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 //config:config TFTP
  22 //config:       bool "tftp (11 kb)"
  23 //config:       default y
  24 //config:       help
  25 //config:       Trivial File Transfer Protocol client. TFTP is usually used
  26 //config:       for simple, small transfers such as a root image
  27 //config:       for a network-enabled bootloader.
  28 //config:
  29 //config:config FEATURE_TFTP_PROGRESS_BAR
  30 //config:       bool "Enable progress bar"
  31 //config:       default y
  32 //config:       depends on TFTP
  33 //config:
  34 //config:config FEATURE_TFTP_HPA_COMPAT
  35 //config:       bool "tftp-hpa compat (support -c get/put FILE)"
  36 //config:       default y
  37 //config:       depends on TFTP
  38 //config:
  39 //config:config TFTPD
  40 //config:       bool "tftpd (10 kb)"
  41 //config:       default y
  42 //config:       help
  43 //config:       Trivial File Transfer Protocol server.
  44 //config:       It expects that stdin is a datagram socket and a packet
  45 //config:       is already pending on it. It will exit after one transfer.
  46 //config:       In other words: it should be run from inetd in nowait mode,
  47 //config:       or from udpsvd. Example: "udpsvd -E 0 69 tftpd DIR"
  48 //config:
  49 //config:config FEATURE_TFTP_GET
  50 //config:       bool "Enable 'tftp get' and/or tftpd upload code"
  51 //config:       default y
  52 //config:       depends on TFTP || TFTPD
  53 //config:       help
  54 //config:       Add support for the GET command within the TFTP client. This allows
  55 //config:       a client to retrieve a file from a TFTP server.
  56 //config:       Also enable upload support in tftpd, if tftpd is selected.
  57 //config:
  58 //config:       Note: this option does _not_ make tftpd capable of download
  59 //config:       (the usual operation people need from it)!
  60 //config:
  61 //config:config FEATURE_TFTP_PUT
  62 //config:       bool "Enable 'tftp put' and/or tftpd download code"
  63 //config:       default y
  64 //config:       depends on TFTP || TFTPD
  65 //config:       help
  66 //config:       Add support for the PUT command within the TFTP client. This allows
  67 //config:       a client to transfer a file to a TFTP server.
  68 //config:       Also enable download support in tftpd, if tftpd is selected.
  69 //config:
  70 //config:config FEATURE_TFTP_BLOCKSIZE
  71 //config:       bool "Enable 'blksize' and 'tsize' protocol options"
  72 //config:       default y
  73 //config:       depends on TFTP || TFTPD
  74 //config:       help
  75 //config:       Allow tftp to specify block size, and tftpd to understand
  76 //config:       "blksize" and "tsize" options.
  77 //config:
  78 //config:config TFTP_DEBUG
  79 //config:       bool "Enable debug"
  80 //config:       default n
  81 //config:       depends on TFTP || TFTPD
  82 //config:       help
  83 //config:       Make tftp[d] print debugging messages on stderr.
  84 //config:       This is useful if you are diagnosing a bug in tftp[d].
  85
  86 //applet:#if ENABLE_FEATURE_TFTP_GET || ENABLE_FEATURE_TFTP_PUT
  87 //applet:IF_TFTP(APPLET(tftp, BB_DIR_USR_BIN, BB_SUID_DROP))
  88 //applet:IF_TFTPD(APPLET(tftpd, BB_DIR_USR_SBIN, BB_SUID_DROP))
  89 //applet:#endif
  90
  91 //kbuild:lib-$(CONFIG_TFTP) += tftp.o
  92 //kbuild:lib-$(CONFIG_TFTPD) += tftp.o
  93
  94 //usage:#define tftp_trivial_usage
  95 //usage:       "[OPTIONS] HOST [PORT]"
  96 //usage:#define tftp_full_usage "\n\n"
  97 //usage:       "Transfer a file from/to tftp server\n"
  98 //usage:     "\n        -l FILE Local FILE"
  99 //usage:     "\n        -r FILE Remote FILE"
 100 //usage:        IF_FEATURE_TFTP_GET(
 101 //usage:     "\n        -g      Get file"
 102 //usage:        )
 103 //usage:        IF_FEATURE_TFTP_PUT(
 104 //usage:     "\n        -p      Put file"
 105 //usage:        )
 106 //usage:        IF_FEATURE_TFTP_BLOCKSIZE(
 107 //usage:     "\n        -b SIZE Transfer blocks of SIZE octets"
 108 //usage:        )
 109 ///////:     "\n        -m STR  Accepted and ignored ('-m binary' compat with tftp-hpa 5.2)"
 110 //usage:
 111 //usage:#define tftpd_trivial_usage
 112 //usage:       "[-crl] [-u USER] [DIR]"
 113 //usage:#define tftpd_full_usage "\n\n"
 114 //usage:       "Transfer a file on tftp client's request\n"
 115 //usage:       "\n"
 116 //usage:       "tftpd should be used as an inetd service.\n"
 117 //usage:       "tftpd's line for inetd.conf:\n"
 118 //usage:       "        69 dgram udp nowait root tftpd tftpd -l /files/to/serve\n"
 119 //usage:       "It also can be ran from udpsvd:\n"
 120 //usage:       "        udpsvd -vE 0.0.0.0 69 tftpd /files/to/serve\n"
 121 //usage:     "\n        -r      Prohibit upload"
 122 //usage:     "\n        -c      Allow file creation via upload"
