Lorenzo Colitti | 313379e | 2013-07-11 01:07:11 +0900 | [diff] [blame] | 1 | /* |
| 2 | * Copyright (c) 1983 Regents of the University of California. |
| 3 | * All rights reserved. |
| 4 | * |
| 5 | * Redistribution and use in source and binary forms, with or without |
| 6 | * modification, are permitted provided that the following conditions |
| 7 | * are met: |
| 8 | * 1. Redistributions of source code must retain the above copyright |
| 9 | * notice, this list of conditions and the following disclaimer. |
| 10 | * 2. Redistributions in binary form must reproduce the above copyright |
| 11 | * notice, this list of conditions and the following disclaimer in the |
| 12 | * documentation and/or other materials provided with the distribution. |
| 13 | * 3. All advertising materials mentioning features or use of this software |
| 14 | * must display the following acknowledgement: |
| 15 | * This product includes software developed by the University of |
| 16 | * California, Berkeley and its contributors. |
| 17 | * 4. Neither the name of the University nor the names of its contributors |
| 18 | * may be used to endorse or promote products derived from this software |
| 19 | * without specific prior written permission. |
| 20 | * |
| 21 | * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND |
| 22 | * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE |
| 23 | * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE |
| 24 | * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE |
| 25 | * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL |
| 26 | * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS |
| 27 | * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) |
| 28 | * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT |
| 29 | * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY |
| 30 | * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF |
| 31 | * SUCH DAMAGE. |
| 32 | */ |
| 33 | |
| 34 | #ifndef lint |
| 35 | char copyright[] = |
| 36 | "@(#) Copyright (c) 1983 Regents of the University of California.\n\ |
| 37 | All rights reserved.\n"; |
| 38 | #endif /* not lint */ |
| 39 | |
| 40 | #ifndef lint |
| 41 | /*static char sccsid[] = "from: @(#)tftpd.c 5.13 (Berkeley) 2/26/91";*/ |
| 42 | /*static char rcsid[] = "$Id: tftpd.c,v 1.3 1993/08/01 18:28:53 mycroft Exp $";*/ |
| 43 | #endif /* not lint */ |
| 44 | |
| 45 | /* |
| 46 | * Trivial file transfer protocol server. |
| 47 | * |
| 48 | * This version includes many modifications by Jim Guyton <guyton@rand-unix> |
| 49 | */ |
| 50 | |
| 51 | #include <sys/types.h> |
| 52 | #include <sys/ioctl.h> |
| 53 | #include <sys/stat.h> |
| 54 | #include <unistd.h> |
| 55 | #include <signal.h> |
| 56 | #include <fcntl.h> |
| 57 | |
| 58 | #include <sys/socket.h> |
| 59 | #include <netinet/in.h> |
| 60 | #include <netdb.h> |
| 61 | |
| 62 | #include <setjmp.h> |
