                 if (CMD_PUT(cmd)) {
 192                         opcode = TFTP_DATA;
 193                         len = full_read(localfd, cp, tftp_bufsize - 4);
 194                         if (len < 0) {
 195                                 bb_perror_msg(bb_msg_read_error);
 196                                 goto ret;
 197                         }
 198                         if (len != (tftp_bufsize - 4)) {
 199                                 finished = 1;
 200                         }
 201                         cp += len;
 202                 }
 203  send_pkt:
 204                 /* Send packet */
 205                 *((uint16_t*)xbuf) = htons(opcode); /* fill in opcode part */
 206                 send_len = cp - xbuf;
 207                 /* NB: send_len value is preserved in code below
 208                  * for potential resend */
 209  send_again:
 210 #if ENABLE_DEBUG_TFTP
 211                 fprintf(stderr, "sending %u bytes\n", send_len);
 212                 for (cp = xbuf; cp < &xbuf[send_len]; cp++)
 213                         fprintf(stderr, "%02x ", (unsigned char) *cp);
 214                 fprintf(stderr, "\n");
 215 #endif
 216                 xsendto(socketfd, xbuf, send_len, &peer_lsa->sa, peer_lsa->len);
 217                 /* Was it final ACK? then exit */
 218                 if (finished && (opcode == TFTP_ACK))
 219                         goto ret;
 220
 221                 timeout = TFTP_NUM_RETRIES;     /* re-initialize */
 222  recv_again:
 223                 /* Receive packet */
 224                 tv.tv_sec = TFTP_TIMEOUT;
 225                 tv.tv_usec = 0;
 226                 FD_ZERO(&rfds);
 227                 FD_SET(socketfd, &rfds);
 228                 switch (select(socketfd + 1, &rfds, NULL, NULL, &tv)) {
 229                         unsigned from_port;
 230                 case 1:
 231                         from->len = peer_lsa->len;
 232                         memset(&from->sa, 0, peer_lsa->len);
 233                         len = recvfrom(socketfd, rbuf, tftp_bufsize, 0,
 234                                                 &from->sa, &from->len);
 235                         if (len < 0) {
 236                                 bb_perror_msg("recvfrom");
 237                                 goto ret;
 238                         }
 239                         from_port = get_nport(&from->sa);
 240                         if (port == org_port) {
 241                                 /* Our first query went to port 69
 242                                  * but reply will come from different one.
 243                                  * Remember and use this new port */
 244                                 port = from_port;
 245                                 set_nport(peer_lsa, from_port);
 246                         }
 247                         if (port != from_port)
 248                                 goto recv_again;
 249                         goto process_pkt;
 250                 case 0:
 251                         timeout--;
 252                         if (timeout == 0) {
 253                                 bb_error_msg("last timeout");
 254                                 goto ret;
 255                         }
 256                         bb_error_msg("last timeout" + 5);
 257                         goto send_again; /* resend last sent pkt */
 258                 default:
 259                         bb_perror_msg("select");
 260                         goto ret;
 261                 }
 262  process_pkt:
 263                 /* Process recv'ed packet */
 264                 opcode = ntohs( ((uint16_t*)rbuf)[0] );
 265                 recv_blk = ntohs( ((uint16_t*)rbuf)[1] );
 266
 267 #if ENABLE_DEBUG_TFTP
 268                 fprintf(stderr, "received %d bytes: %04x %04x\n", len, opcode, recv_blk);
 269 #endif
 270
 271                 if (opcode == TFTP_ERROR) {
 272                         static const char *const errcode_str[] = {
 273                                 "",
 274                                 "file not found",
 275                                 "access violation",
 276                                 "disk full",
 277                                 "illegal TFTP operation",
 278                                 "unknown transfer id",
 279                                 "file already exists",
 280                                 "no such user",
 281                                 "bad option",
 282                         };
 283                         enum { NUM_ERRCODE = sizeof(errcode_str) / sizeof(errcode_str[0]) };
 284                         const char *msg = "";
 285
 286                         if (rbuf[4] != '\0') {
 287                                 msg = &rbuf[4];
 288                                 rbuf[tftp_bufsize - 1] = '\0';