 123 //usage:     "\n        -u      Access files as USER"
 124 //usage:     "\n        -l      Log to syslog (inetd mode requires this)"
 125
 126 #include "libbb.h"
 127 #include "common_bufsiz.h"
 128 #include <syslog.h>
 129
 130 #if ENABLE_FEATURE_TFTP_GET || ENABLE_FEATURE_TFTP_PUT
 131
 132 #define TFTP_BLKSIZE_DEFAULT       512  /* according to RFC 1350, don't change */
 133 #define TFTP_BLKSIZE_DEFAULT_STR "512"
 134 /* Was 50 ms but users asked to bump it up a bit */
 135 #define TFTP_TIMEOUT_MS            100
 136 #define TFTP_MAXTIMEOUT_MS        2000
 137 #define TFTP_NUM_RETRIES            12  /* number of backed-off retries */
 138
 139 /* opcodes we support */
 140 #define TFTP_RRQ   1
 141 #define TFTP_WRQ   2
 142 #define TFTP_DATA  3
 143 #define TFTP_ACK   4
 144 #define TFTP_ERROR 5
 145 #define TFTP_OACK  6
 146
 147 /* error codes sent over network (we use only 0, 1, 3 and 8) */
 148 /* generic (error message is included in the packet) */
 149 #define ERR_UNSPEC   0
 150 #define ERR_NOFILE   1
 151 #define ERR_ACCESS   2
 152 /* disk full or allocation exceeded */
 153 #define ERR_WRITE    3
 154 #define ERR_OP       4
 155 #define ERR_BAD_ID   5
 156 #define ERR_EXIST    6
 157 #define ERR_BAD_USER 7
 158 #define ERR_BAD_OPT  8
 159
 160 /* masks coming from getopt32 */
 161 enum {
 162         TFTP_OPT_GET = (1 << 0),
 163         TFTP_OPT_PUT = (1 << 1),
 164         /* pseudo option: if set, it's tftpd */
 165         TFTPD_OPT = (1 << 7) * ENABLE_TFTPD,
 166         TFTPD_OPT_r = (1 << 8) * ENABLE_TFTPD,
 167         TFTPD_OPT_c = (1 << 9) * ENABLE_TFTPD,
 168         TFTPD_OPT_u = (1 << 10) * ENABLE_TFTPD,
 169         TFTPD_OPT_l = (1 << 11) * ENABLE_TFTPD,
 170 };
 171
 172 #if ENABLE_FEATURE_TFTP_GET && !ENABLE_FEATURE_TFTP_PUT
 173 #define IF_GETPUT(...)
 174 #define CMD_GET(cmd) 1
 175 #define CMD_PUT(cmd) 0
 176 #elif !ENABLE_FEATURE_TFTP_GET && ENABLE_FEATURE_TFTP_PUT
 177 #define IF_GETPUT(...)
 178 #define CMD_GET(cmd) 0
 179 #define CMD_PUT(cmd) 1
 180 #else
 181 #define IF_GETPUT(...) __VA_ARGS__
 182 #define CMD_GET(cmd) ((cmd) & TFTP_OPT_GET)
 183 #define CMD_PUT(cmd) ((cmd) & TFTP_OPT_PUT)
 184 #endif
 185 /* NB: in the code below
 186  * CMD_GET(cmd) and CMD_PUT(cmd) are mutually exclusive
 187  */
 188
 189
 190 struct globals {
 191         /* u16 TFTP_ERROR; u16 reason; both network-endian, then error text: */
 192         uint8_t error_pkt[4 + 32];
 193         struct passwd *pw;
 194         /* Used in tftpd_main() for initial packet */
 195         /* Some HP PA-RISC firmware always sends fixed 516-byte requests */
 196         char block_buf[516];
 197         char block_buf_tail[1];
 198 #if ENABLE_FEATURE_TFTP_PROGRESS_BAR
 199         off_t pos;
 200         off_t size;
 201         const char *file;
 202         bb_progress_t pmt;
 203 #endif
 204 } FIX_ALIASING;
 205 #define G (*(struct globals*)bb_common_bufsiz1)
 206 #define INIT_G() do { \
 207         setup_common_bufsiz(); \
 208         BUILD_BUG_ON(sizeof(G) > COMMON_BUFSIZE); \
 209 } while (0)
 210
 211 #define G_error_pkt_reason (G.error_pkt[3])
 212 #define G_error_pkt_str    ((char*)(G.error_pkt + 4))
 213
 214 #if ENABLE_FEATURE_TFTP_PROGRESS_BAR && ENABLE_FEATURE_TFTP_BLOCKSIZE
 215 static void tftp_progress_update(void)
 216 {
 217         bb_progress_update(&G.pmt, 0, G.pos, G.size);
 218 }
 219 static void tftp_progress_init(void)
 220 {
 221         bb_progress_init(&G.pmt, G.file);
 222         tftp_progress_update();
 223 }
 224 static void tftp_progress_done(void)
 225 {
 226         if (is_bb_progress_inited(&G.pmt)) {
 227                 tftp_progress_update();
 228                 bb_putchar_stderr('\n');
 229                 bb_progress_free(&G.pmt);
 230         }
 231 }
 232 #else
 233 # define tftp_progress_update() ((void)0)
 234 # define tftp_progress_init() ((void)0)
 235 # define tftp_progress_done() ((void)0)
 236 #endif
 237
 238 #if ENABLE_FEATURE_TFTP_BLOCKSIZE
 239
 240 static int tftp_blksize_check(const char *blksize_str, int maxsize)
 241 {
 242         /* Check if the blksize is valid:
 243          * RFC2348 says between 8 and 65464,
 244          * but our implementation makes it impossible
 245          * to use blksizes smaller than 22 octets. */
 246         unsigned blksize = bb_strtou(blksize_str, NULL, 10);
 247         if (errno
 248          || (blksize < 24) || (blksize > maxsize)
 249         ) {
 250                 bb_error_msg("bad blocksize '%s'", blksize_str);
 251                 return -1;
 252         }
 253 # if ENABLE_TFTP_DEBUG
 254         bb_info_msg("using blksize %u", blksize);
 255 # endif
 256         return blksize;
 257 }
 258
 259 static char *tftp_get_option(const char *option, char *buf, int len)
 260 {
 261         int opt_val = 0;
 262         int opt_found = 0;
 263         int k;
