miscutils/rx.c

   1 /* vi: set sw=4 ts=4: */
   2 /*
   3  * Copyright:     Copyright (C) 2001, Hewlett-Packard Company
   4  * Author:        Christopher Hoover <ch@hpl.hp.com>
   5  * Description:   xmodem functionality for uploading of kernels
   6  *                and the like
   7  * Created at:    Thu Dec 20 01:58:08 PST 2001
   8  *
   9  * xmodem functionality for uploading of kernels and the like
  10  *
  11  * Copyright (C) 2001 Hewlett-Packard Laboratories
  12  *
  13  * Licensed under GPLv2 or later, see file LICENSE in this source tree.
  14  *
  15  * This was originally written for blob and then adapted for busybox.
  16  */
  17 //config:config RX
  18 //config:       bool "rx (2.9 kb)"
  19 //config:       default y
  20 //config:       select PLATFORM_LINUX
  21 //config:       help
  22 //config:       Receive files using the Xmodem protocol.
  23
  24 //applet:IF_RX(APPLET(rx, BB_DIR_USR_BIN, BB_SUID_DROP))
  25
  26 //kbuild:lib-$(CONFIG_RX) += rx.o
  27
  28 //usage:#define rx_trivial_usage
  29 //usage:       "FILE"
  30 //usage:#define rx_full_usage "\n\n"
  31 //usage:       "Receive a file using the xmodem protocol"
  32 //usage:
  33 //usage:#define rx_example_usage
  34 //usage:       "$ rx /tmp/foo\n"
  35
  36 #include "libbb.h"
  37
  38 #define SOH 0x01
  39 #define STX 0x02
  40 #define EOT 0x04
  41 #define ACK 0x06
  42 #define NAK 0x15
  43 #define BS  0x08
  44 #define PAD 0x1A
  45
  46 /*
  47 Cf:
  48   http://www.textfiles.com/apple/xmodem
  49   http://www.phys.washington.edu/~belonis/xmodem/docxmodem.txt
  50   http://www.phys.washington.edu/~belonis/xmodem/docymodem.txt
  51   http://www.phys.washington.edu/~belonis/xmodem/modmprot.col
  52 */
  53
  54 #define TIMEOUT 1
  55 #define TIMEOUT_LONG 10
  56 #define MAXERRORS 10
  57
  58 #define read_fd  STDIN_FILENO
  59 #define write_fd STDOUT_FILENO
  60
  61 static int read_byte(unsigned timeout)
  62 {
  63         unsigned char buf;
  64         int n;
  65
  66         alarm(timeout);
  67         /* NOT safe_read! We want ALRM to interrupt us */
  68         n = read(read_fd, &buf, 1);
  69         alarm(0);
  70         if (n == 1)
  71                 return buf;
  72         return -1;
  73 }
  74
  75 static int receive(/*int read_fd, */int file_fd)
  76 {
  77         unsigned char blockBuf[1024];
  78         unsigned blockLength = 0;
  79         unsigned errors = 0;
  80         unsigned wantBlockNo = 1;
  81         unsigned length = 0;
  82         int do_crc = 1;
  83         char reply_char;
  84         unsigned timeout = TIMEOUT_LONG;
  85
  86         /* Flush pending input */
  87         tcflush(read_fd, TCIFLUSH);
  88
  89         /* Ask for CRC; if we get errors, we will go with checksum */
  90         reply_char = 'C';
  91         full_write(write_fd, &reply_char, 1);
  92
  93         for (;;) {
  94                 int blockBegin;
  95                 int blockNo, blockNoOnesCompl;
  96                 int cksum_or_crc;
  97                 unsigned expected;
  98                 int i, j;
  99
 100                 blockBegin = read_byte(timeout);
 101                 if (blockBegin < 0)
 102                         goto timeout;
 103
 104                 /* If last block, remove padding */
 105                 if (blockBegin == EOT) {
 106                         /* Data blocks can be padded with ^Z characters */
 107                         /* This code tries to detect and remove them */
 108                         if (blockLength >= 3
 109                          && blockBuf[blockLength - 1] == PAD
 110                          && blockBuf[blockLength - 2] == PAD
 111                          && blockBuf[blockLength - 3] == PAD
 112                         ) {
 113                                 while (blockLength
 114                                     && blockBuf[blockLength - 1] == PAD
 115                                 ) {
 116                                         blockLength--;
 117                                 }
 118                         }
 119                 }
 120                 /* Write previously received block */
 121                 errno = 0;
 122                 if (full_write(file_fd, blockBuf, blockLength) != blockLength) {
 123                         bb_perror_msg(bb_msg_write_error);
 124                         goto fatal;
 125                 }
 126
 127                 timeout = TIMEOUT;
 128                 reply_char = NAK;
 129
 130                 switch (blockBegin) {
 131                 case SOH:
 132                 case STX:
 133                         break;
 134                 case EOT:
 135                         reply_char = ACK;
 136                         full_write(write_fd, &reply_char, 1);
 137                         return length;
 138                 default:
 139                         goto error;
 140                 }
 141
 142                 /* Block no */
 143                 blockNo = read_byte(TIMEOUT);
 144                 if (blockNo < 0)
 145                         goto timeout;
 146
 147                 /* Block no, in one's complement form */
 148                 blockNoOnesCompl = read_byte(TIMEOUT);
 149                 if (blockNoOnesCompl < 0)
 150                         goto timeout;
 151
 152                 if (blockNo != (255 - blockNoOnesCompl)) {