 289                         } else if (recv_blk < NUM_ERRCODE) {
 290                                 msg = errcode_str[recv_blk];
 291                         }
 292                         bb_error_msg("server error: (%u) %s", recv_blk, msg);
 293                         goto ret;
 294                 }
 295
 296 #if ENABLE_FEATURE_TFTP_BLOCKSIZE
 297                 if (want_option_ack) {
 298                         want_option_ack = 0;
 299
 300                         if (opcode == TFTP_OACK) {
 301                                 /* server seems to support options */
 302                                 char *res;
 303
 304                                 res = tftp_option_get(&rbuf[2], len - 2, "blksize");
 305                                 if (res) {
 306                                         int blksize = xatoi_u(res);
 307                                         if (!tftp_blocksize_check(blksize, tftp_bufsize - 4)) {
 308                                                 /* send ERROR 8 to server... */
 309                                                 /* htons can be impossible to use in const initializer: */
 310                                                 /*static const uint16_t error_8[2] = { htons(TFTP_ERROR), htons(8) };*/
 311                                                 /* thus we open-code big-endian layout */
 312                                                 static const char error_8[4] = { 0,TFTP_ERROR, 0,8 };
 313                                                 xsendto(socketfd, error_8, 4, &peer_lsa->sa, peer_lsa->len);
 314                                                 bb_error_msg("server proposes bad blksize %d, exiting", blksize);
 315                                                 goto ret;
 316                                         }
 317 #if ENABLE_DEBUG_TFTP
 318                                         fprintf(stderr, "using blksize %u\n",
 319                                                         blksize);
 320 #endif
 321                                         tftp_bufsize = blksize + 4;
 322                                         /* Send ACK for OACK ("block" no: 0) */
 323                                         block_nr = 0;
 324                                         continue;
 325                                 }
 326                                 /* rfc2347:
 327                                  * "An option not acknowledged by the server
 328                                  *  must be ignored by the client and server
 329                                  *  as if it were never requested." */
 330                         }
 331
 332                         bb_error_msg("blksize is not supported by server"
 333                                                 " - reverting to 512");
 334                         tftp_bufsize = TFTP_BLOCKSIZE_DEFAULT + 4;
 335                 }
 336 #endif
 337                 /* block_nr is already advanced to next block# we expect
 338                  * to get / block# we are about to send next time */
 339
 340                 if (CMD_GET(cmd) && (opcode == TFTP_DATA)) {
 341                         if (recv_blk == block_nr) {
 342                                 len = full_write(localfd, &rbuf[4], len - 4);
 343                                 if (len < 0) {
 344                                         bb_perror_msg(bb_msg_write_error);
 345                                         goto ret;
 346                                 }
 347                                 if (len != (tftp_bufsize - 4)) {
 348                                         finished = 1;
 349                                 }
 350                                 continue; /* send ACK */
 351                         }
 352                         if (recv_blk == (block_nr - 1)) {
 353                                 /* Server lost our TFTP_ACK.  Resend it */
 354                                 block_nr = recv_blk;
 355                                 continue;
 356                         }
 357                 }
 358
 359                 if (CMD_PUT(cmd) && (opcode == TFTP_ACK)) {
 360                         /* did server ACK our last DATA pkt? */
 361                         if (recv_blk == (uint16_t) (block_nr - 1)) {
 362                                 if (finished)
 363                                         goto ret;
 364                                 continue; /* send next block */
 365                         }
 366                 }
 367                 /* Awww... recv'd packet is not recognized! */
 368                 goto recv_again;
 369                 /* why recv_again? - rfc1123 says:
 370                  * "The sender (i.e., the side originating the DATA packets)
 371                  *  must never resend the current DATA packet on receipt
 372                  *  of a duplicate ACK".
