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