| 63 | #include <syslog.h> |
| 64 | #include <stdio.h> |
| 65 | #include <errno.h> |
| 66 | #include <ctype.h> |
| 67 | #include <string.h> |
| 68 | #include <stdlib.h> |
| 69 | |
| 70 | #include "tftp.h" |
| 71 | |
| 72 | #ifndef MSG_CONFIRM |
| 73 | #define MSG_CONFIRM 0 |
| 74 | #warning Please, upgrade kernel, otherwise this tftpd has no advantages. |
| 75 | #endif |
| 76 | |
| 77 | #define TIMEOUT 5 |
| 78 | |
| 79 | int peer; |
| 80 | int rexmtval = TIMEOUT; |
| 81 | int maxtimeout = 5*TIMEOUT; |
| 82 | |
| 83 | #define PKTSIZE SEGSIZE+4 |
| 84 | char buf[PKTSIZE]; |
| 85 | char ackbuf[PKTSIZE]; |
| 86 | union { |
| 87 | struct sockaddr sa; |
| 88 | struct sockaddr_in sin; |
| 89 | struct sockaddr_in6 sin6; |
| 90 | } from; |
| 91 | socklen_t fromlen; |
| 92 | |
| 93 | #define MAXARG 1 |
| 94 | char *dirs[MAXARG+1]; |
| 95 | |
| 96 | void tftp(struct tftphdr *tp, int size) __attribute__((noreturn)); |
| 97 | void nak(int error); |
| 98 | int validate_access(char *filename, int mode); |
| 99 | |
| 100 | struct formats; |
| 101 | |
| 102 | void sendfile(struct formats *pf); |
| 103 | void recvfile(struct formats *pf); |
| 104 | |
| 105 | |
| 106 | int main(int ac, char **av) |
| 107 | { |
| 108 | register struct tftphdr *tp; |
| 109 | register int n = 0; |
| 110 | int on = 1; |
| 111 | |
| 112 | /* Sanity. If parent forgot to setuid() on us. */ |
| 113 | if (geteuid() == 0) { |
| 114 | setgid(65534); |
| 115 | setuid(65534); |
| 116 | } |
| 117 | |
| 118 | ac--; av++; |
| 119 | while (ac-- > 0 && n < MAXARG) |
| 120 | dirs[n++] = *av++; |
| 121 | |
| 122 | openlog("tftpd", LOG_PID, LOG_DAEMON); |
| 123 | if (ioctl(0, FIONBIO, &on) < 0) { |
| 124 | syslog(LOG_ERR, "ioctl(FIONBIO): %m\n"); |
| 125 | exit(1); |
| 126 | } |
| 127 | fromlen = sizeof (from); |
| 128 | n = recvfrom(0, buf, sizeof (buf), 0, |
| 129 | (struct sockaddr *)&from, &fromlen); |
| 130 | if (n < 0) { |
| 131 | if (errno != EAGAIN) |
| 132 | syslog(LOG_ERR, "recvfrom: %m\n"); |
| 133 | exit(1); |
| 134 | } |
| 135 | /* |
| 136 | * Now that we have read the message out of the UDP |
| 137 | * socket, we fork and exit. Thus, inetd will go back |
| 138 | * to listening to the tftp port, and the next request |
| 139 | * to come in will start up a new instance of tftpd. |
| 140 | * |
| 141 | * We do this so that inetd can run tftpd in "wait" mode. |
| 142 | * The problem with tftpd running in "nowait" mode is that |
| 143 | * inetd may get one or more successful "selects" on the |
| 144 | * tftp port before we do our receive, so more than one |
| 145 | * instance of tftpd may be started up. Worse, if tftpd |
| 146 | * break before doing the above "recvfrom", inetd would |
| 147 | * spawn endless instances, clogging the system. |
| 148 | */ |
| 149 | { |
| 150 | int pid; |
| 151 | int i; |
| 152 | socklen_t j; |
| 153 | |
| 154 | for (i = 1; i < 20; i++) { |
| 155 | pid = fork(); |