 264
 265         /* buf points to:
 266          * "opt_name<NUL>opt_val<NUL>opt_name2<NUL>opt_val2<NUL>..." */
 267
 268         while (len > 0) {
 269                 /* Make sure options are terminated correctly */
 270                 for (k = 0; k < len; k++) {
 271                         if (buf[k] == '\0') {
 272                                 goto nul_found;
 273                         }
 274                 }
 275                 return NULL;
 276  nul_found:
 277                 if (opt_val == 0) { /* it's "name" part */
 278                         if (strcasecmp(buf, option) == 0) {
 279                                 opt_found = 1;
 280                         }
 281                 } else if (opt_found) {
 282                         return buf;
 283                 }
 284
 285                 k++;
 286                 buf += k;
 287                 len -= k;
 288                 opt_val ^= 1;
 289         }
 290
 291         return NULL;
 292 }
 293
 294 #endif
 295
 296 static int tftp_protocol(
 297                 /* NULL if tftp, !NULL if tftpd: */
 298                 len_and_sockaddr *our_lsa,
 299                 len_and_sockaddr *peer_lsa,
 300                 const char *local_file
 301                 IF_TFTP(, const char *remote_file)
 302 #if !ENABLE_TFTP
 303 # define remote_file NULL
 304 #endif
 305                 /* 1 for tftp; 1/0 for tftpd depending whether client asked about it: */
 306                 IF_FEATURE_TFTP_BLOCKSIZE(, int want_transfer_size)
 307                 IF_FEATURE_TFTP_BLOCKSIZE(, int blksize))
 308 {
 309 #if !ENABLE_FEATURE_TFTP_BLOCKSIZE
 310         enum { blksize = TFTP_BLKSIZE_DEFAULT };
 311 #endif
 312
 313         struct pollfd pfd[1];
 314 #define socket_fd (pfd[0].fd)
 315         int len;
 316         int send_len;
 317         IF_FEATURE_TFTP_BLOCKSIZE(smallint expect_OACK = 0;)
 318         smallint finished = 0;
 319         uint16_t opcode;
 320         uint16_t block_nr;
 321         uint16_t recv_blk;
 322         int local_fd = -1;
 323         int retries, waittime_ms;
 324         int io_bufsize = blksize + 4;
 325         char *cp;
 326         /* Can't use RESERVE_CONFIG_BUFFER here since the allocation
 327          * size varies meaning BUFFERS_GO_ON_STACK would fail.
 328          *
 329          * We must keep the transmit and receive buffers separate
 330          * in case we rcv a garbage pkt - we need to rexmit the last pkt.
 331          */
 332         char *xbuf = xmalloc(io_bufsize);
 333         char *rbuf = xmalloc(io_bufsize);
 334
 335         socket_fd = xsocket(peer_lsa->u.sa.sa_family, SOCK_DGRAM, 0);
 336         setsockopt_reuseaddr(socket_fd);
 337
 338         if (!ENABLE_TFTP || our_lsa) { /* tftpd */
 339                 /* Create a socket which is:
 340                  * 1. bound to IP:port peer sent 1st datagram to,
 341                  * 2. connected to peer's IP:port
 342                  * This way we will answer from the IP:port peer
 343                  * expects, will not get any other packets on
 344                  * the socket, and also plain read/write will work. */
 345                 xbind(socket_fd, &our_lsa->u.sa, our_lsa->len);
 346                 xconnect(socket_fd, &peer_lsa->u.sa, peer_lsa->len);
 347
 348                 /* Is there an error already? Send pkt and bail out */
 349                 if (G_error_pkt_reason || G_error_pkt_str[0])
 350                         goto send_err_pkt;
 351
 352                 if (G.pw) {
 353                         change_identity(G.pw); /* initgroups, setgid, setuid */
 354                 }
 355         }
 356
 357         /* Examples of network traffic.
 358          * Note two cases when ACKs with block# of 0 are sent.
 359          *
 360          * Download without options:
 361          * tftp -> "\0\1FILENAME\0octet\0"
 362          *         "\0\3\0\1FILEDATA..." <- tftpd
 363          * tftp -> "\0\4\0\1"
 364          * ...
 365          * Download with option of blksize 16384:
 366          * tftp -> "\0\1FILENAME\0octet\0blksize\00016384\0"
 367          *         "\0\6blksize\00016384\0" <- tftpd
 368          * tftp -> "\0\4\0\0"
 369          *         "\0\3\0\1FILEDATA..." <- tftpd
 370          * tftp -> "\0\4\0\1"
 371          * ...
 372          * Upload without options:
 373          * tftp -> "\0\2FILENAME\0octet\0"
 374          *         "\0\4\0\0" <- tftpd
 375          * tftp -> "\0\3\0\1FILEDATA..."
 376          *         "\0\4\0\1" <- tftpd
 377          * ...
 378          * Upload with option of blksize 16384:
 379          * tftp -> "\0\2FILENAME\0octet\0blksize\00016384\0"
 380          *         "\0\6blksize\00016384\0" <- tftpd
 381          * tftp -> "\0\3\0\1FILEDATA..."
 382          *         "\0\4\0\1" <- tftpd
 383          * ...
