1 /* $NetBSD: tftpd.c,v 1.11 1997/11/06 00:08:02 lukem Exp $ */ 2 3 /* 4 * Copyright (c) 1983, 1993 5 * The Regents of the University of California. All rights reserved. 6 * 7 * Redistribution and use in source and binary forms, with or without 8 * modification, are permitted provided that the following conditions 9 * are met: 10 * 1. Redistributions of source code must retain the above copyright 11 * notice, this list of conditions and the following disclaimer. 12 * 2. Redistributions in binary form must reproduce the above copyright 13 * notice, this list of conditions and the following disclaimer in the 14 * documentation and/or other materials provided with the distribution. 15 * 3. All advertising materials mentioning features or use of this software 16 * must display the following acknowledgement: 17 * This product includes software developed by the University of 18 * California, Berkeley and its contributors. 19 * 4. Neither the name of the University nor the names of its contributors 20 * may be used to endorse or promote products derived from this software 21 * without specific prior written permission. 22 * 23 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 24 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 25 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 26 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 27 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 28 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 29 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 30 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 31 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 32 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 33 * SUCH DAMAGE. 34 */ 35 36 #include <sys/cdefs.h> 37 #ifndef lint 38 __COPYRIGHT("@(#) Copyright (c) 1983, 1993\n\ 39 The Regents of the University of California. All rights reserved.\n"); 40 #if 0 41 static char sccsid[] = "@(#)tftpd.c 8.1 (Berkeley) 6/4/93"; 42 #else 43 __RCSID("$NetBSD: tftpd.c,v 1.11 1997/11/06 00:08:02 lukem Exp $"); 44 #endif 45 #endif /* not lint */ 46 47 /* 48 * Trivial file transfer protocol server. 49 * 50 * This version includes many modifications by Jim Guyton 51 * <guyton@rand-unix>. 52 */ 53 54 #include <sys/param.h> 55 #include <sys/ioctl.h> 56 #include <sys/stat.h> 57 #include <sys/socket.h> 58 59 #include <signal.h> 60 #include <fcntl.h> 61 62 #include <netinet/in.h> 63 #include <arpa/tftp.h> 64 #include <arpa/inet.h> 65 66 #include <ctype.h> 67 #include <errno.h> 68 #include <fcntl.h> 69 #include <netdb.h> 70 #include <setjmp.h> 71 #include <signal.h> 72 #include <stdio.h> 73 #include <stdlib.h> 74 #include <string.h> 75 #include <syslog.h> 76 #include <unistd.h> 77 78 #include "tftpsubs.h" 79 80 /* XXX svr4 defines UID_NOBODY and GID_NOBODY constants in <sys/param.h> */ 81 #define UID_NOBODY 32767 82 #define GID_NOBODY 32766 83 84 #define TIMEOUT 5 85 86 extern char *__progname; 87 int peer; 88 int rexmtval = TIMEOUT; 89 int maxtimeout = 5*TIMEOUT; 90 91 #define PKTSIZE SEGSIZE+4 92 char buf[PKTSIZE]; 93 char ackbuf[PKTSIZE]; 94 struct sockaddr_in from; 95 int fromlen; 96 97 /* 98 * Null-terminated directory prefix list for absolute pathname requests and 99 * search list for relative pathname requests. 100 * 101 * MAXDIRS should be at least as large as the number of arguments that 102 * inetd allows (currently 20). 