| 156 | if (pid < 0) { |
| 157 | sleep(i); |
| 158 | /* |
| 159 | * flush out to most recently sent request. |
| 160 | * |
| 161 | * This may drop some request, but those |
| 162 | * will be resent by the clients when |
| 163 | * they timeout. The positive effect of |
| 164 | * this flush is to (try to) prevent more |
| 165 | * than one tftpd being started up to service |
| 166 | * a single request from a single client. |
| 167 | */ |
| 168 | j = sizeof from; |
| 169 | i = recvfrom(0, buf, sizeof (buf), 0, |
| 170 | (struct sockaddr *)&from, &j); |
| 171 | if (i > 0) { |
| 172 | n = i; |
| 173 | fromlen = j; |
| 174 | } |
| 175 | } else { |
| 176 | break; |
| 177 | } |
| 178 | } |
| 179 | if (pid < 0) { |
| 180 | syslog(LOG_ERR, "fork: %m\n"); |
| 181 | exit(1); |
| 182 | } else if (pid != 0) { |
| 183 | exit(0); |
| 184 | } |
| 185 | } |
| 186 | alarm(0); |
| 187 | close(0); |
| 188 | close(1); |
| 189 | peer = socket(from.sa.sa_family, SOCK_DGRAM, 0); |
| 190 | if (peer < 0) { |
| 191 | syslog(LOG_ERR, "socket: %m\n"); |
| 192 | exit(1); |
| 193 | } |
| 194 | if (connect(peer, (struct sockaddr *)&from, sizeof(from)) < 0) { |
| 195 | syslog(LOG_ERR, "connect: %m\n"); |
| 196 | exit(1); |
| 197 | } |
| 198 | tp = (struct tftphdr *)buf; |
| 199 | tp->th_opcode = ntohs(tp->th_opcode); |
| 200 | if (tp->th_opcode == RRQ || tp->th_opcode == WRQ) |
| 201 | tftp(tp, n); |
| 202 | exit(1); |
| 203 | } |
| 204 | |
| 205 | struct formats { |
| 206 | char *f_mode; |
| 207 | int (*f_validate)(char *filename, int mode); |
| 208 | void (*f_send)(struct formats*); |
| 209 | void (*f_recv)(struct formats*); |
| 210 | int f_convert; |
| 211 | } formats[] = { |
| 212 | { "netascii", validate_access, sendfile, recvfile, 1 }, |
| 213 | { "octet", validate_access, sendfile, recvfile, 0 }, |
| 214 | #ifdef notdef |
| 215 | { "mail", validate_user, sendmail, recvmail, 1 }, |
| 216 | #endif |
| 217 | { 0 } |
| 218 | }; |
| 219 | |
| 220 | /* |
| 221 | * Handle initial connection protocol. |
| 222 | */ |
| 223 | void tftp(struct tftphdr *tp, int size) |
| 224 | { |
| 225 | register char *cp; |
| 226 | int first = 1, ecode; |
| 227 | register struct formats *pf; |
| 228 | char *filename, *mode = NULL; |
| 229 | |
| 230 | filename = cp = tp->th_stuff; |
| 231 | again: |
| 232 | while (cp < buf + size) { |
| 233 | if (*cp == '\0') |
| 234 | break; |
| 235 | cp++; |
| 236 | } |
| 237 | if (*cp != '\0') { |
| 238 | nak(EBADOP); |
| 239 | exit(1); |
| 240 | } |
| 241 | if (first) { |
| 242 | mode = ++cp; |
| 243 | first = 0; |
| 244 | goto again; |
| 245 | } |
| 246 | for (cp = mode; *cp; cp++) |
| 247 | if (isupper(*cp)) |
| 248 | *cp = tolower(*cp); |
| 249 | for (pf = formats; pf->f_mode; pf++) |
| 250 | if (strcmp(pf->f_mode, mode) == 0) |
| 251 | break; |
| 252 | if (pf->f_mode == 0) { |
| 253 | nak(EBADOP); |
| 254 | exit(1); |
| 255 | } |