 384          */
 385         block_nr = 1;
 386         cp = xbuf + 2;
 387
 388         if (!ENABLE_TFTP || our_lsa) { /* tftpd */
 389                 /* Open file (must be after changing user) */
 390                 int open_mode = O_RDONLY;
 391                 if (CMD_GET(option_mask32)) {
 392                         open_mode = O_WRONLY | O_TRUNC | O_CREAT;
 393                         if ((option_mask32 & (TFTPD_OPT+TFTPD_OPT_c)) == TFTPD_OPT) {
 394                                 /* tftpd without -c */
 395                                 open_mode = O_WRONLY | O_TRUNC;
 396                         }
 397                 }
 398                 local_fd = open(local_file, open_mode, 0666);
 399                 if (local_fd < 0) {
 400                         /* sanitize name, it came from untrusted remote side */
 401                         unsigned char *p = (void *) local_file;
 402                         while (*p) {
 403                                 if (*p < ' ')
 404                                         *p = '?';
 405                                 p++;
 406                         }
 407                         bb_perror_msg("can't open '%s'", local_file);
 408                         G_error_pkt_reason = ERR_NOFILE;
 409                         strcpy(G_error_pkt_str, "can't open file");
 410                         goto send_err_pkt_nomsg;
 411                 }
 412
 413 /* gcc 4.3.1 would NOT optimize it out as it should! */
 414 #if ENABLE_FEATURE_TFTP_BLOCKSIZE
 415                 if (blksize != TFTP_BLKSIZE_DEFAULT || want_transfer_size) {
 416                         /* Create and send OACK packet. */
 417                         /* For the download case, block_nr is still 1 -
 418                          * we expect 1st ACK from peer to be for (block_nr-1),
 419                          * that is, for "block 0" which is our OACK pkt */
 420                         opcode = TFTP_OACK;
 421                         goto add_blksize_opt;
 422                 }
 423 #endif
 424                 if (CMD_GET(option_mask32)) {
 425                         /* It's upload and we don't send OACK.
 426                          * We must ACK 1st packet (with filename)
 427                          * as if it is "block 0" */
 428                         block_nr = 0;
 429                 }
 430         } else { /* tftp */
 431                 if (CMD_PUT(option_mask32)) {
 432                         local_fd = STDIN_FILENO;
 433                         if (local_file)
 434                                 local_fd = xopen(local_file, O_RDONLY);
 435                 }
 436 /* Removing #if, or using if() statement instead of #if may lead to
 437  * "warning: null argument where non-null required": */
 438 #if ENABLE_TFTP
 439                 /* tftp */
 440
 441                 /* We can't (and don't really need to) bind the socket:
 442                  * we don't know from which local IP datagrams will be sent,
 443                  * but kernel will pick the same IP every time (unless routing
 444                  * table is changed), thus peer will see dgrams consistently
 445                  * coming from the same IP.
 446                  * We would like to connect the socket, but since peer's
 447                  * UDP code can be less perfect than ours, _peer's_ IP:port
 448                  * in replies may differ from IP:port we used to send
 449                  * our first packet. We can connect() only when we get
 450                  * first reply. */
 451
 452                 /* build opcode */
 453                 opcode = TFTP_WRQ;
 454                 if (CMD_GET(option_mask32)) {
 455                         opcode = TFTP_RRQ;
 456                 }
 457                 /* add filename and mode */
 458                 /* fill in packet if the filename fits into xbuf */
 459                 len = strlen(remote_file);
 460                 if (len + 3 + sizeof("octet") >= io_bufsize) {
 461                         bb_simple_error_msg("remote filename is too long");
 462                         goto ret;
 463                 }
 464                 cp = stpcpy(cp, remote_file) + 1;
 465                 /* add "mode" part of the packet */
 466                 cp = stpcpy(cp, "octet") + 1;
 467
 468 # if ENABLE_FEATURE_TFTP_BLOCKSIZE
 469                 if (blksize == TFTP_BLKSIZE_DEFAULT && !want_transfer_size)
 470                         goto send_pkt;
 471
 472                 /* Need to add option to pkt */
 473                 if ((&xbuf[io_bufsize - 1] - cp) < sizeof("blksize NNNNN tsize ") + sizeof(off_t)*3) {
 474                         bb_simple_error_msg("remote filename is too long");
 475                         goto ret;
 476                 }
 477                 expect_OACK = 1;
 478 # endif
 479 #endif /* ENABLE_TFTP */
 480
 481 #if ENABLE_FEATURE_TFTP_BLOCKSIZE
 482  add_blksize_opt:
 483                 if (blksize != TFTP_BLKSIZE_DEFAULT) {
 484                         /* add "blksize", <nul>, blksize, <nul> */
 485                         strcpy(cp, "blksize");
 486                         cp += sizeof("blksize");
 487                         cp += snprintf(cp, 6, "%d", blksize) + 1;
 488                 }
 489                 if (want_transfer_size) {
 490                         /* add "tsize", <nul>, size, <nul> (see RFC2349) */
 491                         /* if tftp and downloading, we send "0" (local_fd is not open yet)
 492                          * and this makes server to send "tsize" option with the size */