103 */ 104 #define MAXDIRS 20 105 static struct dirlist { 106 char *name; 107 int len; 108 } dirs[MAXDIRS+1]; 109 static int suppress_naks; 110 static int logging; 111 static int secure; 112 static char *securedir; 113 114 struct formats; 115 116 static void tftp __P((struct tftphdr *, int)); 117 static char *errtomsg __P((int)); 118 static void nak __P((int)); 119 static char *verifyhost __P((struct sockaddr_in *)); 120 static void usage __P((void)); 121 void timer __P((int)); 122 void sendfile __P((struct formats *)); 123 void recvfile __P((struct formats *)); 124 void justquit __P((int)); 125 int validate_access __P((char **, int)); 126 int main __P((int, char **)); 127 128 struct formats { 129 char *f_mode; 130 int (*f_validate) __P((char **, int)); 131 void (*f_send) __P((struct formats *)); 132 void (*f_recv) __P((struct formats *)); 133 int f_convert; 134 } formats[] = { 135 { "netascii", validate_access, sendfile, recvfile, 1 }, 136 { "octet", validate_access, sendfile, recvfile, 0 }, 137 #ifdef notdef 138 { "mail", validate_user, sendmail, recvmail, 1 }, 139 #endif 140 { 0 } 141 }; 142 143 static void 144 usage() 145 { 146 syslog(LOG_ERR, "Usage: %s [-s] [directory ...]\n", __progname); 147 exit(1); 148 } 149 150 int 151 main(argc, argv) 152 int argc; 153 char **argv; 154 { 155 register struct tftphdr *tp; 156 register int n = 0; 157 int ch, on; 158 int fd = 0; 159 struct sockaddr_in sin; 160 161 openlog("tftpd", LOG_PID | LOG_NDELAY, LOG_DAEMON); 162 163 while ((ch = getopt(argc, argv, "lns:")) != -1) 164 switch (ch) { 165 case 'l': 166 logging = 1; 167 break; 168 169 case 'n': 170 suppress_naks = 1; 171 break; 172 173 case 's': 174 secure = 1; 175 securedir = optarg; 176 break; 177 178 default: 179 usage(); 180 break; 181 } 182 183 if (optind < argc) { 184 struct dirlist *dirp; 185 186 /* Get list of directory prefixes. Skip relative pathnames. */ 187 for (dirp = dirs; optind < argc && dirp < &dirs[MAXDIRS]; 188 optind++) { 189 if (argv[optind][0] == '/') { 190 dirp->name = argv[optind]; 191 dirp->len = strlen(dirp->name); 192 dirp++; 193 } 194 } 195 } 196 197 if (secure) { 198 if (chdir(securedir) < 0) { 199 syslog(LOG_ERR, "chdir %s: %m", securedir); 200 exit(1); 201 } 202 if (chroot(".")) { 203 syslog(LOG_ERR, "chroot: %m\n"); 204 exit(1); 205 } 206 } 207 208 if (setgid(GID_NOBODY)) { 209 syslog(LOG_ERR, "setgid: %m"); 210 exit(1); 211 } 212 213 if (setgroups(0, NULL)) { 214 syslog(LOG_ERR, "setgroups: %m"); 215 exit(1); 216 } 217 218 if (setuid(UID_NOBODY)) { 219 syslog(LOG_ERR, "setuid: %m"); 220 exit(1); 221 } 222 223 on = 1; 224 if (ioctl(fd, FIONBIO, &on) < 0) { 225 syslog(LOG_ERR, "ioctl(FIONBIO): %m\n"); 226 exit(1); 227 } 228 fromlen = sizeof (from); 229 n = recvfrom(fd, buf, sizeof (buf), 0, 230 (struct sockaddr *)&from, &fromlen); 231 if (n < 0) { 232 syslog(LOG_ERR, "recvfrom: %m\n"); 233 exit(1); 234 } 235 /* 236 * Now that we have read the message out of the UDP 237 * socket, we fork and exit. Thus, inetd will go back 238 * to listening to the tftp port, and the next request 239 * to come in will start up a new instance of tftpd. 240 * 241 * We do this so that inetd can run tftpd in "wait" mode. 242 * The problem with tftpd running in "nowait" mode is that 243 * inetd may get one or more successful "selects" on the 244 * tftp port before we do our receive, so more than one 245 * instance of tftpd may be started up. Worse, if tftpd 246 * break before doing the above "recvfrom", inetd would 247 * spawn endless instances, clogging the system. 248 */ 249 { 250 int pid; 251 int i, j; 252 253 for (i = 1; i < 20; i++) { 254 pid = fork(); 255 if (pid < 0) { 256 sleep(i); 257 /* 258 * flush out to most recently sent request. 259 * 260 * This may drop some request, but those 261 * will be resent by the clients when 262 * they timeout. The positive effect of 263 * this flush is to (try to) prevent more 264 * than one tftpd being started up to service 265 * a single request from a single client. 