| 256 | ecode = (*pf->f_validate)(filename, tp->th_opcode); |
| 257 | if (ecode) { |
| 258 | nak(ecode); |
| 259 | exit(1); |
| 260 | } |
| 261 | if (tp->th_opcode == WRQ) |
| 262 | (*pf->f_recv)(pf); |
| 263 | else |
| 264 | (*pf->f_send)(pf); |
| 265 | exit(0); |
| 266 | } |
| 267 | |
| 268 | |
| 269 | FILE *file; |
| 270 | |
| 271 | /* |
| 272 | * Validate file access. Since we |
| 273 | * have no uid or gid, for now require |
| 274 | * file to exist and be publicly |
| 275 | * readable/writable. |
| 276 | * If we were invoked with arguments |
| 277 | * from inetd then the file must also be |
| 278 | * in one of the given directory prefixes. |
| 279 | * Note also, full path name must be |
| 280 | * given as we have no login directory. |
| 281 | */ |
| 282 | int validate_access(char *filename, int mode) |
| 283 | { |
| 284 | struct stat stbuf; |
| 285 | int fd; |
| 286 | char *cp; |
| 287 | char fnamebuf[1024+512]; |
| 288 | |
| 289 | for (cp = filename; *cp; cp++) { |
| 290 | if(*cp == '.' && (cp == filename || strncmp(cp-1, "/../", 4) == 0)) { |
| 291 | syslog(LOG_ERR, "bad path %s", filename); |
| 292 | return(EACCESS); |
| 293 | } |
| 294 | } |
| 295 | |
| 296 | if (*filename == '/') |
| 297 | filename++; |
| 298 | |
| 299 | if (!*dirs) { |
| 300 | syslog(LOG_ERR, "no dirs"); |
| 301 | return EACCESS; |
| 302 | } |
| 303 | snprintf(fnamebuf, sizeof(fnamebuf)-1, "%s/%s", *dirs, filename); |
| 304 | filename = fnamebuf; |
| 305 | |
| 306 | if (stat(filename, &stbuf) < 0) { |
| 307 | syslog(LOG_ERR, "stat %s : %m", filename); |
| 308 | return (errno == ENOENT ? ENOTFOUND : EACCESS); |
| 309 | } |
| 310 | if (mode == RRQ) { |
| 311 | if ((stbuf.st_mode&(S_IREAD >> 6)) == 0) { |
| 312 | syslog(LOG_ERR, "not readable %s", filename); |
| 313 | return (EACCESS); |
| 314 | } |
| 315 | } else { |
| 316 | if ((stbuf.st_mode&(S_IWRITE >> 6)) == 0) { |
| 317 | syslog(LOG_ERR, "not writable %s", filename); |
| 318 | return (EACCESS); |
| 319 | } |
| 320 | } |
| 321 | fd = open(filename, mode == RRQ ? 0 : 1); |
| 322 | if (fd < 0) { |
| 323 | syslog(LOG_ERR, "cannot open %s: %m", filename); |
| 324 | return (errno + 100); |
| 325 | } |
| 326 | file = fdopen(fd, (mode == RRQ)? "r":"w"); |
| 327 | if (file == NULL) { |
| 328 | return errno+100; |
| 329 | } |
| 330 | return (0); |
| 331 | } |
| 332 | |
| 333 | int confirmed; |
| 334 | int timeout; |
| 335 | jmp_buf timeoutbuf; |
| 336 | |
| 337 | void timer(int signo) |
| 338 | { |
| 339 | confirmed = 0; |
| 340 | timeout += rexmtval; |
| 341 | if (timeout >= maxtimeout) |
| 342 | exit(1); |
| 343 | longjmp(timeoutbuf, 1); |
| 344 | } |
| 345 | |
| 346 | /* |
| 347 | * Send the requested file. |
| 348 | */ |
| 349 | void sendfile(struct formats *pf) |
| 350 | { |
| 351 | struct tftphdr *dp; |
| 352 | register struct tftphdr *ap; /* ack packet */ |
| 353 | volatile int block = 1; |
| 354 | int size, n; |
| 355 | |
| 356 | confirmed = 0; |