 493                         /* if tftp and uploading, we send file size (maybe dont, to not confuse old servers???) */
 494                         /* if tftpd and downloading, we are answering to client's request */
 495                         /* if tftpd and uploading: !want_transfer_size, this code is not executed */
 496                         struct stat st;
 497                         strcpy(cp, "tsize");
 498                         cp += sizeof("tsize");
 499                         st.st_size = 0;
 500                         if (local_fd >= 0)
 501                                 fstat(local_fd, &st);
 502                         cp += sprintf(cp, "%"OFF_FMT"u", (off_t)st.st_size) + 1;
 503 # if ENABLE_FEATURE_TFTP_PROGRESS_BAR
 504                         /* Save for progress bar. If 0 (tftp downloading),
 505                          * we look at server's reply later */
 506                         G.size = st.st_size;
 507                         if (remote_file && st.st_size)
 508                                 tftp_progress_init();
 509 # endif
 510                 }
 511 #endif
 512                 /* First packet is built, so skip packet generation */
 513                 goto send_pkt;
 514         }
 515
 516         /* Using mostly goto's - continue/break will be less clear
 517          * in where we actually jump to */
 518         while (1) {
 519                 /* Build ACK or DATA */
 520                 cp = xbuf + 2;
 521                 *((uint16_t*)cp) = htons(block_nr);
 522                 cp += 2;
 523                 block_nr++;
 524                 opcode = TFTP_ACK;
 525                 if (CMD_PUT(option_mask32)) {
 526                         opcode = TFTP_DATA;
 527                         len = full_read(local_fd, cp, blksize);
 528                         if (len < 0) {
 529                                 goto send_read_err_pkt;
 530                         }
 531                         if (len != blksize) {
 532                                 finished = 1;
 533                         }
 534                         cp += len;
 535                         IF_FEATURE_TFTP_PROGRESS_BAR(G.pos += len;)
 536                 }
 537  send_pkt:
 538                 /* Send packet */
 539                 *((uint16_t*)xbuf) = htons(opcode); /* fill in opcode part */
 540                 send_len = cp - xbuf;
 541                 /* NB: send_len value is preserved in code below
 542                  * for potential resend */
 543
 544                 retries = TFTP_NUM_RETRIES;  /* re-initialize */
 545                 waittime_ms = TFTP_TIMEOUT_MS;
 546
 547  send_again:
 548 #if ENABLE_TFTP_DEBUG
 549                 fprintf(stderr, "sending %u bytes\n", send_len);
 550                 for (cp = xbuf; cp < &xbuf[send_len]; cp++)
 551                         fprintf(stderr, "%02x ", (unsigned char) *cp);
 552                 fprintf(stderr, "\n");
 553 #endif
 554                 xsendto(socket_fd, xbuf, send_len, &peer_lsa->u.sa, peer_lsa->len);
 555
 556 #if ENABLE_FEATURE_TFTP_PROGRESS_BAR
 557                 if (is_bb_progress_inited(&G.pmt))
 558                         tftp_progress_update();
 559 #endif
 560                 /* Was it final ACK? then exit */
 561                 if (finished && (opcode == TFTP_ACK))
 562                         goto ret;
 563
 564  recv_again:
 565                 /* Receive packet */
 566                 /*pfd[0].fd = socket_fd;*/
 567                 pfd[0].events = POLLIN;
 568                 switch (safe_poll(pfd, 1, waittime_ms)) {
 569                 default:
 570                         /*bb_perror_msg("poll"); - done in safe_poll */
 571                         goto ret;
 572                 case 0:
 573                         retries--;
 574                         if (retries == 0) {
 575                                 tftp_progress_done();
 576                                 bb_simple_error_msg("timeout");
 577                                 goto ret; /* no err packet sent */
 578                         }
 579
 580                         /* exponential backoff with limit */
 581                         waittime_ms += waittime_ms/2;
 582                         if (waittime_ms > TFTP_MAXTIMEOUT_MS) {
 583                                 waittime_ms = TFTP_MAXTIMEOUT_MS;
 584                         }
 585
 586                         goto send_again; /* resend last sent pkt */
 587                 case 1:
 588                         if (!our_lsa) {
 589                                 /* tftp (not tftpd!) receiving 1st packet */
 590                                 our_lsa = ((void*)(ptrdiff_t)-1); /* not NULL */
 591                                 len = recvfrom(socket_fd, rbuf, io_bufsize, 0,
 592                                                 &peer_lsa->u.sa, &peer_lsa->len);
 593                                 /* Our first dgram went to port 69
 594                                  * but reply may come from different one.
 595                                  * Remember and use this new port (and IP) */
 596                                 if (len >= 0)
 597                                         xconnect(socket_fd, &peer_lsa->u.sa, peer_lsa->len);
 598                         } else {
 599                                 /* tftpd, or not the very first packet:
 600                                  * socket is connect()ed, can just read from it. */
 601                                 /* Don't full_read()!