266 */ 267 j = sizeof from; 268 i = recvfrom(fd, buf, sizeof (buf), 0, 269 (struct sockaddr *)&from, &j); 270 if (i > 0) { 271 n = i; 272 fromlen = j; 273 } 274 } else { 275 break; 276 } 277 } 278 if (pid < 0) { 279 syslog(LOG_ERR, "fork: %m\n"); 280 exit(1); 281 } else if (pid != 0) { 282 exit(0); 283 } 284 } 285 from.sin_len = sizeof(struct sockaddr_in); 286 from.sin_family = AF_INET; 287 alarm(0); 288 close(fd); 289 close(1); 290 peer = socket(AF_INET, SOCK_DGRAM, 0); 291 if (peer < 0) { 292 syslog(LOG_ERR, "socket: %m\n"); 293 exit(1); 294 } 295 memset(&sin, 0, sizeof(sin)); 296 sin.sin_family = AF_INET; 297 if (bind(peer, (struct sockaddr *)&sin, sizeof (sin)) < 0) { 298 syslog(LOG_ERR, "bind: %m\n"); 299 exit(1); 300 } 301 if (connect(peer, (struct sockaddr *)&from, sizeof(from)) < 0) { 302 syslog(LOG_ERR, "connect: %m\n"); 303 exit(1); 304 } 305 tp = (struct tftphdr *)buf; 306 tp->th_opcode = ntohs(tp->th_opcode); 307 if (tp->th_opcode == RRQ || tp->th_opcode == WRQ) 308 tftp(tp, n); 309 exit(1); 310 } 311 312 /* 313 * Handle initial connection protocol. 314 */ 315 static void 316 tftp(tp, size) 317 struct tftphdr *tp; 318 int size; 319 { 320 register char *cp; 321 int first = 1, ecode; 322 register struct formats *pf; 323 char *filename, *mode = NULL; /* XXX gcc */ 324 325 filename = cp = tp->th_stuff; 326 again: 327 while (cp < buf + size) { 328 if (*cp == '\0') 329 break; 330 cp++; 331 } 332 if (*cp != '\0') { 333 nak(EBADOP); 334 exit(1); 335 } 336 if (first) { 337 mode = ++cp; 338 first = 0; 339 goto again; 340 } 341 for (cp = mode; *cp; cp++) 342 if (isupper(*cp)) 343 *cp = tolower(*cp); 344 for (pf = formats; pf->f_mode; pf++) 345 if (strcmp(pf->f_mode, mode) == 0) 346 break; 347 if (pf->f_mode == 0) { 348 nak(EBADOP); 349 exit(1); 350 } 351 ecode = (*pf->f_validate)(&filename, tp->th_opcode); 352 if (logging) { 353 syslog(LOG_INFO, "%s: %s request for %s: %s", 354 verifyhost(&from), 355 tp->th_opcode == WRQ ? "write" : "read", 356 filename, errtomsg(ecode)); 357 } 358 if (ecode) { 359 /* 360 * Avoid storms of naks to a RRQ broadcast for a relative 361 * bootfile pathname from a diskless Sun. 362 */ 363 if (suppress_naks && *filename != '/' && ecode == ENOTFOUND) 364 exit(0); 365 nak(ecode); 366 exit(1); 367 } 368 if (tp->th_opcode == WRQ) 369 (*pf->f_recv)(pf); 370 else 371 (*pf->f_send)(pf); 372 exit(0); 373 } 374 375 376 FILE *file; 377 378 /* 379 * Validate file access. Since we 380 * have no uid or gid, for now require 381 * file to exist and be publicly 382 * readable/writable. 383 * If we were invoked with arguments 384 * from inetd then the file must also be 385 * in one of the given directory prefixes. 386 * Note also, full path name must be 387 * given as we have no login directory. 388 */ 389 int 390 validate_access(filep, mode) 391 char **filep; 392 int mode; 393 { 394 struct stat stbuf; 395 int fd; 396 struct dirlist *dirp; 397 static char pathname[MAXPATHLEN]; 398 char *filename = *filep; 399 400 /* 401 * Prevent tricksters from getting around the directory restrictions 402 */ 403 if (strstr(filename, "/../")) 404 return (EACCESS); 405 406 if (*filename == '/') { 407 /* 408 * Allow the request if it's in one of the approved locations. 409 * Special case: check the null prefix ("/") by looking 410 * for length = 1 and relying on the arg. processing that 411 * it's a /. 