 153                         bb_error_msg("bad block ones compl");
 154                         goto error;
 155                 }
 156
 157                 blockLength = (blockBegin == SOH) ? 128 : 1024;
 158
 159                 for (i = 0; i < blockLength; i++) {
 160                         int cc = read_byte(TIMEOUT);
 161                         if (cc < 0)
 162                                 goto timeout;
 163                         blockBuf[i] = cc;
 164                 }
 165
 166                 cksum_or_crc = read_byte(TIMEOUT);
 167                 if (cksum_or_crc < 0)
 168                         goto timeout;
 169                 if (do_crc) {
 170                         cksum_or_crc = (cksum_or_crc << 8) | read_byte(TIMEOUT);
 171                         if (cksum_or_crc < 0)
 172                                 goto timeout;
 173                 }
 174
 175                 if (blockNo == ((wantBlockNo - 1) & 0xff)) {
 176                         /* a repeat of the last block is ok, just ignore it. */
 177                         /* this also ignores the initial block 0 which is */
 178                         /* meta data. */
 179                         blockLength = 0;
 180                         goto next;
 181                 }
 182                 if (blockNo != (wantBlockNo & 0xff)) {
 183                         bb_error_msg("unexpected block no, 0x%08x, expecting 0x%08x", blockNo, wantBlockNo);
 184                         goto error;
 185                 }
 186
 187                 expected = 0;
 188                 if (do_crc) {
 189                         for (i = 0; i < blockLength; i++) {
 190                                 expected = expected ^ blockBuf[i] << 8;
 191                                 for (j = 0; j < 8; j++) {
 192                                         if (expected & 0x8000)
 193                                                 expected = (expected << 1) ^ 0x1021;
 194                                         else
 195                                                 expected = (expected << 1);
 196                                 }
 197                         }
 198                         expected &= 0xffff;
 199                 } else {
 200                         for (i = 0; i < blockLength; i++)
 201                                 expected += blockBuf[i];
 202                         expected &= 0xff;
 203                 }
 204                 if (cksum_or_crc != expected) {
 205                         bb_error_msg(do_crc ? "crc error, expected 0x%04x, got 0x%04x"
 206                                         : "checksum error, expected 0x%02x, got 0x%02x",
 207                                 expected, cksum_or_crc);
 208                         goto error;
 209                 }
 210
 211                 wantBlockNo++;
 212                 length += blockLength;
 213  next:
 214                 errors = 0;
 215                 reply_char = ACK;
 216                 full_write(write_fd, &reply_char, 1);
 217                 continue;
 218  error:
 219  timeout:
 220                 blockLength = 0;
 221                 errors++;
 222                 if (errors == MAXERRORS) {
 223                         /* Abort */
 224
 225                         /* If were asking for crc, try again w/o crc */
 226                         if (reply_char == 'C') {
 227                                 reply_char = NAK;
 228                                 errors = 0;
 229                                 do_crc = 0;
 230                                 goto timeout;
 231                         }
 232                         bb_error_msg("too many errors; giving up");
 233  fatal:
 234                         /* 5 CAN followed by 5 BS. Don't try too hard... */
 235                         safe_write(write_fd, "\030\030\030\030\030\010\010\010\010\010", 10);
 236                         return -1;
 237                 }
 238
 239                 /* Flush pending input */
 240                 tcflush(read_fd, TCIFLUSH);
 241
 242                 full_write(write_fd, &reply_char, 1);
 243         } /* for (;;) */
 244 }
 245
 246 static void sigalrm_handler(int UNUSED_PARAM signum)
 247 {
 248 }
 249
 250 int rx_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
 251 int rx_main(int argc UNUSED_PARAM, char **argv)
 252 {
 253         struct termios tty, orig_tty;
 254         int termios_err;
 255         int file_fd;
 256         int n;
 257
 258         /* Disabled by vda:
 259          * why we can't receive from stdin? Why we *require*
 260          * controlling tty?? */
 261         /*read_fd = xopen(CURRENT_TTY, O_RDWR);*/
 262         file_fd = xopen(single_argv(argv), O_RDWR|O_CREAT|O_TRUNC);
 263
 264         termios_err = tcgetattr(read_fd, &tty);
 265         if (termios_err == 0) {
 266 //TODO: use set_termios_to_raw()
 267                 orig_tty = tty;
 268                 cfmakeraw(&tty);
 269                 tcsetattr(read_fd, TCSAFLUSH, &tty);
 270         }
 271
 272         /* No SA_RESTART: we want ALRM to interrupt read() */
 273         signal_no_SA_RESTART_empty_mask(SIGALRM, sigalrm_handler);
 274
 275         n = receive(file_fd);
 276
 277         if (termios_err == 0)
 278                 tcsetattr(read_fd, TCSAFLUSH, &orig_tty);
 279         if (ENABLE_FEATURE_CLEAN_UP)
 280                 close(file_fd);
 281         fflush_stdout_and_exit(n >= 0);
 282 }