 602                                  * This is not TCP, one read == one pkt! */
 603                                 len = safe_read(socket_fd, rbuf, io_bufsize);
 604                         }
 605                         if (len < 0) {
 606                                 goto send_read_err_pkt;
 607                         }
 608                         if (len < 4) { /* too small? */
 609                                 goto recv_again;
 610                         }
 611                 }
 612
 613                 /* Process recv'ed packet */
 614                 opcode = ntohs( ((uint16_t*)rbuf)[0] );
 615                 recv_blk = ntohs( ((uint16_t*)rbuf)[1] );
 616 #if ENABLE_TFTP_DEBUG
 617                 fprintf(stderr, "received %d bytes: %04x %04x\n", len, opcode, recv_blk);
 618 #endif
 619                 if (opcode == TFTP_ERROR) {
 620                         static const char errcode_str[] ALIGN1 =
 621                                 "\0"
 622                                 "file not found\0"
 623                                 "access violation\0"
 624                                 "disk full\0"
 625                                 "bad operation\0"
 626                                 "unknown transfer id\0"
 627                                 "file already exists\0"
 628                                 "no such user\0"
 629                                 "bad option";
 630
 631                         const char *msg = "";
 632
 633                         if (len > 4 && rbuf[4] != '\0') {
 634                                 msg = &rbuf[4];
 635                                 rbuf[io_bufsize - 1] = '\0'; /* paranoia */
 636                         } else if (recv_blk <= 8) {
 637                                 msg = nth_string(errcode_str, recv_blk);
 638                         }
 639                         bb_error_msg("server error: (%u) %s", recv_blk, msg);
 640                         goto ret;
 641                 }
 642
 643 #if ENABLE_FEATURE_TFTP_BLOCKSIZE
 644                 if (expect_OACK) {
 645                         expect_OACK = 0;
 646                         if (opcode == TFTP_OACK) {
 647                                 /* server seems to support options */
 648                                 char *res;
 649
 650                                 res = tftp_get_option("blksize", &rbuf[2], len - 2);
 651                                 if (res) {
 652                                         blksize = tftp_blksize_check(res, blksize);
 653                                         if (blksize < 0) {
 654                                                 G_error_pkt_reason = ERR_BAD_OPT;
 655                                                 goto send_err_pkt;
 656                                         }
 657                                         io_bufsize = blksize + 4;
 658                                 }
 659 # if ENABLE_FEATURE_TFTP_PROGRESS_BAR
 660                                 if (remote_file && G.size == 0) { /* if we don't know it yet */
 661                                         res = tftp_get_option("tsize", &rbuf[2], len - 2);
 662                                         if (res) {
 663                                                 G.size = bb_strtoull(res, NULL, 10);
 664                                                 if (G.size)
 665                                                         tftp_progress_init();
 666                                         }
 667                                 }
 668 # endif
 669                                 if (CMD_GET(option_mask32)) {
 670                                         /* We'll send ACK for OACK,
 671                                          * such ACK has "block no" of 0 */
 672                                         block_nr = 0;
 673                                 }
 674                                 continue;
 675                         }
 676                         /* rfc2347:
 677                          * "An option not acknowledged by the server
 678                          * must be ignored by the client and server
 679                          * as if it were never requested." */
 680                         if (blksize != TFTP_BLKSIZE_DEFAULT)
 681                                 bb_simple_error_msg("falling back to blocksize "TFTP_BLKSIZE_DEFAULT_STR);
 682                         blksize = TFTP_BLKSIZE_DEFAULT;
 683                         io_bufsize = TFTP_BLKSIZE_DEFAULT + 4;
 684                 }
 685 #endif
 686                 /* block_nr is already advanced to next block# we expect
 687                  * to get / block# we are about to send next time */
 688
 689                 if (CMD_GET(option_mask32) && (opcode == TFTP_DATA)) {
 690                         if (recv_blk == block_nr) {
 691                                 int sz;
 692                                 if (local_fd == -1) {
 693                                         local_fd = STDOUT_FILENO;
 694                                         if (local_file)
 695                                                 local_fd = xopen(local_file, O_WRONLY | O_TRUNC | O_CREAT);
 696                                 }
 697                                 sz = full_write(local_fd, &rbuf[4], len - 4);
 698                                 if (sz != len - 4) {
 699                                         strcpy(G_error_pkt_str, bb_msg_write_error);
 700                                         G_error_pkt_reason = ERR_WRITE;
 701                                         goto send_err_pkt;
 702                                 }
 703                                 if (sz != blksize) {
 704                                         finished = 1;
 705                                 }
 706                                 IF_FEATURE_TFTP_PROGRESS_BAR(G.pos += sz;)
 707                                 continue; /* send ACK */
 708                         }
 709 /* Disabled to cope with servers with Sorcerer's Apprentice Syndrome */
 710 #if 0
 711                         if (recv_blk == (block_nr - 1)) {
 712                                 /* Server lost our TFTP_ACK.  Resend it */
 713                                 block_nr = recv_blk;
 714                                 continue;
 715                         }
 716 #endif
 717                 }
 718
 719                 if (CMD_PUT(option_mask32) && (opcode == TFTP_ACK)) {
 720                         /* did peer ACK our last DATA pkt? */
 721                         if (recv_blk == (uint16_t) (block_nr - 1)) {
 722                                 if (finished)
 723                                         goto ret;
 724                                 continue; /* send next block */
 725                         }
 726                 }
 727                 /* Awww... recv'd packet is not recognized! */
 728                 goto recv_again;
 729                 /* why recv_again? - rfc1123 says:
 730                  * "The sender (i.e., the side originating the DATA packets)
 731                  *  must never resend the current DATA packet on receipt
 732                  *  of a duplicate ACK".
 733                  * DATA pkts are resent ONLY on timeout.
 734                  * Thus "goto send_again" will be a bad mistake above.
 735                  * See:
 736                  * http://en.wikipedia.org/wiki/Sorcerer's_Apprentice_Syndrome
 737                  */
 738         } /* end of "while (1)" */
 739  ret:
 740         if (ENABLE_FEATURE_CLEAN_UP) {
 741                 close(local_fd);
 742                 close(socket_fd);
 743                 free(xbuf);
 744                 free(rbuf);
 745         }
 746         if (!finished)
 747                 goto err;
 748         return EXIT_SUCCESS;
 749
 750  send_read_err_pkt:
 751         strcpy(G_error_pkt_str, bb_msg_read_error);
 752  send_err_pkt:
 753         if (G_error_pkt_str[0])
 754                 bb_simple_error_msg(G_error_pkt_str);
 755  send_err_pkt_nomsg:
 756         G.error_pkt[1] = TFTP_ERROR;
 757         xsendto(socket_fd, G.error_pkt, 4 + 1 + strlen(G_error_pkt_str),
 758                         &peer_lsa->u.sa, peer_lsa->len);
 759  err:
 760         if (local_fd >= 0 && CMD_GET(option_mask32) && local_file)
 761                 unlink(local_file);
 762         return EXIT_FAILURE;
 763 #undef remote_file
 764 }
 765
 766 #if ENABLE_TFTP
 767 int tftp_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
 768 int tftp_main(int argc UNUSED_PARAM, char **argv)
 769 {
 770         len_and_sockaddr *peer_lsa;
 771         const char *local_file = NULL;
 772         const char *remote_file = NULL;
 773 # if ENABLE_FEATURE_TFTP_BLOCKSIZE
 774         const char *blksize_str = TFTP_BLKSIZE_DEFAULT_STR;
 775         int blksize;
 776 # endif
 777         int result;
 778         int port;
 779
 780         INIT_G();
 781
 782         if (ENABLE_FEATURE_TFTP_HPA_COMPAT) {
 783                 /* As of 2019, common tftp client in Linux distros
 784                  * is one maintained by H. Peter Anvin:
 785                  * I've seen "tftp-hpa 5.2" version.