412 */ 413 for (dirp = dirs; dirp->name != NULL; dirp++) { 414 if (dirp->len == 1 || 415 (!strncmp(filename, dirp->name, dirp->len) && 416 filename[dirp->len] == '/')) 417 break; 418 } 419 /* If directory list is empty, allow access to any file */ 420 if (dirp->name == NULL && dirp != dirs) 421 return (EACCESS); 422 if (stat(filename, &stbuf) < 0) 423 return (errno == ENOENT ? ENOTFOUND : EACCESS); 424 if (!S_ISREG(stbuf.st_mode)) 425 return (ENOTFOUND); 426 if (mode == RRQ) { 427 if ((stbuf.st_mode & S_IROTH) == 0) 428 return (EACCESS); 429 } else { 430 if ((stbuf.st_mode & S_IWOTH) == 0) 431 return (EACCESS); 432 } 433 } else { 434 int err; 435 436 /* 437 * Relative file name: search the approved locations for it. 438 * Don't allow write requests or ones that avoid directory 439 * restrictions. 440 */ 441 442 if (mode != RRQ || !strncmp(filename, "../", 3)) 443 return (EACCESS); 444 445 /* 446 * If the file exists in one of the directories and isn't 447 * readable, continue looking. However, change the error code 448 * to give an indication that the file exists. 449 */ 450 err = ENOTFOUND; 451 if (dirs[0].name != NULL) { 452 for (dirp = dirs; dirp->name != NULL; dirp++) { 453 snprintf(pathname, sizeof pathname, "%s/%s", 454 dirp->name, filename); 455 if (stat(pathname, &stbuf) == 0 && 456 (stbuf.st_mode & S_IFMT) == S_IFREG) { 457 if ((stbuf.st_mode & S_IROTH) != 0) 458 break; 459 err = EACCESS; 460 } 461 } 462 if (dirp->name == NULL) 463 return (err); 464 *filep = filename = pathname; 465 } else 466 *filep = filename; 467 } 468 fd = open(filename, mode == RRQ ? 0 : 1); 469 if (fd < 0) 470 return (errno + 100); 471 file = fdopen(fd, (mode == RRQ)? "r":"w"); 472 if (file == NULL) { 473 return errno+100; 474 } 475 return (0); 476 } 477 478 int timeout; 479 jmp_buf timeoutbuf; 480 481 void 482 timer(dummy) 483 int dummy; 484 { 485 486 timeout += rexmtval; 487 if (timeout >= maxtimeout) 488 exit(1); 489 longjmp(timeoutbuf, 1); 490 } 491 492 /* 493 * Send the requested file. 494 */ 495 void 496 sendfile(pf) 497 struct formats *pf; 498 { 499 struct tftphdr *dp; 500 register struct tftphdr *ap; /* ack packet */ 501 register int size, n; 502 volatile int block; 503 504 signal(SIGALRM, timer); 505 dp = r_init(); 506 ap = (struct tftphdr *)ackbuf; 507 block = 1; 508 do { 509 size = readit(file, &dp, pf->f_convert); 510 if (size < 0) { 511 nak(errno + 100); 512 goto abort; 513 } 514 dp->th_opcode = htons((u_short)DATA); 515 dp->th_block = htons((u_short)block); 516 timeout = 0; 517 (void)setjmp(timeoutbuf); 518 519 send_data: 520 if (send(peer, dp, size + 4, 0) != size + 4) { 521 syslog(LOG_ERR, "tftpd: write: %m\n"); 522 goto abort; 523 } 524 read_ahead(file, pf->f_convert); 525 for ( ; ; ) { 526 alarm(rexmtval); /* read the ack */ 527 n = recv(peer, ackbuf, sizeof (ackbuf), 0); 528 alarm(0); 529 if (n < 0) { 530 syslog(LOG_ERR, "tftpd: read: %m\n"); 531 goto abort; 532 } 533 ap->th_opcode = ntohs((u_short)ap->th_opcode); 534 ap->th_block = ntohs((u_short)ap->th_block); 535 536 if (ap->th_opcode == ERROR) 537 goto abort; 538 539 if (ap->th_opcode == ACK) { 540 if (ap->th_block == block) 541 break; 542 /* Re-synchronize with the other side */ 543 (void) synchnet(peer); 544 if (ap->th_block == (block -1)) 545 goto send_data; 546 } 547 548 } 549 block++; 550 } while (size == SEGSIZE); 551 abort: 552 (void) fclose(file); 553 } 554 555 void 556 justquit(dummy) 557 int dummy; 558 { 559 exit(0); 560 } 561 562 /* 563 * Receive a file. 564 */ 565 void 566 recvfile(pf) 567 struct formats *pf; 568 { 569 struct tftphdr *dp; 570 register struct tftphdr *ap; /* ack buffer */ 571 register int n, size; 572 volatile int block; 573 574 signal(SIGALRM, timer); 575 dp = w_init(); 576 ap = (struct tftphdr *)ackbuf; 577 block = 0; 578 do { 579 timeout = 0; 580 ap->th_opcode = htons((u_short)ACK); 581 ap->th_block = htons((u_short)block); 582 block++; 583 (void) setjmp(timeoutbuf); 584 send_ack: 585 if (send(peer, ackbuf, 4, 0) != 4) { 586 syslog(LOG_ERR, "tftpd: write: %m\n"); 587 goto abort; 588 } 589 write_behind(file, pf->f_convert); 590 for ( ; ; ) { 591 alarm(rexmtval); 592 n = recv(peer, dp, PKTSIZE, 0); 593 alarm(0); 594 if (n < 0) { /* really? */ 595 syslog(LOG_ERR, "tftpd: read: %m\n"); 596 goto abort; 597 } 598 dp->th_opcode = ntohs((u_short)dp->th_opcode); 599 dp->th_block = ntohs((u_short)dp->th_block); 600 if (dp->th_opcode == ERROR) 601 goto abort; 602 if (dp->th_opcode == DATA) { 603 if (dp->th_block == block) { 604 break; /* normal */ 605 } 606 /* Re-synchronize with the other side */ 607 (void) synchnet(peer); 608 if (dp->th_block == (block-1)) 609 goto send_ack; /* rexmit */ 610 } 611 } 612 /* size = write(file, dp->th_data, n - 4); */ 613 size = writeit(file, &dp, n - 4, pf->f_convert); 614 if (size != (n-4)) { /* ahem */ 615 if (size < 0) nak(errno + 100); 616 else nak(ENOSPACE); 617 goto abort; 618 } 619 } while (size == SEGSIZE); 620 write_behind(file, pf->f_convert); 621 (void) fclose(file); /* close data file */ 622 623 ap->th_opcode = htons((u_short)ACK); /* send the "final" ack */ 624 ap->th_block = htons((u_short)(block)); 625 (void) send(peer, ackbuf, 4, 0); 626 627 signal(SIGALRM, justquit); /* just quit on timeout */ 628 alarm(rexmtval); 629 n = recv(peer, buf, sizeof (buf), 0); /* normally times out and quits */ 630 alarm(0); 631 if (n >= 4 && /* if read some data */ 632 dp->th_opcode == DATA && /* and got a data block */ 633 block == dp->th_block) { /* then my last ack was lost */ 634 (void) send(peer, ackbuf, 4, 0); /* resend final ack */ 635 } 636 abort: 637 return; 638 } 639 640 struct errmsg { 641 int e_code; 642 char *e_msg; 643 } errmsgs[] = { 644 { EUNDEF, "Undefined error code" }, 645 { ENOTFOUND, "File not found" }, 646 { EACCESS, "Access violation" }, 647 { ENOSPACE, "Disk full or allocation exceeded" }, 648 { EBADOP, "Illegal TFTP operation" }, 649 { EBADID, "Unknown transfer ID" }, 650 { EEXISTS, "File already exists" }, 651 { ENOUSER, "No such user" }, 652 { -1, 0 } 653 }; 654 655 static char * 656 errtomsg(error) 657 int error; 658 { 659 static char buf[20]; 660 register struct errmsg *pe; 661 662 if (error == 0) 663 return "success"; 664 for (pe = errmsgs; pe->e_code >= 0; pe++) 665 if (pe->e_code == error) 666 return pe->e_msg; 667 sprintf(buf, "error %d", error); 668 return buf; 669 } 670 671 /* 672 * Send a nak packet (error message). 673 * Error code passed in is one of the 674 * standard TFTP codes, or a UNIX errno 675 * offset by 100. 676 */ 677 static void 678 nak(error) 679 int error; 680 { 681 register struct tftphdr *tp; 682 int length; 683 register struct errmsg *pe; 684 685 tp = (struct tftphdr *)buf; 686 tp->th_opcode = htons((u_short)ERROR); 687 tp->th_code = htons((u_short)error); 688 for (pe = errmsgs; pe->e_code >= 0; pe++) 689 if (pe->e_code == error) 690 break; 691 if (pe->e_code < 0) { 692 pe->e_msg = strerror(error - 100); 693 tp->th_code = EUNDEF; /* set 'undef' errorcode */ 694 } 695 strcpy(tp->th_msg, pe->e_msg); 696 length = strlen(pe->e_msg); 697 tp->th_msg[length] = '\0'; 698 length += 5; 699 if (send(peer, buf, length, 0) != length) 700 syslog(LOG_ERR, "nak: %m\n"); 701 } 702 703 static char * 704 verifyhost(fromp) 705 struct sockaddr_in *fromp; 706 { 707 struct hostent *hp; 708 709 hp = gethostbyaddr((char *)&fromp->sin_addr, sizeof (fromp->sin_addr), 710 fromp->sin_family); 711 if (hp) 712 return hp->h_name; 713 else 714 return inet_ntoa(fromp->sin_addr); 715 } 716