| 357 | signal(SIGALRM, timer); |
| 358 | dp = r_init(); |
| 359 | ap = (struct tftphdr *)ackbuf; |
| 360 | do { |
| 361 | size = readit(file, &dp, pf->f_convert); |
| 362 | if (size < 0) { |
| 363 | nak(errno + 100); |
| 364 | goto abort; |
| 365 | } |
| 366 | dp->th_opcode = htons((u_short)DATA); |
| 367 | dp->th_block = htons((u_short)block); |
| 368 | timeout = 0; |
| 369 | (void) setjmp(timeoutbuf); |
| 370 | |
| 371 | send_data: |
| 372 | if (send(peer, dp, size + 4, confirmed) != size + 4) { |
| 373 | syslog(LOG_ERR, "tftpd: write: %m\n"); |
| 374 | goto abort; |
| 375 | } |
| 376 | confirmed = 0; |
| 377 | read_ahead(file, pf->f_convert); |
| 378 | for ( ; ; ) { |
| 379 | alarm(rexmtval); /* read the ack */ |
| 380 | n = recv(peer, ackbuf, sizeof (ackbuf), 0); |
| 381 | alarm(0); |
| 382 | if (n < 0) { |
| 383 | syslog(LOG_ERR, "tftpd: read: %m\n"); |
| 384 | goto abort; |
| 385 | } |
| 386 | ap->th_opcode = ntohs((u_short)ap->th_opcode); |
| 387 | ap->th_block = ntohs((u_short)ap->th_block); |
| 388 | |
| 389 | if (ap->th_opcode == ERROR) |
| 390 | goto abort; |
| 391 | |
| 392 | if (ap->th_opcode == ACK) { |
| 393 | if (ap->th_block == block) { |
| 394 | confirmed = MSG_CONFIRM; |
| 395 | break; |
| 396 | } |
| 397 | /* Re-synchronize with the other side */ |
| 398 | synchnet(peer); |
| 399 | if (ap->th_block == (block -1)) { |
| 400 | goto send_data; |
| 401 | } |
| 402 | } |
| 403 | |
| 404 | } |
| 405 | block++; |
| 406 | } while (size == SEGSIZE); |
| 407 | abort: |
| 408 | (void) fclose(file); |
| 409 | } |
| 410 | |
| 411 | void justquit(int signo) |
| 412 | { |
| 413 | exit(0); |
| 414 | } |
| 415 | |
| 416 | |
| 417 | /* |
| 418 | * Receive a file. |
| 419 | */ |
| 420 | void recvfile(struct formats *pf) |
| 421 | { |
| 422 | struct tftphdr *dp; |
| 423 | register struct tftphdr *ap; /* ack buffer */ |
| 424 | volatile int block = 0, n, size; |
| 425 | |
| 426 | confirmed = 0; |
| 427 | signal(SIGALRM, timer); |
| 428 | dp = w_init(); |
| 429 | ap = (struct tftphdr *)ackbuf; |
| 430 | do { |
| 431 | timeout = 0; |
| 432 | ap->th_opcode = htons((u_short)ACK); |
| 433 | ap->th_block = htons((u_short)block); |
| 434 | block++; |
| 435 | (void) setjmp(timeoutbuf); |
| 436 | send_ack: |
| 437 | if (send(peer, ackbuf, 4, confirmed) != 4) { |
| 438 | syslog(LOG_ERR, "tftpd: write: %m\n"); |
| 439 | goto abort; |
| 440 | } |
| 441 | confirmed = 0; |
| 442 | write_behind(file, pf->f_convert); |
| 443 | for ( ; ; ) { |
| 444 | alarm(rexmtval); |
| 445 | n = recv(peer, dp, PKTSIZE, 0); |
| 446 | alarm(0); |
| 447 | if (n < 0) { /* really? */ |
| 448 | syslog(LOG_ERR, "tftpd: read: %m\n"); |
| 449 | goto abort; |
| 450 | } |
| 451 | dp->th_opcode = ntohs((u_short)dp->th_opcode); |
| 452 | dp->th_block = ntohs((u_short)dp->th_block); |
| 453 | if (dp->th_opcode == ERROR) |
| 454 | goto abort; |
| 455 | if (dp->th_opcode == DATA) { |