 786                  * Make the following command work:
 787                  *  "tftp HOST [PORT] -m binary -c get/put FILE"
 788                  * by mangling it into "....... -g/-p -r FILE"
 789                  * and accepting and ignoring -m STR option.
 790                  */
 791                 unsigned i = 1;
 792                 while (argv[i]) {
 793                         /* Accept not only -c, but also
 794                          * -lc, -cl, -llcclcllcc etc:
 795                          * "-l Literal mode (do not recognize HOST:FILE)"
 796                          * since we do not recognize that syntax anyway,
 797                          * might as well allow the option.
 798                          */
 799                         if (argv[i][0] == '-' && strchr(argv[i], 'c')
 800                          /*&& argv[i][1+strspn(argv[i]+1, "lc")] == '\0'*/
 801                         ) {
 802                                 if (!argv[++i])
 803                                         break;
 804                                 if (strcmp(argv[i], "get") == 0) {
 805                                         argv[i-1] = (char*)"-g";
 806                                         argv[i] = (char*)"-r";
 807                                         break;
 808                                 }
 809                                 if (strcmp(argv[i], "put") == 0) {
 810                                         argv[i-1] = (char*)"-p";
 811                                         argv[i] = (char*)"-r";
 812                                         break;
 813                                 }
 814                         }
 815                         i++;
 816                 }
 817         }
 818
 819         getopt32(argv, "^"
 820                         IF_FEATURE_TFTP_GET("g") IF_FEATURE_TFTP_PUT("p")
 821                         "l:r:" IF_FEATURE_TFTP_BLOCKSIZE("b:")
 822                         IF_FEATURE_TFTP_HPA_COMPAT("m:")
 823                         "\0"
 824                         /* -p or -g is mandatory, and they are mutually exclusive */
 825                         IF_FEATURE_TFTP_GET("g:") IF_FEATURE_TFTP_PUT("p:")
 826                         IF_GETPUT("g--p:p--g:"),
 827                         &local_file, &remote_file
 828                         IF_FEATURE_TFTP_BLOCKSIZE(, &blksize_str)
 829                         IF_FEATURE_TFTP_HPA_COMPAT(, NULL)
 830         );
 831         argv += optind;
 832
 833 # if ENABLE_FEATURE_TFTP_BLOCKSIZE
 834         /* Check if the blksize is valid:
 835          * RFC2348 says between 8 and 65464 */
 836         blksize = tftp_blksize_check(blksize_str, 65564);
 837         if (blksize < 0) {
 838                 //bb_error_msg("bad block size");
 839                 return EXIT_FAILURE;
 840         }
 841 # endif
 842
 843         if (remote_file) {
 844                 if (!local_file) {
 845                         const char *slash = strrchr(remote_file, '/');
 846                         local_file = slash ? slash + 1 : remote_file;
 847                 }
 848         } else {
 849                 remote_file = local_file;
 850         }
 851
 852         /* Error if filename or host is not known */
 853         if (!remote_file || !argv[0])
 854                 bb_show_usage();
 855
 856         port = bb_lookup_port(argv[1], "udp", 69);
 857         peer_lsa = xhost2sockaddr(argv[0], port);
 858
 859 # if ENABLE_TFTP_DEBUG
 860         fprintf(stderr, "using server '%s', remote_file '%s', local_file '%s'\n",
 861                         xmalloc_sockaddr2dotted(&peer_lsa->u.sa),
 862                         remote_file, local_file);
 863 # endif
 864
 865 # if ENABLE_FEATURE_TFTP_PROGRESS_BAR
 866         G.file = remote_file;
 867 # endif
 868         result = tftp_protocol(
 869                 NULL /*our_lsa*/, peer_lsa,
 870                 (LONE_DASH(local_file) ? NULL : local_file), remote_file
 871                 IF_FEATURE_TFTP_BLOCKSIZE(, 1 /* want_transfer_size */)
 872                 IF_FEATURE_TFTP_BLOCKSIZE(, blksize)
 873         );
 874         tftp_progress_done();
 875
 876         return result;
 877 }
 878 #endif /* ENABLE_TFTP */
 879
 880 #if ENABLE_TFTPD
 881 int tftpd_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
 882 int tftpd_main(int argc UNUSED_PARAM, char **argv)
 883 {
 884         len_and_sockaddr *our_lsa;
 885         len_and_sockaddr *peer_lsa;
 886         char *mode, *user_opt;
 887         char *local_file = local_file;
 888         const char *error_msg;
 889         int opt, result, opcode;
 890         IF_FEATURE_TFTP_BLOCKSIZE(int blksize = TFTP_BLKSIZE_DEFAULT;)
 891         IF_FEATURE_TFTP_BLOCKSIZE(int want_transfer_size = 0;)
 892
 893         INIT_G();
 894
 895         our_lsa = get_sock_lsa(STDIN_FILENO);
 896         if (!our_lsa) {
 897                 /* This is confusing:
 898                  *bb_error_msg_and_die("stdin is not a socket");
 899                  * Better: */
 900                 bb_show_usage();
 901                 /* Help text says that tftpd must be used as inetd service,