 373                  * DATA pkts are resent ONLY on timeout.
 374                  * Thus "goto send_again" will ba a bad mistake above.
 375                  * See:
 376                  * http://en.wikipedia.org/wiki/Sorcerer's_Apprentice_Syndrome
 377                  */
 378         }
 379  ret:
 380         if (ENABLE_FEATURE_CLEAN_UP) {
 381                 close(socketfd);
 382                 free(xbuf);
 383                 free(rbuf);
 384         }
 385         return finished == 0; /* returns 1 on failure */
 386 }
 387
 388 int tftp_main(int argc, char **argv);
 389 int tftp_main(int argc, char **argv)
 390 {
 391         len_and_sockaddr *peer_lsa;
 392         const char *localfile = NULL;
 393         const char *remotefile = NULL;
 394 #if ENABLE_FEATURE_TFTP_BLOCKSIZE
 395         const char *sblocksize = NULL;
 396 #endif
 397         int port;
 398         USE_GETPUT(int cmd;)
 399         int fd = -1;
 400         int flags = 0;
 401         int result;
 402         int blocksize = TFTP_BLOCKSIZE_DEFAULT;
 403
 404         /* -p or -g is mandatory, and they are mutually exclusive */
 405         opt_complementary = "" USE_FEATURE_TFTP_GET("g:") USE_FEATURE_TFTP_PUT("p:")
 406                         USE_GETPUT("?g--p:p--g");
 407
 408         USE_GETPUT(cmd =) getopt32(argc, argv,
 409                         USE_FEATURE_TFTP_GET("g") USE_FEATURE_TFTP_PUT("p")
 410                                 "l:r:" USE_FEATURE_TFTP_BLOCKSIZE("b:"),
 411                         &localfile, &remotefile
 412                         USE_FEATURE_TFTP_BLOCKSIZE(, &sblocksize));
 413         argv += optind;
 414
 415         flags = O_RDONLY;
 416         if (CMD_GET(cmd))
 417                 flags = O_WRONLY | O_CREAT | O_TRUNC;
 418
 419 #if ENABLE_FEATURE_TFTP_BLOCKSIZE
 420         if (sblocksize) {
 421                 blocksize = xatoi_u(sblocksize);
 422                 if (!tftp_blocksize_check(blocksize, 0)) {
 423                         return EXIT_FAILURE;
 424                 }
 425         }
 426 #endif
 427
 428         if (!localfile)
 429                 localfile = remotefile;
 430         if (!remotefile)
 431                 remotefile = localfile;
 432         /* Error if filename or host is not known */
 433         if (!remotefile || !argv[0])
 434                 bb_show_usage();
 435
 436         fd = CMD_GET(cmd) ? STDOUT_FILENO : STDIN_FILENO;
 437         if (!LONE_DASH(localfile)) {
 438                 fd = xopen(localfile, flags);
 439         }
 440
 441         port = bb_lookup_port(argv[1], "udp", 69);
 442         peer_lsa = xhost2sockaddr(argv[0], port);
 443
 444 #if ENABLE_DEBUG_TFTP
 445         fprintf(stderr, "using server '%s', remotefile '%s', localfile '%s'\n",
 446                         xmalloc_sockaddr2dotted(&peer_lsa->sa, peer_lsa->len),
 447                         remotefile, localfile);
 448 #endif
 449
 450         result = tftp( USE_GETPUT(cmd,) peer_lsa, remotefile, fd, port, blocksize);
 451
 452         if (ENABLE_FEATURE_CLEAN_UP)
 453                 close(fd);
 454         if (result != EXIT_SUCCESS && !LONE_DASH(localfile) && CMD_GET(cmd)) {
 455                 unlink(localfile);
 456         }
 457         return result;
 458 }
 459
 460 #endif /* ENABLE_FEATURE_TFTP_GET || ENABLE_FEATURE_TFTP_PUT */