| 456 | if (dp->th_block == block) { |
| 457 | confirmed = MSG_CONFIRM; |
| 458 | break; /* normal */ |
| 459 | } |
| 460 | /* Re-synchronize with the other side */ |
| 461 | (void) synchnet(peer); |
| 462 | if (dp->th_block == (block-1)) |
| 463 | goto send_ack; /* rexmit */ |
| 464 | } |
| 465 | } |
| 466 | /* size = write(file, dp->th_data, n - 4); */ |
| 467 | size = writeit(file, &dp, n - 4, pf->f_convert); |
| 468 | if (size != (n-4)) { /* ahem */ |
| 469 | if (size < 0) nak(errno + 100); |
| 470 | else nak(ENOSPACE); |
| 471 | goto abort; |
| 472 | } |
| 473 | } while (size == SEGSIZE); |
| 474 | write_behind(file, pf->f_convert); |
| 475 | (void) fclose(file); /* close data file */ |
| 476 | |
| 477 | ap->th_opcode = htons((u_short)ACK); /* send the "final" ack */ |
| 478 | ap->th_block = htons((u_short)(block)); |
| 479 | (void) send(peer, ackbuf, 4, confirmed); |
| 480 | |
| 481 | signal(SIGALRM, justquit); /* just quit on timeout */ |
| 482 | alarm(rexmtval); |
| 483 | n = recv(peer, buf, sizeof (buf), 0); /* normally times out and quits */ |
| 484 | alarm(0); |
| 485 | if (n >= 4 && /* if read some data */ |
| 486 | dp->th_opcode == DATA && /* and got a data block */ |
| 487 | block == dp->th_block) { /* then my last ack was lost */ |
| 488 | (void) send(peer, ackbuf, 4, 0); /* resend final ack */ |
| 489 | } |
| 490 | abort: |
| 491 | return; |
| 492 | } |
| 493 | |
| 494 | struct errmsg { |
| 495 | int e_code; |
| 496 | char *e_msg; |
| 497 | } errmsgs[] = { |
| 498 | { EUNDEF, "Undefined error code" }, |
| 499 | { ENOTFOUND, "File not found" }, |
| 500 | { EACCESS, "Access violation" }, |
| 501 | { ENOSPACE, "Disk full or allocation exceeded" }, |
| 502 | { EBADOP, "Illegal TFTP operation" }, |
| 503 | { EBADID, "Unknown transfer ID" }, |
| 504 | { EEXISTS, "File already exists" }, |
| 505 | { ENOUSER, "No such user" }, |
| 506 | { -1, 0 } |
| 507 | }; |
| 508 | |
| 509 | /* |
| 510 | * Send a nak packet (error message). |
| 511 | * Error code passed in is one of the |
| 512 | * standard TFTP codes, or a UNIX errno |
| 513 | * offset by 100. |
| 514 | */ |
| 515 | void nak(int error) |
| 516 | { |
| 517 | register struct tftphdr *tp; |
| 518 | int length; |
| 519 | register struct errmsg *pe; |
| 520 | |
| 521 | tp = (struct tftphdr *)buf; |
| 522 | tp->th_opcode = htons((u_short)ERROR); |
| 523 | tp->th_code = htons((u_short)error); |
| 524 | for (pe = errmsgs; pe->e_code >= 0; pe++) |
| 525 | if (pe->e_code == error) |
| 526 | break; |
| 527 | if (pe->e_code < 0) { |
| 528 | pe->e_msg = strerror(error - 100); |
| 529 | tp->th_code = EUNDEF; /* set 'undef' errorcode */ |
| 530 | } |
| 531 | strcpy(tp->th_msg, pe->e_msg); |
| 532 | length = strlen(pe->e_msg); |
| 533 | tp->th_msg[length] = '\0'; |
| 534 | length += 5; |
| 535 | if (send(peer, buf, length, 0) != length) |
| 536 | syslog(LOG_ERR, "nak: %m\n"); |
| 537 | } |