 902                  * which is by far the most usual cause of get_sock_lsa
 903                  * failure */
 904         }
 905         peer_lsa = xzalloc(LSA_LEN_SIZE + our_lsa->len);
 906         peer_lsa->len = our_lsa->len;
 907
 908         /* Shifting to not collide with TFTP_OPTs */
 909         opt = option_mask32 = TFTPD_OPT | (getopt32(argv, "rcu:l", &user_opt) << 8);
 910         argv += optind;
 911         if (opt & TFTPD_OPT_l) {
 912                 openlog(applet_name, LOG_PID, LOG_DAEMON);
 913                 logmode = LOGMODE_SYSLOG;
 914         }
 915         if (opt & TFTPD_OPT_u) {
 916                 /* Must be before xchroot */
 917                 G.pw = xgetpwnam(user_opt);
 918         }
 919         if (argv[0]) {
 920                 xchroot(argv[0]);
 921         }
 922
 923         result = recv_from_to(STDIN_FILENO,
 924                         G.block_buf, sizeof(G.block_buf) + 1,
 925                         /* ^^^ sizeof+1 to reliably detect oversized input */
 926                         0 /* flags */,
 927                         &peer_lsa->u.sa, &our_lsa->u.sa, our_lsa->len);
 928
 929         error_msg = "malformed packet";
 930         opcode = ntohs(*(uint16_t*)G.block_buf);
 931         if (result < 4 || result > sizeof(G.block_buf)
 932         /*|| G.block_buf[result-1] != '\0' - bug compatibility, see below */
 933          || (IF_FEATURE_TFTP_PUT(opcode != TFTP_RRQ) /* not download */
 934              IF_GETPUT(&&)
 935              IF_FEATURE_TFTP_GET(opcode != TFTP_WRQ) /* not upload */
 936             )
 937         ) {
 938                 goto err;
 939         }
 940         /* Some HP PA-RISC firmware always sends fixed 516-byte requests,
 941          * with trailing garbage.
 942          * Support that by not requiring NUL to be the last byte (see above).
 943          * To make strXYZ() ops safe, force NUL termination:
 944          */
 945         G.block_buf_tail[0] = '\0';
 946
 947         local_file = G.block_buf + 2;
 948         if (local_file[0] == '.' || strstr(local_file, "/.")) {
 949                 error_msg = "dot in file name";
 950                 goto err;
 951         }
 952         mode = local_file + strlen(local_file) + 1;
 953         /* RFC 1350 says mode string is case independent */
 954         if (mode >= G.block_buf + result || strcasecmp(mode, "octet") != 0) {
 955                 error_msg = "mode is not 'octet'";
 956                 goto err;
 957         }
 958 # if ENABLE_FEATURE_TFTP_BLOCKSIZE
 959         {
 960                 char *res;
 961                 char *opt_str = mode + sizeof("octet");
 962                 int opt_len = G.block_buf + result - opt_str;
 963                 if (opt_len > 0) {
 964                         res = tftp_get_option("blksize", opt_str, opt_len);
 965                         if (res) {
 966                                 blksize = tftp_blksize_check(res, 65564);
 967                                 if (blksize < 0) {
 968                                         G_error_pkt_reason = ERR_BAD_OPT;
 969                                         /* will just send error pkt */
 970                                         goto do_proto;
 971                                 }
 972                         }
 973                         if (opcode != TFTP_WRQ /* download? */
 974                         /* did client ask us about file size? */
 975                          && tftp_get_option("tsize", opt_str, opt_len)
 976                         ) {
 977                                 want_transfer_size = 1;
 978                         }
 979                 }
 980         }
 981 # endif
 982
 983         if (!ENABLE_FEATURE_TFTP_PUT || opcode == TFTP_WRQ) {
 984                 if (opt & TFTPD_OPT_r) {
 985                         /* This would mean "disk full" - not true */
 986                         /*G_error_pkt_reason = ERR_WRITE;*/
 987                         error_msg = bb_msg_write_error;
 988                         goto err;
 989                 }
 990                 IF_GETPUT(option_mask32 |= TFTP_OPT_GET;) /* will receive file's data */
 991         } else {
 992                 IF_GETPUT(option_mask32 |= TFTP_OPT_PUT;) /* will send file's data */
 993         }
 994
 995         /* NB: if G_error_pkt_str or G_error_pkt_reason is set up,
 996          * tftp_protocol() just sends one error pkt and returns */
 997
 998  do_proto:
 999         close(STDIN_FILENO); /* close old, possibly wildcard socket */
1000         /* tftp_protocol() will create new one, bound to particular local IP */
1001         result = tftp_protocol(
1002                 our_lsa, peer_lsa,
1003                 local_file
1004                 IF_TFTP(, NULL /*remote_file*/)
1005                 IF_FEATURE_TFTP_BLOCKSIZE(, want_transfer_size)
1006                 IF_FEATURE_TFTP_BLOCKSIZE(, blksize)
1007         );
1008
1009         return result;
1010  err:
1011         strcpy(G_error_pkt_str, error_msg);
1012         goto do_proto;
1013 }
1014 #endif /* ENABLE_TFTPD */
1015
1016 #endif /* ENABLE_FEATURE_TFTP_GET || ENABLE_FEATURE_TFTP_PUT */